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, •• Ms. Lori Potter t~ • <br />Project No. 9974-01 <br />Page 2 <br />December 30, 1999 <br />Unfortunately, we have not had an opportunity to inspect the "constructed basin." However, the <br />DMG 6/4/99 inspection report indicates "The amount of material that was collected in the <br />constructed basin is several feet thick over 1-2 acres." No mention is made of water contained in <br />the constructed basin that leads us to believe that water was drained from the system or <br />evaporated. We do not believe sufficient time exists between May 2, 1999 to June 4, 1999 to <br />evaporate contained waters. Thus, we have to conclude that runoff and sediment discharged from <br />the "constructed basin" during and after the April and May 1999 storm events. <br />Mr. Dillie's Seventh Paragraph <br />We agree that the amount of sediment captured by a sediment pond is dependent upon how long <br />the water remains in the structure. Unfortunately, we have not reviewed any DMG material that <br />demonstrates adequate retention time existed for this qua-ry sedimentation pond. Besides, the <br />sediment pond had failed during the April and May 1999 storm events. Since "high velocity" <br />dischazge conditions existed through the breach embankment area, the retention time (if any) must <br />have been minimal. Hence, we continue to support our opinion that little capture of sediment <br />occurred during the April and May 1999 runoffevents. <br />In addition, it has not been conclusively demonstrated that the "backsloped area" did not <br />discharge runoff over the containment swales. Thus, we continue to believe that significant <br />amounts of sediment from the backsloped area also dischazged onto downstream properties. <br />Mr. Dillie's Eighth Paragraph <br />It is our understanding that when DMG complete their inspections, stormwater violations are to <br />be immediately reported to the WQCD for enforcement. Since DMG is still responsible for <br />inspections, they cannot ignore their obligation to ensure stringent sediment and erosion control <br />practices are implemented. It should also provide regulaz (at least annually) status reports to the <br />WQCD for possible enforcement action. <br />Stockpile Areas <br />Mr. Dillie's 6/4/99 inspection report does not discuss what happens to runoff patterns from the <br />processed material stockpile area. A 1993 aerial photograph illustrates significant amounts of <br />stockpiled material existed within the quarry site. We assume that during the 1999 storm events, <br />similar stockpiling of quarry material also occurred. Such areas are subject to high erosion rates <br />and large sediment yields when significant storm events occur. <br />Runoff from the stockpile areas is assumed to have had to flow towazd the sediment pond. As <br />reported by the DMG 6/4/99 inspection report, a breach of the pond embankment had occurred <br />during the April and May 1999 storm events. Thus, runoff and sediment from the stockpile area <br />must have discharged onto downstream properties at the same time. <br />Summary <br />Nothing that has been presented by DMG makes us conclude that the quarry site is not a major <br />source of sediment onto downstream properties. We continue to believe that the major <br />contribution of sediment onto downstream properties during the April and May 1999 storm <br />events was from the quarry. We also continue to believe that these conditions will occur with <br />