5 Colo. Code Regs. § 1002-38.55
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
Segment 5 of Big Dry Creek includes a series of ponds that lie below the Rocky Flats Environmental Technology Site (RFETS) sewage treatment plant outfall (discharge point STP1). These ponds are part of what is known as the B-Series ponds. More specifically, these ponds are designated as ponds B3, B4 and B5, in upstream to downstream order. This segment is currently classified and has numeric standards for radionuclides, including americium and plutonium.
During the decommissioning of the site, certain cleanup activities may increase the risk of an accidental release of radioactive materials into the sewage treatment plant (STP) collection system, and then into the environment. There may also be releases from soils as a result of surface runoff, which have in the past resulted in some short term excursions above stream standards in the Walnut Creek drainage. In either case, the specific parameters of concern are americium and plutonium.
While the risk of a release from the STP may be very small, if a release did occur, the ponds would reduce the potential for an off-site release to downstream segments. The current draft NPDES permit for the sewage allows RFETS to use an outfall that currently exists above the ponds - referred to as STP1. But, there are no numeric effluent limitations for americium or plutonium assigned to outfall STP1, due to legal disputes about the applicability of such limits.
The permit includes a second outfall below the ponds - known as STP2, which in effect is limited for americium and plutonium through a separate CERCLA based control mechanism - the Rocky Flats Cleanup Agreement (RFCA). While this outfall is not yet constructed, it is envisioned that eventually it will be the primary outfall for the STP.
Even after STP2 is operational, the permit will allow the discharge from STP1 under special circumstances. In order to allow this type of discharge, and because of the existing periodic excursions of stream standards - that are due to man-made conditions that will eventually be remediated, temporary modifications to the underlying numeric americium and plutonium standards are being adopted.
Although the current radionuclide standards have generally been attained in segment 5 in the past, the temporary modifications are being adopted due to the unique challenges associated with decommissioning a nuclear weapons facility. The temporary modifications are narrative standards, allowing the Walnut Creek portion of segment 5 americium and plutonium levels to be higher than the current underlying standards - up to a maximum level of whatever is necessary to maintain the numerical standards in the downstream segment. This downstream segment has compliance points and instream limits on americium and plutonium as part of the Rocky Flats Cleanup Agreement which require that the levels of these parameters be maintained within the stream standards.
The temporary modifications must be in place before the 401 Certification can be issued for the NPDES permit. The ultimate term of these temporary modifications is envisioned to be during the entire period of decommissioning, with an expiration date of December 31, 2009. The NPDES permit and several RFCA associated documents that are currently being revised directly affect the level of protection afforded to segment 5 and downstream segments. In order to ensure that adequate protections are included in these documents within a reasonable period of time, the temporary modifications will initially be adopted with an expiration date of December 31, 2000. During, the May, 2000, triennial review of the South Platte River Basin standards, the temporary modifications may be extended to December 31, 2009, to coincide with site closure, if there is sufficient reason to believe that downstream water quality standards will still be protected.
Because the STP does not discharge into the Woman Creek drainage, the temporary modifications adopted in the rulemaking only apply to the Walnut Creek drainage. The temporary modifications do not apply to the Woman Creek portion of the Big Dry Creek, segment 5, namely Pond C-2.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-38.55