J_2024 05 09_West Orange Stormwater Management Plan

PSE&G Page 5 Mav 17.2011 Site Conditions Surface Features: The subject site is a fenced switching station with existing equipment at the surface, on-site buildings and below-grade utilities. Topographic information shown on the plans provided to us indicates the surface grades range from about +615 to +630 feet in the northern portions of the site and slope downward to the south and southwest to a low of about +580 feet in the southwest comer of the site adjacent to Mt. Pleasant Avenue. Subsurface Conditions: The subsurface conditions encountered in the test borings performed for this study consisted of the following generalized strata, listed in order of increasing depth: 1) Surface Materials: A thin layer of crushed stone on the order of two inches in thickness was encountered at test boring SBH-1. At SBH-2 the surface materials were comprised of a three inch thick asphalt layer which was underlain by about eight inches of stone. At SBH-3 and 4, a light grass cover over the underlying natural soils was present and at SBH-5, six inches of topsoil was encountered. 2) Fill: The surface materials were underlain by clayey sand and sandy clay fill in Borings SBH-1 and 2 which extended to depths on the order of two and one-half feet below the existing surface grades. At SBH-5, loose clayey silts and clayey sands were encountered to about nine feet that likely represent fill materials from past site grading activities. 3) Clavev Silt and Siltv Clav: The surface materials and fill where present were underlain by stiff clayey silts and silty clays that extended to about 3 to 13 feet below grade. .._ < .• • 4) Clavev Sands: The silts and clays were generally underlain by medium dense to very dense clayey or silty sands extending to depths ranging from about 9 to 23 feet below grade. The clayey sand soils were typically medium dense to dense in relative density. Loose soils were observed in Boring SBH-5 at a depth of about 13 feet. 5) Decomposed and Weathered Basalt Bedrock: The clayey sands were typically underlain by decomposed and weathered basalt bedrock. At SBH-2 decomposed sandstone bedrock as observed above the basalt bedrock at about 9 to 13 feet below grade.