5 Colo. Code Regs. § 1002-32.61
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:
Upper Arkansas River Segment 5a and 5b: Segment 5 was divided into segments 5a and 5b as part of changes to temperature standards. Temperature standards were changed from CS-I to CS-II on new Segment 5b: Mainstem of Trout Creek from its source to Trout Creek Reservoir, including all tributaries and wetlands. The remaining portions of Segment 5 were moved to new Segment 5a: All tributaries to the Arkansas River, including wetlands, from the source to immediately below the confluence with Brown's Creek, except for specific listings in segments 5b through 12b. The segmentation description for 5a was edited to exclude specific listings in new segment 5b.
Upper Arkansas River segments 14d, 14e and 14f: All tributaries Segment 14 was split into new Segments 14d, 14e and 14f to facilitate a change in the use classifications and temperature standards. Temperature standards were changed from CS-II to WS-II on new Segment 14d: All tributaries to the Arkansas River, including wetlands, which are not on National Forest lands, from immediately above the confluence of 6-mile Creek (38.405677, -105.122321) to the inlet to Pueblo Reservoir, except for specific listings in segments 14a, 14c, 14e, 14f, and 15-27. The remaining portions of Segment 14 were moved to new Segment 14e: All tributaries to the Arkansas River, including wetlands, which are not on National Forest lands from the Chaffee/Fremont County line to immediately below the confluence with Chandler Creek (38.407024,-105.137940). Newlin Creek (except for listings in segment 15b), Mineral Creek, Adobe Creek, and Oak Creek, including all tributaries and wetlands which are not on National Forest Service Land. As diverse and sensitive species were surveyed in these streams the Aquatic Life use classification was changed from Cold 2 to Warm 1 for new Segment 14d and from Cold 2 to Cold 1 for new Segment 14e. During the review of the aquatic life community in these streams, a reproducing population of brook trout were discovered in Turkey and Little Turkey Creeks and so were moved to new segment 14f: Turkey Creek including all tributaries and wetlands from its source to immediately below the confluence with Little Turkey Creek at 38.594727, -104.851458. to facilitate adoption of protective CS-I temperature standards.
Upper Arkansas River Segment 15a and 15b: Segment 15 was divided into segments 15a and 15b as part of changes to temperature standards. Temperature standards were changed from CS-I to CS-II on new Segment 15a: Mainstem of Badger Creek from the source to the confluence with the Arkansas River, including all tributaries and wetlands. Mainstem of Texas Creek from the forest service boundary to the confluence with the Arkansas River, including all tributaries and wetlands which are not on forest service land. The remaining portions of Segment 15 were moved to new Segment 15b: Mainstem of Grape Creek, including all tributaries and wetlands, from the source to the outlet of De Weese Reservoir, except for specific listings in segment 25. Mainstems of Hayden, Hamilton, Stout, and Big Cottonwood Creeks, including all tributaries and wetlands, from their sources to their confluences with the Arkansas River. Tributaries and wetlands to Texas Creek which are on Forest Service Land. Mainstem of Newlin Creek from the National Forest boundary to County Road 92 (38.300765, -105.140927). The segment description for Segment 15b was also given coordinates for County Road 92.
Middle Arkansas River Segment 13b and 13c: All tributaries and wetlands to the Cucharas and Huerfano Rivers not on forest service lands, except for specific listings in 13a and 13b, were moved from Lower Arkansas segment 2a to Middle Arkansas Segment 13c to reflect the actual location of these streams which are located in the Middle Arkansas River Basin. The segment description for 13b was also edited to align with this change.
Middle Arkansas River Segment 27: Segment 27 (Teller Reservoir) was moved to new segment Upper Arkansas Segment 41 to reflect Teller Reservoir's location in the Upper Arkansas River Basin.
Lower Arkansas River Segments 2a and 2d: A tributary of Segment 2a was moved to new Segment 2d: Unnamed tributary from the source north of county road 350 (37.307, -104.29) to the confluence with the Purgatoire River, to facilitate 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 O.
Some segments assigned an Aquatic Life use classification were missing a standard to protect that use. The commission adopted the missing standards for the following segments:
Upper Arkansas River: 14e (full suite Aquatic Life use standards), 20b (chronic total phosphorus and nutrient footnote), 23 (acute chlorine)
Fountain Creek: 5 (arsenic)
Lower Arkansas River: 2a (full suite Aquatic Life use standards), 6a (full suite aquatic life use standards), 6b (full suite Aquatic Life use standards),
The commission reviewed information regarding the existing aquatic communities. For segments lacking an Aquatic Life use classification, a use was added where biological information demonstrated that these waters are capable of sustaining aquatic biota. Additionally, Class 2 segments with high MMI scores or a wide variety of fish species were upgraded from Class 2 to Class 1.
The following segments were upgraded from Cold 2 to Cold 1:
Upper Arkansas River: 14e
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:
Upper Arkansas River: 14d
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:
Upper Arkansas River: 14a
Middle Arkansas River: 9
Lower Arkansas River: 9b
The division withdrew proposals to add the Water + Fish qualifier and associated standards as applied to the following segments. The division and Colorado Parks and Wildlife (CPW) will work with stakeholders to evaluate whether or not a fish ingestion qualifier is needed in the next basin hearing.
Upper Arkansas River: 8b
Middle Arkansas River: 6b
Fountain Creek: 6, 11
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.
Some segments assigned a Recreation use classification were missing a standard to protect that use. The commission adopted the missing standards for the following segments:
Upper Arkansas River: 20b (chronic chlorophyll and nutrient footnote)
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:
Middle Arkansas River: 4c, 4d, 12, 14
Lower Arkansas River: 7
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:
Lower Arkansas River: 2d
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:
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. 32 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))
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:
Upper Arkansas River: 1a, 2b (acute only), 2c (acute only), 3, 4a, 5, 7, 11, 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:
Upper Arkansas River: 1a, 1b, 2a, 2c, 3, 4a, 4b, 5a, 5b, 7, 8a,10, 12a, 12b 13, 14b, 15a, 15b, 16a, 16b, 16c, 17a, 17c, 18, 19, 20b, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41
Middle Arkansas River: 1, 2, 3, 4c, 4d, 5a, 5b, 6a, 6b, 7a, 7b, 9, 11a, 11b, 12, 13a, 13b, 13c, 14, 17, 18a, 18b, 19, 20, 21, 22, 23, 24, 25, 26, 28
Fountain Creek: 1a, 1b, 2a, 2b, 3a, 3b, 4b, 4c, 4e, 5a, 6, 7a, 8, 9, 10, 11
Lower Arkansas River: 1a, 1b, 1c, 3a, 3c, 4a, 5a, 5b, 5c, 7, 8, 9a, 9b, 10, 11, 14, 15, 18, 19
The commission reviewed all segments designated Use Protected to determine if the Use Protected designation was still warranted. Based upon available water quality data that meet the criteria of 31.8(2)b, the Use Protected designation was not removed from any segments.
The commission reviewed all Reviewable segments to determine if this Antidegradation designation was still warranted. Based upon available water quality data that fails to meet the criteria of 31.8(2)b, the Reviewable designation was not removed from any segments.
Ambient quality-based standards are adopted where a comprehensive analysis has been conducted demonstrating that elevated existing water quality levels are the result of natural conditions or are infeasible to reverse, but are adequate to protect the highest attainable use.
All existing ambient-based standards were reviewed and where appropriate were revised or deleted based on new information. Ambient-based standards were deleted from the following segments:
Middle Arkansas River: 4e (acute and chronic selenium), 18b (acute and chronic selenium).
Fountain Creek: 2a (chronic selenium and sulfate), 2b (acute selenium)
Prior to the June rulemaking hearing, the division withdrew its ambient quality-based standards proposals for Fountain Creek segments 2a and 2b, and Pueblo West withdrew its proposals for Middle Arkansas segments 4a (Wildhorse Creek) and 4g (Pesthouse Gulch). The standards at-issue for Fountain Creek were selenium, sulfate and iron; while selenium was the sole focus in the Middle Arkansas segments. The impetus for withdrawal was an acknowledgment by both parties that certain requirements from the 2016 revisions to the Regulation No. 31 ambient quality-based standards provisions to support the proposals had not been adequately addressed. Specifically, the division and Pueblo West had not fully developed the supporting analyses required by section 31.7 to identify sources and causes of elevated pollutant levels, characterize the highest attainable use, support retaining or revising current uses, or complete comprehensive alternatives analyses to identify whether and to what degree anthropogenic sources/causes could be addressed to improve water quality.
Where existing quality did not attain table value standards, the commission retained the current ambient-based standards in place for these segments for the time being. Where existing quality attained table value standards (i.e., Fountain Creek Segment 2a chronic selenium and sulfate; Fountain Creek Segment 2b acute selenium) or adequate information was not available to support retaining the ambient-based standards (i.e., Middle Arkansas segments 4e and 18b acute and chronic selenium), the commission reverted to table value standards for these segments. For Middle Arkansas segments 4e and 18b, evidence exists which demonstrates the occurrence of naturally-elevated selenium concentrations in these segments; however, adequate supporting information was not available to determine the extent of anthropogenic impacts, the feasibility to reverse such impacts, and the highest attainable water quality condition and use for these waterbodies.
The 2016 revisions to Regulation No. 31 provide that ambient quality-based standards are appropriate where a detailed analysis is conducted that identifies all sources and causes of elevated pollutant levels. In situations where any of the sources/causes are determined to be attributable to anthropogenic activity, a comprehensive alternatives analysis must be conducted to identify the extent to which conditions could be improved from implementing feasible pollution controls. The commission recognizes that the "comprehensive analysis" required by section 31.7 -- the analysis to identify all pollution sources, and where non-natural sources are identified, the analysis to identify improved water quality conditions that could result from feasible pollution controls -- can be time and resource intensive. Prior to the next triennial review, the division has committed to working with stakeholders to evaluate and update the previous source identification and analysis efforts on Fountain Creek Segments 2a and 2b, to meet the Regulation 31 provisions and determine the appropriate ambient-based standards. Pueblo West has also committed to continue its current efforts of source identification and control for the Middle Arkansas segments, and will provide an update at the next triennial review hearing.
In the interim, the division has also expressed its intent to work closely with other parties on their ambient quality-based standards proposals to help ensure that the parties' supporting analyses are sufficiently comprehensive to satisfy the 2016 regulatory requirements and the intent behind those requirements. In addition, the division will continue to improve existing resources (such as the ambient standards checklist developed for the 2016 Regulation No. 31 hearing), work to better understand non-point source identification and reversibility, gain experience on alternatives analysis development, and increase its knowledge of feasible pollution control alternatives.
The commission reviewed all other existing site-specific standards. Based on an evaluation of the available data and information, no additional changes were adopted at this time.
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:
Middle Arkansas River: 4b and 6b
Lower Arkansas River: 1a
To remain consistent with the commission's decisions regarding arsenic in section 32.51 , 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 Arkansas: 9b
There is currently one segment in the Arkansas River Basin (Lower Arkansas Segment 1b) that has a discharger specific variance (DSV) for selenium. 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.
Lower Arkansas Segment 1a (City of Pueblo): The commission adopted a DSV for Lower Arkansas Segment 1a for selenium and sulfate that represents the highest degree of protection of the classified uses that is feasible for the City of Pueblo James R. DiIorio Water Reclamation Facility. Selenium and sulfate are naturally present in the Pierre Shale underlying the City of Pueblo. Groundwater with high selenium and sulfate concentrations as a result of contact with the Pierre Shale enters the Pueblo sewer collection system primarily through groundwater infiltration. Even though the Pueblo WRF removes some selenium, there are elevated selenium and sulfate concentrations in the effluent. Pueblo demonstrated that it is currently not technologically feasible to comply with selenium and sulfate water quality based effluent limits. Based on the alternatives analysis and other evidence submitted by Pueblo, the commission concluded that the highest degree of protection of the classified uses would be achieved through source control measures. The measures are targeted to reduce groundwater infiltration from Basins 2 and 3 within the Pueblo sewer collection system, where elevated selenium and sulfate concentrations have been observed.
The commission concluded that the resulting effluent concentration could not be predicted from available data, and therefore in Section 32.6 the commission adopted narrative alternative effluent limits with enforceable requirements to be implemented during the term of the variance that constitute a quantifiable expression of the highest attainable condition. These include a description of control measures for selenium and sulfate expressed as the number of manholes sealed and the amount of sewer lining measured in terms of the surface area of pipe lined instead of linear feet, to account for the higher cost of lining larger-diameter pipe. The commission also recognized that the conditions need to be flexible enough for Pueblo to target efforts where they will have the greatest impact, and so the number of manholes sealed or the amount of pipe lined may be reduced to allow for other efforts including repair of service lines or taps.
Through the economic feasibility test, Pueblo demonstrated that user fees exceeding 1.5% of median household income would result in substantial and widespread social and economic impact; therefore, pollutant control alternatives exceeding $10 million were determined not to be economically feasible at this time. During the DSV term, Pueblo will be required to spend $10 million to implement a comprehensive source control, sampling, analysis, and optimization adaptive management program. The adaptive management program will include the following elements, in order of priority:
* Lining up to 175,000 ft2 in the sewer collection system in Basins 2 and 3.
* Sealing up to 400 manholes in Basins 2 and 3.
* The amount of sewer lining and manhole sealing may be reduced by:
* Repair of service taps in poor condition;
* Repair of service lines in poor condition; or
* Additional effort where epoxy sealing of manholes is insufficient to control I & I.
* A comprehensive long-term sampling and analysis program to identify source control projects and evaluate the effectiveness of implemented controls.
* Investigation of the contribution from sump pumps.
* Pilot testing to determine the feasibility of treatment optimization to reduce selenium, and implementation of feasible treatment measures.
During the duration of the DSV, Pueblo will continue to study selenium and sulfate treatment optimization and technologies to inform future commission review of the DSV. This effort will include a long-term comprehensive sampling and analysis program, in order to better understand the seasonal and climatic controls on sulfate and selenium and to better evaluate the effectiveness of controls under a variety of climatic conditions. The commission will conduct a re-evaluation of the DSV in December 2020, December 2023, and December 2026. At these periodic reviews, the commission will determine whether the requirements of the DSV continue to be the highest attainable condition. In 2020, the commission will review Pueblo's progress implementing the pollutant minimization plan and any new data collected since the DSV was adopted. In 2023, Pueblo will provide an updated economic feasibility analysis and an updated alternatives analysis, utilizing the results of pilot studies and review of any advancements in the state of selenium treatment technologies. The plan for the re-evaluation in 2026 will be determined during the 2023 rulemaking hearing.
The requirements of the DSV will be either the AEL identified at the time of the adoption of the variance, or the highest attainable condition identified during any re-evaluation rulemaking hearing held by the commission. The commission expects that by implementing the requirements of this variance, Pueblo will achieve some level of control over selenium and sulfate through source control and treatment optimization, such that a numeric alternative effluent limit can be derived in the future, if a subsequent DSV is determined to be necessary.
The commission ensures that the discharge will not contribute to any lowering of the currently attained ambient water quality through its rule at 31.9(5), which requires initial effluent limits to be developed and implemented at the time of permitting that at a minimum represent the level currently achieved. In addition, implementation of Pueblo's pollutant minimization plan will result in incremental improvement throughout the term of the variance, which will prevent any further degrading of water quality.
Lower Arkansas Segment 1b (City of Las Animas): The commission adopted a DSV for Lower Arkansas River Segment 1b for chronic selenium that represents the highest degree of protection of the classified use that is feasible for the City of Las Animas. The city's municipal source water is alluvial well water, which has elevated levels of geogenic selenium. The city treats all raw water through a reverse osmosis treatment system, thus the primary source of selenium in the city's discharge is from the reverse osmosis water treatment plant brine. Las Animas submitted a comprehensive alternatives analysis which demonstrated that compliance with the selenium WQBEL would cause substantial and widespread adverse social and economic impacts in the area where the discharge is located. Alternatives that would allow Las Animas to meet the selenium WQBEL, such as disposal of water treatment residual process water by injection well, or evaporation, would result in user fees that exceed the community's ability to pay. The commission determined that the threshold for substantial and widespread social and economic impacts would be user fees exceeding the current rate of 1.3-1.6%- of median household income for Las Animas' residents.
The commission determined that the highest degree of protection of the classified use that is feasible can be achieved through implementation of a Pollutant Minimization Plan providing for source well optimization, conserving water, repairing losses from the water distribution system and reducing groundwater infiltration to the collection system. Since there is insufficient data at this time to quantify the expected effluent quality that would result through these measures, the commission has adopted a narrative alternative effluent limit (AEL) with enforceable requirements in lieu of a numeric limit. The best feasible effluent quality that can be achieved through source well optimization is expected to be in the range of 0.8 - 28.4 µg/L for Las Animas' combined discharge, which is the range of effluent concentrations that has been achieved under current operating conditions since 2010.
There is significant uncertainty at this time regarding whether compliance with the underlying standard is feasible though optimization of source wells, since there is limited data available on individual source well concentrations. It is not yet known how much concentrations in the source wells will change over time, particularly when operated at different flow rates. By 12/31/2025, if compliance with water quality based effluent limits based upon the underlying standards remains infeasible, then in order to make progress toward identifying longer-term solutions for compliance, the commission has determined that Las Animas should also complete a pilot study for wetland treatment of the city's reverse osmosis brine.
At the re-evaluation of this DSV at the next Arkansas Basin rulemaking hearing in 2023, the commission will review Las Animas' progress implementing the pollutant minimization plan and determine whether the requirements of the DSV continue to be the highest attainable condition. The requirements of the DSV will either remain at the AEL identified at the time of the adoption of the variance, or be modified to the highest attainable condition identified during any re-evaluation rulemaking hearing held by the commission. The commission expects that by implementing the requirements of this variance, Las Animas will be able to quantify the degree of reduction in selenium that is feasible to achieve through source water optimization and other measures, such that a numeric alternative effluent limit can be derived in the future, if a subsequent DSV is determined to be necessary.
The commission ensures that the discharge will not contribute to any lowering of the currently attained ambient water quality through its rule at 31.9(5), which requires initial effluent limits to be developed and implemented at the time of permitting that at a minimum represent the level currently achieved. In addition, implementation of Las Animas' pollutant minimization plan and source water optimization will result in improvement throughout the term of the variance, which will prevent any further degrading of water quality.
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. 32. 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 Arkansas River: 30 (Turquoise Reservoir, Mt Elbert Forebay and Twin Lakes (Upper and Lower)
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-II to CS-I:
Upper Arkansas River: 14f
The following segments were changed from CS-I to CS-II:
Upper Arkansas River: 5b, 15a
The following segments were changed from CS-II to WS-II:
Upper Arkansas River: 14d
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:
Upper Arkansas River: 13, 14c, 17c, 18, 21b, 23, 24, 27
Middle Arkansas River: 1, 2, 5a, 5b, 7a, 7b, 11a, 11b, 13b, 17,
Fountain Creek: 1a, 3a, 5b
Lower Arkansas River: 1b, 3a, 5a, 5b, 5c, 6a, 07, 16c
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.
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 began to apply this sub-classification in 2013 and anticipated that it would 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 Arkansas River: 30 (Twin Lakes and Mt. Elbert Forebay), 37 (Ott Reservoir)
Fountain Creek: 8 (Big Tooth Reservoir, Lake Moraine, Woodmoor Lake), 11 (Gold Camp Reservoir, Lower Reservoir, Keeton Reservoir, South Suburban Reservoir, Unknown Reservoir at 38.70939, -104.82928)
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 Arkansas Segment 8b: The commission extended the expiration date to 06/30/2020 for the temporary modifications for Segment 8b for chronic cadmium, and acute and chronic zinc. This additional time allows for collection of additional biological and temperature/water quality data in ponded wetland habitat in Iowa Gulch and several similar reference streams free from the influence of elevated metals concentrations to resolve the uncertainty regarding the resident biota and appropriate standards for this segment. Efforts will specifically target Hyalella azteca, as lentic habitat waters and emergent vegetation in Iowa Gulch are available; however, this species was not found in previous sampling efforts, and additional data are needed to determine if this species could be expected to be present in Iowa Gulch.
Middle Arkansas Segment 6b: Based upon information submitted by Public Service Company of Colorado (PSCo), the commission adopted a site-specific ambient-based daily maximum (DM) temperature standard for Middle Arkansas Segment 6b of 32.6°C (DM) for March - November, with the TVS of WS-II applying during the winter months.
The commission determined that the highest attainable uses for Segment 6b are the existing classifications of Agriculture, Aquatic Life Warm 2, Recreation E, and Water Supply, and that the ambient temperatures are adequate to protect these uses. To accurately represent spatial and temporal variability in natural temperature conditions, PSCo submitted water quality data from locations throughout the segment, including upstream and downstream of PSCo's Comanche Station discharge. These data demonstrate that natural conditions within the St. Charles River watershed are solely driving elevated daily maximum instream temperatures during the summer months. The commission removed the temporary modification of the DM standard that had previously been in place on Middle Arkansas Segment 6b.
An extension of the current condition temporary modification for chronic temperature from December-February was also proposed with an expiration date of 12/31/2024, but PSCo withdrew its proposal and the existing temporary modification will remain in place with an expiration date of 12/31/2018.
Fountain Creek Segment 4: The commission adopted a proposal for the resegmentation of Segment 4 of the Fountain Creek sub-basin. Segment 4 previously included all tributaries to the mainstem of Monument Creek and Fountain Creek, outside of National Forest or Air Force Academy lands, covering approximately 100 tributaries. These tributaries drain significantly different land uses ranging from mountainous to industrial areas, and have different water quality. Segment 4 was classified for Agriculture, Recreation E, Aquatic Life Warm 2, and Water Supply, and had a Use Protected designation. After extensive data collection, evaluation and field observations, the tributaries were subdivided into segments 4a, 4b, 4c, 4d, 4e and 5a, or moved to existing Segment 3a. Existing Segment 5 was renamed to create Segment 5b.
The resegmentation of Segment 4 was based on the Aquatic Life and Water Supply uses while assuming all tributaries would retain the existing Agriculture and Recreation E uses. Colorado Parks and Wildlife (CPW) provided aquatic life information collected on the various tributaries and their professional opinion on what species would be expected to be found across the watershed. Macroinvertebrate data were also used to determine Class 1 or 2 Aquatic Life uses. Most of the tributaries continue to support Aquatic Life Warm 2 classifications (segments 4a, 4b, 4d and 4e), while some tributaries were determined to be Aquatic Life Class 1 (segments 4c and 5a). Tributaries that support cold water species were moved to Segment 3a (existing) which has an Aquatic Life Cold 1 classification.
Water supply information for existing wells and surface water intakes was obtained from the Colorado Decision Support System website and information provided by AF CURE for planned future water supplies. Alluvial wells were evaluated in accordance with the division's Water Supply Identification Methodology for potential hydrologic connection to a tributary as the tributaries are all small streams with alluvial properties that would match the assumptions of the division's methodology. Wells that are greater than 200 feet from a stream or are screened at a depth greater than 60 feet were determined to be outside of the alluvium and therefore not connected to a tributary. Future uses were evaluated for tributaries that did not have a Water Supply use and were determined to be unlikely if a tributary resided within a water provider's service area boundary and the water provider has requirements to connect to the water system. Future use was considered unlikely in areas such as Fort Carson and the Air Force Academy as development is unlikely and water is provided by another water provider. The tributaries from the Pueblo County line to Pueblo West and Pueblo, as well as Black Squirrel Creek in the Monument area were determined to have the potential for future use as these are outside of a water providers service area and the potential for a new well to be installed may exist.
The tributaries were divided as tributaries to Monument Creek with Aquatic Life Warm 2 and without a Water Supply (Segment 4a), tributaries to Monument Creek with Aquatic Life Warm 2 and with a Water Supply (Segment 4b), tributaries to Monument Creek with Aquatic Life Warm 1 and Water Supply (Segment 4c), tributaries to Fountain Creek with Aquatic Life Warm 1 and without a Water Supply (Segment 4d), and tributaries to Fountain Creek with Aquatic Life Warm 2 with a Water Supply (Segment 4e). The tributaries in segments 4a, 4b, 4d and 4e continue to be designated as Use Protected based on Regulation 31.8(2)(b)(iii)(B) where the segments do, or would, qualify for 303(d) Listing of two or more parameters (typically E. coli and selenium). Segment 4c was determined to be Reviewable.
The Aquatic Life Cold 1 tributaries that were moved to Segment 3a either have a Water Supply use and/or have water quality that would require a Reviewable designation. Except for adding these new streams to Segment 3, no other changes have been made.
Segment 5 has been renamed as Segment 5b, and Segment 5a was created, both of which have a Warm 1 Aquatic Life use. Segment 5a has been designated as Water Supply and Recreation E as opposed to Segment 5b (current Segment 5) which is Recreation N. The segment descriptions were altered to include latitude and longitude instead of the irrigation diversion which no longer exists. No other changes have been made to these segments.
For future use and recording of the decision of which tributaries went to which segment, the following table is included to record the latitude and longitude of each tributary near the point of confluence with Monument or Fountain Creek. These points were chosen based on using GIS and the division's coverage maps in NAD83.
Stream Name | Latitude | Longitude | Final Segment |
North Monument Creek | 39.114968 | -104.910761 | COARFO03a |
Dirty Woman Creek | 39.081775 | -104.876332 | COARFO04b |
Beaver Creek | 39.048472 | -104.867435 | COARFO03a |
Jackson Creek | 39.043241 | -104.854152 | COARFO04a |
Smith Creek | 39.025423 | -104.830462 | COARFO04b |
Monument Branch | 39.013973 | -104.823260 | COARFO04a |
Black Squirrel Creek | 39.000318 | -104.810446 | COARFO04b |
Elkhorn Springs | 38.981928 | -104.808412 | COARFO04a |
Kettle Creek | 38.976090 | -104.798813 | COARFO04c |
Unnamed | 38.948613 | -104.829623 | COARFO04b |
Pine Creek | 38.961800 | -104.799435 | COARFO04a |
South Pine Creek | 38.937662 | -104.816766 | COARFO04a |
Cottonwood Creek | 38.927132 | -104.814858 | COARFO04b |
Dry Creek | 38.926631 | -104.816170 | COARFO04b |
North Rockrimmon Creek | 38.915555 | -104.826052 | COARFO04c |
South Rockrimmon Creek | 38.909113 | -104.827132 | COARFO04a |
Templeton Gap North Tributary | 38.906605 | -104.815082 | COARFO04a |
Templeton Gap Floodway | 38.888866 | -104.824333 | COARFO04a |
Douglas Creek | 38.888680 | -104.826417 | COARFO04a |
South Douglas Creek | 38.882480 | -104.829076 | COARFO04a |
Mesa Creek | 38.856371 | -104.832046 | COARFO04c |
Bear Creek | 38.822378 | -104.840974 | COARFO03a |
Cheyenne Creek | 38.813118 | -104.823434 | COARFO03a |
Shooks Run | 38.816411 | -104.817649 | COARFO04e |
Spring Run | 38.799946 | -104.820992 | COARFO04e |
Spring Creek | 38.808650 | -104.795141 | COARFO04e |
Sand Creek (near Co. Springs) | 38.782008 | -104.778801 | COARFO04e |
Fishers Canyon | 38.776189 | -104.779734 | COARFO04e |
Neal Ranch | 38.754761 | -104.759366 | COARFO04d |
Unnamed | 38.725284 | -104.727502 | COARFO04d |
Crews Gulch | 38.719094 | -104.726343 | COARFO04d |
Unnamed above Fort Carson boundary | 38.694465 | -104.738735 | COARFO04d |
Unnamed below Fort Carson boundary | 38.679695 | -104.712972 | COARFO05b |
Jimmy Camp Creek above Old Pueblo Road | 38.673200 | -104.696739 | COARFO05a |
Jimmy Camp Creek below Old Pueblo Road | 38.672228 | -104.698486 | COARFO05b |
Little Fountain/Rock Creek above Highway 115 | 38.676901 (LFC) 38.698881 (RC) | -104.849436 -104.830406 | COARFO03a |
Little Fountain/Rock Creek below Highway 115 | 38.614494 | -104.674764 | COARFO04e |
Unnamed | 38.597077 | -104.676750 | COARFO04d |
Unnamed 2 | 38.602678 | -104.660838 | COARFO04d |
Unnamed | 38.585843 | -104.669591 | COARFO04d |
Unnamed | 38.566210 | -104.650835 | COARFO04e |
Williams Creek | 38.564539 | -104.625856 | COARFO05a |
Sand Creek (near Wigwam) | 38.535376 | -104.627254 | COARFO04e |
Unnamed | 38.528773 | -104.646758 | COARFO04e |
Unnamed | 38.511449 | -104.629547 | COARFO04e |
Unnamed | 38.488879 | -104.615683 | COARFO04e |
Unnamed | 38.480893 | -104.605607 | COARFO04e |
Unnamed | 38.489335 | -104.590919 | COARFO04e |
Unnamed | 38.445576 | -104.606713 | COARFO04e |
Unnamed | 38.436593 | -104.589458 | COARFO04e |
Unnamed | 38.422393 | -104.591365 | COARFO04e |
Unnamed | 38.421339 | -104.606992 | COARFO04e |
Unnamed | 38.409289 | -104.588270 | COARFO04e |
Steel Hollow | 38.407341 | -104.611280 | COARFO04e |
Unnamed | 38.400587 | -104.597455 | COARFO04e |
Unnamed | 38.395210 | -104.598914 | COARFO04e |
Unnamed | 38.387537 | -104.614172 | COARFO04e |
Unnamed | 38.380028 | -104.606847 | COARFO04e |
Porter Creek | 38.372749 | -104.616156 | COARFO04e |
Gnat Hollow | 38.361287 | -104.617953 | COARFO04e |
Unnamed | 38.364057 | -104.610592 | COARFO04e |
Unnamed | 38.355674 | -104.609416 | COARFO04e |
Unnamed | 38.344821 | -104.609092 | COARFO04e |
Unnamed | 38.345192 | -104.616245 | COARFO04e |
Unnamed | 38.320417 | -104.604750 | COARFO04e |
Unnamed | 38.312846 | -104.590524 | COARFO04d |
Unnamed | 38.317828 | -104.620189 | COARFO04d |
The following edits were made to segment descriptions to improve clarity and correct typographical errors:
* The formatting of the tables in Appendix 32-1 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.
* Upper Arkansas segments 2a and 13: The nutrient note was added to correct a previous omission.
* Upper Arkansas Segment 20b: Total phosphorus and chlorophyll standards and a nutrient note was added to correct a previous omission.
* The qualified discharger table at 32.5(4) was updated to accurately reflect the location of Monarch Mtn Lodge and Powder Monarch LLC on Upper Arkansas Segment 13.
* Existing site-specific temperature standards for Upper Arkansas segments 4, 14c, 20a, 20b, 30 and 35, Middle Arkansas segments 20 and 26, and Lower Arkansas Segment 1a were reformatted in the tables to provide clarity and consistency.
* Existing silver standards were updated to remove the trout qualifier on Lower Arkansas segments 10, 12 and 19, and Middle Arkansas segments 3, 9, 18a, 18b, 21 and 28.
* Fountain Creek Segment 5: Coordinates were added to the segment description.
* Lower Arkansas Segment 15: Commas were modified for clarity.
* Middle Arkansas segments 5b and 6a: Coordinates were added to the diversion for clarity.
* Middle Arkansas Segment 18a: Punctuation was modified for clarity.
* Middle Arkansas Segment 26: Punctuation was modified for clarity.
* Upper Arkansas segments 4a and 4b: Coordinates were added to the Highway 115 bridge.
* Upper Arkansas Segment 14a: Rush Creek was removed from the segment description, as this stream (source at 38.185078, -104.976083) is already correctly located in Middle Arkansas Segment 18b.
* Upper Arkansas Segment 15b: Coordinates were added to County Road 92.
* Upper Arkansas Segment 25: Section Township and range were replaced with coordinates in segment description.
* Upper Arkansas segments 27 and 39: Coordinates were added to the mouth of Phantom Canyon.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-32.61