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Section 780.21(c) Continued. Rule 2,05.6(3) <br />' Revised 12/3/80 <br />east. Coal dust blown onto the adjacent lumber mill will have no <br />immediate hydrologic impact, because the mill is located on a <br />terrace above the Illinois River floodplain. The minor amounts of <br />coal dust which may settle onto the adjacent wet lands to the east <br />of the tipple area have not had any quantitative effect on water <br />quality to date, as shown in Table 10, Kerr Tipple Area Water <br />Quality Data. The only effects of coal dust emissions to date have <br />been a noticeable film on the surface waters in the marsh imme- <br />diately east of the area of operations. There has been no ob- <br />servable occurrence of coal dust to date in the wildlife refuge to <br />the south of the Kerr Tipple Area. The continuing hydrologic <br />monitoring program proposed under Section 780.21 (b) will be ade- <br />quate to observe any effects of operations at the Kerr Tipple Area <br />on surface water quantity and quality. <br />Sedimentation Pond Detention <br />Historical data on surface water quantity 1n the proposed permit <br />and adjacent area is limited. The most complete record of surface <br />water runoff in the intermittent draws draining the proposed permit <br />area are from U.S.G.S. Gaging Station No. 06619420 on Williams <br />Draw. Data on water quantity at this station is graphically shown <br />on Figure 7, Kerr Mine Area Surface Water Flow Hydrographs. Inte- <br />grating the area under the hydrograph, the total amount of snowmelt <br />runoff in Williams Draw in 1980 was 5.8 acre-feet. Assuming this <br />is the normal amount of snowmelt to be expected from the 2,165 acre <br />watershed tributary to USGS Gaging Station 06619420, the average <br />yield of snowmelt water would be 2.7 x 10-3 acre-feet per acre. <br />Williams Draw, as well as the other three intermittent draws drain- <br />ing the proposed permit area, is usually dry except for snowmelt <br />and occasional storm runoff. For the purpose of this analysis, an <br />assumed annual yield of 0.003 acre-feet per acre will be applied to <br />the entire proposed permit area. <br />780-126 ddd <br /> <br /> <br /> <br />