5 Colo. Code Regs. § 1002-37.40
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
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:
Lower Yampa segments 3a and 3b: The mainstems of Jeffway Gulch and Deacon Gulch were moved from Segment 3a to Segment 3b to facilitate application of the appropriate use classifications. A Water Supply use. Water + Fish qualifier, and standards to protect those uses were added to Segment 3a. Segment 3b does not have a Water Supply use or Water + Fish qualifier.
Lower Yampa segments 3q and 31: The mainstem of Little Collom Gulch was moved from Segment 3g to new Segment 3j to facilitate adoption of appropriate standards on these segments if necessary. A site-specific iron standard was adopted for a portion of Segment 3g.
Lower Colorado segments 7a and 9d: The lower portion of Battlement Creek was moved from Segment 7a to new Segment 9d to facilitate improved organization of the regulation. Uses and standards from Segment 7a were retained.
Lower Colorado segments 11a, 11b, 11c, 11d, 11e, 11f, 11 q and 12a: Segments 11a, 11b, 11c, 11d, 11e, 11f and 12a were combined in their entirety into Segment 11a, and a portion of Segment 11g was added to Segment 11a to facilitate appropriate adoption of appropriate use classifications and standards and organization of the regulation. The use classifications for this new Segment 11a are Agriculture, Aquatic Life Cold 1, Recreation P and Water Supply.
Lower Colorado Segment 11q: Segment 11 g was renumbered to Segment 11 b. Additionally, the original segment was divided into three segments to facilitate improved geographic organization of the regulation and adoption of appropriate standards. Tributaries to East Fork Parachute Creek were included in new Segment 11a. Tributaries to the Colorado included in the description were moved to new Segment 12a. Tributaries to the east side of Parachute Creek were retained in Segment 11 b with no changes to the use classifications.
Lower Colorado Segment 11 h: Segment 11 h was moved to previously deleted segment 11c to improve clarity of the regulation. The segment description was also reworded for clarity, but content was not altered.
Lower Colorado segments 5, 12b and 12c: Wallace Creek was moved from Segments 5 and 12b to new Segment 12c to improve clarity and facilitate adoption of the appropriate Aquatic Life use classification and standards. Segment 5 retained an Aquatic Life Cold 1 use with CS-I temperature standards, and Segment 12b retained an Aquatic Life Cold 2 use with CS-II temperature standards. New Segment 12c was assigned an Aquatic Life Cold 1 use with CS-I temperature standards.
Lower Colorado Segment 13d: Coal Canyon Creek downgradient of the Government Highline Canal was moved from Segment 13d to Segment 13a to facilitate adoption of appropriate standards to protect the Aquatic Life use. Segment 13d was deleted.
Segment descriptions were also edited to improve clarity, correct typographical errors, and correct spelling errors. These changes are listed in Section M.
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:
Lower Yampa/Green River: 3a (full suite of aquatic life use standards), 3b (acute chlorine, nitrite), 3f (full suite of aquatic life use standards), 3g (full suite of aquatic life use standards), 31 (acute chlorine, nitrite), 17b (full suite of aquatic life use standards), 17c (nitrite), 20 (full suite of aquatic life use standards), 22d (full suite of aquatic life use standards)
White River: 13a (full suite of aquatic life use standards), 13c (nitrite), 13d (nitrite), 22 (full suite of aquatic life use standards)
Lower Colorado River: lib (full suite of aquatic life use standards), 13a (acute and chronic chlorine, nitrite), 15d (cadmium and silver trout qualifiers)
The commission reviewed information regarding the existing aquatic communities. Where the existing aquatic communities are not aligned with the Aquatic Life use, the following segments were upgraded from Cold 2 to Cold 1:
Lower Colorado River: 12c
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:
Lower Yampa/Green River: 3a, 16
White River: 9d, 13c, 15
Lower Colorado River: 13b
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 P use classification and standards were upgraded to Recreation E:
Lower Colorado River: 14b, 14c
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 seasonal Recreation N use classification and standards were upgraded to Recreation E:
White River: 9c, 9d
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 there is the potential for primary contact recreation, including water play by children. However, at this time, existing primary contact uses were not identified. Therefore, the following segments with a Recreation N use classification and standards were upgraded to Recreation P:
Lower Yampa/Green River: 3a, 3d, 3h, 17b, 17c, 21, 22a, 22b
White River: 9a, 9b, 13a, 16a, 16b, 18a
Lower Colorado River: 4d, 11a
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:
Lower Yampa/Green River: 3a
Lower Colorado River: 9a, 13a
The commission reviewed the single segment lacking an Agriculture use. 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:
Lower Yampa/Green River: 3b (boron), 31 (boron)
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. 37 that have an Agriculture use classification, and where livestock or irrigated forage are present or expected to be present.
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))
EPAs updated cadmium criteria are less stringent than Colorado's current cadmium standards when water hardness is greater than 45 mg/L CaC03. 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:
Lower Colorado River: 4e (chronic)
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:
Lower Yampa/Green River: 2, 3c, 3e, 3h, 4, 5, 6, 8, 9,10,12a, 12c, 13a, 13b, 15, 16, 18, 19a, 19b, 21, 25, 27, 28, 29, 31, 33
White River: 1, 3, 4a, 4b, 6, 7, 8, 9a, 9b, 9c, 9d, 10a, 10b, 11, 12, 13b, 14a, 16a, 18b, 20, 21,23,24,25,26
Lower Colorado River: 1,2a, 2b, 4a, 4c, 4d, 5, 6, 7a, 7b, 8, 9b, 9c, 10, 11a, 11c, 12b, 13f, 14a, 14b, 14c, 15a, 15b, 15c, 15d, 16, 17a, 17b, 18, 19, 20, 21
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 segments designated Reviewable to determine if the Reviewable 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.
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.
Ambient-based standards were adopted on the following segment:
Lower Yampa/Green River: 3g (iron)
All existing site-specific standards were reviewed, and where appropriate were revised or deleted. Site-specific standards were deleted from the following segments:
Lower Yampa/Green River: 3b (boron), 31 (boron)
All existing temporary modifications were examined to determine if they should be allowed to expire or deleted, or if they should be extended, either unchanged or with changes to the numeric limits.
The commission deleted temporary modifications on the following segments:
Lower Yampa/Green River: 12b (arsenic)
The commission extended temporary modifications on the following segments:
Lower Colorado River: 4e (acute and chronic copper)
To remain consistent with the commission's decisions regarding arsenic in section 37.31 , 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:
Lower Yampa/Green River: 3a, 16
White River: 9d
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. 37. 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. 37. 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. 37. 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:
White River: 3, 6
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:
Lower Colorado River: 1 (Colorado River from the confluence with the Roaring Fork River to Elk Creek)
In Regulation No. 37, there are no known water bodies where lake trout are expected to occur, based upon information provided by CPW. No changes were adopted at this time to protect lake trout.
Regulation No. 31 in 2007, the division and others have worked to ensure that appropriate temperature standards were adopted for segments throughout the state. At times, this effort to assign temperature standards has also included reevaluation of the existing Aquatic Life use classifications, and use revisions have been proposed and adopted where appropriate. Incremental progress continues as temperature standards are refined based on the experience and data gains that have occurred since initial adoption of temperature standards.
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. 37 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:
Lower Colorado River: 12c
Moving forward with this site-specific approacin, the commission encourages the division to consider winetlner any additional information would be appropriate to be included in the use attainability analyses.
Lower Yampa segments 3q and 31 (COLCLYOSq and COLCLYOSi): For Segment 3g, the commission adopted table value standards to protect the Aquatic Life use, based on evidence submitted by the division and Tri-State Generation & Transmission Association, Inc. (Tri-State) that there are aquatic life habitat, the presence of macroinvertebrates, and at least occasional flow in this segment. The commission also adopted a site-specific ambient-based iron standard of 1,500 µg/L on Collom Gulch from its source to the diversion structure at 40.333977, 107.860833, which applies during the runoff season, from March to May, with one assessment location (at County Road 32; 40.323530, -107.877200). The table value standard of 1,000 µg/L applies during the non-runoff season (June to February). The TVS applies year-round to all other waters in Segment 3g, with the exception of Little Collom Gulch, which was moved to new Segment 3j.
Tri-State submitted sufficient data and justification to adequately characterize the highest attainable use in Collom Gulch and supported adoption of a site-specific ambient-based total recoverable iron standard for a portion of Segment 3g, Collom Gulch from its source to the diversion structure at 40.333977, 107.860833, to apply from March to May. Although there was one sample demonstrating an exceedance of the standard in June, generally the lack of data precluded extending the ambient standard through June. Additional sampling at the Upper Collom Gulch site located upstream of all mine disturbance may support future adjustment to the applicable season for the ambient standard. The water quality data demonstrated that natural sources within the Collom Gulch drainage are solely driving elevated instream concentrations of total recoverable iron during the spring runoff season.
The division proposed that the commission create a new segment for Little Collom Gulch (Segment 3j), separating it from Collom Gulch, and adopt the full suite of Aquatic Life standards for Little Collom Gulch. Tri-State also proposed that the site-specific iron standard apply to Little Collom Gulch, but a lack of flow during all sampling events (since 2011) in this tributary precluded the collection of data to derive an ambient-based standard. Tri-State presented evidence it has made numerous attempts to collect water quality data in Little Collom Gulch since 2011 but never found flow to sample and that a 2018 survey found no aquatic habitat or aquatic macroinvertebrates in Little Collom Gulch. Due to the lack of observed flow in Little Collom Gulch, there is uncertainty regarding what water quality standards should apply. The commission, however, recognized that Tri-State's new stormwater ponds, which began discharging in April 2019, may affect the hydrology and aquatic life of Little Collom Gulch in the future. Tri-State is required to report flow from the ponds under its permit, and Tri-State committed to developing more information about the ponds and their impacts on Little Collom Gulch for the next triennial review hearing.
For new Segment 3j, the commission determined that there was currently insufficient information and data regarding Little Collom Gulch to apply the full suite of Aquatic Life standards to the segment, and therefore, the commission chose to make no change and retain the Agriculture standards that currently apply for the waters in the new segment. It is the commission's expectation that Tri-State will provide additional information regarding flow from the stormwater ponds at the next triennial review hearing and develop further information regarding how the ponds affect the hydrology and aquatic life of Little Collom Gulch for the commission to consider at the next rulemaking hearing.
Lower Colorado River Segment 4e (COLCLC04e): The commission considered the copper standards for Lower Colorado Segment 4e (Dry Creek). In this hearing, Tri-State initially proposed replacing the temporary modification with site-specific standards. Tri-State submitted evidence that it has been collecting data to determine whether copper standards may be based on the Fixed Monitoring Benchmark (FMB) application of the Biotic Ligand Model (BLM). The division recommends that a minimum of 24 samples be collected over a two-year period in order to fully capture seasonality before development of any BLM-based site-specific standard. In addition, the division recommends the use of field pH measurements, rather than pH measurements in the laboratory, to most closely match field conditions for use in the BLM model. Because the evidence submitted by Tri-State did not contain sufficient reliable field pH measurements, Tri-State withdrew its site-specific standards proposal and proposed an extension of the temporary modification.
The temporary modification for copper was first adopted by the commission in 2008. The maximum effluent potentially dissolved copper concentration for the Tri-State Rifle Station before 2008 was 1,380 µg/L. During the temporary modification term, the maximum effluent potentially dissolved copper concentration was 277 µg/L. The commission determined that effluent quality has been as good as, or better than, the "current condition" while the temporary modification has been in place.
The temporary modification for copper was set to expire December 31, 2019. Because water quality data collection for development of BLM-based standards has been ongoing since 2015, it was expected that this duration would be sufficient. However, because Tri-State Rifle Station's discharge is intermittent and Dry Creek and its tributaries are ephemeral, flowing only in response to precipitation or discharge events, it has been challenging to develop a database containing a sufficient number of samples. In addition, due to documented pH inconsistencies and probe calibration errors, insufficient field pH data were available to use for the BLM at the time of this hearing. Therefore, the commission determined that additional time was necessary to collect additional water quality data, and extended the temporary modification to June 30, 2021. Through continued data collection, it will be possible to correlate field and laboratory pH values and/or develop a field pH database of sufficient size to derive BLM-based standards. It is anticipated that Tri-State will propose site-specific copper standards for consideration at the December 2020 temporary modifications review hearing.
The operative value of the temporary modification is the narrative "current conditions." In future reviews of this temporary modification, the commission will use the following values from the most recent 5 years of data to determine if effluent and waterbody quality is maintained and ensure that the existing uses are protected: the maximum 30-day average (277 µg/L, 11/2015-4/2019) potentially dissolved copper effluent concentration and the 85th (117 µg/L, 11/2015-4/2019) and 95th (143 µg/L, 11/2015-4/2019) percentile dissolved copper instream concentrations at site DC-1.
The following edits were made to segment descriptions to improve clarity and correct typographical errors:
* The formatting of the tables in Appendix 37-1 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 37-1 to improve the clarity and usability of the tables.
* Information was added at 37.6(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 37-1 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.
Lower Yampa/Green River: 3a, 3c, 6, 9, 12a, 17a, 17b, 20, 22b, 23, 25, 26, 29, 32
White River: 4a, 6, 9a, 9b, 10a, 13a, 15, 20, 27
Lower Colorado River: 4a, 5, 9b, 12b, 13a, 14a, 16, 17a, 17b, 19
* Coordinates were added to several segment descriptions to facilitate location of segment boundaries.
White River: 13d
Lower Colorado River: 4b, 17a, 17b
* Lower Yampa/Green River Segment 3b: The effective date (12/31/2019) for the table value standards for several parameters was deleted from the 'Other' column. The standards will be effective on the effective date of this regulation.
* Lower Yampa/Green River Segment 12b: The arsenic standard was corrected from 0.02 µg/L to 7.6 µg/L to reflect the lacl< of a Water Supply use on this segment.
* Lower Yampa/Green River Segment 13a: The segment description was modified to reflect hydrology. The modification did not change the segment boundary.
* Lower Yampa/Green River Segment 13b: The segment description was modified to reflect hydrology. The modification did not change the segment boundary.
* Lower Yampa/Green River Segment 22d: The mercury standard was corrected from 2.0(T)to0.01(T).
* Lower Yampa/Green River Segment 28: The extra decimal point in the mercury standard was deleted to provide clarity.
* White River Segment 4b: The segment description was modified for clarity.
* White River Segment 16a: Unnecessary exclusions were removed from the segment description.
* White River Segment 16b: Segment exclusions were modified to reflect resegmentation.
* White River Segment 20: Exclusions were updated in the segment description.
* White River Segment 25: Existing site-specific temperature standards were reformatted in the tables to provide clarity and consistency.
* Lower Colorado Segment 4a: Exclusions were modified to reflect resegmentation.
* Lower Colorado Segment 11b: The dissolved oxygen standard was corrected to 5.0 mg/L to reflect the Cold 2 Aquatic Life use.
* Lower Colorado Segment 11c: The arsenic standard was corrected to indicate that it is measured as total.
* Lower Colorado Segment 16: Exclusions were updated in the segment description.
* Lower Colorado segments 15c, 15d, 16, 18 and 20: Existing site-specific temperature standards were reformatted in the tables to provide clarity and consistency.
* Lower Colorado Segment 18: The dates for the site-specific temperature standards were corrected to include the month of October.
5 CCR 1002-37.40