Laserfiche WebLink
1 <br />j~5 A statement of pertinent professional observations and conclusions made donne the rnmpletion of the <br />ttrt10®tion. <br />' The condition of the pond appears to be little changed over the pazt year. There were no indiptions of <br />structural weakness, erosion, or 6aaardotu conditions. Conclusions include an apparent requirement for <br />removal of aavmulated sediments. However, changes have been made in the reclamation plan that might <br />' reduce the anticipated runoff from a 10-year, 24hour storm attributable [o Pond 002, and permit the <br />accumulation of greater quantities of sediment Recommended minor maintenance includes: compaction of <br />gopher bttrrows (all apparently shallow); uncover, backfill and companion of prairie dog burrows; and <br />' reseeding of bare areaz. The lack of legible markings on the gage stake in the pond is not a serious detriment. <br />Levels of water and measurements of sediments were determined by cursory survey methods. For efficiency, <br />and complete compliance with the permit, the placement of two gage stakes haz been suggested. <br />' j~ A statement of tumpllantt with the prudent stateof-the-art. <br />The pond is in compliance with the prudent stateof-the-art. <br />' 7L1 A statement of mmplientt with the approved mine plan and centtit, specifically referencing appropriate <br />portions o[ the cermit documents (plans, maps and text). <br />' With respect to Permit topics found in Section 2,05.3 (Operation Plan -Permit Area); Ponds, impoundments <br />and Diversions (page 2.05-2, Rev.3-1-94; and page 2.05-3), specific observations include: <br />' Location In compliance (Drainage Control 1993 Reclaimed <br />Areas, Map 8, 10-20-91). <br />Design and construction This certification is limited to the maintenance and <br />operation of existing sedimentation ponds, not <br />design and construction This certification is based <br />on the Sedimentation Pond As-Built, 7-7-91, Rev. <br />' 1, and other information found in Exhibit 7 of the <br />Permit. <br />' No markings were seen on the gage stake set to <br />monitor sediment levels in this pond. <br />' Capacity The capacity of the pond, from the bottom of the <br />pond to the nest of the principal spillway, is 26 <br />ane-feet (Sedimentation Pond As-Built, 7-7-91, <br />Rev. 1, and Greystone letter of October 8, 1990 <br />' (from the bottom of the pond to the principal <br />spillway invert). This 23 acre feet supersedes the <br />1.76 acre feet (Area E @ 0.44 + Area F @ 0.50 + <br />' Area G @ 0.39 + Area H @ 0.35 + Area 002 @ <br />0.08) by Exhibit 7, Calculations, undated. A runoff <br />(10-year, 24hour event) of 23 aae feet <br />' (Greystone letter, October 8, 1990) leaves 0.3 aae <br />feet for sediment storage (less than the 0.5 aae <br />feet of Greystone letter, July 31, 1990). The <br />volume of sediment in the pond at the time of the <br />' 4th quarter inspection was estimated at 0.6 aae <br />feet, exceeding both allowances. Recommend that <br />' Chimney Rock Mine Pond #002 Inspection Report & Certification, 18 November 1994, Page 5 of 6 <br /> <br />