Hydro One Facility, Orillia, Ontario
In the expert hands of EllisDon and their team of consultants, including Peto MacCallum and Morrison Hershfield and others, construction of the new 120,000+ square foot, $150 million dollar Ontario grid control centre in Orillia, Ontario, began in late 2019 and is set to be fully operational this year.
The site’s plan included a Primary Ontario Grid Control Centre, a provincial warehouse, and a regional operations centre that would operate 24/7 to provide reliable electricity across the province. It was selected by Hydro One “for improved accessibility, cost considerations, and minimal impact on employees working at the existing grid control centre in Barrie.”
GeoSolv was selected to treat the poor soil conditions for the warehouse and guardhouse portion of the project in Orillia for the foundations. The soils in the area mainly consisted mainly of loose-fill underlain by zones of very loose silt and sand. The silts on-site would certainly have created risk for future structural settlements if not properly managed.
Ultimately, the Rammed Aggregate Pier® System, utilizing the Geopier Impact® installation method was selected to be installed to support the heavily loaded raft foundation. Utilizing this ground improvement proved to be a very cost-effective and practical alternative to dig-replace. The Impact installation method allowed for the construction of Geopier elements within the saturated/caving soils and generated no excess soil for the contractor to have to manage.
Rigorous testing on-site proved the design worked for 25mm of total settlement and 19mm of differential on a site, which would have otherwise yielded much higher total and differential settlement due to the poor and variable soils present. Geopier design methodology involves a full-scale Modulus Load test on-site to demonstrate the high stiffness that results from Rammed Aggregate Pier installation. The pier stiffness is predicted from a database of over 10,000 load tests and then checked on-site with a full-scale load test. Load testing at the Orillia site yielded settlements of 10 mm at design stress and showed a very stiff response.
The Geopier system was tendered head-to-head with traditional over-excavation and replacement (engineered fill) and piling methods and was proven to provide significant cost and schedule advantages.
Additional advantages included:
- Avoiding over-excavation to reduce soil handling
- Eliminated the need for shoring/protection systems against the existing structure
- Reduced dewatering requirements by limiting excavation depths
- Improved schedule control avoided weather delays often associated with excavations
- Schedule savings realized by installing the Geopier system prior to requiring any foundation permits
- Controlled costs through lump-sum pricing, avoiding cost overruns due to unknown soil volumes