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Musick, Jason <br />From: Gorham, Kent <br />Sent: Tuesday, June 23, 2009 2:27 PM <br />To: Musick, Jason; Hernandez, Daniel <br />Cc: Talvitie, Marcia; Brown, Sandy <br />Subject: RE: Trapper PR-06 Adequacy <br />Jason, I have completed my review of the surface runoff calculations for PR-6 for the Trapper Mine. <br />My understanding is that the fill is excess spoil and meets the definition of a valley fill. Therefore, the following rules <br />apply with regard to surface drainage and were part of my review. <br />4.09.1(1)(a) The applicant's proposed plan will minimize the effects of surface runoff from the fill to surface and ground <br />waters <br />4.09.1(5) The applicant proposes to riprap or revegetate all ditches upon completion of construction. Ditches are sized <br />to the 100 year event as required by Rule 4.05.4. Artificial channel roughness is necessary to control erosion. <br />4.09.2(4)Terraces to direct drainage to the downdrains are proposed and necessary <br />4.09.2(5) By use of terraces, drainage is not directed over the outslope. <br />4.09.2(7) the proposed ditch system was designed using the 100-year, 24-hour storm event. Ditches as proposed appear <br />to ensure compliance with this Rule. <br />SEDCAD design input parameters are accurate and reflect a worst case runoff condition (i.e. during construction). <br />Hydrology calculations appear accurate and are reasonable estimates of storm runoff for the given situation. <br />As we discussed, during the period of construction, the ditch system will evolve over time to the final configuration. It is <br />up to the applicant to ensure that water is diverted away from the fill and FROM the fill in temporary ditches of <br />adequate size until the final configuration is achieved. This will likely occur through the use of temporary and <br />permanent ditches as the fill expands. <br />This completes my portion of the review. If you have any questions, please let me know. <br />From: Musick, Jason <br />Sent: Wednesday, April 01, 2009 10:33 AM <br />To: Hernandez, Daniel <br />Cc: Talvitie, Marcia; Gorham, Kent; Brown, Sandy <br />Subject: Trapper PR-06 Adequacy <br />Dan, <br />I have communicated with Marcia that due to the fact that I will be in training on Friday 4/3 and OSM training next week <br />4/6 through 4/10, 1 will send out adequacy comments on Thursday 4/2 in order to meet the April 10 deadline. My <br />comments will reflect adequacy concerns which I have been reviewing along with questions that Kent may have up to this <br />point. I mentioned to Marcia that Trapper is in the process of submitting comments based on the March 3`d preliminary <br />adequacy question and March 17th follow-up meeting. Trapper will be informed that this adequacy will not contain all <br />adequacy questions that the Division may have due to the Trapper submittals that have yet to be received. <br />Thanks