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iiiiiiiiiiiuiiiiii ~ • <br />MEMO: Fish Creek AVF Findings for the Seneca Mine 10/14/81 <br />T0: Sandy Emrich p. 2 <br />As stated above, there is the slight potential for water quality <br />degradation in the AVF as a result of the proposed mining opera- <br />tions. Information supplied by the applicant in the "Alluvial <br />Valley Floor Investigation of Fish Creek" (hereafter known as <br />the AVF study) details why the potential for this impact is very <br />slight. <br />Generally, since the mining operations are located within a portion <br />of the Fish Creek drainage (1.16% of the drainage area will be <br />disturbed), there is the potential for spoils water containing <br />elevated levels of dissolved solids to enter the Fish Creek AVF. <br />The mechanism for transport of this degraded water would probably <br />be through the alluvial aquifer of the unnamed tributary to Fish <br />Creek shown on Exhibit 7-16 of the AVF study. Water quality <br />modeling done by the applicant (AVF study, page 6) concludes that <br />the average TDS of Fish Creek could increase by 2% as a result of <br />mining operations. Resultant water quality would still be well <br />within acceptable levels for irrigation purposes. <br />3. Surface coal mining and reclamation operations would be conducted <br />to preserve, throughout the mining and reclamation process, the <br />essential hydrologic functions of the alluvial valley floor. <br />(Rule 2.06.8(5)(a)(iii)). <br />The AVF itself would not be physically disturbed by mining. The <br />potential for water quality degradation, as discussed above, is <br />not considered substantial enough to warrant changes in the mine <br />and reclamation plan. Rather, the potential impact may be ad- <br />dressed in the monitoring plan, to ensure that the essential hydro- <br />logic functions are maintained. <br />Monitoring Plan--Findings <br />The applicant proposes to monitor water quality and quantity in the <br />vicinity of the Fish Creek AVF as follows: <br />1. The water quality of discharges from the sediment pond located <br />in the unnamed tributary to Fish Creek will be monitored. <br />2. The water quantity and quality of the alluvial aquifer of the un- <br />named tributary to Fish Creek will be monitored in a well located <br />near where the drinage leaves the permit area. <br />3. The water quality and quantity of discharges on the southernmost <br />tributary of Fish Creek directly downstream from mining (SW-S2). <br />The monitoring plan provided by the applicant will meet the objectives <br />of Section 4.25-5 of the Colorado Permanent Regulatory Program. <br />DC/cb <br />