42 



three replicates. Stations G300E and GIOOE have lower OSI values mainly due to the 

 detection of Stage I individuals only (Figure 3-15). 



3.4 WLIS D Mound 



The D mound was developed during the 1989-90 disposal season by the deposition 

 of approximately 185,000 m' of material generated by seven small projects in New York 

 and Connecticut (Germano et al. 1993). In July 1990, recolonization over the D mound 

 had appeared to be proceeding well, with many stations showing evidence of Stage III 

 organism activity in the subsurface sediments. The long-term recovery of the D mound 

 was monitored by REMOTS® sediment-profile photography in 1991, 1992, and 1993. 



In June 1991, sediments at several stations over the A and D mounds displayed a 

 decline in benthic habitat quality. Stations lOOS and 300S over the D mound were 

 characterized by low RPD and OSI values. In addition, the subsurface sediments were 

 described as extremely dark due to high concentrations of labile organics and sulphides. 

 High sediment oxygen demand (SOD) in conjunction with seasonal hypoxia within the 

 western Long Island Sound region was considered to be the cause of the anomalous 

 conditions over the A and D mounds (Williams 1995). However, consistent with the 

 DAMOS tiered monitoring protocols, monitoring efforts in the area continued with an 

 expanded scope. 



In July 1992, both REMOTS® sediment-profile photography and sediment toxicity 

 testing were completed at select stations over the A mound, D mound, and 2000W 

 reference area. Although the REMOTS® data indicated only marginal improvement, a 10- 

 day Ampelisca bioassay test for sediment toxicity showed no significant difference between 

 the three areas. Based on those results no remedial action was initiated and continued 

 annual monitoring was recommended (Eller and Williams 1996). 



REMOTS® photographs collected over the A and D mounds in August of 1993 

 displayed improving conditions, with the exception of Station D300S. At three years post- 

 disposal, sediments at this station failed to support a stable infaunal population. In 

 addition, a decline in benthic habitat over Station 200S was documented in the August 

 1993 data set. The 1993 REMOTS® images collected 200 m and 300 m south of the D 

 mound center were characterized by dark, nearly anoxic sediments, and inconclusive 

 successional stage information (Charles and Tufts 1996). Continued monitoring of the 

 southern flank of the D mound was recommended in August 1993. 



During the July 1996 monitoring cruise at WLIS, Stations 200S and 300S over the 

 D mound were revisited to document the changes in benthic habitat quality. Complete 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1996 



