Culverts

Places Mill Road Bridge Replacement

DuBois & King was retained by the Town of Alton to provide bridge study, design, permitting, bidding, and construction phase services to replace the Places Mill Road Bridge over the Sunset Lake outlet. The following deficiencies of the existing bridge resulted in a recommendation for total replacement: sufficiency rating of 49.7%, erosion of the approach roadway at the corners of the bridge, inadequate wingwalls, undermined and poor condition of existing stone masonry abutments, nonexistent approach guardrail, substandard bridge rail, one-lane traffic capacity, and low load carrying capacity of the concrete deck.

DuBois & King completed a study and made recommendations to replace the bridge with a two lane, 36-ft-long, precast concrete arch; provided permit application assistance; and prepared preliminary and final engineering plans and specifications. D&K engineers assisted the Town during the bid phase and provided construction administration and engineering services during construction.

Frog Hollow Bridge Replacement

Evaluation, design, and construction phase services for the replacement of an undersized culvert that had inadequate hydraulic capacity. The new culvert was designed to promote aquatic organism passage and sediment transport. Following a geomorphic assessment to determine natural channel dimensions, D&K identified and evaluated several alternatives. The selected option was a precast concrete, four-sided box culvert with fish baffles. Project involved altered alignment for the new culvert, new guardrail locations, and highway and grading adjustments. Services included:

Coordination and meeting with State regulators
Conducting a stream geomorphic assessment
Completing a topographic site survey
Computing peak stream flows and simulating flows with HEC-RAS
Designing a replacement culvert with fish baffles
Preparing plans and specifications
Providing bid phase and construction inspection services

Fremont Road Bridge Replacement

Planning, design, and construction services for the replacement of the Fremont Road Bridge over Towle Brook. DuBois & King engineers conducted a study and provided recommendations regarding alternatives to replace the bridge. A 14-ft clear span, precast concrete rigid frame was designated as the most cost-effective bridge type for this location. The bridge foundation consists of cast-in-place concrete strip footings bearing on ledge. In addition to design services, DuBois & King provided permit application assistance and bid and construction phase administrative services.

The pre-existing bridge had insufficient hydraulic capacity and had a history of scour damage. However, a hydraulic analysis, using a HEC-RAS model to evaluate the bridge hydraulics, showed that increasing the hydraulic opening would increase the potential for downstream flooding of several homes. DuBois & King consequently recommended a structure with an opening equivalent to the existing bridge. To prevent scour, it was recommended that the new footings be placed well below the stream channel.

Chippenhook Bridge Replacement

Project definition, NEPA, permitting, design, plan development, and construction phase services associated with the replacement of Bridge No. 25 over the Clarendon River. Bridge type and alignment study evaluated various bridge types on several different alignments. Services included ground survey, wetland delineation, preliminary roadway design, and hydraulic and structural analysis. Detailed engineering report presenting bridge type and alignment alternatives along with associated costs, environmental impacts, and advantages and disadvantages for each, along with recommendation with supportive reasoning was presented to the Selectboard and VTrans.

The Town selected a two-lane, 32 ft clear span precast concrete arch structure supported by a cast-in-place concrete slab and new wing walls. Project included approximately 500-ft of roadway improvements, including new subbase, vertical realignment, new bridge guardrails, asphalt, pavement markings, and intersection improvements. Cut granite block facing mounted to each fascia provided a finished appearance to the structure.

D&K bridge and hydraulic engineers have considerable expertise in designing durable culverts that are properly sized and that are placed to facilitate safe vehicle travel, enable aquatic organism passage, and promote wildlife and stream health. Scour and erosion protection are prime considerations when designing culverts as erosion can degrade water quality and be detrimental to aquatic organisms. D&K river experts hydrologists, and hydraulic engineers contribute to the design of culverts by considering the integrity of the up and downstream channel, other river structures, the resiliency of the channel to withstand storm events, and the ability for the culvert to pass storm-event water volume, debris, and sediment.

Services

Inspections
Subsurface Investigations
Load Ratings
Design of Rehabilitations and Replacements
Design of Abutments, Retaining Walls, and Footings
Culvert and Approach Railings
Roadway Approach Design
Hydrologic/Hydraulic Analyses
Aquatic Organism Passage
Streambank Stabilization/Protection
Right-of-Way
Permitting
Cost Estimates
Construction Documents
Bid and Construction Phase Services

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