2020 303(d) Listing Methodology Workgroup October 16, 2018 CDPHE - C1A, 1-3 pm
Introductions 2 303(d) Listing Methodology
Agenda Time Agenda Topic Lead Skip Feeney 1:00 pm Introductions Address lower confidence limit Skip Feeney 1:10 pm assessment follow up questions Carrying 303(d) and M&E listings over Robert Hillegas 1:20 pm during re-segmentation Update the 303(d) Listing Methodology Arne Sjodin 1:50 pm to remove the temperature exceedance allowance for lakes and reservoirs Skip Feeney 2:20 pm Summary and next steps 3 303(d) Listing Methodology
Follow up to lower confidence limit assessment of iron, manganese and sulfate 1. Will this assessment method impact: – Water quality standards regulation? – TMDL development? – Permit limit development? 2. Will the division reassess all segments impaired for these parameters with the new LCL methodology during the next assessment cycle? 4 303(d) Listing Methodology
Agenda Time Agenda Topic Lead Skip Feeney 1:00 pm Introductions Address lower confidence limit Skip Feeney 1:10 pm assessment follow up questions Carrying 303(d) and M&E listings over Robert Hillegas 1:20 pm during re-segmentation Update the 303(d) Listing Methodology Arne Sjodin 1:50 pm to remove the temperature exceedance allowance for lakes and reservoirs Skip Feeney 2:20 pm Summary and next steps 5 303(d) Listing Methodology
Carrying 303(d) and M&E listings over during re-segmentation Outline of discussion • Background of issue. • Examples. • Proposed language. 6 303(d) Listing Methodology
Background • In the 2018 Regulation 93 hearing, questions were raised about the division’s practice with regard to how impairment listings are retained through the various splitting processes. • The E.coli listing on Fountain Creek segment 04 highlighted this issue. 7 303(d) Listing Methodology
Approach This is new language. We will be inserting it in the Listing Methodology to describe the process the division is already performing. 8 303(d) Listing Methodology
Defining terms • Waterbody segments may be re-segmented through several applicable processes. This modification is referred to as “splitting” because changes result in at least two new segments. The original segment is referred to as the parent and the newly created segments are referred to as the children. 9 303(d) Listing Methodology
What generates a child segment? There are many reasons a parent segment could be split: • Standards setting process. • Regulation 93 process. • TMDL process. • ATTAINS reporting. 10 303(d) Listing Methodology
Resegmentation example 11 303(d) Listing Methodology
Resegmentation example 12 303(d) Listing Methodology
Resegmentation example 13 303(d) Listing Methodology
Assessment example 14 303(d) Listing Methodology
Definition of segment Segments shall generally be delineated according to the points at which the use, physical characteristics or water quality characteristics of a watercourse are determined to change significantly enough to require a change in use classifications and/or water quality standards. In many cases, such transition points can be specifically identified from available water quality data. Reg 31.6(4)(c) 15 303(d) Listing Methodology
Why don’t we instantly reassess all child segments? • Processes and timing may not align with 303(d) cycles – Standards Resegmentation. – TMDL covered streams. – EDU listed portions. – ATTAINS reporting. • Resource intensive and not practical. – Need to research where data was originally located? – What was the original Period of Record? – Are there any new data for the child segments? – Are any other factors considered in the basis for the old decision? 16 303(d) Listing Methodology
CWA de-listing options • 40 CFR 130.7(b), “good cause” for not including segments in Category 5 may be based on the following determinations: • More recent data shows attainment. • More sophisticated method demonstrates attainment. • Flaws in original data or analysis. 17 303(d) Listing Methodology
CWA de-listing options, continued • 4b plan. • Impaired segment was not required to be listed. • TMDL. • State inappropriately listed a segment within Indian country. • Other relevant information that supports the decision not to include the segment on the section 303(d) list. 18 303(d) Listing Methodology
Proposed language 303(d) Listing Methodology Section II.G Process for Applying Attainment Status During Waterbody Resegmentation and Attainment Portioning. Waterbody segments may be re-segmented through several applicable processes. This modification is referred to as “splitting” because changes result in at least two new segments. The original segment is referred to as the parent and the newly created segments are referred to as the children. When waterbody segments are split, children segments retain the attainment status of the parent segment. Newly created children segments can be assessed outside of the standard 303(d) basin assessment cycle if new evidence, supporting a change in attainment status, is provided through a formal external party request during the hearing process. Instructions for external requests and proposals are provided in the 303(d) Listing Methodology section II.C. 19 303(d) Listing Methodology
Proposed language, continued In the situation where children segments have no supporting physical, biological or chemical data, other relevant information demonstrating that the applied attainment status is not appropriate can be utilized. These cases will be considered on an individual basis. Attainment portions, often referred to Assessment Units Identifications (AUIDs), may also be “split”. When attainment portions are split, children portions retain the attainment status of the parent. This process follows the same approach as described for waterbody segment splits. In general, the attainment status of child segments or attainment portions will be reassessed, in the segment’s regularly scheduled rotating basin 303(d) Listing cycle. 20 303(d) Listing Methodology
Proposed language, continued 303(d) Listing Methodology Section IV.C Portioning of Segments Insert after final paragraph in section C. When new assessment portions are created on segments with previous impairment classifications for other parameters, the previous impairment classifications are retained on the newly created portions. This portioning process will be consistent with language included in Listing Methodology Section II.G Process for Applying Attainment Status During Waterbody Resegmentation and Attainment Portioning. 21 303(d) Listing Methodology
Agenda Time Agenda Topic Lead Skip Feeney 1:00 pm Introductions Address lower confidence limit Skip Feeney 1:10 pm assessment follow up questions Carrying 303(d) and M&E listings over Robert Hillegas 1:20 pm during re-segmentation Update the 303(d) Listing Methodology Arne Sjodin 1:50 pm to remove the temperature exceedance allowance for lakes and reservoirs Skip Feeney 2:20 pm Summary and next steps 22 303(d) Listing Methodology
Temperature assessment – Lakes and reservoirs Outline of discussion: • Regulation # 31 language that allowed temperature exceedances if adequate refuge was present. • The 2018 Listing Methodology language that addressed the Regulation # 31 allowable exceedances. • Removal of the adequate refuge provision for assessments of the temperature standard. – EPA approval letter • Proposed new language for the 2020 Listing Methodology that removes the reference to allowable exceedances when adequate refuge is present. 23 303(d) Listing Methodology
Temperature assessment – Lakes and reservoirs • From 2005 until 2016, Regulation #31 had language that allowed for an exceedance of the temperature standard in the mixed upper layer of a lake or reservoir if adequate refuge was present. 2 303(d) Listing Methodology 4
Temperature assessment – Lakes and reservoirs • Regulation #31 pre-2016 exceedance allowance: • 5(c)(iii) Lakes and Reservoirs: When a lake or reservoir is stratified, the mixed layer may exceed the criteria in Table 1 provided that an adequate refuge exists in water below the mixed layer. Adequate refuge depends on concurrent attainment of applicable dissolved oxygen standards. If the refuge is not adequate because of dissolved oxygen levels, the lake or reservoir may be included on the 303(d) List as “impaired” for dissolved oxygen rather than for temperature. 25 303(d) Listing Methodology
Temperature assessment – Lakes and reservoirs The current temperature assessment methodology for lakes and reservoirs, as found on page 35 of the 2018 303(d) Listing Methodology, reflects this language. 2. Temperature • The division examines attainment first in the upper portion, as defined above to represent the mixed layer referenced in Regulation #31 ... If the average temperature in this upper portion exceeds the chronic standard, temperatures below the upper portion are evaluated when there is need to consider adequate refuge. Adequate refuge depends on concurrent attainment within a given depth of the temperature standard and applicable dissolved oxygen standards (Regulation #31, Table 1, (footnote 5.c.iii)). 26 303(d) Listing Methodology
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