Table 9. Relative Cost Ranges for Select Liner Material Systems

ERDC TN-DOER-R6

December 2004

Table 9

Relative Cost Ranges for Select Liner Material Systems

Liner System

Qualitative Cost Ranges

Dredged material liner

Soil liner

$$$$

Modified soil/dredged material liner

$$$$$$$$

Geomembrane liner

$$$$$$$$$$$$$$$$$$$$

Geosynthetic clay liner

$$$$$$$$$$$$$$$$$$$$$$

Composite liner

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

Note: Each liner system includes a compacted subgrade.

Construction Contracts. CDF construction contracts are normally specification-based; although

performance-based criteria may provide contractors additional incentive to furnish innovative designs that

reduce costs while still meeting design requirements.

Quality Assurance and Quality Control. Exercise of good construction practices, including

protection of compacted lifts from desiccation and freezing, effective mixing of soil, and interlocking of

previous and subsequent liner lifts, should also include provisions for active and vigilant supervision of

construction activities and laboratory testing by qualified quality assurance and quality control personnel.

Details on quality assurance and quality control issues for liner systems are provided in EM 1110-2-1911

(USACE 1995) for earthwork and for geosynthetic systems by government (e.g., USEPA 1986a, 1987,

1993c), and industry trade organizations and manufacturers (e.g., Waste Management of North America,

Inc. (WMI) 1990, National Seal Company (NSC) 1991a, 1991b).

OPERATIONAL CONSIDERATIONS:

CDF operational considerations include dewatering,

performance/effectiveness, reliability, and monitoring.

Dewatering. CDFs differ from solid and hazardous waste landfills in that dredged material has

significantly higher initial moisture content. Therefore, dredged material dewatering should be

considered in liner design. Dewatering serves several purposes: (1) removal of potential leachate as the

water continues to move through the contaminated dredged material, (2) facilitation of the progression of

the geotechnical characteristics of the dredged material to a state of adequate strength to serve future site

use (e.g., ballpark, or borrow area for high organic content soils), (3) reduction in storage volume as water

is removed from pore spaces to produce space for future additional disposal, and (4) consolidation of the

dredged material, which tends to reduce its hydraulic conductivity. This reduced hydraulic conductivity

possesses both an advantage in reducing the overall permeability of a CDF for infiltration of precipitation

with consequent leachate formation and transport and the disadvantage of reducing the rate of future

dewatering.

Numerous methods of dewatering exist. Surface trenching for improved drainage and use of underdrains

(i.e., leachate collection systems), however, are the only technically feasible and economically justifiable

dewatering techniques for dredged material containment areas. Dewatering techniques employing various

surface trenching technologies, including progressive trenching, perimeter dragline trenching, and interior

trenching, are summarized in EM 1110-2-5027 (USACE 1987). Surface trenching techniques possess

significant advantages over underdrain systems alone in that trenches are able to access full depths of the

CDF, while leachate collection systems only target water accumulated on the bottom liner. Underdrains

have been successfully applied on a small scale; however, their use in large disposal areas has not been

proven economical as compared with surface drainage techniques. Formation of excess leachate that