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.- <br />Mr. Toni Schreiner <br />Re: File #M-200/-090 <br />November 20, 2001 <br />Page 3 of 4 <br />.. <br />10. This operation is required to'develop a-Spill Prevention, Control and Countermeasure <br />(SPCC) Plan in conformance with the regulations of the Colorado Department of Public <br />Health and Environment, Water Quality Control Division. The SPCC Plan details spill- <br />prevention measures to be used at the site. A copy. can be provided to the Division when <br />it.,is finalized. They will be using an aboveground fuel tank on site for fueling of <br />equipment. This tank is double-walled and will be placed on a concrete pad that is <br />designed to contain up to 50 gallons of spilled. fuel. The 'SPCC will also detail <br />maintenance and clean-up measures for the fueling station. <br />11. Since excavation will occur to an average depth of 27 feet, the mining operation.will only <br />affect the alluvial groundwater system. The alluvial groundwater system in the Yampa <br />River Valley is contained .within alluvial deposits of Quaternary age and ranging up to <br />100 feet in depth. The alluvial deposits are, typically' underlain by "shale or' sandstone <br />formations of Tertiary and Cretateous age. <br />12. Depth to groundwater was previously discussed in the response to comment #8. <br />13. Hydrologic information for the site was obtained from nearby mining operations and <br />from experience working in similar alluvial systems throughout Colorado. Dewatering <br />records from a similar mining operation approximately one .mile downstream of the <br />proposed River Valley Resource' site indicates that the alluvial groundwater system <br />hydraulic conductivity is approximately 100 feet/day. This value is in the range of <br />similar alluvial systems. ~ Based on area topography, it is assumed that the, alluvial . . <br />hydraulic gradient near the site is relatively low,.likely 0.004 to 0.006 feet/feet, and also <br />typical of similar alluvial groundwater systems. From this information it is estimated that <br />the continuous pumping rate for pit dewatering would be, approximately 150. to 300' <br />gallons per minute, depending upon fluctuations in seasonal groundwater levels. Under <br />. these conditions it is expected that the influence of dewatering will not extend rltore than <br />1,000 feet from the pit walls. <br />The applicant does not anticipate dewatering operations at the site to impact the water <br />rights of adjacent well owners. However, once dewatering at the site has started, ground <br />water levels in the immediate vicinity are expected fo drop. If water levels are dropping <br />in adjacent wells, due to, dewatering at the River Valley Resource operation, such that <br />well owners' historic water production may be injured, the applicant will begin 'to <br />implement one or more of the following measures. However, if the well has not been put <br />to beneficial use prior to mining, tfie applicant should have no responsibility to provide <br />mitigation. <br />1. Modify existing wells to operate under lower ground water conditions. This <br />would include re-drilling existing wells,to deeper depths or lowering the pumps. <br />All work would be done at the applicants expense with the exception of replacing <br />'equipment that-was non-functional prior to mining. <br />2. If existing wells cannot be repaired, the applicant will drill. a new well for the <br />owner to replace the damaged-well. The new well will produce water of the same <br />quantity and quality to support the historic use. . <br />