Naval Air Weapons Station China Lake

IRP Site 1 lies within the former Armitage Field Former Fuel Farm about 3 miles north of the City of Ridgecrest, in the southern portion of NAWS China Lake. The site was constructed in 1945. It is approximately 450 feet by 400 feet and is bordered by parking in the north, undeveloped desert to the east and south, and NAWS facilities to the west. The site included 13 dry wells that were approximately 10 feet deep, used to support operations at the fuel supply area. Aircraft fuels that did not meet military specifications, used engine oils, fuel tank condensate, and excess fuels were disposed of for approximately 40 years by discharging to the dry wells or by direct release to the ground surface. Releases to the dry wells and the surface may have included other liquid wastes such as solvents and degreasers. The historical disposal practices released free product to the subsurface at Armitage Field in the form of light nonaqueous phase liquids that float on the water table and dissolve into the groundwater. These disposal practices were discontinued in 1982 and the dry wells were removed in 1997.

Six underground storage tanks were present when the fuel farm was operating, including two 100,000-gallon and four 50,000-gallon underground storage tanks. Several types of fuel were stored in these tanks, including jet propellant-3, -4, and -5 and aviation gasoline 115/145 and 100/130. In addition, one 4,000-gallon tank was installed for waste oil. In 1997, the Navy closed the underground storage tanks in place and removed the associated piping, transfer stations, and filling stations.

The characteristics and contamination of groundwater and soil were investigated in a remedial investigation in 1998, and additional data were collected in support of the feasibility study in 2003 and 2005. These studies concluded that free product composed of jet propellant and total petroleum hydrocarbons was floating on the water table. The groundwater surrounding the free product was contaminated with volatile organic compounds, semivolatile organic compounds, and polycyclic aromatic hydrocarbons. Surface and subsurface soil was also found to be contaminated with volatile organic compounds and semivolatile organic compounds.

An underground storage tank corrective action plan completed in 2000 resulted in installation of a vacuum-enhanced skimming remedy. The risk assessment results in the 2007 record of decision concluded that soil and groundwater at IRP Site 1 do not pose an unacceptable risk, although the Navy established remedial action objective to remove the free product by continuing and expanding the vacuum-enhanced skimming remedy. The Navy also opted to conduct long-term monitoring and free product removal, both of which are ongoing. The current volume of total petroleum hydrocarbons the system removed is 46,505 gallons as of September 2018.

A draft remedial system evaluation report was submitted in August 2020 to address changes in the nature and extent of contamination at IRP Site 1. The remedial actions for IRP Site 1 and the other Armitage Field OU sites will continue to be evaluated in five-year reviews. The next five-year review is planned for 2022.

IRP Site 2 consisted of a concrete pad and associated drainage culverts and ditches. From 1945 to 1982, wash water and waste fuel drained from the concrete pad into an open ditch that connected to the storm water runoff system for the airfield and ultimately discharged to an open field east of the airfield. Approximately 10,000 to 20,000 gallons of wastewater containing chlorinated solvents (degreasers), industrial detergents, hydraulic fluid, lubricating oil, antifreeze, and jet fuels was discharged into the ditch on a daily basis when the site was in operation.

The characteristics and contamination of the groundwater at IRP Site 2 were investigated in a remedial investigation in 1998, as well in as the basewide hydrogeologic characterization and the groundwater monitoring program under the feasibility study for Armitage Field in 2003. These investigations indicate that groundwater contamination at IRP Site 2 primarily consists of a plume covering 9.9 acres of trichloroethene and tetrachloroethene, along with a few detections of compounds that result from degradation of these volatile organic compounds. The remedial investigation also indicated that surface and subsurface soil at IRP Site 2 contained low levels of volatile organic compounds and semivolatile organic compounds.

The risk assessment in the 2007 record of decision concluded that soil does not pose an unacceptable risk and that further action is not warranted, although a remedial action objective for groundwater was established at the Armitage Field OU to prevent exposure at IRP Site 2. Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022.

IRP Site 3 consists of a treatment plant, a sewage tank, and an unlined leach pond. The treatment plant and sewage tank are located south of Aircraft Range Access Road, and the leach pond is located north of the road. From 1950 to 1981, an estimated 17,000 gallons per day of sanitary and industrial waste was collected in the treatment plant, then discharged to the sewage tank for settlement and finally to the unlined leach pond through a 10-inch-diameter vitrified clay pipe. Most of the waste the system received was domestic sewage, except for about 500 gallons per day of wastewater that contained low concentrations of solvents, detergents, oil, and grease discharged to the sanitary sewer.

A site inspection was completed in 2002. Volatile organic compounds, semivolatile organic compounds, and metals were detected in groundwater but did not exceed maximum contaminant levels. The risk assessment in the 2007 record of decision concluded that soil does not pose an unacceptable risk and that further action is not warranted, although a remedial action objective for groundwater was established at the Armitage Field OU to prevent exposure at IRP Site 3. Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022. An additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 44 is located about 2,500 feet east of the aircraft runways at Armitage Field. From 1945 to 1988, the old firefighting training area pad in the southwestern portion of the site was used as a practice facility for fighting petroleum fires. Unburned gasoline, jet propellent 5, and water would evaporate or flow off the pad and percolate into the surrounding soil. A new pad was installed in 1988 that included containment berms and an oil-water separator to eliminate releases to the soil, and the old IRP Site 44 pad was decommissioned. The new pad is regulated under the Regional Water Quality Control Board’s compliance program for waste discharges to land, which includes a set of waste discharge requirements and groundwater monitoring.

IRP Site 44 also encompasses Point of Interest 197, call the “Water Road Fuel Dump” located 750 feet east of the old firefighting training area. Based on site records and aerial photographs, fuels may have been released at Point of Interest 197 in the 1960s and 1970s.

The characteristics and contamination of groundwater and soil at IRP Site 44 and Point of Interest 197 were investigated in a phase I and phase II remedial investigation completed in 1998 and 2002, as well as the basewide hydrogeologic characterization and groundwater monitoring program as part of the feasibility study in 2003. It was concluded that IRP Site 44 was contaminated with plumes of free product and dissolved-phase total petroleum hydrocarbons that appear to be associated with Point of Interest 197. The remedial investigation also indicated that surface soil was contaminated with semivolatile organic compounds and subsurface soil with total petroleum hydrocarbons.

The risk assessment results in the 2007 record of decision concluded that soil and groundwater at IRP Site 44 and Point of Interest 197 do not pose an unacceptable risk, although the Navy established a remedial action objective for groundwater to remove the free product in the area. Additionally, benzene was identified as a contaminant for groundwater at IRP Site 44. Optimization of the recovery system is ongoing. A draft remedial system evaluation report was submitted in August 2020 to address changes in the nature and extent of contamination at IRP Site 44.

Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022. An additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 45 is located on the northeastern side of the aircraft runways at Armitage Field. IRP Site 45 services ground support equipment and vehicles. Typical activities included routine vehicle maintenance, such as changing oil, brake fluid, and antifreeze, and adding hydraulic oil. From 1945 to 1981, water and other runoff were directed into a tributary of an unlined shallow ditch, with another unlined ditch draining from the aircraft cleaning area. Past activities at the nearby Naval Air Facility Gas Station, south and southwest of the site, may also have contributed to groundwater contamination in the area.

The characteristics and contamination of groundwater and soil at IRP Site 45 were investigated in a phase I and phase II remedial investigation completed in 1996 and 2002, as well as the basewide hydrogeologic characterization and groundwater monitoring program as part of the feasibility study in 2003. These investigations concluded that chlorinated volatile organic compounds are present in groundwater beneath the site. The remedial investigation also indicated that surface soil was contaminated with polycyclic aromatic hydrocarbons at the site.

The risk assessment in the 2007 record of decision concluded that remedial action for the polycyclic aromatic hydrocarbons in surface soil was needed. At the Armitage Field OU, a remedial action objective for groundwater was established to prevent exposure at IRP Site 45.

In 2013, the polycyclic aromatic hydrocarbons contamination was removed from surface soil through remedial action. Because no contaminants of concern remain in soil, no further action is required for soil. Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022.

IRP Site 50 consists of a trench that measures 20 feet wide by 300 feet long adjacent to IRP Site 3. From the mid-1960s to the mid-1970s, waste engine oil from propeller-driven aircrafts was disposed of in this trench. The used oil may have contained heavy metals and polycyclic aromatic hydrocarbons. Liquid and dried waste oil were observed on the surface of the trench in July 1999 during a site inspection.

The Navy completed a removal action for soil at IRP Site 50 in 1999 and a site inspection in 2002. The soils subject to the removal action at IRP Site 50 were contaminated with total petroleum hydrocarbons and polycyclic aromatic hydrocarbons. An extended site inspection completed in 2002 did not find any additional soil contamination but did detect volatile organic compounds, semivolatile organic compounds, and metals in groundwater associated with IRP Site 50. The volatile organic and semivolatile organic compounds detected did not exceed maximum concentration limits, and the metals appeared to be a result of the sampling method used during the investigation.

The 2007 record of decision for IRP Site 50 was published in required no further action for soil. Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022.

IRP Site 58 is currently used as an office and training room. The site also includes several storage sheds, oil drip pans, two portable waste oil containers (bowsers), and a hazardous material storage locker. The site is 160 feet by 120 feet and is located near the runways, northwest of the hangar area. The storage area was used to store engine oil (used and unused), aviation fuel samples, hydraulic fluid, flight line cleaners, and solvents. The sites storage area was also used as a maintenance area for the VX-5 squadron starting in approximately 1956. The area is covered primarily with asphalt and, to a lesser extent, concrete. IRP Site 58 was repaved in 2006.

IRP Site 58 was subject to a removal site evaluation completed in 2000. The investigation concluded there were no chemicals of concern or chemicals of ecological concern at the site for soil or groundwater. The 2007 record of decision further concluded that soil does not pose an unacceptable risk and that further action is not warranted, although a remedial action objective for groundwater was established at the Armitage Field OU to prevent exposure at IRP Site 58. No further action is required for soil. Monitored natural attenuation and institutional controls are in place and functioning as part of the Armitage Field OU groundwater remedy. The fourth five-year review is planned for 2022.

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IRP Site 15 consists of an abandoned on-site wastewater treatment and disposal system that was used to dispose of wastewater from buildings and test sites at the R Range complex. From 1950 until 1984, the R Range leach field at IRP Site 15 received most of the individual and sanitary wastewater from facilities within the R Range complex. Activities at R Range facilities that generated wastewater included cooling tower blowdown, photographic laboratory operations, and operations at various fuze and explosives research laboratories and associated machining shops. In addition, rinse water from activities at the static firing-rocket test stands at IRP Site 56 in the R Range complex was conveyed to the R Range leach field. In 1984, the R Range leach field and the tile leach field were abandoned, and all sanitary and industrial waste was routed to the sanitary sewer parallel to Pole Line Road.

During the 2002 remedial investigation, chlorinated solvents were identified as chemicals of concern in groundwater; no chemicals of concern were identified for soil. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 15.

The anticipated completion date for the data gaps investigation is 2021, followed by completion of the feasibility study addendum in 2022 and the record of decision in 2023. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 51 is located on the eastern site of Pole Line Road across the street from IRP Sites 15 and 55. The site previously included an old and newer vehicle maintenance ramp, debris piles, disposal trenches, a former inert materials storage building, a bomb disposal building, and a hazardous materials storage pad. The bomb disposal building, and an inert storage building were constructed in 1945. The hazardous materials storage pad was built between 1949 and 1954. Drums of sodium hydroxide, acetone, and toluene were reportedly stored on the pad. Explosive ordnance disposal personnel contractors used the bomb disposal area from the 1960s through the 1970s for cleaning, disassembling, and deactivating missile, rocket, and torpedo warheads and other explosives. Wastewater drained from the bomb disposal and inert storage buildings discharged to an open ditch and was diverted through a culvert to the North Ditch to IRP Site 15. Waste lines were later connected to the sanitary sewer that was installed along Pole Line Road in 1984.

Risk evaluations from a 2000 removal site evaluation, identified no chemicals of concern for soil or groundwater. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 51.

The anticipated completion date for the data gaps investigation is 2021, followed by completion of the feasibility study addendum in 2022 and the record of decision in 2023.

IRP Site 55 previously contained a 500-gallon solvent rinse tank and a tile leach field in the larger footprint of IRP Site 15. The solvent rinse tank, removed in 1991, was a 500-gallon underground storage tank. IRP Site 55 is entirely within the area of IRP Site 15 and includes a tile leach field that appears to have received effluent associated with solvent rinsing and cleaning. This tile leach field, used from approximately 1952 until 1984, received wastewater from other R Range facilities as well. No records were located to indicate the nature of the industrial wastes discharged to the tank and leach field; however, the waste stream may have included dilute concentrations of solvents.

During the 2002 remedial investigation, chlorinated solvents were identified as chemicals of concern in groundwater; no chemicals of concern or chemicals of environmental concern were identified for soil. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 55.

The anticipated completion date for the data gaps investigation is 2021, followed by completion of the feasibility study addendum in 2022 and the record of decision in 2023.

IRP Site 56 is located in the main complex of the Area R buildings. The site consists of three test stands used to test liquid-propellant rockets. The primary reason for investigating this site was the use and spillage of mercury near one of the test stands. Acids, solvents, and bleaches were reportedly also used at the facilities.

Risk assessments from a 2000 removal site evaluation as well as the subsequent feasibility study at the Area R OU identified no chemicals of concern for soil or groundwater. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 56.

The anticipated completion date for the data gaps investigation is 2021, followed by completion of the feasibility study addendum in 2022 and the record of decision in 2023. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 57 is a pit located just south of Water Road and west of Pole Line Road. The site was constructed in 1966, when it was excavated for fill material used in construction of the Warhead Research Laboratory. The pit was later used to dispose of construction debris, including asphalt, concrete, scrap wood, and metal. Investigations have confirmed that only inert wastes were disposed of at the site.

No chemicals of concern were identified for soil or groundwater during the 1997 preliminary assessment. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 57.

The anticipated completion date for the data gaps investigation is 2021, followed by completion of the feasibility study addendum in 2022 and the record of decision in 2023.

IRP Site 64 includes an original leach field, a newer tile leach field and overlying evaporation pond, and an acid waste line. From 1953 until 1969, a single 1,000-gallon septic tank and the original leach field received sanitary and industrial wastes from the Human Factors Laboratory as well as wastewater. In 1969, the septic tank and original leach field associated with the laboratory were abandoned, and a new tile leach field and acid waste line were constructed. A shallow evaporation pond overlies the new tile leach field. In 1984, the facilities served by the evaporation pond and leach field were connected to the main wastewater treatment system at NAWS China Lake. The evaporation pond and leach field were abandoned in place and are currently inactive.

During the 2002 remedial investigation, dioxins and furans were identified as chemicals of concern for soil; no chemicals of concern were identified for groundwater. Groundwater monitoring will continue at the Area R OU and a data gaps investigation will be completed that may include IRP Site 64.

The anticipated completion date for the data gaps investigation is 2021. The feasibility study addendum is anticipated to be completed in 2022 and the record of decision in 2023.

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IRP Site 8 consists of a series of natural and man-made drainages that traverse the hillside of the Propulsion Laboratory Operable Unit. From 1946 to 1981, wastewater from laboratory buildings was discharged through solid separation systems to the IRP Site 8 drainages. The wastewater reportedly contained TNT, plastic bonded explosives, and pressed projectile explosives. Approximately 14,000 gallons of wastewater were discharged to the IRP Site 8 drainage channels each day. In 1981, the drainage channels were replaced with the 21 clay-lined evaporation ponds that constitute IRP Site 49.

Explosives were identified as chemicals of concern for soil in the 2006 remedial investigation report, and tetrachloroethylene and chloroform were identified as chemicals of concern for groundwater at IRP Site 8. A removal action that included IRP Site 8 was completed in 2016. Approximately 7,025 cubic yards of contaminated soil (primarily explosive residues) was removed from six Propulsion Laboratory Operable Unit sites and held at IRP Site 6. Confirmation sampling data from the removal action showed some results above removal action goals.

A work plan for a data gaps investigation, expected to finish in 2021, is being prepared to further assess contamination at the site. In addition, a natural degradation study will be completed in 2020 that will evaluate the contribution of natural abiotic or biotic processes in reducing volatile organic compounds and explosives concentrations in groundwater. Groundwater monitoring at the site is ongoing. The record of decision is anticipated to be available before the end of 2023.

IRP Site 11 consists of a single evaporation pond that received wastewater discharge from a building used to manufacture solid and aerosol propellants and explosives. The unlined evaporation pond was replaced by a clay-lined pond in 1981. This pond was subsequently removed as part of the overall IRP Site 49 removal action.

One type of explosive was identified as a chemical of concern for soil during the 2006 remedial investigation. Groundwater is not present within the unconsolidated soils at IRP Site 11 and no chemicals of environmental concern were identified for the site. A removal action that included IRP Site 8 was completed in 2016. Approximately 7,025 cubic yards of contaminated soil inclusive primarily of explosive residues was removed from six Propulsion Laboratory Operable Unit sites and held at IRP Site 6. Confirmation sampling data from the removal action showed some results above removal action goals.

A work plan for a data gaps investigation, expected to finish in 2021, is being prepared to further assess contamination at the site. In addition, a natural degradation study will be completed in 2020. The record of decision is anticipated to be available before the end of 2023.

IRP Site 46 consists of a drainage that leads away from a currently active fenced area formerly used for cleaning rocket motor casings, a solvent storage shed, and a tank shed. The cleaning facility consisted of two solvent tanks, a concrete drying pad, a solvent storage shed, and two sumps. The drainage that is IRP Site 46 leads east away from the Dunkit facility and historically received discharge of solvent rinse water directly to the ground surface. Rocket motor casings were cleaned at the Dunkit facility starting in 1971. In 1989, the Navy began collecting spent solvents and rinse water in a tank for disposal as hazardous waste.

Chromium and cadmium were identified as chemicals of concern for soil in the 2006 remedial investigation and trichloroethylene was identified as a chemical of concern for groundwater at IRP Site 46. A removal action that included IRP Site 8 was completed in 2016. Approximately 7,025 cubic yards of contaminated soil (primarily explosive residues) was removed from six Propulsion Laboratory Operable Unit sites and held at IRP Site 6. Confirmation sampling data from the removal action showed some results above removal action goals.

A work plan for a data gaps investigation, expected to finish in 2021, is being prepared to further assess contamination at the site. In addition, a natural degradation study is being conducted to evaluate the contribution of natural abiotic or biotic processes in reducing contaminant concentrations in groundwater. Groundwater monitoring at the site is ongoing. The record of decision is anticipated to be available before the end of 2023.

IRP Site 49 consists of numerous surface impoundments spread over the western portion of Salt Wells Valley. From 1946 to 1981, industrial wastewater from laboratories was discharged to open drainage channels that are now designated as IRP Site 8. The open channels were replaced in 1981 with 22 clay-lined ponds designed to collect discharged wastewater. These ponds constitute IRP Site 49. No significant releases were ever documented at the site; however, monthly inspections of the leak detection system in the mid- 1980s revealed that many of the ponds were beginning to leak through the clay liners. As a result, seven of the ponds were reconstructed with a double-layered synthetic liner.

The explosives RDX and TNT were identified as chemicals of concern for soil in the 2006 remedial investigation report, and tetrachloroethylene and chloroform were identified as chemicals of concern for groundwater at IRP Site 49. A removal action that included IRP Site 8 was completed in 2016. Approximately 7,025 cubic yards of contaminated soil (primarily explosive residues) was removed from six Propulsion Laboratory Operable Unit sites and held at IRP Site 6. Confirmation sampling data from the removal action showed some results above removal action goals.

A work plan for a data gaps investigation, expected to finish in 2021, is being prepared to further assess contamination at the site. In addition, a natural degradation study will be completed in 2020. Groundwater monitoring at the site is ongoing. The record of decision is anticipated to be available before the end of 2023.

AOC 79 is located in the Salt Wells Valley, adjacent to a laboratory. AOC 79 consists of a discharge pit adjacent to Buildings 10633 and 10630. A buried metal discharge pipe enters the pit from the south. Historical activities that may have discharged wastewater to this pit are unknown; however, the laboratory was used for mixing and testing explosives in the past.

Analytes that were detected in soil during the remedial investigation include explosive compounds, perchlorate, zinc, and chromium. A removal action that included IRP Site 8 was completed in 2016. Approximately 7,025 cubic yards of contaminated soil (primarily explosive residues) was removed from six Propulsion Laboratory Operable Unit sites and held at IRP Site 6. Confirmation sampling data from the removal action showed some results above removal action goals.

A work plan for a data gaps investigation, expected to finish in 2021, is being prepared to further assess contamination at the site. In addition, a natural degradation study will be completed in 2020. Groundwater monitoring at the site is ongoing. The record of decision is anticipated to be available before the end of 2023.

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IRP Site 7 is located on the northern side of the Michelson Laboratory building. The site consists of two unlined ditches that received liquid wastewater from Michelson Laboratory from 1947 to 1980 via an industrial waste collection system. The estimated maximum flow of the west ditch was 62,000 gallons per day of wastewater containing dilute concentrations of acids, bases, heavy metals, cyanides, photo-processing chemicals, and solvents. The estimated maximum flow of the eastern ditch was 9,400 gallons per day of cooling water containing acids, algaecides, and possibly perchlorate. The total volume of wastewater disposed of into the ditches is unknown.

Metals, pesticides, and polychlorinated biphenyls were identified as chemicals of concern for soil in the remedial investigation report, and volatile organic compounds were identified as chemicals of concern for groundwater at IRP Site 7. The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010.

A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 13 consists of two former unlined trenches that received waste oils from 1965 to 1980. Waste oils possibly included motor oils, solvents, and grease from grease traps at NAWS China Lake cafeterias. An estimated 10,000 gallons of waste were disposed of into the trenches during the 15 years that the site was in operation. The trenches were filled in and operations ceased at the site in 1980.

After initial investigations, including a phase I remedial investigation, the trenches were subsequently excavated and backfilled with clean soils during a removal action in 1999. Confirmation soil sampling confirmed that the removal objectives had been met. Evaluation of the site continued after the removal action was completed. A soil removal action was conducted at IRP Site 13 in 2000 to remove waste oil sludge and associated soil.

Polychlorinated biphenyls were identified as chemicals of environmental concern for soil, and vinyl chloride was identified as a contaminant of concern for groundwater at IRP Site 13 in the revised draft feasibility study. The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010.

A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023.

IRP Site 33 consists of four dry wells that received battery acid waste from laboratory auxiliary power rooms from the late 1950s to the 1970s. Research for the initial assessment study did not indicate use of the wells for any other purpose or chemicals. As part of a site reconnaissance in September 1996, the historical plumbing plan for the Michelson Laboratory foundation was reviewed. According to the plans, three darkroom drains, along with auxiliary power room sumps, are connected to individual dry wells that were referenced in the initial study. A fourth dry well shows no connections.

No chemicals of concern or chemicals of environmental concern were identified for soil or groundwater by risk assessments during the remedial investigation. The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010.

A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023.

IRP Site 47 includes the former industrial sewer system, associated lateral piping, leach lines and sumps, and two former industrial wastewater ponds. The public works compound typically contributed dilute mixtures of oil and grease, heavy metals, vehicle wash water, and battery acids to the industrial sewer system. The Michelson Laboratory complex effluent included dilute mixtures of acids, bases, heavy metals, solvents, plating solutions, photographic and circuit-board chemicals, and cooling waters.

Three metals, two pesticides, and polychlorinated biphenyls were identified as chemicals of concern or chemicals of environmental concern for soil, and three volatile organic compounds were identified as chemicals of concern in the 2010 remedial investigation report for groundwater at IRP Site 47.

A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 68 was used from 1979 to 1990 to store transformers from throughout NAWS China Lake and nearby complexes. The Public Works Transformer Storage Pit typically held 15 to 20 transformers. Excess transformers were stored north of the pit in the area now known as the New Transformer Storage Yard. Until 1984, transformers were set directly on the ground in the unlined Public Works Transformer Storage Pit. Navy-constructed containment devices (drip pans) were used from 1984 to 1988. Commercial drip pans were used starting in 1988. In 1990, the Public Works Transformer Storage Pit was excavated and partially backfilled. A soil removal action was conducted at IRP Site 68 in 2012. The action removed polychlorinated biphenyl-contaminated soil.

A specific polychlorinated biphenyl was identified as a chemical of concern in the contamination assessment and revised draft feasibility study reports; no chemicals of concern were identified for groundwater.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023.

IRP Site 69 is located on the eastern side of the Public Works compound and contains the Public Works Vehicle Paint Shop, which is currently active. The drainage basin collects surface runoff from the paint shop. The paint shop was built in 1951 and is operated by the Public Works Department. Historical or current activities at the paint shop include painting Navy vehicles, rockets, missile launchers, missiles, and other large equipment. Painting reportedly involved the use of lead- and titanium-based paints, phosphorescent paints, thinners, and solvents. Disposal of materials at the paint shop may have contaminated nearby surface soils and the drainage catch basin across the street. The Hazardous Waste Site Transfer Facility at NAWS China Lake reportedly began to collect waste solvents, thinners, and paint from the facility in 1985. These materials are currently disposed of by an approved waste disposal company. The drainage catch basin reportedly was used for waste disposal prior to 1977. A 55-gallon drum was kept at the paint shop to store waste thinners and unused paint. This drum was reportedly routinely dumped in the catch basin.

No chemicals of concern or chemicals of environmental concern were identified for soil or groundwater by risk assessments during the remedial investigation.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021, followed by the record of decision in 2022 or 2023.

IRP Site 70 is located in the western portion of the Public Works compound and consists of a concrete pad and dry well constructed in 1968. The pad was used to steam-clean tanker trucks and other large equipment; fluids generated during the steam cleaning drained to the dry well. The dry well was used for approximately 7 years, from 1968 until at least 1975. The dry well is no longer active, and the area is currently being used as a parking lot and cable storage area.

Volatile organic compounds and semivolatile organic compounds were identified as chemicals of concern for soil in the remedial investigation report, and volatile organic compounds and the semivolatile organic compound naphthalene were identified as chemicals of concern for groundwater at IRP Site 70. No chemicals of environmental concern were identified by the remedial investigation ecological risk assessments. A pilot study was conducted to evaluate the effectiveness of soil vapor extraction at IRP Site 70 from 2005 to 2006. Accelerated site characterization programs were implemented in 2004 and 2007 to 2008 at IRP Site 70 to further delineate free product and related fuel contamination in soil and groundwater.

Free product has periodically been removed from IRP Site 70 monitoring wells since 2006. Semi-annual groundwater monitoring has also been performed at eight IRP Site 70 wells in 2012 and 2013. These monitoring events have demonstrated that the light nonaqueous phase liquid and dissolved total petroleum hydrocarbon plumes at the site are stable or declining and have further found aerobic conditions in groundwater that are conducive to natural degradation of hydrocarbons.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021. The record of decision is anticipated in 2022 or 2023.

IRP Site 71 is located in the northwestern quarter of the Public Works compound and consists of a storage area near the repair shop where oils, antifreeze, and solvents were reportedly stored in drums before the early 1980s. Currently, the site is paved and used as a parking area for large vehicles.

Volatile organic compounds and semivolatile organic compounds in soil and volatile organic compounds and one semivolatile organic compound were identified as chemicals of concern for groundwater at IRP Site 70. No chemicals of environmental concern were identified by the remedial investigation ecological risk assessments.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021. The record of decision is anticipated in 2022 or 2023.

IRP Site 72 includes the Railroad Engine House and the areas near the facility that were associated with service of the trains until approximately 1980. It was used as a service facility for train engines, where routine maintenance involved draining fluids such as used oil through a floor drain to a dry well. It was also reportedly used to store transformers. File searches conducted during the 1996 preliminary assessment showed that NAWS China Lake owned two diesel electric train engines in the past. During initial site visits, the oil pit was observed to be heavily stained, and other oil spills were observed.

The pesticide Aldrin was identified as a chemical of concern for soil in the remedial investigation report. No chemicals of concern have been identified for groundwater, and no chemicals of environmental concern were identified by the ecological risk assessments.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021. The record of decision is anticipated in 2022 or 2023.

AOC 234 is located in the southern portion of the main base adjacent to Michelson Laboratory. The site was a vehicle maintenance and service station. Archived photographs show the maintenance building and service pit in operation in the 1940s during construction of Michelson Laboratory. The cement slab for the maintenance building is still in place. A service station was previously located at AOC 234; however, there is no evidence of a gas pump island or an underground storage tank.

Total petroleum hydrocarbons and arsenic were identified as chemicals of potential concern for soil in the preliminary assessment report, and volatile organic compounds and metals were identified as chemicals of potential concern for groundwater at AOC 234.

The remedial investigation for the Michelson Laboratory/Public Works Operable Unit was finalized in 2010. A draft feasibility study was prepared in 2008, with a revised draft delivered for agency review in May 2014. A draft final feasibility study was prepared in 2018 but was not accepted based on what was considered an insufficient amount of data. A data gaps investigation is anticipated to be completed in 2021. The record of decision is anticipated in 2022 or 2023.

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IRP Site 9 is located in Salt Wells Valley, east of the Propulsion Laboratory Operable Unit. The site encompasses a 10-acre area where reports state that an estimated 300 cubic yards of waste asbestos-containing material generated at NAWS China Lake was disposed of in three slit trenches from 1979 to 1981. Some of the asbestos-containing material was reportedly discarded in plastic bags, although much of it was reported to have been loose when it was buried.

Arsenic, chromium, and lead were identified as chemicals of concern for soil in the 2004 remedial investigation report, and hexavalent chromium and heptachlor epoxide were identified as chemicals of concern for groundwater at IRP Site 9/10. Additional investigation was completed as part of the 2018 remedial investigation addendum at IRP Site 9 and 10 to accomplish the following: confirm that there were no releases of contaminants to groundwater, provide a more current groundwater dataset, update the previous human health risk assessment, and update previous environmental risk assessments.

Based on the results of the remedial investigation addendum, one additional round of groundwater monitoring was recommended to further evaluate whether concentrations of organic and inorganic compounds in IRP Site 9/10 groundwater are remaining stable or are decreasing. An evaluation of the existing soil cover at both sites was also recommended. Finally, an evaluation and potential removal action was recommended for any surface bulk waste debris at IRP Site 9/10 that is found to contain asbestos.

Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend future actions.

IRP Site 10 is located in Salt Wells Valley, east of the Propulsion Laboratory Operable Unit. The site consists of 10 trenches adjacent to IRP Site 9. From 1960 to 1980, these trenches reportedly received solid wastes as well as some liquid waste from nearby propulsion laboratories.

Arsenic, chromium, and lead were identified as chemicals of concern for soil, and hexavalent chromium and heptachlor epoxide were identified as chemicals of concern for groundwater at IRP Site 9/10. Additional investigation was completed as part of the 2018 remedial investigation addendum at IRP Site 9 and 10 to confirm that there were no releases of contaminants to groundwater, provide a more current groundwater set, and update the previous human health risk assessment and environmental risk assessments.

Based on the results of the remedial investigation addendum, one additional round of groundwater monitoring was recommended to further evaluate whether concentrations of organic and inorganic compounds in IRP Site 9/10 groundwater are remaining stable or are decreasing. An evaluation of the existing soil cover at both sites was also recommended. Finally, an evaluation and potential removal action was recommended for any surface bulk waste debris at IRP Site 9/10 that is found to contain asbestos.

Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend future actions.

IRP Site 19 is located in the northwestern portion of the China Lake Complex in the Indian Wells Valley. The site was an open disposal site from 1944 to 1983 and reportedly received approximately 3,000 cubic yards of solid waste before it was subsequently covered by soil. No hazardous waste disposal was documented at the site.

No chemicals of potential concern were identified in soil or groundwater during the 2006 preliminary assessment and 2012 site inspection. A work plan is being generated for a data gaps study.

Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend future investigations and actions under CERCLA.

IRP Site 20 is located in the Division 36 area of the central China Lake Complex in the Indian Wells Valley. The site was used from 1960 to 1979 for disposal of range and inert ordnance wastes, which were reportedly buried in two trenches. The total volume was estimated to be 600 cubic yards. The locations of the two trenches were never verified during subsequent site visits.

No chemicals of potential concern were identified in soil during the 2006 preliminary assessment and 2012 site inspection. Groundwater at the site was too deep to be evaluated. A geophysical investigation was completed at the site, and the results indicated that no further delineation was required.

IRP Site 20 was removed from the Landfill Operable Unit plans for further investigation based on the results of the geophysical investigation. The Navy will be pursuing no further action based on previous investigations indicating no burial of waste at the site.

IRP Site 21 is located in the CT-4 area in Salt Wells Valley at the end of the CT access road. The site consists of a trench that received approximately 2,000 cubic yards of waste between 1956 and 1979. The disposal area was closed in 1979, all waste was removed, and the area was re-graded. The NAWS China Lake Explosive Ordnance Disposal detachment inspected the material as it was removed. Reports of hazardous material disposal could not be corroborated. During site visits in 1996 and 1999, IRP Site 21 appeared free of debris, and no evidence of hazardous materials was found.

No chemicals of potential concern were identified in soil by the 2002 preliminary assessment. While groundwater was not evaluated, previous data do not confirm that it is even present below the site.

Previous investigations concluded that no further action was warranted at the site because all disposed waste was removed in 1979. No further action was recommended for IRP Site 21 in the 2015 basis for no further action determination report and agency concurrence was received in February 2015. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 22 is located in the southeastern portion of the China Lake Complex in the Indian Wells Valley. The site was a landfill that received most of the household wastes generated by on-base housing, and small amounts of industrial material, from 1944 to 1965.

No chemicals of concern were identified for soil or groundwater by risk assessments included in the 1996 and 2000 remedial investigations. A data gaps investigation concluded that reduced frequency or reduced monitoring may be pursued based on the lack of site impacts over the last 50 years. Before any monitoring occurs, replacement of dry wells may be necessary because of declining groundwater levels.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend future, additional CERCLA actions.

IRP Site 23 is located in the south-central portion of the China Lake Complex in the Indian Wells Valley, along North Knox Road, south of the Aircraft Survivability area. The site consists of three trenches that received range waste from 1950 until 1981. Unopened 1- and 5-gallon cans of chlordane were reportedly received at this site. Navy personnel interviewed during a 1996 site reconnaissance confirmed that some of the chlordane in the 1- and 5-gallon containers had been placed at IRP Site 23.

Based on the 2006 preliminary assessment and 2012 site inspection report, arsenic, chromium, and polychlorinated biphenyls were identified as chemicals of potential concern for soil, and trichloroethylene was identified as a chemical of potential concern for groundwater. A 2018 data gaps investigation confirmed chlorinated solvent concentrations at the site, indicating a low-level release to groundwater that may require further evaluation and delineation.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 24 is located in the K-2 Range in the northeastern portion of the China Lake Complex, east of the Aircraft Survivability area within the Indian Wells Valley. The site consists of two trenches excavated in a natural drainage that received range waste from 1950 to 1981. Previous reports indicated that at least several 1- and 5-gallon cans of chlordane were emplaced at this site and others in the 1970s. The site received an estimated 500 to 1,000 cubic yards of waste. No chemicals of potential concern were identified for soil by the 2006 preliminary assessment and 2012 site inspection. Groundwater was not evaluated since it is not likely present at the site based on the shallow bedrock nearby. A geophysical investigation at the site found no features that warrant further delineation.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend future, additional CERCLA actions.

IRP Site 25 is located in the G-2 Range in the southern portion of the China Lake Complex, east of G-2 Tower Road within the Indian Wells Valley. The site consists of three trenches that received inert range waste from 1944 to 1958 and is also referred to as AOC 241. An estimated 600 cubic yards of waste were disposed of at the site. No chemicals of potential concern were identified for soil or groundwater by the 2006 preliminary assessment and 2012 site inspection. An ecological risk screening has not yet been completed. A geophysical investigation at the site found no features that warrant further delineation.

The Navy is conducting more work in the area as part of the larger AOC 241. The site is also being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 26 is located in the southern portion of the China Lake Complex south of George Road within the Indian Wells Valley. The site, also known as Point of Interest 110, consists of two trenches that received an estimated 500 cubic yards of inert range waste from 1950 to 1979. No chemicals of potential concern were identified for soil or groundwater by the 2006 preliminary assessment and 2012 site inspection. An ecological risk screening has not yet been performed.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 27 is located northwest of Armitage Field in the Indian Wells Valley. The site is an inactive landfill that received an estimated 2,000 cubic yards of waste materials in five slit trenches between 1945 and 1978. No chemicals of potential concern were identified for groundwater by the site inspection, and soil was assessed not to be of concern because the wastes are buried. Volatile organic compounds and helium were identified as chemicals of potential concern in soil vapor at the site.

The Navy is conducting a site inspection for IRP Site 27, which will summarize the results of surface soil and groundwater sampling and analysis completed in April 2015 and soil gas and groundwater sampling and analysis completed in July 2017. Additional data collection was recommended based on the results of the site inspection.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 29 is situated within the Indian Wells Valley in the northwestern portion of the China Lake Complex. The site is a disposal area where ordnance and other materials were buried from the early 1950s through the late 1970s. Initial investigations documented a possible one-time disposal of chlordane and lead-based paint, although this was not confirmed by subsequent investigations. A 2018 focused feasibility study identified cadmium, lead, and radionuclides as chemicals of concern for soil but identified no chemicals of concern for groundwater.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future, CERCLA actions.

IRP Site 30 is located within the Indian Wells Valley in the southern-central portion of the China Lake Complex. The site is an ordnance landfill thought to have received inert and live ordnance waste from 1950 to 1979. The site contains an area of noticeable disturbance, which is surrounded by signs indicating burial of ordnance. The volume or type of ordnance could not be identified. No chemicals of potential concern were identified for soil or groundwater at IRP Site 30 by the 2006 preliminary assessment and 2012 site inspection.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 34 is a disposal area located east of North Lauritsen Road in the Indian Wells Valley. The site is a relatively large landfill that received solid and liquid wastes from 1944 to 1955. An estimated 2,000 cubic yards of material were disposed of at the site.

Arsenic and manganese were identified as chemicals of potential concern for soil; hexavalent chromium, metals, volatile organic compounds, and one semivolatile organic compound were identified as chemicals of potential concern for groundwater; and chloroform and trichloroethylene were identified as chemicals of potential concern for soil vapor. A geophysical survey was conducted in December 2018 with the goal of delineating the disposal trenches at the site. The results of the survey conclusively identified a significant number of disposal trenches either fully or partially covered.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 37 is located south and east of the golf course and south of Knox Road in the Indian Wells Valley. The site was used from 1945 to 1964 for disposal of general refuse, construction waste, and demolition debris. The 2004 remedial investigation confirmed that waste was primarily dumped on the surface of the ground and was not placed in trenches or buried. An estimated 1,200 cubic yards of waste were deposited in the landfill. No chemicals of concern were identified for soil or groundwater in the 2018 remedial investigation addendum.

The combined remedial investigation and remedial investigation addendum concluded that IRP Site 37 should no longer be considered a landfill because no burial of waste was observed. The geophysical survey did not identify disposal trenches, all waste appears to be limited to surface piles, and some of the construction debris exposed at the surface contains asbestos. There is no indication of a release of contaminants to surface soil, subsurface soil, or groundwater.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 40 is located approximately 1 mile north of the main administration buildings for the Randsburg Wash/Mojave B Complex. The site consists of three open trenches where solid waste from Randsburg Wash operations were reportedly buried from 1950 to 1975. Materials disposed of in the trenches consisted primarily of inert ordnance and range wastes. No chemicals of potential concern were identified for soil by the 2012 site inspection, and groundwater was not evaluated because it is expected to be very deep.

A geophysical survey was conducted between December 2018 and January 2019 that showed that the largest trench, which was partially open, also contains more areas of adjacent buried waste. The survey also found a second area of disposal south of the open trench.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will provide recommendations for future, additional CERCLA actions.

IRP Site 41 is located in Randsburg Wash, north of the main administration buildings. The site contains a trench where waste was reportedly buried in the 1950s and 1960s. The total quantities of waste oil and solvents disposed of were estimated to be 2,000 to 3,000 gallons each.

No chemicals of concern were identified in the 2004 remedial investigation. An attempt was made to install one monitoring well, but no groundwater was encountered to a depth of 275 feet below ground surface, and the borehole was abandoned. The remedial investigation concluded that reports of waste disposal in prior reports for IRP Site 41 were not accurate. Rather, it concluded that these wastes were disposed of in a nearby trench at AOC 154.

A no further action status was finalized in December 2014, and therefore IRP Site 41 is considered closed. Further action is being conducted at AOC 154.

IRP Site 67, the Lane Haven Dump, is located outside of the main China Lake Complex in the Indian Wells Valley. The site was used to dispose of trash from the Lane Haven Trailer Court from 1964 to 1981. The Navy acquired the property in 1981, and the dump may have been used later to dispose of drums of oil. The pit is uncovered, and interviews revealed that unauthorized dumping at the site had been an ongoing problem because the area was unsecured and readily accessible.

No evidence of drum disposal was found on the site during a 2000 site visit. No chemicals of potential concern were identified for soil during the 2012 site inspection. Groundwater was not investigated since it is expected to occur at a depth greater than 250 feet below ground surface. A geophysical survey was conducted in December 2018 with the goal of confirming that the dump was removed or to locate its actual location. The results of the survey showed no areas of significant burial at the site that would indicate a waste disposal trench or dump.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

IRP Site 84 is located in the Salt Wells Valley east of the Propulsion Laboratory. The site is not well documented historically, but it is believed that the area was used to stage and then burn waste materials from explosive tests. The operating dates are unknown. It was originally investigated in July 2003 as part of the remedial investigation conducted at the Propulsion Laboratory Operable Unit. It was subsequently moved to the AOC program for additional studies. Based on the results of the additional work, the Navy converted AOC 235 into IRP Site 84.

During the 2018 site inspection, metals in soil and hexavalent chromium, chlorinated solvents, and molybdenum in groundwater were identified as chemicals of potential concern. The site inspection concluded that further evaluation in the form of an additional remedial investigation or feasibility study is warranted.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 32 was reportedly located directly west of the airfield along Range Access Road. The site is a reported disposal area covered with soil that contains asbestos from demolition materials disposed of in the early 1980s. A December 2000 site reconnaissance discovered that a building and parking lot may be covering the burial area. In April 2005, another potential burial site was discovered but quickly ruled out. No samples have been collected at the AOC. The only remaining suspected location of the disposal area is beneath the building and parking lot.

Based on known information, the site was recommended for low priority for future evaluation. Although the site is currently considered part of the Landfill Operable Unit, the Navy is investigating it as part of a site inspection at IRP Site 80. A geophysical investigation will be conducted at AOC 32 within the parking lot to evaluate whether potential burial trenches or debris are present within the parking lot. If a potential disposal site is identified, then surface and subsurface soil samples will be collected for analysis of asbestos.

The results of the site inspection will inform the next steps at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 59 is located in the North Range area near the western boundary of the base. The site consists of a shallow trench that previously held several 55-gallon drums, most containing fluid that appeared to be motor oil. The Navy removed all drums as part of a range cleanup effort. Additionally, miscellaneous trash was present inside the trench, and there are areas of stained soil. All debris was also removed along with the drums. This area was once believed to be the location of buried trichloroethylene containers.

Total petroleum hydrocarbons, volatile organic compounds, polycyclic aromatic hydrocarbons, and arsenic were identified as chemicals of potential concern in soil in the 2006 preliminary assessment report. An attempt was made at three separate locations to install temporary monitoring wells to collect groundwater samples, but drilling equipment encountered bedrock that it was unable to penetrate before groundwater was encountered during all three attempts.

Based on previous studies, a 2010 report recommended AOC 59 no longer be considered high priority for future investigation. Although the site is currently considered part of the Landfill Operable Unit, the Navy is investigating it as part of a site inspection at IRP Site 80. Surface and subsurface soil and soil gas samples will be collected.

The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 64 is located in the central portion of the main base just south of Water Road. The site consists of scattered surface debris and an area of disposal trenches, along with a septic system, associated with Building X in Area ER. Area ER is the self-contained facility constructed in 1945 to develop the atomic bomb fuze and for drop tests. This area was active from 1945 to the 1980s. After World War II, all the buildings were eventually used for other projects.

The chemicals of potential concern identified at the site include total petroleum hydrocarbons, dioxins, pesticides, and radionuclides in soil as well as tetrachloroethene, perchlorate, and radionuclides in groundwater. The geophysical survey indicates that buried debris is still present in the old trenches at the site. The 2010 technical memorandum recommended further investigation, focusing on identifying whether the buried debris is responsible for the localized solvent detections in groundwater.

Although AOC 64 is currently considered part of the Landfill Operable Unit, the Navy planned to investigate AOC 64 as part of a site inspection at IRP Site 80. However, it was removed from the list of AOCs for the site inspection and will be addressed within the framework of the Navy’s radiological program, which is not part of the ERP.

AOC 85 is located in a series of drainages at the edge of a playa in Salt Wells Valley. The site is an abandoned landfill suspected to have received X-ray and photographic chemicals and other industrial wastes in the 1940s and 1950s. No significant burial was apparent during the 2018 site inspection. The chemicals of potential concern identified at the site include metals in soil and total petroleum hydrocarbons, chloroform, and metals in groundwater. Several metals were also identified as chemicals of potential environmental concern in the site inspection report.

A geophysical survey was conducted in December 2018 with the goal of defining any suspected disposal trenches at the site. The results of the survey showed no significant anomalies that would indicate a disposal trench, although some areas of shallow buried waste were identified in areas of surface debris.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was decided that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 99 is located near the eastern-central portion of the main base. The site was initially reported as an abandoned dump where debris was exposed at the surface. Dates of waste disposal are unknown. Various metals were identified as both chemicals of potential concern and chemicals of potential environmental concern for soil and groundwater.

AOC 99 is now being used for range operations and no longer falls under the CERCLA guidelines for evaluation. AOC 99 is recommended for removal from the IRP and transfer to the range sustainment program, where further evaluation may be required in the future.

AOC 102 is located in the northern portion of the main base. The site is an asbestos landfill that is well covered with soil and is marked with signs. The cover is a soil mound that directs water away and minimizes potential infiltration. The dates of disposal and the contents of the trench are unknown. An attempt was made to measure the depth to groundwater in a well during the 2005 investigation, but no water was encountered down to a depth of 300 feet. The only chemical of potential concern identified during the preliminary assessment was total petroleum hydrocarbons in soil.

The 2006 preliminary assessment recommended AOC 102 as a low priority for future evaluation. Although AOC 102 is currently considered part of the Landfill Operable Unit, the Navy is investigating AOC 102 as part of a site inspection at IRP Site 80. Further soil sampling will take place to assess potential soil impacts on the site.

The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 113 is located in the eastern portion of the main base near the Aircraft Survivability area. The site is a single open trench that was used to bury concrete rubble from demolition in the housing area. Dates of waste disposal are unknown. Various metals were identified as chemicals of potential concern and chemicals of potential environmental concern in soil during the 2018 site inspection. Based on the location of AOC 113, it was concluded that it would be unlikely that groundwater would be encountered in the area.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was decided that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 118 is located in the eastern portion of the main base near the Aircraft Survivability area. The site consists of two debris areas with partially buried wastes and an aircraft disposal site. Dates of waste disposal are unknown. Various metals were identified as chemicals of potential concern and chemicals of potential environmental concern in soil during the 2018 site inspection. Based on the location of AOC 118, it was determined that encountering groundwater in the area would be unlikely.

A geophysical survey was conducted in December 2018 with the goal of identifying whether any disposal trenches exist at the site or if the debris is surficial. The results indicated that there are no areas of significant waste burial at AOC 118, which confirms the initial assumptions.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 122 is an open trench near the live bombing administration area, located in the North Range area. Dates of disposal are unknown. Total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and acetone were identified as chemicals of potential concern in soil by the 2006 preliminary assessment.

The preliminary assessment recommended that AOC 122 be considered a low priority for future work. Although AOC 122 is currently considered part of the Landfill Operable Unit, the Navy is investigating AOC 122 as part of a site inspection at IRP Site 80. Further soil sampling will occur to evaluate the extent of potential soil impacts.

The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 124 consists of an aircraft debris dump within the active live bombing range, located in the North Range area. Dates of disposal are unknown. Cadmium and zinc in soil were identified as chemicals of potential concern during the 2018 site inspection. Groundwater was not evaluated but is expected to be around 50 feet below ground surface. Antimony, cadmium, copper, lead, and zinc were identified as chemicals of potential environmental concern in soil.

A geophysical survey was conducted in December 2018 with the goal of identifying whether any disposal trenches exist at the site or if the debris is only on the surface. The results indicated that areas of waste burial at AOC 124 are both associated with and nearby an observed pile of debris.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 131 is reportedly located in Salt Wells Valley, near the CT area. The site was a suspected buried disposal trench. The dates of operation are unknown, but most likely it was operational in the 1940s. No chemicals of potential concern or chemicals of potential environmental concern were identified in soil or groundwater in the 2006 preliminary assessment report.

The reported disposal trench could not be located after multiple interviews, reviews of aerial photographs, a search of documents, and two separate geophysical surveys. Therefore, the preliminary assessment recommended no further action for AOC 131. The site was included in the work plan for IRP Site 80 but will likely not be part of the site inspection because of the lack of evidence that the trench exists. A request for a no further action designation is planned for AOC 131.

AOC 154 is located in Randsburg Wash, northeast of the main administration area. The site consists of two large disposal pits or trenches that were the main disposal site for operations in Randsburg Wash from the early 1950s until use was discontinued in 1980. Approximately 3 cubic yards of waste per week were reportedly disposed of in this area. It was also reported that the waste piles were burned regularly.

More recent investigations have suggested that waste disposal attributed to trenches at IRP Site 41 may actually have occurred at AOC 154 because no evidence of disposal was found during investigation of IRP Site 41. As a result, the Navy, with state concurrence, closed IRP Site 41 and focused on the waste disposal identified at AOC 154. A geophysical survey supported by limited surface and subsurface soil sampling has identified a single, relatively large trench at AOC 154.

Total petroleum hydrocarbons, total cyanide, arsenic, and perchlorate were identified in the 2006 preliminary assessment report as chemicals of potential concern in soil. Assessment of groundwater has been problematic because the depth to groundwater at the site is believed to be up to 500 feet below ground surface. The site was part of a geophysical survey conducted between December 2018 and January 2019 to help with delineating the trench.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 173 is reportedly a covered, 5-acre dump located in the eastern portion of the main base just south of the Supersonic Naval Ordnance Research Track control and administration building. Dates of waste disposal are unknown. Minor staining was observed at the site during the site reconnaissance conducted in January 2001. Several burn areas, a small area of black tar, and several scattered areas of metal debris were also observed.

Groundwater was not encountered in a soil boring that went to 105 feet below ground surface and was therefore not sampled. The need to drill deeper using alternative methods was not warranted based on the analytical result for soil samples and the geophysical survey and exploratory trenching at the site. Total petroleum hydrocarbons and acetone were detected in soil and identified as chemicals of potential concern in the 2006 preliminary assessment report.

The preliminary assessment recommended the site as a low priority for further investigation. Although AOC 173 is currently considered part of the Landfill Operable Unit, the Navy is investigating the site as part of a site inspection at IRP Site 80. Samples will be collected to evaluate surface soils for dioxins, furans, and polycyclic aromatic hydrocarbons at the area of burned soil. The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 206 is located adjacent to the south base boundary along Inyokern Road. The site was reportedly used for disposal of industrial and construction debris from 1947 to the mid-1970s. Currently, an open pit is present and industrial, construction, and demolition debris is visible. Wastes include asbestos, construction debris, industrial waste, metal scrap, oil and grease, paints and thinners, wood scrap, and target debris. The analytes identified as chemicals of potential concern during the site inspection included arsenic in soil, and arsenic, manganese, and molybdenum in groundwater. Lead and zinc were identified as chemicals of potential environmental concern in soil.

The Navy conducted a 2018 site inspection for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 211 is located in the southwestern portion of the base just west of the Supersonic Naval Ordnance Research Track control and administration building. The site consists of disposal trenches and burn areas used to dispose of industrial wastes from research and development at the Supersonic Naval Ordnance Research Track from the 1960s to the 1980s. Total petroleum hydrocarbons, the explosive compound TNT, bromoform, acetone, dioxins, arsenic, and perchlorate were detected and identified as chemicals of potential concern in soil in the 2006 preliminary assessment report. Dioxins and perchlorate were detected and identified as chemicals of potential concern in groundwater.

The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 228 is located near the western boundary of the main base in Baker Range. The site includes a burned building, an associated underground storage tank, and a dump north of the building site. Historical information suggests the likely presence of unexploded ordnance in the dump. A septic system was reported but not located. The area was active in the 1940s and 1950s. Total petroleum hydrocarbons, benzene, furans, dioxins, polycyclic aromatic hydrocarbons, and metals were detected and identified as chemicals of potential concern in soil in the 2006 preliminary assessment report. Total petroleum hydrocarbons, semivolatile organic compounds, dioxins, metals, and perchlorate were detected and identified as chemicals of potential concern in groundwater.

The preliminary assessment recommended AOC 228 as medium priority for further investigation. Although the site is currently considered part of the Landfill Operable Unit, the Navy is investigating it as part of a site inspection at IRP Site 80. Further soil and groundwater samples will be collected from around the site to better gauge the level of contamination.

The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020, with no reported results yet available.

AOC 239 is located near the crest of the hill between the Indian Wells and Salt Wells Valleys, north of the China Lake Propulsion Laboratory gate. The site is a buried dump, possibly containing waste debris from chemical laboratories. The dates of disposal are unknown. AOC 239 was identified as the same location as AOC 161 during the April 2004 site visits. Based on drilling for this investigation, groundwater is not believed to exist in the unconsolidated soil beneath this AOC.

The chemicals of potential concern and chemicals of potential environmental concern identified during the site inspection at AOC 239 included explosives, polycyclic aromatic hydrocarbons, and metals in soil. Groundwater was not encountered even though drilling was completed to 80 feet below ground surface.

The Navy conducted a site inspection in 2018 for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 241 is located in the playa in the central portion of the main base. The site was built as a temporary ground range control facility for testing live and inert weapons while the G-1 and G-2 permanent facilities were under construction. The facility reportedly was most likely used for only a few years, possibly between 1945 and 1952. Recent information suggests that AOC 241, or portions of the AOC, are the same location as IRP Site 25.

Total petroleum hydrocarbons, volatile organic compounds, cyanide, pesticides, dioxins, polychlorinated biphenyls, and metals were identified in the 2006 preliminary assessment report as chemicals of potential concern for soil. Total petroleum hydrocarbons, carbon disulfide, metals, and chloride were identified in the preliminary assessment report as chemicals of potential concern for groundwater.

The preliminary assessment recommended AOC 241 as medium priority for further investigation. Although the site is currently considered part of the Landfill Operable Unit, the Navy is investigating it as part of IRP Site 80. Further soil samples from both the surface and subsurface will be collected from around the site to better gauge the level of contamination.

The results of the site inspection will inform the next steps taken at the site. The field activities were planned for 2020 , with no reported results yet available.

AOC 242 is located near the western boundary of the main base in Baker Range. The site is an unlined open trench. Surface photographs date the trench to the 1940s and 1950s. The trench contains boxes of film, empty 55-gallon drums, wood debris, and trash. The chemicals of potential concern identified during the 2018 site inspection at AOC 242 included arsenic and manganese in soil, and total petroleum hydrocarbons and metals in groundwater. Lead, molybdenum, vanadium, and zinc were also identified as chemicals of potential environmental concern in soil at AOC 242.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

AOC 243 is located in Area R near the intersection of Pole Line Road and Water Road. The site consists of three specific disposal trenches designated Trenches 1, 2, and 3. The trenches were first identified as part of the 1996 preliminary assessment investigation for the Area R OU. Based on historical aerial photographs, the trenches were in use as early as 1949, and Trench 2 was filled in by 1979. Trenches 1 and 3 remain partially open.

The chemicals of potential concern identified during the 2018 site inspection at AOC 243 included thallium in soil and hexavalent chromium in groundwater. Chemicals of potential environmental concern identified in soil included cadmium, lead, mercury, and zinc.

The Navy conducted a site inspection for several of the AOCs under the Landfill Operable Unit. It was determined that further evaluation as part of a remedial investigation or feasibility study is warranted for this site. The site is being included in a data gaps work plan for the Landfill Operable Unit sites. Fieldwork will be completed in the winter of 2020 and 2021 and documented in a draft technical memorandum anticipated to be available in the summer of 2021. The technical memorandum will recommend additional, future CERCLA actions.

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IRP Site 4 is located in a remote area of the Salt Wells Valley portion of the China Lake Complex. The site consists of an area where beryllium-contaminated equipment reportedly had been burned and buried. The Navy conducted experiments on beryllium-based propellants at the China Lake Propulsion Laboratory from the early 1960s until 1965. Approximately 900 cubic yards of burned scrap equipment and materials were disposed of at the site. IRP Site 4 includes only the area where this waste was reportedly buried. The site was abandoned after the experiments ended.

Beryllium was the only chemical of potential concern at IRP Site 4 based on past site use and conclusions of the 1997 and 2002 preliminary assessments, although beryllium was not found to be a chemical of potential concern or chemical of potential environmental concern for soil by additional site inspections conducted in 2012.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed. The Navy is currently awaiting the joint agency no further action determination letter.

IRP Site 5 is located in the central portion of the China Lake Complex off G-2 Tower Road in the Indian Wells Valley. IRP Site 5 consists of an area where hazardous waste chemicals were transported to and burned with other propellant, explosive, and pyrotechnic material from 1968 to 1979. It has been estimated that 1,200 cubic yards of these waste materials were incinerated at IRP Site 5. Burro Canyon is managed under a Resource Conservation and Recovery Act Part B permit (non-CERCLA) and continues to be used to treat explosive hazardous waste. No chemicals of potential concern or chemicals of potential environmental concern were identified for IRP Site 5.

The Navy has deferred IRP Site 5 from the IRP since the site is under Resource Conservation and Recovery Act interim status. Resource Conservation and Recovery Act corrective action will be initiated for this site, if necessary.

IRP Site 6 was an open burn facility for propellant, explosive, and pyrotechnic wastes and contains six distinct areas with pits, trenches, and aboveground tanks used for open burning. Past operations included disposal of wastes in trenches or pits. This range site was used from 1946 to 1975.

The remedy published in the 2006 record of decision for IRP Site 6 focuses on consolidation of waste piles and debris and placement of an engineered cover over Areas 1, 2 and 3. Perchlorate, barium, and the explosive RDX are the chemicals of concern for soil at IRP Site 6. Groundwater was assessed and is not present at the site.

Consolidation and construction work at the site began in November 2010 and work for Areas 1, 2, and 3 was completed in February 2012. After additional contaminated waste was discovered at Area 4, a removal action was undertaken to construct another engineering cover for both soil in Area 4 and for excavated soil from the Propulsion Laboratory Operable Unit.

Ongoing activities at IRP Site 6 include implementation of land use controls and maintenance programs to ensure the engineering covers are functioning correctly. A post-closure maintenance plan was prepared for the site to outline requirements for monitoring cover settlement, inspecting the integrity of the covers and surrounding drainage controls, reporting any cover impacts that may require repairs, and describing repair procedures.

The remedy in place at IRP Site 6 will continue to be evaluated in five-year reviews. The next five-year review is planned for 2022.

IRP Site 12 is located near the southern boundary of the main China lake Complex in the Indian Wells Valley. The site includes a 15-acre landfill that received approximately 100 tons of solid waste per year from 1952 to 1979. The landfill was closed in 1979 by capping it with a native soil cover. No chemicals of concern or chemicals of environmental concern were identified for soil at IRP Site 12 by 2000 remedial investigation risk assessments, and arsenic, the single chemical of concern, was identified for IRP Site 12 groundwater.

A third five-year review was completed in 2016 and included document and data review, site inspections, personnel interviews, regulatory agency comments, and report development. The report noted that no activity considered inconsistent with use as a closed landfill was present and concluded that the remedy at IRP Site 12 was protective of human health and the environment. The report further recommended that the Navy conduct annual site inspections during the next five-year review period. Annual inspections will continue, and the next five-year review will be completed in 2022.

IRP Site 14 is located within the Indian Wells Valley in the southern portion of the China Lake Complex. The site is described as the ER Range septic system, which includes five septic tanks, a leach field, and piping from the buildings to the tanks and leach field. From 1950 to 1981, etching process fluids, cooling tower fluids, and sanitary wastewater were reported to have been discharged into the septic system from the adjacent laboratory buildings. Etching wastewater is residual material collected from the etching process, which used chromic acid to produce a pattern or design on metal. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil or groundwater at IRP Site 14 by the site inspection.

The Navy initiated a 2012 supplemental site inspection, which included IRP Site 14. The risk assessments did not identify any chemicals of potential concern or chemicals of potential environmental concern for the site.

In January 2014, the regulatory agencies requested further testing for hexavalent chromium in soil and groundwater. Surface and subsurface soil samples and groundwater samples were collected in May 2019, and the results will be published in a technical memorandum. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 16 is located in the southern portion of the China Lake Complex in the Indian Wells Valley. The site is a septic system that from 1950 to 1981 received sanitary waste from buildings in the G-1 Range complex, primarily photo-processing waste from the range telemetering ground station. The septic system was abandoned in 1981 when the buildings were connected to the City of Ridgecrest sewage treatment plant. Over the 31 years of operation, the system’s maximum flow of sanitary wastes was estimated to be 1,800 gallons per day. Photo-processing waste that may have contained metals, volatile organic compounds, and cyanide was released at a rate of approximately 30 gallons per day. The 1997 preliminary assessment and 2002 site inspection did not identify any chemicals of potential concern or chemicals of potential environmental concern for soil or groundwater at IRP Site 16.

The Navy initiated a supplemental site inspection in 2012, which included IRP Site 16. The risk assessments did not identify any chemicals of potential concern or chemicals of potential environmental concern for the site.

Further soil and groundwater sample collection was requested by the regulatory agencies in January 2014. In May 2019, additional samples were collected and analyzed for cyanide and metals in soil and volatile organic compounds, metals, cyanide, hexavalent chromium, nitrates, sulfate, thiocyanate, and coliform in groundwater. The results will be published in a technical memorandum. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 17 is located in the southern portion of the China Lake Complex in the Indian Wells Valley. The site consists of a septic system that received wastewater from a former range operation building and other surrounding buildings from 1950 to 1981. An estimated 4,600 gallons per day of wastewater were received by the system, 100 gallons per day of which were explosive and photographic laboratory wastewater. The septic system was abandoned in 1981 when the buildings were connected to the City of Ridgecrest sewage treatment plant. The 1997 preliminary assessment and 2002 site inspection did not identify any chemicals of potential concern or chemicals of potential environmental concern for soil or groundwater at IRP Site 17.

The Navy initiated a supplemental site inspection in 2012, which included IRP Site 17. The risk assessments identified vanadium as a subsurface chemical of potential concern for the site, and trichloroethene and several metals as chemicals of interest for groundwater. No unacceptable risk to ecological receptors was identified.

In January 2014, the regulatory agencies requested further sample collection. In May 2019, surface soil samples were collected and analyzed for perchlorate and explosives. The results did not detect any explosives, although perchlorate was detected in all three samples. The 2020 technical memorandum for the additional sampling recommended that IRP Site 17 be designated with no further action status for soil. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 18 is located just east of the China Lake Propulsion Laboratory main gate in the main China Lake Complex. The site consists of six AOCs located within 3 miles of each other. The main features are leach fields and cesspools that received a wide variety of wastewater chemicals from 1950 to 1981. Based on the 1997 and 2002 preliminary assessments, diethylphthalate, cadmium, lead, selenium, silver, and thallium were identified as chemicals of potential concern or chemicals of potential environmental concern in soil at IRP Site 18.

The Navy initiated a supplemental site inspection in 2012, which included IRP Site 18. The risk assessments identified metals as chemicals of potential concern and chemicals of potential environmental concern for soil at the site but designated no further action for groundwater based on its absence at the site.

In January 2014, the regulatory agencies requested further soil sampling within the sludge bed. Samples were analyzed for volatile organic compounds, semivolatile organic compounds, explosives, perchlorate, total nitrogen, and metals. Based on the data collected, further sampling will be conducted to evaluate the extent of diethylphthalate and metals in soil at IRP Site 18, although no further action status was warranted for groundwater. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 28 is located in the Indian Wells valley in the main south-central portion of the China Lake Complex. The site consists of a large unpaved area used to store a variety of items. Transformers were reportedly stored at the site from 1965 to 1970. Since then, the area has reverted to desert habitat. The potential sources of contamination at IRP Site 28 include leakage from transformers stored at the site or possible widespread application of waste oil for dust suppression. The chemicals of potential concern or chemicals of potential environmental concern identified for IRP Site 28 during the 1997 and 2002 preliminary assessments and 2005 site inspection included polychlorinated biphenyls, pesticides, polycyclic aromatic hydrocarbons, dioxins, furans, and metals. Groundwater has not been investigated at IRP Site 28.

The Navy initiated a supplemental site inspection in 2012, which included IRP Site 28. Based on the data collected, the supplemental site inspection recommended further sampling to evaluate the extent of contaminants at IRP Site 28. The Navy is conducting a remedial investigation at IRP Site 28 to better define the nature and extent of contamination in both soil and groundwater. The results of the remedial investigation will inform further actions.

IRP Site 31 is in the Indian Wells Valley, approximately 2,400 feet south-southeast of the NAWS China Lake main gate. The site consisted of a small unpaved area where, from 1945 to 1980, rinse water contaminated with pesticides and herbicides and concentrated solutions of pesticides and herbicides were reportedly discharged directly onto the ground. The system was improved in 1980. Pesticides, primarily chlordane, and arsenic were identified as chemicals of potential concern for soil at IRP Site 31 and were addressed by removal actions. No chemicals of potential concern were identified at IRP Site 31 for groundwater based on phase I remedial investigation sampling.

The additional removal action was conducted at IRP Site 31 in 1999. Based on the analytical results, the 2000 removal action report concluded that no further removal action was necessary. During meetings and site tours conducted at the site in January 2014, the Navy and the regulatory agencies identified the need for additional data.

The Navy sampled groundwater at IRP Site 31 in spring 2016 to confirm that the site had not contaminated shallow groundwater, and a small number of soil samples were also collected. The spring 2016 data report recommended considering no further action status for groundwater at IRP Site 31. The data also confirmed residual soil contamination in the area, warranting further evaluation. The Navy is currently preparing a remedial investigation work plan for the site, with field activities planned for 2021. The results of the remedial investigation will inform further actions.

IRP Site 32 is located within the Indian Wells Valley in the northern portion of the main base adjacent to the western side of the golf course. The site consisted of a small unpaved area where rinse water contaminated with pesticides and herbicides was reportedly discharged directly onto the ground from the mid-1960s to 1980. An estimated 1,000 gallons of rinse water may have been discharged onto the soil each year. In 1980, a concrete pad, drain, and underground reinforced concrete vault used for containment were installed at IRP Site 32. Pesticides were identified as human health chemicals of concern for soil at IRP Site 32 and were addressed by a removal action. No chemicals of concern were identified at IRP Site 32 for groundwater based on phase I remedial investigation sampling.

The Navy and regulatory agencies identified additional data needs at the site during meetings in January 2014. The Navy therefore sampled groundwater at IRP Site 32 in spring 2016 to confirm that the site had not contaminated shallow groundwater. The new data verified the lack of pesticides or other organic chemicals in groundwater but found elevated concentrations of metals in several wells. The data also found elevated concentrations of pesticides in soil at the site. The Navy is currently preparing a remedial investigation work plan for the site, with field activities planned for 2021. The results of the remedial investigation will inform further actions.

IRP Site 35 is located within the Indian Wells Valley, west of Armitage Field in the main China Lake Complex. This location is the site of a Supersonic Naval Ordnance Research Track accident. In 1961, an experimental propellant that included 4 pounds of beryllium accidentally detonated in the gun barrel of the artillery test equipment. Residual dust and the contaminated equipment were reportedly removed from the ground surface and buried at what is now IRP Site 35. The depth of the burial pit is unknown. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil at IRP Site 35 during the 1997 and 2002 preliminary assessments and 2012 site inspection. Groundwater was not evaluated but is expected to be greater than 150 feet below ground surface, based on area well data.

The Navy submitted no further action status documentation for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed.

IRP Site 36 is located within the Indian Wells Valley, west of Armitage Field in the China Lake Complex. IRP Site 36 was a storage facility for sheds that from 1956 to 1962 stored hazardous chemicals including nitric acid, furfuryl alcohol, aniline, and dimethyl hydrazine. According to records, some were occasionally spilled. The total volume of spills reported was less than 300 gallons, and it has been theorized that 70 percent of these chemicals volatilized on the soil surface. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil at IRP Site 36 during the 2006 preliminary assessment and 2012 site inspection. Groundwater was not evaluated but is expected to be greater than 150 feet below ground surface based on area well data.

The Navy submitted no further action documentation for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board requested a remedial investigation and additional sampling of both soil and soil gas before a no further action determination could be made. As a result, a remedial investigation will be completed under a future contract.

IRP Site 38 was reportedly located in the northwestern corner of the China Lake Complex. The site consists of two trenches where, according to early reports, approximately 1,000 cubic yards of inert waste generated during explosives test programs were disposed of from 1968 to 1979. However, according to NAWS China Lake employees interviewed during 1996 and 1999 visits, only one trench, called Excavation No. 2, received wastes. The waste from Excavation No. 2 was hauled off site in 1990. No evidence of hazardous material disposal was observed at the site during the 1996 and 1999 site visits. The 1997 and 2002 preliminary assessments and 2012 site inspection did not identify any chemicals of potential concern or chemicals of potential environmental concern for soil or groundwater at IRP Site 38.

As a result of historical waste removal and re-grading, the exact location of a historical disposal area has never been identified, and no samples have been collected. As a result, the 2012 supplemental site inspection concluded that no further action is warranted at IRP Site 38. In January 2014, the Navy and regulatory agencies agreed to move forward with a no further action determination, and the site may be included in a future no further action record of decision.

IRP Site 39 is a former disposal pit located in the Coso Range. In the 1970s, geothermal drilling muds and oily liquid waste were disposed of in an open pit adjacent to an exploratory geothermal well in the Coso Range. The pit and exploratory well were properly closed in 1979, and the well was reportedly sealed in accordance with state requirements. Soil and groundwater samples were not collected at IRP Site 39 because the initial 1997 preliminary assessment found no evidence for releases of contaminants. Therefore, no chemicals of potential concern or chemicals of potential environmental concern were evaluated or identified.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed.

IRP Site 42 is located 20 miles east of the main administration buildings for the Randsburg Wash/Mojave B Complex. IRP Site 42 consists of an unlined pit where about 30 partially filled 55-gallon drums of an unknown fuel were burned in the mid-1970s. The burning was a one-time event, and the site was not used for any subsequent disposal. The pit contained the empty, burned drums. There was no evidence of staining or residual contamination. The 1997 and 2002 preliminary assessments did not identify any chemicals of potential concern or chemicals of potential environmental concern for soil at IRP Site 42. Groundwater was not evaluated but is expected to be very deep based on data for other Randsburg Wash IRP sites.

The Navy initiated a supplemental site inspection in 2012, which included IRP Site 42. The risk assessments did not identify any chemicals of potential concern or chemicals of potential environmental concern for the site.

The Navy is currently conducting a site inspection at the site to characterize the nature and extent of contamination, update the risk assessment, and identify future actions. The site inspection report will recommend further steps.

IRP Site 43 is located in the central portion of the main China Lake Complex within the Indian Wells Valley. The site consists of a large concrete pad, known as the Mini-Deck, that was used as a platform where a fire on an aircraft carrier deck could be simulated during firefighting test operations. The Mini-Deck was used intermittently for firefighting tests from at least 1965. Trainees were required to extinguish the fire using aqueous film forming foam. From 1979 to 1987, an estimated 300,000 gallons of wastewater consisting of a mixture of water, uncombusted fuels, and aqueous film forming foam were discharged to an unlined evaporation pond. In 1987, a lined holding pond was constructed and was subsequently removed in 1992.

A 2004 remedial investigation report recommended no further action status and moving the site from the CERCLA program to the Resource Conservation and Recovery Act program even though the chemical of concern naphthalene had been identified in soil and naphthalene and benzene had been identified in groundwater. Since the report was finalized, the Navy has chosen to proceed with remedial action for soil and groundwater at IRP Site 43. A 2006 feasibility study recommended a combination of monitored natural attenuation, industrial controls, bioventing, and biosparaging.

More monitoring wells were installed in spring 2016, and it was concluded that the current site chemicals of concern, benzene and naphthalene, as well as other petroleum-related constituents have persisted at the site. Per- and polyfluoroalkyl substances was also discovered at the site, so continued groundwater monitoring was recommended.

Because of the presence of per- and polyfluoroalkyl substances, IRP Site 43 is being re programmed to include a remedial investigation and feasibility study for per- and polyfluoroalkyl substances and a proposed plan and record of decision that will include all contaminants at the site.

IRP Site 48 is located within the Indian Wells valley in the east-central portion of the China Lake Complex. The site consists of two unlined holding ponds that received all the wastewater and fuel generated at the Weapons Survivability Laboratory from 1976 to 1985. Several tests per year that used jet fuel in quantities of up to 300 gallons were carried out at the Weapons Survivability Laboratory. The ponds were still in use from 1985 until 1991 but were lined with concrete. In 1993, the liners were removed, and the areas were backfilled. The soil and groundwater beneath the two former unlined holding ponds were investigated as IRP Site 48. The 1997 preliminary assessment did not identify any chemicals of potential concern or chemicals of potential environmental concern for soil or groundwater at IRP Site 48.

The Navy is conducting a site inspection at IRP Site 48 to fill data gaps. Surface and subsurface soil samples and groundwater samples will be collected to better delineate the nature and extent of contamination.

The Navy will develop a site inspection report for IRP Site 48 from the results of the 2020 field investigation and after all analytical data have been received. The report and results will be used as a basis for recommending further actions at the site. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 52 is located in the main China Lake Complex in the Indian Wells Valley. The site consists of a firing arena used as an explosive test area starting in at least 1949. Before 1978, tests that involved firing at drums of jet fuel may have occurred, though these tests could not be confirmed during personnel interviews. Except for the potential use of fuel drums before 1978, no other hazardous materials beyond general ordnance would be expected at IRP Site 52. Soil and groundwater samples were not collected at IRP Site 52 because the initial 1997 preliminary assessment found no evidence for releases of contaminants. Therefore, no chemicals of potential concern or chemicals of potential environmental concern were evaluated or identified.

Although IRP Site 52 was included in the 2018 draft site inspection work plan, the Navy agreed to remove the site from the CERCLA program and place it under the NAWS China Lake Resource Conservation and Recovery Act program because base personnel indicated that the site was still being used for testing.

IRP Site 53 is located in the main China Lake Complex in the Indian Wells Valley. The site consists of a laboratory building, a septic tank, and an associated leach line. In 1970, the building was used as an infrared electronics, optical, and chemical laboratory. The building was converted to office use in 1976 and is still an active facility. Initial reports indicated that wastewater containing hazardous materials may have been discharged from the laboratory. Soil and groundwater samples were not collected at IRP Site 53 because the initial 1997 preliminary assessment found no evidence for releases of contaminants, resulting in no identification or evaluation of any chemicals of potential concern or chemicals of potential environmental concern.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed.

IRP Site 54 is located in the restricted Area R Test Range in the Indian Wells Valley. The site consists of two slit trenches reportedly excavated to receive spent Celotex bundles and scrap lumber from tests at the Area R Warhead Firing Arena beginning in 1967. Celotex is a nontoxic, biodegradable material made primarily from cellulose, with minor amounts of starch and bound by paraffin wax. The materials in both trenches were burned at least twice to create space for additional disposal. Photo-processing chemical bottles were found floating in reddish water and were removed in the late 1980s. The site has not been used since 1988. Dioxins and furans were identified as chemicals of potential concern or chemicals of potential environmental concern for soil at IRP Site 54. No chemicals of potential concern were identified for groundwater.

The Navy initiated the supplemental site inspection in 2012, which included IRP Site 54. Results of the human health risk assessment identified dioxin in surface and subsurface soil as a potential risk. The ecological risk assessment did not identify any unacceptable risk to ecological receptors. The Navy plans to collect additional samples under a remedial investigation to evaluate the release of dioxins and furans at the site. As part of a remedial investigation at the site, sampling will occur for groundwater, surface and subsurface soils, and suspected asbestos-containing material in the trenches. After the conclusion of fieldwork, a remedial investigation report will recommend further steps.

IRP Site 59 is located in the Armitage Field complex in the Indian Wells Valley. The site consists of a warehouse constructed to store tires and brakes. Between 1952 and 1983, materials were stored in the yard west of the warehouse. Some NAWS China Lake employees have said that the yard was also used to store 55-gallon drums containing solvents, hydraulic fluids, and motor oil. Soil and groundwater samples were not collected at IRP Site 59 because the initial 1996 preliminary assessment found no evidence for releases of contaminants, resulting in no identification or evaluation of any chemicals of potential concern or chemicals of potential environmental concern.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

IRP Site 60 is located in the western portion of the China Lake Complex in the Indian Wells Valley, near the base boundary. The site is a former hut used as a control tower during flight tests on the B-2 Range. The hut was reportedly buried when the site was abandoned. The foundation for the hut is all that is believed to remain. A pile of wood, tar paper, plaster, particle board siding, and scrap metal found in the wash is believed to be the remains of the hut. No chemicals of concern or chemicals of environmental concern were identified at IRP Site 60.

As a result of previous investigations, the 2000 supplemental preliminary assessment recommended that IRP Site 60 be classified as an area of no suspected contamination. Although the Navy has pursued a no further action determination, the Regional Water Quality Control Board has requested that groundwater data be collected before no further action status can be considered. Therefore, additional data and potential closure under a no further action record of decision will be pursued.

IRP Site 61 is located in the southwestern portion of the China Lake Complex in the Indian Wells Valley. The site consists of a dump used to dispose of miscellaneous debris from about 1952 to 1953. An empty 55-gallon stainless steel drum was also present at the site. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil or groundwater at IRP Site 61.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board stated it was not appropriate for the Navy to base closure rationale on information provided in the unpublished 2005 site inspection report. It was considered not appropriate since the document had not been submitted for review and approval by the Regional Water Quality Control Board. The site may become eligible for no further action status after agency review of the 2005 site inspection report.

IRP Site 62 is located at the end of the B-4 Range access road and the B-4 track in the Indian Wells Valley. IRP Site 62 consists of an area used as a small machine shop in the early to mid-1950s and as a full-scale machine shop from at least 1980 to 1997. Two Points of Interest were identified within the footprint of IRP Site 62. These are Point of Interest 57, the machine shop, and Point of Interest 58, the oil and gasoline storage shed. Point of Interest 58 consisted of three sheds that were built in 1953 but destroyed by 1987. The location of the sheds is uncertain. Various metals were identified as chemicals of potential concern or chemicals of potential environmental concern for soil at the site, and various radionuclides were identified as chemicals of potential concern for groundwater at the site.

The Navy initiated the supplemental site inspection in 2012, which included IRP Site 62, and confirmed the site risk associated with the site chemicals of potential concern and chemicals of potential environmental concern.

Further sampling was recommended under the supplemental site inspection to evaluate the extent of metals contamination in surface soil. No further evaluation was recommended for subsurface soil, while further sampling of groundwater was recommended. The Navy will work with the regulatory agencies to define the path forward for IRP Site 62.

IRP Site 63 is located near the southern boundary of the main China Lake Complex in the Indian Wells Valley. The site consists of a concrete pad that was used to rinse dumpsters. The Dempsey Dumpster Station was used from approximately 1944 to 1965 to rinse out dumpsters after the contents — which potentially including pesticides, oils, paints, and thinners — were dumped at the Pilot Plant Road Landfill. Chemicals of potential concern or chemicals of potential environmental concern identified in IRP Site 63 soil include mercury, polychlorinated biphenyls, dieldrin, and lead. Groundwater was not investigated at the site. Area well data indicates that groundwater may be greater than 70 feet below ground surface.

In May 2019, the Navy collected additional surface and subsurface soil samples at IRP Site 63 to address data gaps and undertake further assessments in support of site closure. Based on these results, the recommended approach for IRP Site 63 is to delineate the lateral extent of pesticides and polychlorinated biphenyls in the surface samples only.

IRP Site 65 is located within the main China Lake Complex in the Indian Wells Valley, northeast of the intersection of Water Road and Pole Line Road, near the China Lake playa. The site is a paved area with concrete pads used for mounting large-diameter guns and missile launch mechanisms, used since 1962 or possibly as early as 1955. Small amounts of hazardous materials were reportedly used to clean and maintain weapons at the site. The gun emplacements have been in this area since at least 1976, and perhaps as early as 1965. Before 1991, small amounts of chlorinated solvents, light oil, hydraulic fluids, and grease were reportedly used to clean and maintain weapons at the site. After 1991, the weapons were steam-cleaned on site, and solvents were not used. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil or groundwater at IRP Site 65.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board requested further groundwater sampling for volatile organic compounds and perchlorate, as well as further information on the weapon steam-cleaning process. The site may be included under a future remedial investigation for sites requiring additional data.

IRP Site 66 is located in the Indian Wells Valley, approximately 2,000 feet east of G-2 Tower Road on Burro Canyon access road in the central portion of the main China Lake Complex. The HANS Test Site was constructed in the late 1970s to evaluate the effects of burning composite materials, and especially carbon fibers. Jet propellant 5 was used during these tests and was reportedly contained within an unlined dirt-bermed area at the site. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil at IRP Site 66. Groundwater was not investigated but is expected to occur at a depth greater than 150 feet below ground surface.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board requested the Navy proceed with a remedial investigation for soil sampling at the site to delineate the extent of total petroleum hydrocarbon contamination. The site may be included under a future remedial investigation for sites requiring additional data. Additional investigation will also be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection work plan, which is currently being prepared.

IRP Site 73 is located in the Randsburg Wash/Mojave B Complex along an unnamed road northeast of the main administration buildings. The site was used to assemble flash charges for explosives testing from 1952 to 1962. The flash charges contained magnesium powder and black powder consisting of potassium nitrate, sulfur, and charcoal. Black powder loses its explosive potential on contact with water, so the building was hosed down after each charge was assembled. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil at IRP Site 73. Groundwater was not investigated but is expected to occur at a depth greater than 240 feet below ground surface.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board approved the no further action decision and indicated that a determination letter for the site is being developed.

IRP Site 74 is located in the Randsburg Wash/Mojave B Complex at the intersection of the Randsburg Wash access road and Gun Line Road. The site consists of a leach field that received discharged sanitary and industrial wastewater from six facilities from 1951 to 1993. Between 1993 and 1996, a paved road was constructed through the leach field. Signs reading “Do not drive in posted area” were posted at the site. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil at IRP Site 74. Groundwater was not investigated but is expected to occur at a depth greater than 240 feet below ground surface.

In May 2019, the Navy collected additional surface and subsurface soil samples at IRP Site 63 to address data gaps and undertake further assessments in support of site closure. A technical memorandum presenting the results of the investigation is being prepared. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances work plan, which is currently being prepared.

IRP Site 75 is located near the main administration buildings of the Randsburg Wash/Mojave B Complex. The site consists of a gas station constructed in approximately 1951. A 1,500-gallon gasoline underground storage tank and a 300-gallon waste oil underground storage tank were used at the site. The waste oil underground storage tank was removed in 1991 and the gasoline underground storage tank in 1992. The gasoline pumps on the service island and associated piping were also removed at approximately that same time. No chemicals of potential concern or chemicals of potential environmental concern were identified at IRP Site 75. Petroleum constituents at IRP Site 75 were addressed under the NAWS China Lake UST Program, and the site was closed.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board requested the Navy proceed with a remedial investigation for soil gas sampling at the site, explicitly to delineate the extent of contamination in the vapor phase. The Navy will work with the regulatory agencies to establish a path forward for closure of IRP Site 75 under the CERCLA process.

IRP Site 76 is located in the Randsburg Wash/Mojave B Complex, east of the main administration area at the end of Gun Line Road. The site consists of an area used by the U.S. Marine Corps from 1943 until 1947 as a firing and bombing range. In 1947, the Navy took over the area, and the site was used to fire bombs from gun emplacements and rocket launchers. The site is now used infrequently and is maintained on a stand-by basis. Before 1978, the guns were cleaned by applying solvents with a brush and then wiping the guns down with rags. After 1978, solvents were no longer used to clean the guns, and the guns were steam-cleaned at a separate facility. No chemicals of potential concern were identified for soil, but lead was identified as a chemical of potential environmental concern for soil at IRP Site 76. Although not investigated at IRP Site 76, groundwater is anticipated to be 240 feet below ground surface or deeper.

In accordance with a 2017 work plan, the Navy planned to collect additional samples at IRP Site 76 to further assess the site and address data gaps in support of site closure. Surface and subsurface soil samples were to be analyzed for volatile organic compounds and metals. Because of unresolved explosives concerns at IRP Site 76, the field investigation and sampling were not completed. A remedial investigation will be conducted under a future contract.

IRP Site 77 is located near the City of Ridgecrest sewage treatment facility in the Indian Wells Valley in the southern portion of the China Lake Complex. The site consists of a pit that was dug in 1986 to temporarily hold oily sludge. Based on the pit’s dimension, it contained an estimated 2,700 gallons of oily material. Interviews with site personnel indicated that the oily material was “road slurry” or “cooking oil.” No other substances were reportedly held in the pit, and the oily material was reportedly removed by vacuum truck shortly after the Navy discovered it, and the pit was filled with native soil. The surface soil at IRP Site 77 has since been disturbed by construction associated with sewage treatment plant operations. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil or groundwater at IRP Site 77.

Subsurface soil samples and groundwater samples were collected to evaluate whether a release had occurred from the sludge pit that might pose a threat to human health or the environment. The 2012 supplemental site inspection concluded that site conditions and analytical data indicate that no further action is warranted at IRP Site 77.

The Navy submitted documentation for no further action status for finalization in 2015. In February 2018, comments from the Lahontan Regional Water Quality Control Board requested the Navy proceed with a remedial investigation for groundwater sampling at the site, explicitly to further evaluate the presence of total petroleum hydrocarbons and molybdenum. The site may be included in a future remedial investigation for sites requiring additional data.

IRP Site 78 is located in the southwestern portion of the China Lake Complex within the Indian Wells Valley, near the Supersonic Naval Ordnance Research Track Control Building. The site consists of sumps that may have been used to discharge photographic wastes from a film processing laboratory between 1955 and 1963. Interviews with site personnel during the preliminary assessment indicated that film was never developed at the Supersonic Naval Ordnance Research Track, but later interviews did not support the earlier statement. Sometime between 1985 and 1988, the pipeline to the sumps was disconnected and redirected to a septic tank. After this re-routing, no wastes were drained into the laboratory sumps. No chemicals of potential concern or chemicals of potential environmental concern were identified for soil. Groundwater was not investigated but is expected to occur at a depth greater than 150 feet below ground surface.

In May 2019, additional samples were collected at IRP Site 78 to further assess the site and address data gaps in support of site closure. Four surface and four subsurface soil samples were collected and analyzed for metals, volatile organic compounds, and cyanide. A technical memorandum presenting the results of investigations is in Navy review. The Navy will work with the regulatory agencies to establish a path forward toward no further action.

IRP Site 79 has been deferred from the IRP and from CERCLA, and further action will be taken under the Navy Master Materials License. These actions will include decommissioning the testing areas impacted by depleted uranium in accordance with the Navy Master Materials License requirements.

IRP Site 80 represents the AOCs that have been identified at NAWS China Lake to date. Although the number of AOCs requiring further action under the IRP is still being evaluated, the majority of the AOCs are in the preliminary assessment and site inspection stage of the remedial process. Several AOCs have been included in OUs and are being addressed along with the IRP sites that are included in them. IRP Site 80 is also used to conduct per- and polyfluoroalkyl substances investigations and support the basewide groundwater monitoring program for programming budgets.

IRP Site 81 is located near a former Public Works construction camp, just north of the Supersonic Naval Ordnance Research Track access road. The site is a dump that accepted waste generated at NAWS China Lake only. Limited observations during a preliminary site walk conducted on May 30, 2017, indicate that materials such as inhomogeneous concrete slabs and piles of soil and sand were disposed of on the surface of the site. No chemicals of potential concern or chemicals of potential environmental concern have been identified at IRP Site 81 because the preliminary assessment and site inspection for IRP Site 81 have not been completed.

The ongoing preliminary assessment includes an on-site and off-site reconnaissance of the site. Fieldwork for the site inspection was completed in 2019 and included sampling soil for chemicals of potential concern, including asbestos and typical chemicals associated with surface debris sites. The site inspection report is being prepared and will be published in 2020 or 2021. Both human health and environmental risk assessments will use data from the report, and the results of the investigation will guide future actions.

IRP Site 82 is located in the eastern portion of Salt Wells Valley and consists of a building within the Skytop test complex. Live and inert ordnance and rockets were burned inside a building at the facility. The building was constructed of steel rebar and wire mesh to contain potential exploding ordnance or rockets during tests. Various types of rockets were routinely tested or detonated inside the building. The chemicals of potential concern or chemicals of potential environmental concern identified in the 2018 site inspection risk assessment include dioxins, cadmium, manganese, nickel, copper, and the explosive RDX in soil. Groundwater was not evaluated because groundwater has not been encountered at this site.

Based on the site history and the results of this sampling, the Navy recommended that IRP Site 82 be considered a high-priority for further evaluation. The Navy is currently conducting a remedial investigation at the site with the objective of filling data gaps and updating risk assessments. Additionally, the presence or absence of per- and polyfluoroalkyl substances will be confirmed at other areas of IRP Site 82, as these compounds were detected during the limited site inspection sampling conducted previously. The remedial investigation fieldwork will be completed in 2020, and the results of the investigation will guide future actions.

IRP Site 83 is located in the western portion of the main base, part of Charlie Range. The site was used to store miscellaneous equipment used on Charlie Range. A transformer maintenance site, which was operated in the 1970s, was in the southwestern corner of the compound. A former range employee noted an area that was used for emptying transformers. Potential wastes include polychlorinated biphenyls, waste oils, and solvents. The 2018 site inspection risk assessment identified arsenic, polychlorinated biphenyls, hexavalent chromium, dieldrin, cadmium, and manganese in soil and delta-BHC in groundwater as chemicals of potential concern or chemicals of potential environmental concern.

Based on the results of the previous investigations, the Navy recommended that IRP Site 83 be considered a high priority. Although it is likely that the pesticide compounds detected at IRP Site 83 are a result of routine application, as has been observed at many sites at NAWS China Lake, the polychlorinated biphenyl results indicate that a release occurred. The Navy is currently conducting a remedial investigation at the site. Groundwater as well as surface and subsurface soil will be sampled. The remedial investigation fieldwork will be completed in 2020, and the results of the investigation will guide future actions.

IRP Site 86 is a former Navy housing area demolished in the 1990s that now consists of two dirt lots totaling 16 acres. When the housing was demolished, asbestos-containing materials were containerized and disposed of at appropriate off-site facilities, except for some roofing materials that remained on site. Initial sampling took place in May 2018, and further sampling occurred in June 2018. Neither event found any asbestos fibers in any samples. In July 2018, ambient air was sampled at a nearby Child Development Center, where once again no asbestos was detected.

A preliminary assessment report and site inspection work plan for asbestos-containing material are being completed. Fieldwork is planned for 2021.

IRP Site 87 consists of eight non-contiguous dirt lots totaling 723 acres that were once Navy housing areas. Like IRP Site 86, the structures were demolished in the 1990s. At the time, asbestos-containing materials were containerized and disposed of at appropriate off-site facilities, except for some roofing materials that are still on site. The sites have not been investigated for asbestos.

A preliminary assessment report and site inspection work plan for asbestos-containing material are being completed. Fieldwork is planned for 2021.

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IRP Site 85 was assessed and cleared of environmental and munitions issues before the Navy took ownership of NAWS China Lake. IRP Site 85 is closed with no further action.

MRP Site 1 is a 2.82-acre area located in the south-central portion of the China Lake Complex. The site contains two separate and adjacent ranges belonging to the Sierra Desert Gun Club and the China Lake Police Department. Constructed in 1969, the Sierra Desert Gun Club Small Arms Range was used for recreational shooting and Navy training programs. The site was used for small arms training, primarily with shotguns, small caliber machine guns, and small caliber pistols. Live firing of machine guns and shotguns at the Sierra Desert Gun Club Small Arms Range was discontinued in 1990 but use of air rifles and pistols (pellet guns) continued at the site until 1995. The range is no longer operational.

The China Lake Police Department Pistol Range was constructed in the late 1950s and was used for small arms training, recreational shooting, Navy training programs, and training for station security personnel. Live firing at the China Lake Police Department Pistol Range was discontinued in 1990, and the range is no longer operational.

A preliminary assessment was completed in 2006 and a site inspection in 2011. A remedial investigation addressing site inspection recommendations for MRP Sites 1, 3, and 4, is under way, and fieldwork will be completed in 2021.

MRP Site 2 is an approximately 644-acre area located within the former Mojave Aerial Gunnery Range Cat Marine Corps Auxiliary Air Station Mojave, in California. The site is administratively managed by NAWS China Lake, even though the site is not located on the facility. The site was used from 1944 to 1959 for bombing, strafing, and machine gun practice, primarily by aircraft stationed at former Marine Corps Auxiliary Air Station Mojave. The former range is closed and is no longer in use. The 2011 site inspection did not identify any chemicals of potential concern at Mojave Target 71.

A supplemental site inspection was completed in 2015 that involved digital geophysical mapping, which identified 138 subsurface geophysical anomalies in the 8.4-acre survey at MRP Site 2. Corroded small arms ammunition and six pieces of munition debris were identified on the ground surface, predominantly in the northernmost part of the site. A remedial investigation for MRP Site 2 is being finalized and a feasibility study is currently being developed.

MRP Site 3 is an approximately 7-acre area located adjacent to MRP Site 4, just north of Armitage Field. Constructed in 1952, the Armitage Field Skeet Range was used until the early 1960s. The primary use for the range was to train pilots to fire on moving targets. The range has a single firing line with a fan-shaped debris pattern and no berms. Firing from the line was to the north, using shotguns and clay targets. There are no structures at the site, and the range is no longer operational.

A preliminary assessment was completed in 2006 and a site inspection in 2011. A remedial investigation addressing site inspection recommendations for MRP Sites 1, 3, and 4, is under way, and fieldwork will be completed in 2021.

MRP Site 4 is a 2.3-acre area located adjacent to MRP Site 3 on the northeastern edge of Armitage Field. Constructed in 1946, the range was used for synchronizing or general emptying of aircraft-mounted machine guns. The aircraft were lined up on a concrete apron and chained down; the guns were fired into the target butt. The target butt was composed of a railroad tie wall backed with earthen fill. The range was reportedly used until the early 1960s for small-caliber machine gun rounds and projectiles.

A preliminary assessment was completed in 2006 and a site inspection in 2011. A remedial investigation addressing site inspection recommendations for MRP Sites 1, 3, and 4, is under way, and fieldwork will be completed in 2021.

MRP Site 4 is an approximately 475-acre area located in the southwestern portion of the China Lake Complex, about a mile west of the Armitage Field runway. The site was investigated as AOC 36 in the past. It was used as a simulated target area during air shows between 1950 and 1970. Weapons that are believed to have been used at the site include a wide selection of missiles and rockets, bombs, napalm bombs, and 20-millimeter rounds. Targets used for the shows included old aircraft hulls, white phosphorus marks, flares, and drums. The area is divided into three separate target zones based on current debris and areas of disturbance. There are no structures at the site, and the range is no longer operational.

The preliminary assessment was completed in 2006 and the site inspection in 2011. The site inspection recommended that MRP Site 5 be considered for a remedial investigation for additional characterization. Insufficient data currently exist to make definitive conclusions. In addition, potential munitions or explosives of concern were identified during the preliminary assessment at one location. Given the site history and the size of the area, more munitions or explosives may be present.

The Navy is further developing and refining the approach for additional investigation at MRP Site 5 based on the recommendations from the site inspection.

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UST 1 is the site of a former 10,000-gallon tank located at the NAF Gas Station, at the northern end of the airfield’s fire station. The gas station was constructed around 1945. The tank was removed in 1992, and monitoring wells were installed. Free product was initially reported in two wells near the former tank. Passive free product skimming devices (well socks) were installed at these wells in the 1990s, and by May 2003 only a petroleum sheen was reported in one of the wells.

Monitoring of NAF Gas Station wells continued after 2003, and additional light non-aqueous phase liquid was recovered on an as-needed basis. The total volume of light non-aqueous phase liquid recovered from the former NAF Gas Station wells between 1997 and September 2014 is estimated at 41 gallons. From December 2016 to April and May 2018, light non-aqueous phase liquid was detected in two wells. Maximum reported thickness of the light non-aqueous phase liquid at both wells never exceeded 0.2 foot, indicating that that light non-aqueous phase liquid has been removed to the extent practicable. Groundwater sampling also revealed the presence of 1,2-dichloroethane and benzene.

A preliminary corrective action plan was submitted in September 2020 detailing potential treatment alternatives and included a data gap investigation. The most recent basewide groundwater monitoring report recommends continuing semi-annual groundwater monitoring and sampling at the former NAF Gas Station monitoring wells to evaluate groundwater, light non-aqueous phase liquid levels, and contaminant concentration trends with time. Based on data gathered during the data gap investigation for the corrective action plan and the monitoring program, continued monitoring, no further action, or remedial measures will be recommended as appropriate for the NAF Gas Station.

UST 2 includes three fuel oil USTs associated with boiler plants. Boiler Plant No. 1 is the site of a former 100,000-gallon tank and was reportedly built in 1952. Boiler Plant No. 2 housed a 100,000-gallon tank, and Boiler Plant No. 3 housed a 26,000-gallon tank. All three failed a leak test in April 1991.

In July 1995, the 100,000-gallon UST located at Boiler Plant No. 1 was emptied and cleaned. Soil samples were collected from below the tank. Results of the sampling indicated additional site characterization was warranted. Therefore, soil borings were advanced in the vicinity of the tank in July 1996, including two slant borings under the bottom of the tank. Five groundwater monitoring wells were also installed. The site characterization report, completed in February 1997, indicated that the potential risks at Boiler Plant No. 1 were negligible and recommended no further action at the site. In May 1997, a tank was closed in place with the concurrence of Kern County and the Lahontan Regional Water Quality Control Board.

Groundwater monitoring at Boiler Plant No. 1 began in December 1997. Twelve sampling events were conducted using the five monitoring wells at the site between December 1997 and May 2003. Elevated total petroleum hydrocarbon concentrations were observed and became the driver for more remedial action. To enhance degradation of hydrocarbon in groundwater, an oxygen-release compound was injected into the subsurface aquifer at 12 injection location near the UST in April 2002. After the injections, total petroleum hydrocarbon concentrations in groundwater significantly decreased.

Releases were discovered at Boiler Plants No. 2 and No. 3 as a result of tank tightness testing in April 1991. The case for the tank at Boiler Plant No. 2 was closed in December 1997 and the leak at Boiler Plant No. 3 was addressed by removing the UST and contaminated soil. Kern County authorized site closure in January 1996. Based on the results of groundwater sampling events and the conclusions of the Resource Conservation and Recovery Act assessment, a non-CERCLA assessment, the Navy requested the Boiler Plant No. 1 UST site be assigned closure status in December 2003. No further action was approved by the Lahontan Regional Water Quality Control Board in May 2007.

UST 3 includes the Naval Exchange (NEX) Gas Station and the Former Public Works Gas Station, two former gas stations at NAWS China Lake. The NEX Gas Station was constructed in 1967 and remains active today as a gas station and auto repair facility. The gas station was serviced by three 12,000-gallon steel underground storage tanks containing gasoline and one smaller steel underground storage tanks waste oil. The waste oil tank and one of the gasoline tanks were removed in 1990 and 1991 and were found to be leaking. The remaining tanks and piping showed evidence of leaking and were eventually replaced in 1993. The pipelines and fuel dispensers for the gas station were also replaced during this time, and an uncapped pipe was discovered during the replacement.

Groundwater was investigated in three phases in 1989 and 1990 by installing six monitoring wells near the tank locations. Further subsurface investigations of both soil and groundwater were conducted in 1991. The uncapped pipe was eventually considered the primary source of fuel hydrocarbon releases detected in the subsurface. In fall 1995, five soil vapor extraction wells were installed at the NEX Gas Station, with full-scale soil vapor extraction beginning in April 2000, designed to remove petroleum hydrocarbons from the vadose zone to prevent migration to groundwater. Between April 2000 and August 2002, approximately 24,460 pounds of petroleum hydrocarbons were removed from the soil, including 90 pounds of benzene.

The Navy has submitted a request for a site closure report for the NEX Gas Station site. The request for site closure was based on analytical results from four consecutive groundwater monitoring events, where declining concentrations were observed over four events. The Navy will be submitting a revised closure request with additional groundwater data to the Lahontan Regional Water Quality Control Board. Based on data showing significant degradation of petroleum constituents at the site, the Navy anticipates closing this UST case.

The Former Public Works Gas Station was constructed in 1945. In September 1991, two 10,000-gallon gasoline USTs, one 10,000-gallon diesel UST, and one 500-gallon waste oil UST were excavated and removed from the site. Soil samples collected from the tank excavations were found to be contaminated with petroleum hydrocarbons.

An air sparging system was installed on the site in 1993 to remediate the petroleum-contaminated soil. Groundwater and free product extraction systems were installed at this time, and an optimization pilot test was performed in 1999. This system was used from October 2002 until September 2005. A mobile product recovery system was also implemented in spring 1995, and from then until 2001 it removed 687 gallons of fuel product. In 1997, groundwater samples were collected from groundwater monitoring wells at the Former Public Works Gas Station. Free-phase liquid hydrocarbons were present on the water table at six monitoring wells at the site, and about 3 gallons of product were removed from 2008 to 2014. A total of 16 wells have been monitored since 2002, with semi-annual monitoring since 2008.

In 2001, free product was discovered in a U.S. Geological Survey monitoring well 360 feet north of the Former Public Works Gas Station site, but no link was found between this product and the site itself. Additional investigation is planned.

An investigation was included in the corrective action plan to confirm that the groundwater plume is continuing to decrease and that conditions at the site continue to meet the media-specific criteria. After this investigation, the Navy will prepare and submit a letter requesting closure. Receipt of a final closure letter was anticipated in spring 2021, but there is no indication that it has been received yet.

UST 4 is the site of leak from a tank that contained gasoline and was associated with the China Lake Propulsion Laboratory Battery Shop. The leak was discovered in October 1991 during tank closure. The leak was addressed immediately when it was discovered and notes no further remedial actions. No further information regarding the extent of the release or associated investigation or cleanup was located. The UST case was closed in March 1996.

UST 5 is the site of the IOB Gas Station in the North Ranges of NAWS China Lake, built in 1981. Two USTs are associated with the site, a 6,000-gallon gasoline tank and a 1,000-gallon diesel tank. Between November 1989 and June 1992, both USTs were leak tested a total of four times. Both tanks were judged to be sound based on the results of the leak tests. In February 1992, approximately 5 inches of an unidentified petroleum product was noted on the water surface in a groundwater monitoring well 5 feet southwest of the gasoline UST. The presence of product was reported to the Lahontan Regional Water Quality Control Board in March 1992.

A preliminary investigation conducted in June 1992 evaluated whether the presence of product in the monitoring well adjacent to the gasoline UST was a result of a leak from the USTs or associated piping. The investigation concluded that the petroleum hydrocarbon product was highly localized and of minor concern. It also concluded that the likely source was a motor oil drum resting on the gasoline UST pad, which leaked onto adjacent unpaved soil.

In January 1994, the 6,000-gallon gasoline UST, 1,000-gallon diesel UST, and associated piping and dispensers were removed. Approximately 44 cubic yards of hydrocarbon-contaminated soil was also removed during the UST removal. Groundwater sampling indicated soil located beneath the diesel dispenser contained minor gasoline and diesel fuel contamination. Groundwater within the tank excavation contained typical gasoline contaminants, including elevated concentrations of total petroleum hydrocarbons and benzene, toluene, ethylbenzene, and xylene.

Long-term groundwater monitoring at the IOB Gas Station began in December 1997 with seven monitoring wells. Based on 11 consecutive groundwater sampling events between December 1997 and May 2003, contamination was limited to a single well at the center of the former UST area, and contaminant concentrations in that well declined significantly over the period. To enhance biodegradation of the hydrocarbons in groundwater, an oxygen-release compound was injected at 10 direct-push points into the aquifer near the former UST in April 2002.

Closure was requested in 2003, noting that the limited groundwater contamination had stabilized based on observed trends in the groundwater sampling events, and that natural degradation was occurring at the site. The Lahontan Regional Water Quality Control Board granted closure in March 2007.

UST 6 is the site of a warehouse that housed two 100-gallon fuel oil USTs from the time they were installed in 1940 until they were removed in 1990. They were operational until 1979 when the building was converted to natural gas. During removal, soil samples collected from below each tank were analyzed for total petroleum hydrocarbons and benzene, toluene, ethylbenzene, and xylene. Analysis indicated total petroleum hydrocarbons were detected in the soil beneath both tanks, and xylenes were detected in the soil beneath one tank.

A preliminary investigation conducted in September 1991 installed six boreholes in the vicinity of the former USTs. Samples were again analyzed for total petroleum hydrocarbons and benzene, toluene, ethylbenzene, and xylene, and total petroleum hydrocarbons were detected between 24 and 29 feet below ground surface in the vicinity of one tank. Monitoring wells were installed in three boreholes near one of the tanks and sampled quarterly from July 1998 to December 1999. No analytes were detected above laboratory reporting limits.

Two additional groundwater monitoring wells were installed near one of the former tanks and sampled quarterly between January 2001 and September 2001. Low concentrations of various petroleum hydrocarbons were detected in both soil and groundwater samples.

Closure was requested in February 2002, citing removal of the source of contamination, the low-volatility nature of the contamination, the limited areal and vertical extent of significantly affected soil, the low likelihood of migration of contaminants, the distance to potential receptors, and based on a comparison of analytical data to applicable regulatory levels. The Lahontan Regional Water Quality Control Board granted closure in September 2003.

UST Site 7 is located within the Propulsion Laboratory and is the site of two former 10,000-gallon fuel oil tanks, which were removed from the area in 1976. Two other USTs were also used to store fuel oil on-site.

In November 1991, a 32,000-gallon UST was removed from the Boiler Plant No. 4 site. Soil samples collected at the time indicated total petroleum hydrocarbons and oil and grease contamination were present. Depth to groundwater at the site exceeds 150 feet below ground surface, and no groundwater samples were collected during the tank removal.

In October 1992, the site characterization report was completed, and no further action was recommended. Lahontan Regional Water Quality Control Board staff requested a toxicity characteristic leaching procedure leachability test of the soil at the site. The results of the test indicated a low potential for leachability of petroleum contamination. As a result, the Lahontan Regional Water Quality Control Board granted closure in June 1997.

UST Site 8 was reassigned to the IRP program. The site is now known as IRP Site 75.

UST Site 10 was reassigned to the IRP program. The site is now known as IRP Site 1.

The CLPL Gas Station was built in approximately 1944 in the Propulsion Laboratory main gate administration area on the comer of C Street and 5th Street. It was serviced by one 10,000-gallon gasoline UST, one 550-gallon fuel oil UST, and one 250-gallon waste oil UST.

In July 1989, precision leak tests were conducted on the three USTs. The tests indicated that the 10,000-gallon gasoline UST was leaking. Based on inventory records and results of the tests, approximately 6,000 gallons of gasoline may have leaked between September 1988 and April 1989. The quantity of product released prior to September 1988 is unknown. In July 1989, the 10,000-gallon gasoline UST was emptied and removed from service. In September 1989, all three USTs were excavated and removed from the site.

Preliminary site characterizations conducted in 1990 and 1991 identified the source of petroleum hydrocarbons in the soil as gasoline associated with the former 10,000-gallon gasoline UST but did not fully characterize the extent of contamination. The fuel oil and waste oil USTs did not appear to have impacted soils at the site. Corrective action, including installation of soil vapor extraction wells, pilot testing, and a soil vapor extraction wells system were conducted from 1992 to 1995, but the soil vapor extraction wells system was shut down in 1995 due to technical issues. Soil gas sampling was conducted in May and September 1997. The results showed decreases of soil gas concentrations between the May and September sampling events, and significant decreases when compared with July 1992 results.

A 2001 site assessment delineated the extents of residual petroleum hydrocarbon and volatile organic compound contamination in subsurface soil and groundwater at the site. Soil gas sampling data also indicated a significant reduction of contaminant concentrations in soil due to natural attenuation. Limited groundwater affected by the leak from the former gasoline UST was encountered in the fractured bedrock, and 0.03 feet of free-phase gasoline product was identified in one monitoring well. The site assessment recommended initiation of free-phase product recovery from the one monitoring well and continued groundwater monitoring. Following the site assessment, additional pilot testing was conducted to evaluate remediation alternatives. The Navy plans to evaluate existing data to develop a sampling approach for future actions.

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AOC 1 is a dump site located in the Salt Wells Valley near the Skytop complex in a canyon wash south of the T-range facility. There is no historical information regarding the source or date of the waste material. Potential wastes include solvents, construction debris, metals, and wood scrap.

The 2006 preliminary assessment report considered AOC 1 a low priority for future investigation. The Navy is investigating AOC 1 as part of a site inspection at IRP Site 80. Sampling at AOC 1 for the investigation will be conducted to evaluate surface soils, characterize additional AOC surface debris areas features, evaluate potential soil impacts at the intermittent wash area, and further characterize the extent of metals above soil screening levels in the northern portion of the site.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 3 is located near Armitage Field and was thought to be an aircraft burial area used to discard and burn aircraft that were in operation in the mid-1940s. Aerial photographs from 1945 and 1952 show heavy staining of the dirt around the runways and close to the burn site. Scattered aircraft debris, metal, wood scrap, electronic parts, 55-gallon drums, and refuse were observed during a site reconnaissance conducted in April 2004. Former aircraft landing pads, transformer pad, and minor areas of stained soil were also observed at the site. However, no large disposal areas, heavy staining, or burn areas were observed. Potential wastes at the site include solvents, construction debris, metals, and wood scrap.

The 2006 preliminary assessment report considered AOC 3 a low priority for future investigation. The Navy is investigating AOC 3 as part of a site inspection at IRP Site 80. Sampling at AOC 3 will be conducted to evaluate surface soils for risk assessment, characterize the former transformer pad area for polychlorinated biphenyls, and collect background data for metals in soil outside the AOC boundary to assess whether detected metals within the AOC are within background ranges.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 7 is located near the Aircraft Survivability area of the main base and includes an enclosed 10-foot-diameter metal tunnel used for burning carbon composites. The structure is above ground and was operated from 1978 to 1979 and from 1982 to 1983. Wastes reportedly included carbon composites, paints, and paint thinners. Three 3-inch-wide expansion cracks were observed along the tunnel, and an abandoned paint locker was also noted during a site reconnaissance conducted in December 2000. A drum storage area is located at the southern end of the AOC boundary. There is a pond in the area, but it is reportedly not associated with the AOC.

A screening-level risk assessment was recommended with the data collected thus far to evaluate whether detected compounds of arsenic pose a risk to human health or the environment. The Navy is investigating AOC 7 as part of a site inspection at IRP Site 80. Sampling at AOC 7 will be conducted to evaluate surface soils to characterize the drum storage area and areas near the cracks along the tunnel and to analyze for constituents that have not been assessed. Based on historical composite burning operations, samples will be analyzed for per- and polyfluoroalkyl substances and dioxins and furans. In addition, a surface water sample may be collected for analysis from the pond.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 19 is within the boundaries of the Area R OU. AOC 19 was a staging area for aircraft before they were disassembled and used in tests at NAWS China Lake. Potential wastes include avgas, motor oil, hydraulic fluid, and organic lead deposited from the early 1950s through the 1970s. In 2003, scattered aircraft parts and debris and old oil stains on soil were observed at the site during a site reconnaissance. Based on visual observations, the oil did not appear to penetrate the soil more than 2 inches beneath the surface. There was evidence of subsequent grading across the site.

A 2012 supplemental site inspection recommended additional surface soil sampling to evaluate the extent of organic lead and polychlorinated biphenyls. The Navy is conducting additional site inspections for AOC 19 under IRP Site 80. Sampling will be conducted to evaluate surface soils in areas of staining, to collect discrete subsurface soil samples where prior composite samples were collected, to characterize the metal debris pit areas, and to evaluate potential soil impacts at the wash.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 21 is a fenced storage compound within IRP Site 15 that contained empty 55-gallon drums and exhibited areas of stained soil. Initial reports stated that one drum was stainless steel and possibly was used for storing hydrazine. The area also contained old rockets, cluster bombs, and other potential unexploded ordnance. The drums and potential unexploded ordnance were removed after the initial site visit and before the 2006 preliminary assessment sampling. Potential wastes include metals, metal filings or powder, live and inert ordnance, and wood scrap deposited in the 1950s. AOC 21 is an active area, with operations including maintenance and storage.

The 2012 supplemental site inspection report stated that no evidence was found suggesting that soil or groundwater poses a threat to human or ecological receptors and that no further action is warranted at AOC 21. To support this recommendation, the Navy is conducting additional site inspections for AOC 21 under IRP Site 80. Soil and soil gas samples will be collected to evaluate potential sources of volatile organic compounds within the AOC boundary, and soil and soil gas samples from areas of potential volatile organic compound sources will also be analyzed. Additionally, soil samples will be collected for arsenic analysis outside of the AOC boundary to assess whether detected arsenic concentrations are within background ranges.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 22 is a dry well within the Area R complex that consists of an 8-inch-diameter steel well casing that protrudes 0.6 foot above ground surface. Wastes that may have been disposed of in this well include fuels and solvents. Dates of disposal are unknown.

No evidence was found during the 2012 supplemental site inspection to suggest soil or groundwater poses a threat to human or ecological receptors. Only trace amounts of total petroleum hydrocarbon compounds and volatile organic compounds were detected in groundwater from the existing well at AOC 22. Based on these detections, a temporary well was installed to collect an additional sample for analysis of volatile organic compounds. The sample showed no detections of these compounds. The 2012 supplemental site inspection report concluded that conditions and analytical data indicate that no further action is warranted at AOC 22. The report also recommended that the dry well be decommissioned to prevent any future disposal. However, the Navy is conducting additional site inspections for AOC 22 under IRP Site 80 because this report has not been finalized.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 29 is a 5-acre disturbed site posted as an “explosive test area” located with the Area R complex near the intersection of Water Road and Pole Line Road. The area holds laboratory and industrial trash disposed of in the 1940s. Potential wastes include electronic equipment, metal scrap, wood scrap, industrial waste, and miscellaneous chemical compounds. Based on a site reconnaissance in December 2000, debris piles containing wire, wood, and rocket parts were observed at the northern portion of the site. An area of burned soil was observed at the central portion of the site, and drum storage racks were present at the southern portion of the site.

The 2012 supplemental site inspection report indicated that no further action is warranted at AOC 29 because no evidence was found during the site inspection that suggests soil or groundwater pose a threat to human or ecological receptors. The 2006 preliminary assessment recommended that a more comprehensive asbestos survey be conducted, and any exposed asbestos be removed. However, the Navy is conducting additional site inspections for AOC 29 under IRP Site 80. Soil samples will be collected for asbestos analysis at the northern and southern portions of the site, and the burned soil area will be further evaluated.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 36 was originally part of the Armitage Field OU but was reassigned from the IRP to the MRP. The site is now known as MRP Site 5.

AOC 45 is a circular area about 75 feet in diameter that was used to dispose of and burn napalm in the 1960s. It is located immediately east of the airfield and, reportedly, the circular pit was routinely filled with napalm and set on fire. Potential wastes included components of napalm, fuels, solvents, metals, and wood scrap.

During the 2012 supplemental site inspection, none of the chemicals identified as chemicals of potential concern in soil and groundwater were recommended for further evaluation. However, the Navy is conducting additional site inspections for AOC 29 under IRP Site 80. Soil and soil gas will be sampled under the site inspection for AOC 45 to characterize the extent of possible contaminants at the site.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities are planned to begin in 2020. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

AOC 50 is located near administration buildings east of the airfield. AOC 50 reportedly received general refuse, aircraft debris, target debris, chemical compounds, wood scrap, and metal scrap from 1945 to the 1970s. Aerial photographs from 1973 show the dump to be approximately 5 acres, and a 1981 photograph revealed that the dump was covered. Based on a site reconnaissance in December 2000, scattered debris, waste piles, concrete pads, a burn area, aboveground storage tanks for water, and stained soils were observed at the site. The area is currently located near several office buildings that support airfield activities.

No evidence was found during the 2012 supplemental site inspection to suggest that soil poses a threat to human or ecological receptors. Groundwater in the area is being monitored as part of the Armitage Field OU. The 2012 supplemental site inspection report recommended no further action at AOC 50. However, the Navy is conducting additional site inspections for AOC 50 under IRP Site 80. Soil will be sampled to evaluate dioxins and furans in soil at the burned soil area and at features that have not been previously assessed, the waste piles and concrete pads. Additional soil samples will be collected for analysis of metals outside of the AOC boundary to assess whether previously detected metals concentrations at the AOC are within the background range.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

AOC 70 was a facility used for fire suppression tests located in a playa within the central portion of the main base. The dates of operation of the facility are unknown. It consists of a 200-foot by 250-foot gravel-lined pit and a steel structure made to hang thick metal sheets in the center of the pit. Open fires heated the large metal plates, changing the fire-fighting characteristics. It does not appear that an impermeable liner was installed below the gravel to prevent infiltration. Fuel staining and odors were observed within the pit during a site reconnaissance conducted in April 2004.

No significant contamination was observed based on the results of the initial 2006 preliminary assessment. However, more data were collected given the site history and shallow depth to groundwater. The additional data confirmed the lack of widespread contamination, especially with respect to the groundwater beneath the AOC. The 2010 technical memorandum noted that site activities and the corresponding chemical detections did not represent a significant release that requires further characterization, but also recommended that the data be evaluated with respect to potential human health and ecological risks, and a decision then be made about the need for soil removal or site closure. The Navy is conducting additional site inspections for AOC 70 under IRP Site 80. Soil and groundwater samples will be collected for per- and polyfluoroalkyl substance analysis within and downgradient from the former fire training pit. In addition, soil and groundwater samples will be collected to evaluate potential impacts from the shallow, bermed pit located southeast of the central training area.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available. Additional investigation will be completed in 2021 in accordance with the basewide per- and polyfluoroalkyl substances site inspection.

AOC 82 is located in the northern portion of the main base. AOC 82 consisted of both aboveground and underground storage tanks used to store fuel for electrical generators. One 650-gallon UST and one 300-gallon UST were removed.

Soil samples collected as part of the 2006 preliminary assessment show contamination is limited to total petroleum hydrocarbon compounds and selected metals. As a result, a screening-level risk assessment was recommended to evaluate whether the contaminants of interest pose a potential risk to human health or the environment before any additional investigation is undertaken. Because of the remote location of AOC 82, the preliminary assessment recommended that the potential impacts to ecological receptors be emphasized, and that AOC 82 be considered a low priority site. The Navy is conducting additional site inspections for AOC 82 under IRP Site 80, although no data gaps have been identified, and additional sampling at AOC 82 was not recommended.

Under the site inspection, AOC 82 will be recommended for no further action after the screening-level ecological and human health risk assessments have been completed using existing historical analytical data.

AOC 83 is an inactive hazardous substance storage area in Salt Wells Valley. The operational dates of the storage area are unknown. Previously discovered surface debris and signs that are currently posted on the site indicate past storage of hazardous substances. An area of stained soil in the central portion of the site was reportedly excavated to a depth of 3 feet below ground surface. Three active electrical transformers are located just west of the AOC 83 boundary.

Based on the investigation results, the 2006 preliminary assessment recommended a screening-level risk assessment to evaluate whether the detected compounds pose a potential risk to human health or the environment before any additional steps are taken. It recommended that AOC 83 be considered a low priority for future work. The Navy is conducting additional site inspections for AOC 83 under IRP Site 80. Surface and subsurface soil samples will be collected to assess the transformers for polychlorinated biphenyls and one of two excavated stained soil areas where no previous sampling was conducted.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 98 is located in the playa area of the central portion of the main base. The site encompasses two separate bomb craters, each approximately 20 to 30 feet in diameter. The depth of the craters is unknown because they extend below the water table in the area. Reports indicate that both craters may have been used to dispose of waste. Potential wastes include paints and thinners, fuels, solvents, and metals. Dates of waste disposal are unknown.

Based on the investigation results, the data collected from sediment and surface water do not indicate that hazardous substances were disposed of in the craters, and the 2006 preliminary assessment recommended AOC 98 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 98 under IRP Site 80. Discrete sediment samples will be collected and analyzed for chemicals of potential concern for use in the screening-level risk assessments. Surface water samples will be collected for analysis of total and dissolved metals constituents.

Site inspection results will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 106 includes several historical wells located throughout the base, primarily in the western portions of the main base. This AOC is intended as a catchall for all homestead wells at NAWS China Lake. Many of the wells are left over from ranches and homesteads that predate the Navy’s operation in the area, although some are newer and are a result of training by the Navy construction battalion.

The homestead wells have been divided into three categories based on their location. Those primarily on the ranges are identified as AOC 106R or 106, those within the C Corridor are identified as 106A or 236, and those within the G Corridor are identified as AOC 106B or 237. The C and G Corridors are portions of the City of Ridgecrest that were taken over by the Navy for safe-flight operations but are not fenced as part of the base. These corridors contain several old wells that at one time may have supplied drinking water to residents.

Based on the results of the AOC investigation, it does not appear that the wells were used in the past to dispose of hazardous waste of any kind because no significant contamination was detected in any of the samples. However, only a limited number of wells — many of which were poorly sealed, located in areas directly accessible to the public, and screened in the deep aquifer underlying the China Lake area — could be sampled under the AOC program. As a result, the 2006 preliminary assessment concluded that AOC 106 is a larger issue than could be addressed during the AOC investigation. No further action was recommended under the AOC program, but the Navy should consider further actions to manage these wells such as sealing or decommissioning these wells. Lockable well caps were added to previously open wells, and the Navy is conducting additional site inspections for AOC 106 under IRP Site 80. No data gaps have been identified so no additional sampling at AOC 106 has been recommended. In addition, AOC 106 is being removed from the IRP program.

AOC 120 is located in the southern portion of the main base. AOC 120 is a burial area used by local kennels in the 1960s and 1970s. It consisted of a series of 5-foot-diameter by 40-foot-deep pits. Potential wastes include quicklime and dead animals.

Based on investigation results, the 2006 preliminary assessment recommended a screening-level risk assessment to confirm that these compounds do not pose a potential risk to human health or the environment, and AOC 120 be considered a low priority for future work. The Navy is conducting additional site inspections for AOC 120 under IRP Site 80. No data gaps have been identified so no additional sampling at AOC 120 has been recommended.

Under the site inspection, AOC 120 will be recommended for no further action status after the screening-level ecological and human health risk assessments have been completed using existing historical analytical data.

AOC 143 is located throughout the current and historical housing areas of the Mainside portion of the base and involves waste oils used for dust suppression basewide in the 1940s and 1950s. This AOC was studied as part of a larger investigation throughout the housing areas and schools on base in 1999 and 2000. Potential use of polychlorinated biphenyl-contaminated oil in dust suppression and routine application of pesticides were the focus of the investigation. Other constituents of concern such as lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons were not part of the analytical suites for either surface or subsurface soil samples.

Based on the results of the previous investigations, the 2006 preliminary assessment recommended AOC 143 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 143 under IRP Site 80. A surface survey will be conducted during the site inspection to document areas of potential lead-based paint debris at the active and inactive housing buildings that may have impacted the surficial soils. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead. Seven soil samples will be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents in the waste oils used for dust suppression have impacted the surficial soils.

Site inspection results will indicate whether immediate, investigative, or no of further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 161 and AOC 239 were originally listed separately during the Point of Interest study but were subsequently identified as the same location during April 2004 site visits. See AOC 239 for a site description.

AOC 163 is located near the southern edge of the main base near the Sandquist Gate. The site consists of a concrete pad near the NOTS Construction Camp, AOC 213, just west of the Sandquist Gate. The sources of waste at this AOC are spills from construction-related storage and activities as well as dumping street sweeping debris. Potential wastes include oil and grease, fuels, and wood scrap. Dates of waste disposal are unknown.

Four samples each of surface and subsurface soil were collected in 2001. Analytical suites included metals, semivolatile organic compounds and total petroleum hydrocarbons, and volatile organic compounds. Organic compounds were detected at concentrations below residential preliminary remediation goals. Total petroleum hydrocarbon compounds in subsurface soil were detected at a much lower level than at the surface, indicating only minimal infiltration. Arsenic was the only inorganic compound present at concentrations that exceeded background and residential preliminary remedial goals.

Based on the investigation results, the 2006 preliminary assessment recommended AOC 163 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 163 under IRP Site 80. Under the site inspection, soil samples will be collected to evaluate surface soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 166 was reassigned to the IRP in 2018. AOC 166 is now known as IRP Site 82.

AOC 176 consists of a raised concrete platform with a roof and a concrete slab connected at ground surface. The site is located in the eastern portion of the main base just south of the Supersonic Naval Ordnance Research Track control and administration building. The source of potential waste is steam-cleaning discharges at this former old acid storage and degreaser station. Potential wastes include solvents, acids, hydraulic oil, oil and grease, gasoline, and detergents. The area was used starting in 1955 for an unknown period.

Based on the investigation results, the 2006 preliminary assessment recommended AOC 176 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 176 under IRP Site 80. Under the site inspection, sampling will evaluate the other two discharge pipes for potential surface soil impacts.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 180 is a steel-lined pit used for oil changes and other vehicle maintenance. The site is located in the eastern portion of the main base just south of the Supersonic Naval Ordnance Research Track control and administration building. Potential wastes include oil and grease, hydraulic oil, antifreeze, gasoline, fuels, and solvents. Dates of waste disposal are unknown.

Based on the results of the previous investigations, the Navy recommended a screening-level risk assessment to evaluate whether the contaminants of interest pose a potential risk to human health or the environment. The Navy also concluded that contamination associated with this site does not appear to represent a significant release that requires further characterization. Additional site inspections are being conducting by the Navy for AOC 180 under IRP Site 80.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 200 is an elementary school located at the northern end of the NAWS China Lake housing area, built in 1952 and still in use today. Dust suppression during building construction is believed to have involved oils, possibly containing polychlorinated biphenyls. The site was included in a 2006 preliminary assessment for housing areas and schools. The preliminary assessment investigated the potential use of polychlorinated biphenyl-containing oil and routine application of pesticides but did not address other constituents of concern such as lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons.

Based on the results of the previous investigations, the preliminary assessment recommended AOC 200 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 200 under IRP Site 80. Under the site inspection, a surface survey will document areas of potential lead-based paint debris at the active and inactive housing buildings. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead to evaluate whether lead-based paint from the buildings potentially impacted the surficial soils. Four soil samples will also be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents were present in the waste oils used for dust suppression and potentially impacted the surficial soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 201 was an elementary school located within the old housing area in the central portion of the main base at NAWS China Lake. The school was built in 1952 and was abandoned before investigations were conducted. Potential use of polychlorinated biphenyl-containing oil in dust suppression during building construction and routine application of pesticides were investigated as part of the preliminary assessment in 1999 for the housing areas and schools. No samples were analyzed for other constituents that may be of potential concern, including lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons. The school was subsequently demolished, and the area restored to native desert.

The 2006 preliminary assessment recommended AOC 201 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 201 under IRP Site 80. Under the site inspection, a surface survey will document areas of potential lead-based paint debris at the active and inactive housing buildings that may have impacted the surficial soils. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead. Three soil samples will also be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents were present in the waste oils used for dust suppression and potentially impacted the surficial soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 202 was an elementary school located within the old housing area near the southwestern corner of the main base at NAWS China Lake. The school was built in 1952 and was closing when investigations were conducted. The site was included in a 2000 preliminary assessment for housing areas and schools. It included investigating the potential use of polychlorinated biphenyl containing oil for dust suppression and routine application of pesticides but did not address other constituents of concern such as lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons. The school was subsequently demolished, and the area restored to native desert.

The preliminary assessment recommended AOC 202 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 202 under IRP Site 80. Under the site inspection, a surface survey will be conducted to document areas of potential lead-based paint debris at the active and inactive housing buildings that may have impacted the surficial soils. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead. Three soil samples will also be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents were present in the waste oils used for dust suppression and potentially impacted the surficial soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 203 is a junior high school located in the central portion of the main base at NAWS China Lake. The school was built in 1952 and is still active. The site was included in a 2000 preliminary assessment for housing areas and schools. It investigated the potential use of polychlorinated biphenyl containing oil for dust suppression and routine application of pesticides but did not address other constituents of concern such as lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons.

The preliminary assessment recommended AOC 203 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 203 under IRP Site 80, including a surface survey that will document areas of potential lead-based paint debris at the active and inactive housing buildings that may have impacted the surficial soils. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead. Four soil samples will also be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents were present in the waste oils used for dust suppression and potentially impacted the surficial soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 205 is an elementary school located in what was a base housing area near the southern boundary of the installation. The area is now part of the City of Ridgecrest. The school was built in 1963 and is still active. The site was included in a 2000 preliminary assessment for housing areas and schools that included investigating the potential use of polychlorinated biphenyl-containing oil for dust suppression and routine application of pesticides but did not address other constituents of concern such as lead, polycyclic aromatic hydrocarbons, and total petroleum hydrocarbons.

The preliminary assessment recommended AOC 205 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 205 under IRP Site 80 that includes a surface survey that will document areas of potential lead-based paint debris at the active and inactive housing buildings that may have impacted the surficial soils. If areas of paint debris are identified, up to four surface soil samples will be collected for analysis of lead. Three soil samples will also be collected and analyzed for total petroleum hydrocarbons and polycyclic aromatic hydrocarbon compounds to evaluate whether these constituents were present in the waste oils used for dust suppression and potentially impacted the surficial soils.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 207 is located just outside the southern base fence and consists of multiple concrete building slabs that were used as a vehicle maintenance area and fueling station from 1947 to 1954. A potential vehicle maintenance pit and fuel pump pad were observed at the southeastern corner of the site. The site reconnaissance also identified an area of stained soil at the western portion of the site. Potential wastes include asbestos, antifreeze, fuels, oil and grease, metal scrap, solvents, waste oil, hydraulic oil, and wood scrap.

The 2006 preliminary assessment recommended a screening-level risk assessment to evaluate whether the contaminants of interest pose a potential risk to human health or the environment. The assessment further recommended AOC 207 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 207 under IRP Site 80. Samples will be collected under the site inspection to assess the extent of metals above soil screening levels at the stained area and former oil pit, evaluate the potential gas pump pad for soil impacts, and analyze samples for polycyclic aromatic hydrocarbon impacts.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 208 is located in the southern portion of the base just northwest of the Sandquist Gate and consists of a trailer court that was in operation from 1949 until 1954. During a site reconnaissance in December 2000, several concrete pads and a debris area containing paint and solvent cans, 55-gallon drums, construction debris, and rusted hardware were observed at the eastern end of the site. An area of stained soil was also identified. Potential wastes include wood scrap, waste oil, metal scrap, paints and thinners, solvents, heating oil, fuels, and grease.

The 2006 preliminary assessment recommended a screening-level risk assessment to evaluate whether the contaminants of interest pose a potential risk to human health or the environment. The assessment further recommended AOC 208 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 208 under IRP Site 80. Samples will be collected under the site inspection to supplement existing surface soil data to assess the extent of metals above soil screening levels, to evaluate background arsenic concentrations, assess whether detected arsenic concentrations are related to background, and to evaluate the debris pile for potential soil impacts.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 212 is located adjacent to the traffic circle near the main gate. The site consists of a building constructed in 1945 and was used until the early 1950s. It was initially used as an equipment building, later for elementary school offices, and then as a Girl Scout Hut. The site was also a former photographic material laboratory. Archived photographs showed stained soil, gas pumps, vehicle maintenance, service, and storage, suggesting past use as a vehicle fueling and service station. Potential wastes included oil and grease, solvents, waste oil, fuels, photo-processing chemicals, and metals.

The 2006 preliminary assessment recommended AOC 212 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 212 under IRP Site 80. Samples will be collected under the site inspection to supplement existing surface soil data.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 213 is a large construction camp used to house construction workers from 1944 to 1950. The site is located in the southern portion of the base just northwest of the Sandquist Gate. It is adjacent to a vehicle maintenance and repair area, AOC 163, and an old trailer park area, AOC 208. Potential wastes include wood scrap, waste oil, metal scrap, paints and thinners, solvents, heating oil, fuels, grease, pesticides, and construction debris.

The 2006 preliminary assessment recommended a screening-level risk assessment to evaluate whether the contaminants of interest pose a potential risk to human health or the environment. Based on the data collected, which indicated that numerous compounds were released, the preliminary assessment recommended AOC 213 as a medium priority for further investigation. The Navy is conducting additional site inspections for AOC 212 under IRP Site 80. Samples will be collected under the site inspection to assess the extent of pesticides and dioxins and furans in soil at areas where historical samples exceeded screening levels and assess areas of debris where samples have not been collected.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 217 is located near the southern boundary of the main base, along Highway 178 in Salt Wells Valley. The site is a 20-acre construction camp used to stage equipment during construction in the mid- to late 1940s. Aside from staging equipment, the facility housed vehicle maintenance buildings, a gas station, a paint shop, and other miscellaneous buildings. Potential wastes include wood scrap, waste oil, metal scrap, solvents, oil and grease, construction debris, fuels, gasoline, asbestos, industrial waste, and hydraulic oil.

The 2006 preliminary assessment recommended AOC 217 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 217 under IRP Site 80. Samples will be collected under the site inspection to evaluate asbestos impacts and assess AOC features that were not previously assessed such as the oil pit and metal debris area, and to evaluate potential soil impacts at drainage areas.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020 with no reported results yet available.

AOC 220 is adjacent to the traffic circle near the main gate. The site is the location of a former museum where miscellaneous chemicals and photographic chemicals were used and discarded in sinks from 1945 to the early 1950s. The building was used until 1973. Aerial photos indicated stained soils and probable use of chemical materials. The building was demolished in March 1999. Potential wastes include photographic chemicals, oil, grease, laboratory chemicals, and metals.

The 2006 preliminary assessment recommended AOC 217 as a low priority for further investigation. The Navy is conducting additional site inspections for AOC 217 under IRP Site 80. No data gaps have been identified, so additional sampling at AOC 220 was not recommended.

AOC 220 will be recommended for no further action status after the screening-level ecological and human health risk assessments have been completed using existing historical analytical data.

AOC 221 is located in the southern portion of the base, just north of the Sandquist Gate. The site consists of a former open trench, approximately 10,000 feet long, that was excavated in April 1952 for application of the pesticide chlordane to minimize migration of insects. The trench was subsequently backfilled. Evidence of the chlordane ditch still exists as a linear depression in the soil north of the old trailer court, AOC 208. Potential wastes include insecticides and pesticides.

Based on the data collected and the portions of the trench that were destroyed, the 2006 preliminary assessment recommended that AOC 221 be considered a low priority for future work. The Navy is conducting additional site inspections for AOC 221 under IRP Site 80. Samples will be collected under the site inspection to evaluate surface soils for pesticides and for risk assessment, and additional subsurface soil samples will be collected along the eastern portions of the trench, if located, that were not identified during the prior investigation. Additionally, a data gaps investigation is planned after the site inspection and before remedial alternatives are evaluated. A topographic mapping survey will be conducted at AOC 221 to aid in characterizing the site. Soil samples will be collected to evaluate migration and potential infiltration away from the disposal areas and in areas of burning and staining south of the disposal area.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned to begin in 2020, and the data gaps work plan and fieldwork were anticipated in fall 2020. After data from the site inspection and data gaps investigation become available, the Navy and regulatory agencies will establish the path forward for AOC 221.

AOC 227 is located near the western boundary of the main base in Baker Range. AOC 227 consists of an abandoned well site that is not associated with any structures in the area. It is believed that the Navy construction battalion may have installed the well as a practice drinking water supply well. Potential wastes and dates of waste disposal, if any, are unknown.

The 2006 preliminary assessment recommended no further action with decommissioning or sealing of the well. Because AOC 227 is not affiliated with a CERCLA release, the Navy will not be undertaking a site inspection and will be removing the AOC from the CERCLA program.

AOC 229 is located in the western portion of the main base, as part of Charlie Range. AOC 229 is a 5-acre compound used to store construction materials from the 1940s to the 1960s. Archived photos indicate that 55-gallon drums were stored in the area. Potential wastes include construction debris, electronic equipment, metals, industrial waste, target debris, metal scrap, wood scrap, and asbestos.

The 2006 preliminary assessment recommended AOC 229 as a medium priority for further investigation. The Navy is conducting additional site inspections for AOC 229 under IRP Site 80. Under the site inspection, surface soil samples at AOC 229 will be collected to supplement existing surface soil data. Soil samples will also be collected for asbestos analysis where asbestos-containing materials were identified and at AOC features that were not previously assessed, such as burn and debris areas. Additional soil samples will be collected for analysis of metals outside of the AOC boundary to assess whether detected metals concentrations within the AOC are within background ranges. In addition, one groundwater sample will be collected at the southern burn area to assess the presence or absence of dioxins and furans in groundwater.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 230 was reassigned to the IRP in 2018. The site is now known as IRP Site 83.

AOC 231 is located in the western portion of the main base, as part of Charlie Range. The site is the result of potential fuel spills from an aboveground storage tank operated from 1975 to 1979. No tank or significant areas of stained soil were observed during a site reconnaissance in December 2000. Potential wastes include gasoline, fuels, and solvents.

The 2006 preliminary assessment recommended a screening-level risk assessment to evaluate whether the contaminants of interest pose a potential risk to human health or the environment. It recommended AOC 231 as a medium priority for further investigation. The Navy is conducting additional site inspections for AOC 231 under IRP Site 80. Under the site inspection, surface soil samples at AOC 231 will be collected to delineate the extent of total petroleum hydrocarbons and polycyclic aromatic hydrocarbons above soil screening levels near the previous sample location and to collect background data for metals in soil outside the AOC boundary to assess whether detected metals within the AOC are within background ranges.

The results of the site inspection will indicate whether immediate, investigative, or no further action is required. The field activities were planned for 2020, with no reported results yet available.

AOC 232 is located in the western portion of the main base, as part of Charlie Range. The site includes an existing well possibly used for disposal of waste from range operations. Potential wastes and dates of disposal are unknown.

The 2006 preliminary assessment recommended a screening-level risk assessment and sealing the well casing. It further recommended AOC 232 as a low priority for future work. The Navy is conducting additional site inspections for AOC 232 under IRP Site 80. No data gaps have been identified, so additional sampling under the site inspection was not recommended.

AOC 232 will be recommended for no further action status after the screening-level ecological and human health risk assessments have been completed using existing historical analytical data.

AOC 235 was reassigned to the IRP after a 2016 site inspection that included the site. AOC 235 is now known as IRP Site 84.

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