Geological_Report_1982__(1).pdf

This is a Geological Report from 1982 related to the Conn Dam Stability Assessment, Spillway Improvements, and Feasibility Alternatives Study being procured by the City of Napa, California. The report provides historical geological and geotechnical data on Conn Dam that will serve as foundational information for the current engineering assessment project. The 1982 report contains baseline geological characterizations and subsurface investigations that are relevant to the multi-phase consulting engagement, which includes geotechnical data collection, dam stability assessment under static and seismic conditions, and feasibility alternatives analysis. The City is pursuing this assessment to support regulatory compliance with the California Division of Safety of Dams and to advance federally authorized flood risk reduction studies through the U.S. Army Corps of Engineers, with a geotechnical data report due to DSOD by December 31, 2028.

The 1982 Geological Report provides historical context and baseline conditions necessary for the selected multidisciplinary engineering consulting firm to conduct comprehensive dam safety evaluations and develop alternatives for spillway improvements and long-term reservoir expansion feasibility. This archival geological data will inform Phase One of the project, which requires generation of an updated geotechnical data report, followed by Phase Two stability assessment and Phase Three feasibility alternatives analysis. The historical report is critical for comparing current dam conditions, deformation, and seismic vulnerability against documented baseline conditions from four decades prior, thereby enabling the consultant to assess changes over time and develop evidence-based recommendations for improvements and long-term water supply reliability enhancements.