Geotech Report 02 12 2024

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-02 Subsurface Stormwater Management System Page 6 West Orange, NJ seepage was encountered at depths of 5.5 to 6 feet below the surface immediately above the bedrock. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.82 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at a depth of 2.5 to 3.0 feet. The system should be designed in accordance with the NJDEP Stormwater BMP Manual based on the specific measured permeability rates in each area. We also recommend that the infiltrative surface be covered with a geotextile filter fabric or properly graded soil/aggregate filter material to provide a unform separation layer and infiltrative surface to minimize the transmission of fines and possible soil clogging. Basin (TP-27, TP-28): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +575 to +577 feet. The subsurface conditions revealed in the test pits performed for this study encountered 12 inches of topsoil/vegetation. The topsoil was underlain by clayey soil and extended to the maximum depths explored, 6.5 to 8 feet on bedrock. Groundwater seepage was encountered at depths of 8 feet below the existing ground surface at TP-28. Laboratory tube permeameter testing performed on the clayey sand stratum (silt/clay loam material) resulted in permeability rates of 0.09 inches per hour (KO soils). The area is not suitable for stormwater infiltration. Basin (TP-29, TP-30): The area is partially wooded. Topographic data provided to us indicates that the ground surface elevations range from approximately +570 to +573 feet. The subsurface conditions revealed in the test pits performed for this study encountered 6 inches of topsoil/vegetation. The topsoil was underlain by clayey soil to depths of 2 to 3 feet where bedrock was encountered. Groundwater was not encountered to the maximum depths explored. Laboratory tube permeability testing performed on the silt/clay loam resulted in permeability of less than 0.2 inches per hour (hydraulically restrictive). The area is not suitable for stormwater infiltration. Basin (TP-31, TP-32): The area

ormed on the silt/clay loam resulted in permeability of less than 0.2 inches per hour (hydraulically restrictive). The area is not suitable for stormwater infiltration. Basin (TP-31, TP-32): The area is presently partially open land. Topographic data provided to us indicates that the ground surface elevations range from