Precast Solutions - March/April 2008 - (Page 10)

Malibu Creek Plaza Title 22 Unrestricted Effluent Standards Resue Requirements Constituent BOD5 Total Suspended Solids Turbidity Oil & Grease TDS Sulfate Chloride Total Nitrogen Fecal Coliform (a) Enterococcus (b) Total Coliform Units mg/l mg/l NTU mg/l mg/l mg/l mg/l mg/l MPN/100ml MPN/100ml MPN/100ml 24 Average 30 30 10.0 Max 45 45 15.0 15 2,000 500 500 10 200 104 2.2 23 2.0 10.0 Average Max Treatment Plant Average Effluent <8 <6 1.3 <5 569 65 195 4.04 <2 <1 <4 OVERCOMING HURDLES From the manufacturer’s perspective, Muller 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 Muller. The size and weight of the 20plus 3,000- to 16,000-gallon tanks made transporting them a challenge. The precast manufacturer used 100foot-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 the available space for the treatment system. The tanks The chart shows the expected effluent values by the state of California and, in the far right column, the actual values after the new system became operational. 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.” 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 Lombardo, 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 DOUBLE DUTY explains, “which is why we had to come up with these custom, monolithic concrete tanks.” The large, heavy precast tanks – whose walls served as a partial 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 Muller, a sales engineer with Jensen. 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 businesses 10 PRECAST SOLUTIONS | MARCH/APRIL 2008

Table of Contents Feed for the Digital Edition of Precast Solutions - March/April 2008

Precast Solutions - March/April 2008 Contents Smooth Move Riding the Waves Comparing RCP With Plastic Pipe Cost-Value Analysis of Storm Sewer Pipe Concrete Testing On a Grand Scale Building Confidence

Precast Solutions - March/April 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.