EXECUTIVE SUMMARY 



In June 1991, SAIC conducted field operations at the Western Long Island Sound 

 Disposal Site (WLIS) as part of the DAMOS (Disposal Area Monitoring System) Program 

 for the U.S. Army Corps of Engineers, New England Division (NED). The objectives of 

 this study were (1) to provide information on the fate and effects of dredged materials 

 disposed since the previous July 1990 survey; (2) to assess the stability of the inactive 

 disposal mounds; (3) to determine the extent of infaunal recolonization; (4) to measure near- 

 bottom dissolved oxygen concentrations; and (5) to collect additional PAH and metals data at 

 the three reference areas. Field operations included a 1200 x 800 m bathymetric survey, 

 REMOTS® sediment-profile photography, near-bottom dissolved oxygen measurements, and 

 sediment sampling for chemical and physical analyses. 



Based on recorded disposal volumes, 86,462 m^ of material was disposed during the 

 1990-1991 season. The resulting WLIS "E" mound was 3.0 m high with an elliptical 

 footprint of 400 x 175 m. The WLIS "A", "B", and "C" mound heights remained 

 unchanged since the previous July 1990 bathymetric survey and were considered to be stable. 

 The height of the WLIS "D" mound decreased approximately 0.5 m, primarily due to the 

 consolidation of the mound sedunents. 



Infaunal recolonization of the recently deposited material occurred rapidly as 90% of 

 the on-site stations provided evidence of Stage III activity. Several stations west of the 

 WLIS "D" mound continued to exhibit low reflectance subsurface sediments although the 

 recolonization status was normal. Low reflectance, inferred to represent sediments from the 

 previous year's survey with high oxygen demand, indicated potential deleterious effects of 

 disposal operations and, therefore, warranted further investigation. 



Dissolved oxygen and sediment chemistry were analyzed at three WLIS reference 

 areas (2000W, 2000S, and WLIS-REF). Concentrations of dissolved oxygen in near-bottom 

 waters at the disposal site and reference areas were spatially homogeneous and within aerobic 

 levels. REMOTS® parameters indicated that reference areas 2000S and WLIS-REF had 

 received disposed material in the past, whereas reference area 2000W had benthic habitat 

 conditions characteristic of ambient sediments. Sediment chemistry analyses reflected this 

 disparity among the three reference areas, with the highest concentrations of PAHs and 

 metals occurring at 2000S and the lowest concentrations occurring at 2000W. Consideration 

 should be made to replace reference areas 2000S and WLIS-REF (as comparison areas for 

 the disposal site) with areas deemed not affected by historical disposal operations. 



