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A maximum 3H:1V, eight (8)foot wide, eight (8)foot high drainage channel will be constructed <br /> from the end of the existing rip rap channel to the bottom portion of the slope as located in the <br /> field. The bottom of the drainage channel will be lined with a minimum 30" depth of riprap. <br /> Using on site materials, the riprap available on site will consist of a combination of 20% minimum <br /> 4' diameter rock, 40% minimum 2' to 3' diameter rock and 40% 12" to 18" rock. The 4' diameter <br /> rock will be keyed into the bottom of the constructed 3H:1V channel through excavation <br /> placement to not extend above ground more than 30" high and placed every 20' in slope length. <br /> The 12"to 18" rock will be placed and compacted into the bottom of the excavated channel. The <br /> 2' to 3' diameter rock will then be placed over the smaller rock to fulfill the 30" minimum riprap <br /> depth requirement. Placement will be such that voids will be eliminated to the best extent <br /> possible with rock contacting rock. Side slopes to the constructed channel will be at a maximum <br /> 3H:1V slope. Side slope riprap will extend up the sides of the constructed channel to a minimum <br /> 4' height. <br /> Material excavated as a result of drainage course construction may be: excavated and hauled to <br /> or graded against the excavated bench cuts as noted on the drawing. Prior to depositing or <br /> grading excavated material against the excavated bench cuts, existing vegetation and soils to a <br /> 24" depth will be graded off and stockpiled. Stockpiled vegetation and soils will be evenly <br /> redistributed over the deposited material from drainage course construction upon completion of <br /> earthmoving procedures. <br /> If any trash is encountered during excavation for channel construction, trash will be hauled off to <br /> the nearest County approved landfill site. <br /> Measurement and Payment <br /> There will be no measurement for payment of Task 4, Drainage Repair and Construction. <br /> Payment for this Task will be reflected in a lump sum bid under Item 4 on the Bid Schedule. <br /> This lump sum bid will cover all costs for excavating, hauling, placing and placing the riprap <br /> material as described in these specifications. <br /> Task 5 <br /> Portal Repair and Rock Apron <br /> The mine portal area backfill extends up against the sandstone outcrop. Water upgradient of <br /> the portal is flowing into an existing channel and creating an opening between the bedrock and <br /> fill material. The opening will be further excavated to determine the extent and depth of the hole. <br /> The portal will be filled, compacted and armored with 18" to 24" of rock. Upon further exposure, <br /> the hole may be filled with on site material or a Polyurethane Foam Plug (PUF) in accordance <br /> with Specification 9 of the General Bid Specifications, Colorado Inactive Mine Reclamation <br /> Program, 2006. The PUF must be covered with minimum 3 feet cover using onsite fill material. <br /> Use of PUF is not guaranteed. A rock channel apron will need to be installed over the repaired <br /> hole to deflect the water from the intersection of the over the fill. The rock apron will be <br /> constructed using on-site rock material 18" to 24" in size. The rock apron shall be approximately <br /> 5 feet wide, 10 feet long and 3 feet deep and keyed into the surrounding material to a depth of 2 <br /> feet on both sides of the apron. <br /> Measurement and Payment <br /> There will be no measurement for payment of Task 5, Portal Repair and Rock Apron. Payment <br /> - 9 - <br />