In 2003, the city of Sacramento, Calif., approved installation of the Stormvault Mitigation System by CON/SPAN for treatment of urban runoff from new and redeveloped commercial and light industrial development sites. The mitigation system is a volume-based detention and sedimentation vault designed to treat storm water runoff to the Maximum Extent Practicable. The decision to install the system in the Rovana Circle Project resulted from the engineers’ seeking a solution for a site that called for a below-grade storm water treatment system.
The proposed commercial building, which was already under construction, along with the neighboring parking area allowed no room for a sloped excavation.
Therefore, the contractor chose to utilize shoring to create vertical excavation walls. Because the shoring was rented, the contractor wanted to minimize this time as much as possible.
Installation time was minimized by a just-in-time delivery method of the precast pieces. The shoring installation was completed on a Monday, the base slab poured on Tuesday, and setting of the units began Wednesday morning. The units were delivered Tuesday evening to expedite installation the next day.
On Wednesday morning, the six precast units were set in less than three hours morning and grouting began midday. This allowed for the majority of the watertight joint sealing to be completed the same day the units were set.
Only four hours were needed the following day to complete the installation of the internal baffles, piping and the rest of the treatment system.
The teams from CON/SPAN, BridgeTek and local precaster Jensen Precast, worked together closely to execute drawing preparation, fabrication, delivery and, ultimately, installation.
The Stormvault structure at the Rovana Circle site has a 14-ft span, an 8-ft, 8-in. rise and is 42 ft long. The system now provides storm water treatment and flow attenuation of 2,130 cu ft for the 2.9-acre site. According to the manufacturer, the system’s unique water quality capture design allows the capture of much smaller particles and a higher pollutant load than other flow-through systems.
The system can be designed for variable heights and lengths to accommodate volume and site requirements. It is also designed site-specific for any loading condition, including AASHTO, AREMA and aircraft, and provides peak flow attenuation for any flow rate.
The structural shell of the storm water treatment vault is made up of CON/SPAN precast arch units.
