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Title: Aquatic disposal field investigations, Eatons Neck disposal site, Long Island Sound : an environmental inventory
Authors: Cobb, Stephen P.
Reese, James R.
Granat, Mitchell A.
Holliday, Barry W.
Klehr, Edwin H.
Carroll, Joe H.
Keywords: Water quality--New York (State)--Eatons Neck (N.Y.)
Eatons Neck (N.Y.)
Dredging spoil
Dredged material
Sedimentation and deposition
Sediment transport
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredged Material Research Program (U.S.)) ; no. D-77-6
Abstract: As part of the Dredged Material Research Program being conducted by the U. S. Army Engineer Waterways Experiment Station, an investigation of the environmental effects of open water dredged material disposal was initiated at the Eatons Neck Disposal Site in central Long Island Sound, New York. However, because of local political and public opposition to the dredging project, the field investigation was terminated after Phase I, a 12-month baseline survey of the disposal site and surrounding area. Phase I data, therefore, were used to describe environmental conditions at the Eatons Neck Disposal Site as they were four years after cessation of disposal operations. Dredged material, building rubble, and other materials were dumped at the site for about 70 years (1900 to 1971); 9,841,000 m³ of dredged sediments were placed at the site from 1954 to 1971. Results of hydrodynamic, bathymetry, and sediment studies showed no evidence of dispersion of dredged material from the site. Thus it appears that the Eatons Neck site is suitable, from a confinement standpoint, for the disposal of dredged sediments. Measured current velocities were typically <30 cm/sec 2 m above the bottom; net tidal displacement of water was to the west or southwest at speeds <6 cm/sec. Bathymetric shielding by Cable and Anchor Reef contributed to the reduced flow at the site. Water chemistry data indicated that there were various types of spatial gradients in the central sound. However, it appeared that factors other than the presence of dredged material at the disposal site, e.g., river discharges containing sewage effluents and other chemicals, could explain these gradients. There appeared to be no major differences in chlorophyll a, dissolved oxygen, and dissolved and suspended metals between reference station A and disposal site station DSA. Particulate carbon and nitrogen were higher at the reference station than at the disposal site in March and May. However, interpretations of the-water chemistry data are unclear because daily temporal variation was not adequately separated from spatial variation due to a lack of synoptic data. There were no significant differences between reference station A and the disposal site stations for sediment mineralogy, bulk sediment, and interstitial water metals (with the possible exception of zinc and manganese), oil and grease, and cation exchange capacity. Ammonia, organic carbon, organic nitrogen, and pH, however, were all higher in the sediments at the disposal site than at the reference station. Sediments at the reference station were more fine grained in the upper 10 cm than at the disposal site. These differences are probably due to the larger amounts of organic matter in dredged material at the disposal site. No dissolved oxygen depletion was noted in the bottom water at the disposal site, however. It appears, in summary, that any effects of the presence of dredged material at the site on nutrients, metals, and other chemical variables in the central sound are minimal and are probably overshadowed by effects of sewage effluents and other river inputs. There were few significant differences in the abundance and composition of the benthic macrofauna between sampling stations located on the dredged material deposit and the reference stations. Areally the mud benthic assemblage extended across most of the disposal site and was widely present outside of the site boundaries. The relatively low abundance and diversity of benthos In the mud assemblages were not confined to the dredged material deposit. This trend suggests that these conditions were either natural or a result of perturbations other than the disposal of dredged material. The sand benthic assemblages located on reefs adjacent to and partially within the disposal site had greater abundances of organisms than the mud assemblage. Plankton variability and the small number of samples collected precluded any detailed analyses. However, no gross differences were observed in the plankton between the disposal site and reference stations. The Eatons Neck Disposal Site was found to be a valuable habitat for fishery resources, especially American lobsters. Commercially important species such as winter flounder were equally or more abundant at the disposal site than at the reference station. The disposal site is the major commercial lobstering ground in Long Island Sound. The abundance of suitable sediments (mainly dredged material), building rubble, and other materials for burrow constuction is probably responsible for the abundance of lobsters; the production of benthic organisms, the lobsters' diet, must also be adequate to support the abundant population. Accumulation of heavy metals by lobster as compared to the reference area was not noted at this site.
Description: Technical Report
Gov't Doc #: Technical Report D-77-6
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Technical Report

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