5 Colo. Code Regs. § 1002-38.89
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, 2016, 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. Unless otherwise noted, these temporary modifications will expire 12/31/2015. The basin-wide review hearing is scheduled for June 2015 and it is anticipated that any remaining issues will be resolved in that hearing process.
Upper South Platte River segment 10a, copper
Upper South Platte River segment 14, copper, temperature
Upper South Platte River segment 15, ammonia, copper, temperature
Upper South Platte River segment 16g, copper, temperature
Upper South Platte River segment 16i, copper
Bear Creek Basin segment 1c, chlorophyll, total phosporus
Clear Creek Basin segment 2a, zinc, copper (expiration date of 7/01/2015)
Clear Creek Basin segment 2c, copper (expiration date of 7/01/2015)
Clear Creek Basin segment 9a, copper (expiration date of 7/01/2015)
Clear Creek Basin segment 11, copper (expiration date of 7/01/2015)
Clear Creek Basin segment 14a, copper, temperature
Clear Creek Basin segment 14b, copper, temperature
Clear Creek Basin segment 15, copper, temperature
Boulder Creek Basin segment 8, selenium (expiration date of 7/01/2015)
Boulder Creek Basin segment 9, Copper (expiration date of 7/01/2015)
St.Vrain Creek Basin segment 2b, copper
St.Vrain Creek Basin segment 6, selenium
Middle South Platte Basin segment 1a, selenium, ammonia
Middle South Platte Basin segment 4, Barr Lake and Milton Reservoirs, pH
Big Thompson River Basin segment 2, DO, E.coli, ammonia, nitrate, boron, cadmium, copper lead, mercury, nickel, selenium, silver, and zinc
Big Thompson River Basin segment 4b, selenium
Big Thompson River Basin segment 5, selenium
Big Thompson Basin River segment 9, selenium
Cache La Poudre River segment 11, selenium
Cache La Poudre River segment 12, selenium
Cache La Poudre River segment 13b, seleinum
Lower South Platte River Basin segment 1, selenium
Extension of Temporary Modification: Site-specific copper standards for Upper South Platte segment 10a based on the Biotic Ligand Model were proposed by Plum Creek Water Reclamation Authority (PCWRA). During the course of the hearing process and discussion with the Division, EPA and other parties, PCWRA modified its proposal. The Commission adopted PCWRA's modified proposal to extend the temporary modification to 12/31/2018 and change the statement of the temporary modification to "current condition". The Commission expects that PCWRA will participate in discussions in 2015 with the WQCD and other stakeholders about the FMB application of the BLM.
The Commission extended until July 1, 2020, the temporary modifications for Clear Creek Segment 2a zinc and for Segment 2c copper. The Commission found that: these segments are not currently meeting the respective standards; the Georgetown Wastewater Treatment Facility anticipates problems meeting the zinc standard; the Central Clear Creek Sanitation District Wastewater Treatment Facility anticipates problems meeting the copper standard, and; there are additional ongoing and future remedial activities for metals that could significantly contribute to achieving either or both of these standards. The extent of remedial activities by EPA and CDPHE under CERCLA and by other stakeholders is a key consideration in resolving the uncertainty as to appropriate water quality standards. The extension until July 1, 2020 is intended to allow review of these temporary modifications after the next (2019) CERCLA Five-Year Review is completed.
New Temporary Modification: The Commission adopted a new temporary modification of the ammonia standard in a portion of Upper South Platte segment 3, below the Florisant Water and Sanitation District wastewater treatment facility. Evidence was presented that the discharger has a compliance problem and there is significant uncertainty regarding whether there are feasible treatment options. This temporary modification will expire on December 31, 2017 and will be reviewed in the December 2015 annual review.
New Site-Specific Standards: The Commission adopted site-specific copper standards based on an investigation of the copper bioavailability of Segment 2 below the Upper Thompson Sanitation District's wastewater treatment plant outfall location that employed the Biotic Ligand Model (BLM) and the Fixed Monitoring Benchmark (FMB) methodologies. The original proposal introduced by UTSD was withdrawn and replaced with a compromise proposal offered by the Division. The compromise addressed some of the Division's technical concerns while UTSD avoided the added cost of preparing for another hearing and greatly reduced uncertainty about facility planning.
Based on a review of actual water chemistry and comparison of BLM results at several stations, the Commission elected to base its decision on analysis of data from Station M50, which is immediately downstream of the WWTP discharge. Stations further downstream showed less sensitivity to copper (higher FMB values), so basing the standard on Station M50 protects the downstream uses.
The data record at Station M50 included 115 sampling events from 2004 through 2014. Copper data did not meet the distributional assumption (lognormal) implicit in the BLM, but some additional processing ("trimming") yielded defensible values.
The BLM/FMB analysis resulted in acute and chronic water quality criteria for copper of 11µg/L and 7.5 µg/L, respectively, for the portion of segment 2 below the wastewater treatment plant. The Commission anticipates that these standards will be reviewed as a part of the basin hearing in June 2015, and the values may be modified based on additional technical guidance for analysis and interpretation of data supporting use of the BLM.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-38.89