CHAPTER 4 - THE TECHNICAL BASIS FOR GROUNDWATER PROTECTION 



Cape Cod Aquifer Management Project Final Report Page 27 



their quality. Therefore, it is necessary that quality assurance measures 

 provide for complete documentation for all hydrogeologic investigations. 



Appendix G, "Quality Assurance of Ground Water Models Through Documen- 

 tation", provides detail on the necessary aspects of model documentation. 

 These documentation procedures should be followed for all groundwater flow 

 and contaminant transport models. These procedures have been adopted as 

 policy by the DEQE Division of Water Supply and are required in all 

 reports which involve modeling work submitted to the Division. 



4. 9 Groundwater Protection for Communities on Private Wells 



Protection of private wells and protection of areas that may be needed 

 for future water supplies are the main groundwater management issues in 

 Eastham. The work previously described focused on delineation and manage- 

 ment of the wellhead-protection area to a public-supply well. For East- 

 ham, relevant issues related to the groundwater resource that must be 

 understood by local officials include: groundwater occurrence and flow 

 patterns; rate of groundwater flow; contaminant fate and transport; the 

 potential for salt water intrusion; and the recharge areas of private 

 wells . 



A detailed understanding of groundwater characteristics is essential 

 in hazardous waste site investigations and in siting potentially contam- 

 inating land uses. In Eastham, one of the most common problems is the 

 siting of septic systems near private wells. Without localized ground- 

 water flow information, it is difficult to site wells and septic systems 

 appropriately. Private- well contamination from septic systems, landfills, 

 underground storage tanks, and commercial businesses using hazardous 

 materials are the major threats to groundwater quality in this town. 



The U. S. Geological Survey has completed significant hydrogeological 

 work throughout the Cape. However, the USGS 1977 water-table map for the 

 Eastham region was based on nine obseirvation wells and is only repre- 

 sentative of regional -flow conditions. The observation-well inventory 

 conducted by the CCAMP Data Management Committee did not discover enough 

 observation wells in Eastham that had been appropriately surveyed or were 

 located such that a new water-table map could be generated. However, with 

 the assistance of EPA, the Town of Eastham recently installed 14 water- 

 elevation pond gauges to determine groundwater flow directions in the 

 vicinity of the town landfill. Wells also will be drilled soon under a 

 state grant to study Great Pond. It may then be possible to measure water 

 levels and generate a detailed map. 



4.9.1 Private-Well Recommendations 



Based on this examination of the water-resource issues facing Eastham, 

 the Aquifer Assessment Committee recommended that DEQE develop 

 private-well guidelines and a model bylaw covering well construction, 

 installation and abandonment. Private wells are particularly susceptible 

 to contamination from sources such as a homeowner's disposal of household 



