Section Env-Dw 302.11 - Preliminary Estimate of Wellhead Protection Area; Proposed Refinement Method(a) Subject to (b), below, the preliminary estimate of the wellhead protection area shall be derived using the applicable standard method specified in (c) through (g), below.(b) If sufficient data is not available for a standard method, the preliminary estimate shall be a circle centered on the well having a radius of 4,000 feet.(c) The standard method for estimating a wellhead protection area for a large overburden production well shall be the flow net technique as specified in (d), below, if sufficient information exists to construct a flow net.(d) The flow net technique shall comprise: (1) Constructing an ambient regional potentiometric surface map;(2) Calculating a cone of depression for groundwater being withdrawn at the pumping test production rate for a period of 180 days with no net recharge;(3) Constructing an ambient regional potentiometric surface map with the calculated cone of depression superimposed upon it;(4) Constructing 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) Delineating the wellhead protection area as that area from which groundwater flow lines are captured by the proposed well by extending the area of captured groundwater flow lines up gradient to a groundwater divide;(6) Identifying the recharge mechanisms in the wellhead protection area that will support the proposed permitted production volume; and(7) Refining the wellhead protection area with respect to no-flow boundaries, surface waters, existing pumping wells, well interference, and any other hydraulic influences.(e) The hydrogeologic mapping technique shall be used for overburden production wells when: (1) Sufficient regional potentiometric information is not reasonably available to construct a flow net for delineating the wellhead protection area; or(2) An aquifer is sufficiently confined such that the method described in (d), above, would not be technically correct.(f) The hydrogeologic mapping technique for an overburden production well shall be used to estimate the area from which groundwater flow lines originate and are captured by the well based on the following hydrogeologic information: (1) Surface watershed boundaries within which the production well is contained;(2) Surface water elevations where applicable;(6) Exploratory soil boring and monitoring well logs;(7) Topographic maps; and(8) All other available information that is pertinent to delineating the wellhead protection area.(g) The standard method for developing a preliminary estimate of the wellhead protection area for a large bedrock production well shall estimate the area from which groundwater flow lines originate and are captured by the well based on the following hydrogeologic information: (1) Hydrogeologic mapping information including lineament and bedrock mapping or other remote sensing analyses;(2) Observations gathered from bedrock drilling logs;(3) Geophysical data, if available;(4) Recharge mechanisms and an assessment of areas of induced recharge;(5) Hydraulic influences including: c. Existing pumping wells; andd. Well interference; and(6) All other available supporting information that is pertinent to delineating a wellhead protection area in a bedrock aquifer.(h) The proposed method for refining the wellhead protection area shall include:(1) A detailed description of the proposed method for refinement; and(2) A description of how the refinement will be documented in the final report.N.H. Admin. Code § Env-Dw 302.11
(See Revision Note at part heading for Env-Dw 302) #9008, eff 10-19-07
Amended by, Volume XXXVI Number 14, Filed April 7, 2016, Proposed by #11061, Effective 4/1/2016, Expires 4/1/2026.