2003-08-15_INSPECTION - M2001054

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(Page 21 MINE ID # OR PROSPECTING ID # M-2001-054 INSPECTION DATE 8/6/03 INSPECTOR'S INITIALS RCO OBSERVATIONS This inspection was performed by the Division as a follow-up to verify that problems found during the 5/7/03 inspection had been corrected. The operator was contacted about the inspection. The operator'srepresentative named on page one was present during the inspection. There was no mining occurring during the inspection, though material generated during the recent excavation of the channel and pond was stockpiled for processing and removal. No additional timber cutting appears to have been carried out since last inspection, though most of the felled trees and slash are now gone. The sediment pond and runoff channel, structures that were required to be constructed by 7/31 /03, were inspected. They were shaped by excavating sufficient pitrun material to create functional runoff conveyance and catchment structures. The structures appeared to meet the capacity requirements, and as close as could reasonably be determined, were in approximately the correct locations, as approved in the original mining plan. For these reasons, the corrective action is considered to be completed. The channel structures was functional, but was not, however, found to be constructed to its final configuration, as approved in the permit's mining plan. The channel's side slopes gradients were about 1:1. It was emphasized to the operator during the inspection that the plan requires the side slopes of the channel to be 2:1 (horizontal to verticall. The steep gradient observed is not stable in the lono term and must be reduced to 2' 1 In the final shaping of the channel the operator must ensure that the cross-sectional area of the final channel be at least that shown in the approved plan (which ensures that the capacity is not diminishedl• and that the land area occupied by the structures not eMend outside the permit boundarv. The lower end of the south edge of the channel was located immediately inside the boundary, which indicated that if the required slope reduction was carried out, the top of the reduced slope would be outside the boundary. To complete the structures, the channel slope grading must be performed as the plan specifies, and the "footprint" of the channel must be shifted far enough northward to avoid offsite damage. The toe of each wall of the channel was riprapped with rock 11 ft or larger), though none of the floor of the channel was riprapped. The sediment pond was in place, and though its sloped walls were steeper than 1.5:1, steep walls are what the approved plan allows. The capacity of the pond was estimated to be what the approved plan specified: at least 0.25 acre feet. The operator must ensure that he maintains at least this minimum repuired capacity. The final elevation at the top of the pond slopes is supposed to be the final elevation of the second bench. At present, some of the elevations around the pond margin are about 6-8 feet too high. This does not need to be changed at this time, since that would require additional excavating or earthmoving on the second bench itself, and this activity would be out of sequence with the plan. With the runoff control structures in place, the operator must finish the lower bench before commencing work on the second bench. When excavation on the second bench begins, the operator must bring the bench and pond margin down to their final elevations. The approved gradient for the pond side slopes is slightly steeper than 1:1, but the present gentler gradient is felt to be more stable, and will require less maintenance. The final pond depth in the approved plan is less than 15 feet, which is easily maintained by excavator. The pond outlet was the low point of the margin. It is presently riprapped, though the approved plan calls for two 36-inch diameter culverts. Recently submitted drawings of the site and its structures depicts the approved culverted outlet. If the operator wishes to change the culverts to a riprpapped type of outlet, an adequately engineered evaluation with revised drawings needs to be submitted for review The operator is cautioned that settino the outlet (which ever type) at too low an elevation will reduce the capacity of the pond possibly below the capacity required by the plan. The pond inlet is located at the lower end of the channel, and where the future access road enters the site on the second bench. The upper end of the secondary road has been blocked by an earthen berm, which also functions currently to help contain runoff in the channel. When the secondary road is opened, the berm will presumably be removed, but the operator must ensure that channel runoff is contained and does not run down the road or enter the bench. The recent drawings (referred to above) also included a detail about the pond inlet which is not approved in the original plan: instead of two 72-inch culverts under the top of the access road, a low water crossing with 5:1 slopes was depicted. The new detail was discussed with the operator during the inspection. This type of channel crossing by the access road appears to make more sense from an installation and maintenance prespective, since it will allow equipment access to the