suspended solids benefits CDF effluent quality by reducing particulate- 

 associated contaminants as well as suspended solids concentrations. Increased 

 suspended solids removal and associated contaminant reductions beyond gravity 

 settling may be achieved by the addition of chemicals to promote clarification 

 of the discharged effluent. Both settling and chemical clarification test 

 procedures have been developed to assist in CDF evaluations, and these were 

 applied to the EFS sediment samples. Therefore, the primary purpose of this 

 report is to document and present the results of the settling and chemical 

 clarification tests performed as part of the EFS. 



Testing Objectives 



5. The objective of the settling tests was to develop data for predict- 

 ing the settling behavior of New Bedford Harbor composite, hot spot, and cap- 

 ping sediments when hydraulically dredged and placed in a CDF (intertidal or 

 upland). Objectives of the chemical clarification tests were to evaluate the 

 effectiveness of polymers for the removal of suspended solids from CDF efflu- 

 ent and to develop a conceptual design for removing effluent suspended solids 

 that will not settle by gravity in a dredged material confined disposal area. 



Scope of Work 



6. The scope of work included performing laboratory column settling 

 tests on New Bedford Harbor sediments to estimate the volume requirements for 

 the primary containment area. Jar tests were used to screen and select poly- 

 mers to promote flocculation and settling of suspended solids in primary CDF 

 effluent. The preliminary design of a mixing system to thoroughly mix the 

 polymer and effluent from the primary containment area was also developed. 

 Settling behavior was observed for three sediment types (upper estuary com- 

 posite, hot spot, and potential capping sediments). The chemical clarifica- 

 tion test was performed only on the upper estuary composite sediment sample, 

 since it represented a majority of the contaminated material that may be 

 removed by dredging. 



