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(1) A hydrogeologic report is required for any activity or use requiring a project permit regulated in Part 300, and proposed within a sole source aquifer, Group A wellhead protection area or critical aquifer recharge area with high or moderate groundwater sensitivity.

(2) The hydrogeologic report shall be prepared by a qualified professional who is a geologist, hydrogeologist, engineering geologist, or engineer, who is licensed by the State of Washington and who has experience preparing hydrogeologic assessments.

(3) The hydrogeologic report shall contain the following information relevant to the critical aquifer recharge area:

(a) The surface location of all critical aquifer recharge areas located on site or immediately adjacent to the site, and the permeability of the unsaturated zone;

(b) Groundwater depth, flow direction, and gradient based on available information;

(c) Currently available data on wells and springs within one fourth mile of the site;

(d) Currently available information on the location of surface waters within one fourth mile of the site;

(e) Historic water quality data for the area to be affected by the proposed activity or use compiled for at least the previous five-year period;

(f) Discussion of the effects of the proposed project on the groundwater quality and quantity, including:

(i) Predictive evaluation of groundwater withdrawal effects on nearby wells and surface water features;

(ii) Predictive evaluation of contaminant transport based on potential releases to groundwater;

(iii) Recharge potential of the site including permeability and transmissivity; and

(iv) If water use is proposed for the development activity, a description of the groundwater source of water to the site or a letter from an approved water purveyor stating the ability to provide water to the site;

(g) Best management practices relevant to the proposed activity or use;

(h) Provisions to monitor the groundwater quality and quantity;

(i) A spill plan that identifies equipment and structures that could fail, resulting in an impact to the critical aquifer recharge area. Spill plans shall include provisions for regular inspection, repair, and replacement of structures and equipment with the potential to fail;

(j) Salt-water intrusion addendums shall be required for withdrawals of groundwater or reductions in available recharge within one fourth mile of any part of Puget Sound, or a greater distance inland where there is evidence that chloride (bicarbonate + carbonate) ratio exceeds 1.5 equivalent parts per million at any time of the year. The addendum shall include an assessment of the likelihood and extent of seawater intrusion into a critical aquifer and a description of probable impact on wells on adjacent or nearby parcels;

(k) An assessment of how the development activity meets the protection standards established in SCC 30.62C.320;

(l) If the hydrogeologic report identifies impacts to critical aquifer recharge areas, the project applicant will be required to:

(i) Identify and provide an analysis of alternatives by which such impacts could be avoided or prevented; and

(ii) Provide a detailed mitigation plan for any unavoidable impacts. The mitigation plan should include preventative measures, monitoring, process control and remediation and a contingency plan, as appropriate;

(m) Recommendations for implementation and operation of activities, including size limitations, monitoring, reporting and best management practices (BMP);

(n) An evaluation of potential nitrate and nitrite impacts on the aquifer, including cumulative impacts of adjacent or surrounding developments and activities, and provide recommendations for monitoring and BMP of nitrate and nitrite generating activities; and

(o) Any other information necessary to determine compliance with this chapter. (Added by Amended Ord. 06-061, Aug. 1, 2007, Eff date Oct. 1, 2007; Amended by Amended Ord. 15-034, Sept. 2, 2015, Eff date Nov. 1, 2015).