Naval Weapons Station Seal Beach

IRP Site 7 is the former station landfill located near the southern boundary of the station and at the eastern boundary of the Seal Beach National Wildlife Refuge. The site consists of six known debris areas covering approximately 33 acres. From the mid-1950s to 1973, trash, debris, and other wastes such as solvents, transformer oil, lubricants, paint sludge, asbestos, photo solutions, and mercury were disposed of at the landfill. Most wastes were reportedly paints in mostly empty, small containers, petroleum products, various solvents, used rags, batteries, asbestos, and inert construction debris.

Potential chemicals of concern identified during historical investigations included low levels of volatile organic compounds, semi-volatile organic compounds, polychlorinated biphenyls, pesticides, and cyanide in soils, and low levels and infrequent detections of volatile organic compounds, semi-volatile organic compounds, pesticides, metals, asbestos, and cyanide in shallow groundwater. Based on collected data, there was a minimal risk to human and ecological receptors and a no action interim record of decision was recommended for soil.

A removal action was conducted in 2004 to repair the existing landfill soil cover and ensure a minimum of 2 feet of soil over the buried waste, thus preventing direct contact with buried waste and eliminating the potential migration of contamination through windblown dust, infiltrations, and surface runoff. Groundwater monitoring for pesticides, cyanide, and other metals was also conducted. Based on results, the Water Quality Control Board concurred in 2007 with the Navy’s recommendation that groundwater monitoring be discontinued.

A 2017 annual post-closure inspection and maintenance report documented that the landfill cover at IRP Site 7 continued to provide adequate drainage while minimizing erosion and isolating buried waste from the surface. Routine landfill soil cover inspections and maintenance continue to be conducted at the site, ensuring that soil cover vegetation and erosion control are maintained.

IRP Site 22 is a commercial oil production facility on a man-made island within the Seal Beach National Wildlife Refuge. Oil production waste-holding impoundments were in use at the site in 1954. Wastes confined there reportedly included drilling muds, drill cuttings, and oily wastes.

Investigations indicated that soils contained elevated total petroleum hydrocarbon levels. Based on results of a 1995 study, a removal action was recommended to clean up contaminated wastes. Additional sampling conducted in 2002 by Breitburn Energy Company (Breitburn), the party responsible for operations at the facility, further defined the nature and extent of contamination and potential impacts to ecological receptors. Breitburn subsequently developed and implemented a plan to deter wildlife from visiting or inhabiting the site until cleanup could be conducted.

Action was taken in 2005 to mitigate an oil seep detected in the water on the northeast side of the island. Samples of product, water, and soil collected by the Navy and BreitBurn confirmed a release of petroleum hydrocarbons. BreitBurn operations personnel trenched beneath natural gas lines, the source of a suspected leak, adjacent to the area of impacted soil and wetlands and performed repairs and replacement of some lines. The Regional Water Quality Control Board approved in 2005 the installation of a barrier trench to mitigate potential migration of residual chemical compounds in soil into the wetlands bank and adjacent tidal marsh area, and the barrier was successfully installed where the pipeline leak had occurred.

Between 2006 and 2010, the Regional Water Quality Control Board requested information, additional assessment of the site, and monitoring of the release area. The Navy, Seal Beach Wildlife Refuge staff, and the Regional Water Quality Control Board concurred in 2010 that further assessment in the tidal zone and release area on the slope above the tidal zone and below the barrier trench would significantly impact sensitive re-established vegetation habitat in the adjacent wetlands and impacted areas. Based on the need to protect re-established sensitive habitat, a no further remedial action determination for soil was approved by the Regional Water Quality Control Board.

IRP Site 70 is near the western boundary of the station, south of Westminster Avenue. The facility was built for the design and manufacture of the second stage of the Saturn V launch vehicle for the Apollo moon rocket program and operated by North American Aviation between 1962 and 1973 under contract to the National Aeronautics and Space Administration. Chlorinated solvents, primarily trichloroethylene, used in the manufacturing process were released to the environment during the period, resulting in contamination of the groundwater at the site.

A 1993 preliminary assessment identified hexavalent chromium, trichloroethene, phenolic compounds, trichlorotrifluorethane, and heavy metals as chemicals of potential concern in ten areas of concern. A 1998 closeout report documents the decommissioning of the process piping system and facilities.

From 1996 to 1998, the nature and extent of contamination in soil and groundwater were delineated. Findings from the data supported a decision of no further action for soil.

The 2006 record of decision and remedial action plan document the Navy’s selection of in-situ enhanced bioremediation, monitored natural attenuation, and land use controls to address impacts to groundwater. A 2011 five-year review reported that all immediate threats were addressed, and long-term protectiveness of the site remedy was being maintained by continuing monitoring of remedy performance and compliance with land use controls that restrict the use of, or limit access to, real property, and include institutional control requirements such as deed restrictions, restrictive covenants, or permitting requirements.

The remedy has been in operation since 2008 and has substantially reduced contaminant concentrations, although monitoring data suggest that the system is not performing as well as expected. A soil and groundwater investigation was conducted to better understand site conditions, further assess the effectiveness of the remedial action, and make recommendations for optimizing the in-situ bioremediation system. A March 2022 five-year review stated the remedy has been generally effective at reducing groundwater contamination and is expected to be protective of human health and the environment. A draft 2022 annual performance monitoring report for enhanced in-situ bioremediation received no comments from the Regional Water Quality Control Board in January 2023. Additional system optimization work including new monitoring wells and bioremediation enhancement will be implemented in 2024.

IRP Site 74 is near the middle of the station, off Case Road. The site was constructed in the late 1960s and was an active skeet and trap shooting range for approximately 25 years. The range was closed in the early 1990s because of concern for waterfowl and other wildlife ingesting spent shot composed of antimony alloys and lead. Stray bullets from the nearby small-arms range are another likely source of the lead contamination. Polycyclic aromatic hydrocarbon contamination is likely from clay and coal tar trap targets, the only known source at the site.

An investigation was performed in 2002 to provide data for evaluating ecological and human health risks. Lead and antimony were detected in soil and sediment samples, and polycyclic aromatic hydrocarbons were also detected in soil samples at concentrations posing potential risks.

A 2022 draft final revised feasibility study selected remediation goals based on protection of the most sensitive ecological receptor at IRP Site 74, reducing risk for all ecological receptors, and addressing unacceptable risks from antimony, polycyclic aromatic hydrocarbon, and lead shot in soil and sediment. Pre- and post-biological monitoring, removal of contaminated soil in the upland area, amphibious excavation of sediment in the wetland area, and transport and disposal at an off-site treatment facility comprise the recommended alternative to address the contaminated soil and sediment. The regulatory agencies concurred with the feasibility study which was finalized in December 2022. An internal draft proposed plan was prepared and is currently in Navy review.

IRP Site 75 is near the southeastern boundary of the station. A report in 2004 of chlorinated volatile organic compounds in an agricultural well installed in 1926 led to establishment of the IRP site.

In September 2004, the Orange County Water District collected a groundwater sample from the well and analyzed it for volatile organic compounds. The chlorinated hydrocarbons tetrachloroethene, trichloroethene, 1,1-dichloroethene, 1,1,1-trichloroethane, and 1,1-dichloroethane were identified in the sample. As a result, the Navy destroyed the well in November 2006 and filled it with grout to prevent potential exposure to human and ecological receptors. No evidence has been identified that indicates the storage or use of chlorinated solvents by the Navy in the vicinity of agricultural well KAYO-SB.

Site reconnaissance and sampling were conducted in early 2011. Analytical results indicated that shallow and deeper aquifer groundwater in the vicinity of the well was impacted with concentrations of volatile organic compounds above maximum contaminant levels. Studies completed in 2012 and 2016 to 2017 indicated that dissolved volatile organic compounds identified at IRP Site 75 likely originated from off-site, up-gradient source locations in the industrial developments to the northeast and east of the station. The levels of volatile organic compounds in the shallow unit groundwater, near a residential neighborhood, indicate the need for further investigation of the release, by the property owner, to evaluate for potential risk to short-term and long-term occupants along the path of the contaminant plume.

The Regional Water Quality Board is currently working with potential private industrial sources to ensure that additional contamination does not migrate onto Navy property. Additional groundwater monitoring by the Navy at IRP Site 75 may be planned in coordination with the Regional Water Quality Control Board if further characterization of the site area becomes necessary. Decisions on any future environmental investigations and cleanup will be made by the regulatory agencies once a determination of the off-site responsible party has been made.

Back to IRP Sites Map

IRP Site 1 is a former wastewater settling pond near the intersection of 6th Street and Case Road. The site operated from 1945 until 1971 and the pond contained chromic acid, alkali, acid, and metals-contaminated wastewater from metal cleaning operations in a nearby building that has since been demolished.

A 1989 investigation report identified elevated concentrations of chromium in a low-lying area bounded by railroad tracks and 6th and Case Streets, and a total petroleum hydrocarbons concentration in one sample at the Regional Water Quality Control Board cleanup level. Excavation and off-site disposal of primarily metals-contaminated soil was recommended.

A removal action was conducted at IRP Site 1 from June to November 1999. The removal action closure report recommended no further response action required in December 1999. The no further action remedy was documented in the 2002 record of decision for IR Sites 1 and 19 and in an April 2002 Department of Toxic Substances Control concurrence letter.

IRP Site 2 is the location of three former unlined wastewater evaporating ponds south of Westminster Avenue at the end of 8th Street. The ponds contained approximately 90,000 pounds of ammonium picrate residue, known as Explosive D, which was mixed with water and received as liquid waste from the projectile demilitarization operations conducted in several former production buildings at the site from 1945 until 1971. The Explosive D residue was excavated from the evaporation ponds after they were allowed to dry and disposed of offsite. Based on site investigation and removal action, no further action was recommended for the site, and the Navy subsequently reported the site as no further response action planned. In a February 2000 letter, the Department of Toxic Substances Control concurred with the 1999 report’s recommendation of no further action for the site.

IRP Site 3 is a former cleaning water settling pond southeast of Westminster Avenue at the end of 8th Street. Wastewater contaminated with residual Explosive D dust was discharged from floor drains in the building through a pipe from 1944 to the early 1950s, leaving approximately 520 pounds of ammonium picrate, known as Explosive D, in the pond after it was allowed to dry. The Explosive D residue was excavated from the evaporation pond and disposed of offsite. Following a site investigation and subsequent removal action, no further action was recommended, and the Navy subsequently reported the site as no further response action planned. In a February 2000 letter, the Department of Toxic Substances Control concurred with the 1999 report’s recommendation of no further action for the site.

IRP Site 4 is known as Perimeter Road. From the mid-1960s until 1973, waste oils were used for dust suppression along Perimeter Road. Lead was reported in surface soil along the road, including the areas of potential concern at Perimeter Road South.

An investigation at the site recommended a removal action, and excavation and off-site disposal of lead-contaminated soil was conducted from December 2003 to April 2004. The Department of Toxic Substances Control concurred with the removal action closure report for soil in September 2004.

Groundwater monitoring was conducted to evaluate impacts to groundwater near IRP Sites 4, 5, 6, and 7. Based on the findings and recommendations in the 2005 groundwater monitoring report and the concurrence of the Regional Water Quality Control Board, IRP Site 4 was removed from the monitoring program. The status for groundwater at IRP Site 4 is no further response action planned. The Department of Toxic Substances Control concurred with no further action for groundwater in an October 2005 letter.

IRP Site 5 is the former clean fill disposal area and landfill, located southeast of the intersection of Kitts Highway and Bolsa Avenue, which was used for the disposal of construction debris and clean fill from 1943 until 1944. Contaminated soils at the disposal area and landfill also reportedly contained ordnance items and scrap metal.

Investigation in 1998 recommended a removal action for ordnance at the site. Excavation and off-site disposal of construction debris and contaminated soil or reuse and recycling of screened soil and concrete from the former clean fill disposal area were completed in 2002. Clearance of the ordnance material from sifted soil and other materials was verified. The Department of Toxic Substances Control approved the closure report for soil in 2003.

Groundwater monitoring was conducted in 2004 to evaluate whether groundwater had been impacted. Volatile organic compounds, polycyclic aromatic hydrocarbons, metals, anions, and ammonia were reported in groundwater samples, although most of these compounds and chemicals were at concentrations below screening values. Two additional years of monitoring were completed to assess potential impacts to groundwater. The Regional Water Quality Control Board concurred with no further action for groundwater in July 2007, and the status of IRP Site 5 is no further response action planned.

IRP Site 6, the Explosives Burning Ground, is a triangular area of approximately 15 acres in the southern section of the station that was used from 1945 until 1971 for the open burning of ordnance-contaminated wastes. The site contained several types of contaminants related to burned ordnance.

A 1993 investigation reported low concentrations of total petroleum hydrocarbons as gasoline in soil and groundwater, benzo(a)pyrene above the preliminary remediation goal level in one soil sample, and elevated levels of nitrate/nitrite-N in groundwater samples from one monitoring well. A 1993 screening ecological assessment identified antimony, arsenic, barium, cadmium, chromium, lead, mercury, and zinc as chemicals of potential ecological concern in soil and groundwater. A removal site evaluation was completed by 1998. Excavation and off-site disposal of surface soil was completed. Based on a removal action evaluation in 2000, the Department of Toxic Substances Control concurred with no further action for soil. By 2002, periodic groundwater sampling was underway. Based on the results of a 2005 groundwater monitoring report for IRP Site 6 and several nearby IRP sites and with the concurrence of the Regional Water Quality Control Board, IRP Site 6 was removed from the groundwater monitoring program. The Department of Toxic Substances Control concurred in an October 2005 letter. The site status is no further response action planned.

IRP Site 8, the former battery shop wastewater discharge line, was located just southwest of the corner of Industrial Road and Kitts Highway adjacent to the Seal Beach National Wildlife Refuge and was operational from 1945 until 1975. Reported wastes included neutralized battery acid and lead.

A 1993 investigation conducted to delineate the extent of lead contamination in soil recommended a removal action for lead-contaminated soils. No further response action was recommended for groundwater at the site. Excavation of 512 tons of lead-impacted soil over an area of 1,600 square feet and off-site disposal of the contaminated soil began in 1996, and soil replacement was subsequently completed in 1998.

A final closure report was prepared to document the removal action. The Department of Toxic Substances Control concurred with the removal action closure report in a June 1999 letter, and the Navy subsequently reported IRP Site 8 status as no further response action planned.

IRP Site 9 was a surface impoundment located approximately 500 feet northwest of the corner of Kitts Highway and Buoy Road. The area was in use for the disposal of sandblast grit generated from maintenance of naval buoys from the mid-1950s until the mid-1960s. The sandblast grit was contaminated with metals.

A June 1998 activity completion report documents that a removal action consisting of excavation and off-site disposal of metals-contaminated soil was completed in 1996 and that metals concentrations in remaining soils were below naturally occurring background values.

The Department of Toxic Substances Control concurred with the removal action closure report in an August 1998 letter, and the Navy subsequently reported IRP Site 9 status as no further response action planned.

IRP Site 10 was the location of an acid spill of unknown date in the marsh area of what later became the Seal Beach National Wildlife Refuge. Sampling and analysis results from a 1985 Navy Salt Marsh Pond study reported pH levels in the marsh lower than in surrounding areas and that metals concentrations were consistent with background metals concentrations.

Off-site disposal of acid-contaminated marsh materials was completed, and a site inspection report was prepared. No further action was recommended. The Department of Toxic Substances Control approved the site inspection report in an August 1995 letter. The Navy reported the site status in a 2002 base newsletter as no further response action planned.

IRP Site 11 is near the southeastern border of the station along Perimeter Road. The site was established in response to a 1983 fire within a storage trailer containing both organic and inorganic pesticides.

A 1990 report indicated that the semi-trailer and debris from the fire were removed and properly disposed of offsite in 1984 and that there were no concerns regarding current releases to the environment. No further action was recommended. The Department of Toxic Substances Control approved the site inspection report in an August 1995 letter, and the Navy subsequently reported the site status as no further response action planned.

IRP Site 12 is a former open burning ground located on a circular peninsula at the west end of NASA Road. The “island” was constructed from imported fill and rises 6 to 8 feet above the tidal salt marsh. It was used from 1968 until 1972 as a site for open burning of explosive wastes and for testing firefighting foams. Four trenches were excavated on NASA Island for ordnance disposal. A steel tank containing water, aqueous fire-fighting foam, and residual leaded gasoline reportedly drained into the trenches.

Based on the results of investigations conducted in the 1990s, a removal action at IRP Site 12, consisting of excavation and off-site disposal of burned waste was completed. No further action was recommended for groundwater. The Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the 2002 focused site inspection report recommending no further action for IRP Site 12, and the Navy subsequently reported the site status as no further response action planned.

IRP Site 13 is located along Kitts Highway south of Westminster Street. During the 1969 construction of the Orange County Sanitation District Pumping Station Number 3, an existing sewer main was broken at the corner of Seal Beach Boulevard and Westminster Avenue. Approximately 1,200,000 cubic feet of raw or primary treated sewage was diverted down gradient onto NWS Seal Beach property into a low-lying area southwest of the corner of Kitts Highway and Westminster Street. The sewage ponded and was allowed to evaporate and infiltrate into the soil. Removal of the raw sewage spill and affected surfaces was completed in 1969.

During investigations of IRP Site 13 in 1985 and 1992, metals were not detected above background levels in soil, but low concentrations of nitrate-N were detected. Additional soil samples collected in 2000 and analyzed for volatile and semi-volatile organic compounds detected low concentrations. Groundwater was also sampled and analyzed from three wells.

Based on the results from sampling, the Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the 2002 site inspection report recommending no further action for IRP Site 13. The Navy subsequently reported the site status as no further response action planned.

IRP Site 14 is located between Tank Site 229 and the Seal Beach National Wildlife Refuge adjacent to the southwest corner of Kitts Highway and Industrial Road. It was formerly Underground Storage Tank Site 14 and Underground Storage Tank 228. One 10,000-gallon capacity tank reportedly contained diesel from the mid-1940s to the mid-1960s for fueling a galley boiler at a nearby building. The other tank was 12,500 gallons in capacity and was associated with a fueling station and used for supplying leaded gasoline for automobiles. The site was placed under the IRP because petroleum contaminants at the site were found to be comingled with chlorinated solvents.

A 1985 study recommended no further action for the 10,000-gallon tank because there was no evidence of leakage. Near the fueling station, total petroleum hydrocarbons, volatile organic compounds, and organic lead with non-aqueous phase liquids were found in 1991 in one soil boring. Groundwater monitoring was initiated.

Orange County Water District and Stanford University conducted studies at the site under the oversight of the Navy from 1985 to 1997 investigating biodegradation of gasoline hydrocarbons by microorganisms. In-situ pilot systems were installed, operated, and monitored by researchers. The studies were concluded in 1998 and all associated monitoring and injection wells were abandoned in 1999.

A 1999 baseline survey found that subsurface soil at the site was clean and suitable for future residential land use. Groundwater samples collected from the five monitoring wells installed during the survey found the gasoline-related constituents total petroleum hydrocarbons and volatile organic compounds. Groundwater monitoring was conducted at the request of the Regional Water Quality Control Board. Results from sampling in 2002 indicated that natural attenuation of contamination was occurring.

In 2006, groundwater samples showed that concentrations of total petroleum hydrocarbons in monitoring wells along the boundary with the wildlife refuge were below the screening values and indicated that the plume was not migrating. Based on the 2005 ecological risk screening and the 2006 groundwater monitoring report findings, the Regional Water Quality Control Board approved the site for no further action related to underground storage tank releases at IRP Site 14 in a July 2008 letter. The Navy subsequently reported the site status as no further response action planned.

IRP Site 15 is located west of the southern boundary of the Seal Beach National Wildlife Refuge and is an area where approximately 1,000 gallons of diesel fuel spilled in October 1983 onto the east side of Anaheim Bay Road. Responders contained and disposed of the fuel and affected site media offsite.

A 1985 study recommended no further action at IRP Site 15 because of containment, cleanup, and dispersal at the time of the spill. A 1990 study also evaluated the site and recommended no further action because no significant contamination was found. In an August 1995 letter, the Department of Toxic Substances Control concurred, and the Navy subsequently reported the site status as no further response action planned.

IRP Site 16 was an unpaved area now inside and adjacent to the northern end of 7th Street Pond that was operational from 1944 until 1982. The site consisted of a depriming area, an explosives ordnance disposal and safety demonstration area, and a live ammunition finds area. Surface materials affected by wastes, which included fog oil, smokeless powder, black powder, and ordnance debris, were disposed of offsite.

Investigations were conducted in the 1990s. Based on results, no further action was recommended for soil, other than an ordnance survey. A focused site inspection was conducted in 2002. The Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the 2002 site inspection report recommending no further action IRP Site 16, and the Navy subsequently reported the site status as no further response action planned.

IRP Site 17 is a mercury spill area in a former laboratory building located off 4th Street, 600 feet north of the intersection with Missile Road. The spill occurred in 1970 on a concrete floor and responders contained and removed the mercury spill by first using a mercury vacuum, and then by wiping the floors with rags. A mercury disposal drum and the rags were disposed of at IRP Site 7, the Former Station Landfill.

A 1985 study which recommended that the concrete floor at IRP Site 17 be tested to verify that cleanup was complete. A 1990 follow-up study evaluated the area and recommended no further action. In an August 1995 letter, the Department of Toxic Substances Control concurred with the recommendation for no further action for the site. The Navy subsequently reported the site as no further response action planned.

IRP Site 18 is east of the Marshalling Yard, between Bolsa Avenue and Perimeter Road. The site was established in response to an inert construction debris pile created from the demolition of a station chapel. The rubble was stockpiled, removed, and disposed of offsite.

A 1985 study reported no evidence of hazardous waste disposal at IRP Site 18, and no potential threat to human health or to the environment. No further action was recommended, and the Department of Toxic Substances Control concurred in an August 1995 letter. The Navy subsequently reported the site as no further response action planned.

IRP Site 19 is located along Seal Beach Boulevard, north of the Pacific Coast Highway, and was a pit used from 1970 to the mid-1970s to dispose of all wastes generated by a nearby repair building. Unknown quantities of waste paint, lacquer thinner, solvents including trichloroethylene, and mineral oils were reportedly drained into this pit at least weekly. A sandblast grit disposal area was also identified just north of the pit. The pit area was closed and covered with soil in 1975 or 1976.

The disposal of trichloroethylene at IRP Site 19 and the potential for migration to the salt marsh led to a recommendation for further study. A 1988 site inspection found elevated levels of metals in groundwater and recommended a remedial investigation. The results of a 1995 human health and ecological risk assessment in the investigation report led to a finding that no further action was required for groundwater, although a removal action for metals-contaminated soil in the pit and sandblast grit disposal area was recommended.

A removal action consisting of excavation and off-site disposal of sandblast grit, debris, and soils primarily contaminated with heavy metals was completed in 1998. The Regional Water Quality Control Board concurred with the removal action closure report in June 1999, resulting in no further response action required at the site. The no further action remedy was documented in the 2002 record of decision for IR Sites 1 and 19.

IRP Site 20 is the location of a mercury spill area on the floors in a storage building near the intersection of Case Road and 5th Street. Vibration testing equipment reportedly leaked unknown quantities of mercury onto the concrete floor about once every two months between 1960 and 1967. Recoverable mercury was placed in jars and the remaining mercury was wiped up with rags and put in the trash.

A 1985 assessment recommended that the concrete floor at IRP Site 20 be tested to verify that cleanup was complete. In 1990, the site was investigated again, and a removal action was recommended. Decontamination of the floors was conducted in 1994. The Department of Toxic Substances Control concurred in a July 1995 letter with the recommendation in the removal action closure report for no further action, and the status of IRP Site 20 is no further response action planned.

IRP Site 21 was established in response to a waste pile known as the disposal berm approximately 150 feet north of the intersection of 4th Street and Missile Road, reportedly active from 1966 to 1974. Wastes from nearby chemical laboratory operations were poured onto the berm, including Freon®, waste oils, and black powder. The laboratory wastes applied to the disposal berm area were excavated and disposed of offsite.

A 1985 study first identified IRP Site 21 and recommended no further action because of the degradation and dissolution over time of chemicals of potential concern. An evaluation of the subsurface soils and groundwater was later recommended because of the potential for deeper migration of fluid contaminants.

A 1999 risk assessment recommended no further action. The Department of Toxic Substances Control concurred with the reported findings and recommendation for closure in a February 2000 letter. The Navy reported the status at IRP Site 21 as no further response action planned.

IRP Site 23 is the area just south of 7th Street Pond. Black powder was burned on the ground from 1964 to 1978 in this location formerly known as the Sample Explosive Demolition Area. The black powder and affected soil were removed.

A 1985 study recommended no further action at IRP Site 23 because of the frequency and small quantities of black powder burned. Another study was conducted in 1999 that included a risk assessment. The study report recommended no further action at IRP Site 23. The Department of Toxic Substances Control concurred with the reported findings and recommendation for no further action in a February 2000 letter. The Navy subsequently reported the site status as no further response action planned.

IRP Site 24 is a low-lying area 200 feet southeast of the southern end of 7th Street Pond. From 1950 to 1960, experimental propellant-contaminated wastewater from nearby testing was drained into the unlined Quench Water Disposal Area. Approximately 26,000 gallons of the quenching water was disposed of at the site, posing a potential threat from migration to the salt marsh.

A 1985 study recommended a confirmation study at IRP Site 24 because of the quantity of wastewater and the potential for migration to the salt marsh. A 1990 investigation found no indication of impact from past disposal practices at the site. Explosives used in the experimental propellants were not detected and only low levels of lead and fluoride, both associated with propellant compounds, were detected at the site. The remedial investigation recommended no further action and the Navy subsequently reported the site status as no further response action planned.

IRP Site 25 was an area near 7th Street south of Westminster Street that included a structure used from 1972 to 1976 for quality evaluation tests of firefighting foams. The building reportedly consisted of four 12-foot walls surrounding an open courtyard that contained an open 10-foot diameter, 3-foot-deep steel tank in which a gasoline and water mixture was ignited and then extinguished using firefighting foam. Remaining wastewater was drained from the tank and discharged to the soils of the adjacent courtyard. The wastewater contained dilute residues from the gasoline, extinguishing foam, and combustion by-products. A removal of the combustion and fire suppressant contaminants was conducted.

A 1985 study first identified IRP Site 25 and recommended no further action. A follow-up study in 1990 recommended that further investigation be conducted to confirm contaminant biodegradability and to assess potential contaminant transport in soil and groundwater. A 1993 site inspection to further assess contamination in the building courtyard area and a screening ecological risk assessment both indicated no further work was recommended.

Based on results from a 2002 focused site inspection, the Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the recommendation of no further action, and the Navy subsequently reported the status at IRP Site 25 as no further response action planned.

IRP Site 35 is less than one-quarter mile south of Bolsa Avenue, about 2.5 miles west of Bolsa Chica Road. The site was established in response to historic records showing the potential for waste carrying drums within the Drum Storage Yard. The drum contents were unknown, although otto fuel, paints, and solvents were the suspected contents.

The drums were transported and disposed of at a permitted landfill. A 1998 site inspection recommended no further action. The Department of Toxic Substances Control concurred in February 2000 with the recommendation, and the Navy subsequently reported the site status as no further response action planned.

IRP Site 36 is a baffled concrete basin south of the intersection of Westminster Street and 9th Street. Explosive-D contaminated washwater generated in a production building was diverted through a drain in the bottom of a steam-out tank into the concrete settling tank following the final washout of projectile casings. Once through the settling tank, the wastewater was diverted through a concrete trench to a series of three evaporation ponds at IRP Site 2. An estimated 13 tons of wastewater with ammonium picrate, known as Explosive D, was discharged from the building through the primary settling tank from 1945 to 1971. Removal of Explosive D from the primary settling tank was conducted.

Formerly identified as SWMU 6, the site was included in soil and groundwater investigations and a screening ecological risk assessment conducted in the 1980s. A 1990 follow-up study recommended no further investigation because no releases were reported, the tank was periodically dredged, and there was no evidence of the non-reactive hydrated salt forms of ammonium picrate. The Department of Toxic Substances control agreed in an April 1998 letter with the no further action recommendation. A 1999 risk assessment also recommended no further action and the Navy subsequently reported the site status as no further response action planned.

IRP Site 37 was established in response to wastes within the Bolsa Avenue Storage Yard, located about 2 miles west of Bolsa Chica Road. The waste types within the storage yard included transformers, capacitors, and waste oil drums. The wastes were profiled, transported, and disposed offsite at a permitted landfill.

The Bolsa Avenue Storage Yard, also known as the Public Works Storage Yard, was earlier described as SWMU 7. Investigations, including surface sampling and analysis, were conducted in the 1990s. Based on results of a focused site inspection in 2002, the Regional Water Quality Control Board (July 2002) and the Department of Toxic Substances Control (April 2002) concurred with the recommendation of no further action for IRP Site 37. The Navy subsequently reported the site status as no further response action planned.

IRP Site 38, the X-Ray Shop Leach Field, consisted of a drainage ditch approximately 100 yards long by 3 feet wide located south of a former X-ray facility and parallel to and immediately east of Case Road, 200 feet north of the intersection with Bolsa Road. The site received wastewater discharges from 1956 to 1968 generated by x-ray developing activities. Waste photo processing chemical fluids including Hypoclear and developer were allowed to percolate into the subsurface. Soil from the X‐ray Shop Leach Field affected by waste photo processing chemicals was excavated, transported, and disposed of off-site.

Earlier described as SWMU 19, investigations in the 1990s recommended sampling in the drainage ditch because the x-ray shop used a black and white developing process that produced silver, phenolic alkaline, sodium sulfite, potassium bromide, and possibly cyanides as waste. A risk assessment in 1999 recommended further sampling. Based on results of a 2002 focused site inspection , the Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the no further action recommendation for IRP Site 38. The Navy subsequently reported the site status as no further response action planned.

IRP Site 39 is in the northern part of the base, approximately 600 feet north of the corner of HE Road and 20th Street. The site was reportedly the location of two 5,000-gallon underground storage tanks. From 1958 through the mid-1970s, the tanks were used in a Talos missile fueling and defueling operation performed at a fueling station on a concrete pad. One tank contained the liquid rocket propellant Dimer fuel used for missile fueling, while the second tank received the waste fuel from the defueling operation.

The Waste Missile Fuel Tanks were first described in the 1985 study and later as SWMUs 26 through 28. A 1990 study recommended a geophysical survey to confirm the presence of the tanks and, if located, closure under the Navy underground storage tank removal program. The site was moved out of the IRP and into the underground storage tank removal program. The tanks were removed, and hydrocarbons were detected in soils immediately above groundwater. Excavation of contaminated soils and groundwater monitoring were recommended. Based on the 1998 focused site inspection, closure was recommended, and the Department of Toxic Substances Control concurred. The Navy now reports the site as closed.

IRP Site 40 is in the southwestern part of the station, approximately 0.6 miles west of the Seal Beach National Wildlife Refuge. It includes an inactive locomotive repair shop, and a partially paved gravel area north of and adjacent to the building. Oil and solvents were used during locomotive maintenance activities conducted from the mid-1940s to 1978. A concrete pit inside the building that discharged through a drainpipe into the gravel area provided a collection point for oil and solvents spilled during locomotive maintenance activities until the pipe was plugged in 1978.

The Concrete Pit/Gravel Area was first described in a 1985 study as the Railroad Equipment Maintenance Shop, inclusive of the concrete pit and a gravel area on the north side of the building. It was earlier identified as SWMU 49.

Studies were conducted in the 1990s to evaluate soil and groundwater. A 1995 study confirmed the presence of a plume of volatile organic compounds in groundwater exceeding state and federal maximum contaminant levels. Based on risk assessment results, no further action was recommended for soil and further action was recommended for groundwater to address volatile organic compounds.

A long-term groundwater monitoring program was implemented at the site in 2000. The Navy performed a pilot study to address volatile organic compounds at the site using in-situ treatment with enhanced biodegradation through injection of sodium lactate and a bacterial culture.

The 2004 record of decision/remedial action plan selected enhanced in-situ bioremediation, monitored natural attenuation, and land-use controls as the remedy for groundwater at IRP Site 40. Injection wells, groundwater monitoring wells, and vapor monitoring wells were installed in 2005 and bioremediation was initiated.

A 2017 site closure report evaluated remediation and monitoring activities at IRP Site 40 and recommended closure with no further action, with the anticipated site use to remain industrial and under the Navy’s control. In 2017, the Department of Toxic Substances Control and the Regional Water Quality Control Board concurred with the site closure report. The Navy subsequently reported the site status as no further response action planned.

IRP Site 41 is located near the corner of Case Road and Bolsa Street and is a 4,000-gallon underground storage tank close to a maintenance facility. Waste Otto fuel and Otto fuel-contaminated solvents from maintenance were typically stored in drums at the facility. From 1982 to 1983, the waste liquids were reportedly stored in the tank and periodically pumped out for off-site disposal. The facility ceased use of the tank because of its failure to comply with special handling, transfer, and storage requirements for Otto fuel.

Formerly identified as SWMU 16, previous studies at IRP Site 41 recommended a geophysical survey to confirm the presence of the tank and, if located, closure under the Navy underground storage tank removal program. The Department of Toxic Substances Control reviewed and approved the recommendations for Site 41 in the 1995 site inspection report. The site was moved out of the IRP and was closed under the underground storage tank program. The Navy subsequently reported the status at IRP Site 41 as no further response action planned.

IRP Site 42, the Auto Shop Former Sump/Waste Oil Underground Storage Tank, was near the corner of Net Road and Kitts Highway. A portion of the site lies within the Seal Beach National Wildlife Refuge. The site included an auto maintenance shop and location of the former sump and a battery acid neutralization tank, a wash area, waste oil storage, an oil-water separator, and a stormwater collection basin drainpipe that discharged into the National Wildlife Refuge.

From the 1950s to 1972, waste oils from the auto shop were stored in an underground storage tank that was periodically pumped out by an off-site contractor. The 1,500-gallon oil-water separator was in operation from 1978 to 2004 and separated floatable oil from wastewater. The clarified wastewater from the oil-water separator was discharged to a sanitary sewer pipe.

A 1993 study recommended investigation of lead contamination in soils from site operations and no further response action for groundwater. A 2002 report confirmed that contamination from the vehicle maintenance activities at the site led to discharges from the stormwater collection basin through a drainpipe to the National Wildlife Refuge, depositing metals in soil in a small area around the drain outfall. Copper was the only metal exceeding the upper limit background value for the installation. The report recommended a removal action to reduce the risk to ecological receptors from copper concentrations in soil.

A removal action was completed in 2006 and the Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the 2007 site closeout report that the site be closed, and the status of IRP Site 42 is no further response action planned.

IRP Site 43, the Battery Shop Sump, was in a battery shop on Kitts Highway between Bolsa Avenue and the Pacific Coast Highway. From 1945 to 1978, waste batteries were drained, and waste sulphuric acid neutralized with sodium bicarbonate was poured into a concrete sump in the battery shop. Since at least 1970, a cold dip parts solvent was used to clean engine parts and to regularly wash down the floors, including periodic spills of waste oil. The cold dip solvent was also reportedly washed into the sump and drains in the shop. All floor drains reportedly discharged to the sanitary sewer. The facility also included the auto maintenance shop and former sump and was adjacent to an oil-water separator and a drainpipe that discharged into the National Wildlife Refuge. Removal of neutralized battery acid and cold dip parts cleaner fluids was conducted with off-site disposal.

The battery shop sump at IRP Site 43, and the heavy equipment and automotive shop floor drains in the facility were first described as SWMUs 35, 37, and 38. In 1990, verification of the destination of the drains and the integrity of the drain lines was recommended because they were potentially connected either to the sewer or an outfall in the tidal salt marsh southeast of the building.

Based on a 1998 site inspection, the Department of Toxic Substances control agreed in a 1998 letter with the recommendation of no further action. A 1999 risk assessment also recommended no further response action for soils or groundwater at IRP Site 43, and the Navy subsequently reported the status at IRP Site 43 as no further response action planned.

IRP Site 44, the Former Waste Otto Fuel Drum Storage Yard is located near the corner of Case Road and Bolsa Avenue and was used from the mid-1940s until the late 1970s to store drums of waste Otto fuel; cleaning solvent; and waste lead battery electrolyte.

The sites were first described as SWMUs 14 and 15, respectively. No further investigation was recommended for IRP Site 44 because no releases were reported. Although the IRP Site 45 drain had been sealed, determination of the drain outlet’s location was recommended because it had at one time reportedly emptied into the tidal marsh.

A 1993 site inspection evaluated any further need for investigation or removal action at IRP Site 44/45. No further response action for soil and an investigation to assess groundwater contamination was recommended. A 1990 to 1993 screening ecological risk assessment recommended additional investigation of high concentrations of zinc and nickel in groundwater.

In 2000, nickel and zinc, likely from storage and recycling of metals in the building, and specific polycyclic aromatic hydrocarbons were found above background levels in most groundwater samples and in some sediment samples from a drainage ditch that discharges stormwater from the site into the National Wildlife Refuge. The 2002 human health risk assessment found that the likelihood of humans coming into contact with sediment was minimal and the groundwater pathway was incomplete since the water is saline and not potable. A 2002 focused site inspection recommended removing sediment with nickel and zinc concentrations above background levels because of possible risks to aquatic receptors.

A 2006 removal action was conducted at IRP Site 44/45 consisting of excavation and off-site disposal of metals-contaminated sediment at the former waste Otto fuel drum storage area and excavation and off-site disposal of soil in and around the building floor drain outlet area. Based on the final 2007 closeout report documenting the removal action, the Regional Water Quality Control Board and the Department of Toxic Substances Control concurred with the report’s recommendation and the Navy’s request for no further action at IRP Site 44/45. The Navy subsequently reported the site status as no further response action planned.

IRP Site 46 was established in response to the disposal of used filters from a paint booth air filter system in a maintenance building. A paint shop operated since the 1950s in the building located along the western side of Kitts Highway, north of the Pacific Coast Highway. Used filters from the paint booth were regularly disposed of in dumpsters. Discharge from washwater and solvents used to clean brushes, rollers, and miscellaneous paint equipment at the northwest corner of the building was drained through a concrete culvert into an unlined ditch nearby.

The paint booth within the paint shop was first described as SWMU 47. Investigations were conducted at IRP Site 46 in the 1990s and further assessment for the presence of hexavalent chromium was recommended. Based on results from a 1998 focused site inspection and a 1999 risk assessment, no further response action was recommended at IRP Site 46. The Department of Toxic Substances Control concurred in 2000 with the findings of the risk assessment report. The Navy subsequently reported the site status as no further response action planned.

IRP Site 47 was established in response to temporary drum storage in an area approximately 1,000 feet northwest of the PCH Bridge over Anaheim Bay. The contents of the drums and the period of use of the temporary drum storage area are unknown.

The Sea Scout Anaheim Bay Area drum storage area was first designated Area of Concern No. 8 in 1989. The drums were reportedly collected, profiled, and transported for off-site disposal from the Sea Scout Anaheim Bay Area.

Based on a 1990 study, no further action was recommended, as the drums had been removed and no evidence of contamination was found. The Navy subsequently reported the site status as no further response action planned.

IRP Site 48 is approximately 500 feet south of the Kitts Highway and Anaheim Bay Road intersection and north of Anaheim Bay. The site was established in response to a diesel dispensing drum fuel spill that occurred at an unknown date.

The site was first described in 1989 as AOC 9. A 1990 study reported that small spills, less than 1 gallon, were observed at IRP Site 48. Containment, profiling, transport, and off‐site disposal of diesel fuel and surface materials affected by the spills occurred. No further work was recommended. The Navy subsequently reported the site status as no further response action planned.

IRP Site 71 is near Seal Beach Boulevard less than one-quarter mile west of Westminster Avenue. The external paint area was used for spray painting equipment.

The site was first described in 1989 as AOC 6. Evidence of yellow paint running into the storm drain was observed. The 1994 site inspection reported evidence of release in soil and recommended a study at IRP Site 70 to further assess contamination. Paints and solvents were collected, profiled, transported, and disposed offsite at a permitted and CERCLA‐approved landfill.

Based on the results of a 2002 study, no further action was recommended, and the Regional Water Quality Control Board concurred in a July 2002 letter. The Navy subsequently reported the site status as no further response action planned.

IRP Site 72 is a railroad supply yard less than one-quarter mile north of the eastern end of the Seal Beach National Wildlife Refuge. It was established in response to the presence of sandblast grit and unknown products spilled, piled, and left within the yard. The dates of operation and dates of waste disposal are unknown. Collected sandblast grit and unknown products from the Railroad Supply Yard were profiled, transported, and disposed offsite.

A 1989 assessment first described IRP Site 72 as AOC 7. A 1994 site inspection report recommended no further action. The Department of Toxic Substances Control concurred with the report findings in an August 1995 letter. The Navy subsequently reported the site status as no further response action planned.

IRP Site 73 area is the six-acre site of a former water tower 700 feet southwest of the corner of Forrestal Avenue and Hussey Road. The water tower had been periodically sandblasted and repainted since its construction in 1944. The most recent sandblasting and painting activities took place around 1994 and the tower was removed in 2002.

The site was first identified when a 1997 stationwide background study found elevated lead concentrations in soil samples collected in the immediate vicinity of the water tower. IRP Site 73 was included in a 2000 study that found nine metals above background levels in surface soils as well as detections of polynuclear aromatic hydrocarbons. Risk screening results concluded that risks to humans at the site are acceptable, but the risk to ecological receptors was unacceptable because of metals in soils, with lead being the primary contributor.

A 2002 study recommended remediation by excavation and off-site disposal of lead-impacted soil, while minimizing potential impact to cultural resources on and around the site. A removal action was completed, and excavated soil was disposed of offsite. The Regional Water Quality Control Board concurred with the recommendation for closure outlined in the 2003 closure report. The status at IRP Site 73 is no further response action planned.

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SWMU 17 is just south of Bolsa Avenue and about one-quarter mile east of Kitts Highway. The SWMU was established in response to wastes within the Waste Otto Fuel Drum Storage Area, which was operational from the late 1970s to an unknown date. The drummed waste Otto fuel and cleaning solvent was profiled, transported, and disposed offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 22 is near Seal Beach Boulevard about one-quarter mile south of Westminster Avenue. The SWMU consisted of sink drains and plumbing into which the waste photo processing chemical fluids Hypoclear and developer were disposed. An estimated 400 gallons per year were released to the sanitary sewer from 1978 to an unknown end-date. A 1990 site inspection was conducted, and the Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 24 is a rectangular, 0.69-acre area about 330 feet south of Westminster Street, and less than one-half mile east of Kitts Highway. The site was used from 1984 to 1998 for the removal of explosive residue from expended munitions, including Class C ordnance and combustion products. During operations, kiln dust and sludge wastes were stored in 55-gallon drums and disposed at an off-site facility. Soil samples were collected during site decommissioning in 1998 in areas where structures had been located to assess possible impacts from past operations. Elevated metals concentrations were found. Based on a 2002 study, unacceptable risk to ecological receptors from lead in the upper 2 to 4 feet of soil prompted a plan for a removal action. Groundwater, located at about 21 feet below ground surface, was not impacted.

The excavation of 1,684 tons of impacted soil was conducted in 2002. As outlined in the 2003 closure report, verification soil sample results were below the target cleanup levels. The Department of Toxic Substances Control and the Regional Water Quality Control Board) concurred in 2003 with the closure report for SWMU 24 and the no further response action recommendation. The Navy subsequently reported the status at SWMU 24 as no further response action planned.

SWMU 41 is near Kitts Highway, about one-quarter mile north of Pacific Coast Highway. The site was established in response to wastes within the Drummed Waste Oil Storage Area, which was operational from 1972 to an unknown date. Waste oils were profiled, transported, and disposed of offsite at a CERCLA-approved landfill. IRP Site 42 includes SWMU 41. This site was closed and received regulatory agency confirmation from the Regional Water Quality Control Board and the Department of Toxic Substances Control in 2007. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 42/43 was established in response to wastes within oil/water separators at the Maintenance Shop. The oil/water separators were operational from 1980 to an unknown date. Waste oils were collected, profiled, transported, and disposed offsite at a CERCLA-approved landfill. IRP Site 42 includes SWMUs 42/43. This site was closed and received regulatory agency confirmation from the Regional Water Quality Control Board and the Department of Toxic Substances Control in 2007. The Navy subsequently reported the status of the SWMUs as no further response action planned.

SWMU 50 was established in response to wastes within the Water Scrubber Collector System, an air treatment unit used to remove sandblast grit from the work area. The unit was operational from the 1980s to an unknown date. Waste paint and sandblast grit were collected, profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 51 is near Seal Beach Boulevard, less than one-quarter mile north of Pacific Coast Highway and was established in response to wastes discovered within an abandoned paint locker. Wastes included old paints and solvents. The paint/solvent storage area was operational for an unknown period. Waste paints and solvents were collected, profiled, transported, and disposed offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 52 is near Kitts Highway, just north of the Seal Beach National Wildlife Refuge, and was established in response to wastes contained within the Hazardous Waste Drum Storage Area. Sandblasting waste and contaminated rags were found in 55-gallon drums. The storage area was operational for an unknown period. Waste sandblast grit and contaminated rags were collected, profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 53 is located just north of the National Wildlife Refuge and was established in response to wastes contained within the Hazardous Waste Drum Storage Area. The storage area was operational for an unknown period. Paint-related wastes, empty cans, rags, and other flammable materials were collected, profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 54 is near Westminster Street and was established in response to wastes contained within the Hazardous Waste Drum Storage Area. The storage area was operational from 1984 to an unknown date and contained waste lead sludge and particulates accumulated in a cyclone dust collector from SWMU 24. The waste lead sludge and particulates were profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 55 is near Seal Beach Boulevard, about one-quarter mile north of Pacific Coast Highway and was established in response to wastes contained within the Hazardous Waste Drum Storage Area. The storage area was operational from the 1980s to an unknown date and contained waste sludge from the SWMU 50 water scrubber. The waste sludge and water were profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

SWMU 56 is near Seal Beach Boulevard, about one-quarter mile north of Pacific Coast Highway and was established in response to wastes contained within the Hazardous Waste Drum Storage Area. The storage area was operational from 1987 to an unknown date and contained waste paint thinner. The waste paint thinner was profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned with concurrence in July 2002 from the Regional Water Quality Control Board.

SWMU 57 was located at the corner of Missile Road and Third Street and was used for maintenance from 1989 to 1996. It was established in response to wastes contained within the Former Paint Locker Area. A 2002 study reported metals and volatile organic compounds in soil. A human health risk screening found only arsenic above acceptable levels in soil. A remedial action was conducted at SWMU 57 during 2006 and 140 cubic yards of metals-contaminated soil were excavated to a depth of 4 feet for off-site disposal. The Department of Toxic Substances Control and the Regional Water Quality Control Board concurred with the 2007 closure report recommendation, and the Navy subsequently reported the status of the SWMU as no further response action planned.

SWMUs 58 through 64 were located throughout the station and were established in response to wastes discovered within various paint lockers. Wastes included paints, alcohols, trichloroethylene, and other solvents. The paint/solvent storage areas were operational for an unknown period. Waste paints, alcohols, trichloroethylene, and other solvents were collected, profiled, transported, and disposed of offsite at a CERCLA-approved landfill.

During a 1989 RCRA facility assessment, most metal paint lockers were observed to be located on concrete or asphalt. No signs of release were visible on soil around those on soil. The 1989 report suggested no further action for these SWMUs because adequate control mechanisms to preclude releases of hazardous wastes or constituents were found to be in place.

A 1995 technical memorandum that reported on the results of site visits and confirmation sampling found no potential for release at SWMUs 58 through 64 and, in consultation with the Department of Toxic Substances Control and the Regional Water Quality Control Board, recommended no further action. The Navy subsequently reported the status of the SWMUs as no further response action planned.

SWMUs 65 and 66 were on the western side of the station, near Kitts Highway and Seal Beach Boulevard, respectively. The sites were established in response to wastes within the Sandblast Grit Cyclones. These paint booth air treatment units were used to remove sandblast grit and paint particulates from the work area. The period of operation for the sandblast grit cyclones is unknown. Waste sandblast grit and paint were collected, profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMUs as no further response action planned.

SWMU 69 was in the northeastern portion of the station, near Perimeter Road, and established in response to wastes contained within the Hazardous Waste Drum Storage Area. The storage area was operational for an unknown period, and contained waste trichloroethane, rags, toluene, and absorbent. The wastes were profiled, transported, and disposed of offsite at a CERCLA-approved landfill. The Navy subsequently reported the status of the SWMU as no further response action planned.

The former Building 128 Strip Pit is near Seal Beach Boulevard, just south of Westminster Avenue at a hazardous waste storage facility. The strip pit was used for metal finishing operations from 1975 until an unknown date.

Copper, trichloroethylene, and other volatile organic compounds were contained in the Building 128 Strip Pit. The contaminants were removed from the strip pit and the Navy subsequently reported the site status as no further response action planned with concurrence in 2002 from the Regional Water Quality Control Board.

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MRP Site UXO 1, also referred to as the Primer/Salvage Yard and Port of Long Beach Mitigation Pond, is a known munitions and explosives of concern area located in the south-central portion of the installation. The Port of Long Beach constructed the 39-acre mitigation pond in 1989. It is a tidally influenced pond immediately south of Slough Road that makes up the southern portion of UXO 1. The 48-acre Primer/Salvage Yard area occupies the northern portion of UXO 1. From 1944 through the 1990s, the Primer/Salvage Yard was actively used for ordnance storage related to rocket and projectile segregation, inspection, and repackaging, as well as bomb and rocket overhaul.

Following a 2007 MRP preliminary site inspection, land and marine geophysical surveys were completed in 2009 to locate suspected buried munitions and explosives of concern at MRP Site UXO 1. Soil and sediment samples were collected from the bottom and water samples were collected from the surface of the mitigation pond. Although explosives or propellants were not found in any media, breakdown products from explosive compounds, which are possible munitions constituents, were reported in soil at concentrations below the human health screening criteria. Cadmium and lead were reported in soil at concentrations greater than the human health screening criteria, and cadmium, copper lead, selenium, and zinc concentrations in soil exceeded the corresponding ecological and background screening criteria.

During a 2017 investigation conducted to further evaluate the nature and extent of contamination, suspect munitions and explosives of concern and materials potentially presenting an explosive hazard were observed throughout MRP Site UXO 1, and a surface clearance was performed. An intrusive investigation of the subsurface was conducted and samples were collected from soil and from sediment, and surface water in the pond.

Based on the results of the investigations and risk screening, a feasibility study was recommended to evaluate remedial action alternatives that will mitigate potential human and ecological exposure to materials potentially presenting an explosive hazard or munitions constituents remaining at the site. A proposed plan is currently underway and MRP Site UXO 1 remains an active site.

MRP Site UXO 6, also referred to as the Westminster Port of Long Beach Fill Area, is between Westminster Avenue and Westminster Street. The 180-acre site was reportedly authorized for placement in 1989 and 1990 of 3 to 5 feet of fill excavated from the MRP Site UXO 1 Mitigation Pond, a known munitions and explosives of concern area, and three other man-made tidal ponds at NWS Seal Beach. The estimated quantity from the Mitigation Pond placed in the fill area was calculated to be 330,000 cubic feet and was suspected to include munitions.

Following a 2007 MRP preliminary site inspection, a hand-held detector-aided visual survey was completed in 2009 to locate suspected munitions and explosives of concern at MRP Site UXO 6 and soil samples were collected. A few materials potentially presenting an explosive hazard were identified during the survey. Analytical results found no explosives or picrate, a munitions constituent, present in the soil. Arsenic and lead were reported in soil at concentrations greater than human health and ecological screening criteria.

During a 2017 investigation conducted to further evaluate the nature and extent of contamination, several items identified as materials potentially presenting an explosive hazard were recovered during a surface clearance MRP Site UXO 6. An intrusive investigation of the subsurface was conducted and soil samples were collected. Arsenic and hexavalent chromium concentrations exceeded screening criteria in soil near recovered items and other metallic debris.

Based on the results of the investigations and risk screening, a feasibility study was recommended to evaluate remedial action alternatives that will mitigate potential exposure to materials potentially presenting an explosive hazard at the site. A feasibility study is currently underway and MRP Site UXO 6 remains an active site.

MRP Site AOC 2, the Explosives Drop Test Tower, is at the southern end of 7th Street in the Seal Beach National Wildlife Refuge. The site consists of a central 50-foot tower on a concrete pad that was used from 1955 to 1977 to perform free-fall and guided safety drop testing of fuzes, cartridges, experimental propellants, and other low-level explosive items. The tower itself was removed in 2020. Engineering drawings show guided drop testing was conducted by dropping ordnance through the center of the 50-foot-tall tower into a thick, 2.5-foot-square, 6-foot-high steel box. The bottom of the box was reinforced with a belowground 4-inch-thick armor plate on top of a 3-foot-thick concrete block.

No munitions and explosives of concern or related items were suspected to be present or at MRP Site AOC 2 because of controlled testing conditions and none were observed during a 2007 MRP preliminary site inspection. The site was included in a 2009 inspection because the possibility still existed for exposure to residual explosives compounds and their breakdown products, identified as munitions constituents. A hand-held detector-aided visual survey was completed in 2009 to locate suspected munitions and explosives of concern at MRP Site AOC 2 and soil samples were collected. Two munitions-related items were identified during the survey. Analytical results found no explosives present in the soil above screening criteria. Cadmium and lead were reported in a few soil samples concentrations greater than human health and background screening criteria.

During a 2017 investigation conducted to further evaluate the nature and extent of contamination, no munitions-related items were identified during a surface clearance MRP Site AOC 2. An intrusive investigation of the subsurface was conducted and soil samples were collected in three locations. Arsenic, cadmium, and hexavalent chromium concentrations exceeded screening criteria in several samples near munitions-related items and other metallic debris identified in the subsurface and recovered during the intrusive investigation.

Based on the results of the investigations and risk screening, a feasibility study was recommended to evaluate remedial action alternatives that will mitigate potential exposure to materials potentially presenting an explosive hazard or munitions constituents remaining at the site. A feasibility study is currently underway and MRP Site AOC 2 remains an active site.

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MRP Site UXO 2 was comprised of five unlined evaporation ponds and a settling basin. The complex was south of Westminster Street at 8th Street and operated from 1945 through the mid-1950s, in 1962, and in 1971 to demilitarize 5-inch projectiles. Ammonium picrate, known as Explosive D, was washed out of projectile casings and the washwater was discharged from a tank into a series of baffled concrete settling basins located on the south side of the building. The washwater was drained from the settling basins through a 150-foot-long concrete trench into a series of evaporation ponds, covering 2.3 acres. Treatment in the ponds while in operation consisted of controlled burns and, reportedly in 1948 only, detonation rather than burning. The last controlled burn was in 1962. The facilities ceased operation in 1972. Buildings 101 and 102 and the associated drain lines were demolished and removed in 2009.

A 2007 MRP preliminary site inspection included MRP UXO Site 02 and recommended further investigation for the presence of residual explosives compounds and their breakdown products, identified as munitions constituents. A hand-held detector-aided visual survey and soil sampling were completed in 2009 along the former drain lines, at former discharge points, and in the former ponds. Analytical results found no explosives or picrate present in the soil above human health screening criteria.

A 2011 final report documenting findings from the 2009 inspection recommended no further action at MRP Site UXO 2for munitions and explosives of concern and munitions constituents. The Department of Toxic Substances Control concurred with the recommendation, and MRP Site UXO 2 is closed.

MRP Site AOC 1, the Building 94 Settling Basin, is east of Case Road in the central portion of the station and operated from 1945 until at least 1981 as a gun propellant-charge loading and breakdown facility for filling casings. Approximately 1.5 tons of discarded smokeless powder, a munitions constituent, were reportedly generated per week between 1945 and 1970. To prevent smokeless powder from accumulating, the interior of Building 94 was occasionally washed down with water. The wash water drained through floor drains that led to a settling basin east of Building 94. Small spills of other explosives compounds identified as munitions constituents that also occurred during operations at Building 94 were swept up, placed in powder cans, and taken to a magazine for storage. The frequency, duration, and amount of munitions constituents drained to the basin are unknown. Building 94 and the associated drain lines were demolished and removed in 2010.

Analytical results for Building 94 samples collected in 2003 reported concentrations of explosives and munitions constituents in floor drains below screening criteria. The investigation noted that the potential for the accumulation of gun propellant in drains that were inaccessible remained a concern.

A 2007 MRP preliminary site inspection included MRP Site AOC 1 and recommended further investigation for the presence of munitions constituents. A hand-held detector-aided visual survey and soil sampling were completed in 2009. A 20-mm cartridge casing was observed outside of the former settling basin. Explosives were not detected in soil samples from the end of the former drain line discharge area in the settling basin and other munitions constituents concentrations in soil were less than screening criteria.

A 2011 final report documenting findings from the 2009 inspection recommended no further action at MRP Site AOC 1 for munitions and explosives of concern and munitions constituents. The Department of Toxic Substances Control concurred with the recommendation, and MRP Site AOC 1 is closed.

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