Project Overview

The Village of Baldwin is replacing the existing 8th Street bridge crossing at the Baldwin River. The Village of Baldwin retained Fishbeck to design the replacement bridge in short-order to restore safe travel across the river. Fishbeck retained NTH to quickly perform geotechnical exploration and provide geotechnical recommendations for the design and construction of the bridge foundations.

The existing bridge consisted of prestressed concrete side by side box beam and steel girders constructed in 1940 with reconstruction in 1973 adding the south box beams. The total bridge length is 31 feet, 10 inches. The bridge was closed due to structural safety concerns following a flood in 2019. The bridge was designed as a single-span structure supported on new HP 12×74 steel piles in two rows (vertical and battered). NTH provided subsurface exploration services for scour analyses and pile vertical and lateral resistance design evaluations.

Project Scope

NTH performed a subsurface exploration consisting of 100-ft deep test borings. Due to the proximity of the Baldwin River soil squeeze was controlled using drilling slurry to retain an open borehole. The test boring depths were reviewed and modified in real-time to support drilling no deeper than required to provide minimum and maximum resistance primarily through pile side resistance. NTH also collected samples performed gradation analyses to support scour analyses and design of scour protection for the new foundation system. This was a critical component of the design as the spread footings for the original bridge were “washed out” during a flood event in 2019, resulting in closure of the bridge.

NTH evaluated the subsurface conditions, modeled the proposed pile foundations, and provided recommendations regarding the following:

  • Foundation bearing elevation to achieve 350 kips nominal pile driving resistance
  • Foundation bearing elevation to achieve 500 kips nominal pile driving resistance
  • Lateral pile resistance under design loads and deflection
  • Pile installation and performance confirmation
  • Seismic Site Classification
  • Pile tip protection
  • Lateral earth pressures on abutments
  • Dewatering and temporary earth support

NTH provided Fisbheck with assistance throughout the development of plans and specifications as well as through bidding for the work. Alternative pile bearing elevations were provided such that an economic analysis could be performed in support of pile length, spacing, and orientation development. The project was successfully completed on an accelerated timeframe so that the bridge can be re-opened for public use.

Client Benefit

NTH mobilized to site and completed foundation design services in short-order to facilitate a compressed design schedule. NTH’s accelerated approach facilitated preliminary and final design to get the road back open to the public.