Geotech Report 04 04 2024

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 SUPPLEMENTARY SUBSURFACE INVESTIGATION REPORT SUBSURFACE STORMWATER MANAGEMENT SYSTEM WEST ORANGE, NEW JERSEY FOR GARDEN HOMES/WEST ESSEX HIGHLANDS, INC. SHORT HILLS, NEW JERSEY Prepared by: Sor Consulting Engineers, Inc. 98 Sand Park Road Cedar Grove, New Jersey 07009 Report No. 24-C-11 Job No. 24-C-02 April 4, 2024

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. April 4, 2024 Job No. 24-C-02 Report No. 24-C-11 Garden Homes / West Essex Highlands, Inc. 820 Morris Turnpike, Suite 301 Short Hills, NJ 07078 Attention: Mark Hoffman E-Mail: MarkH@gardenhomes.com Re: Supplementary 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 supplementary 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 further 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 * present recommendations for stormwater infiltration system design.

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-11 Subsurface Stormwater Management System Page 2 West Orange, NJ To accomplish this, an exploration program consisting of eight (8) test pits was conducted on March 28, 2024. The test pits were performed by D. Willis Excavating, Inc. using a Case Extendhoe rubber tire backhoe and extended to depths ranging from 2 to 8 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 geologist from Sor Consulting Engineers. Our geologist 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 ||. 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 eight (8) 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 of higher ridges formed by intruding magma of Jurassic age. Locally, glacial till deposits

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

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-11 Subsurface Stormwater Management System Page 4 West Orange, NJ silty gravelly sand at TP-42 and extended to the maximum depth explored, 4 feet. Bedrock was encountered below the sandy or clayey soil at depths of 4 to 5 feet. Groundwater seepage was encountered at depths of 4 to 5 feet below the existing ground surface on top of bedrock and determined to be trapped water. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rate of 0.95 inches per hour (K2 soils). However, silt/clay loam encountered at TP-43 resulted in permeability rates less than 0.2 inches per hour (hydraulically restrictive zone). We recommend that the stormwater management system be hydraulically connected to loam materials found at a depth of 2 feet (TP-42). 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. Test Pit 43 encountered clayey soil underlain by bedrock and not suitable for stormwater infiltration. Basin (TP-44 and TP-45): The area is presently a wooded site. Topographic data provided to us indicate that ground surface elevations range from approximately +570 feet to +574 feet. The subsurface conditions revealed in the test pits performed for this study encountered 6 to 10 inches of topsoil/vegetation. At TP-44, the topsoil was underlain by clayey soil and extended to maximum depths explored. Basalt bedrock was encountered beneath the clayey material at a depth of 2 feet. Groundwater seepage was encountered above the bedrock and considered trap water. Due to the presence of clayey soils which is hydraulically restrictive and shallow bedrock presence, the area is not suitable for stormwater infiltration design. At TP-45, the topsoil was underlain by clayey soil and extended to a depth of 2.5 feet below the surface. The clayey soil was underlain by silty gravelly sand (loam material) and extended to the maximum depths explored, 8 feet. Bedrock was encountered

and extended to a depth of 2.5 feet below the surface. The clayey soil was underlain by silty gravelly sand (loam material) and extended to the maximum depths explored, 8 feet. Bedrock was encountered beneath the loam at a depth of 8 feet below surface. Groundwater seepage was encountered at depths immediately above the bedrock and considered

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-11 Subsurface Stormwater Management System Page 5 West Orange, NJ trap water. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.95 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 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. Basin (TP-46 and TP-47): The area is presently a partially wooded site. Topographic data provided to us indicate that ground surface elevations range from approximately +574 feet to +578 feet. The subsurface conditions revealed in the test pits performed for this study encountered 15 inches of topsoil/vegetation. The topsoil was underlain by clayey soil and extended to a depth of 4 feet below the surface. The clayey soil was underlain by reddish brown silty gravelly sand (loam material) extended to the maximum depths explored, 5 to 8 feet where bedrock was encountered. Groundwater seepage was encountered at depths of 5 to 8 feet below the surface immediately above the bedrock and considered trap water. Laboratory tube permeameter testing performed on the silty gravelly sand stratum (loam material) resulted in permeability rates of 0.99 inches per hour (K2 soils). We recommend that the stormwater management system be hydraulically connected to these materials found at a depth of 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.

SOR CONSULTING ENGINEERS, INC. Garden Homes/West Essex Highlands, Inc. Report No. 24-C-11 Subsurface Stormwater Management System Page 6 West Orange, NJ 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. Sor Consulting Engineers appreciates the opportunity to be of assistance with this project. Should there be any questions concerning the information provided herein, please do not hesitate to contact us. The following appendices are attached and complete this report: Appendix |: Exploration Location Plan Appendix II: Test Pit Logs TP-40 through TP-47 Burmeister and USDA Soil Classification System Appendix Ill: Laboratory Soil Test Results Appendix IV: Limitations Respectfully submitted, SOR CONSULTING ENGINEERS, INC. Atilla Sencar, P.E. Senior Engineer AS/gs cc: Anderson Consulting Service, LLC Attn: Paul Anderson, P.E., P.P., CME E-Mail: pandersonpe@gmail.com

APPENDIX | EXPLORATION LOCATION PLAN

NY7d ONUSSL IOS TVESAO Tse IN ANNOD SST ONVHO ISD «1 SNMOL 27.01 61 30018 SCNWAHOI X4SS ILS IM vid 3118 TWAld Ohy RWIS tie i a sipitlocebions LOCATION. RVED SO PROPOSED NEW SOIL PERMEABILITY AND SEASONAL 5 8 3 g é 4 { 4 & 5 a & = & ¢ 4 A E s £ 1 e ci \\ >) 2 Nea) om,