Langan Rebuttal Report 9 15 2025

Color 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 Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 323,263 17 65 1 1 1 690 1.676 640 TP-4 TP-14 TP-7 LB-3 12 ft LB-13 Utility Trench (8 ft wide) 590 Factor of Safety: 1.676 Current Slip Surface Number: 271 TP-5 LB-4 540 TP-6 Elevation 490 440 Critical Failure Surface (CFS) 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

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 50 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 = 50) 800 900 1,000 1,100 1,200

Color 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 Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 323,263 17 50 1 1 1 690 1.676 640 TP-4 TP-14 TP-7 LB-3 Utility Trench (8 ft wide) 12 ft LB-13 590 Factor of Safety: 1.676 Current Slip Surface Number: 271 TP-5 LB-4 540 TP-6 Elevation 490 440 Critical Failure Surface (CFS) 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Proposed Condition (GSI = 50) 800 900 1,000 1,100 1,200

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 6.468 640 TP-7 TP-4 LB-3 Utility Trench (8 ft wide) B-13 TP-14 590 Factor of Safety: 6.468 Current Slip Surface Number: 217 TP-5 LB-4 540 TP-6 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Existing Condition (GSI = 65) 800 900 1,000 1,100 1,200

Color 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 Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 323,263 17 65 1 1 1 690 6.448 640 TP-4 TP-14 TP-7 LB-3 Utility Trench (8 ft wide) 12 ft LB-13 590 Factor of Safety: 6.448 Current Slip Surface Number: 217 TP-5 LB-4 540 TP-6 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

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 50 1 4.441 640 TP-7 TP-4 Utility Trench (8 ft wide) LB-3 B-13 TP-14 590 Factor of Safety: 4.441 Current Slip Surface Number: 217 TP-5 LB-4 540 TP-6 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Existing Condition (GSI = 50) 800 900 1,000 1,100 1,200

Color 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 Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 323,263 17 50 1 1 1 690 4.424 640 TP-4 TP-14 TP-7 LB-3 Utility Trench (8 ft wide) 12 ft LB-13 590 Factor of Safety: 4.424 Current Slip Surface Number: 217 TP-5 LB-4 540 TP-6 Elevation 490 440 390 340 290 240 190 0 100 200 300 400 500 600 700 Distance Cross Section B_Proposed Condition (GSI = 65) 800 900 1,000 1,100 1,200

Cross Section C (Static Condition)

Color 660 Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) UCS Intact (psf) Intact Rock Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 323,263 17 37 1 1 Bedrock 180 Decomposed Rock/Very Dense Granular Soil 135 0 38 1 Medium sand 120 0 32 1 Retaining Wall 150 Topsoil 115 0 30 1 640 1 1.589 620 Factor of Safety: 1.589 Current Slip Surface Number: 401 NLB-2 NTP-1 600 NTP-2 NLB-1 Property Line Elevation 580 560 540 520 500 480 460 440 0 100 200 Distance Cross Section C_Existing Condition (GSI = 37) 300 400

Color 660 Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Bedrock 180 Decomposed Rock/Very Dense Granular Soil UCS Intact (psf) Intact Rock Parameter mi Geological Strength Index GSI Disturbance Factor D Piezometric Surface 135 0 38 323,263 17 37 1 1 1 Medium sand 120 0 32 1 Retaining Wall 150 Topsoil 115 0 30 1 1 640 1.589 620 NLB-2 Factor of Safety: 1.589 Current Slip Surface Number: 401 NTP-1 600 NTP-2 NLB-1 Property Line Elevation 580 560 540 520 500 480 460 440 0 100 200 Distance Cross Section C_Proposed Condition (GSI = 37) 300 400