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COLORADO DEPAR71VIENT OF HEAL77•ater Quality Control Division • Rationale -Page 8, Permit No. CO-0029947 Table VI-2 -End ojPipe Comparison (DMR Dota vs. WQ,S Standards} Paratneler Segment 2 WQ,S' EPA "Gold Book" Maximum Reported Commenu (mg/l) Atute Ctite-ia Concetrtrntion (mg/l) (mg/1) Toro! Amnwnra, as N 0.06 (unianrzedJ pH/I'emp Depd. <0.80 Below Standard Nitrate, as N 10.0 10.0 S. 66 Below Standard Sulfate 336 - 576 NA 1,200 Avg. of 687 mg/t 576 -9160 9160 -above Fluoride 1.0 NA 0.91 Below Standard Arsenic ~/) 0.05 NA 0.011 Below Stardard Copper (IR) 0.018 0.018 <0.012 Be%w Standard Lead (IRJ 0.025 0.083 <O.OSS <O.OSS mg/P xas the ddectron limit Boron 0.75 NA 0.79 Avg. of 0. S8 mg/t Phenol NA 10.2 0.072 Below Standard ' Aquatic h;(e and agricultural use WQS from previous rationale. " DMR data from Table V-1 The table indicates 'end of pipe' WQS violations for sulfate, lead, and boron. Oj the three violations, primary concern should be given to the sulfate violations as the boron and lead violations xnuld be non- existent if the mass balance equation ><ns used. Additionally, the Moron standard of 0.75 mg/! u bused upon the protection of such sensitive crops as cirrus groves. The grasses that naturally occw in this part of Colorado arc much more tolerate to boron and the appropriate boron standard should be higher (see previous rationale). Although !lu detection limit of the lead analyses was not low enough to preclude the possibility of exceeding the WQS of 0.025 mg/l, (nor was it the most sensitive detection limit available) inclusion of a permit limit rs not deemed necessary considering that dilution is not accounted for. However, a request for appropriate detection Gmits have been included in Part I. F.2 of the permit to improve reformation obtained from analytical results. WET testing should also indicate acutely task effects that waou/d be caused by lead. Howevn, concern is raised over the concentration of sulfate within the ejjluem. The previous rationale referenced sources stating that sulfate concentrations of up to 576 mg/f were acceptable for irrigation, 576 -960 mg/! were doubtful for irrigation, and concentrations above 9160 mg/[ xrre unsauable for irrigation. Tau DhIIl data indicates that of the seven samples available for 1993, the average sulfate concentration wnr 687 mg/f and the rnasi»utrtt concentration was 1200 mg/t. The nu:ximrun value of 1200 mg/P skewed the average as witlwut rt the average x+ould be 602 mg/P. Nonetheless, even 602 mg/t of sulfate slightly compromises the quality of the efJlttent. The previous rationale stated that after review, the Division may require additional investigations pertaining to methods to reduce sulfate concentrations, if deemed necessary.