Geotech Report 05 23 2023

SOR CONSULTING ENGINEERS, INC. Geotechnical Engineering - Materials Testing - Forensic Studies 98 Sand Park Rd., Cedar Grove, NJ 07009 (973) 239-6001 Fax (973) 239-8380 SUBSURFACE INVESTIGATION REPORT SUBSURFACE STORMWATER MANAGEMENT SYSTEM WEST ORANGE, NEW JERSEY FOR GARDEN HOMES SHORT HILLS, NEW JERSEY Prepared by: Sor Consulting Engineers, Inc. 98 Sand Park Road Cedar Grove, New Jersey 07009 Report No. 23-C-17 Job No. 23-C-16 May 23, 2023

SOR CONSULTING ENGINEERS, INC. Geotechnical Engineering - Materials Testing - Forensic Studies 98 Sand Park Rd., Cedar Grove, NJ 07009 (973) 239-6001 Fax (973) 239-8380 www.sorlabs.com Kamil Sor, Ph.D. Orhun Sor, P.E. Atilla Sencar, P.E. May 23, 2023 Job No. 23-C-16 Report No. 23-C-17 Garden Homes 820 Morris Turnpike, Suite 301 Short Hills, NJ 07078 Attention: Mark Hoffman E-Mail: MarkH@gardenhomes.com Re: Subsurface Investigation Report Subsurface Stormwater Management System West Orange, New Jersey INTRODUCTION Sor Consulting Engineers, Inc. (SCE) is pleased to present the results of a subsurface investigation performed for a proposed stormwater management system to be constructed at a site in West Orange, New Jersey. The site is identified as Lot 32, Block 179 on the municipal tax maps. Based on a concept plan dated September 23, 2022, the proposed development will reportedly include a combination of stormwater detention basins as well as underground perforated pipes installed at various locations beneath pavements. PURPOSE AND SCOPE OF WORK The purpose of this study was to: e explore the subsurface soil and groundwater conditions within the proposed stormwater management system area; e estimate the geotechnical engineering properties of the encountered subsurface materials including soil permeability; e estimate the depth to the seasonal high water table; and e present recommendations for stormwater infiltration system design.

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 2 West Orange, NJ To accomplish this, an exploration program consisting of fourteen (14) test pits was conducted on May 8 and 9, 2023. The test pits were performed by D. Willis Excavating, Inc. using a Case Extendhoe rubber tire backhoe and extended to depths ranging from 5 to 16 feet below the existing ground surface. Tube and bag soil samples suitable for identification and laboratory testing purposes were extracted from the test pits. Upon completion, the test pits were backfilled so as not to leave any open holes. The test pits were performed under the direct technical observation of a licensed geotechnical engineer from Sor Consulting Engineers. Our engineer logged the explorations during excavation and sampled the soils to obtain the appropriate subsurface information. The exploration locations are shown relative to the existing site features on the Exploration Location Plan included in Appendix | of this report. Detailed descriptions of the encountered subsurface conditions are presented on the individual test pit logs included in Appendix II. The subsurface profile and soil conditions at the test pit locations were logged in general accordance with the terminology and protocols described in the NJDEP Stormwater BMP Manual Appendix E and USDA and Burmeister Soil Classification Systems. All soil samples were brought to our office where they were further examined in our soil mechanics laboratory. Mechanical grain size distribution, moisture content and falling head tube permeability test were performed on fourteen samples to assist in sample identification and evaluation of their engineering soil properties. Laboratory test results are presented in Appendix III. The results of the subsurface exploration and geotechnical laboratory testing programs have provided the basis for our engineering analysis and geotechnical recommendations. The following discussions of our findings and recommendations are subject to the limitations contained in Appendix IV of this report. SITE CONDITIONS Geologic Overview: The subject is located within the New Jersey Piedmont Physiographic Province. The province is primarily a low rolling plain divided by a series

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 3 West Orange, NJ of higher ridges formed by intruding magma of Jurassic age. Locally, glacial till deposits 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 A (TP-A1, TP-A2): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +542 to +546 feet. The preliminary bottom of basin elevation is set at + 540 feet. The subsurface conditions revealed in the test pits performed for this study encountered 8 inches of topsoil/ vegetation. The topsoil was underlain by clayey soil and extended to depths of 2 to 2.5 feet below the surface. The clayey soil was underlain by brown silty gravelly sand and extended to the maximum depth explored, 13 feet. Groundwater seepage was encountered at depths of 7 feet below the existing ground surface. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.64 to 1.39 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at depths of 2 to 2.5 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

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 4 West Orange, NJ provide a unform separation layer and infiltrative surface to minimize the transmission of fines and possible soil clogging. Basin B (TP-B1, TP-B2): The area is presently a wooded site. Topographic data provided to us indicates that the ground surface elevations range from approximately +544 to +546 feet. The preliminary bottom of basin elevation is set at + 540 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 depths of 4 to 5 feet below the surface. The clayey soil was underlain by brown silty gravelly sand and extended to the maximum depth explored, 13 to 15 feet. Groundwater seepage was encountered at depths of 8 to 9 feet below the existing ground surface. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.89 to 1.12 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at depths of 4 to 5 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. HDPE C (TP-C1, TP-C2): The area is presently a wooded site. Topographic data provided to us indicate that ground surface elevations range from approximately +558 feet to +560 feet. The preliminary bottom of HDPE system is set at + 557 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 depths of 3.5 to 4 feet below the surface. The clayey soil was underlain by silty gravelly sand (loam material) extended to depths of 5 to 5.5 feet. Basalt bedrock was encountered beneath the loam material. Groundwater was encountered at depths of 4.0 to 4.5 feet below the surface. Due to the presence of clayey soils which is

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 5 West Orange, NJ hydraulically restrictive, high water table and shallow bedrock presence, the area C is not suitable for stormwater infiltration design. HDPE D (TP-D1, TP-D2): The area is presently a wooded site. Topographic data provided to us indicate that ground surface elevations range from approximately +576 feet to +580 feet. The preliminary bottom of HDPE system is set at + 570 feet. The subsurface conditions revealed in the test pits performed for this study encountered 8 to 12 inches of topsoil/vegetation. The topsoil was underlain by clayey soil and extended to a depth of 2 feet below the surface. The clayey soil was underlain by silty gravelly sand (loam material) extended to the maximum depths explored, 9 to 16 feet. TP-D2 encountered bedrock at 9’ below the surface. Groundwater seepage was encountered at depths of 6 to 10 feet below the surface. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.62 to 2.64 inches per hour (K2 to K3 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at a depth of 2 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. HDPE E (TP-E1, TP-E2): The area is presently a wooded site. Topographic data provided to us indicate that ground surface elevations range from approximately +582 feet to +590 feet. The preliminary bottom of HDPE system is set at + 586 feet. The subsurface conditions revealed in the test pits performed for this study encountered 8 inches of topsoil/vegetation. The topsoil was underlain by clayey soil and extended to depths of 2.5 to 3.0 feet below the surface. The clayey soil was underlain by brown silty gravelly sand (loam material) extended to the maximum depths explored, 12 to 14 feet. Groundwater seepage was encountered at depths of 7 to 9 feet below the surface. Laboratory tube

ain by brown silty gravelly sand (loam material) extended to the maximum depths explored, 12 to 14 feet. Groundwater seepage was encountered at depths of 7 to 9 feet below the surface. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam

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. .

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 23-C-17 Subsurface Stormwater Management System Page 7 West Orange, NJ Basin G (TP-G1, TP-G2): The area is presently open land. Topographic data provided to us indicates that the ground surface elevations range from approximately +536 to +538 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 4 to 8 inches of topsoil/ vegetation. The topsoil was underlain by clayey soil and extended to depths of 1.5 to 4 feet below the surface. The clayey soil was underlain by brown silty gravelly sand and extended to the maximum depth explored, 15 to 16 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 0.74 to 0.95 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at depths of 1.5 to 4 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. 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.