Langan Rebuttal Report 9 15 2025

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 65 1 1 1 2.204 640 Utility Trench (8 ft wide) 590 Factor of Safety: 2.204 Current Slip Surface Number: 327 540 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Existing Condition (GSI = 65) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 1 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 1 Medium Dense Sand Mohr-Coulomb 120 0 32 1 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 65 1 1 1 2.201 640 8.2753 ft TP-1 TP-8 LB-1 Utility Trench (8 ft wide) TP-2 590 Factor of Safety: 2.201 Current Slip Surface Number: 327 TP-3 540 LB-2 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 50 1 1 1 2.204 640 Utility Trench (8 ft wide) 590 Factor of Safety: 2.204 Current Slip Surface Number: 327 540 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Existing Condition (GSI = 50) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 50 1 1 1 2.201 640 8.2753 ft TP-1 Utility Trench (8 ft wide) TP-8 LB-1 TP-2 590 Factor of Safety: 2.201 Current Slip Surface Number: 327 TP-3 540 LB-2 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Proposed Condition (GSI = 50) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 65 1 1 1 3.292 640 Utility Trench (8 ft wide) 590 Factor of Safety: 3.292 Current Slip Surface Number: 221 540 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 65 1 1 1 3.284 640 8.2753 ft TP-1 Utility Trench (8 ft wide) TP-8 LB-1 TP-2 590 Factor of Safety: 3.284 Current Slip Surface Number: 221 TP-3 540 LB-2 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 50 1 1 1 3.292 640 Utility Trench (8 ft wide) 590 Factor of Safety: 3.292 Current Slip Surface Number: 221 540 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Existing Condition (GSI = 50) 800 900 1,000 1,100 1,200

Color 690 Name Slope Stability Material Model Bedrock Hoek-Brown 180 Decomposed Rock/Very Dense Granular Soil Mohr-Coulomb 135 0 38 Dense to Very Dense Mohr-Coulomb Sand 125 0 34 Medium Dense Sand Mohr-Coulomb 120 0 32 Top Soil 115 0 30 Mohr-Coulomb Unit Weight (pcf) Effective Effective UCS Cohesion Friction Intact (psf) Angle (psf) (°) Intact Geological Disturbance Piezometric Rock Strength Factor D Surface Parameter Index GSI mi 323,263 17 50 1 1 1 3.284 640 8.2753 ft TP-1 Utility Trench (8 ft wide) TP-8 LB-1 TP-2 590 Factor of Safety: 3.284 Current Slip Surface Number: 221 TP-3 540 LB-2 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section A_Proposed Condition (GSI = 50) 800 900 1,000 1,100 1,200

Cross Section B (Static Condition)

Color 690 Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Bedrock 180 Decomposed Rock/Very Dense Granular Soil 135 0 38 Dense to Very Dens Sand 125 0 34 Medium sand 120 0 32 Top soil 115 0 30 UCS Intact (psf) Intact Rock Geological Parameter Strength mi Index GSI Disturbance Factor D Piezometric Surface 323,263 17 1 1 65 1 1.669 640 TP-7 TP-4 LB-3 B-13 Utility Trench (8 ft wide) TP-14 590 Factor of Safety: 1.669 Current Slip Surface Number: 271 TP-5 LB-4 540 TP-6 Elevation 490 Critical Failure Surface (CFS) 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Existing Condition (GSI = 65) 800 900 1,000 1,100 1,200