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BRIERLEY <br />ASSOCIATES <br />Creating Space Underground <br />February 6, 2015 <br />File No.: 514104 -000 <br />Asphalt Paving Co. <br />14802 W 44th Ave <br />Golden, CO 80403 <br />Attention: M.L. Richardson <br />Director of Strategy and Sustainable Development <br />Subject: Summary of Observed Groundwater 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 groundwater <br />conditions encountered. <br />Observed Groundwater Conditions <br />Brierley performed two phases of subsurface investigations at the Ralston Quarry, borings LH -1 <br />and LH -2 were drilled in early 2011 and borings BA -3 through BA -813 were drilled in the spring <br />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 during the drilling process and the tight rock formation. Groundwater measurements were <br />taken periodically in the holes that were still open after drilling was completed and two <br />temporary groundwater monitoring wells that were installed at borings BA -4 and BA -6 to more <br />accurately measure groundwater depths (Figure 1). <br />Groundwater measurements were between 6 ft below ground surface (bgs) and 9 ft bgs in <br />borings BA -7, BA -7A, BA -8, BA -8A, and BA -813 and monitoring well BA -6. Boring BA -5 was dry <br />when measured. Artesian conditions were observed in boring BA -3 and monitoring well BA -4 <br />with water seeping out of the top of casing or the top of the well after drilling was completed. <br />The quarry is situated within an intruded basalt plug that is surrounded by relatively <br />impermeable metashale and in our opinion acts as a closed local hydrologic system. It is our <br />opinion that the water table in the quarry is driven by local weather patterns and that it is <br />isolated from the regional groundwater table. <br />Artesian conditions occur when the water pressure in the formation is greater than the pressure <br />due to elevation head. Observations from the Brierley staff on site noted increased flow in <br />boring BA -3 corresponding with snowmelt or rain events. Mine slopes and broad benches exist <br />at elevations higher than, and to the north of, BA -3 and BA -4 at the north end of the quarry. <br />990 S. Broadway, Ste. 222, Denver, CO 80209 1303.703.1405 1 www.BrierleyAssociates.com <br />