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Home My WebLink About2024 303d Listing Methodology_Final_1 2024 303(d) LISTING AND DELISTING METHODOLOGY North Carolina Approved by the North Carolina Environmental Management Commission on September 8, 2022 CONTENTS INTRODUCTION .................................................................................................................................................................... 1 WATER QUALITY STANDARDS AND CLASSIFICATIONS ...................................................................... 1 CLEAN WATER ACT SECTIONS 305(B) AND 303(D) ....................................................................................... 1 303(D) LIST AND ASSESSMENT METHODOLOGY PUBLIC COMMENT .................................................... 2 EPA APPROVAL OF THE 303(D) LIST ..................................................................................................................... 2 DATA WINDOW AND DATA SETS FOR 303(D) LIST ........................................................................................ 2 ASSESSMENT UNIT DELINEATION .......................................................................................................................... 3 ASSESSMENT METHODS ................................................................................................................................................... 3 1. ASSESSING NUMERIC CRITERIA .................................................................................................................. 4 DELISTING WATERS ...................................................................................................................................................... 4 CHLOROPHYLL A (AQUATIC LIFE) CRITERIA ..................................................................................................... 5 DISSOLVED OXYGEN (AQUATIC LIFE) CRITERIA .............................................................................................. 5 MBAS (WATER SUPPLY) CRITERIA ......................................................................................................................... 5 MERCURY -WATER COLUMN (FISH CONSUMPTION) CRITERIA ................................................................ 5 NITRATE/NITRITE (WATER SUPPLY) CRITERIA.............................................................................................. 5 PH (AQUATIC LIFE) CRITERIA ................................................................................................................................... 5 TEMPERATURE (AQUATIC LIFE) CRITERIA ........................................................................................................ 6 TOXIC SUBSTANCES ....................................................................................................................................................... 6 ARSENIC (AQUATIC LIFE) (WATER SUPPLY) (HUMAN HEALTH) CRITERIA ....................................... 6 CADMIUM (AQUATIC LIFE) CRITERIA ................................................................................................................... 6 CHLORIDE (AQUATIC LIFE) CRITERIA .................................................................................................................. 6 CHLORINE (AQUATIC LIFE) CRITERIA .................................................................................................................. 6 CHROMIUM (AQUATIC LIFE) CRITERIA ................................................................................................................ 6 COPPER (AQUATIC LIFE) CRITERIA........................................................................................................................ 6 CYANIDE (AQUATIC LIFE) CRITERIA ..................................................................................................................... 6 FLUORIDE (AQUATIC LIFE) CRITERIA ................................................................................................................... 7 LEAD (AQUATIC LIFE) CRITERIA ............................................................................................................................. 7 NICKEL (AQUATIC LIFE) (WATER SUPPLY) CRITERIA .................................................................................. 7 ZINC (AQUATIC LIFE) CRITERIA .............................................................................................................................. 7 TURBIDITY (AQUATIC LIFE) CRITERIA ................................................................................................................. 7 2. ASSESSING NARRATIVE AQUATIC LIFE CRITERIA USING BIOLOGICAL RATINGS ... 7 DELISTING WATERS ...................................................................................................................................................... 7 3. ASSESSING RECREATION CRITERIA USING PATHOGEN INDICATORS ......................... 8 FECAL COLIFORM BACTERIA CRITERIA ............................................................................................................... 8 DELISTING WATERS ...................................................................................................................................................... 8 ENTEROCOCCI BACTERIA CRITERIA ...................................................................................................................... 8 DELISTING WATERS ...................................................................................................................................................... 8 4. ASSESSING SHELLFISH HARVESTING CRITERIA USING GROWING AREA CLASSIFICATION .......................................................................................................................................................... 9 DELISTING WATERS ...................................................................................................................................................... 9 5. ASSESSING FISH CONSUMPTION CRITERIA USING ADVICE AND ADVISORIES ......... 9 DELISTING WATERS ...................................................................................................................................................... 9 APPENDIX A. NUMERIC CRITERIA ASSESSMENT FLOWCHARTS ............................................................... 10 1 INTRODUCTION The water quality assessment process is a framework used by the North Carolina Division of Water Resources to interpret data and information to determine whether a waterbody is meeting water quality standards. This framework is critical to providing a balanced and consistent comparison of data and information with North Carolina water quality standards. WATER QUALITY STANDARDS AND CLASSIFICATIONS Water quality standards are an integral part of water quality assessment. Water quality standards are state regulations as rules that form the foundation of controls that protect lakes, rivers, streams and other waterbodies from pollution. These rules, once adopted by the North Carolina Environmental Management Commission (EMC), must be approved by the US Environmental Protection Agency to ensure compliance with the Clean Water Act. The rules are in Title 15A of the North Carolina Administrative Code (NCAC). These rules include: 1. Beneficial use designations (classifications) (e.g., recreation, water supply, aquatic life) 2. Water quality criteria as numeric levels and/or narrative statements with accompanying frequency, magnitude and duration protective of the beneficial use designations. Under the Clean Water Act, states must review their water quality standards and classifications every three years and make any modifications necessary to meet federal requirements and to protect waters of the state. This process is known as the Triennial Review. Surface water classifications are designations applied to surface water bodies, such as streams, rivers and lakes, which define the best uses to be protected within these waters, and carry with them an associated set of water quality criteria to protect those uses. Surface water classifications are one tool that state and federal agencies use to manage and protect all streams, rivers, lakes, and other surface waters in North Carolina. Each classification has associated criteria that are used to determine if the designated uses are being protected. For detailed information on Water Quality Standards and Classifications please visit https://deq.nc.gov/about/divisions/water-resources/planning/classification- standards. CLEAN WATER ACT SECTIONS 305(B) AND 303(D) The 305(b) report and 303(d) list are products of the water quality assessment. Under federal law and regulation, States must perform a water quality assessment every two years and report results to EPA. The 305(b) report is a list of all waters in the state with associated assessments. The 303(d) list is part of the 305(b) report. The 303(d) list is a list of waters that exceed water quality criteria, and are “impaired” as determined through the listing methodology as approved by the Environmental Management Commission, and need a TMDL. The name of the list comes from Section 303(d) of the federal Clean Water Act (CWA), which requires States to identify and 2 establish a priority ranking for waterbodies for which existing controls are not stringent enough to attain and maintain applicable water quality standards, and to establish total maximum daily loads (TMDLs) for the pollutants responsible. This portion of the CWA is codified in 33 U.S.C. § 1313. 303(D) LIST AND ASSESSMENT METHODOLOGY PUBLIC COMMENT The NC Environmental Management Commission, in accordance with NCGS § 143B-282(c), will “implement the provisions of subsections (d) and (e) of 33 U.S.C. § 1313 by identifying and prioritizing impaired waters…” The NC Environmental Management Commission will provide the public an opportunity to review and comment on any significant proposed changes to the methodology used for creating the 303(d) list. The Environmental Management Commission will strive to provide the public comment opportunity in even-numbered years prior to the assessment in the following odd-numbered year. An additional public comment opportunity to review the draft 303(d) list will also be provided in the months before the list is submitted to the Environmental Protection Agency for approval. EPA APPROVAL OF THE 303(D) LIST Federal law requires the State to submit a 303(d) list to EPA every two years, by April 1st of every even numbered year. Because 303(d) is a federal program under the Clean Water Act, EPA has final authority on the 303(d) list. EPA reviews the state-submitted 303(d) list and may include additional waters that they determine should be included on the list based on their opinions and policies. DATA WINDOW AND DATA SETS FOR 303(D) LIST Data that does not pass the Quality Assurance process shall not be used in determining the assessment of waterbodies for 303(d) purposes. Data once extracted from the EPA Storet Database are further scrutinized and filtered by the DWR to assure only the highest quality data are used for assessment purposes. See Table of Data Qualifiers. Data and information used for the 2024 assessment were collected in calendar years 2018-2022. For 2024 assessment, newer data are defined as data collected during calendar years 2021 and 2022. Assessments based on older data are carried forward if newer data or information were not available to change the previous assessment decision. Older data will not be automatically excluded particularly when its inclusion could be used to augment small sets of more current data. For the 2024 303(d) assessment, the state will augment small sets of current data (i.e. when n<10) with the previous five years of data (2013-2017) where available. NC will require a minimum of three exceedances in the current data set for inclusion on the 303(d) list. 3 ASSESSMENT UNIT DELINEATION Section 303(d) of the Clean Water Act and the EPA's implementing regulations in the Code of Federal Regulations at 40 C.F.R. section 130.7, require states to identify water quality limited segments (WQLS) still requiring Total Maximum Daily Loads (TMDLs) within their jurisdictions. The resulting list of WQLSs is the State’s section 303(d) List. WQLS are defined in 40 C.F.R. section 130.2(j) as “[a]ny segment where it is known that water quality does not meet applicable water quality standards, and/or is not expected to meet applicable water quality standards, even after the application of the technology-based effluent limitations required by sections 301(b) and 306 of the Act.” In North Carolina, WQLS are spatially established by geographically defined assessment units (AUs). The base dataset for assessment units is the USGS 1:100,000 scale hydrography or the map of named streams in NC. NC has augmented this by adding some of the many unnamed streams from the 1:24,000 (more detailed stream map) scale hydrography. Since the 1950's NC has been classifying streams for various uses. For the most part, AUs are the same as the classified named waters. However, this methodology recognizes that unforeseen environmental settings may complicate the assessment scenario and thereby require adaptability of the assessment scale. Therefore, during the assessment process, an AU may be re-segmented, or split into smaller units, to define a WQLS because of assessment result differences between stations in the same AU for any of the assessed parameters or drainage area characteristics (e.g., major tributaries, land use changes). In general, assessments are usually applied only to the AU where the data are collected with minimal extrapolation. It is worth noting, that regardless of using a stream segment as the defaulting listing scale, upstream waters must protect downstream uses, and all upstream sources will be considered when addressing the impairment. For implementation purposes all activities in AUs in the entire upstream drainage area could be subject to management measures or TMDLs to address identified criteria exceedances (Category 4 or 5 assessments). ASSESSMENT METHODS There are five different general assessment methods for water quality standards assessment: 1) 10% exceedance method with 90% statistical confidence, used for most numeric water quality standards. 2) Biological rating method used to assess benthic and fish community collections. 3) Pathogen criteria method to assess recreation standards. 4) Shellfish growing area assessment method to assess waters classified as “SA”. 5) Fish advice and advisories with fish tissue data method to assess fish consumption. More than one method could be used on any individual AU (i.e. Assessment Unit, waterbody segment, or waterbody) depending on the data available and the water quality classification. 4 1. ASSESSING NUMERIC CRITERIA The following sets of evaluations will be used for the 2024 assessment for these parameters: chlorophyll-a, dissolved oxygen, MBAS, mercury, nitrate/nitrite, pH, temperature, toxic substances, and turbidity. For each parameter there is a brief discussion of the standard used for assessment of the parameter including any parameter-specific good causes for not assessing in Category 5. Note Category 5 is the 303(d) list. The true frequency of criteria exceedances cannot be measured. It must be estimated from a set of samples, which introduces uncertainty. The degree of uncertainty depends on the sample size. NC will use a nonparametric hypothesis testing approach based on the binomial distribution. The binomial method allows a quantifiable level of statistical confidence (90%) for listing decisions, which provides a 10% probability of listing an assessment unit when it should not be listed. The null hypothesis is that the overall exceedance probability is less than or equal to the 10% exceedance allowance. NC will also consider the number of excursions of criterion for newer data that have not been assessed before. For 2024 assessment, newer data are defined as data collected during calendar years 2021 and 2022. • Exceeding Criteria-Category 5 o Sample size is greater than nine. o Greater than 10% exceedance with greater than or equal to 90% confidence, or o Greater than 10% exceedance, but less than 90% statistical confidence, and greater than 3 excursions with 90% statistical confidence in exceeding criteria in newer data that have previously not been assessed. The flowcharts for listing and delisting waters when assessing numeric criteria are also provided for reference in Appendix A. The standards (criteria) and additional considerations are included for each parameter as applicable. DELISTING WATERS NC will review the final 2022 303(d) list as the starting point for the development of the 2024 303(d) list. All waters on the 2022 303(d) list will be evaluated for appropriate inclusion on the 2024 303(d) list as defined in 40 CFR 130.2(j). NC will apply a combination of nonparametric hypotheses testing based on the binomial distribution as well as an analysis of the dates of excursions to determine if there is good cause to delist a water. An analysis of newer data that have not been previously assessed is included in the delisting procedure to allow the state to determine if criterion excursions are more recent. For delisting waters for non-toxic parameters, if the 2024 assessment results in greater than 10% exceedance rate with less than 90% statistical confidence and the water was on the 2022 303(d) list, the water will be delisted if there are less than 2 excursions of the criterion in newer data that have not been previously assessed. If the 2024 assessment results in less than 10% exceedance rate and the water was on the 2022 303(d) list, the water will be delisted if there is greater than 40% statistical confidence that there is less than a 10% exceedance of the criterion or if there are less than 3 excursions of the criterion in newer data that have not been previously assessed. For legacy total metals impairments, where total criteria were replaced with dissolved criteria in January 2015, DWR will delist assessments for total metals only when current dissolved metals data are available for assessment. 5 CHLOROPHYLL A (AQUATIC LIFE) CRITERIA Chlorophyll a (corrected): Not greater than 15 g/l in trout waters. Not greater than 40 g/l for lakes, reservoirs, and other waters subject to growths of macroscopic or microscopic vegetation. DISSOLVED OXYGEN (AQUATIC LIFE) CRITERIA The dissolved oxygen (DO) criterion for trout waters is not less than 6.0 mg/l. For non-trout waters it is not less than 4.0 mg/l with a daily average of not less than 5.0 mg/l. The DO criterion for salt waters is 5.0 mg/l. There are exceptions to these standards for classified Sw or swamp waters, lake coves or backwaters, lake bottom waters, poorly flushed tidally influenced streams or embayments and estuarine bottom waters if the lower values are due to natural conditions. • Exceeding Criteria-Category 5 o Sample size is greater than nine. o AU is not a class Sw or swamp like. o Greater than 10% exceedance with greater than or equal to 90% confidence, or o Greater than 10% exceedance, but less than 90% statistical confidence, and greater than 3 excursions with 90% statistical confidence in exceeding criteria in newer data that have not been previously assessed. MBAS (WATER SUPPLY) CRITERIA The MBAS (methylene blue active substances) criterion is not to exceed 0.5 mg/l in water supply waters. This criterion is to protect aesthetic quality of water supplies and to prevent foaming. MERCURY -WATER COLUMN (FISH CONSUMPTION) CRITERIA The mercury criterion is 0.012 g/l for all NC waters. NITRATE/NITRITE (WATER SUPPLY) CRITERIA The NO2+NO3-N criterion is 10 mg/l for water supply waters. PH (AQUATIC LIFE) CRITERIA The pH criteria are between 6.0 and 9.0 standard units for freshwater and between 6.8 and 8.5 for saltwater. pH can be as low as 4.3 for classified swamp waters if this is due to natural conditions. NC has an exception process for waters that are swamp-like but are not formally classified as Sw or swamp waters. These swamp-like waters are in the coastal plain and are usually near classified Sw waters or have been sampled using swamp biocriteria. Swamp streams stop flowing in summer months, but have visible flow during late winter. For more information, see the Benthos SOP at 6 https://deq.nc.gov/about/divisions/water-resources/water-resources-data/water-sciences- home-page/biological-assessment-branch. • Exceeding Criteria-Category 5 o Sample size is greater than nine. o AU is not a class Sw or swamp like. o Greater than 10% exceedance with greater than or equal to 90% confidence, or o Greater than 10% exceedance, but less than 90% statistical confidence, and greater than 3 excursions with 90% statistical confidence in exceeding criteria in newer data that have not been previously assessed. TEMPERATURE (AQUATIC LIFE) CRITERIA The temperature criteria are 29 °C for mountains and Piedmont AUs, 32°C for lower Piedmont and coastal plain waters and 20°C for supplemental classified Trout waters. See full standard for details. TOXIC SUBSTANCES ARSENIC (AQUATIC LIFE) (WATER SUPPLY) (HUMAN HEALTH) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” CADMIUM (AQUATIC LIFE) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” CHLORIDE (AQUATIC LIFE) CRITERIA The chloride criterion is not to exceed 230 mg/l in all freshwaters. CHLORINE (AQUATIC LIFE) CRITERIA The chlorine (residual) criterion is not to exceed 17 g/l in all freshwaters. CHROMIUM (AQUATIC LIFE) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” COPPER (AQUATIC LIFE) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” CYANIDE (AQUATIC LIFE) CRITERIA The cyanide criterion is not to exceed 5 g/l in all freshwaters. 7 FLUORIDE (AQUATIC LIFE) CRITERIA The fluoride criterion is not to exceed 1.8 mg/l in all freshwaters. LEAD (AQUATIC LIFE) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” NICKEL (AQUATIC LIFE) (WATER SUPPLY) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” ZINC (AQUATIC LIFE) CRITERIA See Table: “North Carolina Surface Water Pollutant Standards for Metals, Effective 01/01/2015” TURBIDITY (AQUATIC LIFE) CRITERIA The turbidity criteria are 50 nephalometric turbidity units (NTU) for freshwaters, 25 NTU for reservoirs and estuarine waters, and 10 NTU for supplemental classified Trout waters. 2. ASSESSING NARRATIVE AQUATIC LIFE CRITERIA USING BIOLOGICAL RATINGS Narrative criterion: Waters shall be suitable for aquatic life propagation and maintenance of biological integrity. NC uses benthic and fish community data to assess biological integrity. Biological integrity means the ability of an aquatic ecosystem to support and maintain a balanced and indigenous community of organisms having species composition, diversity, population densities and functional organization similar to that of reference conditions (15A NCAC 02B .0202). Refer to https://deq.nc.gov/about/divisions/water-resources/water-resources-data/water- sciences-home-page/biological-assessment-branch for more information on the biological monitoring program including SOPs. • Exceeding Criteria-Category 5 o Poor, Fair, and Severe biological ratings. DELISTING WATERS Assessments for fish and benthic community ratings will be removed from Category 5 when meeting criteria as follows: • Meeting Criteria-Category 1 o Excellent, Natural, Good, Good-Fair, Moderate, Not Impaired biological ratings. 8 3. ASSESSING RECREATION CRITERIA USING PATHOGEN INDICATORS FECAL COLIFORM BACTERIA CRITERIA The criteria are for fecal coliforms not to exceed a geometric mean of 200/100 ml (MF count) based on at least five consecutive samples examined during any 30-day period and not to exceed 400/100 ml in more than 20 percent of the samples examined during such period. NC uses this standard as the assessment method in freshwaters. • Exceeding Criteria-Category 5 o There are at least five samples collected within a 30-day period, and • Geometric mean is greater than 200 colonies/100ml of water, or • Greater than 20% of the samples exceed 400 colonies/100ml. DELISTING WATERS Assessments for fecal coliform bacteria will be removed from category 5 when meeting criteria as follows: • Meeting Criteria-Category 1 o Geometric mean is less than 200 colonies/100ml of water in monthly samples, and o Less than 20% of the samples exceed 400 colonies/100ml in monthly samples. ENTEROCOCCI BACTERIA CRITERIA The enterococcus criterion in NC is not to exceed a geometric mean of 35 enterococci per 100 ml based upon a minimum of five samples within any consecutive 30 days. NC uses this criterion for assessment of saltwaters. Data for this assessment are collected by Division of Marine Fisheries (DMF) Recreational Water Quality Monitoring program (https://www.deq.nc.gov/about/divisions/marine-fisheries/shellfish-sanitation-and-recreational- water-quality/recreational-water-quality). • Exceeding Criteria-Category 5 o There are at least five samples collected within a 30-day period, and o Geometric mean is greater than 35 enterococci per 100 ml, or o In the case where a DMF station has multiple events where there are 5 or more samples in 30 days: greater than 10 percent of 5 and 30 sampling events exceed a geometric mean of 35 enterococci per 100 ml with 90 percent statistical confidence. DELISTING WATERS Assessments for enterococci bacteria will be removed from category 5 when meeting criteria as follows: • Meeting Criteria-Category 1 o Geometric mean is less than 35 enterrococci/100ml of water in monthly samples. 9 4. ASSESSING SHELLFISH HARVESTING CRITERIA USING GROWING AREA CLASSIFICATION Waters that are classified for shellfish harvesting for market purposes (Class SA) are assessed using https://www.deq.nc.gov/about/divisions/marine-fisheries/shellfish-sanitation-and-recreational- water-quality/shellfish-growing-areas. These classifications are based on fecal coliform exceedances and sanitary surveys. • Exceeding Criteria-Category 5 o Class SA water, and o Growing area classification is Not Approved. DELISTING WATERS Assessments for shellfish harvesting will be removed from category 5 when meeting criteria as follows: • Meeting Criteria-Category 1 o Growing area is classified as Approved for shellfish harvesting. 5. ASSESSING FISH CONSUMPTION CRITERIA USING ADVICE AND ADVISORIES Fish consumption was assessed based on site-specific fish consumption advisories developed using fish tissue data. Advisories and advice are developed by DHHS using fish tissue data collected by DWR and others. See http://epi.publichealth.nc.gov/fish/current.html for all advice and advisories. • Exceeding Criteria-Category 5 o Fish consumption advisory in place for AU, and o AU has site specific fish tissue data. DELISTING WATERS Assessments for fish consumption will be removed from category 5 when meeting criteria as follows: • Meeting Criteria-Category 1 o Fish Consumption advisory is no longer in place, and o AU has site specific fish tissue data. 10 APPENDIX A. NUMERIC CRITERIA ASSESSMENT FLOWCHARTS