Protecting Brownfield developments using spray applied membranes

Toronto’s new 51st Division Police Station receives a spray applied membrane, prior to pouring the concrete floor slab.

Brownfields have been defined by the United States Environmental Protection Agency as “abandoned, idled or underused industrial and commercial facilities where expansion or redevelopment is complicated by real or perceived environmental contamination”.Brownfields, and more importantly, Brownfield redevelopment, has become a growing market for Geosynthetic contractors. Membranes have been used in Brownfield developments as barriers to prevent harmful gases from entering the building; they are installed under the concrete floor slabs.

In 1998, Terrafix, after thorough research of available products, partnered itself with a leading manufacturer of spray applied membranes. To date, this partnership has grown at a steady rate, and together has assisted some of the largest companies in the US with their Brownfield projects.

Last fall, Terrafix’s spray applied membrane was installed at Toronto Police’s new 51st Division. The project consists of the restoration of the Consumers Gas building, located on the corner of Front and Parliament Streets in Toronto, that dates back to 1899. Designated as a Heritage Building, it was used for gas production, and is being transformed into a state-of-the-art police station. The challenge of this project was to maintain the exterior, while completely gutting the interior to construct new offices, holding cells, and exhibit rooms. The spray applied membrane will help prevent harmful gases from mitigating through the floor and into the building.

Terrafix’s spray applied membrane is a non-toxic, asphaltic-based, coldapplied, spray-on membrane. The product arrives on site in liquid form and is sprayed onto a heat burnished geotextile on site to produce a rubberized membrane. Using a spray applied membrane eliminates the need for mechanical fasteners such as batten bar and stainless steel clamps when attaching to penetrations or walls. Terrafix’s spray applied membrane adheres to most construction materials including PVC pipe (for plumbing and electrical penetrations) and concrete (walls, floors or columns). In addition to being used as a Brownfield membrane, the product is also commonly used in waterproofing.

In an industrial setting, coordination of trades is crucial. General contractors, engineers, owners and other subcontractors have benefited from the installation efficiency, reduction in crew size, and time saved.

As part of a stringent Quality Control Program, Terrafix installations are subject to destructive testing for thickness assurance, and smoke testing. During the smoke test, smoke is vented under the membrane. If a hole exists, or a penetration is not properly sealed, smoke will rise up, providing quick detection and location of leaking areas.

Terrafix has typically provided the smoke test after installation of the membrane only. However recent customers have requested additional smoke tests, up to the point of a test being done after the reinforcement bar is installed on top of the membrane. This additional test provides all project companies with the assurance that an impermeable membrane exists before the concrete slab is poured.

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