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BMP: BERMS AND DITCHES <br />1. METHODS: A berm is a ridge of compacted soil. A ditch is a small <br />drainage way. Both of these structures have similar purposes. Berms and <br />ditches should be used: <br />? Above disturbed slopes <br />? Around graded areas (to keep clean runoff out and to contain <br />sediment-laden runoff within) <br />? Along slope benches <br />? Above leach fields when required. <br />The most common use of berms and ditches is to divert upland runoff away from <br />exposed soil to a protected outlet (such as an infiltration trench, storm drain, or <br />stable channel). When a berm or ditch is used to contain runoff from a <br />disturbed area, you must route the sediment-laden water to a sediment trapping <br />device (see section on sediment basins). <br />The following method should be used to construct a berm: <br />A. Deposit a ridge of soil about 18" high with a shovel or backhoe. <br />B. Compact the soil by rolling or tamping until it has the dimensions <br />shown. <br />C. Vegetate permanent berms with installation of an erosion control <br />blanket. <br />The following method should be used to construct a ditch: <br />A. If the drainage area to the ditch is 1/4 acre or less, dig the channel <br />8" deep. If the drainage area is 1/4 to 2 acres, dig the channel 12" deep. <br />Deposit the excavated soil where it will not wash into a drainage way (such as <br />on the downhill side of the ditch). <br />B. Compact the channel by tamping or rolling. <br />8 <br /> <br />60MPP17