colorado department of public health and environment
WATER QUALITY CONTROL COMMISSION
5 CCR 1002-38
regulation no. 38
classifications and numeric standards
for
south platte river basin, laramie river basin
republican river basin, smoky hill river basin
. . . .
38.6	TABLES
. . . .
(4)	Assessment Criteria
The following criteria shall be used when assessing whether a specified waterbody is in attainment of the specified standard.
(a)	Upper South Platte Segment 6b, Chatfield Reservoir: Assessment Thresholds
chlorophyll = 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 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 Assessment Locations
For the purpose of determining attainment of the standard, dissolved oxygen measurements shall only be taken in the flowing portion of the stream and at mid depth, and 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.
(d)	Big Dry Creek Segment 1:  Selenium Assessment Locations
●	bdc 1.5:  upstream of Broomfield Wastewater Treatment Plant
●	bcd 2.0:  upstream of Westminster Big Dry Creek Wastewater Treatment Facility
●	bcd 4.0: upstream of Northglenn Wastewater Treatment Plant
(e)	Big Dry Creek Segment 2 (Standley Lake): Assessment Thresholds
Chlorophyll  = 4.4 ug/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.
●	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.
. . . .

REGULATION #38 STREAM CLASSIFICATIONS and WATER QUALITY STANDARDS

REGION: 3 and 4
               
BASIN: Upper South Platte River	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS

	
	
PHYSICAL
and
BIOLOGICAL	
INORGANIC

mg/l	
METALS

g/l
		
16a.	Mainstem of Sand Creek from the confluence of Murphy and Coal Creek in Arapahoe County to the confluence with Toll Gate Creek.	
	Aq Life Warm 2
Recreation E
Agriculture	T=TVS(WS-II) oC
D.O.=5.0 mg/l
pH=6.5-9.0
E. Coli=126/100ml	NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	S=0.002
B=0.75
NO2=0.5
NO3=100	As(ac)=340
As(ch)=100(Trec)
Cd(ac/ch)=TVS
CrIII(ac/ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Hg(ch)=0.01(Tot)
Ni(ac/ch)=TVS	Se(ac)=TVS
Se(ch)=TVS
Ag(ac/ch)=TVS
Zn(ac/ch)=TVS	
	
16i.  Mainstem of Sand Creek from the confluence with Toll Gate Creek to the confluence with the South Platte River.		Aq Life Warm 2
Recreation E
Agriculture	T=TVS(WS-II) oC
D.O.=5.0 mg/l
pH=6.5-9.0
E. Coli=126/100ml	NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	S=0.002
B=0.75
NO2=0.5
NO3=100	As(ac)=340
As(ch)=100(Trec)
Cd(ac/ch)=TVS
CrIII(ac/ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Hg(ch)=0.01(Tot)
Ni(ac/ch)=TVS	Upper:*  Se(ch)=38.2
Se(ac)=45.1
Lower:*
Se(ch)=9.0
Se(ac)=TVS

Ag(ac/ch)=TVS
Zn(ac/ch)=TVS	* See section 38.6(4)(f) for selenium assessment locations

Temporary Modifications:
Cu (ac/ch) = TVSx2.6 below the Sand Creek Water Reuse Facility outfall. 
(Type iii). Expiration date of 12/31/2015.

Hg(ch)=current condition, Expiration date of 6/30/2017

38.86	STATEMENT OF BASIS SPECIFIC STATUTORY AUTHORITY AND PURPOSE: APRIL 8, 2013 RULEMAKING FOR SAND CREEK, UPPER SOUTH PLATTE SEGMENT 16a; FINAL ACTION MAY 13, 2013; EFFECTIVE SEPTEMBER 30, 2013
The provisions of C.R S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted the following statement of basis and purpose pursuant to C.R.S 24-4-103(4).
BASIS AND PURPOSE
The Commission considered the selenium and mercury standards for Sand Creek, segment 16a of the Upper South Platte Basin.  Based on evidence presented in this hearing, the Commission divided the segment and adopted site-specific ambient-based selenium standards and a temporary modification of the mercury standard as follows.
Selenium and Resegmentation: 
As determined in an earlier hearing (December 2008), the Toll Gate Creek system, a tributary to Sand Creek, has elevated levels of selenium caused by natural or irreversible human-induced sources.  Ambient-based selenium standards were adopted for Toll Gate and its tributaries in that hearing.  In this hearing, evidence was presented that the effects of Toll Gate Creek’s contribution change the water quality characteristics of Sand Creek below its confluence with Toll Gate Creek, to the extent that the selenium levels exceed the relevant table value criteria.  In this hearing, the Commission split the mainstem of Sand Creek into two segments, retaining the segment number (16a) and the table value selenium criteria above the confluence with Toll Gate Creek.
The Commission created a new segment, segment 16i, and adopted ambient quality-based site-specific standards for selenium applicable to the portion of Sand Creek below Toll Gate Creek.  The ambient quality-based standards are based on the 85th percentile (chronic) and the 95th percentile (acute) of the selenium data collected at two specific instream monitoring locations:  Sand Creek at the Peoria Street crossing (which has a station identifier of SWA) and Sand Creek just upstream of the Union Pacific Railroad crossing (which has a station identifier of SW1); each is upstream of a wastewater outfall.  The most recent five years of data were used since there has been a persistent and significant increase in the concentration of selenium since 2008.  Two assessment locations are appropriate since the selenium concentrations consistently decline along Sand Creek, probably due to influx of lower concentration groundwater, however the mechanism has not been identified.  It is the Commission’s intent to maintain this natural or human-induced irreversible pattern of water quality, and not to inadvertently create assimilative capacity.
The Commission added assessment locations to section 38.6(4)(f) to record the assessment strategy for ambient quality-based site-specific standards for selenium applicable to Sand Creek segment 16i.  It is the Commission’s intent that attainment of the standard is to be assessed separately with data from two specific monitoring locations (SWA and SW1).  Further, it is the intent of the Commission that selenium effluent limits for any permitted discharge be calculated to assure attainment of the criteria only at the assessment location (SWA or SW1) closest to the discharge, even if the closest assessment location is upstream. 
Mercury:  
The Commission adopted a temporary modification of the mercury standard for the new segment 16i (the mainstem of Sand Creek from Toll Gate Creek to the confluence with the South Platte River).  There have been several instances of total mercury concentrations in Sand Creek below Suncor’s outfall exceeding the water quality standard.  In addition, Suncor presented evidence that it will have a compliance problem with the water quality-based effluent limit based on the existing standard.
Mercury is a bioaccumulative pollutant and fish tissue is the endpoint of concern.  The rate of bioaccumulation is variable, so there is uncertainty regarding the total mercury water column standard necessary to maintain fish tissue concentrations below the human health criteria of 0.3 mg/kg.
Suncor agreed to undertake a study to resolve the uncertainty, with the following conditions, to ensure that the fish tissue data collected is representative of the potential human health exposure to mercury:
●	Fish tissue will be sampled multiple times per year, during variable flow conditions and seasons.
●	Appropriate sampling methods will be used for capturing the larger fish individuals.
●	The largest individuals caught will be sampled for each species at site SW2-1.
●	Fish tissue samples will be collected as skinless filets, where possible.
●	Suncor will submit an annual progress report with fish tissue data to the Division every year beginning in December 2013.
●	Suncor will continue to collect monthly water quality samples and analyze them for total mercury at SW2-1 using the low-level detection method.
●	Suncor will work with the Division and EPA to calculate the bioaccumulation factor for Sand Creek and to develop a site-specific standard.
The Temporary Modification is set to expire on 6/30/2017.  This anticipates that Suncor will report progress to the Commission in the December 2015 annual Temporary Modification hearing, and that the uncertainty will be resolved during the December 2016 annual hearing.  The Commission is adopting the mercury temporary modification for the newly created Segment 16i with the notation of “current condition” rather than a numeric value.  It is the Commission’s intent that this will preserve the status quo during the term of the temporary modification.  The Commission does not intend that this temporary modification will apply to new facilities or in Preliminary Effluent Limitations.
PARTIES TO THE RULEMAKING HEARING
1.	Suncor Energy (U.S.A.)
2.	City of Aurora
3.	Colorado Division of Parks and Wildlife
4.	U.S. Environmental Protection Agency
5.	Colorado Stone, Sand & Gravel Association