2024-03-21_REVISION - M2022009

• Permit No: M2022009
• IBM Index Class Name: Revision
• Doc Date: 3/21/2024
• Doc Name: Request for Technical Revision
• From: Civil Resources LLC
• To: DRMS
• Type & Sequence: TR1
• Email Name: RDZ
• Email Name: EL1
• Media Type: D
• Archive: No

TABLE OF CONTENTS
Page
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 4
5.2 Bedrock Surface 4
5.3 Hydraulic Conductivity 4
5.4 Specific Yield 5
5.5 Boundary Conditions 5
5.6 Internal Influences 6
6.0 MODEL SIMULATIONS 7
6.1 Existing Conditions 7
6.2 Slurry Wall Installation 8
6.2.1 Red Tierra Equities, LLC Section 20 Site Impacts 9
6.3 Mitigation 10
6.3.1 Cell 1 Slurry Wall Construction 11
6.3.2 Cell 2 Slurry Wall Construction 11
6.3.3 Cell 3 and 4 Slurry Wall Construction 12
6.3.3.1 Cell 3 and Cell 4 Mitigation 13
6.3.4 Combined Mitigation with Section 20 14
6.3.4.1 Monarch Cell 1 Slurry Wall with Section 20 14
6.3.4.2 Monarch Cell 3 Slurry Wall with Section 20 15
6.3.4.3 Monarch DENM and Section 20 Full Build Out 15
7.0 CONCLUSIONS 17
8.0 REFERENCES 17
Tables
Table 1 Boundary Conditions 6
Table 2 Measured and Modeled Site Groundwater Levels 8
Table 3 Surrounding Property Groundwater Elevations 9
Table 4 Surrounding Property Groundwater Elevations—Both Sites 10
Table 5 Base Model and Modeled Site Groundwater Level After Cell 1 Slurry Wall 11
Table 6 Base Model and Modeled Site Groundwater Level After Cell 1, and 2 Slurry Walls 12
Table 7 Base Model and Modeled Site Groundwater Level After Cell 1, 2, 3, and 4 Slurry Walls 13
Table 8 Cell 3 and 4 Slurry Wall with Underdrain Mitigation 14
Table 9 Monarch DENM and Section 20 Approximate Construction Timeline 14
Table 10 Cell 1 and Section 20 Cell 3 and 4 Groundwater Elevations 15
Groundwater Model Report—Monarch DENM Gravel Mine Site -ii- January 2023