COLORADO department of public health and environment
WATER QUALITY CONTROL COMMISSION
5 ccr 1002-38
Regulation No. 38
classification and Numeric standards
for
south platte river basin, laramie river basin, 
republican river basin, smoky hill river basin
. . . 
38.6	TABLES 
(1)	Introduction 
The numeric standards for various parameters in the attached tables were assigned by the Commission after a careful analysis of the data presented on actual stream conditions and on actual and potential water uses. 
Numeric standards are not assigned for all parameters listed in the Tables attached to 31.0. 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 the attached tables: 
ac	=	acute (1-day)
Ag	=	Silver
Al	=	Aluminum
. . .
Zn	=	Zinc 
(b)	In addition, the following abbreviations are used: 
Fe(ch) 	=	WS(dis)
Mn(ch)	=	WS(dis)
SO4 	=	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 31.11(6); 
(i)	existing quality as of January 1, 2000; or 
(ii) 	Iron		=	300 μg/l (dissolved)
Manganese 	=	50 μg/l (dissolved)
SO4 		=	250 mg/l 
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)	As used in the “Temporary Modifications and Qualifiers” column of the tables, the term “type i” refers to a temporary modification adopted pursuant to subsection 31.7(3)(a)(i) of the Basic Standards and Methodologies for Surface Water (i.e., “where the standard is not being met because of human-induced conditions deemed correctable within a twenty (20) year period”).  The term “type iii” refers to a temporary modification adopted pursuant to subsection 31.7(3)(a)(iii) of the Basic Standards and Methodologies for Surface Water (i.e., “where there is significant uncertainty regarding the appropriate long-term underlying standard”).
. . .
[INSERT TABLES HERE]

Table 3
Temporary Modifications (type i)
Big Dry Creek, Segment 5
Effective until December 31, 2009 for the Walnut Creek portions of segment 5:
Parameter				mg/l
Nitrate 					100
Nitrite					4.5
Effective until December 31, 2009 for all of segment 5:
Parameter				mg/l
Benzene				0.005
Carbon tetrachloride			0.005
1,2-Dichloroethane			0.005
1,1-Dichloroethene			0.007
Tetrachloroethylene			0.005
Trichloroethylene			0.005
All other organic and radiologic parameters are covered by the Basic Standards.
. . .

38.68	STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE:  DECEMBER 10, 2007 RULEMAKING REGARDING TEMPORARY MODIFICATIONS; EFFECTIVE MARCH 1, 2008
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 in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
Pursuant to the requirements in the Basic Standards (at 31.7(3)), the Commission reviewed the status of temporary modifications to determine whether the temporary modification should be modified, eliminated or extended.
Language was added to subsection 38.6(2) to explain the terms “type i” and “type iii” temporary modifications. 
In three general cases, the Commission decided to delete temporary modifications, thereby allowing the underlying standards to go into effect:
a.	Segments with no known permitted dischargers:
∙	Upper So. Platte segment 5b, Geneva Creek, temporary modification for zinc.
∙	Lower So. Platte segment 2b, temporary modifications for selenium and E coli.
b.	Segments with permitted dischargers where the dischargers are not expected to discharge the parameters of concern at levels that exceed the standard:
∙	Upper So. Platte segment 4, temporary modification for copper and zinc.
∙	Upper So. Platte segment 15, temporary modifications for fecal coliform and E. coli.
∙	Clear Creek segment 15,  temporary modifications for E. coli.
∙	Big Dry Creek segment 1, temporary modifications for fecal coliform and E. coli.
∙	Boulder Creek segment 2, temporary modifications for E. coli.
∙	Boulder Creek segment 7b, temporary modifications for E. coli.
∙	Boulder Creek segment 10, temporary modifications for E. coli.
∙	Big Thompson segment 5, temporary modifications for selenium.
∙	Big Thompson segment 9, temporary modifications for selenium and E coli.
∙	Big Thompson segment 10, temporary modifications for selenium.
∙	St. Vrain segment 4b, temporary modifications for copper and lead.
∙	Cache La Poudre segment 12, temporary modifications for E. coli.
∙	Lower So. Platte segment 1, temporary modifications for selenium.
c.	Segments where there may be permitted dischargers but for which no questions have been raised about the appropriateness of the standard.  In these cases, instream levels exceed the previous ammonia TVS or the existing nitrate standard: 
∙	Middle So. Platte segment 1b, temporary modification for ammonia.
∙	Middle So. Platte segment 5b, temporary modification for ammonia.
∙	Lower So. Platte segment 1, temporary modification for nitrate.
Temporary modifications provide time for sand and gravel dischargers to work with the Division to determine the most appropriate way to make progress towards resolving non-attainment of underlying selenium standards.  The Commission added "type iii", but took no action on the expiration date for the following segments.
∙	St Vrain segment 6, temporary modification for selenium.
∙	Big Thompson segment 4b, temporary modification for selenium.
Because parties are working to resolve uncertainty and are on schedule to address these segments at the regularly scheduled basin-wide rulemaking (June 2009), the Commission either added "Type iii" or made the reference consistent, but took no action on the expiration date for the temporary modifications for the following segments: 
Upper So Platte segments 16a and 16c: (temporary modifications for selenium).  The Selenium Stakeholders presented evidence that they are making progress on their study of selenium sources and appropriate underlying standards and will make a proposal for the 2009 rulemaking hearing. 
Big Dry Creek segment 5:  (temporary modifications for nitrate, nitrite, benzene, carbon tetrachloride, 1,2-dichloroethanen, 1,1-dichloroethene, tetrachloroethylene, and trichloroethylene).  The temporary modification was identified as a “type i” temporary modification.  The Department of Energy submitted evidence that progress is continuing and that the temporary modifications are necessary because of the Clean Up agreement.  
Boulder Creek, segment 9, Cache La Poudre segments 11 and 12:  (temporary modification for copper).  The City of Boulder (Boulder Creek) and the City of Fort Collins (Cache La Poudre) submitted evidence that they are making progress on their translator studies.
Clear Creek segments 2, 3a, 3b, 6, 9a, 9b, 11, 13b: (temporary modifications for zinc, lead, copper, manganese, and cadmium  - not all segments have all metals).  Evidence was submitted that indicated that the Upper Clear Creek Watershed Association is making progress on their study of appropriate underlying standards and will make a proposal for the 2008 rulemaking temporary modification review hearing.  The Commission adjusted the expiration date to 7/1/2009.
Big Dry Creek segment 1:  The Big Dry Creek Cities presented evidence that the natural or irreversible human-induced ambient water quality levels for selenium in Big Dry Creek Segment 1 at times exceed the relevant table value standard, and an ambient quality based standard, calculated in a manner consistent with Basic Standards requirements, is adequate to protect classified uses.  The Commission accepts the Big Dry Creek Cities’ evidence as accurate.  The Commission expressly finds that the natural or irreversible human-induced ambient water quality levels for selenium in Big Dry Creek Segment 1 exceed the relevant table value standard. Moreover, the proposed ambient quality based standard is adequate to protect classified uses and represents the highest reasonably attainable standard, based on analysis of available data that show elevated instream conditions are attributable to natural or irreversible human induced conditions. 
Strong seasonal variation associated with highly managed flow conditions (e.g., releases of irrigation water from Standley Lake) significantly influences selenium concentrations, particularly in the portion of the stream above the wastewater treatment plants.  As a result, the Commission adopts seasonal ambient quality based site-specific standards for selenium applicable to Big Dry Creek Segment 1.  During the irrigation season (April through October), ambient standards are 7.4 µg/L chronic (dis) and TVS µg/L acute (dis).  Ambient-based non-irrigation season (November through March) standards are 15 µg/L chronic (dis) and 19.1 µg/L acute (dis).  These calculations are based on the 85% (chronic) and the 95% (acute for the non-irrigation season) of the ambient selenium data collected at three specific instream monitoring locations (bdc1.5, bdc2.0 and bdc4.0) upstream of the three municipal wastewater treatment plant discharges, however, it is the Commission’s intent that the existing spatial variability of selenium in Big Dry Creek be maintained.  This composite approach was jointly developed by the Cities and the Water Quality Control Division as a reasonable method to establish the ambient based standards and to assess attainment of future stream standards for Segment 1 of Big Dry Creek. The ambient quality based site-specific standards for selenium (acute and chronic) shall apply to the entirety of Big Dry Creek Segment 1.  The Commission also removes the temporary modification currently in place for selenium in Big Dry Creek Segment 1.
PARTIES TO THE RULEMAKING
1.	Big Dry Creek Cities  (City of Westminster, City of Northglenn, and City and County of Broomfield)
2.	Colorado Rock Products Association
3.	City of Grand Junction
4.	City of Colorado Springs and Colorado Springs Utilities
5.	Upper Clear Creek Watershed Association
6.	City of Black Hawk and Black Hawk / Central City Sanitation District
7.	Department of Energy Office of Legacy Management
8.	City of Aurora
9.	Shell Frontier Oil & Gas, Inc.
10.	City of Boulder
11.	Tri-Lakes Wastewater Treatment Facility
12.	Security Sanitation District
13.	City of Fort Collins
14.	Metro Wastewater Reclamation District
15.	U.S. EPA