5 Colo. Code Regs. § 1002-35.45
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 tine specific statutory autlnority for adoption of tinese regulatory amendments. Tine 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:
Upper Gunnison River Segment 2: This segment excludes Steuben Creek, Willow Creek, and Soap Creek and was modified to also exclude their tributaries.
Upper Gunnison River Segments 15a and 19: Hot Springs Creek below the Hot Springs Reservoir was moved from Segment 19 to Segment 15a to change the temperature standards on this portion of Hot Springs Creek from CS-I to CS-II.
North Fork of the Gunnison River Segments 4a, 4b, and 4c: Segment 4 was split into 4a, 4b, and 4c as part of changes to temperature standards and the Water Supply use. Segment 4b was created to apply CS-II temperature standards on Muddy Creek and its tributaries. Segment 4c was created to remove the Water Supply use from the tributaries to Lake Irwin, which is a small portion of the original Segment 4.
North Fork of the Gunnison River Segments 5a and 5b: Leroux Creek was moved from Segment 5a to Segment 5b to change the temperature standards on Leroux Creek from CS-I to CS-II.
North Fork of the Gunnison River Segments 6a and 6c: Thompson Creek was moved to a new Segment 6c for the purpose of adding a Water Supply use. The description of Segment 6a was updated to include an exception for Segment 6c.
Uncompahgre River Segments 10a, 10b, and 11: The portion of Cow Creek below Nate Creek was moved from Segment 11 to Segment 10a to change the temperature standards on this portion of Cow Creek from CS-I to CS-II. A portion of Kettle Creek was moved to new Segment 10b to facilitate a removal of the Water Supply use.
Uncompahgre River Segments 13a, 13b, and 13c: Segment 13 was split into 13a, 13b, and 13c as part of changes to temperature standards and the Water Supply use. Segment 13b was created to apply CS-II temperature standards East Fork Dry Creek, Pryor Creek, and Spring Creek to Devinny Canyon. Segment 13c was created to apply CS-II temperature standards and add a Water Supply use to Spring Creek from Devinny Canyon to Popular Road.
Uncompahgre River Segments 21 and 22: Segment 21 was divided into segments 21 and 22 to facilitate adoption of a Water Supply use and DUWS sub-classification for Fairview Reservoir, which is in new Segment 22. The description of Segment 21 was updated to include an exception for Segment 22.
Lower Gunnison River Segments 1 and 2: Tine boundary between segments 1 and 2 was moved upstream to Higlnway 65 to increase tine area of application of tine WS-II temperature standards on Segment 2.
Lower Gunnison River Segments 5a and 5b: Segment 5 was divided into segments 5a and 5b to accommodate cinanges in temperature standards. Segment 5a includes North Fork Escalante Creek and was upgraded to CS-I standards, while Segment 5b includes Roubideau Creek, Monitor Creek, and Potter Creek which reclassified as Warm 1 with WS-II standards.
Lower Gunnison River Segments 6a, 6b, and 6c: Segment 6 was divided into segments 6a, 6b, and 6c as part of changes to temperature standards and the Water Supply use. New Segments 6b and 6c were both reclassified as Warm 1 with WS-II standards. A Water Supply use was also added to Segment 6c.
Lower Gunnison River Segments 8a and 8b: Segment 8 was divided into segments 8a and 8b to facilitate a change to CS-II temperature standards for new Segment 8b, which includes Kannah Creek. Segment 8a, which includes Surface Creek, retained its CS-I standards.
San Miguel River Segments 5a and 5b: Segment 5 was divided into segments 5a and 5b to facilitate adoption of a Water Supply use to the mainstem of the San Miguel River from below Naturita Creek to Coal Canyon. Downstream of Coal Canyon does not have a Water Supply use.
San Miguel River Segments 9, 10a, and 10b: Segment 10 was divided into segments 10a and 10b to facilitate a change in temperature standards and use classification. New Segment 10a, which includes the upper reaches of Tabeguache Creek inside the national forest boundary, retains its CS-II standards. New Segment 10b, which includes Naturita Creek and Tabeguache Creek below the national forest boundary were reclassified to Warm 1 with WS-II standards. An exception for Segment 10a was added to Segment 9 for clarity.
San Miguel River Segments 12a, 12b, and 12c: Segments 12a and 12b were modified to facilitate changes to temperature standards and the Water Supply use. The boundary between segments 12a and 12b was changed from Naturita Creek to Horsefly Creek, and Maverick Draw and other tributaries were moved to Segment 12b. Segment 12b was reclassified as Warm 2 with WS-II standards. New Segment 12c includes Calamity Draw below Lincoln Street in Nucia, which was previously part of Segment 12b. The creation of Segment 12c facilitates reclassification as Warm 2 with WS-II standards, and removal of the Water Supply use.
Segment descriptions were also edited to improve clarity, correct typographical errors, and correct spelling errors. These changes are listed in Section P.
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:
North Fork of the Gunnison River: 11 (lead)
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 to Warm:
Uncompahgre River segment: 15b
Lower Gunnison River segments: 5b, 6b, 6c
San Miguel River segments: 10b, 12b
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:
North Fork Gunnison River segment: 11
Uncompahgre River segment: 21
Lower Gunnison River segment: 9
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:
North Fork Gunnison River segment: 6c
Uncompahgre River segments: 12, 13c
Lower Gunnison River segment: 6c
San Miguel River segment: 5a
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 standard. The Water Supply use classification and standards, except for chloride, were removed from the following segments:
North Fork Gunnison River segment: 4c
Uncompahgre River segment: 10b
San Miguel River segment: 12c
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 tinat tinere is scientific uncertainty about tine appropriate standards for cinloride and/or sulfate to protect tine Aquatic Life use, and tinat appropriate standards may need to recognize tinat 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:
A review of the segments with an existing Water Supply use classification showed that some segments were missing one or more standards to protect that use. The full suite of Water Supply standards was added to the following segments:
North Fork of the Gunnison River segment: 11 (iron)
San Miguel River segment: 19 (arsenic)
The commission reviewed all segments with 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. Total copper and molybdenum intakes are calculated from the following equations:
Cu intake mg/day = [([Cu] forage, mg/kg) x (forage intake, kg/day)] + [([Cu] water, mg/l) X (water intake, L/day)] + (Cu supplementation, mg/day)
Mo intake mg/day = [([Mo] forage, mg/kg) x (forage intake, kg/day)] + [([Mo] water, mg/l) x (water intake, L/day)] + (Mo supplementation, mg/day)
The assumed values for these equations are as follows:
[Cu] forage = 7 mg/kg, [Mo] forage = 0.5 mg/kg, forage intake = 6.7 kg/day, [Cu] water = 0.008 mg/L, water intake = 56.8 L/day, Cu supplementation = 0 mg/day, Mo supplementation = 0 mg/day.
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. 35 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:
Upper Gunnison River segments: 9, 11
Acute = e(0.9789*In(hardness) - 3.866)*(1.136672-(ln(hardness)*0.041838))
Chronic = e(0.7977*In(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 CaCOs. 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:
Upper Gunnison River segments: 7, 10a, 10b, 11, 12, 29a, 30, 31
North Fork of the Gunnison River segment: 4c
Uncompahgre River segments: 2, 3a, 3b, 3c, 3d, 3e, 3f, 5, 8, 9
San Miguel River segments: 2, 3a, 3b, 6a, 6b
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 Gunnison River segments: 1,2,4, 5a, 5b, 6b, 6c, 7, 8, 9, 11, 12, 13, 14, 15a, 15b, 16a, 16b, 17a, 17b, 18a, 18b, 19, 21, 22, 23, 24, 25, 26, 29a, 29b, 30, 32, 33, 34, 36, 37, 38
Nortin Forkof tine Gunnison River segments: 1, 2, 3, 4a, 4b, 5a, 5b, 6b, 6c, 7, 8,
9, 10, 11
Uncompalngre River segments: 1, 2, 3a, 3b, 3c, 3d, 3e, 3f, 4a, 4b, 5, 7, 8, 10a, 11, 12, 13c, 16, 17, 18,22
Lower Gunnison River segments: 1, 2, 3, 4a, 4b, 4c, 5a, 5b, 6c, 7a, 7b, 8a, 8b,
10, 11a, lib, 12, 14, 15, 16, 17, 18, 19
San Miguel River segments: 1, 2, 3b, 4a, 4b, 5a, 7, 8, 9, 10a, 10b, 12a, 12b, 13, 14, 18, 19,20
Lower Dolores River segments: la, lb, 2, 3a, 4, 5, 6, 7
The commission reviewed all Warm 2 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 Warm 1 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.
Where the commission downgraded the Aquatic Life use classification to Warm Class 2, the commission reviewed the Antidegradation designation. Pursuant to 31.8(2)(b), the following segments should be designated Use Protected because they are Warm Class 2 and the conditions outlined in 31.8(2)(b)(iii) are not met:
San Miguel River segments: 12b, 12c
The following segments with Outstanding Waters designations were expanded to include the Raggeds Wilderness Area:
Upper Gunnison River segment: 1
Ambient quality-based standards are adopted winere a comprelnensive 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 where appropriate were revised based on new information. Ambient-based standards were revised for the following segments:
Upper Gunnison River segments: 10a, 15a
Uncompahgre River segments: 3a, 3b, 3c, 4b, 4c, 7
The commission reviewed all existing site-specific standards. Based on an evaluation of the available data and information, no changes were adopted at this time.
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 or allowed to expire on 12/31/2017 certain temporary modifications on the following segments:
Upper Gunnison River segment: 12 Uncompahgre River segment: 4b
To remain consistent with the commission's decisions regarding arsenic in section 35.36 , all existing temporary modifications for arsenic of "As(ch)=hybrid" (expiration date of 12/31/21) were retained. An arsenic temporary modification was added to the following segments, which had an existing or newly added chronic arsenic standard 0.02 µg/L and a permitted discharger with a water quality-based effluent limit compliance problem:
Uncompahgre River segment: 12 The commission adopted new Temporary Modifications on the following segments:
Upper Gunnison River segments: 12, 21
There is currently one segment in the Gunnison and Lower Dolores River Basin (San Miguel Segment 12c) that has a discharger specific variance (DSV) for ammonia. The commission reviewed the basis for this DSV and the available information regarding progress toward achieving the highest attainable water quality. The commission determined that this DSV is still appropriate and does not require revision at this time.
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 2012, the new temperature standards were adopted for all segments with an Aquatic Life use classification in Regulation No. 35. 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.
Temperature standards to protect lake trout were added to the following segments:
Upper Gunnison River segment: 38 (Lake San Cristobal, Taylor Park Reservoir, Blue Mesa Reservoir)
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:
North Fork Gunnison River segment: 4b
Uncompahgre River segments: 3c, 13b, 13c
Lower Gunnison River segment: 8b
The following segments were changed from CS-II to WS-II:
Uncompahgre River segment: 15b
Lower Gunnison River segments: 5b, 6b, 6c
San Miguel River segments: 10b, 12b
The beginning and/or end date of the winter season for temperature standards was changed where a use attainability analysis was conducted demonstrating that the winter standards were not attainable during early and/or late winter due to natural or irreversible conditions, and that a delayed start and/or end date is adequate to protect the highest attainable use. Timing of the shoulder season was changed for the following segments:
Upper Gunnison River segment: 8 (summer: June 1 to October 15)
North Fork Gunnison River segment: 3 (summer: March 16 to November 15)
Uncompahgre River segment: 3e (summer: April 1 to November 15)
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. Ambient temperature standards were adopted for the following segments:
Upper Gunnison River segment: 18b
North Fork Gunnison River segment: 3
The commission also intends that the division and interested parties will collect additional data to better characterize the temperature regime and highest attainable aquatic life use in upper Tomichi Creek (Upper Gunnison Segment UG18b), and work to refine the use classifications and temperature standards in upper Tomichi Creek as appropriate in the next triennial review.
In some cases, the existing aquatic life community supported an upgrade in the temperature standard. The following segments were changed from CS-II to CS-I:
Lower Gunnison River segment: 5a
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:
Lower Gunnison River segment: 10
San Miguel River segments: 2, 9
Lower Dolores River segment: 5
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.
In March 2012, the commission adopted interim nutrient values in the Basic Standards (Regulation No. 31) and created a new statewide control regulation (Regulation No. 85) to address nutrients in Colorado. Regulation 31.17 includes interim nutrient values for total phosphorus, total nitrogen, and chlorophyll a for both lakes and reservoirs, and rivers and streams. Due to the phased implementation approach adopted with these criteria (31.17(e)), the commission considered adoption of only total phosphorus and chlorophyll a standards at this time. Nitrogen standards were not considered as part of this rulemaking hearing, but will be considered in the next triennial review, currently scheduled for June 2020.
Total phosphorus and chlorophyll a standards were adopted for waters upstream of all permitted domestic wastewater treatment facilities discharging prior to May 31, 2012 or with preliminary effluent limits requested prior to May 31, 2012, and any non-domestic facilities subject to Regulation No. 85 effluent limits and discharging prior to May 31, 2012. A new section (4) was added at 35.5 describing implementation of the interim nutrient values into the tables at 35.6, and includes a table which lists these facilities and the segment to which they discharge.
For segments located entirely above these facilities, nutrient standards apply to the entire segment.
For segments with portions downstream of these facilities, nutrient standards only apply above these facilities. A note was added to the total phosphorus and chlorophyll a standards in these segments. The note references the table of qualified facilities at 35.5(4).
For segments located entirely below these facilities, nutrient standards do not apply.
For rivers and streams segments, total phosphorus standards were adopted for segments with an Aquatic Life use. Chlorophyll a standards were adopted for segments with either an E or P Recreation use classification.
For lakes and reservoirs segments, a note was added to total phosphorus and chlorophyll standards adopted for lakes in the tables at 35.6, as these standards only apply to lakes larger than 25 acres.
31.17(e)(ii) also allows the commission to adopt numeric nutrient standards for Direct Use Water Supply (DUWS) lakes and reservoirs. No proposals were made to adopt standards based on this provision in this rulemaking (see section M).
31.17(e)(iii) also allows the commission to adopt numeric nutrient standards for circumstances where the provisions of Regulation No. 85 are not adequate to protect waters from existing or potential nutrient pollution. No proposals were made to adopt standards based on this provision in this rulemaking.
Chlorophyll a standards were adopted for the following segments:
Upper Gunnison River segments: 1, 2, 4, 5a, 6a, 6b, 6c, 7, 9, 10a, 10b, 11, 12, 13, 15a, 15b, 16a, 16b, 17a, 17b, 18a, 18b, 19, 20, 21, 22, 23, 24, 26, 29a, 29b, 30, 31, 32, 33, 34, 35, 36, 37, 38
North Fork of the Gunnison River segments: 4a, 4b, 4c, 5a, 5b, 6a, 6b, 6c, 7, 8, 9, 10, 11
Uncompahgre River segments: 1,2, 3b, 3c, 5, 6a, 7, 8, 9, 10a, 10b, 11, 12, 13a, 13b, 13c, 14, 15a, 15b, 16, 17, 18,20,21,22
Lower Gunnison River segments: 3, 4a, 4b, 4c, 5a, 5b, 6a, 6b, 6c, 7a, 7b, 8a, 8b, 10, 11a, lib, 12, 13, 14, 15, 16, 17, 18, 19
San Miguel River segments: 1,2, 3a, 3b, 6a, 6b, 7, 8, 9, 10a, 10b, 11a, lib, 12a, 12b, 12c, 13, 14, 15, 16, 17, 18, 19,20
Lower Dolores River segments: 3a, 3b, 3c, 4, 5, 6, 7, 8
Total Phosphorus standards were adopted for the following segments:
Upper Gunnison River segments: 1, 2, 4, 5a, 6a, 6b, 6c, 7, 9, 10a, 10b, 11, 12, 13, 15a, 15b, 16a, 16b, 17a, 17b, 18a, 18b, 19, 20, 21, 22, 23, 24, 26, 29a, 29b, 30, 31, 32, 33, 34, 35, 36, 37, 38
North Fork of the Gunnison River segments: 4a, 4b, 4c, 5a, 5b, 6a, 6b, 6c, 7, 8, 9, 10, 11
Uncompahgre River segments: 1,2, 3b, 3c, 5, 6a, 7, 8, 9, 10a, 10b, 11, 12, 13a, 13b, 13c, 14, 15a, 15b, 16, 17, 18,20,21,22
Lower Gunnison River segments: 3, 4a, 4b, 4c, 5a, 5b, 6a, 6b, 6c, 7a, 7b, 8a, 8b, 10, 11a, lib, 12, 13, 14, 15, 16, 17, 18, 19
San Miguel River segments: 1,2, 3a, 3b, 6a, 6b, 7, 8, 9, 10a, 10b, 11a, lib, 12a, 12b, 12c, 13, 14, 15, 16, 17, 18, 19,20
Lower Dolores River segments: 3a, 3b, 3c, 4, 5, 6, 7, 8
Also in the March 2012 rulemaking hearing, the commission adopted a sub-classification of the Domestic Water Supply Use called "Direct Use Water Supply Lakes and Reservoirs Sub-classification" (DUWS), in Regulation No. 31, at 31.13(1)(d)(i). This sub-classification is for Water Supply lakes and reservoirs where there is a plant intake location in the lake or reservoir or a man-made conveyance from the lake or reservoir that is used regularly to provide raw water directly to a water treatment plant that treats and disinfects raw water. The commission has begun to apply this sub-classification and anticipates that it will take several basin reviews to evaluate all the reservoirs in the basin. The commission adopted the DUWS sub-classification on the following reservoirs and added "DUWS" to the classification column in the standards tables. The public water systems are listed along with the reservoirs and segments.
Upper Gunnison River segments: 34 (Glazer Reservoir), 37 (Evergreen Lake)
Uncompahgre River segments: 18 (Lake Otonawanda), 22 (Fairview Reservoir)
Lower Gunnison River segment: 16 (Hallenbeck Reservoir, Juniata Reservoir)
San Miguel River segments: 19 (Town Reservoir), 20 (Gurley Reservoir)
31.17(e)(ii) also allows the commission to adopt numeric nutrient standards for DUWS lakes and reservoirs. No proposals were made to adopt standards based on this provision in this rulemaking.
Upper Gunnison River Segments 11 and 12: The commission revised the segment boundary between Segments 11 and 12 to more appropriately reflect the changes in physical conditions, including hardness. In addition, the commission deleted the existing temporary modifications for cadmium, copper, and zinc on Segment 12, and adopted revised seasonal temporary modifications on the mainstem Coal Creek portion of Segment 12. For the period of April to June, the commission adopted the following seasonal temporary modifications with an expiration date of December 31, 2022: cadmium (acute) = 3.5 µg/L, cadmium (chronic) = 2.79 µg/L, copper (acute/chronic) = current condition, and zinc (chronic) = 576 µg/L.
Information submitted by Mount Emmons Mining Company (MEMC) sinowed demonstrated non-attainment of tine cadmium, copper, and zinc water quality standards from April to June, demonstrated or predicted effluent limit compliance problems, and significant uncertainty regarding the extent to which existing quality is the result of natural or irreversible human-induced conditions. Sources identified as contributing to the non-attainment of the water quality standards include, but are not limited to, the iron fen and gossan which are natural sources in Segment 11, the Standard Mine which is a Superfund Site in Segment 11, and the Keystone Mine which is in Segment 12. A current condition temporary modification for chronic cadmium from July to March was also proposed, but prior to the hearing the parties agreed that, in this instance, a compliance schedule is a more appropriate tool to address compliance issues, and the commission agreed with this approach. The commission appreciates the commitment of the parties to work through these issues and encourages continued collaboration among MEMC, the division, and stakeholders about the appropriate implementation options including the terms and conditions of any compliance schedule.
MEMC acquired the U.S. Energy property in early 2016 with the intent, among other things, to work collaboratively with the division and other stakeholders to develop site-specific water quality standards for Coal Creek. After the commission adopted new requirements in Regulation 31.7(1)(b)(ii) in the June 2016 Basic Standards hearing, it became clear that more information would be available in the future to develop and support proposals for ambient-based water quality standards, more specifically to satisfy the new requirements of a comprehensive analysis described in Regulation 31.7(1 )(b)(ii)(B). The commission adopted temporary modifications to allow for development of a comprehensive alternatives analysis to support a proposal for ambient-based standards or other appropriate alternatives. The commission found that an expiration date of December 31, 2022 provides the time necessary to identify the improved water quality conditions that could result from feasible pollution control alternatives addressing human-induced sources, including the Standard Mine and Keystone Mine, and to develop a proposal for ambient-based water quality standards at the 2022 Gunnison River Basin hearing. In establishing this date, the commission considered MEMC's plan to eliminate uncertainty, long-term water quality monitoring plan, commitment to continued collaboration with the stakeholders, and commitment to provide annual progress reports to the division and stakeholders. The commission will review the temporary modifications at the December 2020 and 2021 temporary modification hearings.
For the portion of Upper Gunnison River Segment 12 that includes Coal Creek and the unnamed tributary in the Red Lady Basin whose confluence with Coal Creek is at 38.867899, -107.021435, the commission directs the division to implement the chronic table value or site-specific standards for cadmium, zinc, and copper in a manner that considers seasonality of hardness (i.e., April-June, July-March). For these water bodies, the commission recognizes that seasonality in flow, dissolved metals, and hardness is an important element of the site conditions. Implementation of the numeric standards using the annual mean hardness, for example, would likely understate risks to aquatic life during snowmelt runoff in the spring when dissolved metals are high and hardness is low (approximately April 1 to June 30), and overstate risks during the remainder of the year when dissolved metals typically decrease and hardness levels increase. In this hearing, MEMC initially proposed seasonal standards whose purpose was to ensure the proper consideration of seasonality in permitting and assessments. MEMC withdrew this proposal because the division determined that footnote 3 to Table III in Regulation 31 and footnote 2 to Section 35.6(3) allow the division to account for seasonality in implementing decisions for Coal Creek and the unnamed tributary without the need for a change of standards. The commission agrees with this determination. The commission's intent is that assessment and permitting decisions should derive from and comply with the magnitude, duration and exceedance frequency of the numeric standards that have been assigned to the segment, and that the implementing programs should appropriately consider how aquatic life risks are affected by spatial and temporal variation, particularly where there are sufficient data to characterize such variability.
Upper Gunnison River Segment 20: The definition of LPL, which was erroneously deleted during the 2015 temporary modifications hearing, was replaced. The following text was added to the "Other" box in the segment table:
*Uranium(acute) = lowest practical level
*Uranium(chronic) = lowest practical level
Upper Gunnison River Segment 21: The commission assigned the chronic uranium water supply standard of 16.8-30 µg/L to Segment 21 to clearly define the underlying standard necessary to protect the use. Additionally, the commission adopted a "current condition" temporary modification of the uranium standard with an expiration date of 12/31/2022 for the portion of Marshall Creek from the confluence with Indian Creek to the confluence with Tomichi Creek. Evidence submitted by Homestake Mining Company (HMC) showed non-attainment of underlying standards, a demonstrated water quality-based effluent limit compliance problem and uncertainty regarding the extent to which existing quality is due to natural and/or irreversible human-induced conditions.
HMC is conducting closure and reclamation activities at the Pitch Reclamation Site (site) pursuant to Division of Reclamation and Mining Safety regulations. The site, an inactive uranium mine that ceased operations in 1984, is the main source of uranium loading to Indian Creek (Segment 20) and Marshall Creek (Segment 21). Water quality data from 2001 to 2016 show uranium concentrations decrease with increasing distance from the site outfall located at the headwaters of Indian Creek. The median uranium concentration is 1,060 µg/L at the outfall on Indian Creek (SW-33), 68 µg/L in Marshall Creek immediately downstream of Indian Creek (site MC-2), and 61 and 44 µg/L, at downstream at sites SW-10 and SW-13, respectively. By contrast, upstream of the confluence with Indian Creek, the median uranium concentration in Marshall Creek is 1 µg/L, which demonstrates the correlation between uranium concentrations on Indian Creek and Marshall Creek.
Indian Creek (Segment 20) was previously assigned a narrative "LPL" (lowest practical level) standard for uranium (2012). HMC is currently evaluating methodologies to control uranium loading to Indian Creek from the site in order to define the LPL standard. Ultimately, the controls are expected to reduce uranium loading to Indian Creek, which in turn will lower the concentrations in Marshall Creek. The temporary modification on Segment 21 will allow time for HMC to continue the process of determining the LPL for Indian Creek, the extent to which the legacy mining impacts are reversible, and the effect of site improvements on Segment 21 water quality. The plan for addressing the uncertainty includes determining what best management practices could be implemented, implementation of the management approach, and monitoring subsequent water quality improvements. While the timeline for these activities will likely exceed the 5-year temporary modification, additional water quality data and information regarding progress being made to implement the plan will be available for a review of the temporary modification prior to the expiration date.
In adopting the temporary modification on Marshall Creek, the commission relied on Homestake's commitments to provide updates to the commission in the December 2018 temporary modifications rulemaking hearing. This update is in addition to the regularly scheduled temporary modification reviews that take place the two years prior to expiration, and will focus on progress made by Homestake on the plan outlined in Homestake's Exhibit 10.
Upper Gunnison River Segment 35: The arsenic standard was changed from 0.02 µg/L to 7.6 µg/L, as there is no Water Supply use on this segment and the Water + Fish arsenic standard should not apply.
Uncompahqre River Segment 14: The E. coll standard was corrected to 205, as the previous standard of 206 was a typo.
Lower Gunnison River Segment 2: The cadmium and silver standards for the protection of trout were removed because this segment is classified as Warm.
Lower Gunnison River Segments 14 and 15: The pH standards were corrected to 6.5-9.0 on these segments, as the previous standard of 6.4-9.0 was a typo.
San Miguel River Segment 6a: The site-specific zinc standard of 190 µg/L was erroneously deleted during a previous rulemaking, and was replaced.
The commission corrected tine duration of tine nitrite standard from cinronic to acute on all segments. When the commission adopted the new format for tables in 2016, all nitrite standards were incorrectly included in the "chronic" standards column.
*The following edits were made to improve clarity and correct typographical errors:
*Upper Gunnison River Segment 2: "North Beaver Creek" was changed to "Beaver Creek" and "North Willow Creek" was changed to "Willow Creek" to be consistent with stream names indicated on maps.
*Upper Gunnison River Segment 4: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 5a: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 6a: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 16a: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 16b: The formatting of the site-specific temperature standards was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 25: "Inter-connect" was replaced with "interconnect".
*Upper Gunnison River Segment 26: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 29a: Segment 9b was deleted from the list of exceptions, as this segment does not exist. In addition, the list of exceptions was moved to the end of the segment description to ensure the exclusions apply to the entire segment description.
*Upper Gunnison River Segment 30: The wording regarding exceptions was changed to conform with the rest of the regulation.
*Upper Gunnison River Segment 34: Glazer Reservoir was added to the list of lakes and reservoirs included in the segment.
*Upper Gunnison River Segment 36: Added the word "the" before "Gunnison River".
*Upper Gunnison River Segment 37: Evergreen Lake was added to the list of lakes and reservoirs included in the segment.
*Upper Gunnison River Segment 37: This segment included an exception for "Segment 37"; this was replaced with "Segment 38".
*North Fork of the Gunnison River Segments 2, 4a, 4b, 6a, 9, and 11: "Coal Creek" was replaced by "Anthracite Creek" because Coal Creek is a tributary to Anthracite Creek. Anthracite Creek, not Coal Creek, joins Muddy Creek.
*North Fork of the Gunnison River Segment 5b: A period was added after "5b" in the segment description.
*North Fork of the Gunnison River Segment 6b: The qualifier was changed from "Water+Fish Standards" to "Water + Fish Standards" to be consistent with formatting used in the rest of the regulation.
*North Fork of the Gunnison River Segment 9: Lake Irwin was added to the list of lakes and reservoirs included in the segment.
*Uncompahgre River Segment 3b: The dates for the site-specific temperature standards were corrected to include the month of June. In addition, the formatting of the site-specific temperature standards was changed to conform with the rest of the regulation.
*Uncompahgre River Segment 9: The spelling of "Sneffels" was corrected.
*Uncompahgre River Segment 17: Changed "Segments 16" to "Segment 16".
*Lower Gunnison River Segment 4a: Segments 9 and 13 were deleted from the list of exceptions, as this segment includes stream tributaries and Segments 9 and 13 are reservoirs.
*Lower Gunnison River Segment 4b: Coordinates for the point of diversion for public water supply (38.961321, -108.229830) were added to the segment description.
*Lower Gunnison River Segment 7b: Coordinates for the point of diversion for public water supply (38.965216, -107.876031) were added to the segment description. In addition, the description was corrected to "mainstem of Kiser Creek from the national forest boundary to the confluence with Ward Creek" instead of"... to the confluence with Youngs Creek."
*San Miguel River Segment 1: Removed unnecessary commas and clarified the description.
*San Miguel River Segment 2a: Corrected typos and changed wording regarding exceptions to conform with the rest of the regulation.
*San Miguel River Segment 3b: The dates for the site-specific temperature standards were corrected to include the month of June.
*San Miguel River Segment 7: Removed unnecessary commas and changed "and, all tributaries, and wetlands" to "including all tributaries and wetlands" to be consistent with the rest of the regulation.
*San Miguel River Segment 12a: Deleted Segment 10 from the list of exceptions, as these segments do not overlap.
*San Miguel River Segment 13: Deleted unnecessary commas and clarified the description.
*San Miguel River Segment 14: Corrected a typo and changed wording regarding exceptions to conform with the rest of the regulation.
*San Miguel River Segment 19: This segment included an exception for "Segment 19"; this was replaced with "Segment 20". Town Reservoir was added to the list of lakes and reservoirs included in the segment.
*Lower Dolores River Segment 1a: The formatting of tine site-specific temperature standards was cinanged to conform witin tine rest of tine regulation.
*Lower Dolores River Segment 1 b: The formatting of the site-specific temperature standards was changed to conform with the rest of the regulation.
*Lower Dolores River Segment 7: Morrison Lake, Old Dunham Reservoir, and Belmear Lake were removed from the segment description because these water bodies are not within national forest boundaries.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-35.45