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<br />~, <br />Mr. Dean Massey - 2 - February 10, 1992 <br />• 6. In the permanent pond demonstration for Pond 4 it is Stated that the <br />emergency spillway will be lowered to 7545.2 ft., yet design plans show <br />the top of the 10-year, 24-hour event cresting at 7547.5 ft. Lowering the <br />elevation of the emergency spillway would not allow for treatment of the <br />required 10-year, 24-hour event. An alternative would be to add a riser <br />to the principle spillway at 7545.2 ft. which would allow the pond to <br />dewater to the 2 acre-ft limit, yet maintaining the proper elevation for <br />the open channel emergency spillway, and retain most of the detention time <br />for the 10-year, 24-hour event. Please provide revised plan details which <br />satisfy both the water rights issue and compliance with Rules 4.05.6 and <br />4.05.9. <br />7. There were no SEDCAD runs for Pit 5 drainage structures depicting the <br />25-year, 24-hour event, other than a cover page. Please provide these <br />calculations. <br />8. The slides numbered 1, 3, and 4 do not seem properly located on the slide <br />map contained in the report titled "Response to Stipulation No. 12". <br />Please correct this discrepancy. <br />9. What type of filter blanket is to be used under the road crossings? <br />10. The postmining sediment yield values for Pit 2 and Pit 3 are well in <br />excess of the premining values, although the volume of sediment is <br />• relatively small. Based on Section III Z.a. of the June 26, 1990 <br />Settlement Agreement, those sediment ponds and the associated drainage <br />control can only be removed after compliance with Rule 4.05.2 has been <br />demonstrated. Rule 4.05.2 requires ponds to remain until the disturbed <br />area ceases to contribute additional suspended solids above natural <br />conditions and the quality of untreated drainage meet the State and <br />Federal water quality standards for receiving streams. We therefore <br />cannot approve pond removal at this time. <br />Pond removal is still considered to be a task which should occur. Several <br />options may be used. First, Rockcastie may want to allow further <br />vegetation establishment, then attempt a revised sediment yield <br />demonstration at some time in the future. Second, if Rockcastle does not <br />want to commit to any work beyond 1992, then we will need to retain some <br />amount of additional bond money to allow the Division to complete the <br />job. Finally, we believe that part IV.3.a of the Settlement Agreement may <br />provide some flexibility in designing appropriate alternate sediment <br />control systems at Pits 2 and 3. Such an alternate plan must comply with <br />Rule 4.05.5, and it will be necessary to show that the alternate system <br />would provide treatment of disturbed area flow sufficient to ensure <br />compliance with the existing effluent limitations. Please provide your <br />plan to address this issue. <br />• <br />