Hydraulic_Design_Study_Report_Paukie.pdf

The document is a Hydraulic Design Study Report prepared by Consor Engineers, LLC for Beaufort County, South Carolina, focusing on the Paukie Island Road Culvert and Roadway Improvements project. The study addresses a failing causeway culvert crossing on Paukie Island, which serves a residential community and has been experiencing sinking and passability issues. The project involves replacing the existing two-lane roadway's culvert system, with the primary design criteria being to reduce differential head buildup across the causeway and resist scour effects. A field investigation was conducted on September 19, 2024, to collect calibration data and verify assumptions about the site's hydraulic characteristics.

The report recommends a two-barrel, 8X8 concrete box culvert system to replace the corrugated metal pipes currently in place. This solution aims to reduce flow contraction scour, decrease peak flow velocity during normal tide cycles, and minimize water surface head difference across the causeway. The proposed design includes riprap armoring around the culvert openings to mitigate scour and enhance structural integrity. The study determined that alternative options such as raising the roadway grades would be prohibitively expensive and beyond the project's scope. The hydraulic modeling used GeoHECRAS software and incorporated tidal data from NOAA stations, with the analysis considering various design scenarios including 10-year, 100-year, and 500-year storm events to ensure comprehensive performance evaluation.