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BRIERLEY <br /> ASSOCIATES <br /> Creating Space Underground <br /> February 25, 2019 <br /> File No.: 514104-001 <br /> Asphalt Paving Co. <br /> 14802 W 44th Ave <br /> Golden, CO 80403 <br /> Attention: Stan Opperman <br /> Subject: Summary of Hydrogeologic Conditions <br /> Ralston Quarry <br /> Golden, Colorado <br /> Ladies and Gentlemen: <br /> Brierley Associates (Brierley) has conducted subsurface geotechnical explorations at Asphalt <br /> Paving Co. (APC's) rock quarry located at 6569 Highway 93, just west of the intersection with <br /> West 64th Parkway, in Golden, Colorado. This letter presents a summary of the hydrogeologic <br /> conditions at Ralston Quarry as a response to the Colorado Division of Reclamation, Mining, <br /> and Safety adequacy review letter (Exhibit G) dated February 7, 2019 and the Colorado Division <br /> of Water Resources comments on the matter dated February 11, 2019. <br /> Observed Hydrogeologic Conditions <br /> Brierley performed two phases of subsurface investigations at the Ralston Quarry in early 2011 <br /> and drilled in the spring of 2013. The boring locations are illustrated on Figure 1, attached. <br /> During drilling, measurements of depth to groundwater were not feasible due to the use of drill <br /> fluids (bentonite mud) for coring the rock. Drill fluids were flushed from the boreholes prior to <br /> installation of temporary monitoring wells or packer testing. <br /> Monitoring the level of drilling fluid and water in flushed boreholes showed a small degree of <br /> fluctuation after drilling. Depths measured in a number of borings ranged from 6 ft below ground <br /> surface (bgs) to 9 ft bgs. Boring BA-5 was dry when measured; the measurement depth limited <br /> to 100 ft due to length of water level reader. The elevations indicated on the attached figure <br /> show the water surface within the low point of the quarry is at an elevation of 6155.9. The <br /> ground surface elevation of the adjacent BA-5 is approximately 6193.3, therefore borehole BA-5 <br /> is dry to an elevation of 6093.3 or deeper. <br /> Additionally, packer tests were performed to determine the permeability of the formation at <br /> depth. The packer test pumps water under pressure into a fixed length of the borehole. The <br /> amount of water intake into the formation is measured. Packer testing was performed in general <br /> accordance with ASTM D4630. The hydraulic conductivity of the bedrock ranged from 9.3 x 10-' <br /> centimeters per second (cm/sec) to 2.4 x 10-5 cm/sec, where measurable. For some intervals of <br /> the water pressure tests, the apparent hydraulic conductivity of the bedrock was below the <br /> sensitivity of the packer tests, as indicated by no measurable flow, or negative flow, during the <br /> test. <br /> 990 S. Broadway, Ste. 222, Denver, CO 80209 1303.703.1405 1 www.BrierleyAssociates.com <br />