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Remediation Guidance Document
Chapter 10

US Environmental Protection Agency. 1994. ARCS Remediation Guidance Document. EPA 905-B94-003. Chicago, Ill.: Great Lakes National Program Office.  

Table of Contents

OPERATIONAL CONSIDERATIONS

10. Operational Considerations

This chapter discusses operational considerations that are relevant to the remediation of contaminated sediments. Topics discussed include contracts and contract administration, water-based operations, and land-based operations.

Most of the experience in the management of contaminated sediments has been in the maintenance dredging of navigation channels. The Corps has a limited fleet of dredges nationwide, but most of the actual dredging is contracted to private dredging companies. In addition, most dredged material transport and rehandling, and all construction of disposal facilities for dredged material, are performed by contractors.

Guidance on contract administration for the design and implementation of Superfund remedial actions is provided in USEPA (1986b). The Corps has developed several pamphlets and manuals that provide guidance on contract administration and construction oversight, including:

Contracting

As discussed in Chapter 2, contract mechanisms and regulations for sediment remediation projects are specific to the proponent and funding organizations. The number, type, and scope of contracts for implementing a sediment remediation project will also be affected by the complexity of the remedial alternative(s) selected for the site.

Contract Administration

Contract administration is a broad term that includes inspection and construction management as well as general administrative activities. Inspection is necessary during all phases of construction activities to ensure adherence to specified quantities and quality standards. Construction management involves coordinating activities beyond the contractor's scope or control, tracking progress, determining and making payments, preparing and negotiating contract modifications, and project acceptance. Other contract administration activities include preparing the project plans and specifications, soliciting bids, and recordkeeping. Contract administration is an important step in the management of a remediation project to control the costs of contractual equipment and labor. The goals of contract administration are to ensure that the work is completed on time and that the contractor receives proper compensation. Contract administration encompasses all dealings with contractors from the time the contract is awarded until the work has been completed and accepted, payment has been made, and disputes have been resolved. Factors influencing the extent of contract administration activities include the nature of the work, the type of contract, and the experience and attitudes of the personnel involved.

The Corps typically estimates the level of effort required for the administration of a construction contract to be approximately 8 percent of the construction costs. Additional funds may be required for administration of environmental remediation projects because of the increase in regulation and safety requirements. Smaller projects (those with total costs less than $500,000) require a higher percentage allowance for contract administration costs.

Contract Requirements and Clauses

Dredging
The following general requirements are included in Corps maintenance dredging contracts and may be suitable for environmental remediation contracts:

Contractor Quality Control--The contractor is required to submit a Contractor Quality Control Plan that identifies personnel, procedures, control, instruction, records, and forms to be used for inspection of construction. Construction is allowed to proceed after acceptance of this plan.

Quality assurance and quality control must be performed to ensure that the contractor dredges to the appropriate depth and at the correct location specified in the contract. For maintenance dredging, this is accomplished by conducting hydrographic surveys before and after dredging. For sediment remediation projects, dredging contracts may be structured around dredging areas, depths, and volumes, or by acceptable contaminant concentrations to be left behind. At the Waukegan Harbor Superfund project, the consent decree specified the elevations to which sediments were to be dredged. Completion of the dredging was also contingent upon sampling and testing of the grain size of sediments at the new surface (USEPA 1984b). Quality assurance also ensures that the dredged material is placed at the location and in the manner specified in the contract.

Special Project Features--Special project features must be identified, such as utility location plan, survey note format, Notice to Mariners, buoy relocation positions, and survey information.

Real Estate--Real estate rights for the use of work and storage areas and access to the disposal site must be obtained and provided in the contract. Any additional real estate rights required by the contractor are obtained at the contractor's expense.

Payment--The Corps typically structures its dredging contracts for payment based on lump sums for mobilization and demobilization and a unit price ($/yd[3]) for the quantity of sediments dredged. An alternative method of payment is time-based, where the dredge and operator are essentially "leased" for a period of time. These methods both have their advantages and disadvantages.

A fixed or unit price contract is more readily used to obtain competitive bids for the entire dredging project. This type of contract gives the contractor an incentive to finish the job as rapidly as possible, which may be a problem if it is desired to slow the dredging process to reduce resuspension or for other reasons. The contract specifications must be tightly written to provide performance criteria for the dredging, penalties for not meeting those criteria, and contingencies for most foreseeable events that could cause delays. A poorly written contract and changes in site conditions are the primary reasons for contract disputes and claims.

A time-based lease contract allows for greater control of the contractor's activities. This type of contract may create a disincentive to the contractor to work quickly, and the total dredging cost is not fixed up front. Specifications may not need to be as tight for a time-based contract, although performance criteria and penalties still need to be defined.

Dredging contracts are typically structured with two unit prices. The first unit price (dollars per time or volume) would apply for a base level of effort for which the contractor is guaranteed payment. The second unit price would apply for additional time or volume necessary beyond the base effort. This method of subdividing the unit price item ensures the contractor a minimum level of effort on which to distribute indirect costs, and typically provides the contracting agency with a reduced unit price for additional effort if needed. Lump sum payments for mobilization and demobilization are appropriate for either type of contract.

General Clauses
Construction contracts typically include several clauses to assist in contract administration, including the following:

Liquidated Damages--Liquidated damage provisions establish a rate of assessment that is representative of the harm expected to be suffered if a contractor fails to perform on schedule. The contractor is required to pay a predetermined amount for each day the project is completed late. This may be especially important in remediation projects where highly contaminated materials are being handled, and poor performance, accidents, and spills can create serious environmental problems. In addition, delays caused by one contractor can have significant cost impacts on other contractors responsible for follow-on processes.

Bonding Requirements--Bid guarantees, performance bonds, and payment bonds are a form of security to ensure that the bidder will not withdraw a bid and will execute a written contract and furnish required bonds.

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Water-Based Activities

Equipment/Limitations

The various types of dredging equipment are discussed in Chapter 4. Dredging contracts can be advertised in several ways. The contract may specify the dredging equipment in great detail or may offer a limited number of acceptable equipment types. Another approach would be a contract in which all dredges meeting specific performance criteria are considered. Performance criteria could include minimum production rate, average solid content of dredged material, sediment resuspension characteristics, vertical and lateral accuracy of cut, and others.

Qualification or performance-based contracts are more difficult to prepare and administer than contracts for specified equipment. Contractors rarely have the type of quantitative information on performance needed to compare with other equipment, making selection more difficult. However, if performance criteria for the dredging operations are developed, they provide an incentive for contractors to make innovative modifications to their equipment and operations to meet the criteria, and develop the performance data needed for qualification.

Contracts for Federal navigation dredging projects require removal of sediments down to the project-specified depth and typically provide for payment of up to a 1-ft (0.3 m) overdredging to cover inaccuracies and variations in dredging methods. This serves as an equitable means of payment for complete removal of the required sediments. Any material in the allowable overdepth prism and allowable side slopes is not required to be removed. Any dredging below the allowed 1 ft (0.3 m) is considered excessive, and payment is not made for removal of the excess material.

In a sediment remediation project, consideration should be given to the effects of sediments sliding or sloughing into the area dredged and the practicality of overdepth dredging. As sediments are excavated, adjacent sediments will slide or slough into the depression. The side slope of any excavation is determined by the physical properties of the sediments and local hydraulic conditions. A side slope of 1:2 (vertical:horizontal) is commonly used by the USACE Detroit District when estimating the quantity of sediments to be dredged from Great Lakes navigation channels, although the natural angle of repose may be much flatter (Wong 1994).

Extensive sampling and testing may be used to accurately delineate zones of sediment contamination in three dimensions. When converting maps of sediment contamination into dredging plans, however, it should be recognized that dredges are not capable of removing sediments with precise accuracy, even with the most technologically sophisticated equipment. Dredging specifications with complicated variations in depth and width should be avoided. If a small hot spot is identified, it may not be practical for the dredge to excavate the hot spot in isolation from the adjacent material. Under normal operating conditions on Great Lakes tributaries, a vertical dredging accuracy of 0.5 ft (15 cm) can be expected. To obtain a greater degree of accuracy, excavation would have to be slowed significantly and limited to times when conditions (e.g., currents, waves, wind) are ideal.

The scheduling of dredging and other water-based construction activities may be restricted by a number of events, such as recreational boating traffic and the seasonal spawning of migratory fish. On the Great Lakes, the maintenance dredging season generally coincides with the opening (beginning of April) and closing (end of December) of the navigation locks at Sault St. Marie, Michigan. Despite its logistical and operational problems, winter dredging, as conducted at Waukegan Harbor, may be preferable to avoid the traffic and other restrictions during the warmer seasons.

Access

Most Corps dredging projects are limited to existing navigation channels. Access, therefore, is only limited by the existing shoal or deposit to be removed. For a remediation project, accessibility to the project site may be a problem for the dredging and transportation equipment. This is especially likely in areas outside of navigation channels with naturally shallow depths. In some cases, channels can be dredged to the remediation area to provide waterborne access.

Access and obstructions should be considered in the design phase. If the remediation area is divided by bridges, pipelines, or other obstructions, dredging equipment may have to be remobilized several times. Access points for mobilization should be identified in the project plans, and easements or rights-of-way should be obtained prior to contract advertisement. Another consideration for sediment remediation is the integrity of nearby structures. If the contaminated sediment area is located adjacent to a bulkhead, pier, bridge, or other structure, consideration should be given to the effect sediment removal will have on the integrity of the structure. Dredging at the Superfund project in Waukegan Harbor, Illinois, was prohibited within (6-9 m) because of this concern (USEPA 1984b).

The above discussion applies to dredging and construction from marine plants, which may not be practical for sediment remediation in small rivers and streams. Land-based dredging and construction will require access to the entire length of the waterway to be dredged. Easements and rights-of-way will have to be obtained from landowners, who must be compensated for damages to their property and landscaping. Land-based dredging will require construction equipment to operate in areas that are subject to flooding. The accessibility of the waterway for land-based dredging may therefore vary with the season.

Authorized Crossings

Authorized utility crossings exist in the bottom sediment of rivers and lakes. The type of utilities with authorized crossings include natural gas pipelines, wellheads/water intakes, electrical utilities, and telephone lines. If the dredge damages a utility, it could result in personal injuries and extended environmental or economic damages to the waterway or users of the utility.

When excavation is considered for a project, a determination of any potential authorized utility crossings in the project area must be made. This can be done by contacting the local utility companies in the area, the Corps district, and the U.S. Coast Guard.

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Land-Based Activities

The contracting options for land-based operations of a complex sediment remediation alternative are similar to those discussed earlier for water-based (dredging and transport) operations (also see discussion in Chapter 2). Contracts can be structured to a specific technology type or process unit, or can be opened to all technologies that can meet specified performance criteria. These performance criteria may include: minimum destruction or removal efficiencies for target contaminants, physical and/or chemical characteristics of solid residues, constraints on the quantity and quality of water or air emissions, and maximum time to completion.

Because of the interdependance of transport, pretreatment, treatment, and residue management components, the prime contractor should be responsible for providing all equipment and technologies that deliver the material to and between pretreatment and treatment units and manage all residues from them. The only land-based component that might be divided into a separate contract is the initial construction of a CDF.

There is significant documentation on the construction, operation, and maintenance of CDFs, including guidance provided by USACE (1987b). The management of a CDF for contaminated sediments should consider a number of issues, including:

For a complex sediment remedial alternative involving removal, it is likely that a facility, similar to a CDF in many respects, would be used for the storage, handling, pretreatment, and treatment of dredged sediments; treatment of water residues; and storage and possibly disposal of solid residues. A hypothetical layout of such a remediation facility is shown in Figure 10-1. At this facility, sediments are pumped into one of two settling basins. After dewatering, the sediments are excavated from the settling basin and transferred to an adjacent pretreatment system. Debris and coarse materials from the pretreatment system are placed into one of three residue storage areas. The bulk of the sediments are transferred to the treatment system. Solid residues from the treatment system are placed in one of the residue storage areas. Two storage areas are needed because the residues must be tested before they can be removed for final disposal offsite. The organic residue is placed in a tank trailer for transport to an offsite incinerator. Water from the treatment and pretreatment processes and the settling basins is routed to the water residue treatment system. Some of the treated sediments are transported to a remote site for beneficial use and others are disposed onsite.

Most of the operation and maintenance issues identified above for CDFs would apply to this hypothetical facility. Some additional issues may have to be addressed including:

The management of a facility with several process technologies working concurrently would require a significant level of effort.

All of the management issues listed in this section are discussed in the following paragraphs. A discussion of site closure and post-closure maintenance is also provided.

Water Management

The volume of water to be managed will depend on how the sediments are dredged and transported and on the process requirements of the pretreatment and treatment technologies. Hydraulic dredging will add a significantly greater amount of water to the sediments than will mechanical dredging, which would require that the CDF provide the ponding necessary for sedimentation and retention of suspended solids.

At most Great Lakes CDFs, the depth of the pond is typically maintained by placing boards within the weir structure. Other types of water level control systems include filter cells (passive control) and pumping (active control). Water level management will ensure maximum possible efficiency of the containment area by increasing the retention time. If inefficient settling is occurring in the basin, it may be necessary to operate the dredge intermittently to allow for sufficient retention time and sedimentation, or to install more extensive treatment systems for the CDF effluent. Effective management of the CDF pond can therefore produce significant cost savings to the project.

After a hydraulic dredging operation is completed, the pond within an upland CDF can be drawn down. The rate of drawdown can be slowed to allow settling to remove most of the suspended sediments from the water column and to reduce the loading to effluent treatment systems. Practices for dewatering dredged material are discussed in Chapter 6 and in detailed guidance provided by Haliburton (1978) and USACE (1987b). To facilitate dewatering, rainfall should be routed to one or more collection point(s) and drained as quickly as possible. Trenching and other methods may be used to promote drainage and desiccation.

There are a number of possible wastewater streams produced at a sediment remediation site that will require collection and routing for treatment. Wastewater treatment systems are discussed in Chapter 9. The raw effluent from a CDF during hydraulic dredging/disposal represents the largest potential water flow. Rainfall runoff, leachate, and process water from pretreatment and treatment technologies will have varying flow rates and durations. Depending on their quality and flow rate, some of these wastewater streams may be routed together and mixed before treatment.

Management of Plants and Animals

Management of Plants
Contaminated sediments dredged from freshwater sites and placed in an upland area will rapidly develop extensive vegetation without any inducement. In fact, fine-grained sediments from the most contaminated sites seem to support the most extensive vegetation. From freshwater sites, only the most grossly contaminated sediments and sandy sediments without nutrients have shown any limitations on vegetative growth. Sediments deposited in upland areas on Great Lakes CDFs are typically covered with vegetation in the first or second growing season.

Before a remediation project is initiated, the desirability of vegetation within the containment area should be evaluated. Vegetation can be beneficial because it helps to dewater dredged material, control dust, reduce volatilization losses, and improve effluent quality by filtering. Dense vegetation, however, may severely reduce the available storage capacity of the containment area, restrict the flow of dredged slurry within the area, and have to be removed in order to construct a cap/cover. In addition, the management of plant populations may be necessary to minimize uptake and environmental cycling of sediment contaminants.

To assess the potential for contaminant uptake by plants, the laboratory procedure of Folsom and Lee (1985) should be used. The Times Beach CDF in Buffalo, New York, has been used for more than 10 years as a full-scale laboratory for evaluating plant and animal uptake from contaminated sediments. A compilation of these studies was prepared by Stafford et al. (1991). Subsequent studies have identified plant species that have lesser uptake of certain contaminants (Simmers 1994) and may be suitable for some CDF applications.

Options for managing vegetation include periodically cutting or burning the vegetation, tilling, applying herbicides, planting acceptable species, and placing new sediments on top of existing vegetation. Some of these control measures may cause significant contaminant losses. The vegetation management plan for a disposal or holding site with contaminated sediments must weigh the advantages and risks mentioned above.

Management of Animals
Various animals will use dredged material disposal and holding areas as a habitat, even when facility management controls are in place. Most of the CDFs constructed within the Great Lakes are inhabited by colonies of migratory birds. Vegetated areas are inhabited by small mammals, and ponds (at in-lake CDFs) have limited fish populations. Within highly urbanized areas, disposal facilities for contaminated sediments are some of the most productive wildlife habitats in the area.

Unlike vegetation, animal populations provide no benefits to the operation of a disposal or holding site for contaminated sediments. If migratory bird colonies are present and establish nesting colonies on the facility, there may be conflicts in the scheduling of operations in or around these nesting areas. Fish populations in ponded areas may bioaccumulate contaminants to unacceptable levels and attract birds and humans. Birds and small animals (e.g., rabbits, mice) can attract dogs, and the carrion can attract rats.

Controls that can be used to manage animal populations include the use of noisemakers, predator images, and vegetation management (to discourage birds from using the site). In addition, rotenone, shocking, and elimination of ponds may be used to remove fish populations. Trapping and vegetation management may be used to control populations of small mammals.

Botulism Prevention
Avian botulism has been recorded in naturally occurring wetlands in nearly all parts of the world. It is due to ingestion of a toxin produced by the bacteria Clostridium botulinum. Botulism becomes a concern at CDFs when dredged material forms shallow ponds or is raised slightly above water. These shallow ponded areas provide an attractive food source for waterfowl. When the conditions necessary for bacterial growth occur in the CDFs, the potential for a botulism outbreak is established. Because botulism occurs in mud flats and shallow ponded areas, a preventive strategy for botulism should be part of the water management program. Proper placement of dredged material and drainage of the CDF through an outlet structure will prevent development of extensive mud flats and ponded areas.

A second approach for the prevention of botulism is to schedule the dredging/disposal operations during the cooler seasons. If mud flats or ponded areas develop during these cooler seasons, the potential for a botulism outbreak is minimized because of the inhibition of toxin production by cooler temperatures.

If a botulism outbreak occurs, every possible effort must be made to control its spread. Limitation of the spread of botulism can be implemented by attempting to eliminate the toxin production and by making the site unattractive to waterfowl. This can be accomplished using short-term and long-term methods. Short-term methods include making the site unattractive using noisemakers, power boats in the area, or imitation predators. The removal of bird carcasses from the affected areas is also a necessary short-term action to eliminate toxin production.

Long-term methods involve changing the environmental conditions to eliminate the toxin production. Flooding the site with about 30 cm of water or draining the site to allow the dredged material to dry would eliminate shallow ponded areas. Drainage of shallow pond areas is an effective technique that can be accomplished by using pumps and/or constructing trenches.

Health and Safety Requirements
The health and safety requirements for a CDF or a site where sediments are being handled, pretreated, and treated may be determined by the project authority or by regulations covering the materials being handled. The health and safety requirements for all Corps activities and operations are provided in USACE (1987e). A health and safety plan should be developed for all sediment remediation projects, regardless of the funding authority or applicable environmental regulations. Such plans are especially important with treatment processes that use high temperatures, pressure, or reagents that are hazardous, caustic, reactive, or combustible. Guidance on the development of health and safety plans for Superfund remediation projects is provided by USEPA's Standard Operating Safety Guides (USEPA 1992h) and Health and Safety Plan (HASP) (USEPA 1989f).

PPE, such as gloves, protective clothing, and respirators, is required by OSHA and USEPA for all contractors working on Superfund sites. Some types of PPE are likely to be necessary at sediment remediation sites as well. The purpose of PPE is to shield or isolate individuals from the chemical, physical, and biological hazards that may be encountered at a hazardous waste site when engineering and work practices are not feasible to control exposures. Careful selection and use of adequate PPE should protect the respiratory system, the skin, eyes, ears, face, hands, feet, and head.

The types of PPE that may be required will vary depending on the degree and type of contamination of the material, as well as the methods to remove, transport, and dispose of the material. PPE should be selected and used to meet the requirements of 29 CFR Part 1910, Subpart I.

Safety or contingency plans should be developed to minimize the consequences of accidents or natural disasters (USACE 1987e).

Equipment Decontamination
Vehicles leaving the site may have to be decontaminated and safety checks provided to ensure that materials are properly stored for transport, liners and cover tarpaulins are secured, and manifests for materials are properly documented. Routine maintenance of the site may also include periodic inspections and repairs to dikes, fence enclosures, and other site features.

Site Maintenance and Security
The purpose of site maintenance is to prevent contamination of the workers, protect the public from site hazards, and prevent vandalism. The degree of site controls necessary depends on site characteristics, site size, and the surrounding community. A site control plan should be developed, including a site map, site preparation, site work zones, site security, and safe work practices.

Site security is necessary to prevent exposure of unauthorized, unprotected people to site hazards; avoid vandalism; and prevent theft. To maintain site security, a physical barrier can be erected around the site, signs can be posted, and access points can be limited. Site security is a common problem at CDFs. Private citizens have vandalized or fished and hunted inside the CDFs. Because of the nature of construction activities, personal injury presents a liability concern at CDFs. Access should be limited during the filling stage of a CDF. This can be accomplished by installing a fence and/or posting signs.

Vehicles leaving the site may have to be decontaminated and safety checks provided to ensure that materials are properly stored for transport, liners and cover tarpaulins are secured, and manifests for materials are properly documented. Routine maintenance of the site may also include periodic inspections and repairs to dikes, fence enclosures, and other site features.

Site Monitoring
The scope of a monitoring program for a sediment remediation project will be project-and site-specific. For a complex remedial alternative conducted at an upland facility, items that may be monitored include:

Certain analytical capabilities will be necessary onsite if a treatment technology is used. An onsite laboratory is needed to rapidly measure chemical and physical parameters that are indicators of the performance of the treatment process. These indicators may be surrogates for the major contaminant of concern that can be tested more rapidly and at lower cost. The onsite laboratory may also be needed to support and maintain any continuous or "real-time" monitoring equipment. Offsite laboratories can be used for testing that is less time-critical to the operation of the remedial alternative.

Materials Handling
Within a typical CDF, contaminated dredged material is only handled once, during placement. In contrast, facilities constructed for clean dredged material are often constructed using the dredged material (i.e., the materials placed from one dredging operation are excavated and used to build up the dikes for the next operation).

At a facility used for a complex sediment remedial alternative, various materials may be handled on a continuing basis. Sediments can be dredged rapidly and placed into the facility over a relatively short period (weeks to months). Pretreatment and treatment equipment will require an extended period (months to years) to process the dredged sediments. As the pretreatment and treatment units operate, residues are created that may require immediate treatment, storage for later treatment, storage for transportation, or disposal onsite (see Chapter 9). The logistics of materials handling and internal transportation in such a facility may require detailed planning. Guidance on process plant designs in textbooks on chemical engineering might be useful in developing materials handling strategies.

Storage of Chemicals, Reagents, and Treatment Residues
A sediment remediation site, as illustrated in Figure 10-1, may require a number of storage locations for the chemicals and reagents used in sediment and water treatment and for residues of pretreatment and treatment technologies. Some of these materials may be hazardous, toxic, reactive, or combustible and require special storage containers. The number, size, location, and type of storage areas will be determined by the quantity and character of chemicals and reagents used, or of residues produced, and how these materials are to be rehandled, transported, or disposed.

Dust Management
Airborne contaminants can present a significant threat to worker health and safety, especially when dewatered sediments are being excavated and rehandled. Air monitoring may be required to determine if airborne contaminants are present and will aid in the selection of PPE. Dust particles, aerosols, and gaseous by-products from all construction activities, processing, and preparation of materials should be controlled at all times, including weekends, holidays, and hours when work is not in progress.

Provisions should be included in contracts to ensure that the contractor maintains all excavations, stockpiles, haul roads, permanent and temporary access roads, plant sites, spoil areas, borrow areas, and all other work areas within or outside the project boundaries free from particulates that could cause the air pollution standards to be exceeded or that could cause a hazard or a nuisance. Sprinkling systems, light bituminous treatment, or other equipment can be used to control particulates in the work area. To be efficient, sprinkling must be repeated at sufficient intervals to keep the disturbed area damp at all times. Particulate control should be performed as the work proceeds and whenever a particulate nuisance or hazard occurs.

Energy/Power Generation and Distribution
Some treatment technologies have significant energy requirements and may require special utility connections. If the distance to existing utilities and cost for connection are excessive, generators may be used to provide electrical power. Transportation and/or storage of fuels should also be considered during the design of the project.

Site Closure and Post-Closure Maintenance
As part of site closure, much of the equipment used onsite may require decontamination. Wash water from decontamination will have to be treated. Soil from the site that has become contaminated by contact with the sediments or residues, and materials that cannot be effectively decontaminated, such as plastic liners, may have to be disposed in a licensed landfill or co-disposed with solid residues.

The placement of a cap and/or cover on dredged material in a CDF is not a simple construction activity. Typically, the site has to be cleared of vegetation and large root systems have to be unearthed. The site then has to be graded for positive drainage and the sediments compacted before any cap/cover materials can be placed. Long-term maintenance activities at a CDF would be essentially the same as those at a closed landfill, including:

Plant species grown on a cap/cover are selected to provide erosion protection and should be low maintenance and have shallow root systems. Site security may be required after closure for areas where leachate collection/treatment systems are operated. Dredged material in CDFs is not known to exhibit uneven settling and methane gas production, which are common problems in sanitary landfills. Closed CDFs may be used for a variety of productive purposes. CDFs around the Great Lakes have been used for harbor and airport expansion, park and recreational areas, and wildlife habitat (Miller 1990).


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