Geotech Report 04 04 2024

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-11 Subsurface Stormwater Management System Page 3 West Orange, NJ can be found deposited directly by glacial ice during the Wisonsinian glaciation. The bedrock underlaying the site is composed of a Jurassic aged basalt formation called the Preakness Basalt, a fine to coarse grained basalt that composes the second Watchung Mountain. Surface Features: The entire property is currently moderately to heavily wooded and contains some areas of rock outcrops. Large boulders are scattered throughout the site. Several areas identified as wetlands traverse the property in a general northeast to southwest orientation. Surface grades throughout the site reportedly range from a high of Elevation +630 feet in the extreme northern section to Elevation +530 feet along the townhomes. STORMWATER MANAGEMENT SYSTEM DESIGN CONSIDERATIONS Basin (TP-40 and TP-41): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +560 to +562 feet. The subsurface conditions revealed in the test pits performed for this study encountered 6 to 10 inches of topsoil/vegetation. The topsoil was underlain by clayey sand soil and extended to depths of 3 to 5 feet below the surface. The clayey sand soil was underlain by bedrock where refusal was encountered. Groundwater seepage was encountered at TP-41 immediately above the bedrock. Seepage was determined to be trapped water. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.56 to 0.70 inches per hour (K1 to K2 soils). However, bedrock encountered at depths of 3 to 5 feet below surface are considered hydraulically restrictive and not suitable for stormwater infiltration. Basin (TP-42 to TP-43): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +598 to +602 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 and extended to a depth of 2 feet below the surface at TP-42 and extended to maximum depths explored at TP-43. The clayey soil was underlain by reddish brown