Laserfiche WebLink
HYDROGEOLOGIC EVALUATION FOR THE FREMONT PAVING EVANS #2 PIT <br />PUEBLO COUNTY, COLORADO <br />1.0 INTRODUCTION <br />This evaluation provides a hydrogeologic assessment of the alluvial groundwater conditions <br />across the Evans #2 Pit (M- 2000 -041) project area. The evaluation has been prepared for <br />submittal to the Colorado Division of Reclamation, Mining and Safety in response to the <br />Preliminary Adequacy Review for Amendment 1 (AM -01) dated October 7, 2013. <br />The Evans #2 Pit is to be mined in three phases (Figure 1). Phase I is currently being mined <br />and, along with Phase III, will be reclaimed with a compacted clay liner to create below -grade <br />water storage reservoirs. Phase 11 is to be backfilled for open space following mining. <br />Additional areas within the permit boundary include previously mined Parcels 1 and 2 on the <br />western edge of the site and un -mined Parcel 3 where processing facilities are located (see <br />Figure 1). Parcel 1 is currently being backfilled as part of the final reclamation plan. Adjacent <br />properties are primarily rural with irrigated agricultural uses. The Arkansas River runs from <br />west to east along the southern permit boundary. <br />This evaluation will address adequacy review comments related to Exhibit G, Water Information, <br />of the Minerals Rules and Regulations of the Colorado Mined Land Reclamation Board for the <br />Extraction of Construction Materials. Specifically, the evaluation provides (1) a hydrologic <br />impact analysis to demonstrate the radius of influence of the dewatering operation for current <br />and future mining and reclamation phases, (2) an estimation of the static groundwater elevation <br />at the site assuming no dewatering, (3) an estimate of project dewatering flow rates, and (4) <br />recommendations to be included in a groundwater monitoring plan. <br />2.0 HYDROGEOLOGICAL CHARACTERIZATION <br />2.1 Regional Geologic Setting <br />The Evans #2 Pit site is located in the Colorado Piedmont Physiographic Province between the <br />Southern Rocky Mountain Province to the west and the Great Plains Province to the east (Deere <br />and Ault 2007). The Arkansas River alluvium varies greatly from below Pueblo Reservoir to the <br />Colorado - Kansas state line, extending more than 150 miles and ranging from one to six miles <br />wide. The Quaternary age valley fill is composed of sand and gravel deposits of the Piney Creek <br />and Post Piney Creek alluvium laid down by the Arkansas River (Deere and Ault 2007). The <br />alluvium is as much as 200 feet thick and consists of unconsolidated clay, silt, sand, and gravel. <br />Depth to the alluvial groundwater generally is less than 60 feet below the land surface (USGS <br />2002). <br />The Arkansas River alluvium is underlain by relatively impermeable Pierre Shale bedrock of <br />Cretaceous age. The shale is a thick sequence of clayey to silty marine shales containing fossils <br />and local beds of limestone. The alluvial deposits are covered by calcareous overburden clay <br />soils deposited by residual and slope wash processes. The overburden clay soils were eroded <br />from sub - cropping Pierre Shale bedrock to the north (Deere and Ault 2007). <br />Blue Earth Solutions, LLC * P.O. Box 2427 * Fort Collins, CO 80522 ♦ (970) 227 -2803 <br />