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II. Water Quality The CC&V sediment pond discharges to Arequa Gulch, Water Body Identification (WBID) stream segment COARUA22a, streant segment 22a of the Upper Arkansas River subbasin. This segment is composed of the "Mainstem of Arequa Gulch from the source to the confluence with Cripple Creek." The CC&V effluent travels down Arequa Gulch to Cripple Creek, stream segment COARUA21 of the Upper Arkansas River subbasin. This segment is composed of the "Mainstem of Cripple Creek from the source to the confluence with Fourmile Creek." Both stream segments aze classified for Cold Water Aquatic Life Class 2, Class 2 Recreation, and Agriculture. Both segments are designated Use Protected. Numeric standazds are developed on abasin-specific basis and aze adopted for particulaz stream segments by the Commission. Table A-2 presents the stream standazds for segments COARUA21 and COARUA22a from the Classifications and Numeric Standards for Arkansas River Basin, Regulation No.32. The standards for both Cripple Creek and Arequa Gulch are considered in this assessment. For most parameters of concern the stream standards for Cripple Creek aze the same or more stringent than those of Arequa Gulch, which currenly has site-specific-based standazds for aluminum, manganese, zinc and pH. Discharges from the CC&V sediment pond must not cause or contribute to exceedances of wafer quality standazds in either Arequa Gulch or Cripple Creek. Arequa Gulch Site-Specific Standards 1n the 1998 Arkansas Basin Rulemaking Hearing, the 85th percentile was used for the chronic standards for zinc and manganese. There was limited data, and therefore a short period of record was used to set the quality-based standards for these two pazameters (1/1/96-10/20/97). The acute and chronic aluminum standazds (11,000 ug/1) were based on the recalculation procedures that used acute and chronic toxicity information derived from studies on organism representative of those in the segment. In the site-specific rulemaking hearing in 2001 for pH in Arequa Gulch, a pH standazd was adopted by the Conunission based on a three-yeaz period of record (1/1/99 through 7/20/01). The lower end of the Lmderlying standard of 6.0-9.0 is based on the 15th percentile of the three-yeaz period of record. The temporary modification was based on the minimum value in the data set in that same three-yeaz period of record. In July 2002, the Commission adopted changes to the zinc uid manganese standards that will become effective on January 20, 2003. The new chronic zinc standazd is based on the 85`" percentile of data from a five yeaz period of record. The new acute and chronic manganese standards are based on the recalculation procedure. The standazds for Arequa Gulch and Cripple Creek aze included in Table A-2. Changes in standards that will take effect on January 20, 2003 aze noted in the table in pazentheses. Table A-2 Standards for Stream Segment COARUA21 and 22a Changes in standazds that will be effective Janu 20, 2003 are included in Parentheses Standard COARUA21 COARUA22a ~ '' r ;ti_. ~ 'Pl1`sicalgridBialo cal ti;,, '" ~, ~ '~'_° Dissolved Ox en (DO 6.0 m ,minimum 6.0 m ,minimum H 6.5-9.Osu 5.6-9.Osu Fecal Coliform 2000 / 100 ml (200 / 100m1 2000 / 100 ml z '., - _,i . F"2 4 t _s-.c. .. ~ , 5s sY •`t r, a._. IXIOr LUAL`3~` ~`~' -~~~ -~T~. .. e K ~~}'ES 3 ~ ~,~~~$~ Un-ionized anunonia acute TVS TVS Un-ionized ammonia chronic 0.02 m 0.02 m Chlorine acute 0.019 m 1 0.019 m 1 Chlorine chronic 0.011 m 0.011 m Appendix A Page 3 of 13