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Here the trap efficiency is 94.7% , and it releases water with settleable solids concentration of <br />0.00 ml/1, well below the 50 ml/l standard. As with the above described square transformer pad, <br />the result is also achieved if the grass filter is only 10 feet long by 1,000 feet wide. <br />Finally a 300 foot wide by 1,000 foot long disturbed area of 6.89 acres was modeled with CN 85. <br />This produced a flow in the 10 year 24 hour storm of 5.02 cfs distributed along the 1,000 foot <br />boundary with the down -gradient grass filter. This model was run with the grass filter sloping at <br />50%, and thus should be considered the most severe application of this approach. The first 20 <br />feet of flow through the grass filter reduced the 24 hour weighted settleable solids to 0.35 ml/1, <br />which satisfies the 0.5 ml/l standard. This grass filter has a trap efficiency of 80.4 %. <br />For the broad range of disturbances evaluated, the settleable solids standard is reached in the first <br />20 feet of flow through the undisturbed vegetated land. <br />SEDCAD Models used in this Part H <br />Ditch models: <br />• Exh. H generic triangular ditch <br />• Exh. H generic trap ditch <br />Vegetated (Grass) Filter models: <br />• Exh. H Generic GF 100 x 100 pad <br />• Exh. H Generic GF 100 x 1000 linear <br />• Exh. H Generic GF 300 x 1000 <br />References <br />1) Applied Hydrology and Sedimentology for Disturbed Areas, Barfield, Warner and Haan, 1981 <br />Exh. 7-23H-3 Revision Date: 11/09/15 <br />Revision No.: PR -04 <br />