5 Colo. Code Regs. § 1002-38.6
The numeric standards for various parameters in this regulation and in the tables in Appendix 38-1 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 38-1, 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.
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 |
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 chronic standards, as specified in the Basic Standards and Methodologies at 31.11(6);
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.
In certain instances in the tables in Appendix 38-1, 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)
TABLE VALUE STANDARDS - FOOTNOTES
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chlorophyll a= 11.2 µg/L, summer average, 1 in 5 year allowable exceedance frequency phosphorus(Tot) = 0.035 mg/L, summer average, 1 in 5 year allowable exceedance frequency.
Selenium Standards (µg/L):
West Toll Gate Creek: Selenium(chronic)=50.6, Selenium(acute)=119.2 East Toll Gate Creek: Selenium(chronic)=14.3, Selenium(acute)=15.9 Toll Gate Creek: Selenium(chronic)=26.5, Selenium(acute)=29.5
Selenium Assessment Locations:
* Toll Gate Creek (TG6): Downstream of the confluence of East and West Toll Gate Creeks, at 6th Avenue near the gage station.
* East Toll Gate Creek (ET1): Upstream of the confluence with West Toll Gate Creek, at Chambers Road and 1st Avenue.
* West Toll Gate Creek (WT1): Upstream of the confluence with East Toll Gate Creek, at 2nd Avenue.
Dissolved Oxygen Standards:
Early Life Stage Protection Period (April 1 through July 31)
1-Day1,2,3 | 3.0 mg/L (acute) |
7-Day Average1,4,5 | 5.0 mg/L |
Older Life Stage Protection Period (August 1 through March 31)
1-Day1,2 | 2.0 mg/L (acute) |
7-Day Mean of Minimums1,6 | 2.5 mg/L |
30-Day Average1,4 | 4.5 mg/L |
Dissolved Oxygen Footnotes
1. For the purposes of determining attainment of the standards, dissolved oxygen measurements shall only be taken in the flowing portion of the stream and at mid-depth, at least six inches above the bottom of the channel. Dissolved oxygen measurements in man-made pools are not to be used for determination of attainment of the standards. All sampling protocols and test procedures shall be in accordance with procedures and protocols approved by the division.
2. During a 24-hour day dissolved oxygen levels are likely to be lower during the nighttime when there is no photosynthesis. The dissolved oxygen levels should not drop below the acute standard (ELS acute standard of 3.0 mg/L or the Older Life Stage (OLS) standards of 2.0 mg/L). However, if during the Early Life Stage (ELS) period multiple measurements are below 3.0 mg/L during the same nighttime period, the multiple measurements shall be considered a single exceedance of the acute standard. For measurements below 2.0 mg/L during either the ELS or the OLS periods, each hourly measurement below 2.0 mg/L shall be considered an exceedance of the acute standards.
3. In July, the dissolved oxygen level may be lower than the 3.0 mg/L acute standard for up to 14 exceedances in any one year and up to a total of 21 exceedances in three years before there is a determination that the acute dissolved oxygen standards is not being met. Exceedances shall be counted as described in Footnote 2.
4. A minimum of four independent daily means must be used to calculate the average for the 7-day average standard. A minimum of eight independent daily means must be used to calculate the average for the 30-day average standard. The four days and the eight days must be representative of the 7-day and the 30-day periods respectively. The daily means shall be the mean of the daily high and low values. In calculating the mean values, the dissolved oxygen saturation value shall be used in place of any dissolved oxygen measurements which exceed saturation.
5 For Upper South Platte Segment 15, north of the Lupton Bottoms Ditch diversion, the ELS 7-day average standards for the period July 1 - June 31 shall be 4.6 mg/L.
6. The 7-day mean minimum is the average of the daily minimums measured at the location on each day during any 7-day period.
Ammonia Standards:
Early Life Stage Protection Period (April 1 through July 31)
Ammonia Warm Water = mg/L as N (Total)
Acute = TVS Chronic =
* bdc 1.5: Upstream of Broomfield Wastewater Treatment Plant
* bdc 2.0: Upstream of Westminster Big Dry Creek Wastewater Treatment Facility
* bdc 4.5: Upstream of Northglenn Wastewater Treatment Plant
Selenium Standards (µg/L):
Upper: Selenium(chronic)=38.2, Selenium(acute)=45.1
Lower: Selenium(chronic)=9.0, Selenium(acute)=TVS
Selenium Assessment Locations:
* Upper - (SWA): Downstream of the confluence of Sand Creek and Toll Gate Creek approximately 250 meters upstream of the Sand Creek Water Reuse Facility (SCWRF) discharge near the Peoria Street Bridge.
* Lower - (SW1): Above Suncor, approximately 60 meters upstream of the Union Pacific Railroad crossing and upstream of Brighton Boulevard.
Mercury Assessment Locations and Method:
* Sand Creek (SWP) - Downstream of the sheet piling drop structure located near the Brighton Blvd. Bridge.
* Sand Creek (SWP2-1) - Approximately 600 feet downstream of Suncor Out fall 003 and immediately upstream of the Burlington Ditch Siphon.
* Attainment of the standard below Brighton Blvd. shall be assessed using the weighted 85th percentile total mercury concentration from both assessment locations.
Determination of attainment of the chronic and acute selenium standards will be based on the 85th and 95th percentile, respectively, of paired samples taken the same day from from the two following locations:
* L29: Marcy Gulch upstream of Santa Fe Drive, immediately upstream of the Centennial Water & Sanitation District WWTF
* L36: Marcy Gulch upstream of the confluence with the South Platte River.
Lee Gulch: Selenium(chronic)=10, Selenium(acute)=TVS
Little's Creek: Selenium(chronic)=6, Selenium(acute)= TVS
Big Dry Creek: Selenium(chronic)=23, Selenium(acute)=26
Little Dry Creek: Selenium(chronic)=11, Selenium(acute)=TVS
Determination of attainment of the chronic and acute selenium standards will be based on the 85th and 95th percentile, respectively. The selenium assessment locations are:
* Lee Gulch: Upstream of the confluence with the South Platte River
* Little's Creek: Upstream of the confluence with the South Platte River
* Big Dry Creek: Upstream of the confluence with the South Platte River
* Little Dry Creek: Upstream of the confluence with the South Platte River
Upper Cottonwood Creek:
October-February Selenium(acute/chronic)=TVS/14.0
March-September Selenium(acute/chronic)=TVS/7.1
Lower Cottonwood Creek:
October-February Selenium(acute/chronic)=TVS/5.1
March-September Selenium(acute/chronic)=TVS
Break between Upper and Lower Cottonwood Creek is at the confluence with Lone Tree Creek.
Upper Lone Tree Creek:
October-February Selenium(acute/chronic)=41.0/37.2
March-September Selenium(acute/chronic)=19.3/19.0
Lower Lone Tree Creek: Selenium(acute/chronic)=TVS
Break between Upper and Lower Lone Tree Creek is at the ACCWA Lone Tree Facility Outfall.
Upper Windmill Creek: Selenium(acute/chronic)=TVS
Middle Windmill Creek:
October-February Selenium(acute/chronic)=TVS/15.1
March-September Selenium(acute/chronic)=TVS/8.4
Lower Windmill Creek: Selenium(acute/chronic)=TVS
Break between Upper, Middle and Lower Windmill Creek is at the assessment locations.
Determination of attainment of the chronic and acute selenium standards will be based on the 85th and 95th percentile, respectively.
* Upper Cottonwood Creek: From headwaters to confluence with Lone Tree Creek, to be assessed at CT-P2 - 39.605694, -104.84825. At Peoria St.
* Lower Cottonwood Creek: From confluence with Lone Tree Creek to terminus at Cherry Creek Reservoir, to be assessed at CT2-39.627861, -104.85025. West of Perimeter Road and south of bike path.
* Upper Lone Tree Creek: From headwaters to just above site LTC-3, to be assessed using data from LTC-1 and LTC-2
LTC-1 - 39.58435, -104.838017. Approximately 0.15 miles N of S. Revere Pkwy.
LTC-2 - 39.59685, -104.838217. Approximately 10 yards N of E. Peakview Ave.
* Lower Lone Tree Creek: From site LTC-3 to confluence with Cottonwood Creek, to be assessed using data from LTC-3 and LTC-4
LTC-3 - 39.604817, - 104.837083. Below ACWWA Lone Tree facility outfall.
LTC-4 - 39.614483, 104.840217. Downstream of confluence with Windmill Creek
* Upper Windmill Creek: From Headwaters to WC-1 - Site WC-1-39.574967, -104.830017. West of Potomac St and South of Broncos Pkwy.
* Middle Windmill Creek: All sites between (but not including) WC-1 and WC-2. WC-1-39.574967, -104.830017. West of Potomac St and South of Broncos Pkwy.
WC-2-39.59655, -104.821767. North of Cherry Creek Trail.
* Lower Windmill Creek: From site WC-2 to confluence with Lone Tree Creek, to be assessed at WC-2-39.59655, -104.821767. North of Cherry Creek Trail.
* Below Woods Creek: West Fork of Clear Creek approximately 0.3 miles downstream of Berthoud Falls (39.771829°, -105.803418°).
* Mouth of West Fork: West Fork of Clear Creek near County Road 257.
The radionuclides listed in the table below shall be maintained at the lowest practical level and in no case shall they be increased by any cause attributable to municipal, industrial, or agricultural practices to exceed the site-specific numeric standards.
Parameter | Segment 2 (Standley Lake)1 | Segment 3 (Great Western Reservoir)1 | Segments 4a, 4b, 5a, and 5b1 |
Ambient-based site-specific standards | |||
Gross Alpha | 6 | 5 | NA |
Gross Beta | 9 | 12 | NA |
Plutonium | 0.03 | 0.03 | 0.152,3 |
Americium | 0.03 | 0.03 | 0.15 2,3 |
Tritium | 500 | 500 | 500 |
Uranium | 3 | 4 | 16.8 µg/L |
Other site-specific standards | |||
Curium | 60 | 60 | 60 |
Neptunium | 30 | 30 | 30 |
Radionuclides Footnotes:
1. Statewide standards also apply for radionuclides not listed above.
2. 0.15 pCi/L Statewide Basic Standards.
3. For plutonium and americium measurements in Segment 4a in Woman Creek and Segment 5 in Walnut Creek, attainment will be assessed based on the results of a 12-month flow-weighted rolling average concentration (computed monthly).
NA = No site-specific standard applies
Platte Canyon Reservoir:
DM and MWAT = CLL from 1/1 - 2/29
DM = CLL and MWAT = 25.0 from 3/1 - 12/31
Antero Reservoir:
DM and MWAT = CLL from 1/1 - 3/31
DM = CLL and MWAT = 19.6 from 4/1 - 12/31
Elevenmile Reservoir:
DM and MWAT = CLL from 1/1 - 3/31
DM = CLL and MWAT = 19.8 from 4/1 - 12/31
Spinney Mountain Reservoir:
DM and MWAT = CLL from 1/1 - 3/31
DM = CLL and MWAT = 20.2 from 4/1 - 12/31
Cheesman Reservoir:
DM and MWAT = CLL from 1/1 - 3/31
DM = CLL and MWAT = 21.9 from 4/1 - 12/31
Strontia Springs Reservoir:
DM and MWAT = CLL from 1/1 - 3/31
DM = CLL and MWAT = 22.6 from 4/1 - 12/31
Jefferson Lake:
DM and MWAT = CLL from 1/1 - 3/31
DM = 22.4 and MWAT = 16.6 from 4/1 - 12/31
All other locations DM and MWAT = CL, CLL year-round
All locations DM and MWAT = CL,CLL from 1/1 - 3/31
Barnes Meadow Reservoir DM = CL and MWAT = 16.6 from 4/1 - 12/31
Chambers Lake DM = 22.4 and MWAT =16.6 from 4/1 - 12/31
All other locations DM and MWAT = CL,CLL from 4/1 - 12/31
All locations DM and MWAT = WL from 1/1 - 3/31
North Sterling Reservoir DM = WL and MWAT = 26.1 from 4/1 - 12/31
Jumbo Reservoir DM = WL and MWAT = 27 from 4/1 - 12/31
Jackson Reservoir DM = WL and MWAT = 28.1 from 4/1 - 12/31
All other locations DM and MWAT = WL from 4/1 - 12/31
The stream classifications and water quality standards tables in Appendix 38-1 are incorporated herein by reference.
The following is information regarding duration and measured form of standards in Appendix 38-1:
Discharger-Specific Variance, Suncor Energy (U.S.A.) Inc., Commerce City Refinery (CO0001147): Adopted 10/11/2016.
Selenium (acute) = TVS: no limit; Selenium (chronic) = 9: 24 µg/L. Expiration date: 12/31/2023.
Discharger-specific Variance, Town of Crook (COG589015), Adopted 6/13/2022.
Ammonia (acute): Initial AEL=4 lbs/day, Final AEL=3.4 lbs/day;
Ammonia (chronic): Initial AEL=4 lbs/day, Final AEL=3.4 lbs/day.
Includes a Pollutant Minimization Program.
Expiration date: 12/31/2025.
5 CCR 1002-38.6