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2019 dried out the quarry bottom successfully, showing no observable water inflow within the <br /> quarry bottom. Currently,the quarry bottom is located 150 feet(6150')above the approved final <br /> bottom from the permit mining plan (6000'). <br /> The Denver Water Board owns a water tunnel that passes through the basalt formation of the <br /> Ralston Quarry. This water tunnel has stagnant water at its low point around 6100' in elevation. <br /> Stagnant water indicates no groundwater inflow at this low point. This was observed by Brierley <br /> during their site visit in May 2019. The Denver Water-operated Upper Long Lake Reservoir has <br /> a water level around 6075' in elevation.No groundwater spring or seep has been observed <br /> between Upper Long Lake Reservoir and the Ralston Quarry to date. <br /> 2. Brierley Data and Analysis <br /> Brierley conducted a new SEEP/W analysis based on packer test data results from the original <br /> investigation in 2013. Based on these packer test results, Brierley arrived on a worse-case <br /> permeability of 2.5 x 10E-5 cm/s. Brierley used this permeability in the SEEP/W model <br /> assuming an empty reservoir with groundwater at 6094'. This elevation is conservative and is <br /> based on BA-5 being dry to 106 ft from its collar elevation of roughly 6200'. The SEEP/W <br /> analysis resulted in a worst-case calculated inflow of 143 gpm. <br /> The allowable seepage (design standard)was determined by applying the state standard for <br /> horizontal flow allowance to the depth of the reservoir as measured from the assumed <br /> groundwater elevation (6094'). Brierley then added the state standard for vertical flow <br /> considering the surface area of the reservoir perimeter at elevation 6094' and projecting that to <br /> the bottom of the reservoir. The allowable inflow was determined to be 167 gpm. Since the <br /> calculated inflow is less than the determined allowable inflow,the proposed final pit should not <br /> require a well permit or substitute water supply plan. <br /> The model figure from SEEP/W is attached to show the 1-ft slice of the reservoir half-section <br /> that was modelled along with a summary table. <br /> 3. Conclusion <br /> Based on all available data,there is no groundwater source known to exist within or outside the <br /> quarry that could be intercepted by the approved mining plan. SEEP/W analysis shows that a <br /> permissible amount of groundwater would be able to enter the quarry given a very conservative <br /> groundwater elevation assumption. Observations, excavations and borings into the basalt at <br /> elevations of 6100' (water tunnel), 6094' (borehole BA-5), and 6075' (Upper Long Lake)do not <br /> shown any signs of groundwater flows for many years. Water noted within other drill holes is <br /> highly likely to be surface water, given the mining method and low hydraulic conductivity of the <br /> host rock. <br /> The Ralston Quarry exists in a competent, low-permeability basalt that does not contain any <br /> known aquifers. It is highly unlikely that groundwater flows in excess of the state design <br /> standard will be encountered by the mining in accordance with the approved mining plan. <br /> Ralston Quarry GW 3 Cmg lxv khi and.As,o istm I'LIA' <br />