A landslide occurred on a steep slope between High Street and the Otis Falls Hydro impoundment on the Souhegan River following a prolonged period of heavy rain. High Street and one private residence were threatened by the potential for continuing slope failure. DuBois & King performed final slope stabilization design to include a sheet pile retaining wall at the top of the failure scarp and stabilization of the lower slope with rock riprap. DuBois & King provided bidding assistance to the Town. Services include FEMA Grant Application, data and field investigations, geotechnical investigations, survey, wetland mapping, consultation with sheet pile contractor, utility coordination, environmental permitting, coordination with nearby landowners and oversight agencies, preparation of easement plans, and construction phase administration.
Slope Stabilization for NRCS
Under an on-call contract with the USDA Natural Resource Conservation Service, D&K conducted geotechnical engineering and design of slope stabilization measures for four projects in central and southern Vermont. D&K’s work included field investigations, slope stability analysis, preparation of engineering plans and technical specifications and engineering assistance during construction. The work included coordination with property owners, state and federal regulatory agencies, permitting and cost estimating. Projects included:
Brattleboro, VT. 35-ft-high, 250-ft-long slope that failed during T.S Irene. The solution was a heavy stone fill slope keyed into the bottom of the river.
Jamaica, VT. 24-ft-high, 85-ft-long slope that failed during T.S Irene. Solution was a concrete block toe wall keyed into the bottom of the river with a heavy stone fill slope supporting the upper portion of the slope.
US Route 4, Mendon, VT. 20-ft-high, 70-ft-long slope that failed during T.S Irene. Solution was a heavy stone fill slope keyed into the river bottom with a concrete block head wall supporting the upper portion of the slope.
Stockbridge, VT. 35-ft-high, 80-ft-long slope that failed during T.S Irene. Solution was an open concrete block toe, pinned to bedrock to provide toe resistance and aquatic habitat, and a heavy stone fill slope to provide stability to the slope.
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.
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.
Stowe Mountain Lodge
Civil services for new 139-unit, luxury, 4-star resort building at Spruce Peak Mountain Village. The project included six levels of whole-ownership and fractional-ownership units on a five-acre site adjacent to the Spruce Peak ski area. A luxury spa was included as a key amenity. Underground parking was developed to serve the project.
Professional Services
Services included design of grading, paving, stormwater management, water and wastewater systems, and erosion prevention and sediment control systems for the site. Design of site improvements required close coordination with the Spruce Peak Master Plan requirements. Erosion control was critical on the project as it is located in a mountainous terrain in close proximity to streams. The stormwater management system included a Vortechnics chamber to provide water quality treatment and a subsurface infiltration gallery to provide retention and groundwater recharge.
Grading at the site was challenging, as the building was required to blend into the forested hillside, while providing for convenient vehicle and pedestrian accessibility, including ADA access. Clearing limits established during the permitting/approval phases of the project resulted in constraints to grading that required creative use of slope stabilization and retaining walls. Close coordination with other project team members, including the owner, landscape architect, and permitting approval agencies, was critical to developing the project successfully.