5 Colo. Code Regs. § 1002-35.15
The provisions of 25-8-202(1) (b) and (2); 25-8-204; and 25-8-207 C.R.S. provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted, in compliance with 24-4-103(4), and 24-4-103(8)(d), C.R.S. the following statement of basis and purpose and fiscal impact.
Basis and Purpose:
No change in the aquatic use classifications was requested, although aquatic uses are extremely limited in the new segment 9a. A water supply classification was included for the existing segment 5 within which the headwaters were previously included, and the ambient quality should be sufficient to support that use. No water supply uses exist or are anticipated in super Imogene and Sneffels Creeks and the existing quality is poorer than the dissolved manganese criterion for a water supply classification. Therefore, new segments 9a and 9b do not include a water supply use classification.
The changes in water quality standards are based upon a one-year sampling program conducted by Engineering Science, Inc., in consultation with the Division. The changes more accurately reflect existing stream quality, since the Commission's 1983 adoption of classifications and standards for these segments was based upon extremely limited data.
In determining appropriate standards based on the new data, the Commission applied the Division's established methodology for the rejection of certain data "outliers". The Commission felt that the inclusion of these outliers in the standards calculation would have resulted in standards that are not representative of water quality normally found in the segments in question. The adopted standards more accurately reflect existing ambient quality.
The temporary modification for mercury for segment 9b, adopted for one year, is based on the level necessary to protect aquatic life. The underlying standard for mercury is based on the level necessary to protect human health, assuming bioaccumulation of mercury in fish tissue. If a bioaccumulation study is completed on this segment by the Camp Bird Venture prior to the expiration of the temporary modification, the Commission will reconsider the appropriateness of the underlying standard.
The basis for the adoption of the temporary modification for lead in segment 9a is that imposition of the underlying standard at this time would likely result in substantial and widespread economic and social impact within the area in question, without corresponding environmental benefit. Evidence submitted indicates that construction of a treatment plant to meet the underlying standards could cost on the order of one to two million dollars. A cost of this magnitude would put continuation of the current exploration activities at the Camp Bird Mine - which currently employees 97 people - at risk.
The Commission also decided tinat no permanent downgrading of tine segments in question is necessary at tinis time. Witlnin tine time frame of tine temporary modification, tine Camp Bird exploration operations would be completed and the long-term economic impact of meeting the underlying standards should be known. If new information n economic impacts or ambient water quality becomes available prior to that time, those segments can be readdressed at the request of Camp Bird Venture. In any event, at the next triennial review, the pending revision to the Basic Standards and Methodologies, although it is not anticipated that new facts will be available by that time to warrant reconsideration of the temporary modifications.
Fiscal Impact:
Other than the rulemaking hearing, no increased regulatory costs will result from the changes. No change in existing mine discharge flows is contemplated, and existing treatment of the historic mining flows will continue during the life of the temporary modification for lead. Adoption of the temporary modification will avoid the potential for an adverse substantial and widespread economic and social impact that could result from requiring immediate compliance with the underlying standards.
The revised standards, based on more accurate data, generally are less stringent than the previous standards for these waters. This should help assure that discharge treatment requirements are not unnecessarily string, resulting in potential long-term cost savings for existing or future dischargers.
5 CCR 1002-35.15