With the recent completion of a new central utility plant in Sacramento, California, the facility became the largest of its kind designed to meet the Leadership in Energy and Environmental Design (LEED®) Gold certification. The 78,000-square-foot facility features cooling towers that enable the plant to operate on 90 percent less water than the 40-year-old technology it replaced. California has embraced LEED guidelines set by the U.S. Green Building Council under the state’s Green Building Initiative.

The $181 million Sacramento central plant provides chilled water for cooling and steam for heating, which is piped underground to 5.5 million square feet of state office space in 23 buildings throughout the city. “The new plant will eliminate the water discharge into the Sacramento River by utilizing cooling towers,” according to the Department of General Services’ Web site. “The project includes a thermal energy storage tank that mitigates the noise through not having to operate during sensitive times of the day. In addition, the thermal energy storage tank reduces the electrical costs by reducing the chiller electrical load during peak conditions.”

The plant’s office space, which was constructed primarily with recycled materials, draws part of its energy from solar panels. Other energy-saving technology includes solar shades for windows, automated light switches, permeable paving and high-efficiency mechanical systems for heating and cooling. A main building houses the chiller plant and cooling towers, which feed the 140-foot-tall thermal energy storage (TES) tank that was fabricated by CB&I, Inc., in San Luis Obispo, California.

The TES tank is capable of storing 4.2 million gallons of water that is chilled during off-peak energy demand times for use during the heat of the day. A Tnemec coating system specified for the TES tank featured a prime coat of Series 91-H₂O Hydro-Zinc, a two-component, moisture-cured, zinc-rich urethane, which the fabricator shop-applied to both interior and exterior steel. Interior and exterior steel also received a shop-applied coat of Series N140F Pota-Pox Plus, a polyamidoamine epoxy that offers exceptional barrier protection to steel substrates.

After tank construction, interior steel received two field-applied coats of Series V140F Pota-Pox Plus, a polyamidoamine epoxy, which conforms with California air pollution regulations limiting volatile organic compounds (VOCs) to a maximum of 250 grams per litre. Exterior steel received one touchup coat of Series V140F. “The tank exterior was then covered with a rigid board insulation that was then covered with an aluminum jacket,” explained Mitchell Scott, Business Development Manager at CB&I, Inc. “It is called the Trac-Loc™ insulation system.”

A unique architectural feature on the top of the tank was coated with Series 530 Omnithane, an aluminum pigmented moisture-cured urethane, which provided a metallic appearance. Overall, nearly 950 gallons of coatings were required for the project. The 78,000-square-foot plant has a 16,500 ton capacity, with infrastructure to grow the capacity to 19,000 tons, making it one of the largest facilities of its kind in the western U.S., according to the state’s Department of General Services. The original central plant constructed in 1962 had a capacity of 12,500 tons and was designed to discharge heated water into the Sacramento River. The old plant drew its water from supply wells that limited capacity by as much as 30 percent. In 2008, failure of a chiller in the old central plant required the Department of General Services to use portable chiller units to cool state offices.

The original plan called for renovating the existing central plant, which had a 12,500-ton-capacity chiller plant but was capable of producing only 8,000 to 9,000 tons due to supply-well limitations. After it was determined that the original plant was incapable of supporting any additional equipment, the strategy shifted to construction of a new facility at an estimated savings of 15 percent of the cost of the original renovation plan, according to the project’s design-builder, Skanska USA Buildings, Inc., based in Oakland, California.

Service disruption was also reduced as a result of the new construction. Once the new facility was complete, the heating and cooling system was tapped into the existing piping. For a short time during testing, both systems were working at once. Then the connections with the old system were capped, and the old building was stripped and demolished to make way for the tank and corporation yard as well as the new storage area that took its place.

After the new plant became operational in 2009, the old facility was demolished and the TES tank was constructed in its place. When work on the tank was completed in June, the facility became the largest central plant designed to meet the LEED Gold standard, according to the state Department of General Services.

On Jan. 1, 2011, the nation’s first mandatory Green Building Standards Code (CALGreen) is expected to take effect in California. Under this code, all new buildings constructed in California will be required to reduce water consumption by 20 percent, divert 50 percent of construction waste from landfills and install low pollutant-emitting materials. Buildings that pass state building inspections can be labeled “CALGreen compliant.”

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