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r III IIIIIIIIIIIIIIII STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Drpanmem of Natural Resources I 1 L{ Sherman 51 , RUIIDI 215 ~, +tlk Denver, (~ulnoulo 01103 I ~ ` Phunc' (f U { I Hfi L- { S o, III FA%: I ill 4111 L'~If I UU DEPARTMENT OF NATURAL DATE: October 16, 1996 RESOURCES TO: Erica Crosby Roy Romer Governor FROM: Susan Burgmaier lames 5. LochheaA Execmive DveOO~ RE: Seneca II-W Mine (C-82-057) Michael 0. long Division Dnerlo~ 1995 Annual Hydrology Report I have completed a review of the 1995 AHR for the Seneca 11-W Mine. I reviewed water quantity and quality data, but not sampling frequency compliance since you already did that part. Following are my comments on the report. 1. The approved permit application package, in Tab 17 (Probable Hydrologic Consequences), predicts there will be little or no impact on surface water quantity. An increase in Total Dissolved Solids (TDS) is expected on Dry Creek (114%) and Sage Creek (7%). Ground water 9uality is expected to undergo a 7-9% increase in TDS, and a slight drawdown, which will be Ilmited to the area within the permit boundary, is expected. 2. Ground water levels exhibited typical seasonal fluctuations. Water levels were higher than normal in the Spring, due to the unusually wet weather in the mine area. 3. TDS is increasing in the Hubberson Gulch alluvium. Hubberson Gulch is tributary to Dry Creek. The downstream surface water monitoring site on Dry Creek indicates the increases in surface water TDS, to date, are still below the predicted increase. Increases in surface water TDS were lessened by the higher than normal precipitation during the year. 4. Hydrographs for Hubberson Gulch, Dry Creek, and Sage Creek show seasonal fluctuations consistent with baseline data. Data from the Spring shows higher flows than normal, again due to higher precipitation in the early part of the year. 4. TDS is increasing in the Sage Creek alluvium, but there have not yet been discharges to Sage Creek, since Pond 009 has not discharged. The increase, then, is not likely mine related. 5. Tables 3 and 10 of the AHR should be revised in future reports to note the date monitoring was discontinued at any given site. [f a casing faded, a well was mined through, beavers dammed the flow, etc., the date of that occurrence should be noted. A considerable amount of time is spent each year trying to figure out when a monitoring site was dropped. 6. Monitoring was discontinued at well GW-S2W-7A1 when the casing was destroyed. Will Seneca Coal Company be replacing this well? 7. It would be helpful if, in future reports, Seneca Coal Company would include tables of cumulative data for certain parameters at certain sites. Tables of all data to date for