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Response to DRMS Adequacy Review (2) -Cotter SR -11 Mine Reclamation Plan Amendment <br />Cotter Corporation (N.S.L.) (Cotter) submits this response to the comments attached to the April <br />25, 2013, letter from Stephanie Reigh, Division of Reclamation, Mining and Safety ( "DRMS "), <br />to Glen Williams, Cotter. The DRMS' comments are in italics and Cotter's responses are in <br />bold. <br />1) Page ESWMP -3, Section 4.3 — Existing Stormwater Structures. The DRMS is concerned <br />about erosion and capacity of the existing stormwater structures within subbasin Onsite 30. <br />The satellite image from Google Earth is surprisingly sharp for this area. The Google Earth <br />image in Attachment A shows significant rill and gully erosion below the toe of the east side <br />of the waste rock pile as well as some erosion in a drainage swale flowing from the west end <br />the waste rock pile to the retention pond. The second paragraph discusses a "rock -lined <br />channel along the flank of the waste rock pile" and a "small drainage swale located below <br />the toe of the waste rock ". There appears to be incised channels paralleling the inside of the <br />existing berm on the west, and both south sides as runoff is directed to the retention pond. <br />a. Please label both the aforementioned rock -lined channel and small drainage swale on <br />Sheet 1 of 4, Site Drainage & BMP's, Drainage Design Plan. <br />The "rock -lined channel" mentioned in the original Drainage Design Plan refers to <br />a channel which drops from the upper area, where waste rock is currently <br />stockpiled, into the lower area where some waste rock has been spread, and where <br />future waste rock is proposed to be stockpiled once mining activities resume. This <br />channel is heavily fined with large rock and is now labeled on the revised drawing <br />Sheet 1 contained in Attachment #4. The "small drainage swale" discussed in the <br />report refers to the open channel which runs diagonally from the bottom of the <br />upper area to the existing retention pond. This channel receives flow from the <br />previously discussed "rock -lined channel" and was installed during initial mining <br />operations to intercept runoff from the upper area and route it directly to the pond. <br />It is labeled as an interceptor channel on Sheet 1 of the revised drawings in <br />Attachment #4. <br />b. Please include new BMPs to reduce the rill and gully erosion observed on the east <br />portion of the site below the waste rock pile. <br />Scarification, by disc or other means, is proposed for the area containing the rills in <br />the southeastern portion of the site below the waste rock pile. It is shown on the <br />revised drawing Sheet 1 to be scarified, by disc, in the direction of the contours to <br />break up the rill erosion and to provide additional benefit by producing a more <br />absorbent area for the onsite basin. Any soils that may be eroded will be caught at <br />