The City of Pitt Meadows is concerned that increasing development is impacting shallow groundwater levels, resulting in the continual operation of sump pumps, the inundation of residential properties, and the potential overwhelming of stormwater infrastructure. To determine the cumulative effects of development on the groundwater levels in the city, ISL followed a phased approach.
Stage 1, a desktop hydrogeological assessment, was completed in November 2020 and used existing geotechnical data to estimate current groundwater levels in the city. The hydrogeological assessment recommended that the City move forward with Stage 2, a data collection program to further enhance the reliability of the water level map, and numerical modeling of groundwater flow.
Stage 2 began in early 2021 and included drilling, installing, and testing 12 groundwater monitoring wells. Purpose-specific groundwater data, including lithologies and temporal water levels by means of installing pressure transducers, were collected in areas identified in Stage 1 that had significant data gaps. A numerical model of groundwater flow was then constructed and calibrated, which has allowed for predictions of areas within the City that would be more susceptible to impact from development, particularly with preloading activities.
- Minimal background information on existing groundwater conditions and impacts on groundwater from developments.
- Lack of existing requirements for developers with respect to mitigating groundwater impacts.
- Phase 1 used existing geotechnical data to determine high-level groundwater conditions across the city. Groundwater monitoring well locations for Phase 2 were chosen to fill in areas with data gaps or uncertainties in the data.
- ISL conducted a cursory review of the available information regarding groundwater management from Maple Ridge, Langley, Port Coquitlam, Coquitlam, Burnaby, Richmond, and Vancouver, and determined which existing policies would likely be most relevant to the City.