Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-33 - REGULATION NO. 33 - CLASSIFICATIONS AND NUMERIC STANDARDS FOR UPPER COLORADO RIVER BASIN AND NORTH PLATTE RIVER (PLANNING REGION 12)
Section 5 CCR 1002-33.39 - STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; DECEMBER 12, 2005 RULEMAKING EFFECTIVE MARCH 2, 2006

A. History

Segments 5 and 7 are within the sphere of influence of a historic zinc-mining district, including the former Eagle Mine site. From 1980 until 1999, ambient quality-based standards for several metals had been in place on segments 5 and 7. In 1988, remediation of the Eagle Mine site began under Superfund. In the August 1999 rulemaking the Commission adopted new underlying standards (goals) and Temporary Modifications for cadmium and zinc to reflect existing water quality. The standards (goals) were based on ARARs established in the 1993 Eagle Mine Superfund Site Record of Decision (ROD). The ARARs are defined in the ROD as numerical remedial action goals subject to revision, and were based on table values in the Basic Standards. The Commission noted in the 1999 Statement of Basis and Purpose that, upon completion of remedial action or achievement of an agreed-upon acceptable level of recovery of aquatic biota in segments 5 and 7, the water quality data for the segments should be reviewed to ascertain the current levels of in-stream metals. Based on such findings, site-specific standards may be deemed appropriate for segments 5 and 7 for any metals still exceeding the underlying standards/goals.

B. Temporary Modifications

The Superfund remedial action requirements were completed in 2001, and have resulted in significant improvement in water quality in segments 5 and 7. Therefore, revision of the Temporary Modifications to reflect these water quality improvements is appropriate.

Because water quality data in these segments indicate very strong seasonal trends, seasonal Temporary Modifications have been established for these segments. The 85th percentile of the data for each season was used as the "chronic" value; the 95th percentile was used as the "acute". The Temporary Modifications are set to expire January 1, 2009, coincident with the effective date of standards set at the June 2008 rulemaking hearing for the next triennial review for this basin. Pending the outcome of additional activities at the Superfund Site, changes to the underlying standards will be proposed during the triennial review process. The revised Temporary Modifications adopted in this rulemaking are based on the water quality measured at an integrator station located near the downstream end of each segment; therefore, mass balance calculations conducted for permitting of discharges within the segments and attainment determinations shall be based on attainment of the standards at the downstream end of the segment.

Remaining Uncertainty: Uncertainty still exists as to the appropriate underlying standards to apply to these segments. There is uncertainty regarding what aquatic life use is attainable, based in part on uncertainty regarding the potential for additional remediation and other activity in this watershed. There is also uncertainty regarding what water quality levels are necessary to protect a selected expected aquatic life use. It appears that zinc is the primary environmental variable that negatively influences aquati life. Prior to expiration of these Temporary Modifications, additional studies will be undertaken to address this uncertainty

Duration of the Temporary Modification: The Commission has set the Temporary Modification to expire on January 1, 2009. This coincides with the anticipated effective date of changes that will be made in the next basin-wide hearing (June, 2008) The Commission expects that the above mentioned studies as well as the CERCLA process will reduce the uncertainty and provide a basis to move forward with underlying standards in the June 2008 hearing process.

C. Re-segmentation.

The Commission adopted re-segmentation of segments 5 and 7, based on recognized changes in water quality, hardness and use. Segments 5 and 7 have been subdivided into five sub-segments as described below:

5a Mainstem of the Eagle River from a point immediately above the compressor house bridge at Belden to a point immediately above the Highway 24 Bridge near Tigiwon Road.

5b Mainstem of the Eagle River from a point immediately above the Highway 24 Bridge near Tigiwon Road to a point immediately above the confluence with Martin Creek.

5c Mainstem of the Eagle River from a point immediately above Martin Creek to a point immediately above the confluence with Gore Creek.

7a Mainstem of Cross Creek from the source to a point immediately below the Minturn Middle School, except for those waters included in Segment 1.

7b Mainstem of Cross Creek from a point immediately below the Minturn Middle School to the confluence with the Eagle River, except for those waters included in Segment 1.

D. Antidegradation

Because remediation activities have improved water quality in segments 5a, 5b, 5c and 7b, since the September 30, 2000 date established in the Basic Standards as the default baseline, the Commission has included a note in the Designation column in the tables to indicate that the September 30, 2000 default baseline date does not apply to these specific segments. In accordance with the Basic Standards (section 31.8), the appropriate baseline date and baseline water quality will be determined at the time that a new activity triggers an antidegradation review. It is anticipated that this will be the date upon which the antidegradation review commences. The City of Colorado Springs raised concerns that the antidegradation review process includes calculations of low-flow pollutant concentrations, and that the ultimate development of upstream water rights will decrease instream flows that currently provide dilution flow to these stream segments. The Commission clarifies that nothing in this Regulation is intended to or shall be construed as requiring the maintenance of instream flows for any purpose.

PARTIES TO THE RULEMAKING