2022-11-07_PERMIT FILE - M2022001 (11)

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Table 6 Base Model and Modeled Site Groundwater Level Full Buildout Both Sites Full Buildout and Mitigation Difference From Location Baseline All SW Baseline Conditions Patrid a House 4736.3 4736.0 -0 33 Cline House 47368 47373 0.50 Harding House 4736.6 4737.8 1.25 Wiedeman House 13434 47382 4739.6 140 Wiedman House 13218 47385 47381 -0 40 Shape House 47384 4738.0 -0 44 HS Land and Cattle 47326 4732.1 -0 50 Karbowski Brave House 4725.5 47229 -2.55 Schmidt Well 4714.4 47089 -5.54 United Well 47120 47063 -5 69 Owens Well 47142 4710.2 -4 00 Wn ht House 47174 4711.1 -6.30 Schmidt House 47184 4715.3 -310 Smit House 47188 4716.5 -2.30 Kissler House 47295 47294 -0.10 Woolverton House 4730.8 4730.7 -010 Shimon House 4733.0 47331 0.10 Kern House 47338 47339 010 Rainbolt House 4735.9 4736.0 0.08 Gilcrest Valley HS 47370 47366 -0.37 6.3.3 Mitigation With Recharge It is not expected that the drop in groundwater head elevations to the north of the site will have a negative impact on the property or well owners in this area because the saturated thickness after full build out of both sites was between eighteen (18)and twenty(22)feet at the approximate well locations. If there is a complaint from the property and/or well owners, a recharge underdrain or recharge pond will be constructed north of the site (see Figure 7). The groundwater from the underdrain and/or wells to the south will be piped from the southern end of the site to the north underdrain or recharge pond to mitigate the drop in groundwater head elevation. The water would drop into a five (5)foot diameter manhole located at the north midsection line, between Cell 3 and Cell 7. This manhole would have an open bottom to allow water recharge through the bottom of the manhole in to the aggregate. The manhole would feed two(2)drains running east and west along the property line. Figure 7 depicts the modeled layout for the recharge drain option north of the site. The drain would be 24-inch diameter pipe with a zero(0) percent slope with an invert of 4,727 feet. The recharge drain to the north was modeled using the river module and the quantity of discharge to the groundwater table was matched to the groundwater removed from the model at the southern end of the site. The modelled recharge to the north of the site mitigated the drop in groundwater head elevation at the well observation points to less than two (2)feet. Details for the proposed underdrains are shown on Figure 7 along with details for the dewatering wells. The model was utilized to determine options and feasibility for mounding and shadow mitigation structures and are not final design. The baseline groundwater level is based on eight(8)months of piezometer readings taken at the site and further water level monitoring should be taken into account during design of the final mitigation structures. Groundwater Model Report—Section 20 Gravel Mine Site -12- August 2022