Colorado's Section 303(d) Listing Methodology

Transcription

1 SECTION 303(d) LISTING METHODOLOGY Listing Cycle I. INTRODUCTION II. LISTING PROCESS III. LISTING CRITERIA A.. Existing and Readily Available Data B. Credible Evidence 4. Physical and biological assessments must be performed in accordance with scientifically sound methodologies. All such assessments should be performed by an observer who has training and experience in performing such evaluations. Assessment reports should include a statement of the observer's qualifications and should reference the protocols utilized. Any departures from referenced protocols and methodologies should be documented and the basis for any such departure addressed. Though currently under review and subject to future revision, a specific method has been developed for use in demonstrating attainment or non-attainment of assigned aquatic life uses due to sediment deposition. The document titled Implementation Guidance for Determining Sediment Deposition Impacts to Aquatic Life in Streams and Rivers ; WQCC Policy 98-1 is available either in hard copy or electronically on the Colorado Water Quality Control Commission web site. The Division will generally accept methodologies and protocols in use by the US Geological Survey, US Forest Service, US Bureau of Land Management, US Environmental Protection Agency, Colorado Division of Wildlife, or others, when well-documented, widely available and suitable for their intended purpose. The Division s determination of the acceptability or unacceptability of any such protocol will be included in the Division's discussion of data sources that the Division includes in the Section 303(d) List. C. Data Interpretation 1. Chemical Data - General 2. Chemical Data - Lakes and Reservoirs 3. Biological and Physical Data 4. Assessment of Temperature Data (starting on page 12) {1 st paragraph is moved down} List Meth Temp v2 1 10/11/06

2 A determination that the statewide narrative temperature standard is not attained relies upon a showing both that the aquatic life use is not supported and that an anthropogenic modification of the water temperature has occurred. Interpretation of biological and physical data is discussed above. Assessment of temperature data is discussed below. The numerical temperature standard criterion is evaluated against representative instream data. Temperature varies within a reach both spatially and temporally, e.g. summer and winter. Data should be taken from a location in the stream that is representative of the reach at the time the data are collected. For example, data should not be relied upon that is taken only in locations that may be substantially warmer or cooler than the rest of the segment e.g. backwater habitats, eddies, deep pools, or refugia. a. Summertime Maximum: i. Chronic- Attainment of a the chronic numerical the temperature standard is based on a Maximum Weekly Average Temperature (MWAT), unless otherwise specified in a site-specific standard. The MWAT is defined as an implementation statistic that is calculated from field monitoring data. The MWAT is calculated as the largest mathematical mean of multiple, equally spaced, daily temperatures over a seven-day consecutive period, with a minimum of three data points spaced equally through the day. MWAT are not to be overlapped, i.e. temperature data used in the calculation of one exceedance of an MWAT will not be used in any other exceedance calculation. II. Acute- Attainment of the acute numerical temperature standard is based on a Daily Maximum (DM) water temperature, unless otherwise specified in a site-specific standard. The DM is defined as the highest instantaneous water temperature recorded during a given 24-hour period b. Normal Pattern of Spatial Diversity Temperature profiles will be gathered from multiple locations and habitat types along the reach being investigated. Comparisons will be made with the expected thermal regime. Significant deviation from the expected normal regime should be avoided. c. Normal Pattern of Temporal Fluctuation The maximum temperature change shall not exceed 3 C in addition to temperature changes caused by normal conditions. 5. Assessment of "All Tributary " segments D. Determination of Impairment List Meth Temp v2 2 10/11/06

3 1. Impairment Where the Pollutant is Unknown The federal Clean Water Act defines pollution as the man-made or maninduced alteration of the chemical, physical, biological, and radiological integrity of water, CWA 502(19). Pollution may result from the introduction of pollutants or from causative factors other than pollutants. Pollutants are defined in the federal Clean Water Act at 502(6) to include dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials (except those regulated under Atomic Energy Act of 1954, as amended), heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and agricultural waste discharged into water. Notwithstanding the federal definition cited above, certain radiological constituents are also regulated under the State s Water Quality Control Act and are considered to be pollutants. TMDL development is required in those instances where one or more pollutants are the cause of non-attainment. TMDLs are not required where the impairment is the result of pollution that is not a pollutant. Water bodies with classified uses that are impaired but it is unclear whether the cause of impairment is attributable to pollutants as opposed to pollution will be placed on the M&E List provisionally listed on the Section 303(d) List. The List will include a notation identifying water bodies that are provisionally listed. For water bodies that are provisionally listed on the Section 303(d) List, the Division, in cooperation with other interested persons, will undertake water quality monitoring and/or other water quality studies and assessments to determine whether the cause of the impairment is a pollutant. There will be a general goal of making this determination within seven years of provisionally listing any water body. No TMDL will be developed for a provisionally listed water body unless and until it is determined that the cause of the impairment is one or more pollutants. If the monitoring, study and assessment determines that the cause of impairment is one or more pollutants, the Division will proceed with development of a TMDL. If the monitoring, study and assessment determines that the cause of impairment is not a pollutant, no TMDL will be developed and the Division will recommend the water body for delisting in the next Section 303(d) List review cycle. The fact that a water body is provisionally listed will not result in a prohibition of new or expanded discharges into the segment prior to the determination whether the impairment is caused by a pollutant. To the extent it is known that a pollutant is the cause of the impairment, but the identity of the specific pollutant is not yet known, the water body segment List Meth Temp v2 3 10/11/06

4 will be listed. However, the fact that the water body is so listed will not result in a prohibition of new or expanded discharges into the segment until the pollutant is identified. Permits may be affected once the pollutant is identified. 2. Impairment of Numeric Standards Attainment of numeric chemical standards is assessed by comparison of ambient water quality against assigned standards. Assessment of chemical data considers attainment of both chronic and acute aquatic life use-based chemical standards, where both chronic and acute standards have been assigned to a given waterbody. e. Temperature: Where site-specific numeric temperature standards have been adopted by the Commission, listing decisions may be made solely on the basis of attainment of the numeric criteria.in cold water streams and lakes tthe MWAT or DM is not to exceed the applicable numeric standard more than 1 time in a three-year period. In warm water streams and lakes the MWAT is not to exceed the MWAT of 30ºC more than 1 time in a three-year period. f. Vertical Profiles: and so forth 3. Impairment of Narrative Standards and Classified Uses Impairment of narrative standards and classified uses may be supported by chemical data and/or information generated by biological and/or physical assessments. In instances where a determination of impairment is based solely upon biological and/or physical assessments, such assessments must provide clear and convincing evidence of non-attainment. a. Aquatic Life Use For aquatic life uses, as previously referenced, the Division will generally consider impairment of narrative standards and classified uses to be demonstrated when either the physical/habitat data (except for temperature) or biological community metrics reflect a condition that is significantly less than the expected or reference condition. The Division will evaluate impairment of narrative temperature standards in accordance with subsection III D 3 c, and numerical temperature standards in accordance with subsection III D 2. When such data do not indicate specific pollutant(s) causing non-attainment, the Division will recommend placing the segment on the M&E List for further study. b. Water Supply Use: For water supply uses, the Division will consider chemical data, biological and/or physical assessments that provide clear and convincing evidence of non-attainment. Such impairment may be demonstrated by chemical data documented at levels toxic to humans. The Division will utilize Commission Policy 96-2, Human Health-Based List Meth Temp v2 4 10/11/06

5 Water Quality Criteria and Standards, in any determination of impairment based upon such information. Impairment decisions may also be supported by biological and physical data presenting overwhelming evidence of impairment due to color, taste and odor. In-situ bioassay, or other ambient toxicity test results which demonstrate statistically significant lethal or sub-lethal adverse effects and which are supported by biological information demonstrating adverse impacts to aquatic community health, composition, or productivity, in comparison to an appropriate reference condition, will result in a decision of impairment. In general, interpretation of toxicity test results will conform to applicable portions of the Laboratory Guidelines for Conducting Whole Effluent Toxicity Tests (WQCD, 1998) and the Biomonitoring Guidance Document (WQCD, 2002). For lakes and reservoirs, impairment may be demonstrated where acute conditions (typically low DO levels) result in significant fish kills. Fish kills associated with accidental spills or isolated unauthorized discharges of toxics will not typically be considered a basis for listing. c. Narrative Temperature Standards: A segment shall not be listed as impaired for temperature based solely on non-attainment of the narrative temperature standards. A segment will be listed as impaired for temperature only if there is non-attainment of a site specific numerical temperature standard. d. Narrative Sediment Standards:A determination that the statewide narrative sedment standard is not attained also relies upon a showing both that the aquatic life use is not supported and that sediment is deposited on the bottom of surface waters. Though currently under review and subject to future revision, a specific method has been developed for use in demonstrating attainment or non-attainment of assigned aquatic life uses due to sediment deposition. The document titled Implementation Guidance for Determining Sediment Deposition Impacts to Aquatic Life in Streams and Rivers ; WQCC Policy 98-1 is available either in hard copy or electronically on the Colorado Water Quality Control Commission web site. (moved from III B) IV. 4. Listing Based on Fish Consumption Advisories (FCA) PRIORITIZATION FOR TMDL DEVELOPMENT List Meth Temp v2 5 10/11/06