Southern California water quality project merits a closer look
Lawrence M. Magura, P.E., Project Manager, Black & Veatch Corporation, Lake Oswego, Oregon
Neal Shapiro, Senior Environmental Analyst, Environmental Programs Division, City of Santa Monica, California
Andrew M. Stanton, P.E., Project Manager, Black & Veatch Corporation, Los Angeles, California
There's more to the ongoing efforts to clean up Santa Monica Bay than meets the eye.
The extent of the effort to improve the quality of urban runoff flowing into Ballona Creek—the large, concrete-lined channel that carries dry- and wet-weather runoff to Santa Monica Bay from parts of the western portion of Los Angeles as well as parts of Beverly Hills, Culver City, and the neighboring city of Santa Monica—may not be readily apparent to the casual observer. But the results should soon be evident to area residents and tourists attracted to the bay and its beaches as a result of startup of the Westside Water Quality Improvement Project in September 2006.
Beneath a parking lot at Mar Vista Park in western Los Angeles, a new urban runoff treatment facility works out of sight to remove floatable trash, suspended sediment, pesticides, oil, grease, and toxic-heavy metals from highly polluted urban runoff flowing through the Sawtelle Channel stormwater conveyance system before the flow reaches Ballona Creek, a major surface collector stream that flows into Santa Monica Bay. And behind the implementation of the project lies a significant collaboration, not only between the cities of Santa Monica and Los Angeles, but also among various regulatory and funding agencies.
What lies beneath?
Owned and operated by the City of Santa Monica, the Westside Water Quality Improvement Project operates deep underground in large vaults beneath the parking lot of a heavily-used Los Angeles park. The park site was selected despite its location beyond Santa Monica's borders because it was the only feasible site within the Sawtelle drainage basin that had favorable hydraulic conditions and no conflicts with existing utilities. Because the project was constructed in a public park, and not in a heavily traveled public street or right-of-way, the contractor did not have to contend with the traffic control challenges that frequently negatively impact both cost and contractor productivity in this densely-developed part of the Los Angeles metropolitan area. Black & Veatch provided design and construction-support services for the environmentally responsible, good-neighbor facility, which treats both dry- and wet-weather runoff from eastern Santa Monica and western Los Angeles. Blois Construction served as the contractor. The nearly $2 million project was funded by a combination of grants from the state of California, with matching resources provided by Santa Monica.
The facility utilizes direct filtration, screening, and sedimentation to treat and improve the quality of runoff from the Sawtelle Channel. It treats up to 3 cfs of dry-weather flow (the normal dry-weather flow in the Sawtelle Channel) by direct filtration to remove a host of suspended and dissolved pollutants. It also treats up to 36 cfs of wet-weather (i.e., stormwater) runoff by screening and sedimentation. Upstream and downstream isolation gate valves are normally fully open so that dry- and wet-weather flows are continuously treated. However, the gates can be closed as necessary to protect the system from overload during heavy or a series of storm events.
Initial opening of the baffle box access hatch showed that a significant amount of floating trash had been collected during pilot testing of the facility—a result that boded well for future success. (Courtesy of Black & Veatch Corporation)
Urban runoff enters the treatment train at a concrete "speed bump" diversion weir installed across the floor of the Sawtelle Channel, a large (22-foot by 11-foot) box culvert that flows under the western section of the park. Diverted flow enters a 550-foot-long, 36-inch-diameter pipeline, which conveys flow to a transverse weir at the head of the treatment train. The transverse weir is set so that 0 to 3 cfs (typical dry weather flow) is directed to a large CONTECH Stormwater Solutions, Inc. StormFilter unit containing 90 cartridge filters, where direct filtration removes oil and grease, dissolved heavy metals, herbicides, and pesticides. When the proprietary blended filtration media in the cartridges reaches its absorptive capacity, the cartridges are replaced with fresh ones and the "spent" filter media is hauled to a landfill. Flows exceeding 3 cfs up to 36 cfs (the hydraulic capacity of the diversion system) are sent across the transverse weir into a Bio Clean Nutrient-Separating Baffle Box, where floatable trash, suspended sediment, oil and grease, and refuse entrained in the moving water are removed by a combination of screening and sedimentation.
The hydraulically efficient facility is both cost effective and environmentally responsible. It was designed with no moving parts (except for the isolation gate valves and access hatches), chemical additives, or electrically powered treatment systems. A small electrical panel supplies power for lights and operation of totalizing flow monitors. The system operates by gravity flow alone and was designed to utilize off-the-shelf proven urban runoff treatment systems to maximize reliability and minimize maintenance support.
The location of the facility under the parking lot of a popular public park presented its own set of design and construction challenges. Although the construction site in the parking lot was fenced off to prevent public access, the rest of the park, which plays host to a heavy schedule of soccer matches and public school water safety classes, remained in full operation during the six-month construction period. Fortunately, no accidents involving either the general public or contractor personnel were reported during construction.
Park facilities remained in full use throughout construction of the Westside project. (Courtesy of DMR Team, Culver City, California)
Project construction also had to be coordinated with an ongoing City of Los Angeles Department of Recreation and Parks improvement project (late 2004 and 2005) at Mar Vista Park. The "jewel in the crown" of the renovation project was the construction of a million-dollar artificial-surface soccer field. While Recreation and Parks officials supported the urban runoff treatment facility, they stipulated that the diversion pipeline had to be installed by the park renovation project contractor (November 2004) in order to eliminate potential conflicts between the park improvement project and Santa Monica's contractor for the urban runoff improvement project; such conflicts could have jeopardized timely completion of the soccer field.
Behind the scenes
Urban runoff recognizes no political boundaries. Because the Sawtelle Channel stormwater conveyance system was built by the U.S. Army Corps of Engineers and is owned and operated by the Los Angeles County Flood Control District, and the site selected for the treatment facility by the owner—the City of Santa Monica—is located in the City of Los Angeles, the project had more than its share of political challenges and regulatory approvals that had to be negotiated before construction began. Fortunately, all parties recognized the significant environmental advantages of the project, and all of the required regulatory approvals were obtained successfully and in a timely manner.
A unique special intergovernmental agreement (IGA) between the City of Santa Monica and the City of Los Angeles Department of Recreation and Parks was negotiated to create a legal basis for allowing the City of Santa Monica to build, operate, and maintain an urban runoff treatment facility within the city limits of Los Angeles. While the negotiations were without precedent, they moved forward with universal recognition that the completed project would make a positive contribution to improving water quality in the local watershed and beyond that in Santa Monica Bay. Much goodwill was generated in the process of drafting the IGA, which carried over to the formal ribbon-cutting ceremony in early November 2006. The ceremony was attended by officials from both cities as well as several of the state regulatory and funding agencies involved in the project.
StormFilter vault under construction (Courtesy of City of Santa Monica, California)
Around the bend
The project is a clear win-win because it not only improves the quality of runoff entering Ballona Creek and Santa Monica Bay but also sets a precedent for intergovernmental cooperation between the cities of Los Angeles and Santa Monica to achieve an environmental improvement objective. Furthermore, it paves the road for similar future projects with watershed and runoff overlap. Through intensive and positive cooperation among the project stakeholders and participants, the facility was built as conceived and according to schedule for the betterment of the greater community. Although the dedication ceremony for the Westside Water Quality Improvement Project was not held in time to impact the November 2006 general election, the citizens of Santa Monica nevertheless voted in that election to establish a new special urban runoff tax that will generate some $2 million a year in local revenue to pay for future urban runoff quality improvement projects.
Although beach and park visitors do not know or particularly care about the challenges of balancing jurisdictional needs, competing site uses, construction scheduling, and community activities over two years and two rainy seasons, the Westside Water Quality Improvement Project serves as a shining and noteworthy example of how environmental stewardship can be achieved when people work together in a spirit of sustainability.
Lawrence M. Magura, P.E., can be reached at (503) 675-3194 or firstname.lastname@example.org; Neal Shapiro can be reached at (310) 458-8223 or email@example.com; and Andrew M. Stanton, P.E., can be reached at (213) 312-3307 or firstname.lastname@example.org.