Laserfiche WebLink
CM0001644 <br />0, Page 16 <br />acre-feet impoundment downstream of the No. 1 Tailing Dam. The cost to construct this <br />impoundment is estimated to range between $780,000 to $925,000. This cost includes $60,000 <br />for placement of a grout curtain beneath the dam foundation. <br />J. This cost estimate assumes sufficient borrow areas for construction of a zoned earthen <br />embankment 30 feet high by 1,460 feet long. In addition, it is assumed that borrow area soils are <br />suitable for dam construction. <br />The time frame to construct the impoundment is approximately 38 days. This time estimate <br />assumes the soil borrow areas are in close proximity to the site. <br />J <br />F I Passive Treatment <br />-1 <br />Passive treatment of the No. 1 Tailing Dam seep water will require construction of a limestone <br />i drain. For the purpose of costing, the drain was assumed to be an oxic drain placed just below <br />the ground surface. The drain was estimated to be 1,300 feet long by 15 feet wide (at the base), <br />with a trapezoidal cross section. The trench will be lined with a geosynthetic membrane and filled <br />{ <br />with limestone. <br />The estimated cost to construct the limestone drain is estimated to range between $497,900 to <br />$590,700. This cost assumes that a sufficient volume and quality of crushed limestone is locally <br />available. The estimated time to construct the limestone drain is approximately 26 days. <br />The ultimate cost and design of the drain will require an additional detailed engineering <br />evaluation to ensure the drain is compatible with the seep water quality and seepage rate. <br />4.5 Surface Water Diversion <br />The surface water diversion is a rock-lined trench, eight feet by four feet deep, with trapezoidal <br />cross section. The diversion trench will be aligned with the existing county road. The cost of <br />constructing the surface water diversion is estimated to range between $16,400 to $20,000. This <br />cost assumes that a sufficient quantity of sized rock is available to line the diversion for erosion <br />protection. <br />The surface water diversion can be constructed in an estimated time of three days. This estimate <br />assumes the equipment is available at the site and sufficient quantities and sizes of rip-rap are <br />available in close proximity to the site. <br />OTEMAN Environmental <br />