Laserfiche WebLink
BACKGROUND INFORMATION AND RESULTS OF FIELD INVESTIGATIONS <br />General Description of Current Conditions <br />The location of the seepage area with respect to No. 3 Dam and the Grand <br />County Road 3 is depicted on the attached Drawing No. 3DS-1. The geometry and <br />terrain of the seepage area to be mitigated is shown on Drawing No. 3DS-2, Detail 1. <br />Unaffected drainage is shown on that detail with light blue shading. <br />The area was surveyed by Steffens & Associates, Inc. in 2009 with a Total <br />Station to provide topographical control data for the design. 1 he locations OT <br />predominant points of seepage were also recorded and are shown on Drawing No. 3DS- <br />2. Four seepage points (Seep 1 through 4) and two lines of seepage (Seep 5 and 6) <br />were identified and are shown with their exit point elevation. <br />A CMP drainage culvert from the west side of the county road discharges near <br />Seep 1.. The flow through the culvert is ephemeral and only occurs during snow melt <br />and after rain events. <br />'The seepage flows across the remnants of an old irrigation ditch and into a flat <br />area where a small non-jurisdictional wetland has developed. No hydrologic connection <br />or other nexus between the wetland and the tributaries of the Williams Fork River exist. <br />Hence it is truly isolated and does not fall under Section 404 jurisdiction. <br />North of the seepage, and generally aligned with the 8720 contour is the corridor <br />of the abandoned ditch that crosses an open area and ends at the county road <br />embankment. Directly across the county road is the No. 3 Dam Seep Water Pipeline, an <br />Environmental Protection Facility constructed in 2000. A buried pipeline from the <br />abandoned ditch, across the road, and connecting to the Seep Water Pipeline near the <br />clean-out risers provides a simple method to deliver the seepage into the Henderson <br />Seep Water System. <br />The main issue of the collection system design is how to convey the seepage <br />into the seep water pipe by gravity, thus not requiring pumping. <br />Henderson Operations, Mill Site 9/7/10 <br />No. 3 Dam Seep Mitigation, Design Report Page 2