5 Colo. Code Regs. § 1002-38.98
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 temporary modifications scheduled to expire before December 31, 2020 to determine whether the temporary modifications should be modified, eliminated, or extended.
For the temporary modifications set to expire after the effective date of this hearing, the commission reviewed progress toward resolving the uncertainty in the underlying standard and/or the extent to which conditions are a result of natural or anthropogenic conditions, and evaluated whether the temporary modifications were still necessary. The commission took no action on the following temporary modifications:
Upper South Platte Segment 10a (COSPUS10a): temporary modification of the temperature standards (expires 12/31/2020). Plum Creek Water Reclamation Authority continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Upper South Platte Segment 14 (COSPUS14): temporary modifications of the chloride and temperature standards (expire 12/31/2020). Centennial Water and Sanitation District continues to make progress to resolve the uncertainty in the chloride standard. Centennial and South Platte Water Renewal Partners (formerly Littleton/Englewood) continue to make progress to resolve the uncertainty in the temperature standard. The commission made no change to the expiration dates, as the original time allotment was deemed adequate to resolve the uncertainty.
Upper South Platte Segment 15 (COSPUS15): temporary modifications of the chloride, sulfate, and temperature standards (expire 12/31/2020). Public Service Company of Colorado continues to make progress to resolve the uncertainty in the chloride and sulfate standards. Metro Wastewater Reclamation District continues to make progress to resolve the uncertainty in the temperature standard. The commission made no change to the expiration dates, as the original time allotment was deemed adequate to resolve the uncertainty.
Upper South Platte Segment 16g (COSPUS16g): temporary modification of the temperature standards (expires 12/31/2020). Centennial continues to make progress to resolve the uncertainty in the temperature standard. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Bear Creek Segment 1c (COSPBE01c): temporary modifications of the chlorophyll a and phosphorus standards (12/31/2020). The division is currently working on a model intended to resolve uncertainty in the standards and inform TMDL development. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Clear Creek Segment 2a (COSPCL02a): temporary modification of the acute and chronic zinc standards (expires 7/1/2020). Georgetown continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Clear Creek Segment 2c (COSPCL02c): temporary modifications of the chronic copper and chronic cadmium standards (expire 7/1/2020). Central Clear Creek Sanitation District continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Clear Creek Segment 13b (COSPCL13b): temporary modification of the temperature standards (expires 12/31/2020). City of Black Hawk / Black Hawk Central City Sanitation District continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Boulder Creek Segment 9 (COSPBO09): temporary modification of the acute and chronic temperature standards (expires 12/31/2020). The City of Boulder continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
St. Vrain segments 6 and 7 (COSPSV06 and COSPSV07, respectively): temporary modifications of the chronic iron and acute and chronic manganese standards (expire 12/31/2020). Raytheon Boulder continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Big Thompson Segment 9 (COSPBT09): temporary modification of the chronic selenium standard (expires 12/31/2020). The Town of Milliken continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Cache la Poudre Segment 11 (COSPCP11): temporary modification of the acute and chronic temperature standards (expires 12/31/2020). The City of Fort Collins continues to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
Cache la Poudre Segment 12 (COSPCP12): temporary modification of the acute and chronic temperature standards (expires 12/31/2020). The City of Fort Collins and the City of Greeley continue to make progress to resolve the uncertainty. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
The commission deleted the temporary modifications on the following segments:
Cherry Creek Segment 1 (COSPCH01): temporary modification of the chronic copper standard (expires 12/31/2020). The commission deleted this temporary modification because progress was not being made on the plan to resolve uncertainty and alternative regulatory tools are available to dischargers with copper compliance concerns.
Cherry Creek Segment 3 (COSPCH03): temporary modification of the chronic arsenic standard (expires 12/31/2021). The commission deleted this temporary modification because it was adopted in error. The temporary modification is more stringent than the underlying standard.
Boulder Creek Segment 7b (COSPBO07b): temporary modification of the chronic arsenic standard (expires 12/31/2021). The commission deleted this temporary modification because it was adopted in error. The temporary modification is more stringent than the underlying standard.
Boulder Creek Segment 8 (COSPBO08): temporary modification of the chronic selenium standard (expires 12/31/2020). The commission deleted this temporary modification because progress was not being made on the plan to resolve uncertainty and alternative regulatory tools are available to dischargers with selenium compliance concerns.
Big Thompson Segment 4b (COSPBT04b): temporary modification of the chronic selenium standard (expires 12/31/2020). The commission deleted this temporary modification because progress was not being made on the plan to resolve uncertainty and alternative regulatory tools are available to dischargers with selenium compliance concerns.
Cache la Poudre Segment 13b (COSPCP13b): temporary modification of the chronic selenium standard (expires 12/31/2020). The commission deleted this temporary modification because progress was not being made on the plan to resolve uncertainty and alternative regulatory tools are available to dischargers with selenium compliance concerns.
The commission took no action on temporary modifications that were set to expire on or before the effective date of this hearing. The commission deleted the following temporary modifications, which were allowed to expire:
Upper South Platte Segment 10a (COSPUS10a) - copper and manganese
Clear Creek segments 11, 14a, 14b and 15 (COSPCL11, COSPCL14a, COSPCL14b, and
COSPCL15, respectively) - temperature
Clear Creek Segment 13b (COSPCL13b) - cadmium
Regarding the cadmium temporary modification on Clear Creek Segment 13b (COSPCL13b):
The commission determined that the Black Hawk/Central City Sanitation District does not currently have a demonstrated or predicted water quality-based effluent limit compliance problem, and that it was appropriate to allow the temporary modification to expire on 12/31/2018.
Significant uncertainty remains in this segment regarding the water quality standards necessary to protect current and/or future uses and whether existing quality is the result of natural or irreversible human-induced conditions. Specifically, it is uncertain whether instream concentrations will attain the underlying cadmium standards following implementation of CERCLA remedies at the CDPHE/EPA Mine Water Treatment Plant. Furthermore, uncertainty exists as to what the highest attainable use will be and when data and other relevant information will be available to characterize that use.
5 CCR 1002-38.98