R18-11-605. Evaluating A Surface Water or Segment For Listing and Delisting

A. The Department shall compile and evaluate all reasonably current, credible, and scientifically defensible data to determine whether a surface water or segment is impaired or not attaining. B. Weight-of-evidence approach. 1. The Department shall consider the following concepts when evaluating data: a. Data or information collected during critical conditions may be considered separately from the complete dataset, when the data show that the surface water or segment is impaired or not attaining its designated use during those critical conditions, but attaining its uses during other periods. Critical conditions may include stream flow, seasonal periods, weather conditions, or anthropogenic activities; b. Whether the data indicate that the impairment is due to persistent, seasonal, or recurring conditions. If the data do not represent persistent, recurring, or seasonal conditions, the Department may place the surface water or segment on the Planning List; c. Higher quality data over lower quality data when making a listing decision. Data quality is established by the reliability, precision, accuracy, and representativeness of the data, based on factors identified in R18-11-602(A) and (B), including monitoring methods, analytical methods, quality control procedures, and the documented field and laboratory quality control information submitted with the data. The Department shall consider the following factors when determining higher quality data: i. The age of the measurements. Newer measurements are weighted heavier than older measurements, unless the older measurements are more representative of critical flow conditions; ii. Whether the data provide a direct measure of an impact on a designated use. Direct measurements are weighted heavier than measurements of an indicator or surrogate parameter; or iii. The amount or frequency of the measurements. More frequent data collection are weighted heavier than nominal datasets. 2. The Department shall evaluate the following factors to determine if the water quality evidence supports a finding that the surface water or segment is impaired or not attaining: a. An exceedance of a numeric surface water quality standard based on the criteria in subsections (C)(1), (C)(2), (D)(1), and (D)(2); b. An exceedance of a narrative surface water quality standard based on the criteria in subsections (C)(3) and (D)(3); c. Additional information that determines whether a water quality standard is exceeded due to a pollutant, suspected pollutant, or naturally occurring condition: i. Soil type, geology, hydrology, flow regime, biological community, geomorphology, climate, natural process, and anthropogenic influence in the watershed; ii. The characteristics of the pollutant, such as its solubility in water, bioaccumulation potential, sediment sorption potential, or degradation characteristics, to assist in determining which data more accurately indicate the pollutant’s presence and potential for causing impairment; and iii. Available evidence of direct or toxic impacts on aquatic life, wildlife, or human health, such as fish kills and beach closures, where there is sufficient evidence that these impacts occurred due to water quality conditions in the surface water. d. Other available water quality information, such as NPDES or AZPDES water quality discharge data, as applicable. e. If the Department determines that a surface water or segment does not merit listing under numeric water quality standards based on criteria in subsections (C)(1), (C)(2), (D)(1), or (D)(2) for a pollutant, but there is evidence of a narrative standard exceedance in that surface water or segment under subsection (D)(3) as a result of the presence of the same pollutant, the Department shall list the surface water or segment as impaired only when the evidence indicates that the numeric water quality standard is insufficient to protect the designated use of the surface water or segment and the Department justifies the listing based on any of the following: i. The narrative standard data provide a more direct indication of impairment as supported by professionally prepared and peer-reviewed publications; ii. Sufficient evidence of impairment exists due to synergistic effects of pollutant combinations or site-specific environmental factors; or iii. The pollutant is bioaccumulative, relatively insoluble in water, or has other characteristics that indicate it is occurring in the specific surface water or segment at levels below the laboratory detection limits, but at levels sufficient to result in an impairment. 3. The Department may consider a single line of water quality evidence when the evidence is sufficient to demonstrate that the surface water or segment is impaired or not attaining. C. Planning List. 1. When evaluating a surface water or segment for placement on the Planning List. a. Consider at least ten spatially or temporally independent samples collected over three or more temporally independent sampling events; and b. Determine numeric water quality standards exceedances. The Department shall: i. Place a surface water or segment on the Planning List following subsection (B), if the number of exceedances of a surface water quality standard is greater than or equal to the number listed in Table 1, which provides the number of Table 1. Minimum Number of Samples Exceeding the Numeric Standard MINIMUM NUMBER OF SAMPLES EXCEEDING THE NUMERIC STANDARD Number of Samples Number of Samples Exceeding Standard exceedances that indicate a minimum of a 10 percent exceedance frequency with a minimum of a 80 percent confidence level using a binomial distribution for a given sample size; or ii. For sample datasets exceeding those shown in Table 1, calculate the number of exceedances using the following equation: (Xx| n, p) where n = number of samples; p = exceedance probability of 0.1; x = smallest number of exceedances required for listing with “n” samples; and confidence level  80 percent. Number of Samples Number of Samples Exceeding Standard From To From To From To Number of Samples Number of Samples Exceeding Standard 10 15 3 173 181 22 349 357 41 16 23 4 182 190 23 358 367 42 24 31 5 191 199 24 368 376 43 32 39 6 200 208 25 377 385 44 40 47 7 209 218 26 386 395 45 48 56 8 219 227 27 396 404 46 57 65 9 228 236 28 405 414 47 66 73 10 237 245 29 415 423 48 74 82 11 246 255 30 424 432 49 83 91 12 256 264 31 433 442 50 92 100 13 265 273 32 443 451 51 101 109 14 274 282 33 452 461 52 110 118 15 283 292 34 462 470 53 119 126 16 293 301 35 471 480 54 127 136 17 302 310 36 481 489 55 137 145 18 311 320 37 490 499 56 146 154 19 321 329 38 500 57 155 163 20 330 338 39 164 172 21 339 348 40 2. When there are less than ten samples, the Department shall place a surface water or segment on the Planning List following subsection (B), if three or more temporally independent samples exceed the following surface water quality standards: a. The surface water quality standard for a pollutant listed in 18 A.A.C. 11, Article 1, Appendix A, Table 1, except for nitrate or nitrate/nitrite; b. The surface water quality standard for temperature or the single sample maximum water quality standard for suspended sediment concentration, nitrogen, and phosphorus in R18-11-109; c. The surface water quality standard for radiochemicals in R18-11-109(G); d. The surface water quality standard for dissolved oxygen under R18-11-109(E); e. The surface water quality standard for pH under R18-11-109(B); or f. The following surface water quality standards in R18-11-112: i. Single sample maximum standards for nitrogen and phosphorus, ii. All metals except chromium, or iii. Turbidity. 3. The Department shall place a surface water or segment on the Planning List if information in subsections (B)(2)(c), (B)(2)(d), and (B)(2)(e) indicates that a narrative water quality standard violation exists, but no narrative implementation procedure required under A.R.S. § 49-232(F) exists to support use of the information for listing. D. 303(d) List. 1. When evaluating a surface water or segment for placement on the 303(d) List. a. Consider at least 20 spatially or temporally independent samples collected over three or more temporally independent sampling events; and b. Determine numeric water quality standards exceedances. The Department shall: i. Place a surface water or segment on the 303(d) List, following subsection (B), if the number of exceedances of a surface water quality standard ii. For sample datasets exceeding those shown in Table 2, calculate the number of exceedances using the following equation: (Xx| n, p) where n = number of samples; p = exceedance probability of 0.1; x = smallest number of exceedances required for listing with “n” samples; and confidence level  90 percent. Table 2. Minimum Number of Samples Exceeding the Numeric Standard is greater than or equal to the number listed in Table 2, which provides the number of exceedances that indicate a minimum of a 10 percent exceedance frequency with a minimum of a 90 percent confidence level using a binomial distribution, for a given sample size; or MINIMUM NUMBER OF SAMPLES EXCEEDING THE NUMERIC STANDARD Number of Samples Number of Samples Exceeding Standard Number of Samples Number of Samples Exceeding Standard From To From To From To Number of Samples Number of Samples Exceeding Standard 20 25 5 174 182 24 344 352 43 26 32 6 183 191 25 353 361 44 33 40 7 192 199 26 362 370 45 41 47 8 200 208 27 371 379 46 48 55 9 209 217 28 380 388 47 56 63 10 218 226 29 389 397 48 64 71 11 227 235 30 398 406 49 72 79 12 236 244 31 407 415 50 80 88 13 245 253 32 416 424 51 89 96 14 254 262 33 425 434 52 97 104 15 263 270 34 435 443 53 105 113 16 271 279 35 444 452 54 114 121 17 280 288 36 453 461 55 122 130 18 289 297 37 462 470 56 131 138 19 298 306 38 471 479 57 139 147 20 307 315 39 480 489 58 148 156 21 316 324 40 490 498 59 157 164 22 325 333 41 499 500 60 165 173 23 334 343 42 2. The Department shall place a surface water or segment on the 303(d) List, following subsection (B) without the required number of samples or numeric water quality standard exceedances under subsection (D)(1), if either the following conditions occur: a. More than one temporally independent sample in any consecutive three-year period exceeds the surface water quality standard in: i. The acute water quality standard for a pollutant listed in 18 A.A.C. 11, Article 1, Appendix A, Table 2 and the acute water quality standards in R18-11-112; ii. The surface water quality standard for nitrate or nitrate/nitrite in 18 A.A.C. 11, Article 1, Appendix A, Table 1; or iii. The single sample maximum water quality standard for bacteria in subsections R18-11- 109(A). b. More than one exceedance of an annual mean, 90th percentile, aquatic and wildlife chronic water quality standard, or a bacteria 30-day geometric mean water quality standard occurs, as specified in R18-11-109, R18-11-110, R18-11-112, or 18 A.A.C. 11, Article 1, Appendix A, Table 2. 3. Narrative water quality standards exceedances. The Department shall place a surface water or segment on the Planning List if the listing requirements are met under A.R.S. § 49-232(F). E. Removing a surface water, segment, or pollutant from the Planning List or the 303(d) List. 1. Planning List. The Department shall remove a surface water, segment, or pollutant from the Planning List when: a. Monitoring activities indicate that: i. There is sufficient credible data to determine that the surface water or segment is impaired under subsection (D), in which case the Department shall place the surface water or segment on the 303(d) List. This includes surface waters with an EPA approved TMDL when the Department determines that the TMDL strategy is insufficient for the surface water or segment to attain water quality standards; or ii. There is sufficient credible data to determine that the surface water or segment is attaining all designated uses and standards. b. All pollutants for the surface water or segment are delisted. 2. 303(d) List. The Department shall: a. Remove a pollutant from a surface water or segment from the 303(d) List based on one or more of the following criteria: i. The Department developed, and EPA approved, a TMDL for the pollutant; ii. The data used for previously listing the surface water or segment under R18-11-605(D) is superseded by more recent credible and scientifically defensible data meeting the requirements of R18-11-602, showing that the surface water or segment meets the applicable numeric or narrative surface water quality standard. When evaluating data to remove a pollutant from the 303(d) List, the monitoring entity shall collect the more recent data under similar hydrologic or climatic conditions as occurred when the samples were taken that indicated impairment, if those conditions still exist; iii. The surface water or segment no longer meets the criteria for impairment based on a change in the applicable surface water quality standard or a designated use approved by EPA under section 303(c)(1) of the Clean Water Act; iv. The surface water or segment no longer meets the criteria for impairment for the specific narrative water quality standard based on a change in narrative water quality standard implementation procedures; v. A re-evaluation of the data indicate that the surface water or segment does not meet the criteria for impairment because of a deficiency in the original analysis; or vi. Pollutant loadings from naturally occurring conditions alone are sufficient to cause a violation of applicable water quality standards; b. Remove a surface water, segment, or pollutant from the 303(d) List, based on criteria that are no more stringent than the listing criteria under subsection (D); c. Remove a surface water or segment from the 303(d) List if all pollutants for the surface water or segment are removed from the list; d. Remove a surface water, segment, or pollutant, from the 303(d) List and place it on the Planning List, if: i. The surface water, segment or pollutant was on the 1998 303(d) List and the dataset used in the original listing does not meet the credible data requirements under R18-11-602, or contains insufficient samples to meet the data requirements under subsection (D); or ii. The monitoring data indicate that the impairment is due to pollution, but not a pollutant.