By Glen Furtado, M.A.Sc., EIT and Steve Hobbs, P.Eng.
TRANSPORTATION: Horseshoe Bay Ferry TerminalEngineering
Horseshoe Bay, a quaint, picturesque community located on the North Shore of Vancouver, is home to the newly renovated Horseshoe Bay Ferry Terminal. Last fall, the B.C. Ferry Corporation, which owns t...
Horseshoe Bay, a quaint, picturesque community located on the North Shore of Vancouver, is home to the newly renovated Horseshoe Bay Ferry Terminal. Last fall, the B.C. Ferry Corporation, which owns the terminal, and the B.C. Ministry of Transportation, which owns the highway approaches, completed substantial improvements. The changes were primarily to deal with the queues of traffic waiting to embark on the ferry, as well as to ease traffic congestion within Horseshoe Bay. Prior to the improvements, queues have extended up to seven kilometres from the ferry terminal onto Route 1/99, causing safety conflicts with through traffic. The terminal handles between 3,500 and 13,000 vehicles every day.
Under the aegis of the project manager, CIC, McElhanney Consulting Services of Vancouver led the engineering design for the improvements to the roadworks. The mountainous terrain and limited right-of-way in the area constrained the range of potential solutions and required innovative designs. A freeway bridge and truck runaway lane were removed and a 450-car underground parkade was constructed as a design-build project to meet an acute shortage of parking within the community of Horseshoe Bay. The ferry terminal’s holding stalls were increased from 650 to 1,265 (by filling over the highway), and the Highway 99/Route 1 interchange was reconfigured to accommodate nine toll booths. The capital cost was $39 million.
In addition, there are a new building for foot passengers designed by PBK/Cochrane Group Architects, new amenity buildings, and an overhead pedestrian walkway. There is also a new maintenance building.
Parkade and holding stalls
An initial proposal to improve the terminal involved excavating approximately 70,000 cubic meters of rock from the adjacent mountainside. This option would not have been well received by Horseshoe Bay residents for aesthetic reasons. In addition, it was felt that the parkade itself, a multi-level structure originally intended to be built within the village of Horseshoe Bay, would have had a poor visual impact. It was therefore decided that burying the parkade was a better solution.
By constructing the parkade underground, the ferry terminal holding stall area could be positioned directly over the structure, minimizing the overall footprint required for the terminal facility. In addition, enough material was displaced for the parkade that there was no need to excavate fill from the adjacent mountainside to create the new holding area. Integrating the parkade with the holding stall expansion also minimized the adverse visual impacts associated with the project. When viewed from the outside, the buried parkade is no more obtrusive than a modern adit.
Although the implemented design minimized the amount of side hill cuts needed to accommodate the improved holding facility, the required width of the holding stalls, combined with the upslope B.C. Rail line which runs alongside the terminal, necessitated the installation of retaining walls. Numerous site constraints such as an existing slant leg rigid frame overpass, existing concrete crib wall under the overpass, and the requirement to maintain uninterrupted terminal operations, created concerns about constructability.
A wall form was needed that could be constructed from the top down in order to eliminate the need to temporarily excavate the retained soil behind the wall, as would be the case with conventional fill retention systems. A steel sheet pile wall facing, combined with pre-stressed ground anchors, was used to create an innovative wall system that could be constructed with “top down” techniques.
The steel sheet piling had many advantages for this application. Its facing allows water to weep through the panel joints, effectively reducing hydrostatic pressures behind the wall, a desirable attribute on the rainy north shore of Vancouver. The flexibility of the panel joints allowed the curvilinear design of the terminal to be easily accommodated. Concrete transitions were cast at the terminus of the walls to blend the structure smoothly with the rock cut sections.
A total of 700 square metres of steel sheet piling was installed, combined with 176, 25 mm diameter anchors. Each anchor used a working load of 225 KN.
During the tendering process, the contractor submitted a value-engineering proposal to replace the steel facing with shotcrete, but it ultimately proved to be more expensive. The completed wall system successfully blends into the backdrop of rock outcrops and treed slopes to create the impression of a natural surrounding and does not detract from the view of scenic Horseshoe Bay.
The construction increased the amount of impermeable surfaces within the terminal area, so measures were taken to limit post-development stormwater run-off to the pre-development levels. A landscaped drainage channel was incorporated into the design to assist in the bio-filtration process. The treed drainage channel helps to remove sediment and slow surface stormwater, while providing aesthetic benefits.
Since the expanded holding facility is essentially a short-term parking lot, the potential to have oil and sediment from the queued vehicles mix with stormwater run-off needed to be addressed. A proprietary oil and sediment separator system was incorporated into the drainage design, effectively mitigating the potential of foreign substances out-falling to the Bay. Flotation chambers skim off the lighter contaminates for collection by pump trucks.
The terminal is now fully integrated with the topography, environment and community, while providing the infrastructure needed to improve the facility for users.
Communications and security
Due to the length of the terminal, communication systems are extensive. Underground wiring pathways for voice, data, video, security and even audio are transmitted over 1,200 metres in buried PVC primary conduit. The conduit interconnects the toll plaza, the main terminal building and the control tower.
Flagel Lewandowski designed all systems to use the same wiring infrastructure through “integration engineering.” The wiring is comprised of copper and fibre optic media and supports a multitude of technology systems. A video surveillance system with over 60 cameras provides the “eyes” for marshalling vehicles, for security and passenger safety. Digital matrix paging, LED message boards and monitors display sailing information and announcements to assist passengers with their travel. The wiring network also supports the terminal’s crucial Local Area Network, internet access and 14 cashier stations handling credit card sales. Security includes an intrusion alarm system and proximity card access control. These are administered locally, but there are plans to permit control from B.C. Ferries’ Victoria headquarters via a Wide Area Network.
Owner/sponsor: B.C. Ferry Corporation, B.C. Ministry of Transportation
Project manager: CIC (Peter Lutzmann, P.Eng.)
Civil: McElhanney Consulting Services (Steve Hobbs, P.Eng)
Parkade: Reid Jones Christoffersen, DGBK, PCL Constructors
Geotechnical: Thurber Engineering
Building design: PBK Architects, Cochrane Group
Environmental: ECL Envirowest Consultants, Cirrus Consultants
Communications: Flagel Lewandowski, DMD & Associates, Radian Communication Services
Minor buildings: Herold Engineering, R.M.T. Contracting,
W.J. Murphy Contracting
Roadworks: Bel Contracting, GCL Contracting & Engineering, JJM Group