2621 ROCKEFELLER AVE Geotech Report 2022-10-25

1111 1_ advance outwash deposits. The glacial encountered included fill, and dense to very dense glacial till ando as p soils may require a large excavator to accomplish the excavations, Glacial soils in the area commonly contain boulders that may be encountered during excavation. Accordingly, the contractor should be prepared to deal with boulders,if encountered. I The native glacial till soils contain significant fines (material passing the U.S. standard No. 200 sieve) and will be highly moisture-sensitive and susceptible to disturbance, especially when wet. Ideally, earthwork should be undertaken during extended periods of dry weather when the surficial soils will be less susceptible to disturbance and provide better support for construction equipment. Dry weather 4 construction will help reduce earthwork costs and increase the potential for using the native soils as fill. I Trafficability on the site is not expected to be difficult during dry weather conditions. However, the native soils will be susceptible to disturbance from construction equipment during wet weather conditions and pumping and rutting of the exposed soils under equipment loads may occur. -11 Clearing and Site Preparation Construction of the proposed building will require demolition of the existing residences, sidewalks, and -11 other appurtenant structures. Concrete may be recycled and reused as structural fill; otherwise,it should be removed from the site along with other construction debris. All existing utilities should be removed from the building footprint and rerouted if needed. 1 Areas to be developed or graded should be cleared of surface and subsurface deleterious matter including debris, shrubs, trees and associated stumps and roots. Graded areas should be stripped of 1 organic soils. Organic soils are likely only associated with the existing landscape areas. The organic soils can be stockpiled and used later for landscaping purposes or may be spread over I disturbed areas following completion of grading. If spread out, the organic strippings should be in a layer less that 1 foot thick, should not be placed on slopes greater than 3H:1V and should be track-rolled to a uniformly compacted condition. Materials that cannot be used for landscaping or protection of disturbed areas should be removed from the project site. Subgrade Preparation Prior to placing new fills or gravel below on-grade floor slabs, subgrade areas should be proofrolled to locate any soft or pumping soils. Prior to proofrolling, all unsuitable soils should be removed from below the building area. Unsuitable fill exists along the east side of the building. We recommend that at least the upper 2 feet of existing fill be removed from under the garage slab and be replaced by structural fill. Proofrolling can be completed using a piece of heavy tire-mounted equipment such as a loaded dump truck. During wet weather,the exposed subgrade areas should be probed to determine the ll extent of soft soils. If soft or pumping soils are observed they should be removed and replaced with structural fill. I After completing the proofrolling, the subgrade areas should be recompacted to a firm and unyielding condition, if possible. The degree of compaction that can be achieved will depend on when the construction is performed. If the work is performed during dry weather conditions, we recommend that all subgrade areas be recompacted to at least 95 percent of the maximum dry density (MDD) in • accordance with the American Society for Testing and Materials (ASTM) D 1557 test procedure (modified Proctor). If the work is performed during wet weather conditions, it may not be possible to 11 File No.12547-001-00 Page 4 GEOENGINEERS IFebruary 3,2006