COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT
WATER QUALITY CONTROL COMMISSION
REGULATION NO. 31
THE BASIC STANDARDS AND METHODOLOGIES FOR SURFACE WATER
(5 CCR 1002-31)
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BASIC STANDARDS FOR ORGANIC CHEMICALS
(in micrograms per liter)
	
Parameter		Human Health Based1	Aquatic Life Based4	
	CAS No.	Water Supply2	Water+ Fish3	
Fish Ingestion8	Acute	Chronic	
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Dioxane 1,4-	123-91-1	6.1(effective through 3/21/2012)	
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Dioxane 1,4-	123-91-1	3.2(effective 3/22/2012)	
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Nonylphenol	84852‑15‑3 and 25154‑52‑3	---	---	---	28 (effective 1/1/2011)	6.6 (effective 1/1/2011)	
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31.47	STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE:  OCTOBER 13, 2009 RULEMAKING, EFFECTIVE DATE OF NOVEMBER 30, 2009 
The provisions of sections 25-8-202(1)(b); 25-8-204; and 25-8-402, C.R.S., provide the specific statutory authority for the amendments to this regulation adopted by the Water Quality Control Commission (Commission).  The Commission has also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
In 2007, the Commission adopted aquatic life-based standards for nonylphenol with a delayed effective date of 7/1/2010.  The purpose of the delayed effective date was to address uncertainties associated with analytical methods and possible source control options.  The effective date for nonylphenol standards was identified as an issue for the June 2010 Basic Standards Rulemaking Hearing.  In this written comment rulemaking, the Commission postponed the effective date for nonylphenol standards until January 1, 2011 to avoid implementation of these standards prior to their being addressed at the June 2010 hearing.
During its September 2004 rulemaking, the Commission adopted two standards for 1,4 dioxane -- 6.1 ug/L to be effective through March 21, 2010; and 3.2 ug/L to become effective on March 22, 2010. The dual standard was adopted, in part, due to the uncertainty about the risks posed by 1,4 dioxane and the fact that EPA was in the process of updating the Integrated Risk Information System (“IRIS”) database for that compound. At that time, the Commission adopted the 6.1 µg/L value (which had been typically used for remedial activities in Colorado) as a temporary standard in order to maintain the status quo for a period of five years to give EPA time to complete its IRIS update.  The Commission determined that if EPA’s pending review resulted in a change in the IRIS value, the Commission could consider a corresponding revision of its standards.  As of this date, EPA has not completed the IRIS review. 
In May 2009, EPA released an updated draft toxicological review on 1,4 dioxane for external peer review. According to the current schedule, final completion of the IRIS update should occur before the end of 2011.
In order to continue the status quo until EPA completes the IRIS update, the Commission is postponing the effective date for the more restrictive 1,4 dioxane standard of 3.2 ug/L from March 22, 2010 to March 22, 2012 to give EPA time to finish the IRIS update.