Helical Pile for East Humber Trail Boardwalks, Pedestrian Bridges, and Bat Boxes

The East Humber Trail, in Richmond Hill, Ontario, Canada, is a 2.9 km recreational trail made up of four (4) boardwalks, four (4) pedestrian bridges, and four (4) bat boxes. In September 2012, this nature trail opened to the public to enjoy walking, hiking, jogging and the natural landscape. The area covers several topographies such as woodlands, meadows, and wetlands, providing diverse habitats for many wildlife species, especially a wide variety of birds, which can be observed.

After making a presentation to Richmond Hill City Officials and Engineers, Techno Metal Post Hamilton-Durham (TMPHD) was contracted to install helical piers for the foundations for all the boardwalks, pedestrian bridges, and bat boxes along the entire trail. TMPHD clearly demonstrated this project could be completed in less time than other options considered and save the municipality significant money. This ultimately was the determining factor in TMPHD securing the project.

The Techno Metal Post Engineering Department reviewed the project requirements and confirmed that P2 and P5 piers with 24-inch helix, at varying depths of 5-8 feet and up to 17 feet in organic soils, would be the most effective solution for a project of this scope and application. Initially, consideration was given to using a pier with two (2) helices (10” and 12” diameters, respectively) at an average depth of 28 feet. However, it was then decided that using a single helix (20” to 24”) pier was more cost-effective, giving more than double the service area at the desired depth.

Because all installation locations for this project were in open spaces and environmentally sensitive areas, fields, wetlands, and woodlands, TMPHD needed to ensure that all on-site work had the least impact on the environment and natural habitats. With the R2D and EM1 (both of which use vegetable oil as hydraulic fluid), TMPHD was able to install all helical piers with minimal disruption to the environment, including little noise and no vibration. The flora and fauna and their habitats remained protected and undisturbed throughout the work.

Boardwalks

The various environments for the boardwalks provided different challenges: some were in water, others in wetlands, and some had many tree roots within the installation area to manage.

One of the boardwalks was built over a creek in sensitive soil. TMPHD provided two (2) temporary bridges so that the contractors could move in their heavy equipment without any negative impact on the environment.

Pedestrian Bridges

Techno Metal Post Engineering Department also proposed using two (2) piers to support two of the bridges instead of concrete bridge abutments. By using the piers and placing the bridge load directly on the installed piers, this eliminated the concrete abutments, therefore avoiding disturbance to the environment, which was home to red salamanders. This was accomplished at a fraction of the cost and time. All the required piers were installed in less than four (4) hours, significantly expediting the over-all project timeline.

Bat Boxes

TMPHD proposed using P10 piers as a base for each bat box as an alternative solution to concrete caissons. The Techno Metal Post Engineering Department validated the plan, responding with real-time solutions. The bases for each of the four (4) bat boxes were installed in minimal time, at a rate of 8 minutes per box.

Once all the boardwalks and pedestrian bridges were completed and the bat boxes installed, the city requested a change in the location of the bat boxes. Immediately upon this request, TMPHD remobilized the installation equipment, removed the P10 piers, and relocated them at minimal cost to the city and with no impact on the environment. This would not have been possible without significant effect on the project budget and the environment, had concrete sonotubes been used.

Awards

After its completion, the East Humber Trail boardwalks and pedestrian bridges won various awards, including the 2013 PRO Award for Excellence in Design, which recognized the “exceptional contribution to environmentally sensitive and sustainable design.” In 2013, the trail was also selected by the Environmental Design Research Association to be included in their “Health + Healing Places Exhibition”, stating that the trail “truly exemplified” the theme of “Healthy + Healing Places”.

Year: December 2011 to March 2012

Dealer: Derek Hofrichter and Roger Lauzon, TMP Hamilton-Durham

Client: City of Richmond Hill

Location address: Richmond Hill, Ontario

General contractor: Hawkings Contracting Services, Ltd.

Project objectives: To install helical pier foundations for boardwalks, pedestrian bridges, and pedestal bases for bat boxes, with as little disturbance to the environment and natural habitats as possible.

Specific challenges:

• Winter installation
• Installation in water, swamp areas, and around tree roots
• Working within Environmentally Sensitive Area
• Steel Structures required high precision on installation locations and careful flat plate pier cap welding to ensure easy install of structures after installations were completed.

Success/Advantages over other methods:

• Precision installation of piers
• Precise elevation of finished flat plate brackets
• Specialized track mounted equipment allowing TMPHD to access areas where other heavier excavation equipment would have sunk and damaged the terrain
• Environmentally friendly equipment and procedures, including little noise and no vibrations
• No disruption to flora and fauna

Soil type: Organic soil, Sensitive Soil, Clay

Installation time: 2 weeks

Number of people on site: 3

Materials used:

• P2 pier model (190+ units) in galvanized steel – boardwalks
• P5 pier model (4 units) in galvanized steel – pedestrian bridge
• P10 for bat boxes (4 units)

Equipment used:

• EM1 (track mounted installation machine)
• R2D (smaller installation equipment works in proximity to tree roots)

Bearing capacity:

• P2 minimum bearing capacity of 9 600 lbs
• P5 minimum bearing capacity of 35 000 lbs

Engineer’s specific requirements:

• In order to prevent frost heave, keep a minimum clearance of 6 inches between structural element (helical piers, wood structures, steel framing, any other) and ground surface.
• Special attention should be given to low areas (where water and snow accumulate, water down spouts, etc.), and areas where ground surface is sloped such that water/ice can accumulate under structural elements.

Depth of piers:

• P2 piers varying depths of 7 feet and up to 17 feet in organic soil
• P5 piers varying depth of 8-9 feet

Specific details of structure on piers: Outdoor recreational trail made up of wooden boardwalks and pedestrian bridges, and bat boxes.