5 Colo. Code Regs. § 1002-36.42
The provisions of C.R.S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; 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:
Rio Grande segments 5a and 5b: Segment 5 was divided into segments 5a and 5b as part of changes to temperature standards. The following streams were moved to new Segment 5b: the mainstem of Alder Creek; mainstem of East Alder Creek, including all tributaries and wetlands, from the source to the confluence with Alder Creek; mainstem of Agua Ramon Creek, including all tributaries and wetlands, from the source to the confluence with the Rio Grande; and the mainstem of Embargo Creek, including all tributaries and wetlands, from immediately above the confluence with Dyers Creek to the confluence with the Rio Grande. The remaining Segment 5 streams were included in Segment 5a. Segment 5a retained CS-I temperature standards and new Segment 5b was assigned CS-II temperature standards.
Rio Grande segments 9a and 9b: Segment 9 was divided into segments 9a and 9b as part of changes to temperature standards. The following streams were moved to new Segment 9b: the mainstem of the South Fork Rio Grande, including all tributaries and wetlands, below Decker Creek. Beaver Creek and its tributaries from the source to Beaver Creek Reservoir remained in Segment 9a, as did the mainstem of the South Fork Rio Grande, including all tributaries and wetlands, from the source to just below Decker Creek. Segment 9a retained CS-I temperature standards and new Segment 9b was assigned CS-II temperature standards.
Rio Grande Segment 11: To facilitate adoption of an Aquatic Life use and standards for the lower portion of San Francisco Creek, Segment 11 was amended to include the portion of San Francisco Creek below Spring Branch, previously included in Segment 15
Alamosa River/La Jara Creek/Conejos River segments 2 and 20: Tributaries to the Alamosa River from a point immediately below the confluence of Bitter Creek to the inlet of Terrace Reservoir, except for listings in segments 4a, 5, 6, and 7, were moved from Segment 20 to Segment 2 to facilitate a change in temperature standards and the Aquatic Life use. Segment 2 retained a Cold 1 Aquatic Life use classification with CS-I temperature standards. Segment 20 was reclassified as Cold 2 Aquatic Life use with CS-II temperature standards.
Closed Basin - San Luis Valley River Basin segments 3 and 6: The mainstem of South Crestone Creek from a point just below the Spanish Creek Trail road crossing (37.981612, -105.713237) to its confluence with Crestone Creek, as well as the mainstem of Crestone Creek from its source at the confluence of North Crestone Creek and South Crestone Creek to the mouth, were moved from Segment 3 to Segment 6 to facilitate removal of the Water Supply use from Segment 6.
Closed Basin - San Luis Valley River Basin segments 12a, 12b, and 12c: Existing Segment 12b was moved to new Segment 12c and retained a Cold 1 Aquatic Life use classification with CS-II temperature standards. The mainstem of Saguache Creek from a point just below the confluence of Fourmile Creek to a point just below the confluence with Ford Creek was moved from Segment 12a to Segment 12b to facilitate a change in temperature standards. Segment 12a retained CS-I temperature standards. Segment 12b was assigned CS-II standards with an ambient-based summer MWAT to be assessed at the location described at 36.6(4).
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:
Rio Grande: 7 (acute chlorine), 20b (acute chlorine, acute and chronic manganese)
Alamosa River/La Jara Creek/Conejos River: 16 (acute and chronic manganese), 18 (acute and chronic manganese)
The commission reviewed information regarding the existing aquatic communities. For segments where the existing aquatic communities are not aligned with the Aquatic Life use, the following segments were downgraded from Cold 1 to Cold 2:
Alamosa River/La Jara Creek/Conejos River: 20
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 standards were applied to the following segments:
Closed Basin - San Luis Valley River Basin: 13, 18
The commission reviewed information regarding the current Recreation use classifications and evidence pertaining to actual or potential primary contact recreation, and no changes were adopted at this time. 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.
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:
Rio Grande: 12, 20a, 23b, 26
Alamosa River/La Jara Creek/Conejos River: 9, 10, 12, 18
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:
Closed Basin - San Luis Valley River Basin: 6
For the segments where the Water Supply use classification and standards were removed, the commission adopted the division's proposal to retain 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:
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.
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:
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. 36 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:
Closed Basin - San Luis Valley River Basin: 10
Acute = e(0.9789*ln(hardness)ì¶3.866)*(1.136672-(ln(hardness)*0.041838)) Chronic = e(0.7977*ln(hardness)ì¶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:
Rio Grande: 4b, 5a, 6
Alamosa River/La Jara Creek/Conejos River: 3a, 3c, 20
Closed Basin - San Luis Valley River Basin: 8, 12a
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:
Rio Grande: 1, 2, 4a, 4b, 4c, 5a, 5b, 8, 9a, 9b, 10, 11, 12, 14, 19, 20a, 21a, 21b, 22, 23b, 25, 26, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38
Alamosa River/La Jara Creek/Conejos River: 1, 2, 9, 10, 11b, 12, 13, 14a, 14b, 15, 17a, 17b, 18, 19, 20, 23, 24, 26, 27, 28, 30
Closed Basin - San Luis Valley River Basin: 1, 2a, 2b, 2c, 3, 4, 9a, 9b, 10, 11, 12a, 12b, 12c, 13, 15, 16, 17, 18
EPA's revised 304(a) Aquatic Life criteria for selenium and ammonia at this time; however, the division is committed to evaluating these new criteria. Studies are currently underway for each parameter to improve understanding of these criteria in the context of water quality conditions in Colorado and how these criteria may be adopted and implemented in Colorado in the future.
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 removed from the following segments:
Alamosa River/La Jara Creek/Conejos River: 9, 10
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.
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 site-specific standards were reviewed, and where appropriate were revised or deleted based on new information. Site-specific standards were deleted from the following segments:
Alamosa River/La Jara Creek/Conejos River: 16 (manganese), 18 (manganese)
Site-specific standards were revised for the following segments:
Rio Grande: 4a, 7
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 allowed to expire on 12/31/2018 temporary modifications on the following segments:
Rio Grande: 4a, 7
The commission deleted temporary modifications on the following segments:
Alamosa River/La Jara Creek/Conejos River: 20
To remain consistent with the commission's decisions regarding arsenic in 36.33, 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:
Rio Grande: 12
Alamosa River/La Jara Creek/Conejos River: 18
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 2013, the new temperature standards were adopted for all segments with an Aquatic Life use classification in Regulation No. 36. 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.
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.
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-I to CS-II:
Rio Grande: 5b, 9b
Alamosa River/La Jara Creek/Conejos River: 20
Closed Basin - San Luis Valley River Basin: 12b
Ambient temperature standards were adopted where a use attainability analysis was conducted demonstrating that elevated ambient temperatures are the result of natural conditions or are not feasible to improve to the level required by the current numeric standard, but are adequate to protect the highest attainable use. New ambient temperature standards were adopted for the following segment:
Closed Basin - San Luis Valley River Basin: 12b
Adequate data or resources were not always available to support a revision of the use classification or a temperature standards change. In these cases, no change was proposed. It is the commission's intent that the division and interested parties work to resolve the uncertainty. There is uncertainty regarding the appropriate use classifications and temperature standards to protect the highest attainable use still exist for the following segments:
Rio Grande: 4b, 10, 12
Alamosa River/La Jara Creek/Conejos River: 9, 10, 11b, 13, 14a, 15, 17b
Closed Basin - San Luis Valley River Basin: 9b, 12c
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.
Rio Grande segments 4a and 7: The commission adopted additional changes to Rio Grande Segment 4a and Segment 7 temporary modifications and site-specific feasibility-based standards that it adopted in December 2013, and modified in December 2015. See Section 36.35.
The commission allowed the Segment 4a temporary modifications for chronic cadmium, lead, and zinc, and the Segment 7 temporary modifications for acute and chronic cadmium, copper, lead, and zinc, and acute silver, to expire on 12/31/2018.
Site-specific feasibility-based standards for Segment 4a for acute and chronic cadmium, chronic lead, chronic manganese, and acute and chronic zinc, and for Segment 7 for acute and chronic cadmium, copper, lead, manganese, and zinc, and acute silver, were first adopted in December 2013 with two tiers. See Section 36.35 . These tiered feasibility-based standards were based on improvements in water quality tied to future reopening of the Bulldog Mine. Tier 1 was to be effective 1/1/2017-12/31/2018. Tier 2 was to be effective 1/1/2019. In December 2015, these dates were delayed by two years, resulting in Tier 1 becoming effective 1/1/2019-12/31/2020, and Tier 2 on 1/1/2021.
Due to a delay in the reopening of the Bulldog Mine, the commission delayed the effective dates for the tiered feasibility-based standards to allow time for the activities in Section 36.35 to take place. The new effective dates for Tier 1 is 1/1/2022-12/31/2023. Tier 2 becomes effective 1/1/2024. The commission also adopted Rio Grande Silver, Inc.'s (RGS) proposed updated Tier 1 and Tier 2 values that are based on 2012-2017 data and improved modeling assumptions that more accurately predict Tier 1 and Tier 2 water quality. See RGS Exhibits 10 and 12. For Segment 4a, Tier 2 cadmium concentrations are predicted to attain the 2016 EPA cadmium criteria, which the commission will consider for state-wide application at a hearing in December 2019.
In addition, because existing water quality does not attain table value standards for several metals, but represents the highest attainable conditions in the absence of Nelson Tunnel remediation or restart of the Bulldog Mine, the commission adopted interim, ambient-based site-specific standards for several metals for segments 4a and 7. See Section 36.6 -(c). The ambient-based standards will be effective from 1/1/2019 to 12/31/2021, or until Tier 1 feasibility-based standards become effective. The commission also adopted assessment locations for the ambient and tiered standards in Section 36.6(4)(b)-(c).
RGS will update the commission regarding the status of the Bulldog Mine operations and tiered standards at future commission rulemakings, including the December 2020 Temporary Modifications rulemaking. Decisions made in the current hearing are subject to future review as additional information, such as water quality data, metals treatment, or other opportunities for load reductions, becomes available. In addition, to ensure it will be possible to review and determine the need to update the ambient and tiered feasibility-based site-specific standards, continued data collection at the adopted assessment locations will be necessary.
Recoverable notation (T) to the mercury Aquatic Life and Water Supply standards. The standards apply to the total recoverable fraction of all forms, both organic and inorganic, of mercury in water. Multiple forms of mercury exist in the environment and these forms differ dramatically in both their potential to cause toxic effects and their availability for uptake by organisms. Certain aquatic conditions can lead to the conversion to the highly bioaccumulative, toxic, organic form (methylmercury). The mercury standards are designed to provide protection from the accumulation of those toxic forms and therefore, the standards address all forms of mercury. The addition of the Total Recoverable notation does not represent a change in current Colorado policy or procedures.
The following edits were made to segment descriptions to improve clarity and correct typographical errors:
* The formatting of the tables in Appendix 36-1 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.
* Existing site-specific temperature standards for Rio Grande segments 20a, 21b, and 23b, and Closed Basin segments 2c and 19 were reformatted in the tables to provide clarity and consistency.
* Existing site-specific metals standards for Rio Grande segments 4a and 7 and Alamosa River/La Jara Creek/Conejos River Segment 8 were reformatted in 36.6(4) to improve readability.
* Rio Grande Segment 3: The reference to Seepage Creek was removed from the segment description, as this stream is not located at the outlet of Santa Maria Reservoir, but rather on the south side of Santa Maria Pass. As a result of this change, Seepage Creek will reside in Rio Grande Segment 2.
* Rio Grande Segment 5a: The word "the" was added before "Hwy 122 bridge" to improve clarity.
* Rio Grande segments 6 and 7: Coordinates for the Park Regent Mine Dump were added.
* Rio Grande Segment 7: Commas were modified for clarity.
* Rio Grande segments 12 and 13: Coordinates for the county road crossing were added. Reference to the "Old State Bridge east of Lobatos" was removed.
* Rio Grande Segment 15: Commas and spacing were modified for clarity. The duration of the cadmium and mercury standards were corrected from chronic to acute.
* Rio Grande Segment 17: Wetlands were included in the description twice, so one was removed.
* Rio Grande Segment 18: The Fish Ingestion qualifier was removed from this segment, as it was originally added in error in a past rulemaking.
* Rio Grande segments 19 and 34: Coordinates for the Monte Vista Canal were added.
* Rio Grande Segment 20a: The dates for the site-specific temperature standards were corrected to include the month of October.
* Rio Grande Segment 20b: This segment does not have a Water Supply use, so the manganese Water Supply standard was deleted.
* Rio Grande segments 21a and 21b: Replaced the latitude line with coordinates.
* Rio Grande Segment 21b: The dates for the site-specific temperature standards were corrected to include the months of October and June.
* Rio Grande Segment 23b: The dates for the site-specific temperature standards were corrected to include the month of October.
* Rio Grande Segment 25: Commas were modified for clarity.
* Rio Grande segments 28 and 29: Replaced the segment boundary of "the outlet of Salzar Reservoir" with coordinates for a road crossing next to the reservoir. Salzar Reservoir does not appear to have an outlet to Rito Seco.
* Rio Grande Segment 31: Corrected typos to improve consistency and clarity.
* Rio Grande Segment 36: Commas were modified for clarity.
* Rio Grande Segment 38: Replaced the comma at the end of the description with a period.
* Alamosa River/La Jara Creek/Conejos River Segment 3b: Deleted the word "the" from before "Wightman Fork" to improve clarity.
* Alamosa River/La Jara Creek/Conejos River segments 4b and 5: Moved tributaries and wetlands language to improve consistency and clarity.
* Alamosa River/La Jara Creek/Conejos River segments 5 and 6: Coordinates for the township description were added.
* Alamosa River/La Jara Creek/Conejos River Segment 7: Unused standards were deleted from the table.
* Alamosa River/La Jara Creek/Conejos River Segment 11a: Rephrased to improve clarity.
* Alamosa River/La Jara Creek/Conejos River Segment 11b: Corrected typos and rephrased to improve clarity.
* Alamosa River/La Jara Creek/Conejos River segments 15 and 16: Changed "San Antonio River" to "Rio San Antonio".
* Alamosa River/La Jara Creek/Conejos River Segment 16: Replaced the mercury standard of "TVS" with "0.01".
* Alamosa River/La Jara Creek/Conejos River Segment 20: Commas and spacing were modified for clarity.
* Alamosa River/La Jara Creek/Conejos River Segment 21: Added Segment 20 as an exception to this segment. The duration of the cadmium and mercury standards were corrected from chronic to acute.
* Closed Basin - San Luis Valley River Basin Segment 4: Corrected a typo and added a comma for clarity.
* Closed Basin - San Luis Valley River Basin Segment 8: Added a comma and clarified the segment description.
* Closed Basin - San Luis Valley River Basin Segment 9a: The duration of the mercury standard was corrected from chronic to acute. Unused standards were deleted from the table.
* Closed Basin - San Luis Valley River Basin Segment 11: Rephrased language regarding exceptions to improve consistency and clarity.
* Closed Basin - San Luis Valley River Basin Segment 12a: Added "with" before "Ford Creek".
* Closed Basin - San Luis Valley River Basin Segment 13: Corrected a typo and clarified the segment description.
* Closed Basin - San Luis Valley River Basin Segment 18: Added a space between "16" and "17".
* Closed Basin - San Luis Valley River Basin Segment 19: The temperature standards for this segment were corrected. CLL temperature standards were applied to replace the missing DM values. The site-specific summer MWAT of 21.2°C was inadvertently deleted during a previous rulemaking, and was replaced. In addition, the dates for the summer temperature standards were corrected from "1/1-3/31" to "4/1-12/31".
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-36.42