NOWPARC is an innovative solution to a decades old environmental problem in Thunder Bay Harbour on Lake Superior. DST’s innovative design called for a simple and low cost (but conservative) clay isolation barrier along the shore, dredging and treatment of contaminated sediment, and creation of new land for improved fish habitat, local business sustainability and greening of 1 km of industrial harbourfront. The project is funded from 2 levels of government and 3 industries.

A new TMP plant and paper machine in Ontario required deep drilling through soft ground, in situ cross-hole testing, dynamic foundation analyses and design of heavy piling. The new facility was successfully commissioned with its 25,000 hp motors and 8m wide paper production at a speed of 80 km/hr..

DST provided complete geotechnical design services for this new secondary effluent treatment plant in Northern Ontario. Construction services for this 90m diameter concrete aeration basin included inclinometer monitoring of cut slopes, pore pressure monitoring for ground stability, pre-contract piling and electro-osmosis trials, and vibration monitoring during piling and blasting.

Project Background
The Kaministiquia River in the City of Thunder Bay, Canada, near Lake Superior, erodes its 30 m high banks at a rate of 0.5 m/year. Over the past 25 years, DST has developed an innovative cost effective approach to hazard management for 1.5 km of riverbank where homes and infrastructure are at risk. River erosion was stopped with a layer of rockfill at the bottom of the slope. The slope continues to flatten with periodic landslides, shallow in nature.

Cautionary Zone Approach (CZA)
As a practical alternative to conventional stabilization of the entire riverbank, a hazard management approach was developed based on observations and engineering assessment which defer the costs for decades:

• A cautionary zone (the size dependant on risk) is designated next to all facilities to be protected.
  
• When the top of the slope encroaches on the cautionary zone, action is taken for the specific area affected.

This has led to the following actions over the past 20 years:

• A few houses were purchased and demolished in 1984.
• 350 m of street and watermain were protected with a 12 m deep retaining wall at the top of the slope in 1985.
• 5 new areas at risk were recently stabilized with a new soil nail and root technology (SNART) developed by DST. This was found to be less cost with more benefits than all other available solutions.

SNART Concept
The soil nail and root technology solution involved inserting steel bars, typically 30 to 50 mm in diameter, into a slope on a 1 to 2 m grid. Soil nails can be installed from the slope by driving, rotation or vibrating. The near surface soil between the nails is stabilized with a special nail head and vegetation roots.

At this site the design criteria included a minimum safety factor of 1.5 and a life of 75 years. The 38 mm steel bars were installed to depths up to 12 m, with a sacrificial approach to addressing corrosion. Design root depths varied from 300 to 450 mm.

SNART Features

• A green engineered solution – steel bars integrated with a biotechnical facing.
• No disruption to land use at either the top or bottom of the slope.
• Minimal disruption to natural vegetation on the slope.
• No impact on rivers or streams.
• Maintenance-free for any specified design life.
• Immediate improvement is obtained.
• Applied only to areas in the most need as and when required.
• A flexible system that adapts to fit your desired budget and degree of risk by adjusting nail size, spacing and length.
• Integrates well with the Cautionary Zone Approach to management of slope hazards.
• Available as a design-build solution