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Aic)bd hir ARCOSA <br /> Exhibit G—Water Information <br /> All water involved in the quarry operation will be handled in accordance with all applicable state and <br /> Federal laws.An NPDES Permit has been applied for and granted. The following is a characterization <br /> of the local hydrology. <br /> Surface Water Hydrology <br /> Surface water in the area of the quarry site is concentrated in two channels. The closest to the quarry is <br /> Coal Creek, a natural stream which flows along the west and north sides of the site. Coal Creek is a <br /> braided stream which flows to the northeast in a channel cut in the Pierre Shale. A thick(average 16- <br /> 20'), coarse saturated gravel fills the stream bed. As Coal Creek's water level fluctuates seasonally in <br /> response to water drawn off by irrigation and seasonal changes, the gravels are probably recharged by <br /> the creek at high flow and contribute water to the creek at low flow. Up-gradient from the site, the creek <br /> probably contributes water to the Rocky Flats Alluvium seasonally through infiltration. <br /> The second channel of concentrated surface water flow is a man-made channel, the South Boulder <br /> Diversion Canal. This structure diverts water from Eldorado Canyon to the southeast and eventually <br /> back to the southwest where it empties into Ralston Reservoir. At its closest it lies about 1/2 mile <br /> southwest of the site. This canal will be unaffected by the quarry. <br /> Precipitation on the surficial materials in this area is likely to infiltrate the alluvium at a high rate. <br /> Infiltration rates for the top 5 feet of soil were reported at 0.2 to 6.0 inches per hour(Moreland and <br /> Moreland, 1975). Branson, Miller, and McQueen (1964, Table 2)reported rates from 3.90 to 7.35 <br /> inches per hour for Rocky Flats Alluvium. Sheet or overland flow probably occurs during precipitation <br /> events exceeding these rates.Additional recharge to the gravels in this area probably occurs from Coal <br /> Creek percolation, the McKay and Upper Church Ditches, and possibly minor amounts from the South <br /> Boulder Diversion Canal. <br /> A ditch around that southern quarry slope and along the gravel/shale interface will intercept seeps and <br /> surface water, direct flows around the slope, along the road and to the pond. Precipitation falling into <br /> the pit will collect in an impoundment sump at the northeast corner of the quarry and be discharged in <br /> accordance with NPDES Permit requirements. <br /> Ground Water Hydrology <br /> Ground water occurs in several geologic units near the quarry site. A major regional aquifer which is <br /> exposed and recharged in the area is the Fox Hills Sandstone. The Fox Hills Sandstone here dips <br /> steeply to the east(50°to 67°, Spencer, 1961). The formation is exposed as a resistant ridge about.35 <br /> miles east of the quarry. The intervening interval (from the quarry to the ridge) is Pierre Shale. Because <br /> of the Pierre's very low permeability(i. e. on the order of 10.6 cm/sec hydraulic conductivity), the quarry <br /> operations will have no effect on the water level or quality in the Fox Hills aquifer. <br /> Two other confined aquifers occur to the west of, and stratigraphically down-section from, the quarry. <br /> The Hygiene Sandstone Member of the Pierre Shale forms a possible aquifer about 565 feet thick. It is <br />