THE SUB-SURFACE GEOLOGY AND SURFACE COMPARISONS OF A SMALL URBANIZED EMBAYMENT- SAVIN HILL COVE, BOSTON MA

In 2005, the University of Massachusetts-Boston took delivery of a new, 60 ft research vessel. Sediment accumulation in Savin Hill Cove, home to the University's Marine Operations and cooling plant, restricts movement of the vessel. As a result, a dredge project was planned for late fall-early winter, 2006. In an attempt to elucidate the sediment dynamics and subsurface architecture of the Cove, we began a project to map the surface topography, surface features and subsurface architecture of the Cove.

Savin Hill Cove is dynamic anthropogenicaly modified indentation along the Boston shoreline trending east-southeast. The Cove contains large fringing mudflats on the southwestern and western margins. The northeastern margin is armored and the southeastern-facing mouth is guarded by extensive mussel beds that uncover at low tide. The cove receives water from Dorchester Bay and Boston Harbor, as well as sediment-laden water from the Neponset River estuary.

Our initial observations of the geology of Savin Hill Cove show the presence of modern channels, paleo-channels, mussel bars and gas charged sediments. Initial bathymetric map shows significant changes in depth throughout Savin Hill Cove. There is a channel originating from Patten Cove and terminating in the boat basin. A paleo-channel was observed in the subsurface that begins at Patten Cove and terminates at a different location than the surface channel. A channel related to a storm drain cuts the mudflat and parallels the armored margin. It terminates at the boat basin. The pre-dredge navigation channel is also seen leading away from the basin. There is a significant raise in elevation at the mouth of the cove indicative of the mussel bar that progrades into Dorchester Bay and is subaerially exposed at low tide. Post-dredge bathymetric maps show significant scour marks and alteration of depths from the dredge and a significant drop in elevation around the cooling system intake pipe.

The features mapped, both on the surface and in the subsurface will serve as a baseline for a long-term monitoring project designed to assess the health of the dredge, areas of rapid sediment accumulation, potential source areas, and sediment dynamics of the Cove linked to the Neponset River estuary.