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