Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-38 - REGULATION NO. 38 - CLASSIFICATIONS AND NUMERIC STANDARDS SOUTH PLATTE RIVER BASIN LARAMIE RIVER BASIN REPUBLICAN RIVER BASIN SMOKY HILL RIVER BASIN
Section 5 CCR 1002-38.6 - TABLES

(a) The following abbreviations are used in this regulation and in the tables in Appendix 38-1:

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

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);

(c) Temporary Modification for Water + Fish Chronic Arsenic Standard

(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) Mountain whitefish-based summer temperature criteria [16.9 (ch), 21.2 (ac)] apply when and where spawning and sensitive early life stages of this species are known to occur.

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

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(a) Upper South Platte Segment 6b, Chatfield Reservoir: Chlorophyll a Assessment Thresholds

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.

(b) Upper South Platte Segment 16h: Selenium Standards and Assessment Locations

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.

(c) Upper South Platte Segment 15 and Middle South Platte Segment 1a: Dissolved Oxygen and Ammonia Standards

Dissolved Oxygen Standards:

Early Life Stage Protection Period (April 1 through July 31)

Older Life Stage Protection Period (August 1 through March 31)

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 =

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(d) Big Dry Creek Segment 1: Selenium Assessment Locations

* 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

(e) Big Dry Creek Segment 2 (Standley Lake): Chlorophyll a Assessment Thresholds Chlorophyll a = 4.4 µg/L, Mar-Nov average, 1 in 5 yr allowable exceedance frequency

(f) Upper South Platte Segment 16i, Sand Creek from Toll Gate Creek to the confluence with the South Platte River: assessment locations for selenium and total mercury

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.

(g) Upper South Platte Segment 16g (Marcy Gulch): Selenium assessment

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.

(h) Upper South Platte Segment 16j: Selenium standards (µg/L) and assessment

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

(i) Cherry Creek Segment 4b: Selenium standards (µg/L) and assessment

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.

(j) Clear Creek Segment 5: Manganese assessment

* 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.

(k) Big Dry Creek Segments 2, 3, 4a, 4b, 5a, and 5b: Ambient-based Site-specific Radionuclide Standards

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.

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

(l) Upper South Platte Lakes Segment 19: Temperature Standards

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

(m) Cache la Poudre Segment 18: Temperature Standards

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

(n) Lower South Platte Segment 3: Temperature Standards

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

(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.

(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.

(a) Upper South Platte River Segments 15 and 16i (COSPUS15 and COSPUS16i):

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.

(b) Lower South Platte River Segment 2 (COSPLS02):

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.