WORK PLANS - Laserfiche WebLink

Home Browse Search

Geotechnical Engineering and Geological Elazard Study Lincoln Elementary School Modernization Project Manteca, California Page 10 • The presence of potentially liquefiable soils requiring engineered fill below foundations per Section 6.2.2. • Grading considerations to compact surface soils. Specific conclusions and recommendations addressing these geotechnical considerations, as well as general recommendations regarding the geotechnical aspects of design and construction, are presented in the following sections. 7.2 GRADING AND EARTHWORK RECOVIlVIENDATIONS All grading and site work should be performed in accordance with the 2013 CBC, Title 24, Chapter 33 (Safeguards During Construction), Appendix J (Grading),and Chapter 18A (Soils and Foundations), and with the recommendations of the Geotechnical Engineer of Record during construction. Where the recommendations of this report and the cited sections of Title 24 are in conflict, the owner should request clarification from the Geotechnical Engineer of Record. The recommendations of this report should not be waived without the consent of the Geotechnical Engineer of Record for the project. Recommendations for additional work and construction monitoring are contained in later sections of this report. 7.2.1 Site Preparation At the time of our field exploration, the site was generally developed with existing buildings, hardscapes, and grass. Areas to support slabs, pavements, foundations, and new engineered fills should be stripped of all vegetation, debris, organic topsoil, or any existing non -engineered fill or other unsuitable material or soil. Stripping should extend at least 5 feet beyond the limits of the proposed improvements. Soils containing more than 3 percent organic material by weight over baseline conditions should be considered organic. Organic topsoil is present in grass covered areas. Stripping depths should be detennined at the time of grading by the Geotechnical Engineer of Record or a qualified representative. For planning, an average stripping depth of 4 inches may be used where grass is present. Any organic -laden material which is free from debris may be stockpiled for later use in non-structural areas where approved by the owner, but such material should not be used for engineered fill. 7.2.2 Overexcavation Overexcavation of existing soils should extend to a depth of at least 2 feet below final subgrade for slab - on -grade, and 2 feet below spread or perimeter footings. In areas to support concrete flatwork, hardcourt areas, and any non-structural improvements susceptible to vertical movement, we recommend that the upper 2 feet, as measured from existing grade be removed and replaced with engineered fill in accordance with Section 7.2.5, Engineered Fill Placement. The zone of overexcavation should extend laterally at least 5 feet beyond the perimeter of the proposed improvements. If soft or yielding soils are exposed by this processing, excavation should continue until stiff, non -yielding soils are encountered. The depth and extent of required overexcavations should be approved in the field by the Geotechnical Engineer of Record prior to placement of fill or improvements. 7.2.3 Subgrade Preparation After overexcavation has been achieved, the exposed subgrade should be scarified to a depth of 12 inches, uniformly moisture conditioned to between I to 3 percent over optimum moisture, and compacted to achieve a minimum relative compaction of 90 percent of the ASTM D 155 7 maximum dry density. Field density tests should be taken to verify compaction of the prepared subgrade in these areas. ow W 13-