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GULCH A SEDIMENT POND • TECHNICAL REVISION x History The original location, design pla.~s and specifications for the Gulch A sediment pond ~•+ere originally described in Section 2.05.6, Section 4.05.6 and Exhibit 7 of the original February 5, 1981 permit application. On December 11, 1981, Colowyo submitted additional permit information, a portion of which addressed a change in drainage control for the East Pit area. A sediment control ditch was constructed in lieu of a sediment pond to ,- direct the drainage from Gulch A to the pond at the base of the Streeter Fill. This particular collection ditch was to be used until such tim=_ that mining had advanced into the vicinity of Gulch A. (.lining has advanced into the vicinity of Gulch A, therefore, to provide the roost effective drainage control, it is necessary to construct the Gulch A sediment pond. Since the pond is located above the Upper Good Spring surface water monitoring location, the Upper Good Spring location will no longer. serve as a i useful background condition indicator. To remedy this situation, Colo•.vyo ' proposes to relocate the monitorin; point immediately upstream of the Gulch A I sediment pond. The new location fo^ water monitoring will be chos=_n following I • construction of the pond. The o=_r~=_-aT location for the Gulch A pond is shown ~ ~on t•1ap 12 - Hydrology Central in tie or :ginal permit application. Environment i. Geology: The pond is located immediately above the Good Spring Creek f]oodp]ain on a fan which was previously deposited from parent rock forming the steep slopes and drainage adjacent to the pond location. The Good Spring Creek floodplain is mapped as a Homelake Loam on 0-3% slopes. The Homelake Loam along Good Spring Creek is a deep, poorly ` drained soil developed from colluvial deposits transported from the adja- cent highlands and reworked by a1lu:ial processes of Good Spring Creek. Typically, the unit occurs along the floodplain at elevations between i 6000 and 7000 feet. As indicated from Coloo-ryo monitoring wells along Good Spring Creek, the water table is unconfined and is present at or near the surface of the floodplain most of the year. The fan is a sandy loam material with associated cobbles and angular frag- ments from the cliffs above. The fan was drilled to 11 feet with a tractor mounted auger to determine if the material is suitable for dam construe- . tion. With the exception of any cobbles or large fragments encountered, the material is suitable for dam construction. Any large rock encountered will be segregated from material utilized for the dam. • 2. Climate: The climate in the area of the Colowyo Permit has previously been described in the original Colowyo Permit Application.