CHAPTER 4 - THE TECHNICAL BASIS FOR GROUNDWATER PROTECTION 



Cape Cod Aquifer Management Project Final Report Page 30 



With a Zone II delineation in hand, land uses within the Zone II must be 

 identified and the potential nitrate load quantified for each. The total 

 nitrate load within the Zone II is summed and entered into the mass 

 balance equation along with other parameters such as nitrate concentration 

 in areal recharge and the volume of water withdrawn from the well. 

 Appendices to the nitrate -loading report provide a guide to the nitrogen 

 loads associated with a variety of land uses and a program for summing 

 these inputs on a personal computer. 



The value that results from this calculation is the concentration of 

 nitrate that can be expected in the pumping well after the system has 

 reached equilibrium between the sources of nitrate and the sources of 

 recharge. This equilibrium is reached when water particles from the 

 furthest extent of the Zone II have reached the pumping well. This will 

 require several years and is dependent on the geology, hydrology, recharge 

 rate, and withdrawal of water. 



This methodology was created to allow town planners and land-use mana- 

 gers to recognize the level of incremental development that will cause 

 nitrate concentrations in municipal wells to exceed planning goals and/or 

 health-based, water-quality standards. If used properly, this nitrate 

 accounting model provides a technical basis for evaluating future develop- 

 ment strategies and comparing trade-offs between various land uses and 

 development proposals in wellhead-protection areas. 



4.10.2. Guide to Contamination Sources for Wellhead Protection 



The Aquifer Assessment Committee established the need to provide both 

 local planning boards, conservation commissions, boards of health, and 

 state officials with the guidance for scientifically-based, 

 wellhead-protection strategies. This need was translated into the 

 development of the CCAMP handbook "Guide to Contamination Sources for 

 Wellhead Protection". The wellhead-protection strategies discussed 

 include siting acceptable land uses in recharge areas of public -supply 

 wells and determining those land uses that should be prohibited or 

 strictly controlled by an aquifer protection district bylaw. This guide 

 will be useful for investigating potential sources of groundwater 

 contamination for each land-use activity. 



The guide provides detailed, background information on 32 common 

 land-use (business activity) categories and the associated 18 contaminant 

 classes that are commonly used or generated as wastes. A poster-size 

 matrix, "Land Use/Public -Supply Well Pollution Potential Matrix", 

 developed for display is also included for use as a handy reference to 

 quickly determine which one or more of the 16 contaminants or class of 

 contaminants are commonly associated with each of the 32 land-use 

 categories and which may render groundwater at a public -supply well 

 undrinkable. In addition, this chart compares the pollution potential 

 characteristics of those contaminants, indicating whether they have a low, 

 medium, or high potential to contaminate groundwater if any are accidently 

 released to the environment. The guide also contains information on best 

 management practices that should be encouraged for each land use. 



