2710 14TH ST BLDG A Geotech Report 2023-12-29

4.5. Earthwork 4.5.1. Excavation Considerations Planned final site grades may be close to the existing grades. Based on the subsurface soil conditions encountered in the test pits, we expect the soils at the site may be excavated using conventional heavy-duty construction equipment. The soils encountered in the upper portions of the Site 1 test pits consisted of dense to very dense glacial till with variable silt and gravel content that can be difficult to excavate. Glacial deposits in the area commonly contain cobbles and boulders that may be encountered during excavation. Accordingly, the contractor should be prepared to deal with cobbles and boulders. The fill and native soils contain sufficient fines (material passing the U.S. Standard No. 200 sieve) to 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 construction will help reduce earthwork costs and increase the potential for using the native soils as structural fill. 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 and could potentially generate significant quantities of mud if not protected. 4.5.2. Clearing and Site Preparation Construction of the planned buildings will require demolition of existing buildings, utilities and significant clearing and stripping. We expect that there will be demolition of the existing post -WWII era residential buildings, existing asphalt pavement, sidewalks, curbs, light poles, and utilities. Concrete rubble and asphalt pavement may be recycled and reused as structural fill, otherwise it should be removed from the site along with other construction debris. Based on our explorations and site observations, the asphalt pavement is about 3 inches thick. Existing underground utilities should be dealt with according to Section 4.5.3 of this report. 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 organic materials and topsoil. Based on our explorations and site observations, we estimate that stripping depths will be on the order of 3 to 6 inches to remove topsoil within existing landscape and lawn areas. Greater stripping depths will be needed in more densely vegetated areas and where large tree root systems exist. The stripped organic soils can be stockpiled and used later for landscaping purposes or may be spread over disturbed areas following completion of grading. If spread out, the organic strippings should be placed in a layer less than 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. J GEOENGINEERS� October30, 2019 Page ll File No. 21288-002-00