OAR 340-041-0315: Basin-Specific Criteria (Umatilla): Water Quality Standards and Policies for this Basin

(1) pH (hydrogen ion concentration). pH values may not fall outside the following range: all Basin streams except the main stem Columbia River and the “constructed channel” segment of the West Division Main Canal: 6.5-9.0. When more than 25 percent of ambient measurements taken between June and September are greater than pH 8.7, and as resources are available according to priorities set by DEQ, DEQ will determine whether the values higher than 8.7 are anthropogenic or natural in origin. (2) The following criteria apply to the “constructed channel” segment of the West Division Main Canal and supersede the water quality standards in OAR 340-041-0011 through 340-041-0036 for the “constructed channel” segment of the canal. The criteria in (b) and (c) also apply to the “overflow channels” segment of the West Division Main Canal. (a) Canal waters may not exceed the numeric criteria shown in Table 315 from the uppermost irrigation withdrawal to the end of the “constructed channel” segment of the canal. (b) Toxic substances must not be present in canal waters in amounts likely to singularly or in combination harm the designated beneficial uses of the canal or downstream waters. (c) Sediment load and particulate size shall not exceed levels that interfere with irrigation or the other designated beneficial uses of the canal; (d) pH values may not fall outside the range of 4.5 to 9.0. (3) Minimum Design Criteria for Treatment and control of Sewage Wastes in this Basin: (a) During periods of low stream flows (approximately April 1 to October 31): Treatment resulting in monthly average effluent concentrations not to exceed 20 mg/l of BOD and 20 mg/l of SS or equivalent control; (b) During the period of high stream flows (approximately November 1 to April 30): A minimum of secondary treatment or equivalent control and unless otherwise specifically authorized by DEQ, operation of all waste treatment and control facilities at maximum practicable efficiency and effectiveness so as to minimize waste discharges to public waters. [ED. NOTE: To view attachments referenced in rule text, click here to view rule.]