Precast Solutions

Riding the Waves

By Bridget McCrea

Development near famous Surfrider Beach in California benefits from precast concrete.

When they’re shooting tubes, hanging ten and carving up the waves, the last thing surfers want to worry about is whether the water they’re immersed in is clean. Thanks to a project involving precast concrete, the beach boys and girls hanging out at the famed Surfrider Beach in Malibu, Calif., can rest easy knowing that the water they’ve chosen to swim in is indeed safe.

That wasn’t the case until recently, however, as an inefficient wastewater management system from nearby Malibu Creek Plaza had been muddying the waters. Effluent had been entering Malibu Creek, which empties into Malibu Lagoon and is adjacent to Surfrider Beach, recalls Steve Braband, owner of Agora Hills, Calif.-based BioSolutions Inc. His company oversaw the Plaza’s waste discharge upgrade.

Clean beaches

Nine years ago the California Regional Water Quality Control Board (CRWQCB) and the City of Malibu conducted groundwater and surface water samplings at Malibu Creek Plaza and the nearby area and determined that the wastewater discharge was causing groundwater pollution and adversely impacting Malibu Creek and Malibu Lagoon.

“Surfers were complaining about getting sick and were pointing their fingers at the commercial entities and a treatment plant situated about three and a half miles upstream,” says Braband, whose firm worked with several “very stringent” waste discharge permits designed to meet present standards while warding off potential issues in the future.

Lombardo Associates Inc. of Newton, Mass., was retained to engineer a compliant wastewater management system to protect the lagoon and beach. The previous system was a conventional one consisting of grease interceptors, septic tanks and gravel drainfields, which provided insufficient nitrogen and bacteria removal.

According to Pio Lombardo, company president, the firm designed a cost-effective wastewater management system that employs a septic tank effluent pump (STEP) collection and treatment system. It consists of the Nitrex nitrogen removal technology, recirculating media pretreatment of septic tank effluent and an ozone-UV disinfection system for bacteria removal.

Integrated Water Services Inc. of Pleasanton, Calif., constructed the system, relocated the utilities and handled the dewatering aspect of the project. IWS performed all construction activities for the project, which included piping, excavation, concrete, electrical, setting tanks and other miscellaneous site work. The scope of work for construction included modifications to the collection system, installation of a new treatment system and retrofitting of the existing dispersal fields. Once the water was pumped down, it was stored, tested and treated using an on-site treatment system provided by Pure Effect Inc. of Orange, Calif.

Then it was time for precast concrete to make its grand entry. Specified by the engineer, the precast treatment tanks were used to satisfy requirements to minimize the depth of the excavation and accommodate the available space for the treatment system. The tanks were shipped in pieces and sealed in the field. Each “half” of the tank weighed more than 51,000 pounds, which required special handling and precautions that included a 300-ton crane, extended transportation trailers to accommodate the load and other safety precautions.

Because the tanks were being buried about 13 feet in the ground, the dewatering was particularly critical. Groundwater at the site averaged between 7 and 10 feet below grade, so “tank buoyancy was an issue,” says Peter Balas, COO at IWS. “With relatively shallow groundwater, we had to spend time dewatering, stabilizing the soil and shoring.”

Double duty

The large, heavy precast tanks – whose walls served as a shoring mechanism – also had to be joined together with epoxy. Balas says an alternate material like fiberglass would have added time and expense to the project, due mainly to the groundwater and buoyancy issues. “Given the groundwater and soil stability issues,” he adds, “precast was perfect for this application.”

The precast tanks were manufactured by Jensen Precast in Fontana, Calif. Jensen, which has worked with Lombardo Associates on past projects, got involved after the engineer inquired about the possibility of making “large one-piece tanks.” After pondering the options, the precaster came up with a special design based on a casting typically used for fuel tanks. “We modified it for the wastewater application,” says Alistair Mueller, a sales engineer with Jensen.

Overcoming hurdles

From the manufacturer’s perspective, Mueller says the tight deadline and several in-process changes to the design made the project challenging. “We had to react to those changes and put the actual manufacturing on hold until they could be incorporated into the final product,” says Mueller. The size and weight of the 20-plus 3,000- to 16,000-gallon tanks made transporting them a challenge. The precast manufacturer used 100-foot-long tractor trailers to get the massive structures to the job site.

Lombardo says precast concrete was selected due partly to his firm’s past experience using the material in underground projects. “We looked at fiberglass, polyethylene and other options, but with the high groundwater and concerns about anti-flotation, we opted for precast concrete,” says Lombardo, who adds that tank shape also came into play during the selection process.

“The treatment processes themselves really require that the tanks be rectangular, not cylindrical. Precast is the only way to go with that,” says Lombardo, who during the initial research phase found the cost differences between precast and other options to be “extremely minimal.”

Braband concurs with Lombardi, and says the fact that precast tanks could be built in a monolithic fashion made them particularly attractive for this application. “There was the potential for earth movement,” he explains, “which is why we had to come up with these custom, monolithic concrete tanks.”

More precast, please

The Malibu Creek Plaza Wastewater Treatment System has been operational since July 2007 and has paved the way for Malibu Creek Plaza, a thriving shopping plaza comprising retail and commercial businesses. Located on the Pacific Coast Highway about 10 miles north of Santa Monica, the facility includes three full-service restaurants, a movie theater and a variety of retail shops.

The project was finished ahead of schedule and took just six months from initiation to startup. Despite the numerous changes in scope that occurred during the project, IWS maintained the projected schedule. “IWS really worked well with the owner and the tenants to minimize the impact to their ongoing retail business while getting the project completed on schedule,” says Cindy McAfee, Malibu Creek’s property manager. “They had the resources and expertise to complete this complex project on schedule and maintained great communication with all the stakeholders to make for a very smooth project.”

Mueller expects the successful project to open more doors for precast concrete manufacturers who can develop custom solutions to issues once solved by alternative materials – and not always successfully. “In speaking to Lombardo Associates,” says Mueller, “I believe there is future potential for more of these applications.”

Lombardo says the project owners are particularly impressed with the success, and notes that the system has been “working beyond expectations, which were very high.”

“With all due humility, the regulatory community considers this an advancement in the state of the art; we’ve set the bar higher for what can be done,” says Lombardo. “Some of the attractions of the technology is that it’s very low-maintenance and monitored electronically, so we see what’s going on all the time. The operator only has to be there once a month.”

Braband says the project has become the “showcase of the area,” and notes that his firm is fielding inquiries from companies seeking on-site tours of this state-of-the-art system. “It’s open for business with no odors and no leakage,” says Braband. “Within eight weeks we were meeting our discharge requirements, and it has been running smoothly ever since.”

Project Details

Malibu Creek Plaza, Malibu, Calif.

Description: A shopping plaza located in an environmentally sensitive area near Surfrider Beach.

Owner: Malibu Creek Preservation Co.

Engineer: Lombardo Associates Inc., Newton, Mass.

Contractors: BioSolutions, Agora Hills, Calif.; and Integrated Water Services Inc., Pleasanton, Calif.

Precaster: Jensen Precast, Fontana, Calif.