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STATE OF COLORADO <br />Bill Ritter, Jr., Governor <br />James B. Martin, Executive Director <br />Dedicated to protecting and improving the health and environment of the people of Colorado <br />4300 Cherry Creek Dr. S. <br />Denver, Colorado 80246-1530 <br />Phone (303) 692-2000 <br />TDD Line (303) 691-7700 <br />Located in Glendale, Colorado <br />http://www.cdphe.state.co.us <br />November 17, 2008 <br />Laboratory Services Division <br />8100 Lowry Blvd. <br />Denver, Colorado 80230-6928 <br />(303) 692-3090 <br />Philip Buck, VP Mining Ops <br />Denison Mines USA Corp <br />1050 - 17 St Ste 950 <br />Denver, CO 80265 <br />?F. c <br />h?? i?\ Q <br />* J876 <br />Colorado Department <br />of Public Health <br />and Environment <br />Re: Stormwater Monitoring - Metal Mining and Mine-Waste Remediation General Permit <br />Denison Mines USA Corp - Van 4 Shaft Monogram Mesa <br />CDPS Permit No. COR04 0248 <br />Montrose County <br />Dear Mr. Buck, <br />The Water Quality Control Division (the Division) has issued (see enclosed) Denison Mines USA Corp a permit <br />certification to discharge stormwater from the above referenced facility under the CDPS General Permit for <br />Stormwater Discharges Associated with Metal Mining Operations and Mine-Waste Remediation (stormwater <br />permit), effective November 17, 2008. This letter pertains to the sampling requirements associated with the <br />stormwater permit for this facility. <br />Permit Certification <br />As allowed under Part I.D.6 of the stormwater permit, the Division has determined that sampling is required to <br />measure the effectiveness of the Best Management Practices (BMPs) implemented at your facility in removing <br />pollutants from stormwater discharge. We have enclosed an Annual Report form (which includes a Discharge <br />Monitoring Report (DMR) form), a list of the parameters for which you need to sample, and a guidance document <br />on sampling. Please review these materials closely. <br />Monitoring Requirements <br />During the period beginning today and lasting through September 30, 2011, the Van 4 Shaft Monogram Mesa <br />facility is subject to the monitoring requirements discussed below, at each discharge point (see Representative <br />Discharge, below) of stormwater discharge from the facility. <br />Representative Discharge: When a facility has two or more outfalls that, based on a consideration of features, <br />materials and activities within the area drained by the outfall, the permittee reasonably believes discharge <br />substantially identical effluents, the permittee may test the effluent of one of such outfalls and report that the <br />quantitative data also applies to the substantially identical outfalls. In addition, for each outfall that the <br />permittee believes is representative, an estimate of the size of the drainage area (in square feet) and an <br />estimate of the runoff coefficient of the drainage area (e.g. low (under 40%), medium (40% to 65%) or high <br />(above 65%)) shall be provided. <br />Samples shall be taken twice per year, at least one month apart, unless otherwise directed by the Division. Below is <br />a summary of the sampling requirements for the Van 4 Shaft Monogram Mesa facility, including additional <br />sampling requirements in terms of how to sample, what type of storm event must be used, and what measurements <br />of the storm event itself must be taken. These are also explained in the enclosed sampling guidance document.