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month-to-month. Other than weeds and local gully erosion, the reclaimed area appeazs <br />stable. The site has sparse vegetative cover. Seeded species have developed locally, <br />including: Indian ricegrass, western wheatgrass, basin wildrye, brome, cicer milkvetch, <br />and rubber rabbitbrush. There aze large patches of musk thistle and small patches of <br />toadflax. No slope stability problems have been noted during the Division's inspections. <br />Approximately one acre of the disturbed area is being used by an unknown party for <br />storage of trailers, fuel storage tanks, barrels, and miscellaneous items that appeaz to be <br />related to a concrete operation. <br />Impoundments and Earthen Structures Remaining on the Site <br />Two impoundments remain on the site: a constructed sediment control/mine water <br />treatment pond located 200 feet north of U.S. Highway 160 and a surface depression in <br />the northwest part of the site. The design for the sediment controVmine water treatment <br />pond is in the permit application in Exhibit 13 and on Map 12. Map 12 refers to <br />diagrams of the pond that aze in Exhibit 13, and bears a P.E. stamp. The depression <br />covers approximately one-half acre, is a few feet deep, and is not a designed structure. <br />The dimensions of the sediment control/mine water treatment pond appear similar to <br />those shown in Exhibit 13 and on Map 12. The design and early Division inspection <br />reports indicated the principal spillway was a 12-inch diameter culvert that extended <br />through the pond's earthen embankment. In recent years, the inlet end of this culvert has <br />been found, but the outlet end of the culvert on the outslope of the embankment can no <br />longer be found, apparently having been buried during regrading several yeazs ago, as <br />noted in Division inspection reports. The pond's emergency spillway is an open channel <br />that would dischazge water down-slope to culverts underneath Highway 160. The pond <br />was reported during the Division's May 1994 inspection as dischazging less than 2 <br />gallons per hour, presumably through the emergency spillway. Monthly inspections <br />during the last four years have reported the pond as dry in most months, and when it <br />contains water the level is more than 5 feet below the emergency spillway. The <br />embankment of the pond appears stable. <br />Risks to Public Health, Safety and Environment <br />A potential risk to public health, safety, and environment at the Coal Gulch site would be <br />a worst-case scenario in which runoff during a prolonged wet period or a period of large <br />snowmelt rapidly fills the pond with water and causes a catastrophic failure of the <br />embankment, resulting in a sudden release of impounded water toward U.S. Highway <br />160, located 200 feet downslope from the pond. The risk of this scenario occurring can <br />be considered remote because the pond's emergency spillway was designed for safely <br />passing runoff from a 25-year, 24-hour storm and the spillway appears to be in a <br />functioning condition. Discharge from the spillway would make its way to the culverts <br />underneath Highway 160. <br />Another potential risk to public health, safety, and the environment is the risk of water <br />pollution from the dischazge of acidic and salty underground mine water from the <br />backfilled pre-law mine portal, north of the pond. This dschage does not appeaz to <br />