2022-08-25_PERMIT FILE - M2022001

• Permit No: M2022001
• IBM Index Class Name: Permit File
• Doc Date: 8/25/2022
• Doc Name: Adequacy Review Response #2
• From: Civil Resources, LLC
• To: DRMS
• Email Name: JLE
• Email Name: PSH
• Media Type: D
• Archive: No

TABLE OF CONTENTS
Paqe
1.0 INTRODUCTION.............................................................................................................................................1
2.0 AREA GEOLOGY............................................................................................................................................1
3.0 SITE GEOLOGY..............................................................................................................................................1
4.0 EXISTING GROUNDWATER CONDITIONS...................................................................................................2
5.0 GROUNDWATER MODEL..............................................................................................................................3
5.1 Regional Topography........................................................................................................................3
5.2 Bedrock Surface................................................................................................................................3
5.3 Hydraulic Conductivity.......................................................................................................................4
5.4 Specific Yield.....................................................................................................................................4
5.5 Boundary Conditions.........................................................................................................................4
5.6 Internal Influences.............................................................................................................................5
6.0 MODEL SIMULATIONS...................................................................................................................................6
6.1 Existing Conditions............................................................................................................................6
6.2 Slurry Wall Installation.......................................................................................................................7
6.3 Mitigation Alternatives.......................................................................................................................9
6.3.1 Cell 5S Slurry Wall Mitigation Scenarios................................................................................10
6.3.2 Drain Recharge......................................................................................................................11
7.0 CONCLUSIONS............................................................................................................................................12
8.0 BIBLIOGRAPHY............................................................................................................................................12
Tables
Table1 Boundary Conditions.......................................................................................................................................5
Table 2 Measured and Modeled Site Groundwater Levels...........................................................................................7
Table 3 Mining Groundwater Level Table(Slurry Walls In-Place)................................................................................8
Table 4 Base Model and Modeled Site Groundwater Level After Cell 3,4, and 5N Slurry Walls.................................9
Table 5 Base Model and Modeled Site Groundwater Level After Cell 3,4, 5N and 6 Slurry Walls............................10
Table 6 Water Diversion Necessary With or Without Cell 5S Slurry Wall...................................................................10
Table 7 Groundwater Surface Elevations with Drain Install Options...........................................................................11
Groundwater Model Report—Section 20 Gravel Mine Site -ii- August 2022