Agenda - Council - 09/14/2021 - Laserfiche WebLink

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4.0 DISCUSSION AND RECOMMENDATIONS 4.1 Proposed Construction We understand the project will consist of constructing an approximate 270 lot residential development including the associated streets underground utilities and stormwater ponds. Specific architectural, structural or civil construction plans were not available at the time of this geotechnical evaluation. We anticipate the new homes will include one or two stories above grade with partial to full depth basements. We anticipate below grade construction consisting of cast -in -place concrete or masonry block foundation walls supported on concrete spread footings with the above grade construction likely consisting of wood framing, a pitched roof and asphalt shingles. Based on the assumed construction we estimate wall loadings will range from about 2 to 3 kips (2,000 to 3,000 pounds) per lineal foot and column loads, if any will be less than 75 kips (75,000 pounds). We anticipate that the proposed house pads and street will be constructed near existing site graded so that cuts and fills for permanent grade changes will typically be on the order of 5 feet but given the relatively large elevation changes across the site we anticipate there could be cuts and fills on the order of 10 feet. We have attempted to describe our understanding of the project. If the proposed loads exceed these values, the proposed grades differ by more than 2 feet from the assumed values or if the design or location of the proposed building changes, we should be informed. Additional analyses and revised recommendations may be necessary. 4.2 Discussion Structures existed on north central portion of the project site which we assume will be removed/demolished to make way for the proposed development. We recommend that all remnants of the structures including; foundations, foundation walls, floor slabs and any underground utilities be removed from within the proposed building, roadway, utility and oversize areas and be properly disposed of off -site. The vegetation and topsoil are not suitable for foundation support and will need to be removed from below the building and oversize areas and replaced, as needed, with suitable compacted engineered fill. It is our opinion that the underlying native alluvial soils are generally suitable for foundation support. However, the sand soils had a very loose to loose relative density and will need to be compacted to increase their density to provide adequate foundation support. In addition, some soft clayey soils were encountered in soil boring SB-10 at about 4 1/2 feet below the ground surface and at about 12 feet below the ground surface at soil boring SB-12. The soft clays are not suitable for foundation support and will need to be removed from below the proposed house pad and oversize areas and will either need to be replaced with suitable compacted engineered fill or excavated, dried and recompacted. 6