Geotech Report 05 23 2023

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 6 West Orange, NJ material) resulted in permeability rates of 0.68 to 0.69 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. It appears that the lower section of the ware will be filled to obtain the proposed finished grades. We recommend that clayey soil should be removed prior to fill placement. The fill material should consist of granular soil and should be tested for permeability. 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 F (TP-F1, TP-F2): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +608 to +610 feet. The preliminary bottom of basin elevation was not provided. The subsurface conditions revealed in the test pits performed for this study encountered 10 to 12 inches of topsoil/ vegetation. The topsoil was underlain by clayey soil and extended to a depth 3 feet below the surface at TP-F1 only. The clayey soil or topsoil was underlain by brown silty gravelly sand and extended to the maximum depths explored, 12 to 13 feet. Groundwater seepage was encountered at depths of 8 feet below the existing ground surface. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 1.85 to 2.32 inches per hour (K2 to K3 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at depths of 1 to 3 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

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. .