2022-08-09_REPORT - M1988112 (2)

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DAM NAME: San Luis Tailing Dam DATE OF REPORT:August 5 2022 TAILINGS DAM INSPECTION FORM Directions: Mark and X for conditions found and underline words that apply SEEPAGE AND DRAIN OUTFALL PROBLEMS NOTED: ❑ (30)NONE ❑(31)SATURATED EMBANKMENT AREA ❑(32)SEEPAGEEXITSONDAM ❑(33)SEEPAGE EXITS ATPOINT SOURCE IK(34)MINOR PONDING OF PIPE LEAKAGE ATTOE DRAIN OUTFALLSEEN: ®YES ❑ NO ❑(35)FLOWADJACENTTODRAINPIPE ❑(36)DRAIN OUTFLOW TURBID ❑(37)DRAIN DRY/OBSTRUCTED ❑(38)OTHER SHOW LOCATION OF DRAIN ON SKETCH See Figure 1 AND INDICATE AMOUNT AND QUALITY OF SEEPAGE Minor leakage from toe drain creates puddle,attracting animals,but no pipe damage. CONDITIONS OBSERVED: ❑ GOOD ® ACCEPTABLE ❑ POOR STORMWATER MANAGEMENT SYSTEM PROBLEMS NOTED: ❑ (40)NONE ❑(41)NO EMERGENCY SPILLWAY ®(42)EROSION AT DROP STRUCTURE ❑(43)CONCRETE DETERIORATED/UNDERMINED ❑(45)STRUCTURE MAY BETOO SMALL ❑(46)DIVERSION CHANNEL EROSION El(47)INADEQUATE CHANNEL FLOWCAPACITY ®(48)CHANNEL FLOW OBSTRUCTED ®(49)OTHER Rilling along both sides of drop structure is advancing-continue monitoring and begin planning mitigation strategy. South diversion channel and downstream toe runoff collection swales are in good condition except for choking of culvert south of toe drain(Photo 22). Continue monitoring erosion and revegetation at both side of the drop structure;mitigation will likely be required in 2023. 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 ®(55)OTHER Underdrain flow MONITORING OF INSTRUMENTATION: ❑(56)NO WEIRS/FLUMES ®(57)YES PERIODIC INSPECTIONS BY: R (58)OWNER ❑ (59)ENGINEER Piezometers remain dry. Average underdrain flow measurements from 2020-22(30.8 gpm)are slightly lower than from 2016-2022 (34.5 gpm). Reduction is likely due to ongoing severe regional drought,but continue jetting and video inspection program. CONDITIONS OBSERVED: ® 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 SLOPEBEACH,CREST,DOWNSTREAM SLOPE,TOE ®(65)OTHER 948:Clear toe runoff channel culvert immediately south of toe drain outfall pipe. #49:Disturbed areas adjacent to the South Diversion Ditch Drop Structure that are not protected by riprap were seeded in 2019,but due to drought conditions vegetation establishment is poor to date and erosional rilling is progressing along both sides of the structure;erosion mitigation will likely be required in 2023. CONDITIONS OBSERVED: ❑ GOOD ® ACCEPTABLE ❑ POOR OVERALL CONDITIONS Based on this inspection and recent file review,the overall surficial condition is determined to be: ❑ SATISFACTORY X CONDITIONALLY SATISFACTORY ❑ UNSATISFACTORY Page 2 of 4