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378-10 Pond <br />EMBANKMENT POND SPECIFICATIONS <br />Foundation preparation <br />The entire area upon which the dam <br />will rest shall be cleared of <br />trees, logs, stumps, roots, brush, <br />boulders, sod, and rubbish. If <br />needed to establish vegetation, <br />the topsoil and sod shall be <br />stockpiled and spread on the <br />completed dam and spillways. <br />Foundation surfaces shall be <br />sloped not steeper than a ratio of <br />one horizontal to one vertical. <br />The foundation area shall be <br />thoroughly scarified before <br />placement of the fill material. <br />The surface shall have moisture <br />added, or it shall be compacted if <br />nscessary so that the first layer <br />of fill material can be compacted <br />and bonded to the foundation. <br />The cutoff trench and any other <br />required excavation shall be cut <br />to the lines and grades shown on <br />the plans or as staked in the <br />field. A cutoff trench having a <br />bottom width of not less than five <br />(5) feet and a minimum deoth of <br />four (4) feet the entire length of <br />the dam shall be required on all <br />dams. If they are suitable, <br />excavated materials may be used in <br />the permanent fill. existing <br />stream channels in the foundation <br />area shall be sloped no steeper <br />that a ratio of one and one-half <br />horizontal to one vertical. They <br />shall be deepened and widened as <br />necessary to rertiove all stones, <br />gravel, sand, stumps, roots, and <br />other objectionable material and <br />to accommodate compaction <br />equipment. <br />Foundation areas shall be kept <br />free of standing water when fill <br />is placed on them. <br />• <br />Fill placement <br />Borrow material may be taken from <br />within the water storage basin as <br />long as the following conditions <br />are met: <br />1. The bottom of the excavated <br />area is~parallel to the slope of <br />the stream or natural channel, and <br />the bottom of the cutoff trench <br />under the dam is at least four <4) <br />feet deeper in elevation-than the <br />lowest point within the excavated <br />area. The excavated slope shall <br />not be steeper than three <br />horizontal to one vertical. <br />2. Exposed pervious layers within <br />the ponding area shall be <br />blanketed with two (2> feet of_ • <br />compacted impervious material. <br />3. The storage capacity to the <br />bottom o` the emergency spillway <br />does not txceed ten acre-feet; <br />except for erosion control dams <br />where the storage below an unaated <br />outlet shall not e>:ceed two acre- <br />feet. <br />Otherwise no material may be <br />borrowed within SO-feet of the dam <br />embankment unless supported by an <br />adequate foundation investigation. <br />The material placed in the fill <br />shall be relatively free of sod, <br />roots, frozen soil, stones more <br />than 6 in. in diameter (except for <br />rockfills>, and other undesirable <br />material. <br />• <br />SCS, Colorado, January 1989 <br />