CHAPTER 4 - THE TECHNICAL BASIS FOR GROUNDWATER PROTECTION 



Cape Cod Aquifer Management Project Final Report Page 20 



4. 2 Characterization of the Resource 



4.2.1 Water-Table Mapping 



A good understanding of the water levels in an aquifer is a prerequi- 

 site for most groundwater studies, including the delineation of the re- 

 charge area or zone of contribution to a public-supply well. This will 

 be described in more detail later in this chapter. An accurate 

 water-table map with appropriate contour intervals is essential for 

 investigating contaminated sites and in deciding where to locate a variety 

 of land uses, including public-supply wells, landfills, sewage treatment 

 plants, industrial zones, even septic systems. Understanding groundwater 

 flow, which can be inferred from groundwater levels, is the first step in 

 resource-based groundwater management. 



The Aquifer Assessment Committee decided to examine existing water 

 level observation points and to refine, where possible, the previous 

 water-table map for Cape Cod produced in 1977 by the USGS . The group's 

 intent was to demonstrate how a refined water-table map might be developed 

 without drilling new wells and to develop a methodology for selecting 

 existing wells that should be measured to refine the existing water-table 

 map. In some cases, the USGS mapped contour intervals of ten feet in the 

 Barnstable area did not provide the high degree of resolution needed for 

 Zone II determinations or site specific contaminant investigations. The 

 committee explored the possibility of refining this map utilizing 

 additional existing data available from observation wells. 



4.2.2 Observation-Well Inventory 



The Data Management Group conducted an extensive inventory of observa- 

 tion wells that had been drilled by consultants, federal, state, and local 

 agencies and village water districts for the Town of Barnstable. The 

 first task was to thoroughly review the available geological and engineer- 

 ing studies at the local boards of health, conservation commissions, plan- 

 ning boards, water suppliers, consulting firms, the Massachusetts Depart- 

 ment of Environmental Quality Engineering, the Department of Environmental 

 Management's Water Resources Division, the US Geological Survey and the 

 EPA. 



Copies of drilling and soil logs were obtained whenever possible; 

 reports or other files were also used. Relevant information was copied 

 onto worksheets (Figure 4.1) to standardize and streamline the information 

 collection process . Each well was mapped onto a USGS topographic map and 

 identified by a unique number. 



