Laserfiche WebLink
<br />-2- <br />Division Calculations <br />My SEDCAD+ run consisted of using a CN <br />weighted CN C49) based on the vegetati <br />consisted of the area designated to be <br />1992-1996. No assumption was made for <br />results show 174 cfs peak Q (MLRD) vs. <br />image, the pond appears undersized. <br />of 87 <br />m Map <br />mined <br />the p <br />6 cfs <br />for disturbed acreage and a <br />No. 4. The disturbed area <br />in the watershed between <br />its intercepting runoff. My <br />Q (operator). As you might <br />Recommendations <br />My recommendations to the operator would be as follows: <br />The use of one CN is unacceptable. Other mines in the same general <br />area have gone through detailed investigations to establish <br />reasonably accurate CN's based on real data rather than <br />generalizations. Additionally, the investigation led to no less <br />than 5 land conditions (or CN's), rather than one. The operator <br />should submit data to support curve numbers which represent actual <br />land surface conditions during "worst case" mining to insure proper <br />pond sizing. <br />2. Other mine sites who have approved curve numbers do not account for <br />the pit intercepting runoff and size their ponds accordingly. If <br />the operator wants to account for the pit intercepting runoff then <br />data and appropriate maps should be provided which indicate the <br />areas from which runoff would not reach the pond. Also, if any <br />such plan is approved by the Division, the operator should be aware <br />that they would be in violation of their permit if specified areas <br />were bypassing the pit and draining to the pond. <br />Overall, this submittal is not acceptable in its current form. I would <br />recommend that the operator forget about using generalizations and opinions to <br />support their calculations and instead provide all necessary data to show <br />proper design. Many points are made to support their parameters then <br />referenced to give the impression their design is "very, very conservative." <br />On the contrary, I believe their model is not appropriate nor based on <br />scientific data and given the location of the state highway, I strongly <br />disagree with their approach. Also, the permanent ditches are represented as <br />having no protection in may areas which clearly need it. This should also be <br />addressed during the extended review. If you need details, please see me, but <br />for the reasons outlined above, it would not be prudent to continue a review <br />until the operator and the Division can reach agreements on the above points. <br />KAG/eke <br />3102E <br />