R18-11-109. Numeric Water Quality Standards

A. E. coli bacteria. The following water quality standards for Escherichia coli (E. coli) are expressed in colony forming units per 100 milliliters of water (cfu / 100 ml) or as a Most Probable Number (MPN): E. coli FBC PBC Geometric mean (minimum of four samples in 30 days) 126 126 Statistical threshold value 410 576 B. pH. The following water quality standards for pH are expressed in standard units: pH DWS FBC, PBC, A&W 1 AgI AgL Maximum 9.0 9.0 9.0 9.0 Minimum 5.0 6.5 4.5 6.5 Footnotes: 1. “1” Includes A&Wc, A&Ww, A&Wedw, and A&We. C. The maximum allowable increase in ambient water temperature, due to a thermal discharge is as follows: A&Ww A&Wedw A&Wc 3.0° C 3.0° C 1.0° C D. Suspended sediment concentration. 1. The following water quality standards for suspended sediment concentration, expressed in milligrams per liter (mg/L), are expressed as a median value determined from a minimum of four samples collected at least seven days apart: A&Wc A&Ww 25 80 2. The Director shall not use the results of a suspended sediment concentration sample collected during or within 48 hours after a local storm event to determine the median value. E. Dissolved oxygen. A surface water meets the water quality standard for dissolved oxygen when either: 1. The percent saturation of dissolved oxygen is equal to or greater than 90 percent, or 2. The single sample minimum concentration for the designated use, as expressed in milligrams per liter (mg/L) is as follows: Designated Use Single sample minimum concentration in mg/L A&Ww 6.0 A&Wc 7.0 A&W edw for a sample taken from three hours after sunrise to sunset 3.0 A&W edw for a sample taken from sunset to three hours after sunrise 1.0 The single sample minimum concentration is the same for the designated use in a lake, but the sample must be taken from a depth no greater than one meter. F. Nutrient criteria. The following are water quality standards for total phosphorus and total nitrogen (expressed in milligrams per liter (mg/L)) that apply to the surface waters listed below. A minimum of 10 samples, each taken at least 10 days apart in a consecutive 12-month period, are required to determine a 90th percentile. Not more than 10 percent of the samples may exceed the 90th percentile value listed below. The Director will apply these water quality standards for total phosphorus and total nitrogen to the surface waters listed below, and to their perennial tributaries, if listed. The Director may also apply these total phosphorus and total nitrogen standards to any source discharging to any tributary (ephemeral, intermittent, effluent dependent water, or perennial) of the surface waters listed below, if necessary to protect nutrient water quality in the listed surface water, based on the volume, frequency, magnitude and duration of the discharge, and distance to the downstream surface water listed below: 1. Verde River and its perennial tributaries from the Verde headwaters to Bartlett Lake: Annual 90th Percentile Single Sample Maximum Total phosphorus 0.10 0.30 1.00 Total nitrogen 1.00 1.50 3.00 Surface Water Mean 2. Black River, Tonto Creek and their perennial tributaries for any segments that are not located on tribal lands: Annual 90th Percentile Single Sample Surface Water Mean Maximum Total phosphorus 0.10 0.20 0.80 Total nitrogen 0.50 1.00 2.00 3. Salt River and its perennial tributaries above Roosevelt Lake for any segments that are not located on tribal lands: Annual 90th Percentile Single Sample Maximum Total phosphorus 0.12 0.30 1.00 Total nitrogen 0.60 1.20 2.00 Surface Water Mean 4. Salt River below Stewart Mountain Dam to its confluence with the Verde River: Annual 90th Percentile Single Sample Maximum Total phosphorus 0.05 – 0.20 Total nitrogen 0.60 – 3.00 Surface Water Mean 5. Little Colorado River and its perennial tributaries upstream from: a. The headwaters to River Reservoir, b. South Fork of Little Colorado River at 34°00’49”/ 109°24’18” to above South Fork Campground at 34°04’49”/109°24’18”, and c. The headwaters of Water Canyon Creek to the Apache-Sitgreaves National Forest boundary: Single Sample Maximum Total phosphorus 0.08 0.10 0.75 Total nitrogen 0.60 0.75 1.10 Annual 90th Percentile Surface Water Mean 6. From the Little Colorado River and State Route 260 at 34°06’39”/109°18’55” to Lyman Lake: Single Sample Maximum Total phosphorus 0.20 0.30 0.75 Total nitrogen 0.70 1.20 1.50 Annual 90th Percentile Surface Water Mean 7. Colorado River at the Northern International Boundary near Morelos Dam: Single Sample Maximum Total phosphorus – 0.33 – Total nitrogen – 2.50 – Annual 90th Percentile Surface Water Mean 8. Oak Creek from its headwaters at 35°01'30"/111°44'12" to its confluence with the Verde River and the West Fork of Oak Creek from its headwaters at 35°02'44"/ 111°54'48" to its confluence with Oak Creek. Single Sample Maximum Total phosphorus 0.1 0.25 0.30 Total nitrogen 1.00 1.50 2.50 Annual 90th Percentile Surface Water Mean 9. No discharge of wastewater to Show Low Creek or its perennial tributaries upstream of and including Fools Hollow Lake shall exceed 0.16 mg/L total phosphates as P. 10. No discharge of wastewater to the San Francisco River or its perennial tributaries upstream of Luna Lake Dam shall exceed 1.0 mg/L total phosphates as P.