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Groundwater <br /> The construction of the Compacted Clay Liners as specified in the reclamation <br /> plan may have the potential to create groundwater mounding up-gradient of the <br /> proposed reservoirs. <br /> Cell1 Underdrain Design <br /> Due to time constraints prior to mining Cell 1, an underdrain has been specified <br /> upgradient of Pond 1. <br /> Determination of the discharge capacity of the underdrain was made by utilizing <br /> Darcy's law, written as: <br /> (1) Q=K (dh/dl)*A <br /> where <br /> K= hydraulic conductivity [ft/sec] <br /> dh/dl = gradient = change in head over change in distance [dimensionless] <br /> A= cross sectional area of the aquifer [ft2] <br /> The groundwater gradient was determined by plotting a groundwater contour <br /> map of the local area based on data from a regional published USGS study and <br /> onsite depth to groundwater data measured at the time of test hole drilling ( see <br /> Exhibit G — Groundwater Contour Map). The hydraulic conductivity was <br /> defined as 328 ft/day = .0038 ft/sec, which is thought to be a conservative value <br /> considering the up-gradient aquifer is outside of the alluvial aquifer boundary and <br /> is composed of fine grained silt and sand. The area of aquifer that will need to be <br /> drained is assumed to be the length of the up-gradient clay liner section times 8ft. <br /> The 8ft value is the assumed potential for groundwater mounding to the surface <br /> due to the clay liner blockage. This is also considered to be a conservative <br /> estimate of groundwater mounding. Substituting these parameters into equation <br /> (1) above yields a Qaguifer value of 0.68 c.f.s for the 750ft length of underdrain. <br /> The slotted pipe specification for the underdrain is 8" SDR 17 PVC Pipe with <br /> .125" slot size (manufactured by Certainteed). This section of pipe is designed to <br /> flow 0.025 c.f.s. per liner foot of pipe. The 750 ft section will therefore flow 18.75 <br /> c.f.s. <br /> The slot size specification is based on the underdrain filter design which was <br /> determined as follows: <br /> Determination of the underdrain filter was made by first taking sieve analysis <br /> from onsite borings TH-1 9'-10', Th-8 8'-9' and TH-11 8'-9' (see Table 6.4.7-4 <br /> Soil Sample Sieve Analyses). These borings were completed in in Cells 4 and <br /> 6, however should be representative of the soils found in Cell 1 adjacent to the <br /> proposed underdrain. <br /> Amen Aggregate Resource <br /> Specific Exhibits <br /> Page 44 of 84 <br />