Laserfiche WebLink
• <br />Coulson Excavating Company, Inc. - Bonser Gravel Pit <br />Exhibit G -Water Information <br />The proposed pit is located on the northeastern border of the Big Thompson Watershed Basin. <br />The local tributary watercourse is the Big Thompson River, which runs immediately south and <br />east of the site. M irrigation facility runs directly across the proposed pit, and an irrigation ditch <br />(Hillsboro ditch) runs south of the proposed area. In addition, a shallow un-confined aquifer <br />occurs at the site and adjacent properties from approximately 12 ft to 15 ft depth from the surface <br />extending down to approximately 20 ft to 25 ft below ground surface. The Local groundwater <br />flow direction is southeast. See Exhibit C for the location of the river and ditches. <br />The operation is expected to affect the groundwater/surface water system by exposing a small <br />amount of groundwater to the atmosphere. The only other water loss from the operation will be <br />pore water taken with the mined product. The total loss per year has been calculated as 1.41 <br />acre-ft year`', which is documented by the well permit filed with Office of the State Engineer <br />Division of Water Resources. Small amounts of groundwater from the site will be used for dust <br />control and gravel washing. <br />Water pumped from de-watering trenches will be piped to asediment-settling pond located at the <br />southwest corner of the site. Pump rates for the dewatering trenches are expected to be 0.1 - 0.0 ] <br />MGD. The water will be allowed to naturally seep into the Big Thompson River and a siphon <br />will account for any overflow. The de-watering effluent will be regularly sampled as mandated <br />by National Pollutant Discharge Elimination System (NPDES) protocol. Soil stockpiles will be <br />seeded and bordered by silt fences to avoid soil erosion and degradation of Big Thompson River <br />water quality. See Figure ] of Exhibit D for structure locations. <br />Coulson Excavating Company has applied for a NPDES permit from the Water Quality Control <br />Division at the Colorado Department of Health for gravel mining operations of this pit. <br />