Cara Sequino and Larry Johnson
The coastline city of Goleta, CA, is situated just west of Santa Barbara and approximately 100 miles northwest of Los Angeles. The Goleta Water District (GWD) provides treated water to more than 80,000 residents, businesses and agriculture customers spanning from the City of Santa Barbara border west to El Capitan, across 29,000 acres.
GWD’s Corona Del Mar Water Treatment Plant (WTP) was originally designed and constructed in the early 1970s. A decision was made in October 2005 to invest in improvements to the plant by making a number of treatment process modifications, including construction of a new 9,100-square-foot Laboratory, Administrative and Control (LAC) building. GWD also wanted to improve its stormwater management system, wastewater treatment system and overall operational efficiencies at the WTP. The modernization and upgrade of its WTP, completed in October 2007, cost $25 million and was one of the largest construction projects in GWD’s history.
To establish a leadership role in the community as a responsible steward of the environment, GWD recognized the need for sustainable design features for the Corona Del Mar WTP upgrades and the benefits of incorporating these procedures into the project. The District also wanted to use an alternative project delivery method and employed a design-build team led by MWH (Broomfield, CO) that recognized the importance of incorporating energy savings and sustainable design features into the project.
Post-Development Conditions
The existing stormwater management system was designed to collect surface runoff in a series of area drains and catch basins and convey stormwater to a natural creek bed located several hundred feet to the south of the plant property. As part of the new LAC building’s design, MWH designed a new stormwater collection system to gather surface runoff at the plant and send it to a centralized stormwater pump station located southeast of the building.
The stormwater pump station is designed to pump the first rush of stormwater to a new package domestic wastewater treatment plant located adjacent to the stormwater pump station, capable of pumping 30 gallons per minute for one hour every 24 hours.
The domestic wastewater treatment plant is capable of treating collected stormwater and wastewater generated at the WTP to quality standards that allow the treated effluent to be used for subterraneous irrigation of up to 7,000 square feet of landscaped area at the WTP.
In addition to the stormwater treatment and reuse system, GWD created a 25,000 square-foot percolation pond as part of landscaping north of the LAC building, which stores surface runoff in that area for percolation into the subsurface water table.
It could be expected that the surface runoff of the postdeveloped site would be greater than pre-development surface runoff. However, between the stormwater treatment and reuse system and percolation pond, there is actually a net reduction of surface runoff for a 1.5 year, 24-hour peak discharge storm event between the pre- and post-development conditions.
Enhancing the Stormwater Management System
During a typical storm, surface runoff flow gradually builds up to a peak then gradually drops off after the rainstorm has passed through the site.
Pollutant concentrations in stormwater runoff are typically higher during the initial flows of a storm. Pollutants build up on impervious and pervious surfaces including building roofs, concrete sidewalks and patios, and asphalt roads and parking areas during dry periods and are carried away during the first flows of a storm event. Principal contaminants in stormwater include metals, organic chemicals such as oil and gasoline, pathogens, nutrients such as nitrogen and phosphorus, biochemical oxygen demand (BOD) items such as grass clippings and fallen leaves, sediment such as sand, soil and silt, and salts such as sodium chloride and calcium chloride.
The stormwater management system implemented at the Corona Del Mar upgrade project reduces the amount of pollutants, including total phosphorus and total suspended solids, that would normally find their way to the local creek bed under the pre-development conditions. With the new stormwater collection, pump and treatment system, most of the pollutants are captured and removed before the water is used for subsurface irrigation on site. In fact, nearly all of the total phosphorus and total suspended solids will be removed from the stormwater prior to its leaving the site, reducing demand for potable water by more than 50 percent.
LEED Certification
To demonstrate the WTP’s sustainable features, Leadership in Energy and Environmental Design (LEED) v2.1 criteria certification was sought in six categories, including sustainable sites, water efficiency, energy and atmosphere, materials and resources, indoor environmental quality, and innovation and design process.
Sustainable Sites: Under the category of Sustainable Sites, the Corona Del Mar Plant provides erosion control measures that reduce site disturbance and help to control runoff. Stormwater management techniques also help treat the water onsite before filtering it back into the groundwater table. With the WTP being located close to a major urban area, issued related to the heat island effect caused by urban-rural temperature differences were minimized by the use of highly reflective roof materials and light-colored pavings.
Water Efficiency: No potable water is used for irrigation, and wastewater is treated to tertiary standards on site at the Corona Del Mar WTP. New treatment process enhancements at the WTP, including a new sedimentation basin configuration and a more efficient sludge collection system, save 8.2 million gallons of water per month. The use of low flow lavatories and dual-flush water closets, along with interior motion sensors and waterless urinals, reduce potable water use by 44% over conventional fixtures.
Energy and Atmosphere: New process enhancements such as the pumped diffusion flash mix, hydraulic flocculation, sludge collection and filter-to-waste systems are saving the GWD approximately $3,300 per month in energy costs. The Energy and Atmosphere credits for Corona Del Mar WTP apply to the building’s overall energy systems improvements and increased energy performance of 33%, which equates to $15,000 of incentives for the Goleta Water District. The District is also striving to purchase Green Power, which will reduce ozone depleting factors caused by conventional power generating facilities.
Materials and Resources: Materials and Resources efforts were recognized by the use of highly recycled content and rapidly renewable materials. For example, nearly 100% of the existing 30-year-old redwood in the treatment plant’s flocculation basins was reused as part of the plant upgrade, and over 25% of construction materials used for construction of the LAC building contained post-consumer and post-industrial recycled content. Bamboo, a rapidly renewable natural resource, was used for doors and cabinetry throughout the LAC building. Storage areas were conveniently located to make it easier for building occupants to participate in recycling programs and for collection access. Construction waste management was monitored and achieved due to the contractor’s willingness to participate and help the design team follow through with many LEED items. Approximately 75% of construction waste was diverted from landfills and recycled. This is a direct benefit of the design-build process and sustainable activities demonstrated by the District, MWH and its subcontractors. Local and regional materials were specified during design to minimize transportation and environmental impacts during delivery.
Indoor Environmental Quality: Low emitting materials were designed to reduce VOC levels in the air and eliminate toxins during installation. Carbon dioxide monitors installed in the building notify the building operator if the indoor air quality reaches a concerning level or if there is a dramatic change. The District prohibits smoking within the building and within 25 feet of building entries, operable windows and outdoor air intakes. Occupants have individual controls to adjust lighting in their respective work areas. High performance glazing, large windows, and strategically placed solar light tubes allow daylight to penetrate each space within the building. Sun shades and architectural projections line the perimeter as an aesthetic feature that also controls occupants’ comfort and reduces heating and cooling loads.
Innovation in Design: Innovation in Design credits for Corona Del Mar include an increased use of recycled materials content as well as a reduction in overall water use by more than 40%.
The “green” aspects behind the Corona Del Mar Water Treatment Plant upgrade project were implemented and tracked with great detail, with an outside consultant dedicated to the administration of LEED requirements and working closely with the MWH design team to coordinate the LEED criteria.
In support of continuing Sustainable Site Credits, the stormwater management system improvements implemented during the Corona Del Mar Water Treatment Plant upgrade project have resulted in a net reduction of 8 gallons per minute of surface runoff and a reduction of stormwater pollutants into the neighboring creek when comparing pre- and post-development conditions. In addition, the stormwater management system complies with the Best Management Practices outlined in Chapter 4, Part 2 (Urban Runoff) of the U.S. Environmental Protection Agency’s (EPA) guidelines for removal of 80% of the average annual post-development total suspended solids and 40% of the average annual post-development total phosphorous. uwm
About the Authors:
Cara Sequino is an Associate Architect and the Deputy Sustainable Design Manager for the MWH Design Group. She has a bachelor’s degree in architecture from the University of Miami, FL, and a masters of science in real estate and construction management from the University of Denver. She is also a LEED Accredited Professional and has over 2 years experience with MWH. Sequino is based in MWH’s Denver office.
Larry Johnson is a Vice President for MWH Constructors Inc. He has a bachelor of science degree in civil and environmental engineering from Clarkson University in Potsdam, NY. Johnson has over 28 years of design and construction experience in the field of water, wastewater, dams and hydropower. He is a registered professional engineer in the state of California and has worked for MWH for 23 years. Johnson is based in Walnut Creek, CA.
