EXECUTIVE SUMMARY Chapter 1 – INTRODUCTION The Project Team, lead by Sperling Hansen Associates (SHA) and including its subconsultants Earth FX and CH2M Hill, were retained by the City of Vancouver to undertake a Hydrogeological Review of the Vancouver Landfill (the site). The Hydrogeological Review is required to be updated every five years under the site’s Operational Certificate. This study follows on from the most recent Hydrogeological Review conducted by Gartner Lee Limited in 2000 (GLL, 2000). Site Background: The Vancouver Landfill is located in Delta, British Columbia on 225 Ha of low lying land on the southern edge of Burns Bog. The Landfill has been operated continuously since 1966 as the primary solid waste disposal facility for the City of Vancouver, the Corporation of Delta and the western municipalities in Metro Vancouver. The remaining landfill air space capacity is 31.0 million tonnes (effective April, 2008). At a waste acceptance rate of 750,000 tonnes per year, the facility is currently projected to reach capacity around 2049. In order to minimize the leachate impact on the surrounding environment, a twin ditch leachate collection system was installed in 1978 after the landfill had been in operation for 12 years. The inner ditch collects leachate which is pumped to the Annacis Island Waste Water Treatment Plant. The outer ditch collects and conveys surface water runoff to the natural drainage system. The system relies on the inward hydraulic gradient principle. Leachate containment in the surficial aquifer is realized by maintaining the water level in the outer “clean water” ditch at a higher level than the water level in the inner “leachate” ditch, creating an inward hydraulic gradient with clean water from the outer ditch having a tendency to seep into the leachate collection ditch. This system effectively contains leachate within the established perimeter ditch system as long as water levels in the outer ditch are maintained above those in the inner ditch. Following the recommendations of the 2000 GLL study, leachate collection ditches were regraded to enhance the inward hydraulic gradient and additional upgrade works were carried out. Purpose: The focus of this hydrogeological review was directed to: 1. Review available monitoring data to ensure that the landfill continues to effectively contain leachate, taking all reasonable measures to provide the best possible containment. 2. Develop a better understanding of leachate flow through Phase 1, the first landfill phase to be developed to the full 39 m height. In particular, to gain a better understanding of the potential causes for elevated water levels and leachate breakouts. 3. Further the understanding of groundwater flow through the shallow and deep groundwater flow systems. 4. Better understand the significance of gradient reversals in the twin ditch systems, and to determine if the incidence of grade reversals has been reduced by the ditch network upgrades in 2002. City of Vancouver i SPERLING Vancouver Landfill Hydrogeological Review HANSEN PRJ07009 FINAL REPORT ASSOCIATES 5. Examine the impact of the landfill on aquatic life in the perimeter ditch system and Burns Bog. 6. Examine the causes for upward trends in a number of leachate indicator parameters in groundwater monitoring well GWD 23. 7. Evaluate the impacts of capping with a highly impervious geomembrane system on the overall moisture management within the landfill and the storm water management systems. Methodology: The objectives of the Hydrogeological Review were achieved through a comprehensive investigation that included a detailed field program, extensive data compilation and analysis, sophisticated modelling and focused reporting. The field program included a topographic survey of the ditch network to establish gradients, drilling of two Sonic boreholes in Phase 1, monitoring of water levels in existing gas wells, monitoring wells and sand point piezometers, electrical conductivity surveys, continuous monitoring of leachate and clean water in the twin ditch network, settlement monitoring on and around the Landfill and an assessment of aquatic habitat and fish inventory, conducted by CH2M Hill and a volunteer from the Burns Bog preservation society. The modelling efforts included the development of a Site FX Database that contained all historical topographic, borehole, water level and water quality data. The data was analyzed with a number of computer models including WATBUD (for water balance), HELP (for vertical leachate seepage through various cover system scenarios), Finite Element Modelling (to investigate the possible causes of elevated water levels in Phase 1), PCSWMM (to investigate the capacity of the ditch systems to contain run-off from the site during extreme precipitation events) MODFLOW groundwater flow modelling (to investigate the dynamics of groundwater flow between the landfill, shallow and deep groundwater flow systems) and settlement modelling (to forecast anticipated levels of settlement that are likely to occur with time). Chapter 2 – PHYSICAL SETTING Vancouver Landfill is located on two parcels of land in central Delta that together encompass 635 ha. The northern parcel, identified as Parcel 2 and not affected by landfilling operations, is currently in the process of being transferred to the Corporation of Delta. The rectangular landfill footprint, approximately 800 m north-south and 3 km east-west, occupies 225 Ha. The landfill has been in operation at this site since 1966. Burns Bog: The Landfill is located on the southwest edge of Burns Bog, a large raised peat bog that is a unique and important ecological feature in Delta. The Bog has been evolving over the past 5,000 years to its present dominant heathland type dominated by Sphagnum mosses and pine woodlands. The heathland originally occupied 2,200 ha in the core of the bog while the pine woodland covered 1,140 ha around the Bog’s edges. Today the bog occupies 2,700 ha. A radial groundwater flow system exists in the Bog, draining water from the centre of the Bog to discharge to the Bog edges. City of Vancouver ii SPERLING Vancouver Landfill Hydrogeological Review HANSEN PRJ07009 FINAL REPORT ASSOCIATES Burns Bog was first purchased from the Crown in 1882. In 1981 Western Delta Lands purchased 2,283 ha of Burns Bog. Their interest was subsequently sold to Delta Fraser Properties. In March 2004, the property was purchased by the Province of British Columbia, Greater Vancouver Regional District, the Corporation of Delta and the Government of Canada. The City of Vancouver currently owns a much smaller land parcel, totalling 635 Ha. In September, 2008 Vancouver City Council approved transfer of approximately 200 Ha of surplus lands to the Corporation of Delta. The Corporation of Delta also owns 148 ha that is protected as the Delta Nature Reserve. The rest of the Bog (about one-quarter) is owned by various public and private interests, including Delta School Board, Pineland Peat (160 Ha) and the Fraser Harbour Commission. Although Burns Bog has been described as the largest undeveloped parcel of urban land in Canada, anthropogenic activity, primarily peat mining, ditch and road construction and agriculture have altered an estimated 80% of the natural Bog environment The current 225 ha area occupied by Vancouver Landfill represents approximately 8% of the Burns Bog ecosystem. Peat has been extracted from the Bog since 1940. Approximately 40% of the Bog has been excavated to depths of 0.5 to 2 m. Cranberry and blueberry farms have been developed on the perimeter of the Bog. Site History: The City of Vancouver began operation of the Landfill in 1966. The twin ditch leachate collection system was added in 1978 to contain leachate produced at the site. In 1985 Vancouver Landfill was identified as a long term solid waste disposal site in the Regional Solid Waste Management Plan. In 1999 the City of Vancouver finalized an agreement with the Corporation of Delta to authorize placement of an additional 20 million tonnes of refuse as of Oct. 1st, 1997 within a vertical expansion at Vancouver Landfill and for the transfer of 230 ha of surplus lands within Parcel “D” to Delta. Since 1966 the landfill has been expanded eastward in cells approximately 300 m wide and 10 to 12 m high. In 2000, the operational method was switched to expand the landfill vertically to a maximum height of 39 m, starting with Phase 1 on the east edge of the landfill. Phase 1 was completed in 2006, with additional grading fills placed in 2008. Phase 1 will be capped with final cover in 2009. A landfill gas collection system was first added in 1990 to control odours. The system has been expanded several times since. In 2003, a major upgrade was undertaken to convey the landfill gas to the Village Farms greenhouse operation where it is used to produce electricity from four large generators owned and operated by Maxim and heat from boilers operated by Village Farms. Chapter 3 – GEOLOGICAL SETTING Regional Geological Setting: The City of Vancouver Landfill is sited within the Fraser River Delta, which is in turn located within the Fraser River Lowland. The landmass today referred to as the Fraser River Delta began to form at the end of the last Ice Age between 11,000 and 13,000 years ago when massive glaciers retreated from the Fraser Valley leaving behind a dense blanket of glacial deposits under glacial melt waters. During the glacial melt the flood plain of the Fraser River became overloaded, flooding the low-lying plains to the west and southwest in the area that is now Delta. Marine deposits of silt were laid down in shallow depressions within the flood plains. These City of Vancouver iii SPERLING Vancouver Landfill Hydrogeological Review HANSEN PRJ07009 FINAL REPORT ASSOCIATES now form the excellent confining layer at the base of the peat bog that serves as a barrier layer for the landfill. The postglacial deltaic sediments have a maximum reported thickness of 305 m.