5 Colo. Code Regs. § 1002-31.48
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:
Background: In 2000, the Commission added "type iii" temporary modifications to section 31.7 to recognize that uncertainty regarding the underlying standard was an appropriate use of temporary modifications (see Statement of Basis, Regulation #31, at section 31.37 , IV C,). In 2005, the Commission further revised section 31.7 to remove the distinction between the types of temporary modifications, clarify the durations of temporary modifications, and institute an annual review of temporary modifications. One of the primary purposes of these revisions was to focus attention on ending the need for the temporary modification as soon as possible (see Statement of Basis, Regulation #31, 31.44, I. D). These revisions resulted in a significant change in the Division's approach to temporary modifications, primarily in limiting the use of temporary modifications to situations where there are point source discharges that face unreasonable outcomes.
During the time that Colorado's temporary modifications regulatory provisions have been changing, EPA has also revised its policy regarding permit compliance schedules. Previously, it was thought that compliance schedules could be no longer than the term of the permit. This meant that attainment of underlying water quality standards had to occur by the end of the five-year permit term. EPA has recently revisited the issue and now says that compliance schedules can extend past the end of the permit term.
In the last few years, the Division has implemented the revised provisions both in the regularly scheduled basin hearings and in the new annual temporary modification review hearings. Various parties have expressed concern about the new practices. The current changes are the result of Standards Framework Work Group dialogue.
Organizational Revision of Section 31.7: The current 31.7(4) was deleted and the contents moved to other sections in 31.7. Overview language that was previously at subsection 31.7 was moved to the beginning of 31.7 as an introductory paragraph, because it speaks to the process for all of the following subsections. 31.7(4) (b) was moved to the end of subsection (3) which addresses temporary modifications.
Commission Intent: The Commission continues to believe that temporary modifications are an important and useful water quality standards tool. The benefits of recognizing a short-term need for flexibility in the standards system is evident specifically where there are permitted dischargers on the segment.
The practical result of a temporary modification is to provide relief for permitted discharges until the time the uncertainty is resolved. The Commission continues to believe that it is more appropriate to focus resources on resolving the uncertainty rather than to focus on compliance with underlying standards that may not be appropriate.
Since temporary modifications have no impact on other aspects of Colorado's water quality management program such as the 303(d) list, the Non-point Source Program or the Total Maximum Daily Load (TMDL) Program, it is fitting that temporary modifications only be used where there are permitted discharges that would face unreasonable consequences in the absence of a temporary modification (e.g., a permit compliance schedule to meet a standard that is significantly uncertain).
Changes to the Regulation: The Commission revised the conditions for granting a temporary modification to specifically address the types of situations that warrant adoption of a temporary modification. Temporary modifications now explicitly provide time to resolve three types of uncertainty:
The third condition, significant uncertainty regarding the timing of implementing attainable source controls or treatment, will be repealed on 1/1/2013. The Commission believes that that this type of uncertainty is better addressed through the discharger-specific variance provisions which will become effective on that date.
In addition to requiring one of the three types of significant uncertainty, the Commission revised section 31.7 to establish that temporary modifications are authorized only if there is a demonstrated or predicted water quality-based effluent limit noncompliance problem. This requirement is intended to limit adoption of temporary modifications to situations where there is evidence that a discharger would face unreasonable consequences in the absence of a temporary modification.
The Commission also added section 31.7 to provide additional detail on the factual information that must be submitted in support of temporary modification proposals. The Commission notes that Division has developed an initial checklist and expects that while it may be refined over time as necessary, the Division will begin to use it to document the information that justifies temporary modifications. It will help clarify the expectations for meeting the requirement that we are adding to the regulation. While it will help assure that there is a consistent approach to documenting the need for temporary modifications, the Commission recognizes that the level of effort will vary considerably with the site-specific situation.
The Commission modified section 31.7 to clarify that the duration of a temporary modification is to be based on relevant factors including how soon resolving the issues that necessitated adoption of the temporary modification is deemed feasible. The Commission's intent is that it is important to consider site-specific information, e.g., the plan for resolving the uncertainty, in identifying an appropriate expiration date.
In this rulemaking, the Commission adopted a new subsection in section 31.7 with a delayed effective date of January 1, 2013, establishing an option for the adoption of a discharger-specific variance in certain circumstances. Subsection (4) was added to section 31.7 to describe the process and criteria for granting, extending or removing variances. Subsection (17) was added to section 31.14 to explain how discharger-specific variances are to be integrated into discharge permits.
Overview: A discharger-specific variance establishes an alternative water-quality based effluent limit value that takes the place of a standards-based effluent limit for a specific point source discharge. Since technology-based effluent limits apply independently of water quality-based requirements, discharger-specific variances do not apply to technology-based effluent limits. Technology-based effluent limits must still be met, even where a discharger-specific variance has been established.
During the term of the variance, all other water quality standards not specifically modified remain applicable. Variances ensure that the highest attainable level of water quality is achieved. At the time of the periodic basin review, the basis for the discharger-specific variance must be reviewed to determine if there has been any change in the factors upon which the variance was granted.
Variances may be granted only where there are no feasible alternatives (e.g. pollutant reduction or elimination, seasonal retention, or land application) that would allow the regulated activity to proceed without a discharge that exceeds water quality-based effluent limits (WQBELs), In addition, the Commission intends that the effluent limits included with the variance require the highest degree of protection for the use classification that is feasible to achieve.
In most instances, variances are not appropriate for new discharges. This is because a broader range of alternatives are typically feasible for a new discharge than for an existing discharge. However, the Commission believes that there are a limited number of situations where variances for new discharges should be considered.
It is the Commission's intent that discharger-specific variances are to be used after other avenues (such as temporary modifications) have been shown to be inappropriate. As specified in subsection (4)(b)(ii), temporary modifications of standards must be considered before moving forward with a request for a discharger specific variance. Temporary modifications have been an effective tool in a variety of circumstances where standards are not net. The Commission is adding the discharger-specific variance option at this time because there is a limited set of circumstances where temporary modifications are not available or may not be the most effective water quality management tool.
Delayed Effective Date: The discharger-specific variance provisions will become effective on January 1, 2013. In the intervening time, it is anticipated that the Division, with input from interested stakeholders, will develop guidance to provide additional detail regarding the implementation of the discharger-specific variance provisions adopted by the Commission. The intent of the guidance is to make the discharger-specific variance adoption and implementation process more transparent and understandable to all interested parties, while providing appropriate flexibility.
Periodic Review Requirement: A discharger-specific variance acts as a revised water quality standard for a particular discharge and will be considered by the Commission in the context of water quality standards rulemaking proceedings. The variance will be reviewed in conjunction with the water quality standards review cycle that fulfills the triennial review requirements. If, at the Issues Scoping Hearing or Issues Formulation Hearing, it is determined that action is appropriate before the next scheduled basin-wide standards rulemaking hearing, a special hearing will be held.
Expiration Dates: Discharger-specific variances are temporary and will include an expiration date. In determining the appropriate duration for a variance, the Commission's primary consideration will be the site-specific basis for the variance and the potential for achieving more protective effluent concentration or load. Additional considerations will be the timing of the discharge permit renewal and basin review cycle.
Criteria for Granting a Variance: The Commission established three independent tests for determining whether a variance is warranted. One addresses situations where achieving a specific water quality-based effluent limit is not feasible because such treatment is beyond the limits of current technology. In these cases, the technology does not exist, or if it does exist, cannot treat to the levels that are required to meet water quality standards.
The second test relates to situations where achieving water quality-based effluent limits is not feasible because the costs of required treatment would cause substantial and widespread adverse economic and social impact. Facility-specific cost, affordability, and treatment information is necessary to support a decision that a discharger-specific variance is appropriate under this test.
The third test relates to the non-economic consequences of increased treatment, including the effects on other media such as air or land. The language of this test is the same as the 40 CFR 131.10(g)(3) downgrading factor. The Commission understands this test as weighing and balancing the tradeoffs between the environmental damage caused by (in this case) exceedance of effluent limits with the environmental damage caused by meeting those effluent limits. For consideration of this factor, the Commission expects to see discussion of considerations such as the fate and transport of the pollutant if the treatment works were not present, including the effect of the point source on the timing, concentrations and location of the pollutant's delivery to the receiving water.
The second element of the "other consequences" test relates to an assessment of the wider environmental impacts of increased treatment on other media as well as on water quality. For this element, there would need to be a demonstration that the increased treatment would cause more environmental damage than the benefits of meeting the standard warrant. The entity advocating this reason for a variance would need to demonstrate the basis for such a policy decision.
In addition to meeting one of these three tests to demonstrate need for the variance, the applicant for a variance must demonstrate that the conditions for granting a temporary modification are not met. Alternatively, if that demonstration cannot be made, in order to grant the variance, the Commission must make an affirmative determination that the variance is the most appropriate water quality management tool to address the site-specific circumstances. As noted above, temporary modifications have been an effective tool for many years. The Commission's intent is that, by adding the discharger-specific variance option at this time, progress can be made on the limited set of circumstances where temporary modifications are not available or may not be the most effective tool.
Selection of the Alternative Effluent Limits: A discharger-specific variance will be selected after an evaluation of the alternative pollutant removal techniques and consideration of the impact of the variance on the uses of the stream in the area of the variance and downstream of that area. Alternative techniques should include such options as pollutant reduction or elimination (for instance in industrial manufacturing processes or the pretreatment context), seasonal retention, land application and treatment process alternatives. The chosen option must provide the highest degree of protection of the classified use that is feasible in 20 years, taking into considerations the factors in subsection (4)(a)(i)(C), where appropriate.
Permits are to include "alternative effluent limitations" which represent the limits that can be achieved at full implementation of the chosen option. The alternative effluent limits may be adjusted as new information becomes available. In some cases, for instance where current pollution removal techniques represent the limits of technology, alternative effluent limits may correspond to the level currently attained.
In most cases, acute and chronic alternative effluent limits will be specified. However, on a case-by-case basis, it may be more appropriate to establish other duration-based limits.
During the term of the variance, it is the Commission's intent that the permit require progress towards meeting the alternative limit as quickly as feasible. Steps necessary to document that progress will depend on the facts of a specific situation and the basis for the variance. In some cases, investigation of treatment technologies should continue; in others, it may require long-range planning for wastewater reuse where allowed, or process modification.
Relationship with other regulatory provisions
Antidegradation: In situations where a discharger-specific variance would authorize water quality degradation and trigger the requirement for an antidegradation review, the alternatives analysis upon which the selection of the interim limit was based can also be used for the antidegradation review. Since a demonstration that a current water quality standard is not attainable (required when a variance is considered) is a higher bar than demonstrating that protection of assimilative capacity beyond the standard is not required, it is likely that no additional analysis will be required.
Impaired Waters: As stated above, adoption of a discharger-specific variance constitutes a policy decision that, according to the terms of the variance, during the life of the variance the underlying standard does not need to be met. When a discharger-specific variance is adopted for an impaired water segment that is impaired by multiple sources, development of a TMDL would be required. The Commission intends that alternative effluent limits would establish the extent of regulatory requirements for the discharger in question, in accordance with the terms of the discharger-specific variance. Any impairments that are solely attributable to a duly authorized variance, are not to be included on the section 303(d) List. The section 303(d) List is the list of waters that still require a TMDL. In the case of impairments solely attributable to (and authorized by) a variance, a TMDL is not required since it is apparent why the water quality is impaired, and thus a TMDL is not necessary to identify the remedy for these waters. Cases where multiple sources contribute to an impairment would need to be examined on a case-by-case basis, and section 303(d) Listing may be appropriate.
Regulation #61: The Discharge Permit Regulations (at section 61.12) specify the conditions under which the Division can grant variances. In the context of permitting, the Division may grant variances to non-federal standards (i.e. ground water quality standards). The next time that Regulation #61 is revised, the Commission intends that the word "ground water" will be inserted before the word "standard" in the first line of 61.12(a).
The Commission refined one aspect of the Use Protected designation provisions of section 31.8 . The period 2000-2009 was inserted in the considerations for designating a water as Use Protected (see 31.8(2)(b)(i)(C)); i.e., a waterbody would need to have been effluent dependent or effluent dominated during the period 2000 - 2009. The purpose of this change is to avoid a situation where, over time, more and more waters become effluent dominated and therefore use-protected without the protection of antidegradation review regarding proposed new or increased water quality impacts.
The Commission declined to adopt the Division proposal to modify the definition of "Effluent Dominated". The Commission chose to retain the "eight out of ten" years required instead of changing it to "six out of ten" years.
The Commission clarified the application of dissolved oxygen criteria in lakes and reservoirs in footnote 9 of Table 1 in 31.16. The Commission determined that standards for dissolved oxygen apply as minima against which an individual profile will be assessed. Therefore, dissolved oxygen data collected from multiple locations in a single lake or reservoir on the same date will be assessed independently, and not averaged together.
Recreation: For the recreation use classification, the dissolved oxygen standard should apply to the upper portion of a lake or reservoir, which is typically where primary contact occurs. The dissolved oxygen standard within a single profile will generally be assessed as the average of all measurements from 0.5 meter to 2.0 meters, or to the bottom, whichever is less. Dissolved oxygen standards may be applied to deeper portions of a lake or reservoir on a site-specific basis if there is evidence that primary contact occurs in deeper portions of a lake or reservoir.
Agriculture: For the agriculture use classification, the dissolved oxygen standard should apply to the upper portion of a lake or reservoir, which is typically where livestock drink, and/or where water is diverted for irrigation. The dissolved oxygen standard within a single profile will generally be assessed as the average of all measurements from 0.5 meter to 2.0 meters, or to the bottom, whichever is less. Dissolved oxygen standards may be applied to deeper portions of a lake or reservoir on a site-specific basis if there is evidence that water for livestock or irrigation is drawn from deeper portions of a lake or reservoir.
Aquatic Life: For the aquatic life use classification, the numeric dissolved oxygen standards should apply to the upper portion of a lake or reservoir. The dissolved oxygen in the upper portion of a lake or reservoir will generally be characterized within a single profile as follows:
The Commission decided that dissolved oxygen may be less than the applicable standard in the lower portion of a lake or reservoir except where footnote 5(c)(iii) applies or a site-specific standard has been adopted. The Commission expects that the need for a site-specific standard will be determined at a standards hearing. Interested parties should work together to develop site-specific standard proposals that will protect species expected to occur based on sound scientific rationale and evidence.
Fall Turnover Exclusion: The Commission created additional flexibility with respect to the dissolved oxygen standard during fall turnover when oxygen-depleted bottom water may be mixed throughout a lake or reservoir. The fall turnover exclusion allows the dissolved oxygen to drop one milligram per liter below the table value standard for up to 7 days during fall turnover. However, a dissolved oxygen profile must be measured 7 days before and again 7 days after the profile with low dissolved oxygen is measured at a consistent location to ensure that the depressed oxygen condition does not persist for more than the allowed 7-day period. The Commission recognizes that fish grow more slowly when oxygen levels are slightly depressed, but also recognizes that low dissolved oxygen during fall turnover is a natural phenomenon, and that fish and other aquatic species can withstand this event without long-term negative consequences. Lakes with fish species that spawn in the fall do not qualify for the fall turnover exclusion since eggs and larvae are more sensitive to the negative effects of low dissolved oxygen. An exception to this is allowed if data show that adequate dissolved oxygen is maintained in all spawning areas for the duration of fall turnover.
Water Supply: The Commission left the existing Footnote 9 in place for the water supply use classification, but expects to consider revisions of the numeric criterion of 3.0 mg/l, and its application to lakes and reservoirs at the next basic standards rulemaking hearing in 2016.
The Commission reformatted the temperature criteria in 31.16 Table 1, and updated the values based on new data included in the Colorado Temperature Database. The Commission also deleted the razorback sucker tier (warm stream tier III), and included the razorback sucker in warm stream tier II because the expected range of the razorback sucker is also habitat for the more thermally sensitive white sucker. Since the temperature tier applied to a segment is based on the most thermally sensitive species, the razorback sucker tier was never applied. However, this action does not preclude the adoption of a site-specific temperature standard based on the expected occurrence of the razorback sucker.
Several corrections were made to the temperature criteria. Both the Arctic grayling and golden shiner were moved from stream tiers to the cold and warm lake tiers respectively because both species are found only in lakes. Additionally, a typographical error in the chronic temperature criterion for cold stream tier II, and large lakes and reservoirs was corrected.
The Commission also adopted a provision in footnote 5(c)(iv) of Table 1 to exclude certain exceedances of the temperature criteria in the shoulder-seasons from being considered an impairment of the aquatic life use. The footnote excludes exceedances of the winter temperature criteria in cold streams for 30 days before the transition from winter to summer, and 30 days after the transition from summer to winter provided that the natural seasonal progression of temperature is maintained. The Commission adopted this exclusion to account for year-to-year variation in the timing of the natural seasonal fluctuation of temperature. The Commission does not intend for this footnote to change the underlying table value during the winter shoulder season. The Commission did not apply this exclusion to lakes or warm-water streams because there was no evidence that spring and fall temperature fluctuations occur naturally outside of the regulatory "summer" season in these systems. The Commission believes that this issue should be reevaluated as more data becomes available.
The Commission also changed the air temperature exclusion in footnote 5(c)(i), so that sites must exceed the monthly maximum air temperature instead of the annual maximum air temperature. This change makes it possible to exclude data from any extraordinarily warm day for any time of year, and not just in summer when the maximum annual temperature occurs.
The Commission also clarified the definition of "maximum weekly average temperature" in 31.5 by deleting the word "daily" and adding the word "summertime".
The Commission adopted an averaging period of two months for the existing E. coli standards in Footnote 7 to Table 1. Without an averaging period, assessments have masked seasonal trends in E. coli at impairment concentrations. An averaging period of two months was selected to closely approximate the duration of the eight-week epidemiological studies, which are the basis for the table value criteria. Site-specific or seasonal standards will be assessed with intervals as close as possible to two months.
The Commission clarified how the domestic water supply standards for arsenic and nitrate would be implemented in permits by expanding on the Table II footnote 4 (nitrate) and Table III footnote 14 (arsenic). These two standards apply at the point of water supply intake. In order to provide a consistent level of protection and simplify implementation in the CDPS permitting process, the default assumption will be that the standard is applied at the end of the applicable regulatory mixing zone. This presumption can be overcome if the permittee provides information demonstrating 1) that there is no actual domestic water supply use; or 2) that the standard will not be exceeded at the point of intake
Aluminum: With regard to aluminum, information was presented at the hearing indicating that the total recoverable aluminum water quality standard of 750 µg/L acute and 87 µg/L chronic, including the relevant footnote, should be revised. The technical basis for the existing aluminum standards was the 1988 United States Environmental Protection Agency ("EPA") Aluminum Document subsequent to which additional relevant data and information has become available. The revisions to the acute and chronic aluminum standards used the EPA criteria derivation and recalculation procedures. The revisions also considered the results from more recent studies such as the Arid West Water Quality Research Project (2006), which analyzed potential updates to aluminum standards based on more complete literature reviews. The Arid West work was primarily based on an overall evaluation of the EPA recalculation procedure for Arid West effluent-dependent water users and provided information that was unavailable when the 1988 Aluminum Document was prepared. Specifically, the Arid West recalculation procedure analysis discovered an inverse aluminum toxicity and hardness relationship. A hardness-based aluminum standard is more representative of the concentration levels that harm aquatic life and so provides a better measurement of potential toxicity. The total recoverable aluminum acute criteria range from 512 µg/L to 10,071 µg/L at hardness concentrations of 25 mg/L and 220 mg/L, respectively. Following discussions with the Parties, the Commission has adopted a modified version of the original chronic criteria proposal to reflect certain species' chronic sensitivity, specifically Daphnia magna. Using the modified criteria equation, the total recoverable aluminum chronic criteria range from 73 µg/L to 1,438 µg/L at hardness concentrations of 25 mg/L to 220 mg/L. Given the available data, it was recommended that the upper bound of hardness calculations be 220 mg/L, rather than the standard 400 mg/L for other metals equations. In addition, it was noted by the Commission that some evidence indicates that rainbow trout may exhibit increased sensitivity to aluminum within the upper range of the pH standard. The Commission intends to revisit the standard if new data and information become available indicating that the current standard is not protective of rainbow trout.
Iron: The Commission declined to adopt the proposal submitted by the Colorado Mining Association. The evidence did not support the assertion that the proposed dissolved iron criterion would be protective of aquatic life.
Mercury: The Commission deleted the acute mercury table value of 1.4, and the chronic mercury table value of 0.77. These values were based on toxicological studies that included water as the sole pathway of exposure. The remaining table value for aquatic life is based on toxicological studies that included both water and food as pathways for mercury exposure. The food pathway is particularly important for mercury since it is bioaccumulative, and biomagnifies up the food chain.
Molybdenum: The Commission adopted total recoverable molybdenum table-values for the drinking water supply and agriculture use classifications. The molybdenum criterion of 210 ug/l for water supply is based on an RfD-like value that the Institute of Medicine derived from the Fungwe et. al. (1990) study and was calculated in accordance with Policy 96-2. The Commission urges the Division to review this standard and consider EPA's expected health reference level and the work underway in Europe.
The molybdenum criterion of 300 ug/l for agriculture is intended to protect livestock from the effects of molybdenosis. The agriculture table value assumes that the safe copper:molybdenum ratio is 4:1. Total copper and molybdenum intakes are calculated from the following equations:
Cu intake mg/day = [([Cu] forage, mg/kg) x (forage intake, kg/day)] + [([Cu] water, mg/l) x (water intake, L/day)] + (Cu supplementation, mg/day)
Mo intake mg/day = [([Mo] forage, mg/kg) x (forage intake, kg/day)] + [([Mo] water, mg/l) x (water intake, L/day)] + (Mo supplementation, mg/day)
The assumed values for these equations are as follows:
[Cu] forage = 7 mg/kg, [Mo] forage = 0.5 mg/kg, forage intake = 6.8 kg/day, [Cu] water = 0.008 mg/L, [Mo] water = 0.375 mg/L, water intake = 54.6 L/day, Cu supplementation = 48 mg/day, Mo supplementation = 0 mg/day.
Food and water intake is based on a 273 kg (600 lb) feeder steer consuming 6.8 kg/day of dry matter and 20% of its body weight in water per day. Site-specific water intake rates should be based on estimates of actual water consumption rates based on maximum air temperatures rather than need since cattle typically consume more water than strictly necessary. In general, assumptions about copper, molybdenum, and sulfur exposure for the purpose of deriving site-specific molybdenum standards should reflect current or potential exposure levels that are reasonable for the area, including dietary supplements. When calculating site-specific standards, copper supplementation should be as low as possible and not higher than 400 mg/day.
Uranium: The Commission revised the table value for uranium to be a hyphenated value. The Commission retained the 30 µg/L value, the maximum contaminant level (MCL) from EPA's 2000 radionuclides rule, and added a value of 16.8 µg/L. The 16.8 µg/L value is derived from use of the reference dose and relative source contribution from the 2000 radionuclides rule in Equation 1-1 of Policy 96-2. This equation and the resulting value are based purely upon the protection of human-health and do not take treatment or economic considerations into account as does the MCL. Footnote 13 to Table III will be applied to the revised uranium table value. The human-health value of 16.8 µg/L is based upon protection against the chemical toxicity effects of uranium. The Commission also added footnote 17 to reference 31.11(2) which establishes the need to maintain radioactive materials at the lowest practical level.
Zinc: Since the 2005 Regulation No. 31 Basic Standards Hearing, the zinc criteria have undergone an additional technical review and update as part of the Arid West Water Quality Research Project. These revisions involved extensive literature searches and evaluation of a considerable amount of usable data for the acute and chronic zinc toxicity databases. Using these latest updates to the acute and chronic zinc toxicity databases, the zinc criteria equations were updated.
Zinc (sculpin): The Commission added a chronic zinc equation for sculpin with modifications based upon new data and information available since adoption of the equation in 2005 (31.44). Although the equation was not captured in Table III of Regulation 31 at that time, it has been adopted and applied in some of the basin regulations, Regulations 33, 34, 35, & 37. The equation applies where mottled sculpin are expected to occur and hardness is less than 102 ppm CaCO3. It does not apply where mottled sculpin are expected to occur if the hardness is greater than 102 ppm CaCO3. Footnote 15 was added to Table III to clarify the Commission's intent for application.
The equation is based upon data and information characterizing the chronic toxicity of zinc to Colorado sculpin as zinc varies with hardness. Chronic data from sculpin outside of Colorado were not used because their toxicity exhibits a different relationship with hardness. The equation is a linear regression of chronic toxicity values and hardness.
The Commission declined to adopt the proposal submitted by the Wastewater Utility Council that the effective date of the nonylphenol standard be delayed until January 1, 2017, because the standard is not in dispute and is needed to protect aquatic life. However, the Commission recognizes the concerns about implementation of the standard expressed by several dischargers. These concerns relate to the potential difficulty of testing, measuring and controlling nonylphenol and its precursors. The Commission is retaining the effective date of January 1, 2011, based on its understanding that the normal permitting process would be followed. Effluent limits would not normally be imposed during the initial round of permit renewals, but monitoring would be required as a first step.
The Commission added clarification to a number of items and corrected minor typographical errors:
- The definition of "chronic standard" (at 31.5(7)) was revised to remove the reference to unionized ammonia.
- The definition of "existing quality" (at 31.5(20)) was revised to reference total ammonia instead of unionized ammonia and to clarify the time period used for determining existing quality for temperature.
- The subsection on ambient quality-based standards (at 31.7(1)(b)(ii)) was revised. The reference to the 85th percentile was changed to "existing quality" which is defined at 31.5(20) and includes the 85th percentile for dissolved metals, the 50th percentile for total recoverable metals and the appropriate statistics for pH, DO and temperature. The sentence regarding ambient temperature standards was deleted because it is covered in the definition of "existing quality." Acute standards for parameters in Tables I and II will be handled on a case-by-case basis.
- A solid line was added at the end of the footnotes to the Basic Standards for Organic Chemicals in subsection 31.11 to distinguish the end of the footnotes from the beginning of subsection 31.11(4)
- Punctuation was corrected in subsection 31.14 (16).
- A reference was added at subsection 31.16(3)(O).
- In Table I, the typographical error for the dissolved oxygen table value for warm water aquatic life was corrected to reflect the correct value of 5.0 mg/l. The coldwater values of 6.0 mg/l and 7.0 mg/l (spawning) had been incorrectly copied into the warm water column.
- For clarification, "1-day" was deleted from Footnote 1 to Table I.
- Language describing the transition from fecal coliforms to E. coli was deleted from Footnote 7 to Table I because this transition is complete.
- A reference to Footnote 9 was added to Footnote 1 to Table I.
- Footnote 8 to Table I was deleted because it is not used.
- The Table III column heading "Drinking Water Supply" was changed to "Domestic Water Supply" to match the name of the classification at subsection 31.1.3(1)(d).
- A missing parenthesis was replaced in the cadmium aquatic life chronic equation in Table III.
- Table IV was reformatted, the acute and chronic zinc values were updated to reflect changes adopted in this hearing, a row was added for chronic zinc numbers for the protection of mottled sculpin and the acute cadmium value at hardness 400 was corrected.
PARTIES TO THE RULEMAKING
5 CCR 1002-31.48