Laserfiche WebLink
• SEDIMENT POND N0. 003 <br />The design and storage capacity and detention time of Sediment Pond No. <br />003 was evaluated to answer the concerns of the Divsion in their review <br />of the Seneca II Permit Renewal. The existing spillway will be modified <br />to meet the requirements for sedimentation ponds (4.05.6). <br />The total drainage area of Pond 003 is 30.14 acres, see Exhibit "7-7", <br />Surface Hydrology Map, Drainage Area III. For design purposes, 16.67 <br />acres is considered to be undisturbed ground and 13.47 acres is <br />considered disturbed bare ground. .The weighted curve number was <br />calculated to be 73 and the weighted "k" factor was determined to be <br />0.26 (see Table 1 and 2). The curve number and "k" factors for the <br />individual soil types were taken from Tables 7-6-1 and 7-6-2, <br />respectively. <br />The unit hydrograph type that was selected.to be used in the SEDIMOT II <br />• computer model was for a disturbed drainage condition since about half <br />of the drainage area was disturbed ground. <br />The time of concentration was calculated using the following formula <br />(Barfield et al, 1981). <br />tc = ~0.8(S + 1 0.7 <br />1140 YO <br />where L = hydraulic length of watershed = 3400 ft. <br />Y = average watershed slope = 11.0% <br />S = maximum retention <br />s = 1000 - 10 = 1000 - 10 = 3.70 <br />then tc = (3400)0'8(3.70 + 1)0'7 = 0.522 hrs. <br />1140 (11.0) '' <br />Next, a particle size-percent finer distribution of the soil type in the <br />Pond 003 watershed was determined from a soil sample taken from the <br />• reclaimed area in April of 1986. This sample was used because it <br />closely represents the watershed soils. The input particle distribution <br />is as follows: <br />7-6b-2 Revised 8/27/86 <br />