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iii iiiiiiiiniiim <br />999 <br />October 2, 1998 <br />MEMORANDUM <br />To: Walt Wright, Mine Manager <br />Bill Pecharich, Surface Superintendent <br />Mark Milner, Environmental Technician <br />Annual Hydrologic Report File <br />Stotmwater Management Plan File <br />From: Thomas C. Anderson, Environmental Coordinator <br />Subject: Storm Event of October 1, 1998 <br />On the afternoon of October 1, ]998, a brief, heavy thunderstorm occurred at the Sanborn Creek <br />Mine site. The total storm event lasted two hours or less. The heaviest rainfall occurred in <br />approximately 30 minutes. Mazk Milner, Environmental Technician and Thomas C. Anderson, <br />Environmental Coordinator inspected the mine area. Areas inspected included the main facilities <br />area around Elk Creek, drainages to the west towards Bear Creek, and drainages and the facilities <br />along old State Highway 133 to the east. <br />Nearly all stormwater management controls were functioning during the event. Problems <br />associated with the recent construction of the new road to the West Vatley Fill, Somerset <br />Cemetery, and Upper Elk Creek were noted. Runoff from the road ditch from the Somerset <br />Cemetery to the lower access road carried sufficiert sediment and water to take out the straw <br />bales at the culvert to the lower access road, and fill the lower access road ditch, plugging the <br />lower access road culvert. Runoff and sediment then overflowed the lower access road ditch to <br />the ditch south of the road south of the pazking lot. South side berm height was insufficient for <br />this additional flow, which then went over the berm to the main access road ditch below. While <br />the sediment fences along the main access road ditch generally functioned, the additional flow <br />went over the top of the lower ones. <br />Runoff was sampled where the road ditch nmoff left the permit azea The flow along the State <br />Highway 133 road ditch was monitored. The flow dissipated by infiltration and the sediment <br />load was deposited along the road ditch in a short distance. Significant runoff did not reach the <br />highway culvert west. of Somerset, and the silt fence and straw bales at the highway culvert west <br />of Somerset remained in functioning condition. Results of the sample will determine if the <br />effluent limitation for settleable solids was met or exceeded in the stonnwater runoff leaving the <br />permit azea at the main entrance. However, the stormwater runoff did not reach the receiving <br />waters at the North Fork of the Gunnison River. <br />Runoff from the Upper Elk Creek road from the Somerset Cemetery to the silt fence above Elk <br />Creek was sufTicient to displace the straw bales from in front of the silt fence, and appeared to be <br />