Geotech Report 04 19 2021

SOR CONSULTING ENGINEERS, INC. Garden Homes Report No. 21-C-12 Proposed Residential Development Page 7 West Orange, NJ In order to achieve the desired site grades; we anticipate that fill will also be required to reach the proposed construction subgrade levels. Prior to the placement of any fill, the soils exposed after the removal of all surface vegetation and topsoil and after excavating to proposed construction subgrade should be thoroughly proofrolled and compacted to a dense and unyielding condition by numerous passes of a large vibrating steel drum compactor. Any localized areas that cannot be compacted to a dense and unyielding condition such as soft clayey soils should be excavated to expose suitable subsoils and backfilled with controlled compacted fill. After proofrolling, fill may be placed as required to reach the desired construction subgrade levels. Fill material may consist of either suitable portions of the on-site soils or imported well-graded sand and gravel containing less than 15 percent by weight passing a U.S. Standard No. 200 sieve. The natural sandy silt and clayey silt soils encountered directly below the surficial topsoil are highly moisture-sensitive and their suitability for immediate use as controlled fill or backfill within building and pavement areas will be dependent upon their moisture content at the time of construction. If the moisture content is even slightly above optimum as determined by the ASTM D-1557 test procedure, these soils will be difficult if not impossible to compact. As such, the sandy silt and clayey silt soils are considered marginal for reuse as controlled fill or backfill within structural areas. These soils would, however, be suitable for use as fill within landscaped areas or berms. Cleaner silty gravelly sandy soils were often found below the sandy silt and clayey silt. These soils are generally less sensitive to changes in moisture and would therefore be more suitable for use as controlled fill or backfill within building and pavement areas. During extensive excavations, the silty gravelly sand should be segregated and reserved for future use as controlled fill. Rock fragments resulting from excavation operations may also be used as fill provided that the fragments are less than 6 inches in maximum dimension and adequately placed to preclude the formation of voids in the fill. Fill containing

vation operations may also be used as fill provided that the fragments are less than 6 inches in maximum dimension and adequately placed to preclude the formation of voids in the fill. Fill containing significant quantities of rock fragments should remain at least 4 feet below finished building and slab subgrade levels so as not to interfere with subsequent foundation and utility installation. In addition, depending upon the gradation characteristics of the rock fill, it may be necessary to place a layer of geotextile fabric between the rock fragments and overlying layers of soil fill in order to prevent migration