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 8 West Orange, NJ material to provide a uniform separation layer and infiltrative surface to minimize the transmission of fines and possible soil clogging. Basin (TP-39): The area is presently open land. The topographic data provided to us indicates that the ground surface elevations is approximately +537 feet. The preliminary bottom of basin elevation is set at +530 feet. The subsurface conditions revealed in the test pits performed for this study encountered 6 inches of topsoil. The topsoil was underlain by clayey soil to a depth of 3 feet below surface. The clayey soil was underlain by reddish brown silty gravelly sand (loam material) and extended to the maximum depth explored, 10 feet. Groundwater was encountered at a depth of 9 feet below surface. Laboratory tube permeameter testing performed on the loam material resulted in permeability rate of 0.81 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found below the depth of 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 uniform separation layer and infiltrative surface to minimize the transmission of fines and possible soil clogging. RECOMMENDED SERVICES It is recommended that Sor Consulting Engineers be provided the opportunity for a general review of the final design and specifications to assure that the stormwater management system recommendations are properly interpreted and implemented in the construction documents. We also recommend that controlled compacted fill and backfill operations as well as stormwater management system subgrades be observed by a geotechnical engineer from our firm. This is to ensure compliance with the recommendations contained herein and to address any changes in the subsurface conditions that were not disclosed by the test pits.