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Ms Carla Lenkey THIRD QUARTER 1997 DIVIR 'December 9, 1997 page 4 and Section 34 precipitation data evidence precipitation above the 10 year, 24 hour event, entitling the discharges to exemptions from the SS, Fe, and TSS. While the West Station was not in service, the area is located between the Section 16 and Section 34 measuring devices; it would be expected, then, to have received rainfall in the same range as those two stations of 2.34 to 1.84 inches. This would then entitle the discharges from Outfalls 008A and OlOA to a similar exemption from the discharge standards for SS, Fe and TSS. Documented Rainfall Data Enclosed with this letter are SAROAD (Storage and Retrieval of Aerometric Data) tables indicating hourly totalized precipitation for the Section 16, Section 34 and Gossard precipitation sites as demonstration of meeting the Burden of Proof Requirement found in permit COG-850017, on page 6, Part I, B, 1, d, 1, specific for rainfall events. When reviewing the SAROAD tables, please note the cumulative precipitation from September 18 through September 22 for Section 16 totals 5.22 inches. Cumulative precipitation for the same time period for Section 34 totals 4.40 inches. The total precipitation for the Gossard station for the same time period total 4.27 inches. Daily rainfall exceeded the 10 year, 24 hour event level of 1.8 inches at two of Colowyo's measuring stations, and was significant at the third station. °,xemotion Request _tccordingly, Colowyo claims the Alternate Limitations for an Active Mining Outfall of Permit No. COG- 850017, page 4, Part I, B, 1, a, specific to any precipitation event for Outfalls 002A and OOSA; and specific to Outfalls 004A, 007A, 008A, and OlOA for a precipitation event greater than the 10 year, 24 hour precipitation event (meaning an event equal to or in excess of 1.8 inches of precipitation) occurring from 0600 hours September 18 through 0600 hours September 19, 1997. This event generated 2.34 inches of precipitation at the Section 16 precipitation station within 24 hours. This same event generated 1.84 inches of rain at the Section 34 precipitation station. 1.64 inches of precipitation was measured at the Gossazd precipitation station for the same time period. The West Station was not in service, however the azea is located between the Section 16 and Section 34 measuring devices. Colowyo hopes the information provided in this letter clarifies the events which occurred at Colowyo during the third quarter 1997. We would be happy to meet with you and members of the WQCD to discuss this further if necessary. Please feel free to contact me at (970) 824-1531 if you have any questions or need additional information. Respectfully, lLLCt~. / ~ . ~~~ imberley A. Wolf