5 Colo. Code Regs. § 1002-35.6
Current through Register Vol. 47, No. 22, November 25, 2024
Section 5 CCR 1002-35.6 - [Effective 12/31/2024] TABLES(1)IntroductionThe numeric standards for various parameters in this regulation and in the tables in Appendix 35 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 35-1, 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 35-1: 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 |
sc | = sculpin |
sp | = spawning |
SSE | = site-specific equation |
T | = total recoverable |
t | = total |
tr | = trout |
TVS | = table value standard |
tjg/L | = micrograms per liter |
UP | = use-protected |
WL | = warm lake temperature tier |
WS | = water supply |
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 31.16 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 35-1 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 StandardsIn certain instances in the tables in Appendix 35-1, 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 uniess 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)Discharger-specific Variances(a) San Miguel Segment 12c (C0GUSM12c): Disclnarger-specific Variance, Town of Nucia (COG589067), Adopted 10/11/2016.
Ammonia (acute): AEL=no limit;
Ammonia (chronic): AEL=13.8 mg/L (11/1-4/30);
Ammonia (chronic): AEL=8.3 mg/L (5/1-10/31).
Expiration date: 12/31/2026.
(5)Stream Classifications and Water Quality Standards TablesThe stream classifications and water quality standards tables in Appendix 35-1 are incorporated herein by reference.
The following is information regarding duration and measured form of standards in Appendix 35-1:
(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)Site-specific Standards, Assessment Locations, and Assessment CriteriaThe following criteria and/or locations shall be used when assessing whether a specified waterbody is in attainment of the specified standard.
(a) Upper Gunnison Segment 18b: Temperature Assessment Locations (4/1 - 10/31) *Tomichi Creek at Doyleville: 38.456592, -106.626869
*Tomichi Creek at Gunnison: 38.521111, -106.940958
(b) North Fork Gunnison Segment 3: Temperature Assessment Location (3/16 - 11/15) *Nortin Forl Gunnison River above moutin near Lazear: 38.785167, -107.833417
38 CR 01, January 10, 2015, effective 6/30/201538 CR 03, February 10, 2015, effective 6/30/201539 CR 03, February 10, 2016, effective 3/1/201639 CR 03, February 10, 2016, effective 6/30/201639 CR 23, December 25, 2016, effective 12/30/201640 CR 03, February 10, 2017, effective 6/30/201740 CR 17, September 10, 2017, effective 12/31/201742 CR 04, February 25, 2019, effective 6/30/201943 CR 03, February 10, 2020, effective 6/30/202044 CR 05, March 10, 2021, effective 6/30/202144 CR 17, September 10, 2021, effective 12/31/202145 CR 17, September 10, 2022, effective 9/30/202246 CR 10, May 25, 2023, effective 6/14/202347 CR 18, September 25, 2024, effective 12/31/2024