REV104140 - Laserfiche WebLink

Home Browse Search

as well as September, at this site. (~ The statement suggesting that TDS declining has been removed from the n u values at SW-S2-2 are text. 16. The discussion of TDS values within the Fish Creek basin has been expanded to examine in more detail the effects of mine discharges on water quality in this area. As PWCC has stated in Tab 7 (Hydrology) of the Seneca II Mine permit, Cow Camp Creek is not a viable source of water for drinking, irrigation, or aquatic habitat due to its ephemeral nature. Surface water monitoring of Cow Camp Creek since 1986 has verified that is is ephemeral; Cow Camp Creek has consistently discharged to Fish Creek only during May of each yearly monitoring period. PWCC has not previously predicted maximum expected TDS levels for Cow Camp Creek for these reasons, and we see no reason to do so at this point in time. 17. ~~ 18 eaa Pew Models used to predict runoff are based on rainfall, not snowfall. Peabody, in its hydrologic design analysis uses Figures 38 through 43 on pages 57 and 67 in the NOAA Atlas, Vol. III, 1973. Pages 14 and 15 of this same document discuss the differences between precipitation as rainfall and snowmelt. The 1.6 inch number used is based on the 0.10 probability (Figure 40) of the 24-hour precipitation event. Many of the methods used in stormwater management are based on studies and research conducted by the SCS. These same methods are documented in Applied Hvdroloav and Sedimentology for Disturbed Areas by Dr. Richard Warner et al., also author of SEDCAD. As a final verification of the proper figures to use, a call was made to Mr. John Andrews, Assistant Area Engineer, SCS, Denver, CO. Mr. Andrews verified the proper figures were the ones that showed precipitation as a result of rainfall, or the ones that consider precipitation from May to October. The maps contained in "Peak Flows in Colorado" by the SCS, were adjusted in the mountain areas to account for rainfall only, i.e., the 0.10 probability maps were superimposed onto the 10-year, 24-hour precipitation maps shown in this guide. This same rationale holds true for other comments regarding differences in precipitation amounts. Peabody cannot comment on differences in input values between DM&G and PWCC because DM&G did not include their input values. PWCC assumes that the ditch sizes in question refer to those listed in question No. 17. With the exception of the Wadge Pit lA, all ditches have been in place for several years. A number of cross sections were taken in the field to arrive at