Franklin Pacific Construction was a key subcontractor to Goodfellow Brothers Inc for the construction of a 534’L x 124’W x 18’D underground stormwater detention vault for the City of Redmond Washington.  The detention vault was constructed beneath the parking lot of the Overlake Village Shopping Center which remained open for business during construction.  This necessitated detailed scheduling and coordination with the business activity of the shopping center so as to not interrupt any shopping activity.  The first phase of the project began in June and was required to be completed by November so that a winter shutdown could occur during the holiday shopping season.  This meant that the construction schedule was compressed and required substantial overtime in order to meet the deadline.  Franklin Pacific successfully achieved this milestone with a few weeks to spare.

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The vault consists of two detention cells and a flow splitter structure in the middle.  The detention cells were generally constructed of an 18 inch thick base slab, 24 inch thick perimeter walls, and 63,000 sq ft of precast hollowcore lid planks supported by interior column and beam lines.  As this is a water retaining structure expansion joints with water stop was required at approximately 24 feet on center in the base slab and perimeter walls.  The completed structure contains approximately 8500 cubic yards of concrete.  The cost of the detention vault structure construction was approximately $5.2 million.

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