Geotechnical Data Report

This is a Geotechnical Data Report prepared for the City of St. Helens, Oregon, in support of the Wastewater System Capacity Improvements Project focusing on Basins 4 and 6. The report documents subsurface soil and geological conditions at project sites through boring logs, laboratory testing results, and engineering analysis. The geotechnical investigation characterizes soil stratigraphy, bearing capacity, settlement potential, groundwater conditions, and excavation requirements necessary for designing and constructing sanitary sewer infrastructure improvements. The report provides critical data for civil design engineers and contractors to evaluate construction feasibility, recommend appropriate foundation designs, and identify potential construction challenges such as high groundwater tables, unsuitable soil materials requiring removal, or difficult excavation conditions that may impact project scheduling and costs.

The geotechnical data establishes baseline subsurface conditions essential for accurate project cost estimation, construction methodology development, and risk assessment. Findings from boring locations and laboratory analyses of soil samples inform specifications for trench shoring, dewatering requirements, bedding materials, pipe installation standards, and pavement restoration. This technical documentation supports the competitive bidding process by providing all prospective bidders with consistent, verified information regarding site conditions, thereby reducing ambiguity and change order disputes during construction. The report enables contractors to submit more accurate bids based on actual subsurface conditions rather than assumptions, facilitating fair competition and more reliable project cost and schedule forecasting for the City of St. Helens.