5 Colo. Code Regs. § 1002-36.48
The provisions of C.R.S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; 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
Pursuant to the requirements in the Basic Standards (at 31.7(3)), the commission reviewed the status of all temporary modifications to determine whether the temporary modifications should be modified, eliminated, or extended.
There are currently no temporary modifications for standards other than arsenic.
To remain consistent with the commission's decisions regarding arsenic in section 36.44 , all existing temporary modifications for arsenic of "As(ch)=hybrid" (expiration date of 12/31/24) were retained.
The division submitted a plan to resolve uncertainty in the 2019 Temporary Modifications rulemaking. The division plans to propose revised standards for arsenic as soon as possible following updated toxicological information from EPA's Integrated Risk Information System (IRIS) and completion of ongoing studies to better understand arsenic conditions in Colorado. Furthermore, per the conditions of the revised and extended temporary modification at 36.6(2)(c) (effective 6/30/2020 and expires 12/31/2024), and based on the widespread need to make progress to understand sources of arsenic and set forth processes for lowering arsenic in discharges, additional permit Terms and Conditions (T&Cs) are being implemented for facilities benefitting from the "current condition" temporary modification. These T&Cs may include requirements for additional monitoring, source identification, and characterization of source control and treatment options for reducing arsenic concentrations in effluent. The commission recognizes the need to resolve the uncertainty in the arsenic standards and ensure that human health is adequately protected.
The commission's provisions at Regulation 31.7(4) allow adoption of a discharger-specific variance (DSV), which is a temporary standard that represents the highest feasible degree of protection of a classified use, while temporarily authorizing alternative effluent limits (AELs) for a specific pollutant and specific point source discharge where compliance with the water quality-based effluent limits (WQBELs) is not feasible. An initial AEL ensures the protection of currently attained ambient water quality from the onset of the variance, and a final AEL represents the highest attainable condition that is feasible to achieve during the term of the variance.
Alamosa River/La Jara Creek/Conejos River Segment 12 (CORGAL12): The commission adopted a DSV for Alamosa River/La Jara Creek/Conejos River Segment 12 (CORGAL12) for total inorganic nitrogen (TIN) that represents the highest degree of protection of the classified use that is economically feasible for the Town of La Jara (CO0020150). The initial AEL shall not be more restrictive than 23 mg/L and the final AEL shall not be more restrictive than 14.5 mg/L prior to the expiration of the DSV on 12/31/2025. The commission ensures that the discharge will not contribute to any lowering of the currently attained ambient water quality by adopting an initial AEL that, at a minimum, represents the level currently achieved, as stated by its rule at 31.7(4)(b)(i)(C). This DSV also includes a Pollutant Minimization Program (PMP) that is described in the division's Rebuttal Revised Exhibit H (pages 23-24).There is currently significant seasonal variability in influent flows to the wastewater treatment plant that is believed to be due to groundwater inflow to the Town of La Jara's collection system. In addition, the Town of La Jara's wastewater treatment facility has sludge accumulation that is affecting its organics (TSS and BOD5) removal. During the term of this variance, the Town of La Jara will take steps to reduce groundwater inflow, which will reduce influent volume. The planned collection system lining and treatment facility rehabilitation actions will help provide the necessary conditions to achieve basic secondary standards and potentially reduce TIN concentrations in the discharge. These actions will also help establish a path forward to implementing additional TIN removal technologies in the future, if necessary.
A comprehensive alternatives analysis (division Rebuttal Revised Exhibit H Appendix H-4) demonstrated that there are currently no economically feasible alternatives that would allow the Town of La Jara to meet its TIN WQBELs and compliance with these WQBELs would cause substantial and widespread adverse social and economic impacts to the community. The Town of La Jara is identified as a disadvantaged community by the Department of Local Affairs (DOLA). Due to the limited number of ratepayers, the community's low median household income, high unemployment rate, and declining population, it is not feasible for the Town of La Jara to make the capital investment that would be required to meet the TIN WQBELs at this time. Based on the information in the division's Rebuttal Revised Exhibit H Appendix H-1, the commission determined that any alternative that would result in user fees exceeding 1.7% of median household income for the Town of La Jara's residents was economically infeasible at this time.
The commission adopted a DSV with an initial AEL to protect the ambient water quality in the receiving stream and a final AEL that is based upon the expected TIN effluent quality that will be achieved through feasible improvements to the lagoon. Because there is uncertainty in the final effluent quality that will be achieved, the Town of La Jara will collect additional data to characterize the effectiveness of the improvements, which the commission will review upon reevaluation of the DSV. The commission expects that the Town of La Jara will submit annual reports to the division describing the progress made on PMP implementation in November of each year until the end of the DSV. If, at the end of the DSV, it remains infeasible for the Town of La Jara to achieve TIN WQBELs, a subsequent DSV may be appropriate.
In addition, the acronym "AEL" was defined at 36.6(2)(a).
5 CCR 1002-36.48