_INSPECTION - C1994082 ‎(70)‎

• Permit No: C1994082
• IBM Index Class Name: INSPECTION
• Doc Name: Inspection Report
• Inspection Date: 4/22/2008
• Email Name: DTM
• Media Type: D
• Archive: No

Availability of Records
Records were checked at the mine office and were found to be complete and up-to-date through the 1st quarter,
2008.
Roads
Mine site roads had not been maintained through the winter, and remain for the most part snow covered and
impassable. Water bars constructed last fall along a temporary scraper road on the ridgetop west of the topsoil
stockpile near Pond 12 appear to have contributed to erosion on the slope where the slide reoccurred.
Drainage control ditching and water bar locations along the scraper route will need to be modified as
warranted to minimize erosion and divert runoff away from the failure area, as soon as the area has
dried sufficiently to allow for equipment access and dirtwork.
Hydrologic Balance
As noted previously, snowmelt at the site had recently begun in earnest, and permanent channels in the
accessible watersheds were flowing. Much snow still remains in the mine area, with the exception of south
facing slopes.
Quarterly Discharge Monitoring Reports for CDPS Permit CO-0000221 (Seneca Mine Complex)for the 1"
Quarter 2008 were hand delivered to me during the inspection. The report showed no exceedances of
applicable effluent limits for Yoast Mine discharge points during the quarter.
Permanent Channels
In most areas, permanent channel details were obscured due to snow cover. In some locations that were
visible, it was noted that turf reinforcement matting (TRM) installed last fall had been scoured under or sidecut
(due to ditch blockage by ice, apparently). Given the heavy snowpack and associated runoff it is likely that
extensive maintenance will be necessary this year on the recently completed permanent channels. Some
modifications may be warranted with respect to method and timing of TRM installation ( e.g. extend liner higher
up ditch sideslopes; seed channels with fast growing cover crop and permanent channel mix in late summer to
establish growth in the channels during the fall, so that TRM will be more effective during the first year's
snowmelt runoff).
The steep TRM lined diversion channel along the west side of the Pond 12 slope failure was damaged by the
slope failure, and will need to be repaired in conjunction with the landslide regrading/remediation plan. The
diversion may need to be extended along the ridge above (north of)the slope failure location.
Sediment Ponds
Sediment Ponds 11, 12, 13, and 14 were accessible and were inspected. All of the ponds had at least some ice
cover, most with some ice free areas along the margins of the ponds. There was no discharge from Pond 11,
ice level was approximately 6 feet below the primary spillway riser elevation. The other three ponds were spilling
over the top of the primary riser, and discharging significant flow rates due to inflow into the ponds from
snowmelt. Pond 12 discharge was sampled and described in the NOV CV-2008-001 narrative. Pond 13
discharge was very clear; Pond 14 discharge was only slightly cloudy.
Backfilling and Grading; Slides & Damage
Due to snow cover in most areas and limited accessibility, detailed observations were precluded in most areas.
The Pond 12 slope failure occurred on a snow-free south exposure. The slide and related impacts to topsoil and
the hydrologic balance is described in previous sections of this report.
Topsoil & Revegetation
Due to snow cover, limited access, and season, these topics could not be closely evaluated at this time.
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