2007-11-01_PERMIT FILE - C1982056A ‎(3)‎

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 11/1/2007
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans Part 2
• Media Type: D
• Archive: Yes

tons/acre of mulch, following seeding and prior to the development of a vegetated channel, with dischazge at point J.
The three West Rockfall Hazard Trench outslope demonstrations (A-G, G-J, and J-L) document the adequate treatment
of 4.93 disturbed acres using mulched disturbance areas and 5-foot long vegetative filters. The SEDCAD+
demonstrations are provided in Exhibit 8.
The Water Tank Hazard Trench demonstration consists of the successful treatment of 6.65 acres, of which 0.65 acres
are disturbed. SEDCAD+ modeling indicates a 10-year, 24-hour peak flow of 0.61 cfs. The trench will be mulched
with 2 tons/acre mulch, following seeding and prior to establishment of a vegetated channel. There are two rock check
dams in the trench; one at across-section T, shown on Sheet 3 in Exhibit 7F, and the other at the outfall of the trench.
A 20-foot vegetative filter below [he lower rock check dam treats the remaining water. The outslope of the Water Tank
Trench and anticipated associated construction disturbance consists of 0.44 acres, resulting in a peak flow of 0.42 cfs.
The disturbance will be treated with 2 tons/acre mulch and the downgradient 20-foot vegetative filter will achieve
effluent limitations fora 10-year, 24-hour storm. The SEDCAD+ demonstrations are included in Exhibit 8.
The East Rockfall Hazard Trench demonstration consists of the treatment of 18.7 acres, of which 2.22 acres are
disturbed. SEDCAD+ modeling predicts a 10-year, 24-hour peak flow of 2.12 cfs. The trench will be treated with 2
tons/acre mulch following seeding. A contour furrow will be established approximately halfway (30 inches) up the cut
to aid in sediment retention. Rock check dams will be established at cross-sections P, N, and M, as well as at 255 feet
below cross-section O and 160 feet below cross-section N, as shown on Sheet 3 in Exhibit 7F. A 175-foot vegetative
filter below the outfall of the East Rockfall Hazard Trench will result in achievement of effluent limitations following a
10-year, 24-hour storm. The outslope of the East Rockfall Hazard Trench consists of 2.25 acres of fill and associated
construction disturbance, which is predicted to result in a peak flow of 2.16 cfs following a 10-year 24-hour storm
event. The outslope will be treated with 2 tons/acre mulch, and the mulch in combination with a 20-foot wide
vegetative filter will result in the achievement of effluent limitations following a 10-year 24-hour storm event. The
SEDCAD+ demonstrations are provided in Exhibit 8.
TCC plans to collect a limited number of discharge water samples at rock filters during a future precipitation event to
support current field observations. Samples will be compared to applicable stormwater limitations for settleable solids.
109 Diversion Filter -Drainage and sediment control for the l09 Diversion will be provided by an existing rock filter
adjacent to Pond F, the vegetation surrounding the site, and revegetation. The site is approximately 0.06 acres in size
and protected immediately upslope by a collection ditch; which limits surface moon contributions to the site.
Southwest District Ventilation Borehole and Substation -Drainage and sediment control at the Southwest District
Ventilation Borehole will be provided by placement of afilter-fabric (silt) fence downslope from the site. In the event
the filter-fabric does not perform adequately to control sediment, the silt fence may be replaced with rock filters at
appropriate drainage points. The ventilation borehole site is approximately 0.2 acres.
Trout Creek Sandstone Test Site -Drainage and sediment control for this site will include revegetating site and use
of existing downslope vegetation (i.e. vegetation filter). The site is approximately 1.2 acres in size and is surrounded by
existing vegetation, which will serve to limit the amount of moon to the site. During active drilling, a berm around the
site will divert upland flows around this area.
Fish Creek Tiaale -Drainage and sediment control at Fish Creek Tipple involves the use of diversion ditches,
culverts, riprap, and Sedimentation Pond E. Details of the sedimentation control system for this site are found on
pages 2.05-16 through 2.05-19 of the Fish Creek Tipple Appendix, Volume VIII.
NMD Power Borehole -Drainage and sediment control for this site involves gravel surfacing of the pad and use of
the surrounding vegetation as a downslope vegetative filter. The site is approximately 1 acre and will be surrounded on
three sided by topsoil stockpiles, which will limit surface moon to the pad. The SAE demonstration for this site is
presented in Exhibit 8.6.
TR07-60 2.05-83 06/04/07