OAR 340-041-0104: Basin-Specific Criteria (Main Stem Columbia River): Water Quality Standards and Policies Specific to the Main Stem Columbia River

(1) pH (hydrogen ion concentration). pH values may not fall outside the following range: main stem Columbia River (mouth to river mile 309): 7.0 – 8.5. (2) Total Dissolved Solids. Guide concentrations listed below must not be exceeded unless otherwise specifically authorized by DEQ upon such conditions as it may deem necessary to carry out the general intent of this plan and to protect the beneficial uses set forth in OAR 340-04l-0101: (a) Main stem Columbia River (river miles 120 to 147 and 218-309) — 200.0 mg/l; (b) All other river miles of main stem Columbia River — 500.0 mg/l. (3) Total Dissolved Gas. The Commission may modify the total dissolved gas criteria in the Columbia River for the purpose of allowing increased spill for salmonid migration. The Commission must find that: (a) Failure to act would result in greater harm to salmonid stock survival through in-river migration than would occur by increased spill; (b) The modified total dissolved gas criteria associated with the increased spill provides a reasonable balance of the risk of impairment due to elevated total dissolved gas to both resident biological communities and other migrating fish and to migrating adult and juvenile salmonids when compared to other options for in-river migration of salmon; (c) Adequate data will exist to determine compliance with the standards; and (d) Biological monitoring is occurring to document that the migratory salmonid and resident biological communities are being protected. (e) The Commission will give public notice and notify all known interested parties and will make provision for opportunity to be heard and comment on the evidence presented by others, except that the Director may modify the total dissolved gas criteria for emergencies for a period not exceeding 48 hours; (f) The Commission may, at its discretion, consider alternative modes of migration. (4) Minimum Design Criteria for Treatment and Control of Sewage Wastes: (a) During periods of low stream flows (see paragraphs 4(a)(A) and 4(a)(B) of this rule): Treatment resulting in monthly average effluent concentrations not to exceed 20 mg/l of BOD and 20 mg/l of SS or equivalent control. Periods of low stream flow vary throughout the main stem Columbia River. Low stream flow periods, by river mile, are: (A) River miles 120 to 147: Approximately July 1 to January 31; (B) River miles 147 to 218: Approximately May 1 to October 31. (b) During periods of high stream flows (see paragraphs 4(b)(A) and 4(b)(B) below): A minimum of secondary treatment or equivalent control and unless otherwise specifically authorized by the Department, operation of all waste treatment and control facilities at maximum practicable efficiency and effectiveness so as to minimize waste discharges to public waters. (A) River miles 120 to 147: Approximately February 1 to June 30; (B) River miles 147 to 218: Approximately November 1 to April 30.