An Environmental Survey of Effects of Dredging and Spoil Disposal, London, Connecticut.

The report considers the activities and findings of the several integrated research projects designed to monitor the environmental effects of dredging in the Thames River and dredge spoil disposal at the New London Dumping Ground. Surveying of dredging impacts on suspeded materials in the Thames River has been completed by UCONN. The data confirm earlier indications that effects are limited to within 150 m of the dredge. A model of the rivers flow characteristics has been selected and is in the the testing phase. Three predredging surveys were conducted to determine baseline temperature, salinity, suspended solids and light transmission characteristics of the lower Thames River. These data were also used, in conjunction with historical information, to estimate predredging circulation of the lower river. Mercury in river water was lower in February and April 1975 than during earlier periods, perhaps due to the removal by dredging of contaminated sediments. The report indicates large decreases, apparently due to natural seasonality, in benthic macrofaunal densities throughout the study area between predisposal and April 1975 collections. Predisposal water and sediment samples from 44 stations have been analyzed for fecal coliform and other bacteria. Highest fecal coliform counts were found in the river. Coliform counts were higher at disposal area stations on an ebb than on a flood tide, indicating that the Thames River outflow can have an effect on water quality within the designated disposal area.