3535 RIVERFRONT BLVD Geotech Report 2023-02-22

September 24, 2018 HWA Project No. 2015-061-21 of the loads is a function of the relative density,permeability, and water content of the soil. In general, soil settlements can be divided into two categories: elastic, or immediate, settlement and consolidation settlement. Immediate (elastic) settlement takes place during construction. Consolidation settlement occurs over time. Elastic settlement is expected to occur as a result of this project; however, the anticipated magnitude is so low that we do not expect elastic settlement to be a design concern for the proposed improvements. Consolidation settlement results from the application of static loading on fine-grained soil deposits that are saturated and have not previously experienced similar loading conditions. Consolidation settlement occurs as both primary consolidation (short term consolidation) and secondary consolidation (long term consolidation). Both of these mechanisms are described below. Primary consolidation: Primary consolidation begins immediately upon the application of load and is the result of pore water being expelled from the void space within the soil unit. As load is applied, the pore water pressure increases within the soil unit and slowly decreases as the pore water is expelled from the soil. As this process continues the void space between the soil particles is reduced and the volume of the soil deposit decreases. This decrease in the volume results in a reduction in the thickness of the soil unit which manifests as settlement at the ground surface. The magnitude of primary consolidation is dependent on the magnitude of the applied load, the geometry of the compressible soil unit, with respect to the applied load, and the compressibility properties of the soil. Secondary compression: Secondary compression is associated with structural deformation within the soil as the result of applied load. In mineral soils the secondary compression is relatively small in comparison to the primary consolidation. However, secondary compression in organic soils is much larger due to the potential for cellular deformation within the organic ' material. Secondary compression continues for many years after application of load. Typically, secondary compression is calculated over a design life of 50 years. The magnitude of the secondary compression settlement is difficult to predict, but is typically 5% to 10% of the settlement that occurs as primary consolidation for most non-organic soils. For highly organic soils, on the other hand, secondary compression has been observed to be a significant amount of the total settlement. Based upon our experience, we have assumed secondary settlement of the organic deposits will be about 25% of its estimated primary settlement. Anticipated Settlement Magnitude with Standard Construction Settlement analyses was performed to evaluate the magnitude of settlement due to proposed grade increase throughout the project site (an average 3 foot grade increase assumed across the site) assuming no settlement mitigation measures were implemented. Additionally, settlement analyses were performed to evaluate the magnitude of settlement associated with construction of a restroom structure applying a 2,000 psf bearing pressure. Settlement analyses were performed based on existing equations governing the primary and secondary consolidation and stress redistribution established by Boussinesq theory. Consolidation parameters where estimated Final Geotecluiical Report-3-Acre Park.docx 12 HWA GeoSciences Inc.