5 Colo. Code Regs. § 1002-31.37
The provisions of 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; 25-8-209 and 25-8-402 C.R.S. 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:
The current Colorado manganese table value was adopted in 1997. It was based on data available at that time that demonstrated the mitigating effect of water hardness on manganese toxicity to a variety of aquatic species, including brook and brown trout. Subsequent to the adoption of the hardness-based table value by the Commission, additional acute and chronic toxicity tests were conducted by the Division of Wildlife (DOW) on rainbow trout. Inclusion of the rainbow trout data results in a more accurate aquatic life manganese table value for Colorado.
The Climax Molybdenum Company (CMC) proposal was developed using EPA's Guidelines for the Derivation of Ambient Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses. EPA recommends the use of regression analysis in evaluating concentration-effect relationships for toxicity data to be used in criteria derivation. In EPA's most recent ambient water quality criteria (1999 revision for ammonia) it recommends the use of a 20 percent effect concentration (EC 20) as the appropriate endpoint for evaluating chronic toxicity. This was the approach originally proposed by CMC. The DOW expressed concern that the result of this methodology would not be protective enough for Colorado. The DOW recommended that a more restrictive 10 percent effect concentration be used. CMC agreed to revise its proposal to accommodate this concern but noted that this may require the consideration of site-specific manganese standards in one case. The Commission adopted the modified proposal.
The Farmers Reservoir and Irrigation Company (FRICO) advanced two alternative proposals for consideration in this rulemaking hearing. The first alternative would have added a footnote to section 31.16 , addressing the relationship of table value criteria to site-specific standards. The second alternative would have added new table value criteria for the agriculture classification for fecal coliform, nitrate and phosphorus. In its prehearing statement, FRICO withdrew the proposal for the adoption of nitrogen and phosphorus standards to protect agricultural canals and reservoirs from eutrophication, in view of EPA's current effort to develop nutrient criteria.
Based upon the evidence submitted in this rulemaking, the Commission has decided not to adopt either proposal advanced by FRICO.
With respect to the proposed footnote for section 31.16 , the proposed first sentence appears to be a restatement of language in section 31.7 of the regulation, while the second sentence appears to be inconsistent with language in section 31.7 . The Commission has determined that the proposed footnote is not necessary or appropriate at this time.
The Commission also has determined that the addition of table values for the agriculture use is not necessary or appropriate at this time, particularly where the function of such table values would be only to protect a limited subclass of that use. The Commission does not believe that the evidence regarding potential impacts on crops from nitrate levels above 5.0 mg/l is strong enough to warrant inclusion of a new table value. Moreover, the existing provisions of the Basic Standards, including section 31.13 and section 31.7 , provide authority for the Commission to adopt site-specific standards to protect sensitive crops should that be determined necessary and appropriate in particular circumstances.
The Commission also considered the potential risk to agricultural workers of fecal coliform in irrigation water. The Commission has concluded that the evidence available at this time does not indicate that agricultural workers are faced with a risk greater than that associated with a recreation class 2 classification. Since all surface waters are classified either class 1 or class 2 recreation, the Commission has determined that the effect of such classifications serves to protect agricultural workers and that consequently there is no need for a separate fecal coliform table value for the agriculture.
The Commission received conflicting evidence in this rulemaking regarding the potential economic costs and benefits of compliance with water quality standards that might result from the implementation of the proposed new Basic Standards provisions. In view of the lack of an adequate demonstration that the proposed changes are necessary or appropriate to protect agricultural uses, as described above, the Commission has concluded that the benefits of adopting such changes would not bear a reasonable relationship to the potential costs of compliance with resulting requirements.
The City of Thornton proposed that the Commission adopt a new "wastewater treatment plant effluent-dominated" sub-classification under the water supply classification. Thornton also proposed that the Commission adopt numerical table values for fecal coliform, nitrate, phosphorus and total organic carbon (TOC) that would apply to this new sub-classification. Thornton's prehearing statement dropped the proposal for a fecal coliform table value.
Based upon the evidence submitted in this rulemaking, the Commission has decided not to adopt the Thornton proposal.
The Commission does not believe that the evidence submitted demonstrated the need for a separate water supply sub-classification at this time. From the available information, it does not appear that the conditions proposed by Thornton in which the new sub-classification would apply occur frequently enough to warrant the creation of an entire sub-classification and associated table values. Moreover, the existing provisions of the Basic Standards, including section 31.13 and section 31.7 , provide authority for the Commission to adopt site-specific standards to provide additional protection for specific water supplies, should that be determined necessary and appropriate in particular circumstances.
The Commission also does not believe that the evidence submitted supports the adoption of the table values proposed by Thornton. With respect to nitrate, Thornton provided no convincing evidence that water with nitrate levels between 5 mg/l (Thornton's proposed table value) and 10 mg/l (the existing water supply table value) poses a significant public health risk. Moreover, there was no evidence provided that a population being served by a water source that is "wastewater treatment plant effluent-dominated" is more susceptible to nitrate than the general public. With respect to phosphorus, the table value proposed by Thornton is based on limited site-specific experience and does not warrant the adoption of a statewide table value.
The Commission believes that the potential public health issues associated with TOC should be investigated further. However, the evidence submitted in this hearing does not warrant the adoption of the proposed TOC table value at this time. The evidence does not demonstrate that TOC present in effluent poses a greater risk than TOC from other sources. Moreover, Thornton has not demonstrated that its proposed TOC limit of 2 mg/l above background is necessary to avoid interference with its treatment processes. The potential usefulness of TOC as an indicator for the presence of organic pollutants is worthy of further examination; however, the Commission has concluded that the existing science does not support Thornton's position on this issue.
The Commission received conflicting evidence in this rulemaking regarding the potential economic costs and benefits of compliance with water quality standards that might result from the implementation of the proposed new Basic Standards provisions. In view of the lack of an adequate demonstration that the proposed changes are necessary or appropriate to protect water supply uses, as described above, the Commission has concluded that the benefits of adopting such changes would not bear a reasonable relationship to the potential costs of compliance with resulting requirements.
This rulemaking hearing addressed a number of potential revisions to this regulation that were identified in a January, 2000 triennial review informational hearing. Many of the revisions proposed for this rulemaking and ultimately adopted by the Commission grew out of the efforts of the Colorado Water Quality Forum's Basic Standards Work Group, which provided important input to the Water Quality Control Division as it developed its proposals for this rulemaking. Each of the major revisions adopted by the Commission is addressed below.
Over the last several years, the Commission has had several discussions regarding how best to use the water quality standards system to encourage improvement - or not discourage such improvement - for waters impacted by historical mining activities. The Commission has felt that neither of the primary options set forth in the Basic Standards - table value standards or ambient quality-based standards - are the best possible fit for many of these situations. To provide additional options, the Commission adopted language in a new subsection (c)(ii) of section 31.7(1). This new subsection explicitly provides that a site-specific narrative standard may be adopted on a site-specific basis to address waters impacted by historical mining activities where improvement is believed to be attainable. The new provision would include numerical temporary modifications based on existing ambient quality.
This approach could be applied where a use attainability analysis has not yet been conducted, but the Division or other interested parties intend to conduct such an analysis. It would provide that the underlying standards for a segment would be either the results of such an analysis if completed and approved by the Commission, or - if a use attainability analysis is not completed by a specified date -table value standards. This option would provide an incentive for timely completion of a use attainability analysis, while assuring that protective standards will be in place if such an analysis is not completed. An appropriate date will be identified when a narrative standard is adopted for a particular segment, based upon the amount of time needed to complete a site-specific use attainability analysis.
The Commission is aware of the fact that situations may exist where a use attainability analysis for such impacted waters has been completed, and though feasible improvement measures have been identified, uncertainty remains regarding the chemical, biological, and/or physical conditions that will be achieved once those measures have been implemented. Though the Commission considered the adoption of a narrative standard option which would have equated the standard with that concentration or condition realized after the improvement measures were complete, it decided that this concept was adequately addressed within the state's temporary modification provisions, with specific reference to the newly adopted language found in section 31.7 . That section addresses situations where significant uncertainty exists. In other words, a temporary modification could be utilized until such time as the results achieved from the implementation of the improvement measures provide a clear indication of the appropriate long-term standard.
The Commission believes that this site-specific narrative standard option should make the water quality standards system more consistent with efforts to remediate state waters degraded by historical mining activities. The new language is specific to waters impacted by historical mining activities because this is the type of situation that has presented a concern regarding the restrictions of the previous options for water quality standards. Other instances where current impaired water quality exists, such as the segments listed on the section 303(d) list, may bring into play a variety of considerations that differ from the unique circumstances associated with waters impacted by historical mining activities that the Commission has determined warrant the new site-specific narrative standard option. If it is determined that other categories of circumstances warrant a similar site-specific narrative standard option, revised or additional provisions can be considered in future reviews of this regulation.
In addition to the language in new subsection 31.7 regarding historical mining sites, the Commission has added language in a new subsection 31.7 , clarifying the Commission's more general authority to adopt site-specific narrative standards in appropriate circumstances. A variety of site-specific narrative standards have previously been adopted by the Commission where warranted by specific circumstances. It is appropriate for the Basic Standards to recognize this option.
The traditional situation for adopting a temporary modification has been where an underlying numerical water quality standard currently is not being met, but it is believed that the conditions causing the exceedance can be corrected within a 20-year period so that the underlying standard that is protective of the use will be attained. However, over time the Commission has used temporary modifications as a helpful regulatory tool in circumstances that go somewhat beyond this original specific situation. In particular, temporary modifications have been adopted in certain circumstances where there is uncertainty as to whether existing water quality is caused by natural or irreversible conditions, or where there is uncertainty about the level of water quality needed to protect the classified uses of a water segment. In this rulemaking, the Commission adopted revisions to section 31.7 to explicitly provide that "significant uncertainty regarding the appropriate long-term underlying standard" is a basis for establishing a temporary modification.
Previous language in section 31.7 and section 31.14 provided that, whenever a temporary modification has been adopted, discharge permits and other applicable control requirements should include provisions aimed at eliminating the need for the temporary modification. In this rulemaking, the Commission adopted revisions to these provisions to recognize that in instances where a temporary modification is adopted based on uncertainty as to the appropriate underlying standard, it may not be appropriate to expect control actions aimed at achieving the underlying standard until the uncertainty is resolved.
In this rulemaking, the Commission adopted a number of revisions to the Antidegradation Review Process provisions of section 31.8(3). Several changes have been adopted in the "Significance Determination" provisions in subsection 31.8 . This subsection has provided that an activity will not be considered to result in "significant degradation" if any of four tests are met. If it is determined that an activity would not result in significant degradation, then no further antidegradation review is required. The Commission restructured these significance tests. The test based on 10 percent of the existing load has been revised to apply specifically to bioaccumulative toxic pollutants, since this is the major category of pollutants for which "load", rather than merely "concentration" , plays a key role. The Commission has selected a bioaccumulation factor (BAF) of 1000 as the threshold above which this test would apply. By placing an "and" at the end of this revised subsection, this loading test is required to be met whenever bioaccumulative toxic pollutants are present in order to determine that a new or increased loading is not significant.
The remaining significance tests would now apply in the case of new or increased loadings of all pollutants. In order to assure that successive new loadings to a segment do not result in an impact that is cumulatively significant without an antidegradation review occurring, the concentration-based "15 percent of the available increment" test has been modified. The revised language provides that where the cumulative impact of discharges would increase the low flow pollutant concentration by more than 15 percent, any new or increased loading would not be considered insignificant based on this test.
The Commission has added language to the regulation specifying that the load and concentration-based significance tests apply to "the portion of the segment impacted by the discharge". The Commission recognizes a need to further define this term as utilized in the new regulatory language. It has been included, in part, to address concerns over future loading to those segments which currently include in their description "all tributaries thereto". The Commission directs the Division to work with the regulated community in an effort to further define this concept as a part of the work group process established to develop a new antidegradation guidance document.
The Commission believes that these significance tests warrant additional consideration in the future. In particular, a question has been raised whether the presence of "100 to 1" dilution alone should result in a conclusion that a new or increased loading is not significant, if the concentration-based increment is exceeded. Secondly, additional consideration should be given to whether there are pollutants other than bioaccumulative toxics for which cumulative loads are an important consideration, even when concentration thresholds are not exceeded. The Commission requests that the Division and other interested persons explore these issues further prior to the next triennial review and bring a recommendation back to the Commission at that time as to what, if any, additional revisions to the regulation should be considered to address these concerns.
The Commission also adopted additional language with respect to the "temporary or short term changes" significance test, to assure that this "off-ramp" is not applied where the long-term operation of a regulated activity will result in an adverse change in water quality. Any such impacts should not be considered temporary or short term.
The Commission added a new subsection 31.8(3)(g), entitled "Protection of Existing Uses" . This new subsection merely places in the regulation a provision previously contained in Commission Policy 88-1, providing that a rulemaking hearing will be held to consider adoption of an additional water quality classification for a water segment if it is determined during an antidegradation review that an existing use of the segment has not been classified. This policy was originally adopted in response to a concern raised by EPA regarding the antidegradation provisions adopted by the Commission in 1988. The Commission determined that it would reduce the confusion that has existed regarding the scope of this policy to incorporate this provision into the regulation, eliminating the need for a separate policy. Therefore, by this action the Commission also is repealing Policy 88-1 as a separate policy document.
The Commission revised the references to "activity" throughout this section to refer to "regulated activity" , for consistency with the terminology used in subsection 31.8 . In addition, a reference in this subsection to "control regulations existing as of April 30, 1993" was deleted since it appears that this language is no longer necessary.
An extensive list of statewide numerical standards are established in the table entitled "Basic Standards for Organic Chemicals", which is contained in section 31.11(3) of the regulation. Two specific issues regarding these standards were addressed in this rulemaking. First, many of the standards are based upon EPA-established drinking water standards, under the federal Safe Drinking Water Act, or water quality criteria developed pursuant to section 304(a) of the federal Clean Water Act. Since these standards and criteria are modified from time to time, it is necessary to review the existing Colorado standards in comparison to the latest available information. As a result of this review, the Commission adopted several revisions to the standards to conform with the latest available information as to protective levels for the various chemicals.
Second, the Commission modified the human health-based criteria set forth in this table to refine how these criteria apply to individual water segments. Specifically, the Commission has established three human health-based standards columns (water supply only, fish consumption only, and water + fish consumption) in the table. The standards in these three columns will apply to individual water segments based on whether (a) a water supply classification, (b) a class 1 aquatic life or class 2 with recurring fishing, or (c) both of these classifications/circumstances is present, respectively. A similar change has been made to Table III. The Commission believes that these revisions result in a system that provides more appropriate human health-based water quality standards for individual circumstances, minimizing the potential for under-protection or over-protection.
In comments submitted for this rulemaking, EPA expressed concern that Colorado's proposed standards for certain "Group C Chemicals" are not adequately protective since they are not based on the potential carcinogenicity of these chemicals. The chemicals in Group C have been identified by EPA as "possible human carcinogens" due to the limited nature of the data regarding carcinogenicity. The Commission's Policy 96-2, regarding Human Health-based Water Quality Criteria and Standards, sets forth a policy approach not to base standards for Group C chemicals on carcinogenicity. The Commission has chosen to continue to apply its established policy approach in this hearing. EPA has recognized that it is the prerogative of states to choose an appropriate level of risk in setting water quality standards. This action by the Commission is a determination that the risks of carcinogenicity of Group C chemicals do not warrant standards based on carcinogenicity at this time. If EPA decides that the evidence of carcinogenicity for the chemicals in question warrants re-classifying them as Group B "probable human carcinogens" , then Colorado's standards will be revised accordingly. Until then, or until the Commission should decide to modify its current standard-setting policy for this category of chemicals, the action taken here is an appropriate state consideration of risk levels in adopting water quality standards.
In this rulemaking the Commission adopted revisions to the provisions in subsection 31.13(1)(a) regarding recreation use classifications and to the Table I water quality criteria for recreation uses. Several revisions were adopted to the provisions regarding recreation classifications. First, the Commission subdivided the class 1 classification into "class 1a" for waters with existing primary contact uses and "class 1b" for potential primary contact uses. As reflected in the associated numerical criteria in Table I, the Commission believes that it is appropriate to provide a higher level of protection for those water segments where primary contact uses are actually occurring.
Reflecting the federal requirement that water quality be protected at a level adequate for "recreation in and on the waters" unless it is demonstrated that such uses are not attainable, the revised regulation provides that the Commission shall assign a class 1a or class 1b classification to all surface waters unless a use attainability analysis demonstrates that there is not a reasonable potential for primary contact uses to occur in the waters in question within the next 20-year period. The Commission is requesting that the Division develop a Recreation Use Attainability Analysis Guidance Document that could be used by any person wishing to conduct such a use attainability analysis. This guidance document should be developed with public input, including a public briefing to the Commission that provides an opportunity for public comment to the Division.
The revised regulation also provides that where no use attainability analysis supporting a class 2 classification has been completed, the new class 1a will be the default classification, unless a reasonable level of inquiry has failed to identify any existing class 1 uses of the water segment. Where such an inquiry fails to identify existing recreation uses, a class 1b classification will be appropriate. This approach should help assure that primary contact uses are protected. The Commission intends that what constitutes a "reasonable level of inquiry" will be a case-specific determination, which will depend on factors such as the size and location of the segment in question and what is known about the presence or absence of primary contact uses for other, similar water segments. It generally will be appropriate to direct inquiries to a variety of persons in the area with potential knowledge regarding uses of the water segment, such as to land owners, land management agencies, local governments, recreational user groups, and/or Riverwatch coordinators or other school contacts.
The Commission intends that any revisions of existing recreation classifications and standards to apply the new classifications described above would occur through the normal rulemaking process, which would provide an opportunity for public review of and comment on information supporting any new site-specific classifications and standards. Proposed changes generally are identified in attachments to the rulemaking hearing notice, with any alternative proposals to be considered identified in parties' prehearing statements.
The discussions that led up to this rulemaking hearing included consideration of options that would have included additional subcategories of the recreation use classifications. Although additional subcategories are not being adopted at this time, such options may be considered further in subsequent triennial reviews. The Commission requests that the Division and other interested persons develop additional information regarding the usefulness or appropriateness of such subcategories for consideration in subsequent reviews.
The primary change adopted with respect to the Table I water quality criteria for recreation uses is the addition of Escherichia coli (E. coli) as a pathogen indicator. Available studies indicate that E. coli, which is a subset of fecal coliform, is a better predictor of potential human health impacts from waterborne pathogens. For now, the Commission also has retained fecal coliform table values. The Commission intends that during the next triennium alternative fecal coliform and E. coli numerical standards will be adopted for water segments in the individual basins. The Commission wants the public to be aware that it currently anticipates moving to E. coli as the sole pathogen indicator in the next triennial review of this regulation. Dual standards are being established in the interim as a transitional step. One reason for adopting this transitional approach is that at present there is uncertainty regarding the acceptability and comparability of several alternative E. coli monitoring methods. The Commission is hopeful that much of this uncertainty may be resolved prior to the next triennial review.
As stated in the revised footnote 6 to Table I, so long as dual standards are in place for a water segment, the Commission intends that dischargers will have the option of either parameter being used in establishing effluent limitations in discharge permits. This footnote further clarifies that for the evaluation of ambient water quality data, such as in making section 303(d) listing decisions, in the event of a conflict between fecal coliform and E. coli data, the E. coli data will govern. The Commission believes that these provisions will help ease the transition from fecal coliform to E. coli standards.
The E. coli criterion adopted for new recreation class 1a is 126 per 100 milliliters. This level is based on EPA criteria recommendations, which are derived from an anticipated risk level of 8 swimmer illnesses per 1000 swimmers. The class 1b criterion of 205 per 100 ml is based on a policy decision to accept a higher risk level - 10 illnesses per 1000 swimmers - for this classification, based on the assumption that primary contact uses are not currently likely to be occurring for these water segments, although such uses may be a potential in the future. The E. coli criterion for class 2 waters is set at 630 per 100 ml, based on an EPA policy recommendation that the criteria for secondary recreation uses not be set higher than five times the primary use standard.
During this transition period, the previous class 2 fecal coliform criterion of 2000 per 100 ml is retained. The previous class 1 fecal coliform criterion of 200 per 100 ml is adopted as the value for the new class 1a. Finally, a fecal coliform level of 325 per 100 ml has been established for the new class 1b, based upon interpolation between the 200 and 2000 values, to be consistent with the new E. coli value for class 1b.
The revised footnote 6 to Table I clarifies that compliance with fecal coliform and/or E. coli standards is to be based upon the geometric mean of representative samples. EPA has recommended that states consider the adoption of single sample maxima for bacteriological indicators, in addition to standards based on geometric means, to provide additional protection of recreation uses. The Commission has declined to adopt such criteria at this time, due in part to uncertainty regarding the significance of and the appropriate response to elevated single sample test results. An important aspect of this concern is the substantial variability that can be common in individual bacteriological samples, because bacteria are not uniformly distributed in water samples, since they behave more like suspended particles, rather than dissolved constituents. Repeat testing on such samples can yield results which vary substantially.
However, the Commission may consider the adoption of single sample maxima or other short-term indicators in the next triennial review. Another approach to short-term indicators that has been suggested would be to provide that no more than "x" percent of samples could exceed a specified level. The Commission requests that the Division and other interested persons develop additional information regarding the usefulness or appropriateness of such short-term bacteriological criteria prior to the next triennial review, including identifying potential criteria values.
The issue of whether and how to account for animal waste in setting recreation standards is a challenging one. Relatively little information is available at present regarding the risks posed by animal sources. Moreover, the range of natural sources - such as waterfowl and terrestrial wildlife - and anthropogenic sources - both urban (pets) and rural (livestock) - present a variety of management challenges with respect to potential options for controlling or mitigating water quality impacts. Therefore, the Commission anticipates that this issue will need to be closely monitored and revisited over the next several years. As a matter of policy, the Commission chose at this time not to include any language in the standard itself - or the accompanying footnote - regarding non-human sources of coliform bacteria.
With respect to non-human sources, the Commission intends that the fecal coliform and E. coli standards will be applied in a manner consistent with EPA's current official guidance, which is contained in the Water Quality Standards Handbook, Second Edition, August, 1994, page 2-3.
In adopting these provisions, the Commission recognizes that the state of knowledge regarding the potential risks posed by non-human sources of coliform bacteria is evolving. The EPA criteria generally were developed based upon evidence of risks posed by human sources. However, there have been recent examples of human health impacts resulting from water contamination by at least some non-human sources, and EPA currently is considering substantial changes to its guidance regarding the use of bacterial water quality criteria for the protection of recreational uses. The Commission believes that the approach adopted here is a reasonable policy choice based on current information. However, the issue of non-human sources will need to be reevaluated in subsequent triennial reviews as additional information becomes available.
Finally, the Commission wishes to emphasize that ingesting water from streams and other surface waterbodies has inherent risks and is not encouraged, but rather should be avoided to the extent possible during all forms of recreation. While the Commission believes that the criteria adopted here provide a reasonable and appropriate level of protection of human health, avoidance of ingestion is always preferable.
In December of last year, EPA published its 1999 Update of Ambient Water Quality Criteria for Ammonia. This update is a modification of the 1998 Update of Ambient Water Quality Criteria for Ammonia. Colorado's current table value criteria for ammonia in the Basic Standards were adopted in the late 1980's, following an extensive review of EPA's then-current criteria by a Colorado panel of scientific experts. The recommendations of this panel were set forth in a draft final report entitled Proposed Nitrogenous Water Quality Standards for the State of Colorado, dated March 12, 1986, prepared for the Water Quality Control Commission by the Nitrogen Cycle Committee of the Basic Standards Review Task Force.
In view of the complex set of issues relating to ammonia criteria and standards, and the need to assess the appropriateness of EPA's revised criteria for conditions in Colorado, the Commission decided not to consider changes to the current Colorado ammonia criteria in this rulemaking hearing. Rather, the Commission believes that it will be important for the Division to work with the regulated community and other interested persons to examine the new EPA criteria and develop recommendations for any revisions to the current Colorado criteria and standards that may be appropriate. In order to provide a meaningful opportunity for such an informal process to occur, the Commission anticipates revisiting the ammonia criteria issue in the next triennial review of the Basic Standards and Methodologies for Surface Water.
Tables II and III of this regulation include table value criteria for a "water supply" use for four parameters (chloride, sulfate, iron and manganese) that are based on "secondary" drinking water standards developed pursuant to the federal Safe Drinking Water Act. These secondary standards are not health-based, but rather are based upon "welfare" impacts such as taste, odor and discoloration of laundry or fixtures. They are established by EPA as goals for public water supplies and are not required to be enforced by states.
Prior to this rulemaking, the Commission generally applied these four table values as numerical standards for all water segments classified for water supply use, except where site-specific information justified a different standard, e.g. based upon higher naturally occurring levels of the parameter in question. For some time, dischargers have expressed concern about the cost of meeting effluent limitations resulting from the sulfate, iron and manganese secondary drinking water standard-based stream standards, since the secondary standards are not enforceable against water suppliers and are not health-based, and since treatment of wastewater to remove these constituents is generally expensive and difficult. (Similar practical concerns do not seem to have arisen with respect to chloride standards.) On the other hand, although the secondary standards are not enforceable against water suppliers and are not health-based, water suppliers have indicated that due to the needs of their customers it is important to them to minimize these constituents in their source water, and there is a cost to the water suppliers if they need to treat to remove these constituents. Several water suppliers have experienced problems with ambient manganese levels in the past, and have had to add additional treatment steps to remove manganese.
In an effort to balance these considerations, as a result of this rulemaking the Commission is adopting a change to its approach to establishing numerical standards for sulfate, iron and manganese. (No change is being adopted with respect to chloride standards, since it does not appear that there are practical concerns with the current approach to chloride standards.) There are several components to this action:
- Existing numerical standards for all surface water segments that are based on the water supply table values for sulfate, iron and manganese will be deleted in a rulemaking hearing addressing water quality standards for all river basins;
- Existing segment-specific numerical standards for sulfate, iron and manganese that are based on previous site-specific analysis (e.g., identifying higher naturally occurring levels of a constituent) will be retained;
- For segments with a water supply classification that have an actual water supply use (as opposed to a potential use), the Commission is adopting numerical standards based on the less restrictive of (a) existing quality as of January 1, 2000, or (b) the water supply table value criteria for iron, manganese, and sulfate;
- For segments with a water supply classification that do not have an actual water supply use, no numerical standards for sulfate, iron and manganese will be established unless determined to be necessary and appropriate in accordance with section 31.7 as the result of a future site-specific rulemaking;
- For purposes of implementing water supply-based numerical standards for iron, manganese and sulfate into discharge permits, a new provision is added to section 31.14 to direct the Division to give credit in establishing effluent limitations for potentially elevated levels of these constituents in the water entering the wastewater treatment plant or other discharging facility, where the source is ambient surface or ground water tributary to the receiving waters that is no worse than existing quality as of January 1, 2000.
The Commission believes that this set of actions provides the most efficient and reasonable starting point for water supply-based sulfate, iron and manganese standards to provide appropriate protection of actual water supplies against the introduction of new or increased sources of these constituents while also minimizing the risk of costly, unnecessary treatment by point source dischargers. The Commission has essentially "grandfathered" existing levels of these constituents (where they exceed table values) as the numerical standards for segments with an actual water supply use. A proviso has been included to assure that existing contamination levels are not grandfathered if they result from an unauthorized discharge with respect to which the Division has undertaken an enforcement action or if they conflict with remedial action requirements for these constituents established pursuant to any response action under the Comprehensive Environmental Response Compensation and Liability Act. Of course, the numerical standards being established by these revisions to the Basic Standards could be revised to be more or less stringent in a subsequent site-specific standard-setting hearing if determined appropriate based on the site-specific evidence. In some cases, where iron and manganese levels are elevated due to historic mining activities, use of the new site-specific narrative standard option discussed above may be appropriate.
The Commission intends that, consistent with established practice, the "existing quality" of particular segments for the parameters in question will be determined based upon the 85th percentile of available representative data.
At the same time, the Commission has determined that there is no need for statewide water supply-based sulfate, iron and manganese standards for segments with a water supply classification but no actual water supply use - i.e., those segments classified as water supply based on a potential future use. Where there is no actual use in place that could be impacted by a discharge, the Commission does not believe that dischargers should need to treat for these secondary drinking water standard-based stream standards. If an actual use for a water supply-classified segment begins in the future, then the numerical standards being adopted as a result of this rulemaking would apply - i.e., existing quality as of January 1, 2000, or table values, whichever is less restrictive. In such circumstances, the Commission expects that the Division would allow a reasonable compliance schedule in issuing or renewing discharge permits.
The Commission has provided that an "actual use" will be determined based on use of the surface waters from the segment in question or use of hydrologically connected ground water. The Commission intends that an actual use of ground water would receive protection where its quality could be impacted by the quality of the surface water in question. Any situation for which it is determined that there is no reasonable potential for the surface water quality to affect the quality of ground water used as water supply should not be considered to involve "hydrologically connected ground water".
The Commission recognizes that today's action could result in numerical standards for sulfate, iron and manganese applying in a segment with a water supply use classification that has an actual water supply use, but where the only water supply intake(s) are located upstream from any point source discharge(s) to that segment. In these circumstances, if it appears that there are no downstream actual water supply uses potentially impacted by the discharge(s), it would be appropriate for the Commission to re-segment the stream in question so that the numerical standards now being established through the Basic Standards apply only upstream of the water supply intake.
The Commission recognizes that it is not possible to anticipate and account for all potential site-specific factual situations in a statewide rulemaking action such as this. Therefore, the Commission has retained the option of adopting site-specific water supply-based numerical standards for sulfate, iron and manganese that may be more or less stringent than those being adopted here wherever determined appropriate in a site-specific rulemaking proceeding. Moreover, the Commission intends to revisit this action in subsequent triennial reviews of the Basic Standards, to determine whether it is working effectively as intended or may need future refinement. If it is determined that this action results in significantly increased costs for water suppliers, especially in light of significant new Safe Drinking Water Act requirements for additional treatment of public water supplies, the Commission believes that more protective standards should be re-established.
Two sets of changes are adopted with respect to the metals table values set forth in Table III. First, the Commission has adopted language to clarify use of the hardness-based equations in calculating standards, to provide consistency between current practice, this regulation and EPA guidance. The Commission added language to footnote 3 to Table III to explicitly state the limitations on using the hardness-based metals equations in that table. These equations are to be used with hardness values no greater than 400 mg/l, as calcium carbonate, even if the ambient conditions are greater than this range. The data that were used to derive these equations were generally based on toxicity tests in waters with hardness ranging from 50 mg/l to 200 mg/l. The cap at 400 mg/l hardness limits the extent that the equations are extrapolated beyond the original data where the slope of the LC50's flattens out. The previous practice of using a lower limit of 25 mg/l is inappropriate, since there is no evidence that the toxicity does not continue to increase as hardness decreases below 25 mg/l (i.e., the slope remains constant at low hardness).
Adding this clarification in the Basic Standards does not preclude the use of site-specific studies, such as developing a "water effects ratio" to demonstrate that lower toxicity occurs at higher hardness levels in specific circumstances. The Commission is concerned with the current uncertainty regarding toxicity at higher hardness levels that results from available EPA criteria. The Commission encourages EPA to undertake additional studies of the metals in question at higher hardness levels, to reduce this uncertainty and improve the accuracy of the criteria in the future.
Second, the Commission modified the hardness-based table value criteria for several metals to incorporate appropriate "conversion factors" . The need for these conversion factors results from the fact that the table value criteria originally were developed based on "total recoverable" metals levels, but are now applied as "dissolved" metals standards. Because the dissolved fraction of a metals sample is a subset of total recoverable metals, application of the conversion factors is necessary to assure that metals standards are not under-protective. The revised criteria should more accurately reflect potential toxicity to aquatic life.
Concern was expressed in the hearing regarding application of the revised selenium table values that result from application of the conversion factors. Where selenium data is available only reported to the nearest whole number, the Commission intends that this be taken into account in assessing compliance with the revised table values.
The Commission also added a new Table IV to the regulation, identifying metals levels associated with a range of hardness values, for those metals with table value criteria in the form of hardness-based equations. The Commission has included language in the introductory portion of section 31.16 to clarify that where the hardness-based equations in Table III are applied as "table value" water quality standards for individual water segments, those equations - rather than the values set forth in Table IV - define the applicable numerical standards. The illustrative examples of approximate metals values associated with a range of hardness levels in Table IV are intended solely as an aid to persons using this regulation, for informational purposes only.
The Commission corrected a number of clerical errors that had been identified in this regulation.
PARTIES STATUS/MAILING LIST STATUS TO THE RULEMAKING HEARING
5 CCR 1002-31.37