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p tb NOV C-97-1~l-ATTACHMENT CRDA_2 1. Near the end of Terrace Bench Drain #4, just above the juncture with East Collection Ditch, water overtopped the terrace drain, eroded a gully 4' deep, 5' wide, and lo' long through the toe of the bare refuse slope. A segment of the East Collection Ditch a short distance below the blowout filled in with refuse sediment and the ditch overflowed. A rilled flow path 8-10 feet wide, with individual rills 4-6 inches deep extended down the undisturbed hillslope approximately 150 feet to an ephemeral drainage. Avery minor amount of coaly debris had been deposited along the flow path. A 60 foot segment of the perimeter ditch beginning approximately 50 feet below the junction with the #4 bench terrace drain was largely filled in with refuse sediment. 2. CRDA-2 Upland Permanent Diversion Ditch breached at a point approximately 150 yards from the western terminus of the ditch, where the ditch crosses a dry wash. The ditch at this location had filled in with sediment from the dry wash and overtopped, resulting in upland drainage flowing onto the refuse. Debris path indicates that the water flowed across a compacted corner of the active refuse bench and then down the access road ditch, with no apparent adverse consequences. A 50 to 100 foot segment of the permanent diversion in the vicinity of the breach needs to be cleaned out and restored to - design capacity. CRDA-1 - 3. An overflow of the Northwest Collection Ditch occurred in a low gradient segment of the ditch a short distance below the junction with_Bench #2 terrace drain. Trie ditch at this location filled in with refuse sediment and overtopped. Out of ditch flow occurred across undisturbed ground for a short -- distance, leaving a surface skim of fine coaly material in some areas; no erosion. Flow re-entered a lower section of the ditch and was conveyed to the sediment pond. 4. Drainage from the rough graded active bench of CRDA-1 caused erosion of the bare refuse outslope in several areas along the southeast outslope of Bench #4. This in turn resulted in blockage of the Bench #3 terrace drain in the vicinity of the sharp turn at the southeast corner of the pile, which was largely filled in by sediment along a 150' segent. Overtopping of the #3 Bench drain resulted in minor rilling (2-4 inch rills) within a 10 foot wide flow path down the revegetated outslope below the terrace drain. 5 Terrace Drain #3 had also been filled in with sediment approximately 50 feet from its junction with the Southeast