Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-36 - REGULATION NO. 36 - CLASSIFICATIONS AND NUMERIC STANDARDS FOR RIO GRANDE BASIN
Section 5 CCR 1002-36.6 - TABLES

Universal Citation: 5 CO Code Regs 1002-36 ยง 6

Current through Register Vol. 47, No. 17, September 10, 2024

(1) Introduction

The numeric standards for various parameters in this regulation and in the tables in Appendix 32 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 32-1, 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 32-1:

Ac

= acute (1-day)

oC

= 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

D.O.

= dissolved oxygen

DM

= daily maximum temperature

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

WS

= water supply

WS-I

= warm stream temperature tier one

WS-II

= warm stream temperature tier two

WS-III

= warm stream temperature tier three

WL

= warm lake temperature tier

(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 31.16 Table II and III:

(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 32-1 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 12/31/2024. 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.

(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 12/31/2024.
(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 32-1, 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 |jg/L unless noted)

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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, 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) 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.

(7) Selenium is a bioaccumulative metal and subject to a range of toxicity values depending upon numerous site-specific variables.

(8) Lake trout-based summer temperature criteria [16.6 (ch), 22.4 (ac)] apply where appropriate and necessary to protect lake trout from thermal impacts.

____________________________________________________________________________________

(4) Site-Specific Standards, Assessment Locations, and Assessment Criteria

The following criteria shall be used when assessing whether a specified waterbody is in attainment of the specified standard.

(a) Seasonal Aluminum Standards for Alamosa River/La Jara Creek/Conejos River Segment 8, Terrace Reservoir:

5/1-6/30 Near Surface:

7/1-4/30 Near Surface:

Aluminum(chronic)=873(T) µg/L

Aluminum(chronic)=102(T) µg/L

Aluminum(acute)=TVS(T) µg/L

Aluminum(acute)=TVS(T) µg/L

Aluminum(chronic)=59 µg/L

Aluminum(chronic)=9 µg/L

Aluminum(acute)=159 µg/L

Aluminum(acute)=15 µg/L

5/1-6/30 Near Bottom:

7/1-4/30 Near Bottom:

Aluminum(chronic)=1,542(T) µg/L

Aluminum(chronic)=227(T) µg/L

Aluminum(acute)=5,583(T) µg/L

Aluminum(acute)= TVS(T) µg/L

Aluminum(chronic)=41 µg/L

Aluminum(chronic)=9 µg/L

Aluminum(acute)=65 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) All phosphorus standards are based upon the concentration of total phosphorus. For total phosphorus, stream standards are expressed as an annual median and for lakes standards as a summer (July 1 - September 30) average in the mixed layer. For chlorophyll a, stream standards are expressed as a maximum of attached algae and lakes standards as a summer (July 1 - September 30) average in the mixed layer. For additional assessment details, see tables at Regulation 31.17(b) and (d).

(c) 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.

(d) All mercury standards apply to the total recoverable fraction of all forms, both organic and inorganic, of mercury in water.

(e) All ammonia, nitrate, and nitrite standards are based upon the concentration reported as nitrogen.

(6) Discharger-specific Variances

(a) Lower Arkansas Segment 1a (COARLA01a):

Discharger-Specific Variance, City of Pueblo James R. DiIorio Water Reclamation Facility (CO0026646): Adopted 6/12/2018.

Selenium (acute) = 19.1 ìg/L: narrative; Selenium (chronic) = 14.1 ìg/L: narrative;

Sulfate (chronic) = 329 mg/L: narrative. Expiration date: 12/31/2028.

Narrative alternative effluent limit: 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 to reduce selenium and sulfate concentrations in the effluent as much as feasible and to ensure that the discharge does not contribute to any lowering of the currently attained ambient water quality. 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 optimization measures.

(b) Lower Arkansas Segment 1b (COARLA01b):
(i) Discharger-Specific Variance, City of La Junta (CO0021261): Adopted 10/11/2016.

Selenium (acute) = TVS: no limit; Selenium (chronic) = TVS: 0.37 lbs/day as a 12-month rolling average. Expiration date: 12/31/2026.

(ii) Discharger-Specific Variance, City of Las Animas (CO0040690): Adopted 06/11/2018

Selenium (chronic) = TVS narrative. Effective Date: 12/30/2018; Expiration Date: 12/31/2025

Narrative alternative effluent limit: During the DSV term, Las Animas will implement a Pollutant Minimization Plan, which is expected to result in effluent concentrations between 0.8 - 28.4 µg/L. The following measures are required during the term of the variance to reduce selenium concentrations as much as feasible and to ensure the discharge does not contribute to any lowering of ambient in-stream water quality:

. Monitor selenium concentrations in each municipal water well and use the wells with the lowest selenium concentrations to meet water demand to the maximum extent feasible

. Initiate a water conservation program

. Locate and repair sources of water loss in the water distribution system.

. Maintain the ongoing sanitary sewer collection system replacement program to address groundwater infiltration

. Complete a wetland treatment pilot study by 12/31/2025, if compliance with water quality based effluent limits based upon the underlying standards remains infeasible after implementing the above measures.

Disclaimer: These regulations may not be the most recent version. Colorado may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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