School is back in session and children have begun practicing soccer on the multipurpose field on Limerick Street in Alexandria, VA. This field is quite different than most, however: beneath it sits an 18 million gallon tank, divided into four water holding tanks for the storage of high nutrient loaded primary effluent during peak loading at Alexandria Renew Enterprises.
The turf field was part of a $145 million project by Alexandria Renew Enterprises to build new headquarters and has been given to the city under a 15-year easement. Dutchland, Inc. constructed the precast post-tensioned tank and multi-purpose field that enables Alex Renew to process 13 billion gallons of wastewater each year. The project was built by Clark Construction / Ulliman Schutte under the Construction Manager at Risk (CMAR) delivery method. Dutchland was a subcontractor to Clark/Ulliman Schutte for the tank structure.
Dutchland’s precast tank measures 415-ft long by 256-ft wide and consists of three levels with a building integrated into the tank. The main levels include a central pipe gallery buried 50-ft deep, twelve wet wells buried 47-ft deep, and the main tank structure buried 37-ft deep, with 12-ft above ground. The tank rests on 1,800 14-inch post-tensionted concrete piles that are used for both compression and tension and are attached to the base slab with strand. The tank is covered with a flat precast roof topped with granular fill and a synthetic playing surface to accommodate regulation soccer and lacrosse fields.
The tank was originally designed as a cast-in-place reinforced concrete structure. As a VE proposal, the tank was changed from a cast-in-place concrete structure to a precast post-tensioned structure. The justification for the change included net cost savings, schedule savings, and a significant reduction in construction-related impacts to the surrounding community.