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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31.7	PROCESS FOR ASSIGNING STANDARDS AND GRANTING, EXTENDING, OR REMOVING TEMPORARY MODIFICATIONS
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(3)	Granting, Extending, and Removing Temporary Modifications to Numeric Standards
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 (a)	Conditions Justifying a Temporary Modification
The Commission may grant a temporary modification if:
(i)	an existing permitted discharge has a demonstrated or predicted water quality-based effluent limit compliance problem, and 
(ii)	one of the following is shown to exist:
(A)	there is significant uncertainty regarding the water quality standard necessary to protect current and/or future uses. 
(B)	there is significant uncertainty regarding the extent to which existing quality is the result of natural or irreversible human-induced conditions. 
(C)	there is significant uncertainty regarding the timing of implementing attainable source controls or treatment (this subsection C is repealed effective 10/01/2013).
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(4)	Granting, Extending and Removing Variances to Numeric Standards (effective October 1, 2013)
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31.49	STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JUNE 13, 2011 RULEMAKING; EFFECTIVE DATE JANUARY 1, 2012
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 adoption. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE:
The Commission’s decision to delay consideration of nutrient criteria nine months until March 2012 resulted in revisions to the Division’s and Commission’s long range work schedule.  Because the delay also will affect development of discharger specific variance guidance, the Commission extended the effective date of the variance provisions at 31.7(4) nine months to October 1, 2013.  The Commission also extended the repeal date of subsection C of 31.7(3)(a)(ii), nine months to October 1, 2013, This subsection C describes a condition for granting a temporary modification: significant uncertainty regarding the timing of implementing attainable source controls or treatment.  Because it is expected that this type of uncertainty will be addressed through the discharger-specific variance provisions, subsection C is scheduled to be repealed on the date the discharger-specific variance provisions become effective.