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<br /> <br /> <br />1 <br />1 <br /> <br /> <br />i' <br /> <br /> <br /> <br />r <br /> <br />1 <br />1 <br />1 <br /> <br />5. Standard soils loss equations (such as USLE) are not applicable to mining/ <br />heavy disturbances. Sediment losses from various sources were researched <br />to find sediment loss numbers applicable to mining situations. No papers <br />were found listing sediment losses from mining, but an excellent article <br />on sediment losses from heavy highway construction was found which should <br />be indicative of sediment losses during rainstorms from mining conditions. <br />The referenced article is "Effectiveness of Sediment Control Techniques <br />Used during Highway Construction in Central Pennsylvania", by Lloyd A. <br />Reed, 1978. It is USGS Water Supply Paper H2O54. The article states <br />that runoff from five basins (1, 2, 2A, 2B, and 3) was measured during <br />highway construction. Basin 2A appeared to be most similar to the mining <br />activity at the Grassy Gap Coal Mine. Basin 2A included 4.5% disturbance. <br />The remaining 95.5Y of the drainage area was undisturbed grass and forest <br />land. That article stated that the highest average storm-runoff occurred <br />during early earthwork and was 210 mg/1 (page 19). Assuming no sediment <br />runoff from the undisturbed areas, this implies that the sediment load <br />from the disturbed area was 4667 mg/1 (210/.045). <br />Pages 36-41 of the article are enclosed. A diagram of the disturbed areas <br />at Basin 2A is shown on page 36. The east offstream sediment pond received <br />runoff from a construction area of 8 acres (no undistrubed acreage). Thus <br />sediment measurements from the east offstream pond should be typical of <br />sediment loads from heavily disturbed construction-type areas. Page 40 <br />states that the sediment load in the east sediment pond (after displacing <br />the clean water) was 1,800 mg/1 just after a storm. <br />Therefore, an estimate of 10,000 mg/1 sediment runoff from disturbed areas <br />at the Grassy Gap Mine is probably a fairly realistic number. If anything, <br />it may be conservative. <br />XIII. No response required from The Rockcastle Company at this time. ~~10"~ <br />XVI. The Rockcastle Company uses explosives on the average of once per day. <br />Publication in the Steamboat Pilot notifies the public that blasting occurs <br />once daily at the mine between the hours of 8 & 5 (daylight hours). A shot <br />pattern similar to the enclosure is used. Records of each shot are main- <br />tained on file at The Rockcastle Company's office in Steamboat Springs. <br />-3- <br />