PERMFILE61538 - Laserfiche WebLink

Home Browse Search

COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Qua[iry Control Division Rationale -Page 12, Permit No. CO-0000221 3) Acrtte WET Limitations - Out(a(!s 002. 003. 005. 006. 010 and OII: The Division has found that dischar>es of pit pumpage, spoils spring water and similar sources from coal mines at similar sites have ezhibite~ effluem toxicity and toxicity failures have previously occurred for some of the discharges at this jacili n this basis, the Division believes there is reasonable potential for the discharges from oulfalls 002, 003, 0(15, 006, OIO and 011 to interfere with attainment ojapplicable water quality classifications or standards, Because of this, the acute toxicity limit has been incorporated into the permit and becomes effective immediately. The permittee is required to conduct routine monitoring, the results of which are to be reported as an LCD. If the LCD 5 100% ejfluem, the permittee is required to conduct the automatic compliance schedule as identified in Part I.A.4.c. of the permit. 4) Chronic WEI'Limitations - Outfalls 004 and 008: Outfalls 004 and 008 discharge to Fish Creek, which is within segmem 136. This segment is classified aquatic life, class 1, with all of the appropriate aquatic life numeric standards. Thus, the default to acute testing applied to the other outfalls does not apply to outfalls 004 and 008. Further, because of the variable nature of coo! mine draiwge and spoil spring flows and their correlation to stream flows, it is appropriate to look beyond annual flows to determine more realistic seasonal IWC's for these two outfalk. The Division used discharge Jlow values for each outfall that represent the mean of the momh[y average flows for each month over the period from 1986 through 1996 in conjunction with the 30E3 developed by the Division for Fish Creek. From these results, the highest momhly IWC per calendar quarter was selected as the quarterly lWC. The monthly flows and corresponding IWC for outfalls 004 and 008 are shown in the following table. The selected IWCs are highlighted in Bold and Double-Underlined. Table VI-8 -Mean Monthly Discharge Flows for Period 7986 - 1996 (cfs) and Corresponding IWCs Out- Jan. Feb Mar Apr May Jun Jul Aug Sep . Oct Nav. .Dec. fau .. 004 .0546 .0889 .2660 .5048 .2909 .1181 .0807 .0629 .0609 .0650 .0673 .0:~ Flow ~C 3.3 5.3 l0.8 I2.3 6.1 9.0 16.8 77.3 16.9 7.5 7.8 3.3 008 .0314 .0395 .2813 .3673 Flow /WC !.9 2.4 I1.3 9~3 2068 .0933 4.4 7.2 0706 .0493 15.0 14.1 0427 .0580 .0424 .0422 12.5 6_8 5.0 2.7 On the same basis as stated for acute limitations above, the Division believes there is reasonable potential for the discharges from outfalls 004 and 008 to interfere x~ith attainment of applicable water quality classifications or standards. Because of this condition, the chronic limit is continued in the permit and becomes effective immediately. The permittee is required to conduct routine monitoring. The results of the testing arc to be reported on Division approved forms. The permirtee will be required to conduct a statistical derivation on the data, looking for an}' statistical!}~ significant difference in toxicity between the control and the effluem concentrations. This set of calculations rill look at the full range of toxicity Qethaliry, growth and reproduction). If a level of chronic rozicity occurs, sack that there is a statisticalh~ significant difference in the lerhaliq• (at the 95'9 confidence level) between the contra! and any effluent concentration less than or equal to the lnstream Waste Concentration (IWC), the permittee will be required ro follow the automatic compliance schedule identified in Part I.A.S. c. of the permit, ij the observed toxicit~ is due to organism lethalit}•. Only exceedance of the limitation specified in Part /.A.l.f. will trigger the requirement for conducting the automatic compliance schedule identified in Pan /.A.S.c. of the permit. If the toziciry is due to differences in the growth of the fathead minnows or the reproduction of the Ceriodaphnia, no immediate action on the parr of the permittee will be required. However, this inciden along with other WET data, will be evaluated by the Division and may form the basis for reopening !h~ permit and irtc(uding additional WET limits or other requiremems.