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Ta sk 3 <br />Rock Check Dam Construction: <br />Rock Check Dams are required in three areas; along the access road, on the portal bench and <br />the outslope of the fill. See drawing for locations. The rock will be collected by the <br />CONTRACTOR at a location specified by the PROJECT MANAGER. Rock check dams shall be <br />installed as follows: <br />Access Road Small erosion features extend down the. slope approximately 200 feet. <br />Install a rock check dam every 20 feet as directed by the Project Manager. Rock check <br />dams shall consist of 18" to 24" diameter rock using on site material. Rock check dam <br />dimensions will be 3' long by 3' wide by 2' deep at the base of the dam and will be keyed <br />in to a depth of 2' below ground surface. Placement will be such that voids will be <br />eliminated to the extent possible with rock contacting rock and smaller rock used to fill <br />any voids. <br />• <br />Portal Bench- One large erosion feature extends down the graded portal slope for a <br />distance of approximately 50 feet. Rock check dams will be installed every 10 feet as <br />directed by the Project Manager. The Rock Check Dams will be constructed according to <br />the attached Drawing 2. Drainage Course Rock- Rock Outcrop to Slope and Check Dam <br />X- Section & Plan Rock check dam rip rap, available on -site will consist of an evenly <br />distributed <br />combination of 60% minimum 4' diameter rock rip rap, 20% 2' to X foot <br />diameter rip -rap and 20% 12" to 18" rock. The 4' diameter rock will be keyed into the <br />bottom of the constructed 3H:1 V channel, and should not extend more than 30" above <br />f <br />ground level. The 12° to 18° rock will be placed and compacted around the 4' diameter <br />.-- 3 <br />rock. The 2' to 3' diameter rock will then be placed over the smaller rock to fulfill the 30° <br />minimum dprap depth requirement. The check dam will be constructed in a V -shape with <br />the middle of the V situated 4' in slope length, up stream in elevation. Rip rap will extend <br />a minimum 4' up the side slopes. Side slopes to the constructed channel will be at a <br />N <br />maximum 2H:1V slope. Positive drainage will be maintained from the bench cut into the <br />drainage channel. See Drawing 2 for more detail. <br />S(' G • s <br />Fill Outslope- Small erosion features extend down the slope approximately 100 feet. <br />Install a rock check dam every 20 feet as directed by the Project Manager. Rock check <br />dams shall consist of 18 n to 24 using on site material. Rock check dams will be 3' long <br />by 3' wide by 2' deep at the base of the dam and be keyed in to a depth of 2' below <br />ground surface. Placement will be such that voids will be eliminated to the extent <br />- possible with rock contacting rock and smaller rock used to fill any voids. <br />Lt' ✓D` <br />lK �; Measurement and Payment <br />Measurement for payment will be accomplished by counting the number and type of rock check <br />dams constructed and accepted by PROJECT MANAGER. Payment will be made at the unit <br />p f f prices established in the Bid Schedule for Items 3a, Road / Fill Outslope Check Dams, and 3b, <br />t e Mtw Portal Bench Check Dams. The unit prices established in Items 3a and 3b of the Bid Schedule <br />will !be considered full compensation for all costs and expenses, necessary and incidental, to <br /> �a construct the check dams as described, including excavating, hauling and placing the rip rap <br />material. <br /> s r- <br />MW r� <br />6 <br />