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M <br /> COLORADO LEGACY LAND <br /> December 19,2022 RECEIVED <br /> Mr.Michael Cunningham <br /> Division of Reclamation,Mining,and Safety DEC 3 0 2022 <br /> Department of Natural Resources <br /> 1313 Sherman Street,Room 215 DIVISION OF RECLAMATION <br /> Denver,CO 80203 MINING AND SAFETY <br /> Subject: Technical Revision#30 <br /> Mine Land Reclamation Permit M-1977-300, <br /> Former Schwartzwalder Mine,Golden,Colorado <br /> Dear Mr.Cunningham: <br /> Colorado Legacy Land, LLC (CLL) is currently executing a soil excavation project in support of the ongoing <br /> environmental remediation and reclamation work at the Former Schwartzwalder Mine site in Golden,Colorado <br /> (the Site). In order to complete the excavation work, CLL is requesting a technical revision to Mine Land <br /> Reclamation Permit M-1977-300 for the following items: <br /> Update Quarterly Monitoring Network: <br /> Since taking ownership of the site in 2018, CLL has conducted quarterly surface water and groundwater <br /> monitoring of the site in accordance with the MLR Permit specifications. After compiling and reviewing data <br /> from these sample locations,CLL is requesting the following updates to the quarterly monitoring network: <br /> Groundwater Monitoring Locations: Three alluvial monitoring wells and one sump in the current <br /> quarterly monitoring network are within the boundaries of the excavation areas. Although excavation <br /> was not initially anticipated to extend to bedrock near these wells and sump (Figure 1),onsite gamma <br /> scanning indicates the presence of deeper contamination down to bedrock in this area (Figure 1). <br /> Figure 1 illustrates the excavation extents that were initial scoped in Technical Revision #14 and the <br /> currently anticipated excavation extents, which overlaps with MW-6, MW-7, MW-12, and the Master <br /> Sump. Table 1 summarizes the location, construction information, lithology, and justification for <br /> removal of the sump and these wells. Detailed soil boring logs and monitoring well construction <br /> reports for each well and sump are included in Attachment A. <br /> Shallow alluvial monitoring wells MW-6, MW-7, MW-12, and the Master Sump (Sump 1) are <br /> recommended for removal to ensure that the surrounding contaminated alluvial soils are <br /> appropriately excavated and disposed. In addition, because excavation around these wells is <br /> anticipated to extend to bedrock, therefore these alluvial wells and sump will not have a function <br /> without the surrounding alluvium. The current and proposed updated groundwater monitoring <br /> network are shown on Figure 3 and Figure 4, respectively. CLL notes that an additional bedrock well <br /> in the area of MW-7 and MW-12 is planned for after completion of the alluvial excavation project in <br /> summer 2023;this well will appropriately sample bedrock water quality that remains in this area,and <br /> the surface water locations retained on site (Figure 5) will sample surface water in this area. Removal <br /> of the wells and sump shall be documented with a Well Abandonment Report, Form GWS-09 <br /> (Attachment B) and filed with the State of Colorado, Office of the State Engineer within 60 days of <br /> removal. <br /> Groundwater wells shown on Figure 4 and the Mine Pool spigot sample (located inside the water <br /> treatment plant)shall be sampled in the second quarter,third quarter,and fourth quarter of each year. <br /> During the first quarter of the year wells are not sampled because access is made difficult in many <br /> locations by snow,and the plant is not operational. This is consistent with CLLs commitment to worker <br /> health and safety as well as CLLs seasonal site management strategy. <br /> PAGE 1 OF 23 <br />