A large general contractor (GC) working in the City of Toronto found themselves out-of-compliance with their permit for discharging to the municipal storm sewer after a torrential rainfall in August 2018.
The open excavation site received 75 mm of rain in less than 3-hours, stopping below-grade work. The GC implemented an emergency pumping strategy. In order to keep the work area safe and dry, the accumulated water was pumped into the municipal storm-sewer system.
The discharge water entering the storm-sewer system was more turbid than usual: when analyzed, Total Suspended Solids (TSS) exceeded the municipal storm-sewer criteria. The City issued an “Order to Comply” and by-law officers increased the frequency of inspections, and conducted daily sampling of discharge quality and quantity entering the sewer.
With the increased attention from the City, the GC’s pumping activities were regularly interrupted due to discharge volume and quality compliance concerns.
The GC needed to better monitor on-site pumping activities, and demonstrate on-site permit compliance using real-time data and documenting the quality and quantity of their discharge entering the storm sewer system.
EMAC was retained to develop a customized datalogging solution. EMAC instrumented the pumping system with real-time water quality (turbidity / TSS) and flow (velocity and totalized volume) monitoring communication program.
EMAC implemented a site-specific monitoring dashboard where the GC had access to the data 24/7. High level alarms and automatic callouts were set-up ensuring the supervisors a remote and real time line of sight on on-site conditions and activities.
The GC successfully completed all below-grade works without another discharge incident. The GC’s consultant reported all EMAC’s real-time monitoring data to the City, certifying that the contractor met all environmental obligations and satisfied the Municipal Order to Comply.
The real-time monitoring program ensured the project was completed on schedule, eliminating months of potential delays and tens of thousands of dollars in unnecessary turbidity-TSS mitigation (equipment and treatment) costs.