APPENDIX E: HYDROGEOLOGIC CONSIDERATIONS OF ZONE OF CONTRIBUTION METHODS 

 Cape Cod Aquifer Management Project Final Report Page E-2 



improved telemetering systems. 



Reports of water-department statistics are submitted annually by public 

 water-supply companies to the Massachusetts Department of Environmental 

 Quality Engineering (DEQE) . The following table summarizes the total 

 volume of groundwater extracted, the length of each system and the number 

 of services or individual hook-ups in Barnstable at the end of 1984: 



No. of Well Miles of No. of 

 Water Company Gallons Pumped Sites Mains Services 



Barnstable Water Co. 1,016,042,000 11 45.32 6,358 

 Centerville-Osterville 



Fire District 

 Barnstable Fire District 

 Cotuit Fire District 



Total 1,951,445,800 31 341.33 17,648 



The highest annual well discharge in 1984 was 237,804,000 gallons at Mary 

 Dunn #2, operated by the Barnstable Water Company. This well, located 

 north of the Barnstable Municipal Airport, operated during every month of 

 the year at a mean rate of 651,518 gallons per day (gpd) or 452.4 gallons 

 per minute (gpm) . The lowest well discharge in 1984 was 1,960,000 gallons 

 at Barnstable Fire District's GP Well #1, located just west of Phinney's 

 Lane and approximately 900 feet north of U.S. Highway 6. This well 

 operated every month except during March at a mean rate of 5,370 gpd or 

 3.7 gpm. 



Well Discharge and Safe Yield 



The zone of contribution methods used by Cape Cod Planning and Economic 

 Development Commission (1983) and SEA Consultants (1985) rely solely on 

 the "rated safe yield" of a well for discharge information. The safe 

 yield (SY) may be defined as the maximum rate of extraction that a well 

 can safely pump without depleting an aquifer over a specified time 

 interval. In accordance with General Laws Chapter 111, Section 17, the 

 DEQE defined the safe yield of a public water well as: 



SY - (T) x (available water) x (safety factor) 



where SY - safe yield in gallons per day 



T - aquifer transmissivity, in gallons per day per foot, determined 



by the modified non-equilibrium method of Cooper and Jacob 



(1946). 



