5 Colo. Code Regs. § 1002-42.19
The provisions of section 25-8-202(1)(a), (b) and (2); 25-8-203; and 25-8-204; C.R.S., provide the specific statutory authority for adoption. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
In this rulemaking proceeding, the Commission has adopted changes to site-specific ground water use classifications and standards to be more consistent with current and anticipated future uses, taking into account the Rocky Flats site cleanup and water management strategy. This approach allows for the deletion of domestic and agricultural use classifications for ground water in the site-specific area of the Rocky Flats Site because those uses will be prevented by institutional control. The Surface Water Protection Classification was retained and the Statewide Standards for Surface Water apply. Radionuclide standards were amended to be consistent with new Statewide standards.
DOE has been studying the sources of ground water contamination associated with past weapons production and other industrial activity, as well as contaminant migration patterns in ground water at the Rocky Flats Environmental Technology Site (RFETS) since the 1980s. These studies and interim remedial measures have been implemented in accordance with the requirements of the Federal Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and the Federal Resource Conservation and Recovery Act (RCRA) and its companion State law and regulations under a succession of agreements among the U.S. Department of Energy, U.S. Environmental Protection Agency and the State of Colorado.
In 1991, the Commission adopted Site-specific use classifications and quality standards for ground water within the boundaries of what is now called the Rocky Flats Environmental Technology Site (Site). Per 5 CCR 1002-8, 3.12.7(1), the "Specified Area" includes unconfined ground waters in the unconsolidated Quaternary, Rocky Flats, Arapahoe and Laramie-Fox Hills aquifers within the Site boundary. Use classifications for ground water in the Quaternary and Rocky Flats aquifers were set, including Domestic Use-Quality, Agricultural Use-Quality and Surface Water Protection. The Basic Standards for Ground Water in 5 CCR 1002-8, 3.11.5, Tables 1 through 4, were applied to all ground waters in the Specified Area, while additional Site-specific standards for organics and radionuclides were established for the Quaternary and Rocky Flats aquifers in Tables 5 and 6 of 3.12.7(1).
The Upper Hydro-Stratigraphic Unit (UHSU) is a term developed at this Site and other RCRA/CERCLA sites to define ground waters in different lithologic units that are in hydraulic connection with each other and/or with surface water. The UHSU at the Site consists of unconsolidated surficial deposits, weathered bedrock and sandstones in hydraulic connection with overlying units. Use of the term UHSU in this regulation, in lieu of the Quaternary and Rocky Flats aquifers, to define the upper-most portion of the "Specified Area" will allow the Commission to protect water quality in ground water which does not meet the useable quantity expectations associated with the term aquifer.
The Site conceptual model for contamination sources and migration patterns shows that all known, delineated ground water contamination plumes associated with Site sources have transport pathways through alluvial and weathered bedrock ground waters which discharge only to surface waters within the Site boundaries. This hydrologic regime, along with DOE's agreement-articulated in the recently finalized Rocky Flats Cleanup Agreement (RFCA) and Vision-to restrict uses of ground water at the Site for any purpose other than to support cleanup, justifies the removal of the Domestic and Agricultural Use Classifications of Site ground waters. In addition, removal of the domestic and agricultural uses, while retaining the Surface Water Protection Use Classification, is consistent RFCA and the Vision wherein the signatories have agreed that DOE will remediate ground water to prevent migration of contaminants into surface waters at levels that impair their classified uses.
Adoption of the proposed statewide health risk-based standards for plutonium and americium allows deletion of these standards from the site specific standards, Table 6. The Woman Creek drainage standards for gross beta and uranium are amended to be consistent with adoption of proposed changes to the Site Specific Surface Water Standards.
The Commission has revised 5 CCR 1002-8, 3.12.7(1)(b) by deleting the Domestic and Agricultural Use Classifications and Standards on the Rocky Flats Specified Area; deleting Table 5; and amending Table 6.
PARTIES TO THE RULEMAKING
5 CCR 1002-42.19