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GENERAL48098
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Last modified
8/24/2016 8:23:57 PM
Creation date
11/23/2007 4:05:54 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1987072
IBM Index Class Name
General Documents
Doc Date
8/6/2004
Doc Name
Proposed Decision & Findings of Compliance for SL2
From
Phase III /Final
Permit Index Doc Type
Findings
Media Type
D
Archive
No
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Completion of Evaluation Required by Section 3.03.2(21 <br />The Division has conducted an evaluation of the reclamation work, in accordance with <br />Section 3.03.2(2). This evaluation considered, among other things: the results ofinspections <br />and monitoring, the need for further reclamation work, whether pollution of surface or <br />subsurface water is occurring, and the probability of future occurrence of such pollution. The <br />evaluation concluded that all reclamation has been completed in the bond release area, no <br />water pollution is occurring, and there is little potential for future water pollution. Impacts to <br />ground water and surface water aze described below. <br />Grouud Water Impacts: <br />As shown in Figure 1, the underground workings of the La Plata Mine aze <br />above the current ground water saturated zone. The elevation of the top of <br />the saturated zone is considered to be stabilized at its approximate current <br />position. Only a significant long-term change in regional climate or <br />significant nearby well pumping would significantly raise or lower this <br />elevation. <br />Over time, meteoric water probably infiltrates from the land surface down <br />into the abandoned underground workings of the La Plata Mine. As this <br />water slowly accumulates in the workings, it would seep into the bedrock <br />walls of the workings, and migrate downgradient to the saturated zone. The <br />expected migration direction would be generally southwazd from the <br />workings. Any minerals this migrating water picks up in the mine workings <br />would be carried to the saturated zone. If the mineral content of this <br />migrating water is high, then it could pollute the ground water in the saturated <br />zone. The infiltration and migration process would take many decades owing <br />to the slow infiltration rate and the low hydraulic conductivity of the Cliff <br />House Sandstone and Menefee Formation. It is improbable that any water <br />from the La Plata workings has reached the saturated zone, yet. <br />Also, it is improbable that the La Plata workings have dischazged water to the <br />land surface in the portal azea because it would take many decades to fill the <br />workings enough to exert significant pressure in the portal area. No seepage <br />or dischazge from the portal area has been found during the Division's regular <br />inspections. The improbability of current degradation to the saturated zone, <br />and the absence of dischazges from the portal, indicate the La Plata Mine is <br />not causing ground water pollution, and the operation is in compliance with <br />the Basic Standazds for Ground Water (Colorado Water Quality Control <br />Regulation 41.S.C.6). <br />An acidic seep existed within the permit azea when the permit was issued in <br />1987 (page 15 of permit application). The seep discharged from a cut slope <br />along the access road at the east end of the mine portal bench. The seep <br />
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