5 Colo. Code Regs. § 1002-38.43
The provisions of 25-8-202(1) (b) and (2); 25-8-204; and 25-8-402 CHRIS provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted in compliance with 24-4-103(4), CHRIS, the following statement of basis and purpose.
BASIS AND PURPOSE:
Section 3.8.5 has been revised to delete an outdated reference to a former provision of this regulation and to simplify the language of this subsection.
The 50 ug/l dissolved manganese standard formerly listed for segment b of Boulder Creek has been deleted to correct an apparent clerical error. No water supply classification has ever been applied to this segment, so this standard is inappropriate.
Segment 5 of Big Dry Creek
The Commission postponed the statewide radionuclide standards hearing from the previously scheduled date, based on delays in EPA's promulgation of drinking water radionuclide standards. Therefore, it is appropriate to extend the expiration of the temporary modifications for radionuclide standards included in the segment 5 standards from December 31, 1994 to December 31, 1996, and the Commission has done so.
Segments 7a and b
The Commission has revised the segmentation of two tributaries to the South Plate River. The previous segments of 7a, all tributaries to the South Plate River below the confluence with the North Fork to the outlet of Chatfield Reservoir, and b, mainstem of Brush Creek and Filter Gulch from the source to the confluence with the South Plate, have been combined into a single segment, 7.
The substantive effect of this consolidation is to withdraw the water supply classification from the previous segment b, making it identical to the previous segment 7a and, thus, obviating the need for separate segments. In 1988, the Commission adopted a water supply classification for segment b. The water supply classification was established in order to protect water quality in the South Plate alluvium. In 1991, the Commission adopted an interim narrative standard for the Lower South Plate River Alluvium and Terrace Gravel System. See ' 3.12.5 (5 CCR 1002-8). The classification system adopted by the Commission in 1991 assures that the water quality of the South Plate Alluvium will be maintained. This eliminates the need for the water supply classification for Brush Creek and Filter Gulch.
The previous water supply classification was also based, in part, on the possibility of a hydrologic connection between Brush Creek and Filter Gulch to the ground water in the area of the Kassler Water Treatment Plant. However, evidence presented at the hearing demonstrated that the include of Brush Creek and Filter gulch on water quality in the South Plate alluvium is negligible and that the South Plate River is the major contributor to the alluvium in the area around the Kassler Water Treatment Plant.
When the Commission adopted the water supply classification for segment b in 1988, there was evidence of a possible future use for water supplied in the Denver water distribution system from the Kassler Plant should the Plant ever be reopened. However, the Kassler Plant has not been used as a water source since its termination in 1985, and there is no indication that the Kassler Plant will be reopened in the reasonably foreseeable future.
Clear Creek, Segments 14 and 15
Clear Creek segment 14 is currently classified for aquatic life warm 2, recreation 2, water supply and agriculture uses. Clear Creek segment 15 is classified for aquatic life warm 1 goal qualifier, recreation 2, water supply and agriculture uses. Temporary modifications are in existence for Segment 14 below the Croke Canal for cadmium, zinc, and copper. The temporary modifications are due to expire on June 30, 1994.
Coors operates two wastewater treatment plants at its facility in Golden, Colorado, discharging to Clear Creek segment 14 below the Croke Canal. The general wastewater treatment plant processes wastewater primarily from the City of Golden, but also from various industrial facilities which comprise the non-brewing operations at Coors. A process wastewater treatment plant processes only the waste from the brewing operations at Coors. The effluents from the two treatment plants are combined for discharge below the Croke Canal pursuant to Permit No. CO-0001163. During many months of the year the statistical flow in Clear Creek is very low or zero due to diversions for municipal and agricultural uses above the discharge. Consequently, the water quality standards are, in effect, the permit limits for the Coors discharge. If stream standards were to be set based upon table values and converted into discharge limitations, then the limits for copper and zinc could not be met with the current wastewater treatment technology. There is no economically feasible and technically reliable end of the pipe technology which would meet such low limits.
Brewing operations universally produce a waste which is high in biochemical oxygen demand. In the case of Coors, this results in highly alkaline wastewater. Alkalinity has an attenuating effect on the toxicity of certain metals to aquatic species. For this reason, Coors' effluent is capable of carrying metal levels that are above the current water quality standards without harm to the most sensitive aquatic organisms. Biomonitoring studies carried out by Coors consistently show that survival of Ceriodaphnia dubia and fathead minnows is very high even in 100 percent effluent. On the other hand, Clear Creek above the discharge point is often lethal to Ceriodaphnia dubia because of the high concentration of metals in Clear Creek and its low hardness and alkalinity. As a result of these observations, Coors conducted a study to be the basis for setting site-specific criteria-based standards proposed in this rulemaking.
Site-Specific Criteria Based Standards
The Commission's basic standards regulations provide for the establishment of site-specific water standards when justified by the results of a bioassay or comparable scientific study. It provides a mechanism for taking the wide variation of conditions that exist in Colorado into account when adopting site-specific standards. Adopting such site-specific standards simply means that different numerical standards are adequate to protect the uses in question. Colorado Water Quality Control Division guidelines for developing site-specific aquatic life criteria are comparable to EPA's water effect ratio method for setting aquatic life criteria. The Division guidance regards development of site-specific water quality criteria as appropriate when". . . existing standards, often based on laboratory defined criteria, are under protective or over protective of the aquatic life classification." The State guidance also refers to the need to protect the worse case conditions of in-stream toxicity. The water effect ratio procedure uses samples taken at low and high flow to address this concern. The procedure also uses the lowest, that is, the most conservative value, of the three that are generated. The Division guidance uses the most sensitive species to act as a surrogate for the protection of the ecosystem. The water effect ratio procedure uses Ceriodaphnia dubia as the most sensitive species and includes a secondary species to verify the results. The procedures establish the concentrations for metals that are acceptable for protecting the aquatic uses.
Coors conducted a water effect ratio study using biomonitoring tests to establish the level at which a metal is toxic in a given effluent and receiving water, specifically Clear Creek. In conducting the study, Coors worked closely with personnel from the Water Quality Control Division and EPA.
The study involved taking samples downstream of the discharge point, upstream of the discharge, and the effluent itself. Biomonitoring tests were run with samples at different dilutions with reconstituted laboratory water. The metals of interest are added in different concentrations in order to produce toxicity during the test. The data is used to establish the LC50 in accordance with the standard biomonitoring test procedures. Parallel tests are also performed with the same type of test organisms in reconstituted laboratory water with enough metal being added to produce an LC50 for the samples. The concentration of the metal that produced the LC50 in the downstream sample is then divided by the amount of metal that produced an LC50 in the reconstituted laboratory water. This ratio is called the water effect ratio. The ratio is designed to take into account the beneficial effect of the receiving stream and effluent that allow aquatic organisms to live at metals levels that are lethal in reconstituted laboratory water. Since reconstituted laboratory water is used in setting water quality standards by EPA, the water effect ratio is multiplied by the water quality standards to generate a new stream standard that is site-specific.
Coors chose Prospect Park in segment 15 as the downstream site, as it is sufficiently downstream of the effluent discharge so that mixing with the receiving stream is complete, but it is sufficiently close to the discharge point so that no other discharge would have been included in the sample. Two flow seasons were used and samples were taken at least three weeks apart as required by the water effect ratio guidance. Samples for upstream were taken at Vanover Park in golden above the Coors discharge point. Ceriodaphnia dubia and fathead minnows were used following accepted State and EPA protocol. As required, samples were spiked with specified metals in separate tests using copper, zinc and silver. The metal concentration for the Prospect Park sample was first adjusted to account for the amount of metals initially present in the sample before spiking. These final water effect ratio results were multiplied by the appropriate water quality standard to arrive at the site-specific criteria-based water quality standards. The analyses performed by Coors following the above procedure resulted in site-specific water quality standards that are now being proposed for zinc and copper.
South Mosquito Creek, Segments 2b and 2c
In 1987, the Commission adopted a three-year temporary modification for zinc in segment 2b and for zinc and mercury in segment 2c of South Mosquito Creek. The zinc temporary modifications were calculated from the sampling data collected below the London Mine Venture discharge. The underlying chronic zinc standards are 110 ug/1 and 250 ug/1, respectively. The temporary modifications for zinc are scheduled to expire on June 30, 1994. The current London Mine discharge permit referenced above is based upon the temporary modifications for zinc. Both the stream ambient data and the discharge data exceed the underlying standard. The underlying zinc standards are not being met due to human-induced conditions upstream from the London Mine, that is, historic mining activity has ceased. There is no current or anticipated mining activity occurring at the London Mine. Consequently, in the future the permit may deactivate. In the past, actions have been taken to improve the quality of the discharge by diverting flows with high levels of metals inside the mine. If necessary, additional future actions will be evaluated. The available stream data are limited, particularly dissolved data, but will continue to be collected during the period of an extended temporary modification. The current limited data support the extension of the temporary modifications and additional data will continue to be collected from the stream and the mine discharge. The proposed temporary modifications are based upon sampling data. Further, natural surface drainage over surface zinc exposures into No Name Creek may cause South Mosquito Creek to contain more zinc than the standard would, at times, allow.
PARTIES TO THE RULEMAKING HEARING APRIL, 1994
5 CCR 1002-38.43