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Relative to the reference areas, data collected over the majority of the WLIS H, G, 

 and F mounds indicate they are consistent with the normal pattern of recolonization 

 following dredged material disposal. The newest bottom features at WLIS appear to be 

 recolonizing as expected, with the exception of sediments at Station H50W. The WLIS H 

 and G mounds should continue to be monitored on an annual or every other year basis, 

 respectively, to ensure complete recolonization, including the presence of stable, mature, 

 benthic assemblages consistent with the DAMOS tiered monitoring protocol. 



Stations 200S and 300S over the D mound were revisited in 1996 due to concern 

 over slow recolonization rates. Station D300S has shown dramatic improvement since the 

 1993 REMOTS® survey, while slow recolonization at 200S persists (Figures 3-21 and 3- 

 22). The variability between replicates of D200S and D300S and the satisfactory benthic 

 conditions over the nearby G mound indicate that the problem is localized. 



In July 1992, it was determined that elevated levels of labile organics were 

 responsible for the poor benthic conditions observed over the southern flank of the WLIS 

 D mound. Dredged material mounds with elevated levels of organic material tend to 

 recover at a slower rate due to the increased chemical oxygen demand (COD) caused by 

 oxidation of the labile organics. Monitored periodically, the southern flank of the D mound 

 has been given six years to allow microbial action and chemical oxidation to break down 

 the organic load in the subsurface sediments. Within those six years, limited improvement 

 in benthic conditions has been documented in the surficial sediment layers. The 

 progression in habitat quality docimiented at D300S during the July 1996 survey is most 

 likely due to the construction of WLIS G approximately 60 m to die northeast. The 

 development of a wide apron around the G mound provided 10 cm to 20 cm of new 

 sediment to overlay the historic dredged material composing the southern flank of the D 

 mound. 



A final solution to the localized problem between D200S and D300S that would 

 facilitate the improvement of benthic conditions, as well as complement a recommended 

 management plan for the disposal site, is the development of a new disposal mound 

 southwest of the G mound center (Figure 4-2). A new sediment deposit composed of high 

 quality dredged material with a lower primary nutrient and organic detrims content would 

 overlie the southern flank of the D mound, covering any existing problems in the 

 subsurface sediment layers. In addition, the new material would assist in closing the 

 supplemental lateral containment cell described above, while promoting a healthy benthic 

 environment through faster recolonization and increased bioturbation. 



Sediments with low COD tend to facilitate the development of a healthy benthic 

 environment. By reducing the COD in the subsurface sediments, a higher percentage of 

 the available bottom water dissolved oxygen (DO) can be utilized for biological processes. 



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



