J_2024 05 09_West Orange Stormwater Management Plan

PSE&G May 17.2011 Page 8 Temporary construction excavations should comply with the most recent OSHA Excavation Guidelines (29 CFR Part 1926) assuming that the existing fill materials and natural clay sands soils prevalent at the site are Type “C” soils. The guidelines indicate for Type “C” soils, simple excavations less than 20 feet in depth shall have a maximum allowable slope of 1.5 horizontal to 1 vertical. Sloughing of the excavation sidewalls could occur and flattening of the slopes or use of plates, sheets, trench boxes or other types of temporary excavation support may be required to minimize the size of the excavations or to prevent undermining of adjacent equipment. It should be the contractor’s responsibility to evaluate and provide a properly designed excavation support system, maintain safe excavations at all times and prevent undermining of existing structures and equipment. The near surface excavated fill is expected to consist primarily of clayey sand and silts and clays. The sandier soils would be considered suitable for reuse as controlled compacted fill and backfill provided they are at and maintained at moisture contents which would allow them to be properly compacted. Any encountered clayey soils would be poorly suited for reuse due to their moisture sensitive nature. Variations in the nature and composition of the fill materials present at the site should be anticipated. A determination regarding the suitability of excavated fill materials for reuse as structural backfill adjacent to the foundations should be made at the time of construction by a qualified geotechnical engineer. Occasional cobbles and boulders were encountered and weathered basalt was encountered at nine feet in SBH-2 and as shallow as five feet in a previous test pit performed by MTA. As such, large excavation equipment with rock teeth could be required to penetrate the surface of the weathered basalt if excavations extend to these levels.