2021-09-27_REVISION - M1990057 - Laserfiche WebLink

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Mr. Dustin Czapla 8 CDRMS September 24,2021 Lake County, CO has a low earthquake risk, with one (1) earthquake since 1931. The USGS database shows that there is a 3.53% chance of a major earthquake within 50km of Lake County, CO within the next 50 years. The largest earthquake within 30 miles of Lake County, CO was a 3.1 Magnitude in 1993 (near Twin Lakes). There is less than 0.08% chance that an earthquake of 7.0 would occur over the next 50 years. The unconsolidated soil and glacial till beneath the tailings are not expected to respond unusually to seismic activity. No other geologic hazards at the site have been identified that would preclude the operation of the approved tailings storage facility. Soil Soils within the permit and adjacent area is discussed in Section 9.0 Rule 6.4.9: Exhibit I - Soils Information Appendix 9-1. The following also presents Mr. John Nelson's (District Conservation ist-USDA-SCA-1990) reclamation mill site specific observations and recommendations. "The mill site area is located approximately 2 miles southwest of Leadville, Colorado at an elevation of 9750 feet. This site also falls within the Lake County soil survey of which only one soil series has been mapped, the Leadville sandy loam (LeE)". Mr. Nelson's report follows: This site will be used to dispose of mill tailings with a basic pH. All topsoil encountered in this area should be stockpiled for future reclamation work. The above-mentioned seeding recommendations and rates may also be used in the mill site area, especially in areas where topsoil is placed over mill tailings. In addition, the owners have requested that several "seeding test plots"be established at this site to help determine which plant materials will be best suited for reclamation work in higher pH soils. Plant materials and future monitoring of these test plots will be provided by the Lake County Soil Conservation District and the Soil Conservation Service. In addition to the above recommendations, future seedings may been enhanced by the use of fertilizers, mulches and manure. The amount of fertilizer should be determined by use of soil tests. However, nitrogen can be applied at a rate of at least 50 pounds per acre, and phosphate at a rate of 40 pounds per acre. If straw mulches are used, they should be crimped into the soil with a disc, cleats on heavy equipment or with hand tools. Manure should be available locally and would do much to improve the soil condition. Taking care of the seeding during the first year or two of growth may also help in establishing a successful stand of grass. Keeping wildlife and possibly livestock off the seeding during at least the first growing season will help new seedings establish themselves. This may be accomplished with fencing. In addition, if water is available, watering during the first growing season would do more than anything else to help the stand establish itself." CJK has provided maps, narrative and effectiveness of the Environmental Protection Plan in (Section 7.0 Rule 6.4.7 Exhibit G Water Information, Section 21.7.4 - Monitoring Systems, Section 21.9 -Groundwater Quality Data, Section 21.12-Mill Water Quality Monitoring Plan, Appendix 21-3 thru Appendix 21-9 and Standard Operating Procedures (SOPs). See Figure 3-6 Surface and groundwater monitoring, Figure 4-1-Flowsheet and Material Balance, Figure 4-8 Leak Detection and Figure 6-1 TSF-Post Mill Reclamation Plan Map in permit. (d) Describe, with maps and narrative, the monitoring systems, monitoring site locations, sample designator, parameters sampled, frequency of sampling, report