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 to determine whether the temporary modification should be modified, eliminated or extended.
A.Ammonia: Temporary modifications of ammonia standards on nine segments were reviewed. Deleted: Ammonia temporary modifications were deleted on the following segments because permits had recently been reissued for dischargers on the segments. In these cases, compliance schedules in the permits are adequate to address any necessary treatment plant upgrade issues
Middle Arkansas segment 9
Lower Arkansas segment 1a
No action: The Commission took no action on the ammonia temporary modifications on the following segments.
Middle Arkansas segment 3
Fountain Creek segments 2a, 4, and 6
Lower Arkansas segments 1b, and 7
Except for Fountain Creek segments 2a and 4 (which expire 12/31/2012) these temporary modifications will be allowed to expire on 12/31/2011.
B.Other Parameters: The type iii temporary modifications of the copper standards for Fountain Creek segments 2a and 6 were also reviewed and no action was taken. EPA's guidance on the Biotic Ligand Model (for possible development of site-specific copper standards) has not yet been released. These will be reviewed again in the December 2011 Temporary Modification hearing.C.Middle Arkansas segment 4c: Paint Brush Hills Metropolitan District provided to the Commission the preliminary results of the Use Attainability Analysis on portions of Middle Arkansas segment 4c, which supports possible resegmentation to separate some or all of Black Squirrel Creek and its tributaries from segment 4c. Evaluation of an appropriate ammonia standard is also in development for the segment. To allow Paint Brush Hills Metropolitan District time to complete the UAA and propose resegmentation and site-specific standards for the new segment, the Commission has decided the expiration date of the ammonia acute and chronic standards temporary modification on Middle Arkansas segment 4c that is currently scheduled to expire on 12/31/2011 is extended to 12/31/2013. The Commission emphasized that its intent and expectation is that the issues that necessitated adoption of this temporary modification should be resolved as soon as possible and in a manner that takes full advantage of the opportunities provided by the annual December reviews of temporary modifications. The Commission recognizes that it is important to resolve uncertainty regarding the underlying standards so that temporary modifications can be eliminated and any needed pollution controls can be put in place in a timely manner.
PARTIES TO THE RULEMAKING HEARING
1. Paint Brush Hills Metropolitan District2. Tri-State Generation and Transmission Association4. Mountain Water and Sanitation District5. City of Grand Junction6. Colorado Division of Wildlife8. U. S. Environmental Protection Agency9. City of Colorado Springs and Colorado Springs Utilities38 CR 03, February 10, 2015, effective 6/30/201539 CR 03, February 10, 2016, effective 3/1/201639 CR 03, February 10, 2016, effective 6/30/201639 CR 23, December 25, 2016, effective 12/30/201640 CR 03, February 10, 2017, effective 6/30/201741 CR 01, January 10, 2018, effective 1/31/201841 CR 03, February 10, 2018, effective 6/30/201841 CR 17, September 10, 2018, effective 12/31/201842 CR 04, February 25, 2019, effective 6/30/201943 CR 03, February 10, 2020, effective 6/30/202044 CR 01, January 10, 2021, effective 2/14/202144 CR 05, March 10, 2021, effective 6/30/202144 CR 17, September 10, 2021, effective 12/31/202145 CR 17, September 10, 2022, effective 9/30/202246 CR 10, May 25, 2023, effective 6/14/2023