2010-01-13_GENERAL DOCUMENTS - M1983083

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The low base flows continue down the existing rock excavated channel to Culvert C3. High storm flows are diverted through a concrete side spillway constructed in the channel adjacent to Cl. The side spill discharges storm flows into a newly constructed channel that conveys flows over the new grading below Pond 4. During construction of the drainage channel, the excavated material was screened and sorted for use as bedding and riprap material and placed to a depth of 10 inches. Deere and Ault, Inc. assisted the Division in determining the location of the drop structures and the concrete spill pan. The boulder drop structures were each approximately 50 feet long and comprise a majority of the upper drainage channel. In between drop structures, rip rap was utilized. Each drop structure consisted of a 5-foot concrete seepage-cutoff wall that ranged from 15 inches to 24 inches thick, reinforced with#4 rebar. The boulders ranged from 2 feet to 4 feet in diameter and were grouted in place. During construction of the drop structures, the concrete and grout was tested by Shannon and Wilson Inc. to ensure it met the required specifications. Concrete blankets were necessary due to the drop in night time temperature. The lower grouted riprap channel and basins also used the larger rock, approximately 12 inches to 24 inches in diameter. The channel was moved approximately 60 feet to the west where it reconnected with USC-7 at the location of Pond 5 embankment. The concrete side spill-pan directs larger flows from the upper channel across the access road and into the lower channel. Channel USC-7 adjacent to the access road will continue to be used to direct water during low flows. A grouted boulder rundown was constructed to stabilize the outfall of Culvert C3. A 4-foot concrete cutoff wall with#4 rebar was installed at the outlet of Culvert C3. Grouted 24 inch rocks were placed around the culvert and down the 2H:1V slope where it enters Gilson Gulch. The lower energy dissipation basin was placed at the outlet of Culvert C3. Task 8 Provide and Incorporate Organic Material: In order to create a sufficient depth of plant growth medium, organic materials were incorporated into the native soil. A combination of dry chicken litter at a rate of 3 tons/acre, Biosol Plus (7-3- 3) at a rate of 1,200 pounds per acre and certified weed free mulch were mixed and incorporated into the soil. A wheel- loader mixed the organic material together and incorporated it into the soil to a depth of 18 inches. Task 9 Surface Roughening: Surface roughening took place on the upper mine area (the previous location of Ponds 1 and 2), the facilities area, and all backfilled areas. The loader and a tracked excavator gouged the soil surface to mix in the organic material and mulch. The"figure eight" road in the upper mine area was roughened to a depth of 12 inches to 18 inches to deter vehicles from entering the site. The lower mine areas were roughened to a depth of 6 inches to 12 inches to accommodate access by the landowner. Task 10 Revegetation: After the surface was roughened, the site was hand seeded. A total of 6 acres were revegetated using the Ponderosa Pine/Spruce/Fir mix. Twelve (12)seed bags were provided by the Division to CCC to revegetate all reclaimed and disturbed areas. The seed mixture included the following species: Species Scientific Name Variety lbs/Acre Yarrow Achillea lanulosa 0.2 Rocky Mt. Penstemon Penstemon strictus Bandera 0.6 Western wheatgrass Pascopyrum smithii Arriba 3.0 Slender wheatgrass Elymus trachycaulus San Luis 2.0 Mtn. Brome Bromus marginatus Bromar 4.0 Arizona fescue Festuca arizonica Redondo 1.0 Hard fescue Festuca ovina Durar 1.0 Indian ricegrass Oryzopsis hymenoides Nezpar 2.0 Big bluegrass Poa ampla Sherman 1.0 Canby bluegrass Poa canbyi Canbar 0.5 Green needlegrass Stipa viridula Lodorm 2.0 TOTAL pis lbs./acre(hand seeded) 17.3 Task 11 Post Construction Sediment Control: A storm water management plan was developed for the site. The constituent of concern at this site is sediment that could be transported from the site during and immediately after reclamation construction. The reclamation plan for the site contains a number of provisions to manage storm water that could emanate from the site during reclamation. The severe roughening of the site serves to incorporate nutrients into the soil and disrupts surface runoff patterns to reduce flow velocities and minimize erosion potential. Pond 5 also acts as a sediment control, and silt fence was placed in the lower region of Gilson Gulch to contain any sediment generated during a storm event. The silt fence will remain in place until vegetation has established and the SWMP is terminated.