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INTRODUCTION <br /> As part of the on-going development of the Deepe Pit, Flatiron Sand <br /> and Gravel Company plans to remove sand and gravel from areas <br /> designated as Stages 4 and 6 (as shown on Plates 1 and 2 ) . Each <br /> JI stage will be mined separately, with Stage 4 mined first. <br /> Currently, most of the sand and gravel underlying these stages is <br /> below the water table. To facilitate extraction of the sand and <br /> gravel , a dewatering trench will be constructed around the <br /> perimeter of each stage. This method of dewatering has been <br /> successfully used to dewater Stage 1 without adverse impacts . <br /> Stage 1 is immediately north of Stage 4 and east of Stage 6 . <br /> Because the depth to water in the vicinity of the new stages will <br /> f be increased and because there are wells in the area, Leonard Rice <br /> I Consulting Water Engineers , Inc. investigated the magnitude and <br /> lateral extent of dewatering. This report presents the results of <br /> r <br /> that investigation. <br /> EXISTING GROUND WATER CONDITIONS <br /> The Deepe Pit is being developed in the water saturated <br /> unconsolidated sand and gravel alluvium deposited by South Boulder <br /> Creek. The alluvium is underlain by impermeable non-water <br /> producing shale. The alluvium ranges in thickness from zero to <br /> about 20 feet thick and has been deposited in a valley <br /> ( approximately 4 ,000 feet wide parallel to South Boulder Creek. The <br /> alluvium is moderately permeable with a hydraulic conductivity that <br /> Iranges from 80-1200 gpd/ft2 and averages about 200 gpd/ft2 . The <br /> depth to water varies seasonally and from year to year due to <br /> fluctuations in precipitation in the drainage basin and local <br /> irrigation practices . The annual variation is up to 3 feet . <br /> Depending on location, the depth to water is generally 1 to 6 feet <br /> below ground level . The water table slopes to the north about 80 <br /> feet per mile. <br /> I� <br /> 1 <br /> Leonard Rice Consulting Water Engineers,Inc. <br />