APPENDIX C 



WATER-TABLE ELEVATIONS IN EASTERN BARNSTABLE, MASSACHUSETTS 



Douglas L. Heath and Ethan Mascoop 



U. S. Environmental Protection Agency, Region 1 



Boston, MA 



July 1987 



Introduction and Purpose 



The town of Barnstable is fortunate to have a good supply of ground 

 water for its public-water supply, industrial, commercial, recreational 

 and agricultural needs. As the town continues to develop, more demands 

 will be made for this resource. To help town planners understand the 

 groundwater system and to protect it from a variety of pollution sources, 

 the Cape Cod Aquifer Management Project (CCAMP) produced a map showing the 

 shape and elevation of the water table. The mapped area is in the eastern 

 half of the town and in part of western Yarmouth, a region of Cape Cod 

 which has experienced high growth over the last thirty years. 



The purpose of mapping the water table is to display the occurrence 

 and movement of groundwater as it moves under the force of gravity from 

 high to low elevations. The map produced by CCAMP indicates the position 

 of the water table undisturbed by pumping stresses from public supply 

 wells. The extent of ground water contamination from underground storage 

 tanks, chemical spills, road salt and septic system effluent, and other 

 sources, and the directional velocity of contaminated plumes, can be bet- 

 ter understood from the configuration of the water table. Another impor- 

 tant purpose is to help define areas of recharge to pumping wells which 

 must be protected from contamination to safeguard public health. 



Previous investigators have produced local and regional maps of the 

 water table. In 1977, the U.S. Geological Survey (USGS) published a Cape 

 wide water-table map based on observation well and pond data obtained in 

 May, 1976. The map identified six major fresh water lenses which supply 

 potable water to residents of Cape Cod (LeBlanc and Guswa, 1977). Informa- 

 tion from this study helped to provide a basis for estimating high ground 

 water levels (Frimpter, 1980) and to refine and calibrate a USGS three 

 dimensional numerical model of Cape Cod's ground water system (Guswa and 

 LeBlanc, 1981). In 1982, the Cape Cod Planning and Economic Development 

 Commission used the water-table map to delineate zones of contribution to 

 public supply wells (Horsley, 1983). In 1984, SEA Consultants, Inc. ob- 

 tained water-table elevations at 17 observation wells to produce computer 

 simulations of piezometric head. These maps indicated the response of the 

 water table in Barnstable to various amounts of recharge and wastewater, 

 especially at the Barnstable Waste Water Treatment Facility (WWTF) . The 

 maps also provided information to delineate zones of contribution to pub- 

 lic supply wells in Barnstable (SEA Consultants, Inc., 1985). However, 

 the study did not define the flow patterns of ground-water in the vicinity 

 of surface water bodies or the coastline, which affect local hydraulic 

 gradients and flow directions. Recently, water table -maps for smaller 

 areas of the town have been made that show groundwater directions related 

 to suspected sources of contamination. Some of these studies were done in 

 compliance with MGL Chapter 21E and in response to requests by the town of 



