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,~ _- ~. SEtTLEFISNT AGREEM@IT JUSTIFICATION NOV C-96-019 Notice of Violation (NOV) C-96-019 was issued November 27, 1996 for "Failure to construct or maintain sediment pond as designed to treat runoff or inflow. Specifically, sediment pond RP-1 primary spillway structure was leaking, allowing water to discharge without sufficient settling time." On becember 19, 1996, the NOV was modified to reflect that the discharge exceeded the effluent limitations established by the Colorado Water Quality Control Act. The facts of the violation as agreed to at the Assessment Conference are as follows. A heavy rain began to fall on November 22, 1996. The ground at the refuse piles area was frozen at the time, resulting in a high percentage of the rain reporting to the ponds as surface flow. It is probable that the precipitation event did not meet or exceed the ten year, twenty four hour event. Mine personnel agreed that there was a danger of a non-compliant discharge from one or more sediment ponds below the active refuse piles. Therefore, a decision was made to transfer water from one or more of these ponds to pond RP- 1, which was empty. The water transfer apparently continued until sometime on November 24, 1996. When the mine personnel visited the site on Monday, November 25, 1996, it was observed that the RP-1 pond was discharging due to a then undetermined failure of the corrugated metal pipe (CMP) dewatering system. The discharge was estimated at six to eight gallons per minute. A sample of the discharge was taken by mine personnel at 8:00 a.m. November 26, 1996. Sample analysis showed the total suspended solids concentration to be 67 milligrams per liter, which is below the effluent limitation. A pump was rented and brought to the site for the purpose of transferring water back to the ponds of origin. The transfer process was initiated at about 8:00 a.m. on November 26, 1996. The pump apparently periodically malfunctioned. To alleviate the malfunction, the suction portion of the pump was occasionally repositioned in the pond, resulting in significant mixing of the water and a corresponding increase in total suspended solids. At approximately 10:00 a.m., Dan Mathews of the Division arrived at the site. Mr. Mathews sampled the discharge shortly after his arrival. Analysis of the sample indicated that the total suspended solids concentration had risen to 127 milligrams per liter. The pumping of pond RP-1 continued until after the water level had dropped below the CMP structure. It is estimated that the pond discharged for something less than 24 hours. Given the volume of flow, and distance to Red Wash, it was judged to be unlikely that flow from the pond entered that drainage. After the pond was dewatered, the CMP within the pond embankment was excavated. It was discovered that a bolt holding a connecting