Colorado department of public health and environment
WATER QUALITY CONTROL COMMISSION
5 ccr 1002-37
REGULATION NO.  37
CLASSIFICATIONS AND NUMERIC STANDARDS
FOR
LOWER COLORADO RIVER BASIN 
37.1	AUTHORITY
These regulations are promulgated pursuant to section 25-8-101 et seq. C.R.S., as amended, and in particular, 25-8-203 and 25-8-204.
37.2	PURPOSE
These regulations establish classifications and numeric standards for the Colorado River Basin, including all tributaries and standing bodies of water.  This includes all or parts of Garfield, Mesa, Rio Blanco, Moffat and Routt Counties. The classifications identify the actual beneficial uses of the water.  The numeric standards are assigned to determine the allowable concentrations of various parameters.  Discharge permits will be issued by the Water Quality Control Division to comply with basic, narrative, and numeric standards and control regulations so that all discharges to waters of the state protect the classified uses.  (See Regulation No. 31, section 31.14).  It is intended that these and all other stream classifications and numeric standards be used in conjunction with and be an integral part of Regulation No. 31 Basic Standards and Methodologies for Surface Water.
37.3	INTRODUCTION
These regulations and tables present the classifications and numeric standards assigned to stream segments listed in the attached tables (see section 37.6).  As additional stream segments are classified and numeric standards for designated parameters are assigned for this drainage system, they will be added to or replace the numeric standards in the tables in section 37.6.  Any additions or revisions of classifications or numeric standards can be accomplished only after public hearing by the Commission and proper consideration of evidence and testimony as specified by the statute and the "basic regulations".
37.4	DEFINITIONS
See the Colorado Water Quality Control Act and the codified water quality regulations for definitions.
37.5	BASIC STANDARDS
(1)	TEMPERATURE
All waters of the Colorado River Basin are subject to the following standard for temperature.  (Discharges regulated by permits, which are within the permit limitations, shall not be subject to enforcement proceedings under this standard).  Temperature shall maintain a normal pattern of diurnal and seasonal fluctuations with no abrupt changes and shall have no increase in temperature of a magnitude, rate, and duration deemed deleterious to the resident aquatic life.  This standard shall not be interpreted or applied in a manner inconsistent with section 25-8-104, C.R.S.  
(2)	QUALIFIERS
See Basic Standards and Methodologies for Surface Water for a listing of organic standards at 31.11 and metal standards found at 31.16 Table III.  The column in the tables headed “Water + Fish” are presumptively applied to all aquatic life class 1 streams which also have a water supply classification, and are applied to aquatic life class 2 streams which also have a water supply classification, on a case-by-case basis as shown in the Tables 37.6.  The column in the tables at 31.11 headed “Fish Ingestion” is presumptively applied to all aquatic life class 1 streams which do not have a water supply classification, and are applied to aquatic life class 2 streams which do not have a water supply classification, on a case-by-case basis as shown in Tables 37.6.
(3)	URANIUM
(a)	All waters of the Lower Colorado River Basin, are subject to the following basic standard for uranium, unless otherwise specified by a water quality standard applicable to a particular segment.  However, discharges of uranium regulated by permits which are within these permit limitations shall not be a basis for enforcement proceedings under this basic standard.
(b)	Uranium level in surface waters shall be maintained at the lowest practicable level.
(c)	In no case shall uranium levels in waters assigned a water supply classification be increased by any cause attributable to municipal, industrial, or agricultural discharges so as to exceed 16.8-30 ug/l or naturally-occurring concentrations (as determined by the State of Colorado), whichever is greater. 
(i)	The first number in the 16.8-30 ug/l range is a strictly health-based value, based on the Commission’s established methodology for human health-based standards. The second number in the range is a maximum contaminant level, established under the federal Safe Drinking Water Act that has been determined to be an acceptable level of this chemical in public water supplies, taking treatability and laboratory detection limits into account. Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range. Water bodies will be considered in attainment of this standard, and not included on the Section 303(d) List, so long as the existing ambient quality does not exceed the second number in the range.
(4)	 NUTRIENTS
Prior to May 31, 2022, interim nutrient values will be considered for adoption only in the limited circumstances defined at 31.17(e).  These circumstances include headwaters, Direct Use Water Supply (DUWS) Lakes and Reservoirs, and other special circumstances determined by the Commission.  Additionally, prior to May 31, 2017, only total phosphorus and chlorophyll a will be considered for adoption.  After May 31, 2017, total nitrogen will be considered for adoption per the circumstances outlined in 31.17(e).
Prior to May 31, 2022, nutrient criteria will be adopted for headwaters on a segment by segment basis for the Lower Colorado Basin.  Moreover, pursuant to 31.17(e) nutrient standards will only be 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 85 effluent limits and discharging prior to May 31, 2012. The following is a list 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 85 effluent limits and discharging prior to May 31, 2012 in the Lower Colorado Basin:  

Segment	Permittee	Facility name	Permit No.	
COLCLY02	Craig City of	CRAIG WWTF	 CO0040037	
COLCWH07	Whiteriver RV LLC	WHITERIVER RV SANITATION WWTF	COG588048	
COLCWH07	Meeker Sanitation District	MEEKER SANITATION DISTRICT	CO0047139	
COLCWH13b	Shell Frontier Oil & Gas Inc	CORRAL GULCH WWTF	CO0048859	
COLCWH21	Rangely Town of	RANGELY WWTF	CO0000010	
COLCLC01	Rifle City of	RIFLE REGIONAL WW RECLAMATION FACILITY	CO0048151	
COLCLC01	Wastewater Treatment Service LLC	WASTE WATER TREATMENT SERVICES WWTF	COG589110	
COLCLC01	Silt Town of	SILT TOWN OF	COG588046	
COLCLC01	West Glenwood Springs SD	WEST GLENWOOD SPRINGS SD	COG588008	
COLCLC01	Glenwood Springs City of	GLENWOOD SPRINGS REGIONAL WWTF	CO0048852	
COLCLC01	Talbott Enterprises Inc	TALBOTT ENTERPRISES INC	COG588061	
COLCLC01	New Castle Town of	NEW CASTLE WWTF	COG588062	
COLCLC01	Riverbend Water and Sewer Company	RIVERBEND SUBDIVISION	COG588006	
COLCLC02a	Colorado Retail Ventures Services LLC	CAMEO EAGLE TRAVEL CENTER	CO0048847	
COLCLC02a	DeBeque Town of	DEBEQUE TOWN OF	CO0048135	
COLCLC02a	Battlement Mesa Metro Dist	BATTLEMENT MESA METRO DIST WWTF	COG589086	
COLCLC02b	Clifton Sanitation District	CLIFTON SANITATION DISTRICT	CO0033791	
COLCLC02b	Palisade Town of	PALISADE WWTF	CO0000012	
COLCLC03	Fruita City of	FRUITA WASTEWATER RECLAMATION FACILITY	CO0048854	
COLCLC04e	Tri-State Generation & Transmission Assoc Inc	Rifle Station	CO0042447	
COLCLC07a	Weiss & Associates	CANYON CREEK ESTATES WWTF	COG588081	
COLCLC13b	Mesa Co/Grand Junction City of	PERSIGO WWTF	CO0040053	
COLCLC15a	Grand Mesa Metro Dist 2	GRANDE MESA METRO DIST 2	CO0023485	
COLCLC15a	Mesa WSD	MESA WSD	CO0048143	
COLCLC15c	Collbran Town of	VALLEYWIDE SEWERAGE SYSTEM	CO0040487	
Prior to May 31, 2022:
•	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 footnote “C” was added to the total phosphorus and chlorophyll a standards in these segments. The footnote references the table of qualified facilities at 37.5(4). 
•	For segments located entirely below these facilities, nutrient standards do not apply.
A footnote “B” was added to the total phosphorus and chlorophyll a standards in lakes segments as nutrients standards apply only to lakes and reservoirs larger than 25 acres surface area. 
37.6	TABLES
(1)	Introduction
The numeric standards for various parameters in the attached tables were assigned by the Commission after a careful analysis of the data presented on actual stream conditions and on actual and potential water uses.
Numeric standards are not assigned for all parameters listed in the tables attached to Regulation No. 31.  If additional numeric standards are found to be needed during future periodic reviews, they can be assigned by following the proper hearing procedures.
(2)	Abbreviations:
(a)	The following abbreviations are used in the attached tables:
ac	=	acute (1-day)
Ag	=	silver
Al	=	aluminum
As	=	arsenic
B	=	boron
Ba	=	barium
Be	=	beryllium
oC	=	degrees celsius
Cd	=	cadmium
ch	=	chronic (30-day)
Chla	=	Chlorophyll a
CL	=	cold lake temperature tier
Cl	=	chloride
CLL	=	cold large lake temperature tier
Cl2	=	residual chlorine
CN	=	free cyanide
CrIII	=	trivalent chromium
CrVI	=	hexavalent chromium
CS-I	=	cold stream temperature tier one
CS-II	=	cold stream temperature tier two
Cu	=	copper
dis	=	dissolved
D.O.	=	dissolved oxygen
DM	=	daily maximum
DUWS	=	direct use water supply
E.Coli	=	escherichia coli
Fe	=	iron
Hg	=	mercury
mg/l	=	milligrams per liter
ml	=	milliliters
Mn	=	manganese
Mo	=	molybdenum
MWAT	=	maximum weekly average temperature
NH3	=	ammonia as N(nitrogen)
Ni	=	nickel
NO2	=	nitrite as N (nitrogen)
NO3	=	nitrate as N (nitrogen)
OW	=	outstanding waters
P	=	phosphorus
Pb	=	lead
S	=	sulfide as undissociated H2S (hydrogen sulfide)
Sb	=	antimony
sc	=	sculpin
Se	=	selenium
SO4	=	sulfate
sp	=	spawning
T	=	temperature 
Tot	=	total
Tl	=	thallium
tr	=	trout
Trec	=	total recoverable
TVS	=	table value standard
U	=	uranium
ug/l	=	micrograms per liter
UP	=	use-protected
WAT	=	weekly average temperature
WL	=	warm lake temperature tier
WS	=	water supply
WS-I	=	warm stream temperature tier one
WS-II	=	warm stream temperature tier two
WS-III	=	warm stream temperature tier three
WS-IV	=	warm stream temperature tier four
Zn	=	zinc
(b)	In addition, the following abbreviations were used:
 	Fe(ch)		=	WS(dis)
 	Mn(ch)		=	WS(dis)
 	SO4		=	WS
These abbreviations mean:  For all surface waters with an actual water supply use, the less restrictive of the following two options shall apply as numerical standards, as specified in the Basic Standards and Methodologies at 31.16 Table II and III:
(i)	existing quality as of January 1, 2000; or
(ii)		Iron		=	300 ug/l (dissolved)
	Manganese	=	50  ug/l (dissolved)
	SO4		=	250 mg/l
For all surface waters with a “water supply” classification that are not in actual use as a water supply, no water supply standards are applied for iron, manganese or sulfate, unless the Commission determines as the result of a site-specific rulemaking hearing that such standards are appropriate.
(c)	As used in the Temporary Modifications and Qualifiers column of the tables in 37.6(5), the term “type A” refers to a Temporary Modification adopted pursuant to subsection 31.7(3)(a)(ii)(A) of the Basic Standards and Methodologies for Surface Water (i.e., “there is significant uncertainty regarding the water quality standard necessary to protect current and/or future use”).  As used in the Temporary Modifications and Qualifiers column of the tables in 37.6(5), the term “type B” refers to a Temporary Modification adopted pursuant to subsection 31.7(3)(a)(ii)(B) of the Basic Standards and Methodologies for Surface Water (i.e., “there is significant uncertainty regarding the extent to which existing quality is the result of natural or irreversible human-induced conditions”).
(d)	Temporary Modification for Water + Fish Chronic Arsenic Standard
(i)	The temporary modification for chronic arsenic standards applied to segments with an arsenic standard of 0.02 ug/l that has been set to protect the Water+Fish qualifier is listed in the temporary modification and qualifiers column as As(ch)=hybrid.
(ii)	For discharges existing on or before 6/1/2013, the temporary modification is:  As(ch)=current condition, expiring on 12/31/2021.
(iii)	For new or increased discharges commencing on or after 6/1/2013, the temporary modification is:  As(ch)=0.02-3.0 ug/l (Trec), expiring on 12/31/2021.
(a)	The first number in the range is the health-based water quality standard previously adopted by the Commission for the segment.
(b)	The second number in the range is a technology based value established by the Commission for the purpose of this temporary modification.
(c)	Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range.
(3)	Table Value Standards
In certain instances in the attached tables, the designation "TVS" is used to indicate that for a particular parameter a "table value standard" has been adopted.  This designation refers to numerical criteria set forth in the Basic Standards and Methodologies for Surface Water.  The criteria for which the TVS are applicable are on the following table.
TABLE VALUE STANDARDS
(Concentrations in ug/l unless noted)
PARAMETER(1)	TABLE VALUE STANDARDS (2)(3)	
Aluminum (Trec)
	Acute = e(1.3695[ln(hardness)]+1.8308)
pH equal to or greater than 7.0
          Chronic=e(1.3695[ln(hardness)]-0.1158)
pH less than 7.0
          Chronic= e(1.3695[ln(hardness)]-0.1158) or 87, whichever is more stringent	
Ammonia (4)	Cold Water = (mg/l as N)Total

	
	Warm Water = (mg/l as N)Total

	
Cadmium	Acute = (1.136672-[ln(hardness) x (0.041838)] )x e0.9151[ln(hardness)]-3.1485
Acute(Trout) = (1.136672-[ln(hardness)x (0.041838)] )x e0.9151[ln(hardness)]-3.6236
Chronic = (1.101672-[ln(hardness) x(0.041838)]) x e0.7998[ln(hardness)]-4.4451	
Chromium III(5)	Acute = e(0.819[ln(hardness)]+2.5736)
Chronic = e(0.819[ln(hardness)]+0.5340)	
Chromium VI(5)	Acute = 16
Chronic = 11	
Copper	Acute = e(0.9422[ln(hardness)]-1.7408)
Chronic = e(0.8545[ln(hardness)]-1.7428)	
Lead	Acute = (1.46203-[ln(hardness)*(0.145712)])*e(1.273[ln(hardness)]-1.46)
Chronic =(1.46203-[ln (hardness)*(0.145712)])*e(1.273[ln(hardness)]-4.705)	
Manganese	Acute = e(0.3331[ln(hardness)]+6.4676)
Chronic = e(0.3331[ln(hardness)]+5.8743)	
Nickel	Acute = e(0.846[ln(hardness)]+2.253)
Chronic = e(0.846[ln(hardness)]+0.0554)	
Selenium(6)	Acute = 18.4
Chronic = 4.6
	
Silver	Acute = ½e(1.72[ln(hardness)]-6.52)
Chronic = e(1.72[ln(hardness)]-9.06)
Chronic(Trout) = e(1.72[ln(hardness)]-10.51)	
Temperature	tempera-ture Tier	Tier Code	Species Expected to BE PRESENT	Applicable Months	Temperature Standard (oC)	
					(MWAT)	(DM)	
	Cold Stream   Tier I	CS-I	brook trout, cutthroat trout	June – Sept.	17.0	21.7	
				Oct. – May	9.0	13.0	
	Cold Stream   Tier II	CS-II	 all other cold-water species	April – Oct.	18.3	23.9	
				Nov. – March	9.0	13.0	
	Cold Lake	CL	brook trout, brown trout, cutthroat trout, lake trout, rainbow trout, Arctic grayling, sockeye salmon	April –  Dec.	17.0	21.2	
				Jan. – March	9.0	13.0	
	Cold Large    Lake (>100)	CLL	brown trout, lake trout, rainbow trout	April –  Dec.	18.3	23.8	
				Jan. – March	9.0	13.0	
	Warm Stream Tier I	WS-I	common shiner, Johnny darter, orangethroat darter	March – Nov.	24.2	29.0	
				Dec. – Feb.	12.1	14.5	
	Warm Stream Tier II	WS-II	brook stickleback, central stoneroller, creek chub, longnose dace, Northern redbelly dace, finescale dace, razorback sucker, white sucker 	March – Nov.	27.5	28.6	
				Dec. – Feb.	13.8	14.3	
	Warm Stream Tier III	WS-III	all other warm-water Species	March – Nov.	28.7	31.8	
				Dec. – Feb.	14.3	15.9	
	Warm Lakes	WL	yellow perch, walleye, pumpkinseed, smallmouth bass, striped bass, white bass, largemouth bass, bluegill, spottail shiner, Northern pike, tiger muskellunge, black crappie, common carp, gizzard shad, sauger, white crappie, wiper	April – Dec.	26.3	29.5	
				Jan. – March	13.2	14.8	
Uranium	Acute = e(1.1021[ln(hardness)]+2.7088)
Chronic = e(1.1021[ln(hardness)]+2.2382)	
Zinc	Acute = 0.978*e(0.9094[ln(hardness)]+0.9095)
Chronic = 0.986*e(0.9094[ln(hardness)]+0.6235)
if hardness less than 102 mg/l CaCO3
Chronic (sculpin) = e(2.140[ln(hardness)]-5.084)	

TABLE VALUE STANDARDS - FOOTNOTES 
(1) 	Metals are stated as dissolved unless otherwise specified.
(2) 	Hardness values to be used in equations are in mg/l as calcium carbonate and shall be no greater than 400 mg/L.  The hardness values used in calculating the appropriate metal standard should be based on the lower 95 per cent confidence limit of the mean hardness value at the periodic low flow criteria as determined from a regression analysis of site-specific data.  Where insufficient site-specific data exists to define the mean hardness value at the periodic low flow criteria, representative regional data shall be used to perform the regression analysis.  Where a regression analysis is not appropriate, a site-specific method should be used.  In calculating a hardness value, regression analyses should not be extrapolated past the point that data exist.
(3) 	Both acute and chronic numbers adopted as stream standards are levels not to be exceeded more than once every three years on the average.
(4)	For acute conditions the default assumption is that salmonids could be present in cold water segments and should be protected, and that salmonids do not need to be protected in warm water segments.  For chronic conditions, the default assumptions are that early life stages could be present all year in cold water segments and should be protected.  In warm water segments the default assumption is that early life stages are present and should be protected only from April 1 through August 31.  These assumptions can be modified by the Commission on a site-specific basis where appropriate evidence is submitted.
(5) 	Unless the stability of the chromium valence state in receiving waters can be clearly demonstrated, the standard for chromium should be in terms of chromium VI.  In no case can the sum of the instream levels of Hexavalent and Trivalent Chromium exceed the water supply standard of 50 ug/l total chromium in those waters classified for domestic water use.
(6)	Selenium is a bioaccumulative metal and subject to a range of toxicity values depending upon numerous site-specific variables.
(4)	Assessment Criteria
The following criteria shall be used when assessing whether a specified waterbody is in attainment of the specified standard. 
(a)	White River Segment 13b Selenium Assessment Thresholds and Locations 
Corral Gulch, Se(ch)=5.7 ug/l
Assessment location: Corral Gulch at the mouth.
Duck Creek, Se(ch)=7.9 ug/l
Assessment location: Duck Creek at the mouth.
Yellow Creek, Se(ch)=6.9 ug/l
Assessment location: Yellow Creek upstream from the confluence with Barcus Creek. 
Greasewood Creek, Se(ch)=6.0 ug/l
Assessment location: Greasewood Creek at the mouth.
(b)	White River Segment 13c Iron Assessment Threshold and Location 
Yellow Creek, Fe(ch)=1625 ug/l
Assessment location: Yellow Creek at the mouth.
. . . . 
37.33	STATEMENT OF BASIS SPECIFIC STATUTORY AUTHORITY AND PURPOSE JUNE 9, 2014 RULEMAKING; FINAL ACTION AUGUST 11, 2014 EFFECTIVE DATE DECEMBER 31, 2014
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
A.	Waterbody Segmentation
Some water bodies were moved from one segment to another segment to improve organization and/or to facilitate changes in classified uses or standards.  Some new segments were created to facilitate changes that applied only to a portion of an existing segment.  The following changes were made:
Lower Yampa/Green River Segments 3b and 3i:  Lower Johnson Gulch from the confluence with Pyeatt Gulch at CO 107 to the confluence with the Yampa River was moved from Segment 3b to a new Segment 3i to facilitate a change in the antidegradation designation.
Lower Yampa/Green River Segments 3d and 3h:  Lay Creek was moved from Segment 3d to a new Segment 3h to facilitate the adoption of a water supply use classification and standards.
Lower Yampa/Green River Segments 3c and 3e:  Wilson Creek was moved from segment 3e to segment 3c to upgrade the aquatic life use from Warm 2 to Warm 1. 
Lower Yampa/Green River Segment 6a was renumbered as segment 6.
Lower Yampa/Green River Segments 9 and 12c:  Beaver Creek was moved from Segment 9 to a a new Segment 12c to facilitate the adoption of the Outstanding Waters designation.
Lower Yampa/Green River Segments 17b and 17c:  Scandinavian Gulch was moved from Segment 17b to a new Segment 17c to facilitate adoption of standards for the protection of the aquatic life use.
Lower Yampa/Green River Segments 20 and 22d:  Conway Draw was moved from Segment 20 to a new Segment 22d to facilitate the adoption of a water supply use classification and standards.
White River Segments 4a and 4b:  Lost Creek and Snell Creek were moved from Segment 4a to Segment 4b to facilitate the adoption of the Outstanding Waters designation.
White River Segments 16a and 16b:  Some of the tributaries to Piceance Creek were moved from Segment 16a to a new Segment16b to facilitate the adoption of a water supply use classification and standards on Segement 16a. 
White River Segements 18a and 18b: Some tributaries to Piceance Creek were moved from Segment 18a to a new Segment 18b to facilitate the adoption of a water supply use classification and standards on Segment 18b. 
Lower Colorado River Segments 11b and 11c:  The water bodies in these segments were combined into one segment because the designation, uses and standards are the same.  
Lower Colorado Segments 13a and 13f:  Asbury Creek was moved from Segment 13a to a new Segment 13f to facilitate the adoption of a water supply use classification and standards. 
Lower Colorado River Segments 19 and 21:  All lakes and reservoirs tributary to Plateau Creek and within Grand Mesa National Forest were moved from Segment 19 to Segment 21 to upgrade the aquatic life use from Warm 1 to Cold 1 and to facilitate the adoption of water supply standards.  
Lower Colorado Segments 15a – 15d and 16:  Plateau Creek and its tributaries (Segment 15) were divided into 4 segments to facilitate changing the temperature tier on the new Segment 15b and the adoption of site-specific ambient temperature standards on the new Segments 15c and 15d.  The upstream boundary of Segment 16 was changed to facilitate a change in the aquatic life use and adoption of ambient temperature standards for the lower portion of Plateu Creek.    
The following segment descriptions were edited to improve clarity, correct typographical errors, and correct spelling errors:
Lower Yampa/Green River Segments: 10, 19a
White River Segments: 9a, 9b,10b, 13b
Lower Colorado River Segments: 11g, 12b, 13d
B.	Revised Aquatic-Life Use Classifications 
The Commission reviewed information regarding the existing aquatic communities. Class 2 segments with exceptionally high MMI scores, or a wide variety of fish species were upgraded from Class 2 to Class 1.  Segments that supported Colorado State Species of Special Concern such as mountain sucker or native cutthroat trout were also upgraded from Class 2 to Class 1.
The following segments or portions of segments were upgraded from Warm 2 to Warm 1:
Lower Yampa/Green River Segments: 3e (Wilson Creek moved to 3c), 22b, 22c

The following segments were upgraded from Cold 2 to Cold 1:
White River Segment: 19
Lower Colorado River Segments: 11b, 11h
Based upon evidence that the waters are expected to support cold water fisheries, portions of the following segment were upgraded from Warm 1 to Cold 1:
Lower Colorado River Segment: 21
Based upon the results of a Use Attainability Analysis that demonstrated the Cold Aquatic Life Use is not attainable, the following segment was downgraded from Cold 1 to Warm 1:
Lower Colorado River Segment: 16
C.	Recreation Classifications and Standards
Based upon evidence that portions of these segments support recreational fishing and are publicly accessible and/or accessible to families who live in the area, it was determined that there is the potential for primary contact recreation. The following segments with year-round Recreation N standards were upgraded to Recreation P:
White River Segments: 13b, 13c, 17, 18b, 20
Lower Colorado River Segment: 8
The use classification for the following segment was inadvertently changed to Recreation P in 2007, and the Recreation N use classification was restored in this rulemaking hearing:
White River Segment: 16
D.	Water Supply Use Classification and Standards
The Commission added a Water Supply use classification and standards on segments where there is a drinking water intake or where the evidence demonstrates a reasonable potential for a hydrological connection between surface water and alluvial wells used for drinking water.  The Water Supply use classification and standards were added to the following segments:
Lower Yampa/Green River Segments: 3h, 5, 6, 12a, 16, 22d
White River Segments: 13b, 14a, 16a, 18b, 20
Lower Colorado River Segments: 11h, 13f
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 were added to the following segment:
Lower Colorado River segments: 11e
E.	Agriculture Standards
Molybdenum:  In 2010, the Commission adopted a new standard for molybdenum to protect cattle from the effects of molybdenosis.  The table value adopted at that time was 300 ug/l, but included an assumption of 48 mg/day of copper supplementation to ameliorate the effects of molybdenosis.  State and local experts on cattle nutrition indicated that copper supplementation in the region is common, but is not universal.  Therefore, copper supplementation assumption was removed from the equation, which yields a standard of 160 ug/l.   The Commission expects that this value may be revised when data on the copper and molybdenum content of local forage becomes available.  The Commission also notes that in light of EPA’s disapproval of the 300 ug/l table value in the Basic Standards and Methodologies for Surface Water, the Commission intends to review this value during the next Basic Standards triennial review.
The Agriculture table value assumes that the safe copper:molybdenum ratio is 4:1. Food and water intake is based on a 273 kg (600 lb) feeder steer consuming 6.8 kg/day of dry matter and 20% of its body weight in 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 = 6.8 kg/day, [Cu] water = 0.008 mg/L, [Mo] water = 0.375 mg/L, water intake = 54.6 L/day, Cu supplementation = 0 mg/day, Mo supplementation = 0 mg/day. 
A molybdenum standard of160 ug/l was adopted for the following segments in Regulation 37 that have an Agriculture use classification, and where livestock or irrigated forage are present or expected to be present:
Lower Yampa/Green River Segments: 2, 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 4, 5, 6, 7, 8, 9, 10, 12a, 12b, 12c, 13a, 13b, 15, 16, 17a, 17c, 18, 19a, 19b, 20, 21, 22a, 22b, 22c, 22d, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33
White River Segments: 1, 3, 4a, 4b, 6, 7, 8, 9a, 9b, 9c, 9d, 10a, 10b, 11, 12, 13a, 13b, 13c, 13d, 14a, 14b, 15, 16a, 16b, 17, 18a, 18b, 19, 20, 21, 22, 23, 24, 25, 26, 27
Lower Colorado River Segments: 1, 2a, 2b, 3, 4a, 4c, 4d, 4e, 4f, 5, 6, 7a, 7b, 8, 9a, 9b, 9c, 10, 11a, 11b, 11d, 11e, 11f, 11g, 11h, 12a, 12b, 13a, 13b, 13c, 13d, 13e, 13f, 14a, 14b, 14c, 15a, 15b, 15c, 15d, 16, 17a, 17b, 18, 19, 20, 21 
The following segment does not have an Agriculture use classification or a Water Supply use classification, and a molybdenum standard was not applied:
Lower Yampa/Green River Segment: 17b
Lower Colorado River Segment: 4b 
F.	Changes to Antidegradation Designation
The Commission reviewed all Cold 2 segments that were Use-Protected to determine if that designation was still warranted.  No segments were changed to Reviewable.
The Commission reviewed all Warm 2 segments to determine if the Use-Protected designation is still warranted.  Based upon available water quality data that meet the criteria of 31.8(2), the Use-Protection designation was removed from the following segments: 
	Lower Yampa/Green River Segments: 3g, 3i, 6
The Commission adopted an Outstanding Waters (OW) designation for the following segments based on evidence presented by WildEarth Guardians showing that water quality meets the requirements of 31.8(2)(a):
	Lower Yampa/Green River Segment: 12c
	White River Segment: 4b
The presence of designated Critical Cutthroat Trout Habitat by the State of Colorado proves the exceptional recreational or ecological significance of the waters. Outreach conducted by WildEarth Guardians demonstrated support for the change in designation, the outstanding nature of these waters and the need for the additional protection of the outstanding waters designation.  The Commission understands that existing land uses, including grazing, are in place in these watersheds. The evidence demonstrates that these existing land uses are compatible with the OW designation since the current high level of water quality has been attained with these uses in place. It is the Commission’s intent that this OW designation should not be used to establish additional permit requirements for existing uses within this area.
G.	Ambient Standards
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.  In some cases, new ambient standards were adopted.  The following segments have ambient-based standards for metals that were revised:
Lower Yampa/Green River Segment: 16
White River Segments: 13b, 13c
New assessment locations were adopted for White River segments 13b and 13c, because additional data was available to develop individual site-specific selenium standards for Corral Gulch, Duck Creek, Greasewood Creek and Yellow Creek.  The assessment locations are listed at 37.6(4).
H.	Aquatic Life Ammonia and Metals Standards
New Table Value Standards:  The zinc, zinc sculpin, and aluminum table values were revised in the 2010 Basic Standards hearing.  The acute and chronic zinc, zinc sculpin, and aluminum equations in 37.6(3) were modified to conform to Regulation 31.  The footnotes to the table values in 37.6(3) were renumbered to match the appropriate references.  Footnote (4 old) was deleted and a new footnote 4 was added.  
Zinc sculpin standards:  In low-hardness situations (hardness below 102 mg/L), the zinc equation is not protective of mottled sculpin (Cottus bairdi), a native west-slope fish species. For the following segments where sculpin are expected to occur and hardness could be low, both the zinc sculpin standard and the chronic zinc table value standard were adopted:
Lower Yampa/Green River Segments: 4, 7, 10, 15, 18
White River Segments: 1, 3, 6

Based upon a review of existing hardness and fishery data, the sculpin-specific zinc equation was deleted from the following segments where hardness is consistently higher than 102 mg/L:
Lower Yampa/Green River Segments: 2, 12a, 13b
Lower Colorado River Segments: 7a, 15a 
The following segments were designated as Aquatic Life Warm 2 or Cold 2, but lacked standards to fully support the Aquatic Life Use. Available data indicates that the Aquatic Life Use is attainable, and therefore the full suite of standards protective of aquatic life was added to the following segments, with a delayed effective data of December 31, 2019 on Lower Yampa segment 3b:
Lower Yampa/Green River Segments: 3b, 3i, 6, 17c
Lower Colorado River Segments: 11b, 13a
The goal qualifier for selenium was deleted on Lower Yampa/Green River segment 3b, based upon data that indicate the table value standard for selenium is attained.  
I.	Uranium Standards
At the 2010 Basic Standards rulemaking hearing, the Commission changed the Water Supply table value for uranium from 30 ug/L to a hyphenated standard of 16.8-30 ug/L.  The Commission revised the language in 37.5(3)(c) to reflect the change to the basin-wide standard.  A new section 37.5(3)(c)(i) was added to explain the hyphenated standard.  Subsection 37.5(3)(d) was deleted because it was redundant with 37.5(3)(c).
J.	Temporary Modifications
All existing Temporary Modifications were examined to determine if they should be allowed to expire or be extended.  Temporary Modifications were not automatically extended if non-attainment persisted due to revisions made to the Temporary Modification provisions in 2005 and 2010.  
To remain consistent with the Commission’s decisions regarding arsenic at 37.31, 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 of 0.02 ug/L and a permitted discharger with a predicted water quality–based effluent limit compliance problem:
Lower Yampa/Green River Segments: 5, 17a, 
Lower Colorado River Segments: 4c, 11h, 15b, 15c, 15d, 17b
New or modified Temporary Modifications were adopted for the following segments.
Lower Colorado Segment 4e:  The Commission extended the Type A Temporary Modification for copper from December 31, 2015 to June 30, 2017. The extension of the Temporary Modification of the underlying copper standards recognizes that Tri-State Generation and Transmission Association, Inc. (Tri-State) provided water quality data predicting a compliance issue associated with its permitted discharge on Lower Colorado Segment 4e and there remains uncertainty as to the appropriate standards for that segment.  Tri-State submitted a plan to collect additional data and to evaluate the bioavailability of copper in this segment.  The progress on resolving the uncertainty with the copper standards will be reviewed in the annual Temporary Modification hearing in December 2015.
The Commission shortened the Type A Temporary Modification for iron from December 31, 2015 to June 30, 2015. This will allow time for Tri-State to develop a more definitive plan to resolve the uncertainty with the iron standards. Tri-State provided water quality data predicting a compliance issue associated with its permitted discharge on Lower Colorado Segment 4e and there remains uncertainty as to the appropriate standards for that segment. Tri-State may request an extension of the temporary modification at the annual Temporary Modification hearing in December 2014.  
Where the Commission has adopted a narrative temporary modification of “current condition”, the Commission intends that, when implementing the temporary modification in a CDPS permit, the permit conditions will reflect the current effluent quality, recognizing that it changes over time due to seasonal variability, change in the influent flow and the concentration over time.
K.	Temperature
Ambient temperature standards for lakes 
In the 2008 triennial review, the WAT standard was found to be unattainable for a number of cold large lakes and reservoirs with apparently healthy cold-water fish populations. Because summertime temperature in the mixed layer for large lakes and reservoirs is very well correlated to the waterbody’s elevation, the Commission adopted ambient temperature standards for large lakes wherever data were available to characterize a WAT and the thermal characteristics of the lakes and reservoirs were determined to be the result of natural conditions. As a result of setting ambient temperature standards, the adequate refuge defined in Regulation 31, Table 1, footnote 5(c)(iii) was assessed using the site-specific temperature standard, and many lakes with obvious dissolved oxygen issues were considered to have adequate refuge.
Footnote 5(c)(iii) states: 
When a lake or reservoir is stratified, the mixed layer may exceed the criteria in Table 1 provided that an adequate refuge exists in water below the mixed layer. Adequate refuge depends on concurrent attainment of applicable dissolved oxygen standards. If the refuge is not adequate because of dissolved oxygen levels, the lake or reservoir may be included on the 303(d) List as “impaired” for dissolved oxygen, rather than for temperature. 
To ensure that adequate refuge is defined in a way that protects the Aquatic Life use, the Commission adopted Footnote D which was applied to the temperature standard for deep stratified lakes. Footnote D states “Assessment of adequate refuge shall rely on the Cold Large Lake table value temperature criterion and applicable dissolved oxygen standard rather than the site-specific temperature standard”, and was applied to the following lake segments: 
White River segment: 25 (Lake Avery) 
Lower Colorado River segment: 20 (Rifle Gap, Harvey Gap and Vega Reservoirs) 
Based upon a Use Attainability Analysis that demonstrates the table value standards for temperature are not attainable, ambient-based temperature standards were adopted for the following segments:
Lower Colorado River Segments: 15c, 15d, 16
Based upon a Use Attainability Analysis that determined Cold Stream Tier I species were not expected to occur, the temperature standard was changed from CS-I to CS-II on the following segment:
Lower Colorado Segment: 15b
L.	Nutrients
In March 2012, the Commission adopted interim nutrient values in the Basic Standards (Regulation 31) and created a new statewide control regulation (Regulation 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 adopted 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, 2019. 
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 85 effluent limits and discharging prior to May 31, 2012. A new section (4) was added at 37.5 describing implementation of the interim nutrient values into the tables at 37.6, 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 footnote “C” was added to the total phosphorus and chlorophyll a standards in these segments. The footnote references the table of qualified facilities at 37.5(4). 
•	For segments located entirely below these facilities, nutrient standards do not apply.
•	For rivers and streams segments, total phosphorus standards were adopted above the dischargers listed at 37.5(4) for segments with an Aquatic Life Use.  Chlorophyll a standards were adopted above the dischargers listed at 37.5(4) for segments with either an E, P, or U Recreation use classification.
•	For lakes and reservoirs segments above the dischargers listed at 37.5(4), total phosphorus and chlorophyll standards were adopted with a footnote “B” as these standards only apply to waterbodies larger than 25 acres surface area.
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 by the Division to adopt standards based on this provision in this rulemaking.
31.17(e)(iii) also allows the Commission to adopt numeric nutrient standards for circumstances where the provisions of Regulation 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:
Lower Yampa/Green River Segments: 3b, 3c, 3e, 3f, 3g, 3i, 4, 5, 6, 7, 8, 9, 10, 12a, 12b, 12c, 13a, 13b, 15, 16, 17a, 18, 19a, 19b, 20, 22c, 22d, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33
White River Segments: 1, 3, 4a, 4b, 6, 7, 8, 9c, 9d, 10a, 10b, 11, 13b, 13c, 13d, 14a, 14b, 15, 16a, 16b, 17, 18b, 19, 20, 22, 23, 24, 25, 26, 27
Lower Colorado River Segments: 4b, 4c, 5, 6, 7a, 7b, 8, 9a, 9b, 9c, 10, 11h, 12b, 13a, 13b, 13c, 13d, 13e, 13f, 14a, 14b, 14c, 15a, 15b, 15c, 15d, 16, 17a, 17b, 18, 19, 20, 21
Total Phosphorus standards were adopted for the following segments:
Lower Yampa/Green River Segments: 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 4, 5, 6, 7, 8, 9, 10, 12a, 12b, 12c, 13a, 13b, 15, 16, 17a, 17b, 17c, 18, 19a, 19b, 20, 21, 22a, 22b, 22c, 22d, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33
White River Segments: 1, 3, 4a, 4b, 6, 7, 8, 9a, 9b, 9c, 9d, 10a, 10b, 11, 13a, 13b, 13c, 13d, 14a, 14b, 15, 16a, 16b, 17, 18a, 18b, 19, 20, 22, 23, 24, 25, 26, 27
Lower Colorado River Segments: 4a, 4b, 4c, 4d, 4e, 4f, 5, 6, 7a, 7b, 8, 9a, 9b, 9c, 10, 11a, 11b, 11d, 11e, 11f, 11g, 11h, 12a, 12b, 13a, 13b, 13c, 13d, 13e, 13f, 14a, 14b, 14c, 15a, 15b, 15c, 15d, 16, 17a, 17b, 18, 19, 20, 21
Lower Colorado Segment 4e: A footnote C was added to the total phosphorus standard on this segment and on Lower Colorado Segment 4f.  Tri-State Generation and Transmission Association, Inc was added to the list of facilities at 37.5(4). Tri-State submitted effluent data that demonstrated a compliance problem with the total phosphorus standard.  At the time when Regulation 31.17(e) was adopted, it was not apparent that cooling tower discharges were a significant source of phosphorus or that these facilies would be impacted by nutrient standards.  The Commission decided to include Tri-State in the list of exempt dischargers at 37.5(4) as a matter of policy on the basis that the overall intention of the phased implementation of nutrient criteria was to control existing discharges through Regulation 85, rather than through water-quailty based effluent limits.   
M.	Direct Use Water Supply Sub-classification 
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 (Regulation 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 of reservoir that is used regularly to provide raw water directly to a water treatment plant that treats and disinfects raw water.  In this action today, 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.
White River segment 11: 		Kenney Reservoir (Western Fuels)
Lower Colorado River segment 21:	Jerry Creek Reservoirs Number 1 and 2 (Ute Water Conservancy District)
Lower Colorado River segment 21:	Palisade Cabin Reservoir (Town of Palisade)
31.17(e)(ii) also allows the Commission to adopt numeric nutrient standards for Direct Use Water Supply (“DUWS”) lakes and reservoirs.  No standards were adopted based on this provision in this rulemaking.
N.  Chromium III Standards	
A review of the chromium III standards showed that standards to protect the Aquatic Life use classification may not be protective of the Agriculture use in some high-hardness situations. A chromium III standard of CrIII(ch)=100(Trec) was added to segments with Aquatic Life and Agriculture use classifications, but no Water Supply use.  The acute chromium III standard associated with the Water Supply use is protective of the Agriculture use, but is not protective of the Aquatic Life use when hardness is less than 61 ug/l.  For segments that have both Aquatic Life and Water Supply Use classifications, a chronic chromium III standard of CrIII(ch)=TVS was added to all segments that did not previously have that standard. Changes were made to the following segments:
Lower Yampa/Green River Segments: 2, 3b, 3c, 3d, 3e, 3h, 3i, 7, 9, 10, 12b,12c, 13a, 13b, 17a, 19a, 19b, 21, 22a, 22b, 22c, 23, 25, 26, 27, 30, 32, 33
White River Segments: 1, 3, 4a, 6, 7, 8, 9a, 9b, 9c, 9d, 10a, 10b, 11, 12, 13c, 13d, 14b, 15, 16b, 17, 18a, 19, 21, 23, 25, 26, 27
Lower Colorado River Segments: 1, 2a, 2b, 3, 4a, 4c, 4d, 4e, 4f, 5, 6, 7a, 7b, 8, 9a, 9b, 9c, 10, 11a, 11b, 11d, 11f, 12a, 12b, 13a, 13b, 13c, 13d, 13f, 14a, 14b, 14c, 15a, 15b, 15c, 15d, 16, 17a, 17b, 18, 19, 20, 21
O.  Other Site-Specific Revisions
A footnote “A” was added to the chronic arsenic standard to explain the hyphenated standard on the following segments:
Lower Yampa/Green River Segments: 3e, 3h, 6, 13a, 13b, 16, 17c, 22d, 
White River Segments: 9a, 9b, 9c, 9d, 13b, 16a, 18b
Lower Colorado River Segments: 4a, 4d, 6, 11e, 12b, 13f
PARTIES TO THE RULEMAKING HEARING
1.	Grand County, Northwest Colorado Council of Governments and Northern Colorado Water Conservancy District
2.	Eagle River Water and Sanitation District
3.	Trout Unlimited
4.	WildEarth Guardians
5.	Tri-State Generation and Transmission Association
6.	Seneca Coal Company, Peabody Sage Creek Mining, LLC, and Twentymile Coal Company
7.	Western Resource Advocates
8.	Colorado River Water Conservation District
9.	Climax Molybdenum Company
10.	Trapper Mining, Inc.
11.	Upper Blue Sanitation District
12.	Clinton Ditch & Reservoir Company
13.	Vail Resorts, Inc. and Vail Summit Resorts, Inc.
14.	Eagle Park Reservoir Company
15.	Upper Eagle Regional Water Authority
16.	Colorado Parks and Wildlife
17.	Denver Water
18.	Environmental Protection Agency
19.	Powdr-Copper Mountain, LLC
20.	Town of Frisco