-'-;^ Á^:\^rv'ÍV\ ' ~ " - '■ -" * WÊÊSSÊÊ•JV-V:= Modifications, Corrections and Revisions to the Animas UAA Several replacement pages to the UAA are included in this mailing. The plastic binder can be easily be opened by hand if you don't have a binder contraption. Remove original page(s) and replace with new. The following is a summary of the changes we have implemented. Chapter 8 The Ac/Ch Standards.xls workbook (previously Ac_Ch TVS.xls), Appendix 8-B, was modified to reflect the WQCD’s most current equations. Figures 8.16 and 8.17, which compare dissolved and total metal concentrations using the WORM, were revised to correct an error in copying formulas for iron, D/T_Fe.xlsf and zinc D/T_Zn.xls, The DissJTot Folder is a part of the Appendix 8-C. Formula errors in for cadmium, D/T_Cdxls, and manganese, D/T_Mn.xls, were also corrected; however these two metals were are not depicted in figures 8.14 through 17. Chapter 11 M18C, described as the 1st SW Drain-MF Min, was deleted from Table 11.1, Metal loads from selected adits in the Upper Animas Basin. This site is the “red tributary.” It was incorrectly classified as a mine adit. Phase 1 reduction scenarios for aluminum and iron shown in Figures 11.1a and 11. Id were modified to reflect removing M18C as an adit source. Deleting this source also affected concentrations shown in Figures 11.2a and lL2d. Table 11.3, Summary o f metal loads from adits and combined mine waste for the Animas River Basin above A 72, was modified to account for removing 1 SW Drain- MF Min as an adit source of metals. The text of pages XI-2, XI-6, & XI - 7 have revised to reflect that Table 11 1 now contains only 33 (rather than 34) of a total of 133 (rather than 134) draining adits which accounts for 89% of adit loads (rather than 91%). A waste load reduction scenario that considers the impact of zinc loading to the Animas River from undetermined sources between A53 and A68 was developed. The load analysis is based on stream flow and water chemistry at A53 and A68 between August 1998 and August 1999. Results of the load analysis are contained in the workbook A53 A68 Loadxls. The zinc load from undifferentiated sources approximates zinc loads from all adit sources in the basin. The result of removing this undifferentiated zinc load, represented as Zn concentrations at A68 and A72, is presented in the workbook entitled A53_A68 Redxls. • Table 12.1 a-f has been slightly modified to reflect newly adopted Table Value Standard equations and corrections to the anticipated reductions from draining adits. • The title to Table 12.2 has been changed from 85% pH to 15% pH to reflect correct percentile used for pH standards • Table 12.4 has been modified to reflect coiTected values for stream standard and temporary modification recommendations resulting from changes in Table 12.1. Additional Analyses Recently Being Developed includes: • Cumulative Remediations Reductions and Costs from Adits • Cumulative Remediation Reductions and Costs from Mine Wastes • Metal Loading Analysis for Animas river between Howardsville and Silverton These will be made available at regularly scheduled ARSG meetings or upon request. Figure 8.16 Comparison of total recoverable and dissolved iron concentrations and the cyclical variation of pH at stream gages in the upper Animas Basin. Animas at Silverton, A68, is not shown because most observations of dissolved iron are less than detection. Animas River at Silverton, A68 Cement Creek CC48 Month Month ToM R e c o v ----------- Dis ♦ pH { Totd R e c o v ------------Oissotod ♦ pH Mineral Creek, M34 Animas River below Silverton, A72 Month Month Total R e c o v --------- aâsd v etl ♦ pH { TeW R e c o v ------------D ssd w d ♦ pH Figure 8.17 Comparison of total recoverable and dissolved zinc concentrations and the cyclical variation of pH at stream gages in the upper Animas Basin. V I I - 4 7 Legend Figure 8.20a Seasonal, flow-based sources of total recoverable aluminum and iron to Mineral Creek near Silverton, estimated from the water quality regression model. Stream flow is the average monthly flow at M 34,1993 to 1999. Calculated values are for the 15th day of each month. Figure 8.20b Seasonal, flow-based sources of total recoverable cadmium, copper, manganese, and zinc to Mineral Creek near Silverton, estimated from the water quality regression model. Stream'flow is the average monthly flow at M 34,1993 to 1999. Calculated values are for the 15th day of each month. CHAPTER XII - RECOMMENDATIONS The recommendations of this report are based on a combination of four components of the UAA - the biological assessment, the water chemistry assessment, the limiting factors analysis, and the remediation analysis. Most of the recommendations are directed to the Colorado Water Quality Control Commission (WQCC), but a few are aimed at other stakeholders: the San Juan Board of County Commissioners, U.S. Forest Service, and the U.S. Bureau of Land Management. The recommendations for WQCC lie in three areas, segmentation, use classifications and water quality standards. CHANGES IN SEGMENTATION While the UAA has focused on stream segments in the Upper Animas Basin that have impaired water quality, many small tributaries to Mineral Creek and the Animas River can meet cold water aquatic life class 1 Table Value Standards (TVS). Some of these small streams have improper or non-existent use classifications and standards. For example, about nine small tributaries to the Animas River from Maggie Gulch to Elk Park (tributaries to Segments 3 a, 3b, and 4a), have been inadvertently omitted from descriptions of any segment and therefore have no applicable use classifications and standards. Several tributaries to the upper part of Mineral Creek have no aquatic life classifications, yet they are located in non-mineralized areas and have very good water quality. To bring the omitted segments under regulatory compliance and to more accurately portray the current water quality situation, it is proposed that all tributaries to the Animas River from Maggie Gulch to Elk Park be placed under one segment description, segment 6, with exceptions made for those areas that do not meet TVS for aquatic life class 1. The exceptions fall under: segment 7, the drainage of Cement Creek, segment 8, Mineral Creek above South Mineral Creek including tributaries on the east side of the creek except for Big Horn Creek, and the Middle Fork of Mineral Creek, segment 9, Mineral Creek from South Mineral Creek to the Animas River, currently called segment 9b. Segment 6, therefore includes tributaries to Mineral Creek on the west side of the drainage, which is outside the caldera, except for the Middle Fork of Mineral Creek. It includes’the South Fork of Mineral Creek and Big Horn Creek which is only tributary included on the east side of Mineral Creek. The differences in water quality between streams in segment 6 and those in segments 7, 8, and 9 are closely tied to differences in geology of the areas those streams drain. technology that could be used and the size and complexity of site. Accessibility affects both cost and the remediation technique selected. As discussed in Chapter X, the cost analysis is a first approximation and uses four cost categories, each with a broad numerical range. The costs for remediation for each site listed in Table 11.1 below is the mid-point of the range for each cost category. One million dollars was used as an estimate for sites whose costs are greater than $500,000. These cost estimates do not include engineering design, operation, or maintenance costs that may be needed. Loading from the Largest Adit and Mine Waste Sources The adits have been ranked, using the weighting factors discussed in Chapter 10, on the basis of both high and low flow loading of seven metals plus pH. Most high flow samples were obtained in June or July, while low flow loads were obtained in September or October. These figures may overestimate low-flow loading since early fall stream flows had not yet dropped to levels seen in winter months. Loads from the Kohler, Bandora, North Star, and Evelyn mines were sampled frequently. Selection of sites to be included for possible remediation is based upon the combined rankings of all sites within the Upper Basin (Appendix 10E). Many sites were previously categorized as "no action" because of their low total contributions and remoteness and/or low concentrations. The loading from the top ranking 33 adits, including a few large loaders lacking either a high or a low flow sampling datum, are displayed in Table 11.1. These are current loading figures and do not include any potential reductions. Eighty nine percent of the loading from all adits comes from these top 33 sites. Mine waste piles have been ranked in a similar fashion as adits including the same weighting factors, except that they are ranked by metal concentration determined by the leach test instead of load (Appendix 11 A). Table 11.2 lists the top 26 mine waste sites plus an additional six sites which were added because of their large size and therefore potential for significant load contributions. Leachate concentrations presented in Appendix 10E have been converted to "potential loads". The annual load contributed from waste rock site in Table 11.2 was estimated by multiplying the concentration from the leach test of the waste rock times the surface area of the pile times the average annual runoff from the basin expressed as depth (29 inches).