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PollutionEngineering August 2012 : Page 18

Hawaiian Paradise Upgrades Sewers You won’t see it on your Waikiki vacation, but it’s under there keeping Hawaii beautiful. By KIMBERLY PAGGIOLI, P.E. and LIZ MOUCKA A b taining high-resolution subsurface data is essential s for creating the most rep-f esentative conceptual site model, especially at a con-m taminated site. According to the EPA’s Triad Approach, the conceptual site model is a summary of a site’s condition and should be the basis for any decisions made when it comes to investigating, character-izing and remediating a site. Therefore, it is important to ensure it is correct. America’s paradise destinations are not immune to the infrastructure fail-ures effecting cities nationwide. On March 24, 2006, a wastewater emergency in the Waikiki and Ala Wai area of Honolulu, Hawaii, resulted in the city spending $20 million implementing an emergency repair and installing a temporary bypass 7,200 feet long. A section of 42-year-old concrete pipe ruptured under Kaiolu Street about two city blocks northeast of the Beachwalk Wastewater Pump Station in Waikiki. This line serves the busiest area of these islands: Waikiki, McCully, Kapahulu, portions of Diamond Head, Makiki, the University 18 Pollution Engineering AUGUST 2012 A small access shaft allowed nearby activities to continue uninterrupted. area and Ala Moana. The cause of the failure was never officially determined, but according to engineers, a combination of several factors led to the emergency condition. Weeks of heavy rainfall during the spring of 2006 had saturated the soil – a mixture of coral, sand and silt – forcing the pump station to operate at capacity for several weeks and causing the aged concrete pipe to carry higher loads. The broken section was repaired within three days, but the event reinforced what city engineers already knew. Aware of the line’s aging condition, the city of

Hawaiian Paradise Upgrades Sewers

Kimberly PaggioliI, P.E. And Liz Moucka

You won’t see it on your Waikiki vacation, but it’s under there keeping Hawaii beautiful.<br /> <br /> A I Taining high-resolution subsurface data is essential for creating the most repesentative conceptual site model, especially at a contaminated site. According to the EPA’s Triad Approach, the conceptual site model is a summary of a site’s condition and should be the basis for any decisions made when it comes to investigating, characterizing and remediating a site. Therefore, it is important to ensure it is correct.<br /> <br /> America’s paradise destinations are not immune to the infrastructure failures effecting cities nationwide. On March 24, 2006, a wastewater emergency in the Waikiki and Ala Wai area of Honolulu, Hawaii, resulted in the city spending $20 million implementing an emergency repair and installing a temporary bypass 7,200 feet long.<br /> <br /> A section of 42-year-old concrete pipe ruptured under Kaiolu Street about two city blocks northeast of the Beachwalk Wastewater Pump Station in Waikiki. This line serves the busiest area of these islands: Waikiki, McCully, Kapahulu, portions of Diamond Head, Makiki, the University area and Ala Moana. The cause of the failure was never officially determined, but according to engineers, a combination of several factors led to the emergency condition. Weeks of heavy rainfall during the spring of 2006 had saturated the soil – a mixture of coral, sand and silt – forcing the pump station to operate at capacity for several weeks and causing the aged concrete pipe to carry higher loads.<br /> <br /> The broken section was repaired within three days, but the event reinforced what city engineers already knew. Aware of the line’s aging condition, the city of Honolulu had begun plans for an upgrade; in fact, construction for a new permanent force main was scheduled to begin in 2007 when the March 2006 rupture unexpectedly occurred. Concerned that additional ruptures could occur at any time, the city initiated a transition plan to protect the community from any spill emergencies before the new 5,800-foot upgrade line was completed.<br /> <br /> Emergency bypass<br /> <br /> Under the lead of the Honolulu City Department of Design and Construction, the engineering general consultant, R. M. Towill Corporation and sub-consultants Yogi Kwong Engineers and Kai Hawaii Inc., who had designed the upgrade, immediately jumped into action planning the Beachwalk Wastewater Emergency Bypass (BWEB). The engineers’ plan involved setting up a temporary system of above ground pipes and pumps to intercept and divert raw sewage from the Beachwalk wastewater pump station to the Ala Moana pump station during construction of the new force main.<br /> <br /> M&E Pacific Inc. served as construction manager for the emergency bypass, with Hawaiian Dredging Construction Company as the general contractor.Subcontractor Healy Tibbitts Builders Inc. placed the temporary bypass run above ground in places and sunk into the Ala Wai Canal where possible. Frank Coluccio Construction Company of Seattle began microtunneling a new 1,300-foot-long, twin 36-inch sewer line of Hobas pipe beneath Kaiolu Street and the canal.<br /> <br /> Two lines were needed to provide adequate capacity, according to Leighton Lum, vice president and design engineer with RM Towill Corp. These twin 36-inch lines had been designed as part of the new Beachwalk force main and had already been specified for this portion of the project.In consideration for a solution to the Emergency, work would begin on them immediately and they would initially be tied into the temporary bypass line.<br /> <br /> There was 2,000 lineal feet of 36-inch Centrifugal Cast Fiberglass Reinforced Polymer Mortar pipe for this twin line.With the timetable moved up by more than 12 months on this twin line, the pipe supplier easily answered the call of duty.<br /> <br /> “The contractors had a lot of site work to do in preparation before they actually needed the pipe delivered, so that gave the factory time to manufacture the 36-inch pipes and ship them via west coast ports,” said Hobas Pipe representative Bijan Khamanian. The pipe order was received in July 2006 and installation began in September 2007.<br /> <br /> The project involved reinforcing the soil under Kaiolu Street by jet grouting, and then direct jacking the 44-inch diameter steel casings that would house the 36-inch pressure pipes. The direct jacking operation emanated from a pit on the northeast side of the canal, tunneled under the 10-foot-deep canal and continued below Kaiolu Street to the Beachwalk pump station.Coluccio used an Iseki Microtunnel Boring Machine (MTBM) for the emergency project placing a 44-inch steel casing, followed by 36-inch carrier pipes.<br /> <br /> With the two parallel lines only eight feet apart, workers could use the same pit for the jacking of both lines. This was a beneficial design element for this urban installation as the pipe invert, or flow line, is at almost 40 feet deep. Geotechnical and design engineers specified the flow line at the 40-foot depth for a number of reasons.<br /> <br /> “Eventually, this would serve as a gravity line; we needed to get under the Ala Wai Canal and we wanted to tunnel in coraline deposits and coral limestone – not in the soft lagunal soils that would require a lot of ground improvement,” according to James Kwong, president of Yogi Kwong Engineers.<br /> <br /> Force main project<br /> <br /> With the emergency bypass in place, the city of Honolulu began to construct a permanent wastewater line called the Beachwalk Force Main system, estimated to cost $37 million. The new force main begins at the vault on the mountain side of the canal behind the Ala Wai Elementary School, where it ties into the twin 36-inch lines completed in 2008. It travels alongside the canal through Ala Wai Park, crossing under the canal near the Ala Wai Clubhouse, and then follows Ala Wai Boulevard before crossing back under the canal and terminating at the Diamond Head end of Ala Moana Park.<br /> <br /> For the 5,800-foot force main upgrade, 4,400 lineal feet of 72-inch nominal diameter pipe was supplied. The city of Honolulu, engineers and contractors had three types of 72-inch pipe under consideration; however, Frank Coluccio’s experience with the selected pipe prompted them to choose the material once again.Due to the required pressure rating, and the necessity to have a flush joint for jacking, the supplier manufactured a special flush joint pipe with an FWC coupling.<br /> <br /> To accomplish this custom manufactured pipe, the centrifugally cast fiberreinforced polymer mortar pipe was cast in a 78-inch nominal pipe mold. The pipe is nominally 72 inches inside diameter, and its outside diameter measures81. 5 inches.<br /> <br /> The 72-inch pressure pipes were designed for a maximum static working pressure of 18-psi, a maximum surge pressure of 18-psi (transient to 36-psi) and a maximum field test pressure of 75-psi. This required the company to manufacture a 50-psi class (PN50) pipe to meet these conditions. Pipes were factory hydrotested to two times the pressure rating or 100 psi at the factory prior to delivery.<br /> <br /> Tunneling for the 72-inch line began in November 2009. A total of five access pits for the jacking equipment were excavated in preparation for the microtunneling to be done in five sections, averaging a little less than 1,200 feet each, along the entire route. 4,400 feet of pipe were driven in four drives with the maximum load realized at the jacks of 500 tons. This was well below the pipes allowable capacity of 750 US tons. The pipe was supplied with a safety factor of 3.0, which yields an ultimate capacity of the pipe of 2,250 tons.Coluccio had purchased and planned on possibly using intermediate jacking stations on the jacking runs. Due to the low loads seen, none of the intermediate jacking stations were ever utilized.<br /> <br /> Pipe installation was completed in September 2011. As each section of the New line was completed, that portion of the surface temporary line was removed, much to the pleasure of the residents, tourists and city officials alike. Installation and joining of the pipes proceeded smoothly and without incident, according to Khamanian. Completion of the new Beachwalk Force Main is expected in late 2012. <br /> <br /> Kimberly Paggioli, P.E., is vice president of marketing and quality assurance for Hobas Pipe USA. She can be reached at (800) 856- 7473 or kpaggioli@hobaspipe.com.

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