COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT
WATER QUALITY CONTROL COMMISSION 
5 CCR 1002-62
REGULATION #62
REGULATIONS FOR EFFLUENT LIMITATIONS
62.1	AUTHORITY
The Water Quality Control Commission (“Commission”) is directed by section 25-8-205, C.R.S., to promulgate control regulations to describe prohibitions, standards, concentrations, and effluent limitations on the extent of specifically identified pollutants that any person may discharge into any specific class of state waters.
Materials incorporated by reference are available for public inspection during normal business hours, or copies may be obtained at a reasonable cost, from the Administrator, Water Quality Control Commission, 4300 Cherry Creek Drive South, Denver, Colorado  80222.  All material incorporated by reference may be examined at any state publications depository library.  Copies of incorporated materials are also available at the U.S. Environmental Protection Agency’s Region 8 Technical Library located at 1595 Wynkoop Street (16th Street Mall and Wynkoop) Denver, Colorado  80202-1129.
Unless expressly stated otherwise, materials incorporated by reference are those editions in existence as of the date this regulation is promulgated or revised by the Commission, and references do not include later amendments to or editions of the incorporated.  
62.2	APPLICABILITY
The provisions of this regulation apply where the limitations and/or other conditions required hereunder are incorporated into a permit issued pursuant to Commission Regulation No. 61 (Colorado Discharge Permit System Regulations), 5 CCR 1002-61, except that this regulation does not apply to permits for stormwater discharges.
62.3	DEFINITIONS
See the Colorado Water Quality Control Act and the Commission’s codified regulations for additional definitions.
(1)	"STATE WATERS" - means any and all surface or subsurface waters which are contained in or flow in or through this state, but does not include waters in sewage systems, waters in treatment works of disposal systems, waters in potable water distribution systems, and all water withdrawn for use until use and treatment have been completed.
62.4	REGULATIONS
(1)	The effluent limitations for identified pollutants shall be applied in permits in accordance with the following requirements.
(2)	At such time as effluent limitation guidelines are promulgated by the Commission for any industry pursuant to section 25-8-205(2)(d), C.R.S., such industry shall be subject to those guidelines and shall not be subject to effluent limitations set forth below in paragraph 62.5.  If the Commission has not so promulgated effluent limitation guidelines for any particular industry, but that industry is subject to numeric effluent limitation guidelines promulgated by the United States Environmental Protection Agency (“EPA”) pursuant to the Federal Water Pollution Control Act of 1972, the effluent from these industries shall be subject to the corresponding numeric effluent limitations in the applicable EPA guidelines and shall not be subject to the effluent limitations of paragraph 62.5 below.
(3)	The effluent limitations set forth below, or promulgated according to subparagraph (2) above, are also subject to being superseded when it is found that stricter limitations are required in order to ensure that water quality standards are maintained.
62.5	SPECIFIC LIMITATIONS FOR THE DISCHARGE OF POLLUTANTS
The following numeric limits shall apply where the Water Quality Control Division (“Division”) identifies the pollutant as one that may, without treatment, be present in the discharge at a level approaching the relevant limit.  Except as required under federal law, where the Division determines that a numeric limit is infeasible, the Division shall require implementation of best management practices as a condition of the permit as necessary to control or abate the discharge of pollutants to state waters.  In no case will a discharge be held to be in compliance with any of the limitations set forth below where the discharge is diluted with other waters, unless such compliance would exist without such dilution.
(1)	Numeric Limitations
PARAMETER		PARAMETER LIMITATIONS	
		7-Day
	Average1 		30-Day
	Average2 		Instantaneous
	Maximum3 	
(a)	Biological Oxygen Demand (BOD5)	45 mg/l	30 mg/l	N/A	
(b)	Total Suspended Solids (TSS)	45 mg/l	30 mg/l	N/A	
(c)	Carbonaceous Biological Oxygen Demand (CBOD5)	40 mg/l	25 mg/l	N/A	
(d)	Residual Chlorine			0.5 mg/l  3, 5	
(e)	pH			6.0 - 9.0 s.u.3, 4	
(f)	Oil and Grease			10 mg/l 3, 6	
1	7-Day Average:  The arithmetic mean of all samples taken in a 7-day period.
2	30 Day-Average:  The arithmetic mean of all samples taken in a 30-day period.
3	As determined by the results of any single grab sample.
4	The pH shall remain at or between these values.
5	This limitation shall not apply to discharges to irrigation ditches or to ground water
6	A numeric effluent limit will be assigned in permits for discharges to surface waters, however, monitoring for a "visual sheen" will generally be required.  Where a visual sheen is detected, the discharger will be required to collect a grab sample and have it analyzed for oil and grease.  Monitoring for oil and grease may be required where there is a reasonable potential that oil and grease will be present in the effluent at concentrations at or above 10 mg/l.
These numeric limits and sampling requirements have been set with the inherent variability of the analytical procedures taken into consideration.
(2)	In addition to the above effluent limitations, the arithmetic mean of the values for effluent samples for CBOD5, BOD5 and TSS collected in a period of 30 consecutive days shall not exceed 15 percent of the arithmetic mean of the values for influent samples collected at approximately the same time during the same period (85 percent removal).  
(a)	For domestic sources, where the permittee has demonstrated that the treatment facility is unable to meet the 85 percent removal requirement for a parameter and the inability to meet the requirement is not caused by excessive infiltration, as defined in 40-CFR 35.2005(b)(16), a lower percent removal requirement or a mass loading limit may be substituted provided that the permittee can demonstrate that the provisions of 40 CFR 133.103(d) can be met.
(b)	For industrial sources, the Division may, as it finds appropriate on a case by case basis, substitute a lower percentage removal requirement or a mass loading limit for the 85 percent removal requirements of this subsection (2).  The Division may also determine, on a case by case basis, that the numeric limitations for CBOD5, BOD5, and TSS as listed in subsection (1), are sufficiently protective of the applicable designated uses, and in such case, the Division may exempt such industrial source(s) from the percentage removal requirements of this subsection (2).
(3)	The numeric limitations for TSS in section 62.5(1)(b), above, may be adjusted for waste stabilization ponds which treat domestic waste provided that (1) the waste stabilization ponds are the principal process used for secondary treatment; and (2) the facility is designed to achieve the solids removal possible with best waste stabilization pond technology.  Best waste stabilization pond technology is defined as that design criteria for ponds currently in effect as adopted by the Commission or the Division.  Since these criteria will be upgraded periodically, any permittee not in conformance with the approved design criteria will be given an opportunity to establish a reasonable implementation schedule given due consideration to design, construction, and financial capability of the permittee.  The adjusted limitations shall be as described below:

Treatment Type	7-Day Average 1	30-Day Average 2	
Non-aerated Waste
Stabilization Ponds	160 mg/l	105 mg/l	
Aerated Waste
Stabilization Ponds	110 mg/l	75 mg/l	
1	7-Day Average:  The arithmetic mean of all samples taken in a 7-day period.
2	30-Day Average:  The arithmetic mean of all samples taken in a 30-day period.
In addition, where adjusted TSS limitations are given, the 85 percent removal requirement for TSS shall be waived.
(4)	The numeric limits for pH for domestic wastewater treatment facilities may be adjusted to values outside of the limits in section 62.5(1)(e), above, subject to limitations necessary to protect applicable water quality standards, where inorganic chemicals are not added to the waste stream as part of the treatment process and where industrial contributions do not cause the pH to be less than 6.0 s.u. or greater than 9.0 s.u.
(5)	Sampling of discharges, for the purpose of the effluent limitations for pollutants set forth in section 62.4(1) above, shall be made prior to any admixture of the discharge with state waters.  All new discharges, except for individual sewage disposal (onsite) systems, shall be constructed so that a sample of the effluent can be obtained at a point after the final treatment process and before discharge to state waters.  
If samples for BOD5, CBOD5 or TSS are taken at the outfall of a final quiescent pond, with a detention time of at least 48 hours, the sample may be a grab sample.  In all other plants which cannot meet this requirement, effluent samples shall be a composite sample, comprised of a minimum of four grab samples taken approximately two hours apart.
(6)	Normally the numeric limits for BOD5 will be applied, however, they may be replaced with the numeric limits for CBOD5 in section 62.5(1)(c) at the request of the permittee.
(7)	The permittee must be able to show proof at the request of the Division of the accuracy of any flow-measuring device used in obtaining data submitted in the discharge monitoring report.  The flow-measuring device must indicate values within ten percent of the actual flow being measured.
(8)	If wastewater is returned to the source from which it was obtained, the numeric limitations specified in section 62.5(1) above, may be in addition to the measured values of the same parameter(s) in the incoming water except where an exceedance of a water quality standard would take place.
(9)	Any person subject to the numeric limits for BOD5, or CBOD5 shall have the option of establishing, to the continuing satisfaction of the Division, a relationship between BOD5 or CBOD5 and COD (chemical oxygen demand), TOC (total organic carbon), or TOD (total oxygen demand) with respect to such effluent, and the COD, TOC, or TOD values so established shall be substituted for the BOD5, or CBOD5, values required under section 62.5(1), above.
62.6	Reserved.
62.7	Reserved.
62.8	Reserved.
. . . .
62.19	STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY, AND PURPOSE; JUNE 11, 2012 RULEMAKING, EFFECTIVE JULY 30, 2012 
The provisions of sections 25-8-202(1) and 25-8-501(3), C.R.S., provide the specific statutory authority for adoption of the attached regulatory amendments. 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 revised section 62.1 to state that in addition to the Commission office and the state publications depository library, copies of materials incorporated by reference also can be viewed at the U.S. Environmental Protection Agency’s (“EPA”) Technical Library in Denver.  This revision was made for consistency with new rulemaking requirements in the Colorado Administrative Procedure Act, section 24-4-103, C.R.S.     
The Commission revised section 62.4(2) to address situations where a particular industry sector is subject to the numeric limitations in Regulation 62, and EPA subsequently promulgates an effluent limitation guideline (“ELG”) that does not include numeric effluent limitations (but rather practice-based effluent limits) for one or more of the applicable parameters.  These revisions provide that where the federal ELG sets forth numeric limits for parameters that are also included in Regulation 62, the sector must adhere to the numeric limit specified in the ELG.  Where, however, the federal ELG does not specify a numeric limitation for a certain parameter and Regulation 62 does, the regulation allows flexibility for the numeric limitation in Regulation 62 to remain applicable to that sector.  
The Commission also revised section 62.5(2) to make a clearer distinction between CBOD5, BOD5, and TSS removal requirements for domestic sources and industrial sources.  For industrial sources, the Commission found it appropriate to grant the Division discretion to substitute, in certain cases, lower percent removal requirements or mass loading limits for the 85 percent removal requirements found in that subsection.  The Commission also gave the Division discretion to exempt certain industrial sources from the further removal requirements of that subsection where the Division determines that the numeric limitations for CBOD5, BOD5, and TSS are sufficient.
The Commission also took this opportunity to make minor stylistic edits to the Regulation, such as deleting unnecessary wording in section 62.4(3), changing the term “municipality” to “permittee” in section 62.5(3) to include industrial dischargers, and abbreviating references to the Water Quality Control Commission and Division.