Reports
Capacity determinations for overboard disposal areas in the Pooles Island vicinity
1992, Halka, J.P. and Panageotou, W.
Open-File Report 11
Introduction
In the northern Chesapeake Bay, overboard disposal sites in the vicinity of Pooles Island and the Aberdeen Proving Ground have been utilized for the placement of sediments dredged from adjacent shipping channels (Figure 1). Four sites, located in the vicinity of Pooles Island, are identified by the letter designations D, E, F, and G. Area G has been further subdivided into three sections which have been identified as G-South (also designated G-1), G-Central (G- 2), and G-North (G-3). Another site, identified as H, is located close to shore in the waters of the Aberdeen Proving Ground.
This area was first utilized for the overboard deposition of sediment when the approach channel to the Chesapeake and Delaware Canal was deepened from 27 to 35 feet MLW. This work was completed for the adjacent sections of channel during the period between 1965 and 1968. Since that time, the present sites have been utilized for the disposal of sediment dredged to maintain the channels at the presently authorized depth of 35 feet mean low water (MLW).
Maintenance dredging of the shipping channels is an ongoing process necessary to ensure navigational access. Suitable locations for the sediment removed from the channels must be found. These designated overboard disposal sites have been utilized for over two decades and a need has arisen to determine their remaining capacity. Planning for the disposal of sediments derived from future dredging projects can proceed only with adequate information on the remaining site capacity. In this report the capacity of these designated sites has been estimated based upon the existing bathymetry and a knowledge of the behavior of deposited sediments as assessed from 10 years of observations of maintenance dredging operations (e.g., Panageotou and Halka , 1987, 1988, 1989, 1990). Verification of the methods has been achieved, in part, by performing a comparison of the historical volume changes at the sites with the records of the sediment volumes derived from dredging operations.
This analysis of site capacity is based solely upon a knowledge of the physical characteristics and properties of the deposited sediments and the physical conditions existing in the northern portion of the Chesapeake Bay. The calculations are based upon estimates Of the deposited sediment depth, the slope of the upper surface, and the horizontal spread within the limits of the bathymetric data set. It does not include, nor depend upon, a determination of the potential for environmental impacts to the system resulting from the deposition of the dredged sediment. Management or regulatory decisions regarding the use of these sites, which may be made in the future to alter environmental effects, could significantly change the useable capacity.
