Section Env-Ws 379.08 - Preliminary Estimate of the Wellhead Protection Area and Proposed Method for Refinement for Large Production Wells(a) The intent of estimating the wellhead protection area is to identify an area through which groundwater is likely to reach the well and within which potential and known contamination sources should be identified to determine the appropriateness of the well site.(b) For all large overburden production wells and for large bedrock production wells with permitted production volumes less than 216,000 gallons, the applicant shall present, in the preliminary report, a preliminary estimate of the wellhead protection area and a detailed proposal for performing either a standard method for refinement or an alternative method for refinement.(c) For large bedrock production wells with permitted production volumes equal to or greater than 216,000 gallons, the applicant shall present in the preliminary report: (1) A preliminary estimate of the wellhead protection area; and(2) A detailed proposal for a method for refinement that will produce a wellhead protection area that is based on site specific data and conservative assumptions, such as the wellhead protection area produced for large overburden production wells using the standard method pursuant to Env-Ws 379.08(e).(d) The preliminary estimate of the wellhead protection area for all large production wells shall be derived by drawing a circle with a 4000 foot radius around the well, or when sufficient data is available, by using the standard refinement method defined by Env-Ws 379.08(e).(e) The standard refinement for wellhead protection area refinement for large overburden wells shall be either a flow net technique or a hydrogeologic mapping technique as specified in Env-Ws 379.08(f), (g) or (h).(f) The flow net technique shall be used for unconfined wells where there is sufficient existing information to construct a flow net, including:(1) The calculation of a cone of depression for groundwater being withdrawn at the pumping test production rate for a period of 180 days with no net recharge;(2) The construction of an ambient regional potentiometric surface map;(3) The construction of an ambient regional potentiometric surface map with the calculated cone of depression superimposed upon it;(4) The construction of a flow net for the map with the superimposed cone of depression, in which contours are reported in feet or meters referenced to the national geodetic vertical datum;(5) The delineation of the wellhead protection area as that area from which flow lines reach the well;(6) The extension of the wellhead protection area up gradient to a groundwater divide;(7) Identification of the recharge mechanisms in the wellhead protection area that will support the proposed permitted production volume; and(8) Refinement of the wellhead protection area with respect to no flow boundaries, surface waters, existing pumping wells, well interference, and any other hydraulic influences.(g) The hydrogeologic mapping technique shall be used when:(1) Sufficient regional potentiometric information is not reasonably available to construct a flow net for delineating the wellhead protection area for large overburden production wells; or(2) An aquifer is sufficiently confined such that the method described in Env-Ws 379.08(a) through (f) would not be technically correct.(h) The hydrogeologic mapping technique shall be a contributing area analysis based on:(1) The surface watershed boundaries within which the production well is contained;(2) The surface water elevations where applicable;(3) The pumping test data;(6) The topographic maps; and(7) All other available information relative to delineation of a wellhead protection area.(i) The standard refinement method for large bedrock production wells with permitted production volumes less than 216,000 gallons, shall be a contributing area analysis based on the following hydrogeologic information:(1) Hydrogeologic mapping information including lineament and bedrock mapping performed by the United States Geologic Survey;(2) Recharge mechanisms and areas; and(3) Hydraulic influences including: c. Existing pumping wells, and(j) An alternative wellhead protection area refinement method shall be an analytical or numerical model which incorporates aquifer parameter values derived from the pumping test providing that the models assumptions are not violated and conservative estimates of aquifer parameter values are used. The use of model's that rely on porous media assumptions shall only be allowed for use with a bedrock well if those assumptions are demonstrated to be valid for the well site.(k) The wellhead protection area refinement proposal shall include:(1) A description of the preliminary estimate of the wellhead protection area completed in accordance with Env-Ws 379.08(d);(2) A map of the well location showing the preliminary estimate of the wellhead protection area on an original or a color copy of a United States Geologic Survey topographic quadrangle at a scale of 1:24,000 or 1:25,000, which includes the quadrangle title, scale and date;(3) A detailed description of the proposed method for refinement; and(4) A description of how the refinement will be documented in the final report.N.H. Code Admin. R. Env-Ws 379.08
(See Revision Note at chapter heading for Env-Ws 300) #6521, eff 6-4-97; ss by #6979, eff 4-21-99; ss by #8871, INTERIM, eff 4-21-07, EXPIRES: 10-18-07