3400 RIVERFRONT BLVD Geotech Report 2022-10-25

• • • • • A 42-inch-diameter storm drain line crossing the roadway constructed of reinforced concrete. The pipe invert elevation is approximately 2 to 4 feet. This sanitary sewer line will be • covered by up to 10 feet of new fill (typically around 4 to 10 feet of fill) and will remain in • service. • • A water line in the roadway will be replaced as part of this project. • • Underground telemetry lines for a lift station in the roadway will be replaced as part of this • project. • A storm drain line crossing the roadway that drains to the river will be replaced as part of this project. • . Based on the grading plans for the project prepared by Core Design, Inc. dated March 2015, the grades at the site were raised approximately 0 to 10 feet. Fill heights will generally be greatest • west of the existing Eclipse Mill Road in the area of the drainage Swale. The grading plan • summary shown on Figure 4 identifies the approximate heights of the fills and cuts that were • performed to achieve final grades. • The following sections provide a summary of our settlement analysis and justification for our recommendation to install a surcharge fill. • 5.2.2 Settlement Analysis We performed an analysis to evaluate the potential settlement that will result from raising grades • to final grades. Consolidation of the fine-grained deposits occurs very slowly and is the primary • contributor to long-term settlement of the site. Consolidation of the sand layers occurs very • rapidly as the fill loads are placed and does not contribute to long-term consolidation settlement. . The risk of settlement of the organics in the undocumented fill will be mitigated by installing the buildings on mat foundations. Therefore, the main risk of settlement at this site will be from the • consolidation of the 10-to 20-foot-thick layer of soft to medium stiff silt and organic silt that is • present across most of the site. Deeper soil layers consist of dense to very dense sand or hard silt and will not be susceptible to gradual consolidation and will not contribute to the long-term • consolidation settlement of the site. We modeled consolidation of the soft to medium stiff silt as organic silt using the soil • consolidation properties shown in Table 1. These values were obtained from site consolidation • data or published correlations, as indicated in the table footnotes. • • • • • • • G EODESIGN= 7 Polygon-128-01:091615 •