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Slope Stabilization for Vermont Highways

 

In the aftermath of Tropical Storm Irene, many roadways throughout the State were severely damaged due to flood waters from adjacent streams and rivers. DuBois & King was tasked with designing permanent fixes to five of these areas. They include areas along VT Route 14 in Sharon, VT Route 100B in Moretown, VT Route 100 in Granville, VT Route 125 in Hancock, and areas of VT Route 125 in Ripton. Emergency repairs were made to these areas following the storm to reopen the roadways to traffic. The current focus is to provide permanent designs to stabilize the stream embankments and provide additional protection against future storm events.

Project locations received hydrological and geomorphological reviews. Stream bank protection measures were designed for each site. Roadway drainage at project locations was analyzed and updated to meet current design standards. The Hancock location includes the installation of a new buried, 14′ x 7′ concrete box culvert to alleviate potential flooding to the roadway and an adjacent residence. All proposed designs received an environmental permitting review from the State of Vermont.

Design of new guardrail systems was included, also providing additional shoulder width in many areas to increase safety for pedestrians and bicyclists. The Sharon location included an adjustment to the vertical profile of the roadway to help alleviate a substandard geometric condition. Project locations received new pavement and signage to meet current design standards.

CCC Road Repairs

 

The Vermont Department of Forests, Parks, and Recreation engaged D&K to design repairs to a portion of a forest road, which was significantly damaged/washed out by Tropical Storm Irene. Sections of the road are steep and significant repairs and slope stabilization were necessary. Project included design of 50-ft-long retaining wall that required drilling and grouting to an existing ledge surface to provide a secure base, extensive ditching, culvert replacement sizing and design, and several culvert headwalls of varying type (concrete, dry stack, cement masonry).

Ryegate Design-Build Culvert Replacement

 

D&K is the lead engineer for the $15.2 million dollar VTrans Ryegate STP CULV (10) design-build project, which replaces a deteriorated culvert conveying the Manchester Brook under US Route 5 and the Washington County Railroad. The existing undersized culvert has contributed to flooding of US Route 5 and the backwater jeopardizes the integrity of the roadway and rail embankments. The existing culvert is a deeply buried structure (over 60 ft under the railroad embankment) with steep embankments on both sides of the roadway and rail line. Partnering with the contractor, D&K has developed a solution that provides savings in initial construction costs, safer conditions for future inspections, better access for maintenance, improved aquatic habitat, and improved service life and constructability.

The structure consists of two 32-ft-wide, cast-in-place, reinforced concrete arch culverts beneath the roadway and rail line. The culverts are 141 ft and 128 ft in length and will have a 100-year service life, eliminate flooding potential, and greatly improve aquatic organism passage. The project includes a temporary rail bridge to allow culvert excavation below, and temporary track realignment and superelevation removal to minimize lateral forces of trains on bridge throughout construction. Complex design issues include designing a culvert to meet better than a 100-year service life; design of support for temporary roadway and rail bridges; design for significant slope stability issues; protection of the brook throughout construction; and limiting settlement between footings to 1 inch or less.

Eastman East Lake Road Drainage

 

The Eastman Community Association (ECA) selected DuBois & King to assess existing conditions (including stormwater patterns, drainage infrastructure, erosion areas, roadway conditions and subsurface conditions) to evaluate stormwater quality, erosion and roadway improvements to mitigate water quality impact to Eastman Lake. Located within the sub-association of the Eastlake Condominium Association (ELCA), DuBois & King collaborated with both stakeholders on developing improvement alternatives. The engineering study discussed roadway surface, stormwater collection and stormwater treatment options enhance water quality discharging to the lake. An engineering study recommending the preferred alternative, project phasing and anticipated construction costs has been approved by the ECA and ELCA project committee. A Public Hearing is scheduled to receive public feedback that will ultimately lead to the design/development phase of the project.

Construction of the recommended improvements are scheduled to be completed Summer 2017. DuBois & King staff are providing hydraulic and hydrologic (H&H) analysis, drainage system design, geotechnical engineering, wetland delineation, survey, and permitting assistance to advance the project from study phase to design phase and though construction.

West Street Reconstruction

 

Project started with an alternatives analysis to determine the best option for reconstruction or relocation of a 1.3-mile portion of West Street, which was partially destroyed by flooding. Alternatives included closing the road permanently, reconstructing on the existing alignment, and relocating on one of three different alignments. D&K engineers proceeded to developed preliminary engineering, final design, and contract documents for the preferred alternative, which was to reconstruct the road on the existing alignment. The scope of services included field survey, development of line and grade, partial relocation of the adjacent stream, streambank stabilization, coordination with VT ANR and USACOE, design of a new precast concrete box culvert, and quantity and cost estimates. The project was considered an emergency action and was cost-shared between the Towns, the State, and FEMA. Services included:

Alternatives analysis
Hydraulic and hydrologic study
Preliminary engineering
Bridge culvert design
Topographic survey
Conceptual, preliminary, and final design
Stream relocation/stabilization
Construction observation
Permitting
Final design
Bid phase services
Contract documents

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