2018-02-07_PERMIT FILE - M1981148 (8)

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Review of post-1990 planning documents related to drainage and prepared for Solterra show that water run-on and off from the mine was not considered, except for pre-1939 drainage patterns (Carroll, 2006a,b), (JSC, 20013a,c,d; 2015). Carroll does show contours across the face of the mine but it appears to this commentator that they don't reflect the effect of mining operations'. There is one exception by Jansen Strawn (JSC, 2013b). DR11 of DR12 shows JSC's Final Drainage Plan for the southern half of the mine. This drawing shows JSC's"proposed major basin boundary" and "proposed basin boundaries". What is interesting is the JSC is making projections on how JSC is going to handle drainage on General Shale's property. The map does show the existing inner channel and the direction of flow with arrows. The outer ditch is evident when evaluating contour shape but JSC seems not to have recognized that there is a channel there. In fact,one of their proposed drainage basins (middle one)crosses this drainage pathway. That pathway carries water to the southeast corner of the mine and beyond. Not only did JSC miss the channel,they did not evaluate where the water might be coming from. General Shale is coordinating with Solterra and the City of Lakewood to redesign the existing stormwater conveyance system on the mine property. In a meeting with Lakewood on February 17, Lakewood indicated that it has no formal role in the design or approval of the stormwater drainage since the mine is being operated under a DRMS (DNR) permit. In that same meeting, General Shale and Lakewood agreed that General Shale would provide the City of Lakewood with a preliminary drainage study and design drawings, and the City would review these and provide technical feedback. HMD and General Shale would consider this feedback and provide a final drainage study with drawings to the City of Lakewood. If acceptable,the City of Lakewood would provide a letter to General Shale that the stormwater design meets the City of Lakewood engineering standards. Hydrology Urban Drainage and Flood Control District(UDFCD 2016) recommends the use of the Colorado Urban Hydrograph Procedure (CUHP)for watersheds that are greater than 90 acres in size. The pre-1939 watershed area above the SW corner of the mine where the arroyo exits mine property is approximately 293 acres (0.456 square miles). Therefore,the CUHP will be utilized in this analysis. UDFCD recommends further that the storm be routed Utilizing EPA's Stormwater Management Model (SWMM). Accordingly, EPA's SWMM is being used in this analysis to evaluate the effect of the timing of sub basin 'This statement is based on the Carroll reports that were received by HMD from the City of Lakewood. However, JSC(2013a)has a drawing that purportedly came from the Carroll reports. This drawing shows a full contour set with evidence of mining operations. In this drawing,the arroyo appears intact. Why the Carroll reports(assuming JSC is correct)show three different treatments of the mine from a contour map viewpoint within the space of three months is unclear. 3 07/30/2017