Statutes, codes, and regulations
Colorado Administrative Code
Department 1000 - Department of Public Health and EnvironmentDivision 1002 - Water Quality Control Commission (1002 Series)
Rule 5 CCR 1002-36 - REGULATION NO. 36 - CLASSIFICATIONS AND NUMERIC STANDARDS FOR RIO GRANDE BASIN
Section 5 CCR 1002-36.6 - [Effective 12/31/2024] TABLES

5 Colo. Code Regs. § 1002-36.6

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Current through Register Vol. 47, No. 20, October 25, 2024
Section 5 CCR 1002-36.6 - [Effective 12/31/2024] TABLES
(1)Introduction

The numeric standards for various parameters in this regulation and in the tables in Appendix 36-1 were assigned by the Commission after a careful analysis of the data presented on actual stream conditions and on actual and potential water uses. For each parameter listed in the tables in Appendix 36-1, only the most stringent standard is shown. Additional, less stringent standards may apply to protect additional uses and can be found in the tables in Regulation No. 31.

Numeric standards are not assigned for all parameters listed in the tables in 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 this regulation and the tables in Appendix 36-1:

ac

=

acute (1-day)

AEL

=

alternative effluent limit

°C

=

degrees Celsius

ch

=

chronic (30-day)

CL

=

cold lake temperature tier

CLL

=

cold large lake temperature tier

CS-I

=

cold stream temperature tier one

CS-II

=

cold stream temperature tier two

DM

=

daily maximum temperature

D.O.

=

dissolved oxygen

DUWS

=

direct use water supply

E. coli

=

Escherichia coli

mg/L

=

milligrams per liter

MWAT

=

maximum weekly average temperature

OW

=

outstanding waters

sp

=

spawning

SSE

=

site-specific equation

T

=

total recoverable

t

=

total

tr

=

trout

TVS

=

table value standard

µg/L

=

micrograms per liter

UP

=

use-protected

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

(b) In addition, the following abbreviations are used:

Iron (chronic)

=

WS

Manganese (chronic)

=

WS

Sulfate (chronic)

=

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 31.11(6);

(i) existing quality as of January 1, 2000; or
(ii) Iron = 300 µg/L (dissolved)

Manganese = 50 µg/L (dissolved)

Sulfate = 250 mg/L (dissolved)

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) 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 µg/L that has been set to protect the Water + Fish qualifier is listed in the Other column in Appendix 36-1 tables as As(ch)=hybrid.
(ii) For discharges existing on or before 6/1/2013, the temporary modification is: As(ch)=current condition, expiring on 12/31/2029. Where a permit for an existing discharge is reissued or modified while the temporary modification is in effect, the division will include additional permit Terms and Conditions, which may include requirements for additional monitoring, source identification, and characterization of source control and treatment options for reducing arsenic concentrations in effluent. Where a permit for an existing discharge is reissued or modified while the temporary modification is in effect, and the permit previously included the additional permit Terms and Conditions, the division may include low cost activities to control sources of arsenic as an additional element of the permit Terms and Conditions.
(iii) For new or increased discharges commencing on or after 6/1/2013, the temporary modification is: As(ch)=0.02-3.0 µg/L (total recoverable), expiring on 12/31/2029.
(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 tables in Appendix 36-1, 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 µg/L unless noted)

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TABLE VALUE STANDARDS - FOOTNOTES

(1) Metals are stated as dissolved unless otherwise specified. Nitrogen and phosphorus standards are based upon the concentration of total nitrogen and total phosphorus.
(2) Hardness values to be used in equations are in mg/L as calcium carbonate and shall be no greater than 400 mg/L, except for aluminum for which hardness shall be no greater than 220 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. The "T" in the chronic equations stands for temperature.
(5) The acute(warm) cadmium equation applies to segments classified as Aquatic Life Warm Class 1 or 2. The acute(cold) cadmium equation applies to segments classified as Aquatic Life Cold Class 1 or 2.
(6) For lakes and reservoirs, the chlorophyll a, total nitrogen, and total phosphorus standards for Aquatic Life and Recreation apply only to lakes and reservoirs greater than 25 acres in surface area. The chlorophyll a standard for Direct Use Water Supply (DUWS) applies to lakes and reservoirs of any size.
(7) Unless the stable forms of chromium in a waterbody have been characterized and shown not to be predominantly chromium VI, data reported as the measurement of all valence states of chromium combined should be treated as chromium VI. In addition, in no case can the sum of the concentrations of chromium III and chromium VI or data reported as the measurement of all valence states of chromium combined exceed the water supply standards of 50 µg/L chromium in those waters classified for domestic water use.
(8) Selenium is a bioaccumulative metal and subject to a range of toxicity values depending upon numerous site-specific variables.

___________________________________________________________________________________

(4)Site-specific Standards, Assessment Locations, and Assessment Criteria
(a) Seasonal Aluminum Standards for Alamosa River/La Jara Creek/Conejos River Segment 8, Terrace Reservoir:

5/1-6/30 Near Surface:

Aluminum(chronic)=873(T) µg/L

Aluminum(acute)=TVS(T) µg/L

Aluminum(chronic)=59 µg/L

Aluminum(acute)=159 µg/L

7/1-4/30 Near Surface:

Aluminum(chronic)=102(T) µg/L

Aluminum(acute)=TVS(T) µg/L

Aluminum(chronic)=9 µg/L

Aluminum(acute)=15 µg/L

5/1-6/30 Near Bottom:

Aluminum(chronic)=1,542(T) µg/L

Aluminum(acute)=5,583(T) µg/L

Aluminum(chronic)=41 µg/L

Aluminum(acute)=65 µg/L

7/1-4/30 Near Bottom:

Aluminum(chronic)=227(T) µg/L

Aluminum(acute)= TVS(T) µg/L

Aluminum(chronic)=9 µg/L

Aluminum(acute)=12 µg/L

(b) Site-specific standards and assessment locations for Rio Grande Segment 4a:

Standards effective through 12/31/2028

Low flow (August 1-March 31):

Cadmium(chronic)=0.50 µg/L

Zinc(acute/chronic)=257 / 164 µg/L

High flow (April 1-July 31):

Cadmium(chronic)=0.42 µg/L

Zinc(acute/chronic)=115 / 88 µg/L

Tier 1 standards effective 1/1/2029 through 12/31/2030

Low flow (August 1-March 31):

Cadmium(chronic)=TVS

Zinc(acute/chronic)=253 / 162 µg/L

High flow (April 1-July 31):

Cadmium(chronic)=0.42 µg/L

Zinc(acute/chronic)=115 / 88 µg/L

Tier 2 standards effective from 1/1/2031

Low flow (August 1-March 31):

Cadmium(chronic)=TVS

Zinc(acute/chronic)=142 / 64 µg/L

High flow (April 1-July 31):

Cadmium(chronic)=TVS

Zinc(acute/chronic)=51 µg/L / TVS

Assessment Locations: For assessing the standards on Segment 4a, data from the following three locations will be combined:

* Station RG-4 (a/k/a 8104K): Rio Grande downstream of Highway 149 bridge near Wason Ranch (37.821943, -106.889589)

* Station RG-8 (a/k/a 8104E): Rio Grande upstream of Highway 149 bridge near La Garita Ranch Drive (37.777672, -106.836631)

* Station RG-9 (a/k/a 000135): Rio Grande downstream of 4 UR/Goose Creek Road bridge (37.765798, -106.830305)

(c) Site-specific standards and assessment locations for Rio Grande Segment 7:

Standards effective through 12/31/ 2028

West Willow

Low flow (August 1-March 31):

Cadmium(acute/chronic)=32.6 / 27.4 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=108 / 102 µg/L

Manganese(acute/chronic)=3,320 / 2,425 µg/L

Zinc(acute/chronic)=11,960 / 9,360 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=22.5 / 15.5 µg/L

Copper(acute/chronic)=34.3 / 28.0 µg/L

Lead(acute/chronic)=TVS / 23.5 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=4,001 / 3,765 µg/L

Windy Gulch

Low flow (August 1-March 31):

Cadmium(acute/chronic)=13.3 / 13.3 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / TVS

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=3,584 / 3,492 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=7.1 / 5.9 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 1.68 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=1,940 / 1,558 µg/L

Willow Creek

Low flow (August 1-March 31):

Cadmium(acute/chronic)=20.9 / 16.9 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 24.4 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=5,861 / 5,427 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=10.9 / 8.5 µg/L

Copper(acute/chronic)=11.2 / 8.2 µg/L

Lead(acute/chronic)=TVS / 14.2 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=2,667 / 1,873 µg/L

Tier 1 standards effective 1/1/2029 through 12/31/2030

West Willow

Low flow (August 1-March 31):

Cadmium(acute/chronic)=32.6 / 27.4 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=108 / 102 µg/L

Manganese(acute/chronic)=3,320 / 2,425 µg/L

Zinc(acute/chronic)=11,960 / 9,360 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=22.5 / 15.5 µg/L

Copper(acute/chronic)=34.3 / 28.0 µg/L

Lead(acute/chronic)=TVS / 23.5 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=4,001 / 3,765 µg/L

Windy Gulch

Low flow (August 1-March 31):

Cadmium(acute/chronic)=13.3 / 13.3 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / TVS

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=3,584 / 3,492 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=7.1 / 5.9 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 1.68 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=1,940 / 1,558 µg/L

Willow Creek

Low flow (August 1-March 31):

Cadmium(acute/chronic)=14.4 / 11.6 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 17.0 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=4,041 / 3,743 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=9.5 / 7.4 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 12.5 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=2,324 / 1,635 µg/L

Tier 2 standards effective from 1/1/2031 West Willow

Low flow (August 1-March 31):

Cadmium(acute/chronic)=19.1 / 13.0 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=68.2 / 61.2 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=6,055 / 3,011 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=14.9 / 7.7 µg/L

Copper(acute/chronic)=27.0 / 20.5 µg/L

Lead(acute/chronic)=TVS / 9.5 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=2,498 / 2,254 µg/L

Windy Gulch

Low flow (August 1-March 31):

Cadmium(acute/chronic)=13.3 / 13.3 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / TVS

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=3,584 / 3,492 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=7.1 / 5.9 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 1.68 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=1,940 / 1,558 µg/L

Willow Creek

Low flow (August 1-March 31):

Cadmium(acute/chronic)=14.9 / 11.1 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 7.7 µg/L

Manganese(acute/chronic)=TVS /TVS

Zinc(acute/chronic)=3,521 / 3,106 µg/L

High flow (April 1-July 31):

Cadmium(acute/chronic)=6.3 / 4.0 µg/L

Copper(acute/chronic)=TVS / TVS

Lead(acute/chronic)=TVS / 6.0 µg/L

Manganese(acute/chronic)=TVS / TVS

Zinc(acute/chronic)=1,758 / 974 µg/L

Assessment Locations:

West Willow

* Station WW-A (a/k/a WW-1): West Willow just above East Willow Confluence (37.864431, -106.925529)

Windy Gulch

* Station WNG-A (a/k/a WG-L): Windy Gulch at mouth (37.856498, -106.928140)

Willow Creek

* Station W-C (a/k/a W-Flume and 8105D): Willow Creek at Flume above Creede (37.855873, -106.927282)

(d) Site-specific temperature assessment location for Closed Basin-San Luis Valley River Basin Segment 12b:

* Saguache Creek above Ford Creek (38.163367, -106.290418)

(5) Stream Classifications and Water Quality Standards Tables

The stream classifications and water quality standards tables in Appendix 36-1 are incorporated herein by reference.

The following is information regarding duration and measured form of standards in Appendix 36-1:

(a)E. coli criteria and resulting standards for individual water segments are established as indicators of the potential presence of pathogenic organisms. Standards for E. coli are expressed as a two-month geometric mean. Site-specific or seasonal standards are also two-month geometric means unless otherwise specified.
(b) The pH standards of 6.5 (or 5.0) and 9.0 are an instantaneous minimum and maximum, respectively to be applied as effluent limits. In determining instream attainment of water quality standards for pH, appropriate averaging periods may be applied, provided that beneficial uses will be fully protected.
(c) All mercury standards apply to the total recoverable fraction of all forms, both organic and inorganic, of mercury in water.
(d) All ammonia, nitrate, and nitrite standards are based upon the concentration reported as nitrogen.
(6) Discharger-specific Variances
(a) Alamosa River/La Jara Creek/Conejos River Segment 12 (CORGAL12):

Discharger-specific Variance, Town of La Jara (CO0020150), Adopted 6/13/2022.

Nitrate (acute), implemented as Total Inorganic Nitrogen (TIN) (acute): Initial AEL=23 mg/L, Final AEL=14.5 mg/L.

Includes a Pollutant Minimization Program. (see 36.51(B)) Expiration date: 12/31/2025.

5 CCR 1002-36.6

38 CR 03, February 10, 2015, effective 6/30/2015
39 CR 03, February 10, 2016, effective 3/1/2016
39 CR 03, February 10, 2016, effective 6/30/2016
40 CR 03, February 10, 2017, effective 6/30/2017
41 CR 01, January 10, 2018, effective 1/31/2018
41 CR 03, February 10, 2018, effective 6/30/2018
41 CR 17, September 10, 2018, effective 12/31/2018
42 CR 04, February 25, 2019, effective 6/30/2019
43 CR 03, February 10, 2020, effective 6/30/2020
44 CR 05, March 10, 2021, effective 6/30/2021
44 CR 17, September 10, 2021, effective 12/31/2021
45 CR 17, September 10, 2022, effective 9/30/2022
46 CR 10, May 25, 2023, effective 6/14/2023
46 CR 21, November 10, 2023, effective 12/31/2023
47 CR 18, September 25, 2024, effective 12/31/2024