5 Colo. Code Regs. § 1002-35.21
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 renumbering and/or creation of new segments in tine basin was made due to information winicin sinowed tinat:
Upper Gunnison River Basin segment 29b was created for Lake San Cristobal.
Uncompahgre River Basin segment 3b was created for Ridgway Reservoir.
Waters within the Redwell Basin, tributary to Oh-Be-Joyful Creek, were moved to Upper
Gunnison River Basin segment 10 to maintain water quality relationships of Oh-Be-Joyful Creek basin below the wilderness area boundary.
Red Mountain Creek tributaries Corkscrew and Champion basins were added to Uncompahgre
River Basin segment 6b (Red Mountain Creek) to maintain water quality relationships of the drainage.
Pryor Creek and West Fork Spring Creek were added to Uncompahgre River Basin segment 13
because of similar water quality and uses with the existing segment.
San Miguel River Basin segment 4 was resegmented into segments 4a and 4b.
Lower Dolores River Basin segment 3b was created for the waters within the Sinbad Valley (Salt Creek).
The Commission reviewed information regarding existing aquatic communities. The Aquatic Life Use classifications were changed for several segments based on the presence of Colorado Cutthroat Trout, current temperature data and deleted for one segment. The following changes were made:
Aquatic Life Use changed from Cold 2 to Cold 1 to reflect the presence of Colorado Cutthroat Trout, a species of special concern:
Upper Gunnison River Basin segment 17 Uncompahgre River Basin segment 13
Aquatic Life Use changed from Cold to Warm based on temperature data and aquatic life species present:
Lower Gunnison River Basin segment 2
Deletion of the Aquatic Life Use based on water quality and aquatic life sampling and the preparation of a use attainability analysis:
Uncompahgre River Basin segment 6b.
As part of the Basic Standards hearing of 2005, recreation classifications were revised into four new classifications. The Commission reviewed the previous segment classifications (la, lb and 2) and determined the appropriate new classification based on classification criteria presented as part of the Basic Standards Hearing, use attainability analyses or other basis. In addition, during the 2005 Basic Standards Hearing, the transition from the use of the fecal coliform standard to an E. coli standard was completed. Fecal coliform criteria were deleted from the numeric standards.
Based on the information tinat sinowed existing primary contact recreation use is in place in at least a portion of the segment, the Commission changed the following segments from Recreation Classla to Recreation Class E with a 126/100 ml E. coli standard:
Upper Gunnison River Basin segments: 1,2, 3,4, 5, 6b, 7, 8, 9, 10, 11, 12, 13a, 14,20,22,25,
29a, 29b, 30, 31 and 32
North Fork of the Gunnison River Basin segments: 1, 2, 4 and 7
Uncompahgre River Basin segments: 1, 3a, 4a, 4c, 5, 6b, 13, 14 and 15b
Lower Gunnison River Basin segments: 1, 2, 3, 4b, 5, 6, 8, 10, 11a, lib and 13
San Miguel River Basin segments: 1, 2, 3a, 3b, 4, 5, 6a, 6b, 7a, 7b, 8, 9, 10, 11 and 12
Lower Dolores River Basin segments: 1, 2, 3a, 4 and 5
The following segments were converted from Recreation Class lb to Recreation Class P with a 205/100 ml E. coli standard:
Upper Gunnison River Basin segment13b
North Fork of the Gunnison River segments 5 and 6
Uncompahgre River Basin segment 9
Lower Gunnison River Basin segments 7 and 12
The following segment was converted from Recreation Class 1 to Recreation Class U:
Upper Gunnison River Basin segment 6a
The following segments were converted from Recreation Class 2 to Recreation Class U. These segments include:
Upper Gunnison River Basin segments 16, 17, 18, 19, 21, 23, 24 and 26. The E. co/; standard for these segments were 126/100 ml and were not changed.
Upper Gunnison River Basin segment 15 had a fecal coliform standard of 2000/100 ml and was changed to be consistent with the use at 126/100ml E. coli.
Based on review of existing Use Attainability Analyses showing that primary contact recreation is not attainable, the following segments were converted to Recreation Class N classification with 630/100 ml E co/; standard:
Uncompahgre River Basin segments 2, 4b, 6a, 7, 8, 12 and 15a Lower Gunnison River Basin segment 4a
The following segments with seasonal Recreation Class la/Recreation Class 2 classification were converted to Class E/Class N:
North Fork of the Gunnison River Basin segment: 3 Lower Gunnison River Basin segment 9
The following segment with seasonal Recreation Class la/Recreation Class lb classification was converted to Class E/Class P:
Uncompahgre River Basin segment 10
The following segment with seasonal Recreation Class 1 b/Recreation Class 2 classification was converted to Class P/Class N:
Uncompahgre River Basin segment 11
Based on review of information regarding the location of public water supplies, a water supply classification and standards were added Uncompahgre River Basin segment 3a.
Numeric Standards to protect Agricultural Uses were adopted for the following segments:
Uncompahgre River Basin segment: 6a
San Miguel River Basin segments: 3a, 6a and 6b
Outstanding Waters Designation: Based on evidence that shows the water quality meets the requirements of 31.8(2)a, the OW designation was added to the following segment: Upper Gunnison River Basin segment 1 was modified to incorporate the waters within the Powderhorn Wilderness Area.
Decoupling Cold 2 and UP: As part of the Basic Standards hearing of 2005, the Commission eliminated the direct linkage between cold-water aquatic life class 2 and the use-protected designation. Therefore, all cold-water aquatic life class 2 segments that are use-protected were reviewed to determine if that designation is still warranted. The following segments are now reviewable:
Upper Gunnison River Basin segments: 6a, 13a, 13b, 15 and 17 Uncompahgre River Basin segments: 6a, 7, 8, 9, 10, and 13 Lower Gunnison River Basin segment: 7. San Miguel River Basin segment: 12.
Decoupling Aquatic Life Warm 2 and UP Also as part of the Basic Standards hearing of 2005, the Commission decided that the presence of a warm water class 2 classification would still be a presumptive basis for applying a use-protected designation; however, that presumption can be overcome if there is data showing that the water is of high quality. Therefore, the Commission reviewed all warm water class 2 segments to determine if the use protected designation is still warranted. No Regulation 35 aquatic life warm 2 segments were changed from use-protected to reviewable.
Based on water quality sampling data and aquatic life information, aquatic life numeric standards were added to Upper Gunnison River Basin segment 6a.
There are several segments in the Basins that are assigned standards based on existing ambient water quality. Ambient standards are adopted where natural or irreversible man-induced conditions result in exceedances of table value standards. The Commission reviewed the information that is the basis for these standards as well as any new information that would indicate whether they are still appropriate, need to be modified, or should be dropped. The Commission did not adopt any changes to the ambient quality-based standards.
At tine June 2005 Basic Standards rulemaking, tine Commission adopted tine 1999 Update of Ambient Water Quality Criteria for Ammonia (US EPA, Office of Water, EPA-822-R-99-014, December 1999) as tine numeric ammonia criteria for Colorado. These new criteria are in the form of total ammonia rather than un-ionized ammonia. The Commission modified the ammonia equations in 35.6(3) and footnotes to conform to Regulation No. 31. In cases where dischargers need time beyond one permit term to assure compliance with new permit limits, temporary modifications have been adopted. These are listed below in the temporary modification section.
New Table Value Standards: As part of the Basic Standards hearing of 2005, new zinc and cadmium table values were adopted. The acute and chronic zinc and cadmium equations in 35.6(3) were modified to conform to Regulation No. 31.
Site-Specific Zinc Standards for Sculpin: In low hardness situations (hardness below 113 mg/l CaCOs) the new zinc equation is not protective of sculpin, a native west-slope fish species. The Commission adopted sculpin-specific zinc equation as site-specific standards for the following segments that are inhabited by sculpin that also have low hardness:
Upper Gunnison River Basin segments: 2, 3, 4, 6a, 7, 15, 16, 19, 22, 23, 29a, 30 and 32 North Fork of the Gunnison River Basin segments: 1, 2 and 4 Uncompahgre River Basin segments: 5 and 6a Lower Gunnison River Basin segment: 8 San Miguel River Basin segments: 1 and 2
For arsenic, each use (except recreation) has a different arsenic ("As") value, including Fish Ingestion (Fl) and Water Plus Fish (W+F). In different combinations of uses, different values become the most limiting. In order to eliminate the confusion, the Commission added the operative value to the individual segments. The following matrix displays the most limiting arsenic criteria.
Most Limiting Arsenic Criteria Depending on the Possible Combinations of Uses and Qualifiers
If the Use Classifications were: | These Arsenic Standards were Applied (dissolved unless otherwise noted) |
Class 1 aquatic life, water supply | As(ac) = 340, As(ch) = 0.02 (tree) |
Class 2 aquatic life (water + fish standards), water supply | As(ac) = 340, As(ch) = 0.02(trec) |
Class 2 aquatic life (no fish ingestion standards), water supply | As(ac) = 340, As(ch) = 0.02 - lO(trec) |
Class 1 aquatic life | As(ac) = 340, As(ch) = 7.6(trec) |
Class 2 aquatic life (fish ingestion standards) | As(ac) = 340, As(ch) = 7.6(trec) |
Class 2 aquatic life (no fish ingestion standards), agriculture | As(ac) = 340, As(ch) = 100 (tree) |
Agriculture only | As(ch) = 100 (tree) |
Water supply only | As(ch) = 0.02 - lO(trec) |
Uranium standards were added for segments that flow near uranium-bearing rock formations. The Uranium standard was added to:
Lower Gunnison River Basin segments: 5 and 6
San Miguel River Basin segments: 5 and 12
Lower Dolores River Basin segments: 1, 2, 3a, 4 and 5
All temporary modifications were re-examined to determine whether to delete the temporary modification or to extend them, either as existing or with modifications of the numeric standards. Because of the June 2005 changes to Regulation No. 31, temporary modifications were not automatically extended if non-attainment persisted.
The following segments had temporary modifications which are being removed because current ambient conditions are meeting the underlying standards:
Uncompahgre River Basin segment 4a (Selenium).
Temporary modifications were removed for the following segments though the water quality standards were not being met.
Upper Gunnison River Basin segment: 10
Lower Gunnison River Basin segment: 9
San Miguel River Basin segments: 6a, 6b and 7b.
The following segments have new or extended temporary modifications. As specified in 61.8(2)(c)(iii) (the Permit Rules, Regulation No 61), where a temporary modification has been adopted, limits in permits are to be set based on the temporary modification and the provision strictly limiting the loading from the facility does not apply. These temporary modifications will be subject to review and rulemaking for the two years before their scheduled expiration in order to track progress towards the full attainment of water body standards and uses.
Upper Gunnison River Basin segment 8: Cd(ch) = 0.4, expiration date of 12/31/2011. This temporary modification is intended to allow the Town of Crested Butte Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Upper Gunnison River Basin segment 12: Cd(ch) = 2.3, Zn(ch)= 518, expiration date of 12/31/2011. This temporary modification is intended to allow the Keystone Mine adequate time to assess any potential changes to its discharge permit. The need for these temporary modifications will be reviewed in 2009 and 2010.
Upper Gunnison River Basin segment 16: Zn(ch) = 11.9, expiration date of 12/31/2011. This temporary modification is intended to allow the North Elk Meadows HOA Wastewater Treatment Facility adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
North Fork of the Gunnison River Basin segment 3: Se(ch) = 5.7, expiration date of 12/31/2011. This temporary modification is intended to allow multiple dischargers adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
North Fork of the Gunnison River Basin segment 5: Se(ch) = existing ambient quality, expiration date of 12/31/2011. This temporary modification is intended to allow multiple dischargers adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
North Fork of the Gunnison River Basin segment 6b: Fe(ch)(Trec)= existing ambient quality, Se(ch) = existing ambient quality, expiration date of 12/31/2011. This temporary modification is intended to allow multiple dischargers adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahqre River Basin segment 3a: Cd(ch)=1.1, Fe(Trec) = 1673, expiration date of 12/31/2011. This temporary modification is intended to allow multiple dischargers adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahgre River Basin segment 4a: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the City of Montrose and the West Montrose Sanitation District Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahgre River Basin segment 4b: Se(ch) = 20, expiration date of 12/31/2011. This temporary modification is intended to allow multiple dischargers adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahqre River Basin segment 4b: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the Town of Olathe Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahgre River Basin segment 4c: Se(ch) = 20, expiration date of 12/31/2011. This temporary modification is intended to allow the Gunnison Basin Selenium Task Force and the Colorado River Water Conservation District adequate time to assess any potential changes. This need for this temporary modification will be reviewed in 2009 and 2010.
Uncompahgre River Basin segment 12: Se(ch) = existing ambient quality, expiration date of 12/31/2011. This temporary modification is intended to allow the Gunnison Valley Selenium Task Force adequate time to assess any potential changes. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 2: Se(ch) = 8.4, expiration date of 12/31/2011. This temporary modification is intended to allow the Gunnison Valley Selenium Task Force adequate time to assess any potential changes. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 2: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the City of Delta Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 4a: Se(ch) = existing ambient quality, expiration date of 12/31/2011. This temporary modification is intended to allow the Gunnison Valley Selenium Task Force adequate time to assess any potential changes. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 4a: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the Town of Cedaredge Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 4b: Se(cln) = existing ambient quality, expiration date of 12/31/2011. TInis temporary modification is intended to allow the Gunnison Valley Selenium Task Force adequate time to assess any potential changes. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Gunnison River Basin segment 7: Se(ch) = 9.3 and Fe(ch)(Trec)= 2650, expiration date of 12/31/2011. This temporary modification is intended to allow the Gunnison Valley Selenium Task Force adequate time to assess any potential changes and to allow dischargers any potential changes to their permits. This need for this temporary modification will be reviewed in 2009 and 2010.
San Miguel River Basin segment 2: Cd(ch) = 0.6, expiration date of 12/31/2011. This temporary modification is intended to allow the Telluride Water Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
San Miguel River Basin segment 3b: Cd(ch) = 0.7, Zn(ch) = 198 expiration date of 12/31/2011. This temporary modification is intended to allow the Telluride Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
San Miguel River Basin segment 4b: Temperature = 26.3°C MWAT below the mixing zone of the Tri-State Generation and Transmission Nucia Power Station from 6/1 to 9/30, expiration date of 12/31/2011. This temporary modification is intended to allow Tri-State Generation and Transmission adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010. Further discussion of this temporary modification is found in Section N. Other Site-Specific Revions.
San Miguel River Basin segment 5: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the Naturita Wastewater Treatment Plant adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
Lower Dolores River Basin segment 2: NHs (ac/ch)=TVS(old) expiration date of 12/31/2011. This temporary modification is intended to allow the Southwest Mesa County Rural Public Improvement District (Gateway) adequate time to assess any potential changes to its discharge permit. This need for this temporary modification will be reviewed in 2009 and 2010.
For segments with multiple streams or "all tributary" segments the Division in setting temporary modifications should use the narrative statement "existing ambient quality" to avoid confusion with multiple sampling locations.
The Commission adopted a temporary modification for temperature in the lower portion of Segment 4b of 26.3 °C, as a maximum weekly average temperature ("MWAT") from 6/1 to 9/30, to expire 12/31/2011. This temporary modification is adopted pursuant to Regulation 31.7(3)(a)(iii) because there is significant uncertainty regarding the appropriate long term underlying temperature standard.
There is uncertainty associated with the underlying standard in the lower portion of Segment 4b. This portion of the stream is a transition between cold and warm water. Based on the existing Basic Standards, the Commission adopted a temporary modification of 26.3°C and an underlying standard of 20°C, which raises uncertainty as to the appropriate underlying standard that should be applied to protect the aquatic life community.
A temporary modification has been adopted to provide time to address this uncertainty and recommend appropriate standards for these water bodies. During the effective period of this temporary modification, Tri-State, in coordination and collaboration with the Division and CDOW, will conduct cost-effective studies designed to address whether Tri-State's discharge has an adverse impact on the aquatic community.
The numeric value of this temporary modification was calculated using a mass-balance approach with the following assumptions: The upstream low-flow was estimated as the 7E3 generated from the amount of water measured at the Brooks Bridge minus the Tri-State cooling water withdrawal. The upstream temperature was an adjusted MWAT of 24°C which corresponds to the modeled MWAT of the San Miguel at the point of discharge. The discharge characteristics were the Power Station design flow and an effluent temperature of 30°C max.
It is the Commission's intent to preserve the status quo for Tri-State's discharge for the duration of the temporary modification. In a stipulation between Tri-State and the Division, Tri-State committed that it will not alter operations on a year round basis in a manner that would adversely affect effluent temperature for the duration of the temporary modification. The Division agreed that it will maintain the existing daily maximum permit limit of 30°C at the compliance point on a year round basis.
The Commission corrected several typographical and spelling errors, and clarified segment descriptions.
The reference to "Water+Fish Organics" was corrected to "Water+Fish Standards" to incorporate the appropriate standards from both the organics table and the metal parameter table in Regulation No. 31.
The Water and Fish Organics qualifier on the Uncompahgre River Basin segment 9 was corrected to Fish Ingestion since the segment does not have a Water Supply use.
The segment description for Upper Gunnison River Basin segment 2 was changed to reflect the incorporation of the Oh-Be-Joyful Wilderness Area into the Raggeds Wilderness Area.
The segment description for Upper Gunnison River Basin segment 4 was changed to include the Taylor Park Reservoir.
The segment description for Upper Gunnison River Basin segment 26 was changed to include the Silver Jack Reservoir.
The segment description for San Miguel River Basin segment 2 was changed to include the Trout Lake.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-35.21