Going Underground

Seattle utility aims for LEED certification with rainwater reuse

Seattle Public Utilities (SPU) is building a $50-million waste transfer station with 84 parking spots in the southern region of the state. The two-story, 140,500-sq-ft building is projected to be finished in July 2012 and will eventually replace the old south transfer station located across the street.

“The new facility will allow the city to maintain reliable solid waste services in an economical and environmentally sound manner,” said Henry Friedman, project manager for SPU.

SPU’s goal was to build the project to the standards of the U.S Green Building Council’s Leadership in Energy and Environmental Design (LEED) certification program and achieve LEED Gold status. The LEED rating system measures a proposal’s impact on the environment through various categories such as climate change (carbon emissions), indoor air quality, resource depletion, human health, water efficiency and habitat alteration, among others.

To achieve credit for water efficiency, SPU wanted to harvest rainwater to reuse onsite. Throughout the year, the water will be used in many ways, such as irrigation, washing the transfer station floor, as washdown water for the tipping floor, and for the wheel wash, which trucks can utilize as they leave the tipping floor. With limited available space on site, they needed to utilize an underground system.

SPU worked with URS Corp Inc. to locate a rainwater harvesting cistern to meet their needs and chose an UrbanGreen steel reinforced polyethylene (SRPE) harvesting cistern from CONTECH Construction Products Inc. for the project. The cistern utilized DuroMaxx technology and was comprised of two 84-in. diameter cistern sections, each 75 ft long. The SRPE cistern was chosen because it was available in such a large diameter and provided watertight joints welded using ElectroFusion couplers. It was also an economical solution.

The cistern features include a 12-in. rain leader for runoff collection, valve control outlets to drain the tanks for maintenance, four 36-in. access risers with integral ladders and internal pumps connected to the irrigation system. The irrigation will be used for the new landscaping around the facility, including 123 onsite trees, 32,000 sq ft of ground cover and 81,000 sq ft of grass cover. The system was installed below grade by KLB Construction and backfilled in just three days. The general contractor was M.A. Mortenson Construction.

“The installation went smoothly and we preferred to utilize the UrbanGreen SRPE product over the alternatives,” said Aiesh Ragih with KLB Construction.

Greg Kowalsky is with Contech Construction Products Inc. Kowalsky can be reached at gkowalsky@contech-cpi.com.

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