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<br />In response to Stipulation No. 16 of the PROPOSED DECISION AND FINDINGS <br />OF COMPLIANCE dated October 18, 1864 the eight culverts at station <br />31+50 of the Northern No. 1 haul road is designed to pass the 10 year <br />24 hour event. <br />Rs per the attached calculations at a maximum head of 1.5 feet tas <br />actually measured by HaIIK Coufos) the eight 36 inch culverts will pass <br />357 cubic feet per second. In appendix R of the mine permit <br />?~F•Plication Espey, Huston b Associates, Inc, state that the peaK flow <br />or worst case for the 10 year 24 hour event Ss 310 cfs. This 1s <br />ai suming 0 discharge from thle sedimle ntat ion pond. Therefore the <br />culverts have an excess capacity of 47 cfs or 15%. This is cell within <br />engineering tolerances. Even if the Northern No. 1 Sedimentation <br />Pond's gate valve is opened to allow continuous discharge with an <br />average retention tinx of 24 hours the peaK flow is Increased by only <br />0.14 cfs. <br />• The peaK flow from the disturbed -area again according to appendix A of <br />the EsPey, Huston ~ Associates, Inc. report is 9.6 cfs. Rssuming after <br />reclamation that the sedirrrentation pond is removed the peaK flow <br />thlrough the eight culverts during a IB year 24 hour event will be <br />~F~proximately 320 cfs. The culverts still have an over cap is ity of 37 <br />cfs or 12%. This is still with in acceptable engineering tolerances. <br />r <br />~.• <br />1 hereby certify that these calculations and statements are correct <br />within the confines of the accuracy of the data provided by Northern <br />Coal Company. <br />R. Troy WS11s,P.E. <br />_.`~11~111111111II III~'F,, <br />~'~~~~~~41 E~ f~f+=, <br />Oatg . - . , ~ /fir ~ ~: <br />:~ ! l <br />5 <br />C-yb Q <br />/ ~/ /~/~ <br />