Laserfiche WebLink
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-8B 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 />