Engineering and Expeditionary Warfare Center

Confined Disposal Facility

Schematic of a confined disposal facility
Schematic of a confined disposal facility

    

Abstract

Confined disposal facilities (CDFs) are disposal areas formed by engineered dikes that are used to retain sediments dredged from the bottoms of streams, rivers, lakes, and coastal waters. They are used to contain sediments from both navigational dredging operations and environmental dredging operations.

 

  Abstract      Names      Description      Applicability     Cost     Duration     Limitation     Publications     Related Sites 

 

top of page

Other Technology Names

  • CDF
  • Near-shore Confined Disposal Facility
  • Near-Water CDF
  • Upland Confined Disposal Facility

 

 

top of page

Description

A CDF is a technology where dredged material is placed in subaqueous, intertidal, or upland areas inside perimeter dikes that are built up above the adjacent water surface level. The dikes needed to form CDF cells may be constructed at an upland location (above the water table), partially in the water near shore, or completely surrounded by water. A CDF may contain a large cell for material disposal, and adjoining cells for retention and decantation of turbid, supernatant water. In general, water is discharged over a weir or allowed to migrate through the dike walls, maintaining the solids within the CDF. A variety of linings have been used to reduce seepage through the dike walls. The most effective linings are clay or bentonite-cement slurries, but sand, soil, and sediment linings have also been used.

Three key factors normally will influence the development and implementation of CDF technology at a given site: location, design, and monitoring. First, the location of a CDF will depend on physical site parameters (such as the relationship sizes of the site and the CDF technology required for remediation, and proximity to a navigable waterway); construction parameters (such as geology and hydrology of a site); and environmental effects of the CDF on the site. Second, the design of a CDF should be directed toward the goal of minimizing contaminant loss. Therefore, potential contaminant release pathways must be identified, followed by the selection of controls and structures that will limit contaminant release. Common contaminant release pathways include leaching through the bottom of a CDF, seepage through CDF dikes, volatilization to the air, and uptake by plants and animals. Caps are a potentially effective method of minimizing contaminant loss through pathways associated with CDFs, but selection of proper CDF liner material is also important for proper containment. Finally, continuous monitoring is required to ensure the structural integrity of a CDF. Long-term monitoring of CDFs can include of monitoring the following: structural integrity of the dikes, cover integrity (if applicable), groundwater/surface water impacts, water quality monitoring of the discharge, air emissions, and various chemical parameters.

The size, shape, and design of each CDF is different and based on the dredging needs of the harbor(s) or channel(s) served and the physical and chemical characteristics of the dredged material. The key to controlling contaminants associated with dredged material is to contain as high a percentage of the sediment particles as possible. A principle goal of CDFs is to receive and confine dredged material and return excess water with minimal suspended sediments to an adjacent water body.

CDFs have dikes that resemble a breakwater and are made of such materials as stone or gravel. Large armor stones are typically placed on the outside face of the dike to protect against wave action. The inner core of the dike is often constructed with sand and gravel, sometimes in discrete layers. The dike, which is permeable, encircles the disposal area where the dredged material is placed. The sediment particles and contaminants bound to the particles settle out in the disposal area and excess water passes back through the dike. As the facility becomes filled, the dikes become less permeable, and water must be removed by overflow weirs, filters in the dikes, or pumping.

Upland CDFs are designed with earthen dikes and resemble a levee or berm. The dikes are most often constructed with soil excavated from the disposal site, and the sides seeded to prevent erosion. Some CDFs incorporate liners or steel sheet pile in the dike walls to contain the dredged material that is typically placed into the facility by pipeline or truck. After the sediment particles have settled out, excess water is removed by overflow weir or pumping.

 

 

 

top of page

Applicability

CDFs are used to contain dredged sediments to reduce exposure to the material. These technologies can be applied to contain halogenated and nonhalogenated volatile organic compounds (VOCs) and nonhalogenated semivolatile organic compounds (SVOCs). Beneficial reuse of contaminated sediments includes creating near-shore habitats or innovative land expansions.

 

 

top of page

Cost

Major cost items can be divided into three categories including pretreatment costs, fixed costs, and variable costs. These cost categories along with some of the more common factors that impact individual cost components are provided in the following table.

Typical Cost Components

Cost Dependencies

PRETREATMENT COSTS

Site survey

Location of site; specific contaminants of concern; areal extent of proposed containment area

CAPITAL INVESTMENT (Fixed Cost)

Site preparation (utility locating, debris removal, fencing)

Areal extent of CDR; location of site (urban or rural); existing structures; fence perimeter; required signage; personal protective equipment (PPE) level; equipment decontamination

Mobilization/demobilization (transportation to site, mobile office, equipment storage)

Site location and facility requirements

Equipment leasing (e.g., dredging, excavation, and grading equipment)

Confined disposal facility design; areal extent; lithology; location of site (urban or rural); existing structures; PPE level

Labor (for transportation and on-site setup)

Location; facility requirements; equipment complexity; PPE level; equipment decontamination

Containment area construction; dike and weir construction; settling basin construction

Containment area type; areal extent of containment area; depth and design of containment area; existing lithology; fill and liner material selection

Monitoring well installation

Areal extent of contamination; specific contaminants of concern; monitoring requirements and number of monitoring wells; lithology; depth to contaminated interval

OPERATING COST (Variable Cost)

Long-term inspection

Site location; surface inspection requirements; containment design failure and repair strategy; PPE level; equipment decontamination

Equipment leasing (e.g., pumps)

Dike water removal requirements; confined disposal facility repair requirements

Labor (for site inspection and sampling analysis for process control)

Inspection requirements; sampling requirements; PPE level; equipment decontamination

Sampling and analysis for process control

Remedial goals; performance criteria; site footprint; quality control measures; PPE level

Labor (for site supervision and quality assurance and health and safety support)

Site footprint; inspection requirements; repair schedules and requirements; quality control measures; site control measures

Waste disposal

Quantity of process control samples and frequency; disposition of debris

 

 

top of page

Duration

Installation time for a CDF typically ranges from 6 to 12 months. Operation and maintenance duration lasts as long as the contained sediment requires management. The period of time requiring active monitoring and maintenance is expected to be 20 years or longer. Several media may require monitoring, such as groundwater, surface water, air emissions, soils, and leachate.

 

 

top of page

Limitations

The following factors may limit the applicability and effectiveness of the technology:

  • Contaminants can potentially migrate from the CDF along several pathways, including effluent discharges to surface water during filling operations and subsequent settling and dewatering, rainfall surface runoff, leaching into groundwater, volatilization to the atmosphere, and direct uptake by plants or animals.
  • Contaminant losses from CDFs may also occur due to low pH conditions caused by bacterial oxidation of sulfur-containing sediments during crust management operations.
  • Without proper design and maintenance, CDFs can develop odor problems as well as mosquito and insect problems

 

 

top of page

Publications

Topics Title and Description Pages Size (KB)
 

Sediment: Implementation Guide For Assessing and Managing Contaminated Sediment at Navy Facilities (January 2005)

This document presents guidelines for conducting sediment site assessments and remedial alternative evaluations within the Navy’s Environmental Restoration program. It is intended for use by RPMs and their technical support staff as stepwise guidance that will apply to most Navy sediment investigations.

294 20,867

Dredging

Confined disposal

Evaluation of Dredged Material Proposed for Disposal at Island, Nearshore, or Upland Confined Disposal Facilities, U.S. Army Corps of Engineers Testing Manual ERDC/EL-TR-03-1 (January 2003). 

This manual is a resource document providing technical guidance for evaluation of potential contaminant migration pathways from CDFs.

337 4711
Confined Disposal Facility

Confined Disposal Facility (CDF) Containment Features: A Summary of Field Experience, U.S. Army Corps of Engineers ERDC TN-DOER-C18 (August 2000)

Describes field experiences with the application of containment features to improve the effectiveness of CDFs in retaining contaminants.

18 454
Contaminated Sediments

Contaminated Sediment Remediation Guidance for Hazardous Waste Sites, U.S. EPA-540-R-05-012 (December 2005)

This document provides technical and policy guidance for project managers and management teams making remedy decisions for contaminated sediment sites. It is primarily intended for federal and state project managers considering actions under CERCLA, although some technical aspects may also be applicable for RCRA sites.

236 2936
       

 

 

top of page

Related Sites

Topics Title and Description Pages Size (KB)
       
  ------------------------------------------ NONE -----------------------------------------    
       
       
       
       

top of page

 

SHARE THIS PAGE

1322 Patterson Ave. SE, Suite 1000, Washington Navy Yard, D.C. 20374-5065

  • Please read this Privacy Policy
  • GILS NUMBER DOD-USN-000702
Connect with Us