5 Colo. Code Regs. § 1002-32.58
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, 2018, to determine whether the temporary modification should be modified, eliminated or extended.
No action: The commission took no action on the temporary modifications on the following segments.
Upper Arkansas Segment 8b: temporary modifications of temperature standards. Resurrection mining presented evidence that they are making progress on the plan for eliminating the need for the temporary modification. The commission made no change to the expiration date of 12/31/2017 as the original time allotment was deemed adequate to resolve the uncertainty.
Middle Arkansas Segment 4b: temporary modifications of ammonia, arsenic, chronic boron, cadmium, chlorine, chronic chlorophyll a, chromium III, chromium VI, copper, acute cyanide, dissolved oxygen, E. Coli, chronic iron, lead, manganese, chronic mercury, chronic molybdenum, nickel, chronic nitrate, chronic nitrite, acute pH, chronic phosphorous, selenium, silver, chronic sulfide, and zinc. The commission made no change to the expiration date of 12/31/2018 as the original time allotment was deemed adequate to resolve the uncertainty.
Lower Arkansas Segment: 1a: temporary modifications of the selenium and sulfate standard. The City of Pueblo is making progress on its plans to seek a discharger-specific variance (DSV). The two major tasks for the division and Pueblo are to develop the Alternative Effluent Limit and to fully articulate the compliance schedule. The commission made no change to the expiration date of 12/31/2018 as this time allotment was deemed adequate to resolve the uncertainty.
Extensions:
Upper Arkansas Segment 8b: temporary modifications of the chronic cadmium, and acute and chronic zinc standards were extended to 12/31/2018. The commission extended the expiration date to 12/31/2018 for the temporary modifications for segment 8b for chronic cadmium, and acute and chronic zinc to allow time to collect additional biological data in ponded wetland habitat to resolve the uncertainty regarding the resident biota and appropriate standards for this segment. This may be suitable habitat for sensitive organisms important to the recalculation procedure. In the event that access is not granted to sample this habitat on Iowa Gulch, sampling the ponded habitat from nearby streams may be necessary to inform the resident species list in Iowa Gulch.
Middle Arkansas Segment 6b: temporary modification of the temperature standard was extended to 12/31/2018. Public Service Company of Colorado presented evidence that additional time is needed to collect data to resolve the uncertainty regarding the underlying temperature standard. Therefore, the commission extended the expiration date of the "current conditions" temporary modification for temperature to 12/31/2018.
New temporary Modifications:
Middle Arkansas Segment 2: temporary modification of the temperature standard. The commission adopted a "current conditions" temporary modification of temperature. Colorado Parks and Wildlife operates the Pueblo hatchery that currently has temperature compliance issues. There is uncertainty about the appropriate temperature standard in the Arkansas River below Pueblo Reservoir. Temperature records in the Arkansas River below Pueblo Reservoir indicate the cold stream tier II temperature standards have never been attained since record keeping began in 1986, and Pueblo Reservoir already has an ambient-based temperature standard. CPW will collect additional information on the Arkansas River including instream temperatures throughout the segment, effluent temperatures, and coldwater species reproduction to support a site-specific standard. The commission adopted this temporary modification with an expiration date of July 1, 2021. The commission will first review progress on this study plan in the June 2018 Arkansas Basin hearing.
Site specific standards: The commission adopted site-specific standards for the following segments.
Upper Arkansas Segment 8b and 9: site-specific standard for acute cadmium. The commission adopted a site-specific standard for Segments 8b and 9 using a hardness-based equation for acute cadmium based on the EPA recalculation procedure. The recalculation method provides a revised equation for acute cadmium which is intended to protect the resident, attainable aquatic macroinvertebrate communities and fish populations in Iowa Gulch, and is consistent with the site-specific standard on the downstream receiving waters, Upper Arkansas Segment 2c.
Resegmentation: The commission approved the following resegmentation.
Upper Arkansas Segments 8a and 8b: the boundary between Segments 8a and 8b was clarified by changing the description of the upper boundary of Segment 8b to include additional description and coordinates for the historical ASARCO water supply intake. This redefinition was necessary because the ASARCO water supply intake no longer exists. This segment boundary is based on a difference in water use and water-quality characteristics in these two segments.
New Temporary Modifications of the Arsenic Standard:
Consistent with the actions taken in 2013, the commission adopted a temporary modification of the arsenic standard on segments on the following list, with an expiration date of 12/31/2021. At the April 8, 2013 rulemaking, the commission heard testimony that concurred with the finding from a December 13, 2011 rulemaking hearing that an initial reasonable lower limit of treatment technology for arsenic is 3.0 µg/L, pending further investigation by the division, dischargers and stakeholders. The temporary modification was established by the commission to allow for a temporarily less stringent application of the chronic arsenic standard in control requirements for both existing discharges and new or increased discharges.
Upper Arkansas Segment 2a
Upper Arkansas Segment 2c
Upper Arkansas Segment 7
Upper Arkansas Segment 14b
Upper Arkansas Segment 18
Upper Arkansas Segment 37
Middle Arkansas Segment 7a
Middle Arkansas Segment 7b
Middle Arkansas Segment 18a
Middle Arkansas Segment 20
Fountain Creek Segment 1b
Fountain Creek Segment 8
Lower Arkansas Segment 9a
Lower Arkansas Segment 11
Lower Arkansas Segment 19
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-32.58