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© Mt Carla Leakey Colorado Depar[mtnt o/'Public Health and Envtranmen[ September Z2, 1997 Page 1 • 8/26/92 Letter from J. Kubic to R. Burrell (provides information on requirements for exemptions from permit effluent limitations based on stormwater runoff) • 9/10/92 Letter from R. Burrell to A. Ihlenfeldt (provides background information for stormwater exemption for the Marr Mine, confirms that regular pond maintenance including sediment removal is occurring, and references exemption provisions for secondary settleable solids limitation) • 8/12/93 Letter from J. Nettleton to P. Nelson (discusses coordination between Kerr and WQCD relative to stormwater exemption which occurred over the previous yeaz and provides revised stormwater exemption request form meeting all applicable WQCD requirements) • 4/15/97 and 7/2/97 stormwater Exemption Requests for the Reporting Periods of 3/97 and 6/97 (periods identified in the 9/4/97 Notice of Significant Noncompliance) • 7/11/97 Letter from J. Kubic to J. Mossman (approval of 4/15/97 and 7/2/97 exemption requests) The Marr Mine employees a number of sedimentation ponds to intercept and control runoff • from all mine disturbance azeas. These ponds are constructed, maintained, and operated to tntercept and retain runoff from the assoctated disrurbed azeas, with runoff water being retained in the ponds for at least 24hours and usually significantly longer to allow settlement of suspended solids. TSS and iron exceedances result from very high spring (snowmelt) runoff volumes which exceed the regulatory and practical design storage capacity of the ponds, and from high natural concentrations of very fine particles which will not readily settle out of the water. The elevated iron concentrations are associated with the fine sediments. These conditions are not unique to the mine site and are consistent with spring runoff conditions for other surrounding developed and undeveloped lands in the general area as evidenced by high TSS and 'trop loads for all area drainages in the spring. Given that the problem is a narural one related to the hydrologic and geomorphic environment of this area, as previously recognized by the WQCD, development of corrective action plans as referenced in your September 4, 1997 letter is unnecessary and inappropriate. The current system of documenting and repotting any exceedances and providing the associated documentation to correlate specific exceedances to stormwater runoff per the provisions of the existing permit is the most practical and effective method of providing the WQCD with verification of ongoing permit compliance. After you have opportunity to review this submittal, please feel free to contact me with any questions regarding this submittal, permit compliance, or related matters.