5 Colo. Code Regs. § 1002-31.20
These Regulations establish Basic Standards and an Antidegradation Standard (Section 3.1.11 and Section 3.1.8). They also establish a system for classifying State waters, for assigning standards and for granting temporary modifications. These Regulations do not classify State waters, nor do they assign any numeric standards except those radiological standards listed under Basic Standards. In addition, one of these Regulations is a control regulation. Section 3.1.4 makes it a violation to release pollutants into State waters without the treatment or other corrective action necessary to protect the beneficial uses of the waters, or to conduct, operate, or maintain facilities, processes, activities, or waste piles in such a way as to have any adverse effect on the beneficial or classified uses. This section gives the Colorado Water Quality Control Division greater flexibility to protect and maintain the quality of State waters. It is based on C.R.S. 1973, 25-8-102, 25-8-202(1), and 25-8-207(c).
The Colorado Water Quality Control Act requires the Commission to classify waters of the State. These regulations are intended to comply with the legislative intent as stated in C.R.S. 1973, 25-8-102(2):
"It is further declared to be the public policy of this state to conserve state waters and to protect, maintain, and improve the quality thereof for public water supplies, for protection and propagation of wildlife and aquatic life, and for domestic, agricultural, industrial, recreational, and other beneficial uses; to provide that no pollutant be released into any state waters without first receiving the treatment or other corrective action necessary to protect the legitimate and beneficial uses of such waters; to provide for the prevention, abatement, and control of new or existing water pollution; and to cooperate with other states and the federal government in carrying out these objectives."
In addition, the subject Regulations are consistent with the Federal Clean Water Act which states, in part: (Section 101(a))
"The objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation's waters...
C.R.S. 1973, 25-8-203(2) provides that the types of water classes shall be based on or intended to indicate relevant characteristics such as:
Such regulations are known as Classifications. C.R.S. 1973, 25-8-204 also requires that the Commission shall promulgate regulations which describe water characteristics or the levels of protection necessary to protect the beneficial uses. Such regulations are referred to as Standards.
In formulating the Regulations governing stream classifications, the Commission relied upon portions of the January 1974 Water Quality Standards and Stream Classifications, on the work of a broadly-based scientific committee which met publicly for several years, on testimony given at two oversight hearings and two series of public hearings, on workshops involving the public, and on documentary evidence including, but not limited to, the following:
More than thirty meetings, on notice to the public, were held during the formulation of these Regulations.
Section 303 of the Federal Act requires that water quality standards be established for every state. EPA will only promulgate such standards if the state does not promulgate acceptable water quality standards itself. Both the Federal and the State Acts require review of the water quality standards and stream classifications every three years. This review of the standards and classification system is pursuant to that required review.
With the exception of 3.1.4, these Regulations supersede those adopted in May, 1978. They May 1978 regulations superseded or were to phase out the January 1974 Water Quality Standards and Stream Classifications and the Temporary Stream Classification Exception Designated as Class C, effective October, 1976. As the Commission reclassifies State waters, previous classifications will be phased out. Those which have never been classified will be controlled by the Basic and Antidegradation Standards of these Regulations, by effluent limitations, and by classified uses in adjacent waters. Until such time as they are reclassified, streams which were classified under the previous system will be controlled by the limitations accompanying the previous system and all the factors mentioned above.
These Regulations establish basic water quality standards (called Basic Standards) which differ very little from the Basic Standards adopted in January, 1974. Previous Basic Standards stated that "the radioactivity of surface waters shall be maintained at the lowest practicable level and shall, in no case, except when due to natural causes, exceed the latest federal drinking water standard ..." . To further clarify the previous Basic Standards, the present Regulations set numeric standards for six radioactive substances. Four of the levels - Cesium 134, Radium 226, and 228, Strontium 90, and Tritium - are identical to those in the federal drinking water standards.
With Plutonium 238, 239, and 240, and Thorium 230 and 232, the numeric standards are consistent with a goal of keeping exposures below 4 millirems per year (the level suggested for other human-made radionuclides in the National Interim Primary Drinking Water Regulations. Because of the difficulty of removing these radionuclides by conventional treatment procedures, it is necessary and important to restrict treatment procedures, it is necessary and important to restrict their levels in the waters. Their potential adverse effect on human health suggests that extreme caution be exercised in their release to State waters. In addition to addressing radioactivity, Basic Standards set forth certain other minimum standards applying to all waters regardless of beneficial use(s). These Basic Standards (Section 3.1.11) are essential to a program designed to protect the waters of the State because they describe the fundamental condition that all waters must meet. All of the previously-cited evidence and testimony form the basis for the Basic Standards.
An Antidegradation Standard, required by state and federal law is included. It requires that the quality of the waters cannot be degraded so as to interfere with their present uses. Furthermore, certain high quality waters may be identified. Because of the special values of these waters, no parameters may be degraded (High Quality Water - Class 1), or may be degraded only when the Commission allows lower water quality as a result of necessary economic or social development (High Quality Water - Class 2).
Under the previous system (January 1974), waters were classified as A1, A2, B1, or B2. Waters designated A1 or A2 were defined as waters suitable or to become suitable for all purposes for which raw water is customarily used, including primary contact recreation. Waters classified B1 of B2 were defined similarly except they were not protected for primary contact recreation. A1 and B1 applied to cold waters and A2 and B2 to warm waters. The temperature classifications were consistent with characteristics for cold and warm water aquatic life. Because that classification system was not comprehensive, dissatisfaction was expressed by many including those being regulated and those doing the regulating. Therefore, a new system was devised where uses to be protected could be identified indivdually and levels for various parameters could be identified which would protect the specified use. Subsequently, a stream could be classified for as many of those uses for which it is presently suitable and those for which it is to become suitable within the next twenty years.
The Classification Subcommittee of the Water Quality Standards and Stream Classification Committee recommended the following classifications: Recreation (primary contact and secondary contact), Agriculture, Aquatic Life (Cold Water and Warm Water), Domestic Water Supply (two classes). The Subcommittee also recommended a Wildlife Classification for protection of critical wildlife areas. This classification has been dropped, however, in favor of a section entitled "Areas Requiring Special Protection" in which various special situations can be addressed on a case-by-case basis.
An Industrial classification and a Stock Watering Classification were considered and rejected by both the Subcommitte and the Commission. Regarding an Industrial classification, it was decided that water supply requirements for different industries vary so greatly that it would be virtually impossible to decide what parameters and what levels would be appropriate for such a classification. At the request of the cattle and dairy interests, the Agriculture classification was defined so that in addition to being suitable for irrigation, it would also be suitable for stock watering. The rationale was that it would be difficult to segregate the two uses. If, in specific areas, the waters are in fact segregated and numeric standards for those parameters to protect stock watering are not necessary, the Commission can respond by not assigning those standards to those waters.
The Aquatic Life classification went through a number of changes during the public hearing process and was eventually defined in terms of habitat. The temperature differentiation was retained resulting in cold and warm water categories under Class 1. The major change was a differentiation made between waters where the potential life forms are presently limited primarily to flow and stream bed characteristics rather than water quality characteristics. An additional classification was added primarily in response to federal requirements that high quality waters be identified in each state. This classification is appropriately entitled High Quality Waters (FORMERLY in two classes).
Stream classifications may either be upgraded or downgraded upon reclassification. Upgrading means that additional uses are identified and will be protected. Downgrading will eliminate one or more of the presently classified uses. A finding must be made by the Commission that the stream is not attaining that use and that such use is unattainable in a twenty-year period because of at least one of the conditions set forth. The first three conditions are essentially the same as the conditions for the Class C Exception under the previous system. The Class C was a temporary classification for the purpose of granting a temporary exception for one or more parameter levels otherwise in effect on a stream. The criteria, however, were of a very permanent nature and are now much more appropriately applied to the more permanent downgrading situation. To accommodate the agricultural industry, an additional criterion was established recognizing agricultural practices considered a satisfactory for the locality. The twenty-year time period for attainability was used because the areawide wastewater management plans (208 plans) are based on twenty years. The regulations also allow the Commission to find that the former classifications had no factual basis and therefore did not reflect actual beneficial uses and that this would be an additional reason for downgrading.
The concept of the previous Class C Exception is now incorporated into a section entitled Temporary Modifications. When a use classification is assigned to a stream, numeric standards may also be assigned to protect that use. When a numeric standard is not being met at the present time, a temporary modification to this numeric standard may be granted. All planning, discharge permits, new wastewater facilities and other water quality control actions are to be geared towards eliminating the need for the temporary modification. Such temporary modifications must be reviewed at least every three years and may be extended or removed. In general, requests for temporary modifications are preferred over the more permanent downgrading. They serve as reminders that conditions are correctable and may increase the priority for funding to attain the classified use and the underlying numeric standard.
In addition, there are Qualifiers which may be appended to a use classification to indicate special considerations. The "Goal" qualifier indicates that the waters are presently not fully suitable for such use. The "Seasonal" qualifiers indicates that the water may only be suitable for the classified use during certain periods of the year. The "Interrupted Flow" qualifier indicates that while flow may be interrupted, the flow conditions still permit the classified use during periods of flow. The expanded use classification, the upgrading and downgrading provisions, the temporary modifications and the qualifiers make this system far more flexible than the previous system.
All waters of the State will be classified under this regulatory system through a process which provides for public notice and a public hearing before any classification of numeric standard is assigned. Whenever possible, the Commission will hold the public hearing in the general locality of the waters being classified. All classifications, standards, and temporary modifications will be assigned by the Commission by rule after consideration of all available data and evidence presented at the hearings, and can be changed only by a new rulemaking decision. Numeric standards will be assigned when there is documentation showing that a particular numeric level is appropriate for protecting the classified use. Standards may be set for an entire stream or for one or more segments thereof. Standards may be assigned at the time classifications are assigned or at any time thereafter, this is intended to be a dynamic process so that new standards may be adopted on a regular basis as the supporting information becomes available. The scientific and technological rationale for the standards will be developed from information obtained at the classification hearings.
Public participation in the process is always encouraged. A change in a classification, standards, or temporary modification may be sought at any time; however, it is within the discretion of the Commission to decide whether or not to consider the proposed change. In any case, all classifications, standards, and temporary modifications must be reviewed every three years.
The establishment of classifications and standards is based on the long-established fact that natural waters have a limited ability to assimilate wastes without rendering the water unfit for various beneficial uses. The quantity of pollutants that can be assimilated by a stream or water body is directly related to the quantity of water available for dilution and assimilation. Stream flows and levels change during the year and from year to year. Extremely low flows or water levels may not provide enough dilution water to assimilate the pollutants which, under normal or high flows, would not impair the assigned uses; therefore, it is reasonable to establish a flow below which the water quality standards assigned to State waters are not in force. This low flow or water level is commonly accepted as the "minimum annual average seven-consecutive-day flow expected to occur once in ten years" - 7-day 10 year low flow. The 7-day 10-year low flow may be determined by various statistical analyses of stream flow records covering at least ten years.
The Regulations also permit a seasonal average low flow rather than an Annual average low flow. A seasonal average low flow, for instance, may result in a less restrictive discharge permit requirement for ammonia in the winter because of the toxicity relationship to temperature and pH.
Another concept which uses the dilution and assimilative capacity of a stream and may result in a less restrictive discharge permit requirement is the "mixing zone". A mixing zone is intended to serve as a zone of initial dilution in the immediate area of a discharge. The water quality standards assigned to the receiving waters are not in effect in the mixing zone. The Division designates the mixing zone on a case-by-case basis in accordance with the criteria established in the Regulations, Section 3.1.9 . The mixing zone is well explained in that section and further information can be found in the Federal Water Pollution Agency's Water Quality Criteria 1968, p. 31.
Attached to the Regulations are three tables showing numeric levels for various parameters. The Tables are not adopted as regulations. The numeric levels set forth in the Tables are levels established by the commission after careful analysis of all available information and are generally considered to protect the beneficial use classifications of the waters of the state. They are intended to guide the commission and others at the use classification and numeric-standard-setting hearings. They carry no presumptive validity or applicability. Numeric standards may not be assigned for all the parameters listed in the Tables, and conversely, standards may be assigned for parameters which are not listed in the Tables.
5 CCR 1002-31.20