Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-33 - REGULATION NO. 33 - CLASSIFICATIONS AND NUMERIC STANDARDS FOR UPPER COLORADO RIVER BASIN AND NORTH PLATTE RIVER (PLANNING REGION 12)
Section 5 CCR 1002-33.62 - STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JUNE 10, 2019 RULEMAKING; FINAL ACTION AUGUST 12, 2019; EFFECTIVE DATE DECEMBER 31, 2019
Current through Register Vol. 47, No. 17, September 10, 2024
The provisions of C.R.S. 25-8-202(1)(a) and (b); 25-8-203; 25-8-204; and 25-8-402 C.R.S., provide the specific statutory authority for adoption of these regulatory amendments. The commission also adopted in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
A. Water Body Segmentation
Some segments were renumbered, combined, or new segments were created to facilitate appropriate organization of water bodies in this regulation. Renumbering and/or creation of new segments was made based on information that showed:
Upper Colorado segments 2, 5, and 6a: The mainstem of Willow Creek from the outlet of Willow Creek Reservoir to the confluence with the Colorado River was moved from segments 2 and 6a to a new Segment 5 to facilitate adoption of appropriate temperature standards. New Segment 5 was assigned CS-II temperature standards. Segments 2 and 6a retained CS-I temperature standards. Segment 2 is classified as Recreation E, and Segment 6a is classified as Recreation P. The more protective Recreation E standards from Segment 2 were adopted on Segment 5.
Upper Colorado segments 6b and 6c: Segments 6b and 6c were combined into Segment 6b to facilitate improved organization of the regulation and adoption of appropriate standards to protect the Aquatic Life use. Existing standards on Segment 6c were retained for the new Segment 6b.
Upper Colorado segments 7b and 7c: Tributaries to Muddy Creek from the inlet of Wolford Mountain Reservoir to the outlet of the reservoir and Blacktail Creek were moved from Segment 7c to Segment 7b to facilitate adoption of a Recreation E use classification and standards on these tributaries.
Upper Colorado segments 7b, 7d, and 7e: The mainstem of Muddy Creek from the outlet of Wolford Mountain Reservoir to above the Highway 40 Bridge in Kremmling (40.060574, -106.398739) was moved from Segment 7b to a new Segment 7d to facilitate adoption of appropriate temperature standards. The mainstem of Muddy Creek from above the Highway 40 Bridge in Kremmling (40.060574, -106.398739) to the confluence with the Colorado River was moved from Segment 7b to a new Segment 7e to facilitate adoption of appropriate temperature standards and to remove the Water Supply use. Segment 7b retained CS-I temperature standards and the Water Supply use. Segment 7d retained the Water Supply use and was assigned CS-II temperature standards. Segment 7e was assigned CS-II temperature standards with no Water Supply use.
Blue River segments 4a and 5: Soda Creek from the source to Dillon Reservoir was moved from Segment 5 to Segment 4a to facilitate improved organization of the regulation. Segment 5 was previously included as an exception to Segment 4a, but the uses and standards were the same for both segments. Segment 5 was deleted.
Roaring Fork segments 3a and 3c: Three Mile Creek, including all tributaries and wetlands, from the source to the confluence with the Roaring Fork River was moved from Segment 3c to Segment 3a to facilitate adoption of appropriate temperature standards. Segment 3c retained CS-II temperature standards. Segment 3a retained CS-I temperature standards.
Segment descriptions were also edited to improve clarity, correct typographical errors, and correct spelling errors. These changes are listed in Section M.
B. Aquatic Life Use Classifications and Standards
Some segments assigned an Aquatic Life use classification were missing a standard to protect that use. The commission adopted the missing standards for the following segments:
Upper Colorado River: 4 (sculpin qualifier), 6a (sculpin qualifier), 6b (full suite of aquatic life use standards), 7c (sculpin qualifier)
Eagle River: 11 (full suite of aquatic life use standards)
Yampa River: 4 (full suite aquatic life use standards), 11 (full suite aquatic life use standards), 12 (full suite aquatic life use standards), 19 (dissolved selenium)
The commission reviewed information regarding the existing aquatic communities. No segments were lacking an Aquatic Life use, but Class 2 segments with high MMI scores or a wide variety of fish species were upgraded from Class 2 to Class 1.
The following segments were upgraded from Cold 2 to Cold 1:
Yampa River: 11
The commission reviewed all Class 2 segments that have fish that are "of a catchable size and which are normally consumed and where there is evidence that fishing takes places on a recurring basis." Water + Fish or Fish Ingestion standards were applied to the following segments:
Eagle River: 11
C. Recreation Use Classifications and Standards
The commission reviewed information regarding the current Recreation use classifications and evidence pertaining to actual or potential primary contact recreation. In addition, newly created segments were given the same Recreation use classification as the segment from which they were split, unless there was insufficient evidence to support keeping that classification, or evidence to show that the existing use classification was inappropriate.
Based upon evidence that portions of these segments are publicly accessible and located in a developed area where there is easy access for children, it was determined that primary contact recreation is expected to occur. The following segments with a Recreation N use classification and standards were upgraded to Recreation E:
Upper Colorado River: 7a
Blue River: 7
Roaring Fork River: 3b
North Platte River: 7b
Based upon evidence that portions of these segments are publicly accessible and/or accessible to families who live in the area or visitors to public recreation lands in these segments, it was determined that primary contact recreation is expected to occur, including water play by children. The following segments with a Recreation U use classification and standards were upgraded to Recreation E:
Yampa River: 20a
During the 2008 hearing, the commission created Segment 20a and adopted a Recreation U classification after it was determined that a lack of reasonable inquiry had been completed and no use attainability analysis was completed. The segment description specified endpoints; however, the beginning of the segment was ambiguous. It has since been identified that tributaries to the Yampa River from above the confluence with the Elk River on National Forest lands were not explicitly included in any segments. The description for Segment 20a has been amended to include this omission, and the recreation use was upgraded to Recreation E to protect existing primary contact recreation on this segment.
D. Water Supply Use Classification and Standards
The commission added a Water Supply use classification and standards where the evidence demonstrated a reasonable potential for a hydrological connection between surface water and alluvial wells used for drinking water. The Water Supply use classification and standards were added to the following segments:
Yampa River: 5, 11, 13c (changed from seasonal application to year around), 13e
The commission removed the Water Supply use classification and standards where the evidence demonstrated that a Water Supply use does not currently exist due to flow or other conditions, and that such a use is not reasonably expected in the future due to water rights, source water options, or other conditions. The Water Supply standard for chloride was retained for these segments, given concerns regarding the protection of aquatic life by the existing Water Supply standards. The Water Supply use classification and standards, except for chloride, were removed from the following segments:
Upper Colorado River: 7e
For the segments where the Water Supply use classification and standards were removed, the commission retained the 250 mg/L chronic (30-day average) standards for chloride as an interim step, based on evidence presented demonstrating the toxic effects of chloride on aquatic life. Retaining the current chloride standard is necessary to protect the assigned Aquatic Life uses and to ensure that these waters are free from substances toxic to aquatic life in accordance with 31.11(1)(a)(iv). The commission retained the numeric standard for chloride because narrative standards have often proved challenging to implement, and interim numeric standards will provide implementable interim standards while allowing time for development of robust replacement criteria based on the latest scientific information.
The commission recognizes that there is scientific uncertainty about the appropriate standards for chloride and/or sulfate to protect the Aquatic Life use, and that appropriate standards may need to recognize that toxicity is affected by site water characteristics (similar to the influence of hardness on the toxicity of dissolved metals). The commission's intention is that future revisions to the numeric standards assigned to these segments, and also to Regulation No. 31 (i.e., aquatic life-based table values chloride and/or sulfate), can be considered if:
E. Agriculture Use Classification and Standards
The commission reviewed the single segment lacking an Agriculture use (COUCBL07). Based on an evaluation of the available data and information, no changes were adopted at this time.
Some segments assigned an Agriculture use classification were missing a standard to protect that use. The commission adopted the missing standards for the following segments:
Yampa River: 13g, 13h, 13i (total recoverable trivalent chromium)
F. Other Standards to Protect Agriculture, Aquatic Life, and Water Supply Uses
In the 2015 Regulation No. 38 hearing, the commission adopted a standard of 150 µg/L, based on an improved understanding of the dietary- and water-intake rates for various life-stages of cattle. This standard is protective of all life-stages of cattle (including lactating cows and growing heifers, steers and bulls) at all times of year.
The Agriculture table value assumes that the safe copper:molybdenum ratio is 4:1. Food and water intake is based on growing heifers, steers, and bulls consuming 6.7 kg/day of dry matter and 56.8 liters of water per day. Molybdenum supplementation is assumed to be zero. The table value standard (TVS), which considers total copper and molybdenum intakes, is calculated from the following equation:
The assumed values for these equations are as follows:
Cuforage = 7 mg/kg, Forageintake = 6.7 kg/day, Cuwater = 0.008 mg/L, Waterintake = 56.8 L/day, Cusupplementation = 0 mg/day, Cu:Mo Safe Ratio = 4:1, Moforage = 0.5 mg/kg.
In 2010, the commission also adopted a new standard for molybdenum to protect the Water Supply use that was calculated in accordance with Policy 96-2.
A molybdenum standard of 150 µg/L was adopted for all segments in Regulation No. 33 that have an Agriculture use classification, and where livestock or irrigated forage are present or expected to be present.
The following segments (or portions of segments) have an Agriculture use classification and a Water Supply use, but livestock watering does not occur. A molybdenum standard of 210 µg/L was retained on these segments to protect the Water Supply use:
Blue River: 14, 15
The following segment has an Agriculture use classification, but livestock watering does not occur. A numeric molybdenum standard does not apply to this segment. Instead, a narrative standard applies to protect the Water Supply use in downstream waters.
Blue River: 13
The following segment has an Agriculture use classification, but a site-specific molybdenum standard has been previously adopted. The site-specific molybdenum standard of 190 µg/L was retained on this segment to protect the Agriculture use:
Upper Colorado River: 8
Acute = e(0.9789*ln(hardness) - 3.866)* (1.136672-(ln(hardness)*0.041838))
Chronic = e(0.7977*ln(hardness) - 3.909)*(1.101672-(ln(hardness)*0.041838))
EPA's updated cadmium criteria are less stringent than Colorado's current cadmium standards when water hardness is greater than 45 mg/L CaCO3. Although the criteria are less stringent, they were developed using the latest science and are protective of aquatic life, and it is expected that Colorado's state-wide cadmium standards will likely be updated using the 2016 EPA cadmium criteria at a later date. Therefore, the commission determined it was appropriate to adopt the new criteria for waters known to be impaired for cadmium to ensure forthcoming clean-up goal development and Total Maximum Daily Load (TMDL) evaluations are based on the most relevant water quality standards available. The updated cadmium standards were adopted for the following segments:
Blue River: 2c, 4a, 6a, 7, 12
Eagle River: 2, 5a (acute), 5c (acute), 6
The cadmium Water Supply standard was added because the acute Aquatic Life standard is not protective when the hardness was greater than 200 mg/L in non-trout streams and 345 mg/L in trout streams; the lead Water Supply standard was added because the acute Aquatic Life standard is not protective when hardness is greater than 79 mg/L; and the nickel Water Supply standard was added because the chronic Aquatic Life standard is not protective when hardness is greater than 216 mg/L. Cadmium, lead, and nickel Water Supply standards were added to the following segments:
Upper Colorado River: 1, 2, 3, 4, 5, 6a, 7a, 7b, 7c, 7d, 8, 9, 10a, 10b, 10c, 11, 12, 13
Blue River: 1, 2a, 2b, 2c, 4a, 4b, 6a, 6b, 8, 9, 10, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23
Eagle River: 1, 2, 3, 4, 5a, 5b, 5c, 6, 7a, 7b, 8, 9a, 9b, 9c, 10a, 10b, 12, 13, 14
Roaring Fork River: 1, 2, 3a, 3b, 3c, 3d, 4, 5, 6, 7, 8, 9, 10a, 10b, 11, 12
North Platte River: 1, 2, 3, 4a, 4b, 5a, 5b, 6, 8, 9
Yampa River: 1, 2a, 2b, 3, 4, 5, 6, 7, 8, 11, 13a, 13c, 13e, 13f, 14, 15, 18, 19, 20a, 20b, 21, 22, 23
G. Antidegradation Designations
The commission reviewed all segments designated Use Protected to determine if the Use Protected designation was still warranted. Based upon available water quality data that meet the criteria of 31.8(2)b, the Use Protected designation was not removed from any segments.
The commission reviewed all Reviewable segments to determine if this Antidegradation designation was still warranted. Based upon available water quality data that fails to meet the criteria of 31.8(2)b, the Reviewable designation was not removed from any segments.
H. Ambient Quality-Based and Site-Specific Criteria-Based Standards
Ambient quality-based standards are adopted where a comprehensive analysis has been conducted demonstrating that elevated existing water quality levels are the result of natural conditions or are infeasible to reverse, but are adequate to protect the highest attainable use. All existing ambient-based standards were reviewed and no revisions were made.
Ambient-based standards were deleted from the following segment:
Blue River Segment 11 (COUCBL11):
The commission replaced the "existing quality" standards on French Gulch for acute and chronic lead with table value standards (TVS). Recent water quality data show that lead concentrations are achieving TVS in French Gulch. The commission recognizes that the 2016 accute and chronic cadmium criteria and zinc TVS are not currently attainable. The commission anticipates the necessary information will be collected to support the adoption of site-specific standards for cadmium and zinc in the next Upper Colorado basin hearing in 2024 or sooner if possible.
The 2016 revisions to Regulation No. 31.7 provide that where sources and causes of elevated pollutant levels are determined to be attributable to anthropogenic activity, a comprehensive alternatives analysis must be conducted to identify the extent to which conditions could be improved by implementing feasible pollution controls. Substantial anthropogenic impacts have been identified and studied in French Gulch. In partnership with EPA, Summit County and the Town of Breckenridge have made substantial investments in water quality studies and treatment efforts in Blue River Segment 11. Numerous non-point source clean-up projects have been completed, and in 2008 the Wellington Oro (W-O) wastewater treatment plant began operating. While a great deal of information and data were shared in this hearing, more recent information to characterize the effects of these changes is not currently available. The division will work with interested parties to complete a use attainability analysis for Segment 11, including a comprehensive alternatives analysis that meets the requirements in 31.7(1)(b)(ii), prior to the 2024 rulemaking hearing.
In 2003, in addition to the "existing quality" standards adopted on Segment 11, site-specific numeric standards were adopted downstream on Blue River segments 2a and 2b. The 4 µg/L acute and chronic cadmium standards on Segment 2a were described as a "CERCLA treatment target concentration" (NWCCOG Rebuttal Statement). By contrast, the zinc standards on Segment 2a and cadmium and zinc standards on Segment 2b were adopted to protect various life stages of brown trout. No changes were proposed or adopted for Blue River segments 2a and 2b in this rulemaking hearing. However, because the W-O treatment facility has been operating for a decade, additional cadmium and zinc toxicity data have become available, and habitat improvements have been made in segments 2a and 2b, there is a need to review the cadmium and zinc standards as part of a use attainability analysis. The commission intends that the division and interested parties will work to identify appropriate cadmium and zinc standards to protect the highest attainable use on Blue River segments 2a and 2b as part of the effort to develop site-specific standards on Segment 11.
Treatment targets in the discharge control mechanism for the W-O facility were developed based on water quality standards in Blue River Segment 2a. The commission considered replacing the "existing quality" narrative standards for cadmium and zinc on Segment 11 with the EPA 2016 cadmium criteria and TVS, respectively, as recommended by the division but determined that it was best to retain the narrative standards until enough information is available to develop site specific standards in 2024. EPA's Superfund and Emergency Management Division will continue to monitor water quality in French Gulch and the Blue River to assess the performance of the WO treatment facility and to assess whether there are other viable alternatives to improve water quality in French Gulch and the Blue River. In addition, EPA's Superfund and Emergency Management Division will continue to work cooperatively with interested parties to help derive appropriate cadmium and zinc standards to be proposed during the next basin rulemaking hearing.
The commission intends that the division will work with interested parties, which include EPA, CPW, and local governments, to leverage existing studies and ongoing data collection efforts to develop site-specific standards on Blue River segments 2a, 2b and 11 prior to the next basin review.
The commission reviewed all other existing site-specific standards. Based on an evaluation of the available data and information, no additional changes were adopted at this time.
I. Temporary Modifications
All existing temporary modifications were examined to determine if they should be allowed to expire or if they should be extended, either unchanged or with changes to the numeric limits.
The commission deleted temporary modifications on the following segments:
Blue River: 12
Eagle River: 1, 4
Roaring Fork River: 1
Yampa River: 1
To remain consistent with the commission's decisions regarding arsenic in section 33.50 , all existing temporary modifications for arsenic of "As(ch)=hybrid" (expiration date of 12/31/21) were retained. In addition, for the following segments, an arsenic temporary modification was adopted for the 0.02 µg/L Water + Fish numeric standard in recognition of the uncertainty regarding "the water quality standard necessary to protect current and/or future uses" (31.7(3)). For arsenic, a known human carcinogen, the uncertainty is multi-faceted. For example, there are unresolved questions about existing water quality conditions (including spatial and temporal variation), the sources and causes of any numeric standard exceedances, and to what extent existing conditions may be a result of natural or irreversible sources. Likewise, with reference to the equations used to calculate the Water + Fish, Water Supply, and Fish Ingestion table value standards for arsenic (Policy 96-2), there are unresolved questions about the cancer slope, the bioconcentration or bioaccumulation factor, and the percentage of total arsenic in fish tissue that is inorganic. The commission recognizes the need to resolve the uncertainty in the arsenic standards and ensure that human health is adequately protected. Temporary modifications for arsenic were added to the following segments:
Yampa River: 5, 11, 13c (year-round application)
The commission adopted temporary modifications on the following segments:
Yampa River Segment 2b (COUCYA02b): Temporary modification of the chronic temperature standards.
The commission adopted a temporary modification of the chronic temperature standards on Segment 2b during July, August, September and November with an expiration date of December 31, 2024 and a narrative operative value of "current conditions". Steamboat presented information that shows instream non-attainment and a predicted compliance problem with the chronic water quality based effluent limit (WQBEL) for its WWTF during those months. The commission found that there is uncertainty about the extent to which the existing quality is the result of natural or irreversible human-induced conditions.
The adoption of this temporary modification is based on a predicted compliance problem in the next permit renewal, after January 2022. The commission would not typically adopt a temporary modification this far in advance of a predicted compliance problem, but is making an exception in this instance based on the work that Steamboat is already doing to characterize thermal drivers in the Yampa River and implement strategies to reduce stream temperatures. Steamboat's plan to resolve uncertainty includes an alternatives analysis for wastewater cooling technology at the city's WWTF, with an update to be presented to the commission at the December 2020 temporary modifications hearing. This information will inform whether a temporary modification continues to be justified or whether another regulatory tool such as a compliance schedule would be appropriate.
The operative value of the temporary modification is the narrative "current conditions." In future reviews, the commission will consider the need for changes to all elements of the temporary modification, including the operative value. Because the division is now working to develop methods to support derivation of numeric operative values and effluent limits, the commission anticipates that numeric operative values are likely to be adopted in the future as more data are available to characterize spatial and temporal variability in effluent and instream temperature conditions.
J. Temperature Standards
The commission revised temperature criteria in Regulation No. 31 in 2007, and again in 2010, based on the development of the Colorado Temperature Database and a lengthy stakeholder process. In 2014, the new temperature standards were adopted for all segments with an Aquatic Life use classification in Regulation No. 33. In June 2016, temperature criteria in Regulation No. 31 were further revised, including changes to the temperature table value standards, revision of warm water winter acute standards, and the addition of footnotes to protect lake trout and mountain whitefish.
While early life stages of mountain whitefish are known to be the most thermally-sensitive, the time period these early life stages occur can vary from site to site. Mountain whitefish spawn in the fall, but timing of spawning, incubation, and emergence all depend on a variety of site-specific factors, including water temperature. The incubation period takes longer when water is colder, and that will delay hatching, emergence, and migration of fry. Depending on when spawning occurs and the water temperature in which the eggs are spawned and incubated, the incubation period could last through late spring.
Based on information provided by Colorado Parks and Wildlife (CPW), thermally-sensitive early life stages of mountain whitefish occur in certain water bodies in Regulation No. 33. Spawning begins in October and the fry life stage is complete by May in these water bodies. Therefore, only limited application of the mountain whitefish summer temperature standards to protect eggs, larvae, and fry is necessary.
In segments currently assigned CS-I temperature standards, the application of the mountain whitefish summer temperature standards is not necessary. The winter season included in CS-I temperature standards (i.e., October to May) is expected to cover the period when mountain whitefish early life stages are expected to occur (i.e., October to May). In addition, the CS-I winter standards are more stringent than the mountain whitefish summer standards. Therefore, because the CS-I temperature standards are protective of mountain whitefish early life stages, the commission did not adopt the mountain whitefish summer standards on segments with CS-I temperature standards in Regulation No. 33. While the commission made no changes to the temperature standards, mountain whitefish spawning and early life stages are known to occur in the following CS-I segments:
Upper Colorado River: 4 (Grizzly Creek and No Name Creek), 7b (Piney River)
Eagle River: 9a (Eagle River from Gore Creek to Squaw Creek)
Roaring Fork River: 3a (Roaring Fork River from Snowmass Creek to the Fryingpan River Threemile Creek, Fourmile Creek), 6 (Fryingpan River), 8 (Crystal River)
Yampa River: 2a (Yampa River from Stagecoach Reservoir to Oak Creek), 3 (Upper Bear River), 8 (Elk River), 20a (Mad Creek and tributaries to the Elk River)
The commission adopted standards to protect mountain whitefish on a season- and site-specific basis where information provided by CPW biologists indicated that thermally-sensitive early life stages of mountain whitefish are known to occur. CS-II summer temperature standards typically apply from April to October. Because mountain whitefish spawning and early life stages are expected to occur from October to May, the mountain whitefish summer temperature standards were applied for the months of April, May, and October. The CS-II table value standards were retained for the remainder of the summer (i.e., June through September). Standards to protect mountain whitefish were not adopted where a site-specific temperature standard was in place. Temperature standards to protect mountain whitefish were applied to the following CS-II segments for the months of April, May, and October:
Upper Colorado River: 3, 7a
Roaring Fork River: 3c
Yampa River: 2b, 13b, 13f
In this hearing, the commission adopted standards to protect lake trout on a site-specific basis where information provided by CPW indicated that this species occurs and protection from thermal impacts is appropriate. Adoption of lake trout standards are dependent on two factors: the existing temperature tier (cold lake or cold large lake) and whether a site-specific temperature standard was already in place. For cold lakes, only the chronic lake trout standard was adopted, as the acute cold lake temperature standard (21.2°C) is more protective than the acute lake trout standard (22.4°C). The chronic lake trout standard (16.6°C) is more protective than the chronic cold lake temperature standard (17.0°C). For cold large lakes, both acute and chronic lake trout standards were adopted unless there was a site-specific standard in place. Acute and chronic lake trout standards (22.4 and 16.6°C, respectively) are more protective than acute and chronic cold large lake standards (24.2 and 18.3°C, respectively). Lake trout standards were not proposed where an existing site-specific standard is applied.
Temperature standards to protect lake trout were applied to the following segments:
Upper Colorado River: 11 (Rim Lake MWAT), 12 (Grand Lake DM and MWAT;
Lake Granby DM), 13 (Deep Lake MWAT; Williams Fork Reservoir DM)
Blue River: 23 (DM and MWAT on Green Mountain Reservoir)
Roaring Fork River: 11 (Savage Lake and Ivanhoe Lake MWAT, 12 (Ruedi Reservoir DM)
North Platte River: 8 (Blue Lake, Lower Big Twin Lake, and Katherine Lake MWAT), 9 (Upper Big Creek Lake and Lower Big Creek Lake DM and MWAT; Agua Fria Lake MWAT)
In the 2016 Regulation No. 31 hearing, the commission declined to adopt the division's proposal for statewide solutions for temperature transition zones and shoulder seasons, in favor of a basin-by-basin consideration of temperature standards on a site-specific basis. The basin-by-basin approach was selected as it allows for consideration of temperature attainability and ambient quality-based site-specific temperature standards issues in the context of multiple lines of evidence and site-specific contravening evidence. The sections below describe the considerations and methods used to develop and support the site-specific temperature standards revisions adopted in this basin hearing.
Temperature standards have been implemented and reviewed in Regulation No. 33 during three triennial reviews - 2008, 2014, 2018. The level of emphasis and effort dedicated to understanding the aquatic community and temperature standards implementation during these reviews has resulted in a great deal of progress and application of appropriate temperature standards across the basin. Accordingly, fewer site-specific temperature standards and/or corresponding Aquatic Life use revisions were necessary compared to previous basin reviews.
Based upon information regarding the species expected to occur, temperature data, physical habitat, land cover/use, groundwater inputs, flow conditions, and all other available information regarding thermal drivers, the commission adopted revisions of temperature standards for the segments listed below where water quality is not feasible to improve or where the thermal regime is the result of natural conditions, but is sufficient to protect the highest attainable use.
The following segments were changed from CS-II to CS-I:
Roaring Fork: 3a (Threemile Creek)
The following segments were changed from CS-I to CS-II:
Upper Colorado River: 5, 7d, 7e
Moving forward with this site-specific approach, the commission encourages the division to consider whether any additional information would be appropriate to be included in the use attainability analyses.
K. Standards Corrections and Clarifications
L. Correction of Typographical and Other Errors and Segmentation Clarification
The following edits were made to segment descriptions to improve clarity and correct typographical errors:
* The formatting of the tables in Appendix 33-1 was modified to include only parameters that have been adopted in a majority of segments. The tables include rows for physical and biological, inorganic and metals for all parameters which the commission commonly adopts into segments. In segments where there is no numeric standard for a commonly adopted parameter, a blank row for that parameter is included to show the commission's site-specific decision not to adopt a numeric standard for that parameter. The commission removed beryllium and aluminum from all segments where no standard has been adopted because these parameters have only been adopted on a site-specific basis, rather than basin-wide.
* An acronym list was added to the front of Appendix 33-1 to improve the clarity and usability of the tables.
* The order of segments presented in 33.6(4) was changed to align with the order of segments in Appendix 33-1.
* Information was added at 33.6(5) specifying that the ammonia, nitrate, and nitrate standards are to be reported as nitrogen. This is consistent with the description of the standards as they are included in Table II of Regulation No. 31.
* The segment descriptions in Appendix 33-1 were reviewed, and minor revisions were made to several segments to correct grammar, punctuation, and typos. The purpose of these changes was to improve clarity and consistency of the segment descriptions.
* Revisions were made to the sentence structure of these segments. The purpose of these changes was to improve clarity and consistency of the segment descriptions.
Upper Colorado River: 7c
North Platte River: 4b
* Coordinates were added to the segment descriptions to facilitate location of segment boundaries.
Upper Colorado River: 6b, 10a, 10b, 10c
Blue River: 2a, 2b, 10, 11, 13
Eagle River: 2, 3, 5a, 5b, 6, 7a, 7b
Roaring Fork River: 3b
North Platte River: 4b
Yampa River: 6, 7, 11, 13g, 14, 15, 20b
* Upper Colorado River Segment 1: The segment description was amended for clarity and consistency.
* Upper Colorado River Segment 2: An exception for Segment 5 was added to reflect a new segment.
* Upper Colorado River Segment 4: The exception for Segment 1 was removed for clarity.
* Upper Colorado River Segment 6a: The segment description was amended for clarity.
* Upper Colorado River Segment 7a: Exceptions for segments 7d and 7e were added to reflect new segments.
* Upper Colorado Segment 10a: An exception for Segment 2 was added to correct a previous omission.
* Upper Colorado segments 10b and 10c: The segment description was amended to match the diversion records in Division of Water Resources.
* Upper Colorado Segment 11: The segment description was amended for clarity.
* Upper Colorado Segment 13: The segment description was amended for clarity.
* Blue River segments 2a and 2b: The reference to Summit County Road 3 was removed and replaced with Coyne Valley Road to improve clarity.
* Blue River Segment 4a: Wetlands were added to the segment description to correct a previous omission. Exceptions for Segments 2c, 6a, and 16 were added, and the exception for Segment 5 was removed.
* Blue River Segment 12: The arsenic standard was corrected from 0.02 µg/l to 0.02-10 µg/l to reflect the existing uses.
* Blue River Segment 21: The segment description was amended for clarity and consistency.
* Eagle River Segment 3: An exception for Segment 4 was added to correct a previous omission.
* Eagle River segments 7a and 7b: Minturn Middle School was replaced with Minturn Water Facility in the segment description to reflect a current landmark. The middle school is no longer in operation. The exception for Segment 1 was removed to correct a previous error.
* Eagle River segments 8, 9a and 9b: Dates for temperature table value standards were added to clarify the temperature standards that are effective outside of seasonal site-specific standards. A note was added to the daily maximum on 9b to clarify seasonal standards are effective.
* Eagle River Segment 12: An exception for Segment 1 was added for clarity.
* Eagle River Segment 13: The segment description was amended for clarity.
* Roaring Fork River Segment 3a: The exception for Segment 3c was removed to reflect Threemile Creek is now included in Segment 3a, and the exception for Segment 10 was changed to 10b to reflect current segmentation.
* Roaring Fork River Segment 5: An exception for Segment 1 was added to correct a previous omission.
* Roaring Fork River Segment 7: The segment description was amended for clarity.
* Roaring Fork River Segment 8: Exceptions for Segments 10a and 10b were added to reflect current segmentation.
* Roaring Fork River Segment 11: The segment description was amended for clarity.
* North Platte River Segment 4a: The source of the segment was added for clarity, and exceptions for Segments 5a and 5b were added to correct previous omissions.
* North Platte River Segment 7a: The reference to the outlet of Spring Creek Reservoir was removed to reflect current segmentation.
* North Platte River Segment 8: The segment description was amended for clarity.
* North Platte River Segment 9: The site-specific MWAT standard for Lake John was corrected to from 1.2 to 21.2 to reflect the standard adopted by the commission in 2014.
* Yampa River Segment 2a: The segment description was amended for clarity. The mainstem of the Yampa River begins at the confluence of the Bear River and Phillips Creek.
* Yampa River Segment 3: An exception was added for Segment 1, and exceptions for segments 8, 13a-f and 19 were removed to reflect current segmentation.
* Yampa River Segment 4: The nutrient note was added to correct a previous omission.
* Yampa River Segment 5: The segment description was amended to improve clarity. Chimney Creek becomes Phillips Creek prior to reaching the Yampa River.
* Yampa River Segment 8: The segment description was amended for clarity. The West Fork Elk River originates at the Elk River and confluences with the Yampa River. Previously it was unclear if the West Fork was included with the Elk River in Segment 8. The exception for 20b was removed to reflect current segmentation.
* Yampa River Segment 12: An exception was added for Segment 8 and 20a to improve clarity and consistency.
* Yampa River Segment 13a: The segment description was amended to improve clarity and consistency with Segments 13b and 13c. Over time tributaries to Trout Creek have been moved to other segments, and it was unclear which tributaries to Trout Creek were included in 13a.
* Yampa River Segment 13b: The segment description was amended for clarity. Wetlands were added to Fish Creek and Middle Creek to correct a previous omission. The erroneous trout standards were removed. The assessment location and temporary modification language was amended for clarity.
* Yampa River 13c: The segment description was amended for clarity and consistency with 13a and 13b. The boundary for tributaries to Trout Creek was moved from County Road 179 approximately 1500 feet downstream to the confluence with Fish Creek to improve clarity.
* Yampa River Segment 13d: The assessment location language was amended for clarity.
* Yampa River Segment 13e: The assessment location language was amended for clarity.
* Yampa River Segment 13g: The segment description was amended for clarity. Cow Camp Creek is an informal name not included on maps. The erroneous trout standards were removed.
* Yampa River Segment 13h: The spaces for total cadmium and total silver were removed from the table to correct a formatting error. Acute cadmium and chronic silver were added to replace the missing standards to protect Aquatic Life use.
* Yampa River Segment 13i: The temporary modification language was modified for clarity. The assessment location was removed to reflect assessment locations adopted by the commission in 33.6(4).
* Yampa River Segment 13j: The seasonal qualifier for selenium was removed to reflect selenium standards as adopted by the commission.
* Yampa River Segment 14: The segment description was amended for clarity.
* Yampa River Segment 15: The segment description was amended for clarity. Dry Fork Elkhead Creek confluences with Elkhead Creek prior to the Yampa River. The erroneous trout standards were removed.
* Yampa River Segment 18: The segment description was amended for clarity. The mainstem of the Little Snake River is also within the Lower Colorado River basin. The new description clarifies that tributaries within Segment 18 are within the Upper Colorado River basin.
* Yampa River Segment 20a: This segment description was amended to clarify the beginning of the segment is upstream of the confluence with the Elk River. Previously, tributaries to the Yampa River from above the confluence with the Elk River on National Forest land were not explicitly included in any segment, and 20a was inconsistently applied to National Forest lands.
* Yampa River Segment 23: The erroneous trout standards were deleted.
