2018-09-10_INSPECTION - M1988112

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DAM NAME: San Luis Tailing Dam DATE OF REPORT: 06 20 18 TAILING DAM INSPECTION FORM Directions: Mark an ✓for conditions found and underline words that apply SEEPAGE AND DRAIN OUTFALL PROBLEMS NOTED: ❑(30)NONE ❑(31)SATURATED EMBANKMENT AREA ❑(32)SEEPAGE EXITS ON DAM ❑(33)SEEPAGE EXITS AT POINT SOURCE 0(34)MINOR PONDING OF PIPE LEAKAGE AT TOE DRAIN OUTFALL SEEN: 0 YES ❑NO ❑(35)FLOW ADJACENT TO DRAIN PIPE ❑(36)DRAIN OUTFLOW TURBID ❑(37)DRAIN DRY/OBSTRUCTED 0(38)OTHER: See comment. SHOW LOCATION OF DRAIN ON SKETCH AND INDICATE AMOUNT AND QUALITY OF SEEPAGE See Figure 1 for location. Photos 13-16:Toe drain manifold collection pipe was disconnected at time of inspection. All 3 pipes appeared to be flowing clear. Seepage quantity not estimated due to partially submerged exit conditions. Storm-water runoff sediment accumulation from right groin area continues to be a minor maintenance/access issue in the toe area. CONDITIONS OBSERVED: Z GOOD ❑ACCEPTABLE ❑POOR STORM WATER MANAGEMENT SYSTEM PROBLEMS NOTED: ❑(40)NONE ❑(41)NO EMERGENCY SPILLWAY ❑(42)EROSION AT DROP STRUCTURE ❑(43)CONCRETE DETERIORATED/UNDERMINED ❑(45)STRUCTURE MAY BE TOO SMALL ❑(46)DIVERSION CHANNEL EROSION ❑(47)INADEQUATE CHANNEL FLOW CAPACITY ❑(48)CHANNEL FLOW OBSTRUCTED 0(49)OTHER: Photos 9-11: South Diversion Ditch drop structure replacement project was under construction at the time of inspection. During construction, storm water from upstream watershed is being contained in the channel by a cofferdam (berm) constructed across the ditch channel upstream from the structure. CONDITIONS OBSERVED: ❑GOOD ❑ACCEPTABLE ❑POOR MONITORING EXISTING INSTRUMENTATION FOUND: ❑(50)NONE ❑(51)GAGE ROD IN POOL AREA 0(52)PIEZOMETERS ❑(53)SEEPAGE WEIRS/FLUMES ❑(54)SURVEY MONUMENTS 0(55)OTHER: Underseepage flows MONITORING OF INSTRUMENTATION: ❑(56)NO 0(57)YES PERIODIC INSPECTIONS BY: 0(58)OWNER ❑(59)ENGINEER See attached piezometer measurements-all instruments remain dry; underseepage flow rates (measured at outfall pipe) remain steady at approximately 40 gpm. CONDITIONS OBSERVED: 0 GOOD ❑ACCEPTABLE ❑POOR MAINTENANCE AND REPAIRS PROBLEMS NOTED: ❑(60)NONE ❑(61)ACCESS ROAD NEEDS MAINTENANCE ❑(62)CATTLE DAMAGE ❑(63)BRUSH ON: UPSTREAM SLOPE/BEACH,CREST,DOWNSTREAM SLOPE,TOE ❑(64)RODENT ACTIVITY ON: UPSTREAM SLOPE/BEACH,CREST,DOWNSTREAM SLOPE,TOE 0(65)OTHER: Continue to maintain surface erosion controls(cross berms and rock-lined downspouts)in right d/s groin repair area,and repair minor gullying in upper left abutment groin near access road where runoff is bypassing the lined ditch. Consider re-directing surface runoff from right lower groin away from d/s toe area to prevent deposition of sediment. CONDITIONS OBSERVED: 0 GOOD ❑ACCEPTABLE ❑POOR OVERALL CONDITIONS Based on this inspection and recent file review,the overall surficial condition is determined to be: 0 SATISFACTORY ❑CONDITIONALLY SATISFACTORY ❑UNSATISFACTORY Page 2 of 4