40 



volumes of contaminated material 

 (between 20,000 - 70,000 m s or more) 

 were placed at one disposal point and 

 then covered with clean material. The 

 intended result of capping operations 

 is to produce a cross-sectional mound 

 profile that would consist of two 

 chemically distinct layers: a basement 

 layer of contaminated material covered 

 by a layer of clean material, as 

 opposed to the random, mottled cross- 

 sectional mix of contaminated and 

 clean material one would find in a 

 mound where "de-facto" capping had 

 occurred. The overall, reigning null 

 hypothesis for this tiered strategy is: 



H : Capping has isolated all 

 sediment contaminants 

 effectively. 



The monitoring tasks done to accept or 

 reject this hypothesis, along with the 

 underlying assumptions and sources of 

 uncertainty, are discussed below. The 

 main objective is to verify that indeed 

 contaminants are not leaching upward 

 through the cap material and are not 

 becoming available to the ambient 

 environment. 



Box 3.1 "Verify physical coverage of 



mound; characterize chemicals 

 in surface sediments " 



As mentioned previously, physical 

 monitoring of all DAMOS disposal sites 

 takes place on a routine (annual) basis; 

 this background physical monitoring 

 plays an important role in the 

 verification of capping projects. 

 Experience gained from the other 

 capping projects done at the Central 

 Long Island Sound Disposal Site (SAIC, 

 unpub.) has shown that strict 

 operational control of disposal events 

 is needed to insure creation of a 

 successful cap. Contaminated 

 sediment disposal must be performed 

 at a taut-wire mooring marking the 

 target location, and a combination of 

 precision bathymetry and REMOTS® 

 surveys must be performed at the 

 completion of contaminated sediment 

 disposal to confirm the areal extent of 

 contaminated sediment on the bottom. 

 REMOTS® profiling is used to map the 

 thickness of dredged material from 0- 

 20 cm thick; acoustic profiling is used 

 to map the presences of disposed 

 material > 20 cm thick. 



52 A Two-Tiered Monitoring Protocol For 

 Capped Mounds 



5.2.1 Tier One: Biological Processes and 

 Related Management Decisions 



Many of the monitoring procedures 

 and logical flow of tasks are similar to 

 those described in Section 4. However, 

 there are some important differences 

 which will be pointed out under the 

 appropriate subheadings. 



Once this has been documented, a 

 capping plan can be developed for 

 subsequent disposal operations to 

 maximize the areal coverage of the 

 contaminated sediment by clean 

 material. Immediately following 

 completion of the capping operations, 

 another combination of precision 

 bathymetry and REMOTS® surveys will 

 be performed to insure complete 

 coverage of the contaminated material 

 with the minimum thickness required 

 in the disposal project permit. Past 

 experience has shown that typically a 



An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites 



