Collaboration for Reclaimed Water Use: LOTT Clean Water Alliance and the City of Tumwater

By Nick Belmont, Lynda Banks and Judy Horning

Nestled into the base of Puget Sound, the city of Tumwater, Washington, is the southern gateway to a mega-metropolitan area including the cities of Tacoma and Seattle. Tumwater is located near the neighboring cities of Lacey and Olympia, the state capital. Combined, these three cities form a community just over 100,000 in population.

LOTT Clean Water Alliance (LOTT) is the non-profit interjurisdictional corporation that provides wastewater treatment and reclaimed water production services for the cities of Tumwater, Olympia, and Lacey in Thurston County. LOTT’s facilities include two treatment plants, three pump stations, sewer interceptor lines, and reclaimed water distribution pipes.

A recent joint project by LOTT and the city of Tumwater met a unique challenge for each agency: for the city, complete a planned park and shift to reclaimed water for golf course irrigation; and for LOTT, provide operational stability to meet increasing reclaimed water demands. The two groups decided on a collaborative approach to meet their goals and achieve cost savings and construction efficiencies through the implementation of the Deschutes Valley Park and Reclaimed Water Tank project. Gray & Osborne was hired as project engineer and Robert W. Droll served as the landscape architect.

A fundamental part of the project involved construction of a 1.0 million gallon (MG) AWWA D110 Type I prestressed concrete water storage tank and pump station. A prestressed concrete tank was chosen due to the site’s location within a high seismic area and the ability of a prestressed concrete tank to be differentially backfilled, which was a required design aspect of the Reclaimed Water Tank project. DN Tanks was contracted to perform the specialty prestressing of the tank.

Design parameters for the prestressed concrete tank included a 16-inch-thick mat slab floor to counteract soil conditions such as erosion potential and the chance of soil liquefaction during a strong seismic event. Additionally, the flat slab roof was 18 inches thick instead of the typical 9 inches, and it was designed for a 100 PSF live load and a 500 PSF dead load to accommodate the community park traffic.

The city of Tumwater and LOTT officially opened the park with a celebration to showcase the completed park. The half-acre park overlooks the golf course and features a children’s playground, jungle gym, grassy play area, benches, restrooms, parking, and public art incorporated into the roof of the tank. Reclaimed water stored in the tank underneath the park is used for irrigation for the Tumwater Valley Golf Course and the Deschutes Valley Park and as backup supply for reclaimed water uses in nearby Olympia. The tank will also allow for additional reclaimed water uses in the future.

DN Tanks is exhibiting at WEFTEC.16, Booth 7229. For more information, visit www.dntanks.com.