CHAPTER 6 - ANALYSIS OF LAND-USE WITHIN ZOC FOR TOXIC AND HAZARDOUS MAT. 

 Cape Cod Aquifer Management Project Final Report Page 56 



6 . 5 Discussion 



6.5.1 Risk to Public-Supply Wells 



The potential risk facing public-water supplies may be characterized 

 in various ways as a result of the inventory undertaken within ZOC #1. The 

 most overwhelming conclusion is the high potential threat posed by petro- 

 leum products . 



Underground storage tanks are the most pervasive potential contaminant 

 source in this ZOC. Not only are there 186 within the entire zone, a 

 large majority of these are clustered in the southern portion around the 

 Hyannis business district close to three of the public-supply wells. A 

 1320 foot (1/4 mile) radius from the three public-supply wells in the 

 southeastern portion of the zone illustrates the degree of risk presented 

 by these tanks. Within this distance there are 45 tanks. Fourteen of 

 these are over 20 years old and 11 are of an unknown age but in the ab- 

 sence of this information the Department of Public Safety regulations 

 consider these to be older than twenty years. Expanding the radius to 

 2640 feet (1/2 mile), 83 tanks are within the circle, of which 42 are 20 

 years or older and 20 are of unknown age. According to an EPA study, 

 tanks 20 years and older have a 57 percent chance of leaking, so it ap- 

 pears there is a significant public-health risk to the three public wells 

 in this area. 



Further, the investigation of spills and leaks indicates that 43 per- 

 cent of all such incidents were due to leaking underground storage tanks 

 and all six of the confirmed hazardous -waste sites are the result of 

 petroleum-product contamination. A management strategy of close monitor- 

 ing and scheduled removal of suspect tanks could greatly reduce the risk 

 to the water supply in this zone. In addition, the numerous threats to 

 groundwater quality in ZOC #1 warrant periodic water quality analysis of 

 monitoring wells in between the public wells and upgradient sources of 

 contamination. The public wells themselves should be tested regularly for 

 a wide range of organic compounds . 



The data collected for Barnstable's ZOC #1 was incorporated into the 

 Geographic Information System (CIS) project described previously in Chap- 

 ter 5. After the data was digitized, it was manipulated to evaluate the 

 pollution-potential risk to the water quality at the public-supply wells. 

 The GIS computerized database provided the means to ask many "what if.." 

 questions - a burdensome task otherwise. While the land-use survey de- 

 scribed in this chapter was an essential step, the GIS project enabled a 

 more sophisticated assessment of this information in risk assessment analy- 

 sis than would have been possible otherwise (see CCAMP GIS Demonstration 

 Project Report). 



6.5.2 Management Issues 



Of the several local, state, and federal programs examined, five 

 emerged as having the strongest potential groundwater protection measures. 

 These are the local toxic- and hazardous -materials bylaws in Barnstable 



