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!. (Page 2) • MINE ID ,f OR PROSPECTING ID ~ W-77-342 INSPECTION DATE 2/23/96 INSPECTOR'S INITIALS ACS This inspection was conducted to make observations related to an incident that occurred on 2/21/96 which resulted in a discharge of mill process water from the Ute Park Pump House into the area below the pump house where the lower flood bypass ditch connects with the Ute Creek bed. The Ute Creek bed eventually passes beneath County Road No. 3 and empties into the Williams Fork River just east of the county road. The Henderson Mill has a discharge point, designated outfall 006 in the facilities CDPS permit, that ie located just above the culvert at the county road. A flow rate measuring flume is located at the outfall location. Zero flow through the flume was observed at the time of this inspection, and based on observations of the snow present above and below the flume location, there had been no recent flow through the flume. Flow of process water from the Ute Park Pump House was detected by the Operator during the afternoon of 2/21/96. This incident was reported to the Division of MinEerale and Geology (DMG) during the afternoon of 2/22/96, thus meeting the 24-hour reporting requirement of Rule 8.1 for failure of "any Environmental Protection Facility designed to contain or control designated chemicals or process solutions ae identified in the permit". The Operator has subsequently provided a written report that fulfills the notification information and follow-up information of Rules 8.2.2 and 8.2.3. The following mill-site facilities were inspected by DMG during the afternoon of 2/23/96: 1) the seep water collection moat below the main tailing dam; 2) the head gates at the outlet ditches from the seep water collection moat, ae well ae the outlet ditches that carry seep water from the moat to the Ute Park Pump House; 3) a complete inspection was made of the Ute Park Pump House facility; 4) the snow covered area immediately below the Ute~Park Pump House; 6) outfall 006 designated in the Henderson Mill CDPS Permit. The following circuaatances led to the discharge of mill process water from the Ute Park Puap House: 1. High winds and heavy, wet snow resulted in utility line slap that caused a power outage at the Ute Park Pump House. Henderson Mill personnel determined that an inspection of the power lines was necessary prior to restoring power to t:he Ute Park Pump Houae. The Ute Park House ie equipped with an MRTU alarm system to monitor for power failure. The alarm system ie independent of the normal pump house contro:L system. 2. One of the established procedures for the Henderson Mill. in the event of a pump house power outage ie to close two gate valves at the outlet ditcliee from the seep water collection moat below the tailing dam, thus preventing additional seep water from reporting to the Ute Park Pump House until power is restored. These gate valves were closed, in accordance with procedure, within one hour of the power outage. The seep water ie typically acidic, with pH values as low as 2 or 3, and also carries a load of dissolved metals. 3. Mill process water reports to the Ute Park Pump House via the decant system from the tailing pond. The process water circuit at the pump house ueual.ly operates ae a closed eyetem, with the decant line connected directly to a pump manifold where mill process water is pumped directly to Eaet Branch Reservoir. To prevent ringing in '. he process water return line, a Teledyne Valve has been installed at the back of the pump manifold. There ie a pneumatic valve, set at 90 psi, located below the Teledyne Valve. If both of these valves are open, mill process water from the pump manifold will discharge to the seep water trench located below the pump house floor. Once the capacity of the seep water trench is exceeded, the containment of fluids at the pump house is lost. The pump house begiins to fill with water through the floor drains, and the water will leak out of the pump k:ouse through the overhead and man doors. 4. The Teledyne Valve was stuck open during the power outage. The compressor that maintains 90 psi back-pressure on the pneumatic valve was inoperable during the power outage, and when compressed air bled out of the eyetem, and back-pressure on the valve equilibrated with hydrostatic head in the decant line (86.5 psi), the pneumatic valve opened, and lose of containment, ae described in item f3 above, occurred. When waiter was detected flowing out under the doors at the pump house, the Teledyne Valve was manually closed, halting the discharge of process water from the pump manifold. The Operator estimates that a total of 35,000 to 47,000 gallons of process water was released prior to closing the valve.