We installed the StormVault Retention System on a 12-hectare commercial site in Mississauga. The first month of operation gave us enough data to evaluate performance against the Ontario Water Resources Act requirements.
Peak flow attenuation matched the pre-development target within 3% across three measured storm events. The built-in oil-grit separator captured approximately 0.8 m³ of sediment and 40 litres of hydrocarbons during the initial runoff period. The HDPE liner held without leakage during a 48-hour saturation test at 2.1 metres of head pressure.
The installation crew noted that the modular precast sections aligned within 6 mm tolerance, which simplified the connection to the existing 900 mm outlet pipe. The only delay came from a late delivery of the geotextile wrap, which pushed the backfill schedule by two days.
For compliance reporting, the system's integrated sampling port allowed us to collect grab samples at the required intervals without entering the confined space. The first-month TSS removal averaged 83%, slightly below the 85% design spec but within the acceptable range for the commissioning phase. We expect the media to stabilize after the second month as the filter bed settles.
The project engineer appreciated the factory test certificates that accompanied each vault section. They reduced the on-site verification paperwork by roughly 60% compared to a cast-in-place alternative. The total installed cost came in 4% under budget, mostly due to the shorter excavation time.
I would recommend specifying the 3.6-metre diameter configuration for sites with a contributing area above 10 hectares. The 2.4-metre option works for smaller catchments but requires more frequent maintenance access for the sediment sump.