History
Areas of Potential Concern
Since the early 1900s, SEFC has been a heavy industrial area (see Chapter One, “History”). Occupied by sawmills, steel fabrication and bridge works, shipbuilding, sand and gravel production, and brick and shingle manufacturing, this area has been filled with a variety of contaminants.
Waterfront before remediation. Source: City of Vancouver, 2002.
Twelve Areas of Potential Environmental Concern (APEC) were identified on the site, predominantly in the western areas occupied by galvanizing plants, shipyards and heavy steel fabrication facilities. Eighteen APECs were identified off site, mainly to the south and the east, reflecting the heavy industrial use of the area with support industries located nearby to service the primary industries.
Diagram shows locations of test excavations used to identify areas of contamination. Source: Vector Engineering, 2008.
Compliance and Capping
The Olympic Village site was divided into 11 parcels for development, plus parks and public areas. With the exception of three parcels, the lands were remediated and Certificates of Compliance were issued. However, at parcels 3, 6 and 11, residual contaminants remained: groundwater contamination at parcels 3 and 6, and soil contamination at parcel 11. The residual contamination was addressed by a risk assessment process, which showed that risk to people and the environment was within acceptable levels to the ministries of Health and Environment and therefore no further remediation was necessary.
At parcels 3 and 6, the zinc in groundwater contamination extended more than 12 metres into the bedrock. It was shown that this residual contamination does not prevent a risk to the environment, and consequently it was not necessary or practical to conduct further remediation.
Human or environmental exposure to the residual contamination in soil at parcel 11 is blocked by the concrete walls and foundation of the building, and the contamination does not therefore present a risk.
Design Parameters
140 Trucks a Day . . .
Picture 64 Olympic-sized pools of excavated material. With approximately 160,000 cubic metres of material excavated in 10 months, this was the biggest excavation in the history of Vancouver. There were 95,000 cubic metres (38 Olympic-sized pools) of contaminated site material, of which 22,350 cubic metres (almost 9 Olympic-sized pools) was hazardous waste. All of the soil had to be classified as hazardous or not and whether it met or exceeded commercial or residential standards. Anything that was not hazardous but exceeded residential standards was sent to the Vancouver landfill to be used as capping material. Residential quality material went to the Tsawwassen First Nation band landfill where the material had to meet stringent federal standards and was used as preparation filling for future development. All hazardous material went to the hazardous waste facility in Princeton, BC. At a rate of about 140 trucks per day (ten trucks per hour in a 14-hour workday), each load was tracked by licence, soil quality, tonnage and destination.
At right, jet grout walls are built to contain soils and prevent contact with the waters of False Creek. Source: Keystone Environmental, 2008.
The pace of construction necessitated that all soil be classified before excavation began. Using a 20-metre grid, sampling at every one-metre depth interval and drilling as much as 11 metres, Keystone Environmental characterized the quality of the soil for the entire site. By assessing the soil before excavation, excavated material could go straight into the truck, thereby cutting in half the amount of equipment needed. “There was no other way to do it in the short amount of time allowed for remediation,” Bill Donald concluded. The main investigation took place from July to September 2006, requiring 93 boreholes, 43 monitoring wells and over 1,400 samples.
Stormwater Treatment and Shoring Design
Water Treatment
Vector Engineering designed the sedimentation and erosion control plan for the entire Millennium Water development. This plan included a sediment pond and a variety of sediment control products (such as portable wheel washes, silt fencing, catch basin silt sacs, etc.) that mitigated the release or tracking of sediment out onto city streets and into the city storm sewer system.
During excavation, all rainwater that fell on the site had to be captured and treated for contamination – more than 88 million gallons in total. Source: Matcon, 2008.
Due to the sheer volume of water to be treated, the pond had to be supplemented with water treatment tanks that used a flocculent to settle out the total suspended solids (TSS). This wastewater treatment system was designed, built and operated by Storm Guard to deal with the TSS and also the contaminated water that was pumped out of some of the parcels during the excavation and foundation stage. Challenges at the site were significant given its historic use (heavy industry and related contaminants), its proximity to False Creek, the ambitious development footprint and timeline. Storm Guard’s discharge consistently satisfied all regulatory criteria, specifically relating to the following: heavy metal content, pH, total petroleum hydrocarbons, TSS, surfactants, organic toxicants and LC50 tests. The treatment plant ultimately treated over 88 million gallons (333,116 cubic metres) of water at flow rates of 500 gallons (just under two cubic metres) per minute. Analytical results obtained through a mobile onsite laboratory were used to ensure peak performance during changing influent water conditions (such as storm events and fluctuating contaminant loads). Results obtained on site were consistently supported by those obtained independently by the site’s environmental monitor, Keystone Environmental.
Vector also designed the dewatering plan for the entire development, which consisted of a network of pipes that conveyed the accumulated water from each parcel to the water treatment facilities. This water was first treated in the treatment tanks and then discharged into the sediment pond for further settling prior to discharge to the city sewers. Sediment loading could not be discharged if there were more than 75 ppm of suspended solids and the pH of the water was outside of the accepted range. Vector monitored the sediment control plan as a whole and ensured that all parties working in the Millennium Water site followed the plan. Keystone Environmental monitored the quality of the discharge water from the treatment facilities (sediment pond and tanks).
As part of the SEFC Plan, the City developed a wetland for Hinge Park to treat stormwater from upstream of the area (the catchment area south of the site) and from the surface runoff on the city streets within the Millennium Water site.
Jet Grout Wall
Specialized drilling using the ‘Klem drill’ to
form a jet grout wall. Source: Matcon, 2008.
With more than 1,100 jet-grouted columns installed by Geopacific Consultants, this was the biggest jet-grouting contract completed in Western Canada. Jet grouting is a soil improvement technique that involves breaking up the soil structure completely and mixing the in situ soil with water cement grout. The grout mix is jetted back into the soil, with the aid of special tools, at very high speeds (800-900 km/hr) created by high pressures (7,000 to 9,000 psi or approximately 48,000-62,000 KPa). Technical and logistical challenges, due to the variable soil conditions and the proximity of the site to a tidal body of water, were resolved. The jet grout columns, in proximity to the ocean, create a soil-cement wall with two purposes: providing an impervious water cut-off wall and supporting the streets and other public space improvements constructed adjacent to the building excavations.
Wheel Wash
Wheel-wash stations remove contaminants from all truck wheels before they leave the site. Source: Stormguard, 2008.
With a high volume of trucks entering and exiting the site daily, the potential for contaminated soil carried on their wheels to be tracked through city streets was viewed as a significant environmental issue. A 7 metre (24 foot) truck wash supplied by Wheel Wash International solved this potential problem. Units are fully self-contained requiring only city power (three phase or by means of generators) and a water supply. Water used to wash the undercarriages and wheels of exiting trucks is constantly filtered and recycled. Sensors placed ahead and beyond the mobile wheel wash function to activate and deactivate the wash cycle.
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BANNER IMAGE
Aerial photograph of SEFC leading up to construction, including all of the stormwater treatment ponds.
Source: Matcon, 2008