Excavation is nearing completion and the contractor is pouring concrete on the design-build culvert replacement project in Ryegate. DuBois & King is the Lead Design Engineer for the design-build project in Ryegate that will replace culverts that convey Manchester Brook under US Route 5 and the Washington County Railroad. The deteriorated undersized culverts contributed to flooding of US Route 5 and the backwater jeopardized the integrity of the roadway and rail embankments. The culverts are deeply buried structures (over 60 ft under the railroad embankment), with steep embankments on both sides of the roadway and rail line.
Working with the Vermont Agency of Transportation, the design-build team of DuBois & King and Engineers Construction, Inc., of Williston, Vermont, developed an alternative technical concept structure that consists of two 32-ft-wide by 16-ft-high, cast-in-place, reinforced concrete arch culverts beneath the roadway and rail line. The base technical concept would have resulted in a completely buried structure with a length of 320 ft. The alternative concept being implemented is separate culverts beneath the road and railroad with a curved structure open to daylight in the median. The new culverts are 144 ft and 128 ft in length, and will increase the hydraulic capacity by 25 times the existing capacity. The alternative concept provides for: savings in initial construction costs, better access for maintenance, greatly improved hydraulic capacity, safer conditions for future inspections, improved aquatic habitat, and improved service life.
The new culverts are being installed using an open-cut approach. Temporary sheet piles are being driven up to 70 ft deep through the rail and roadway embankments for support as excavation proceeds down to the bottom of the culvert footings. Temporary bridges were designed to maintain rail and highway traffic over the excavations. Design issues include providing a 100-year service life for the new culverts; support for temporary roadway and rail bridges; significant support of excavation measures; protection and maintenance of the brook throughout construction; and limiting settlement of footings to 1 inch or less. Construction is scheduled to be substantially complete by December 2015.
See the drone video: https://www.youtube.com/watch?v=vwi33vaR7Vs
