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 7 West Orange, NJ approximately +602 to +604 feet. The subsurface conditions revealed in the test pits performed for this study encountered 8 to 18 inches of topsoil/vegetation. The topsoil was underlain by silty gravelly sand and extended to the maximum depth explored, 10 feet. Groundwater or seasonal high groundwater was not encountered at the maximum depths explored. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.61 to 0.94 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found beneath the topsoil. 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-33 through TP-38): The area is partially wooded. Topographic data provided to us indicates that the ground surface elevations range from +578 to +594 feet. The subsurface conditions revealed in the test pits performed for this study encountered 4 to 10 inches of topsoil/vegetation. The topsoil was underlain by clayey soil to depths of 1.5 to 3 feet at TP-33, 34, and 35. The topsoil and clayey soil was underlain by silty gravelly sand and extended to maximum depths explored. At TP-37 and 38 bedrock was encountered at depths of 5 to 6 feet below surface. Groundwater was only encountered at Test Pits 33, 34, and 36 at depths of 9 to 11 feet below surface. Laboratory tube permeameter testing performed on the silty gravelly sand (loam material) resulted in permeability rates of 0.45 to 0.82 inches per hour (K1 to K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found below the topsoil or clayey soil. The system should be designed in accordance with the NJDEP Stormwater BMP Manual based on the specific measured permeability rates in each area. We recommend that the infiltrative surface be covered

. The system should be designed in accordance with the NJDEP Stormwater BMP Manual based on the specific measured permeability rates in each area. We recommend that the infiltrative surface be covered with a geotextile filter fabric or properly graded soil/aggregate filter