5 Colo. Code Regs. § 1002-36.16
The provisions of 25-8-202(1)(a), (b), and (2); 25-8-203; 25-8-204; and 25-8-402 C.R.S. provide the specific statutory authority for adoption of these regulatory amendments.
The Division proposes the following revisions to the segmentation, classification, and standard for segments 8, 9, and 11 of the Closed Basin (Kerber Creek and its tributaries). The Division proposes to revise the segment descriptions for segment 8, to divide segment 9 into segments 9a and 9b, and to amend the description for segment 11. Water quality standards based on dissolved criteria are proposed for segment 8. Water supply and agricultural use classifications and corresponding standards are added as goals for segment 9a. Cold water aquatic life class 1, water supply, and agriculture are proposed to be added as goals for segment 9b together with the corresponding standards. Temporary modifications based on the existing quality of segments 9a and 9b are proposed through June 30, 1997. Fecal coliform standards based on the 200/100ml criterion are proposed for segments 8, 9a, and 9b. The specific changes to the segment descriptions, use classifications, and water quality standards are shown in Table 1.
BASIS AND PURPOSE
The mainstem and tributaries to Kerber Creek in the Closed Basin portion of the Rio Grande Basin, including all or portions of segments 3, 8, 9, and 11 were withdrawn from consideration at the hearing for amendments to the water quality classifications and standards for the Rio Grande Basin, 3.6.0 (5 CCR 1002-8) held on November 1, 1993 in Alamosa Colorado. The Water Quality Control Division (Division) and ASARCO Incorporated (ASARCO) jointly stipulated to setting aside these segments for a later site-specific hearing because of efforts already underway by the Hazardous Materials and Waste Management Division (HMWMD) and ASARCO to collect additional samples which would better describe the water quality of Kerber Creek and several of its tributaries.
The description of segment 8, which formerly included the headwaters of Kerber Creek and Squirrel Creek, was modified to include all of the small streams, most of which are on National Forest land, that are unimpacted by the mining that has occurred in the Kerber Creek watershed. Water quality samples collected from several of these streams between 1990 and 1993 indicate that the quality is better than TVS for the existing classified uses.
The Division proposes to split segment 9, which includes the impacted mainstems of Kerber Creek, Squirrel Creek, Copper Gulch and Rawley Gulch, into two segments. Proposed segment 9a includes the portions of Squirrel Creek, Rawley Gulch, and Kerber Creek and their tributaries that have been impacted by mining. Major sources of metals and acid are from Squirrel Creek which includes mill tailings and adit drainage from the Rawley #12 mine, and from Rawley Gulch. Water supply and agricultural classifications and corresponding numeric standards were added as goals. Temporary modifications, which are based on the existing quality for cadmium, copper, lead, iron, manganese, and zinc, have been adopted for the period that remediation activities are expected to occur. Segment 9a currently does not have an aquatic life use classification, and as a result of a use attainability analysis performed by the Division, one is not proposed. Human-caused conditions and sources of pollution likely prevent the attainment of an aquatic life use within a twenty year period.
The numeric standards adopted reflect the water supply classification and are intended to protect shallow wells drilled in the alluvium along Kerber Creek which may be used as a domestic source by residents of the community of Bonanza. Water from Kerber Creek is also used to water livestock. A site-specific standard for manganese (water supply) was adopted because it is unlikely than a 50 ug/l standard can be achieved; moreover, the manganese criterion is based on aesthetics and not human health. The Commission adopted a copper standard of 1,000 ug/l to protect drinking water, since no specific scientific support could be identified for the 500 ug/l standard proposed for livestock watering.
Proposed segment 9b begins at Brewery Creek, which is the largest tributary unimpacted by metals, and extends to the confluence with San Luis Creek. The upper end of segment 9b is seriously impacted by 9a and from several large piles of tailings deposited along Kerber Creek downstream of Brewery Creek. Cold water aquatic life 1, water supply and agricultural classifications were added as goals with corresponding numerical standards. Temporary modifications, based on the existing quality for cadmium, copper, lead, iron, manganese, and zinc, were adopted for the period that remediation activities are expected to occur. Numeric standards adopted will avoid chronic toxicity to brook trout.
The water hardness of segment 9b increases in a downstream direction and metal concentrations decrease. Dilution from Brewery Creek further reduces the metal concentrations. The Colorado Nonpoint Source program found that some aquatic life is already present in the lower reach of the segment, mainly between Little Kerber Creek and San Luis Creek. This 10 mile reach of Kerber Creek will significantly benefit from remediation activities undertaken in segment 9a and the upper portion of 9b. Because of the increasing hardness and precipitation of metals the lower end of the segment should support brown trout. Monitoring of San Luis Creek by the Division in 1992 found both brook and brown trout below the confluence of Kerber Creek. Water from this segment of Kerber Creek is used for watering livestock and irrigation.
It is recognized that segment 9b of Kerber Creek, which is more particularly described as the mainstem of Kerber Creek, from the confluence with Brewery Creek to the confluence with San Luis Creek, could not currently meet a cold water aquatic life class 1 classification. In addition to water quality, currently physical characteristics, such as stream bank erosion, sparse vegetation, and broad shallow morphology in some areas, may inhibit aquatic habitat. These have been caused by past and present land use practices. Therefore, this classification is placed on this segment as a goal qualifier. It is recognized that ASARCO will direct all remediation that effects segment 9b of Kerber Creek to the attainability of a classification of cold water aquatic life class 1. However, full aquatic life class 1 use on segment 9b may require additional efforts to improve the physical conditions of the stream by persons who are not parties to this rulemaking and on property over which ASARCO has no control. This classification is intended to encourage such efforts.
Waters in new segment 11 were contained in segment 2 prior to the November 1, 1993 rulemaking hearing and included all tributaries in the Closed Basin which are in the Rio Grande National Forest. Several streams in new segments 8 and 9a were in the former segment 2. New segment 11 is mostly comprised of streams from the east side of the Closed Basin that drain the Sangre de Cristo Range. Many are within the newly designated Sangre de Cristo Wilderness Area. No changes to the classifications are proposed, and TVS based on dissolved metals are already in place.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-36.16