Case Studies

10 Case Studies

Subaqueous capping of contaminated dredged material in open-water

sites began in the late 1970s, and a number of capping operations under a

variety of disposal conditions have been accomplished. The Corps has

conducted over 20 capping projects, with the majority conducted by the

USACE New England Division (NED). An overview of the field experi-

ences related to capping of contaminated dredged material is found in T

able 8. Projects have included sites in Central Long Island Sound, New

York Bight area at the mouth of the Hudson River, Puget Sound, and Rot-

terdam Harbor, the Netherlands. Data on capping projects vary widely in

their availability. The projects listed in Table 8 are not intended to be all

inclusive, but are representative of a range of site and operational condi-

tions. Brief descriptions of most of these projects and others are given in

the following paragraphs.

Long Island Sound

Capping is an alternative frequently used by the NED for disposal of

material dredged from numerous industrialized harbors in New England.

NED has documented the operations and monitoring programs in the Cen-

tral Long Island Sound (CLIS) disposal site and other sites as a part of the

Disposal Area Monitoring System (DAMOS). The DAMOS program was

initiated in 1977, and the experience gained from 15 years (1979-94) of

DAMOS capping experience is described in a series of DAMOS technical

reports, many of which describe operations involving capping. The cap-

ping experience gained by NED in the CLIS disposal area has recently

been summarized in a monograph (SAIC 1995) from which some of the in-

formation presented here is taken. Other capping experience gained by

NED in the New London disposal site can be found in DAMOS reports

and SAIC reports.

Over 15 years of disposal site monitoring of capped mounds in New

England have provided an important data set of sufficient duration to allow

evaluation of the long-term effects of capping contaminated dredged mate-

rial. The data set includes a broad spectrum of characteristics including

physical, chemical, and biological components. Future capping projects

can benefit from the lessons learned in these pioneering projects.

106

Chapter 10 Case Studies