3.3 Demolition

Following Phase 1, the immediate removal of the Georgia and Dunsmuir viaducts, as well as selected trees, will occur. A Desktop Health Impact Assessment completed by Golder Associates in 2015 concluded that the demolition would have neutral impacts on air quality and noise change with proper mitigation measures in place. Planned road development was determined to reduce traffic noise in the area. However, no air quality modelling was completed for developments on site. A Comprehensive Health Impact Assessment MUST be completed for proposed projects onsite to ensure minimal impacts to the existing community.

3.3.1 Viaducts

As mentioned in previous reports, the Viaducts will require $8-10M over the next 15 years in maintenance cost alone. It would cost $50-65M to repair after a major earthquake and $80-100M to replace entirely (Removal of the Georgia and Dunsmuir Viaducts 2015). Both viaducts MUST be dismantled, and their materials SHOULD be salvaged for future works onsite where appropriate.

3.3.2 The Downtown Skateboard Plaza

Spencer Hamilton, a local professional skateboarder, believes the current skatepark is successful because it mimics the “different obstacles you’d actually see in the downtown core” of cities like Vancouver, San Francisco and Los Angeles. He wants to see the Plaza’s street-style design, which skateboarders worked with the park board to design, replicated in a replacement park. “This place is actually a true representation of what street skateboarders want, which is space, granite ledges, stairs, [and] rails,” says Hamilton (Miyagi & Gray, 2017). When demolishing the park, dismantle and salvage granite ledges and features for future park use.

Figure 56: Archival Photograph of Protesters on the Viaducts with Signs Reading ‘Freeways are not free”, “The road to hell is paved with politicians errors”, and More, 1972. (https://vancouversun.com/news/metro/this-week-in-history-1972-sees-georgia-viaduct-open) SITE GUIDELINES

3.3.3 Murrin Substation (721 Main Street)

Built in 1947, The Murrin Substation is reaching end-of-life (BC Hydro, n.d.) and SHOULD be decommissioned, demolished, and remediated for the site to move onto its next life. While the kind of remediation depends on the type of contamination in the soil and the groundwater, an assumption can be made based on the use of the site that there will likely be petroleum-based contamination and possible PCB’s. Some of the technologies listed below are suited for PCB remediation but it may be a lengthier process. Some considerations for soil remediation are as follows:

+ Excavation of the site. + In-situ chemical oxidation, ensuring to thoroughly saturate the soil with the oxidant (e.g. hydrogen peroxide). + Soil vapour extraction could be an option depending on the size of the contaminated site. This process involves venting the impacted soil from the subsurface so that the contamination is volatilized and pulled to the surface to be treated in the air. + The use of mycelium (specifically Morchella mycelium), which is a network of fungal threads) could be considered as a technique for soil remediation, specifically soils with heavy lead content (Yazhou Wang et al., 2021).

Some considerations for groundwater remediation are as follows:

+ In-situ chemical oxidation (injecting hydrogen peroxide into the groundwater). + Activated carbon treatment technology. This involves injecting an activated carbon substrate into the subsurface, which acts as a sponge to the contaminants. + Enhanced in-situ bioremediation. This process includes injecting nutrients and electron acceptors (e.g. emulsified vegetable oil or lactate) into the subsurface to promote the aerobic biodegradation of the petroleum contamination in the groundwater via the existing native bacterial population. This could include injecting more bacteria to kickstart the process.

Special thanks to Samuel Lingwood, M.Sc.A., P.Eng., Team Leader & Senior

Project Manager, Environmental Due Diligence & Remediation at Pinchin Ltd. for providing us with this information.