2018-03-01_HYDROLOGY - C1981010 (2)

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COLORADO Water Quality Assessment Department of Public Health b Environment Temporary modification: Arsenic chronic = hybrid through 12/31/2021 Dissolved Cadmium acute and chronic = TVS Total Recoverable Trivalent Chromium acute = 50 lag/l Dissolved Trivalent Chromium chronic = TVS Dissolved Hexavalent Chromium acute and chronic = TVS Dissolved Copper acute and chronic = TVS Dissolved Iron chronic = For WS, the greater of ambient water quality as of January 1, 2000, or 300 lag/l Total Recoverable Iron chronic = 1000 lag/l Dissolved Lead acute and chronic = TVS Dissolved Manganese chronic = For WS, the greater of ambient water quality as of January 1, 2000, or 50 lag/l Dissolved Manganese acute and chronic = TVS Total Recoverable Molybdenum chronic = 160 lag/l Total Mercury chronic = 0.01 lag/l Dissolved Nickel acute and chronic = TVS Dissolved Selenium acute and chronic = TVS Dissolved Silver acute and chronic = TVS Dissolved Zinc acute and chronic = TVS Note that on segment COLCLY02 sulfate, dissolved iron and dissolved manganese have water supply standards determined using existing quality as of January 1, 2000. Data from WQCD 12804 and 12803 were available for the Yampa River prior to January 1, 2000 and were used for this analysis. Based on 2 sample results from March 31, 1999, the ambient concentration of sulfate using the 85th percentile was 120 mg/l. Therefore, 250 mg/t is applied as the water supply standard for sulfate. The dissolved iron ambient concentration was 156 ug/l based on 2 samples from March 31, 1999. Therefore, 300 ug/l is applied as the water supply standard for dissolved iron. The ambient manganese concentration was 48 ug/l based on 2 samples from March 31, 1999. Therefore, 50 ug/l is applied as the water supply standard for dissolved manganese. Note that the temporary modification for chronic arsenic is specificied `hybrid', which applies "current condition" to discharges existing on or before 6/1/2013. This is further described in the Statement of Basis and Purpose, Regulation No. 37, September 30, 2013. The following standards from Regulation 31 were further evaluated in this analysis for outfall 002 based on the waste stream potentially discharging from that outfall. Outfall 002 can receive wash water from the floor drains which collect wastewater from vehicle maintenance activities. Table A -4d Additional Standards Being Evaluated Based on Regulation 31 at Outfall 002 Metals Benzene chronic = 2.2 gg/t Toluene chronic = 510 pg/1 Ethylbenzene chronic = 530 lag/l Anthracene (PAH) chronic = 2,100 pg/1 Benzo(a)anthracene (PAH) chronic = 0.0038 lag/t Benzo(a)pyrene (PAH) chronic = 0.0038 pg/1 Benzo(b)fluoranthene (PAH) chronic = 0.0038 lag/[ Benzo(k)fluoranthene (PAH) chronic = 0.0038 lag/l PagQe 13 of 40 4300 Cherry Creek Drive S., Denver, CO 80246-1530 p 303-692-2000 www.coLorado.gov/cdphe/wqcd I e�