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THE CONSTRUCTION WEEKLY June 15, 2009 䡵 enr.com Engineering News-Record WATER WORKS New York City tucks massive 290-mgd water filtration plant under Bronx golf course 1-26450083.indd 1 7/1/09 1:28:02 PM Cover Story Drinking Water 䊳 By Jack Buehrer Digging In To Deliver U nder an extremely tight deadline mandated by the U.S. Environmental Protection Agency, New York City is building its first-ever water filtration plant, which, once operational in 2012, will end a long, costly and often controversial saga that began nearly two decades ago. Originally estimated at $992 million, the now $2.8-billion Croton Water Filtration Plant entailed more than 10 years of planning before contractors broke ground in early 2007. But unlike the breakneck, 51-month construction schedule, the idea for the 290-million-gallon-per-day plant has been slowly gestating in 2 䡲 ENR 1-26450083.indd 2 䡲 New York since 1989, the year EPA began requiring filtration for all surface drinking water. “They talked about it for years,” says Bernard Daly, who is managing the project for the New York City Dept. of Environmental Protection. “Now we’re being very aggressive. It’s the driving part of the project.” Enacted in 1989, the Surface Water Treatment Rule requires all public surface water systems to achieve 99.9% removal June 15, 2009 enr.com 7/1/09 1:28:03 PM NYC takes $2.8-billion drinking water filtration plant 100 ft below grade r Clean Water of bacteria, Giardia lamblia cysts and viruses and a maximum contaminant level of 1 nephelometric turbidity units. Like some other big cities that did not filter drinking water, New York City applied for and received a “filtration avoidance” for water that came from the Catskill/ Delaware watershed, the western region of the city’s large 19-reservoir water system. But in 1993, EPA ordered the eastern portion of the system, the Croton watershed, be filtered and disinfected because of its consistent exposure to stormwater runoff and pollution. Construction of what now is estimated to be a $2.8 billion project—spread over 10 separate contracts—is expected to bring the Croton system up to EPA standards while supplying about 10% of the city’s drinking water under normal conditions and more than 30% during drought conditions. In all, the plant will have the capacity to treat 290 million gallons of water per day. Located about 15 miles northeast of midtown Manhattan, the plant is being built between 80 ft and 100 ft underground across a 9-acre footprint at a golf course, located in the southeastern corner of Van Cortlandt Park in the Bronx. Raw water conveyed through the New Croton Aqueduct in Westchester County will enter the plant via gravity through an 865-ft, 12-ft-dia tunnel constructed as part of three-tunnel contract, which created one intake and two outflow lines by boring and blasting through more than a mile of hard rock. 䊴 Layers. Once crews have a section of the foundation set, they go vertical, resulting in a tiered site that is at base slab in some areas and roof level in others. WATER CONVEYANCE ROUTE N.Y. N.J. Jerome Park Reservoir Van Cortlandt Park Plant site Ma nha ttan Bronx Queens Brooklyn 1-26450083.indd 3 Conn. PHOTO BY THE NEW YORK DAILY NEWS/HOWARD SIMMONS; MAP BY NANCY SOULLIARD FOR ENR New Croto n Aqueduc t Croton watershed 7/1/09 1:28:04 PM FILTRATION PROCESS Screw compressor Raw water passes through dissolved-air-floatation filters and Saturators receives standard UV treatment before being released into the city’s water system at Jerome Park Reservoir. DAF recycle Rawwater pump station Overflow Flocculators Weir Stage 1 Stage 2 DAF filters Troughs Raw water from New Croton Aqueduct DAF recycle pumps High level (pumped) Backwash tanks Mixer 1 Mixer 2 Media Mixer 3 UV Sleeve valves Filter to waste Air scour Waste backwash storage Backwash pump Floated solids buffer tanks Mixed-solids storage tank Low level (gravity) Treated-water pump station Force main to Hunts Point WPCP Waste backwash recycle pumps Residuals transfer pumps SOURCE: NEW YORK CITY DEP added at each train’s final water weir— including hydrofluosilicic acid to prevent tooth decay and sodium hydroxide for additional pH adjustment—treated water will be discharged through two 108-in.dia outflow tunnels, leading to the Jerome Park reservoir for distribution. The Metcalf and Eddy/Hazen & Sawyer team designed a beefed-up, castin-place reinforced-concrete structure that was required to be flexible enough to be folded into a relatively small site and strong enough to support three 9-acre levels while also holding the earth load above the plant. The design was created by converting 2D drawings into a 3D model, which was used primarily for clash detection and resolution. In 1997, the federal government sued the city for failing to meet deadlines set forth in the 1993 EPA ruling. The city was originally given a 2006 deadline to complete the plant as part of a federal court consent decree that also required it to pay a $1-million fine. The project was slowed even more by lawsuits disputing the plant’s location, chosen because of its proximity to existing lines that send water south to Manhattan and Queens. Procurement Snags As recently as February 2007, DEP was being fined $30,000 a day by the 䊱 Invisible. Once complete, the plant will be covered by about 10 ft of fill and sodded over to create a “living roof,” and driving range. federal government for not having hired a lead contractor to begin work. The original low bidder, a consortium led by Perini Corp., pulled out in spring 2007. By the time Skanska Northeast, in joint venture with Queens-based Tully Construction Co. Inc., signed the $1.3-billion base contract in August 2007, Schiavone Construction, Seacaucus, N.J., had already completed its $126-million site-preparations contract. enr.com June 15, 2009 1-26450083.indd 4 䡲 ENR 䡲 RENDERINGS COURTESY OF GRIMSHAW ARCHITECTS When complete, the plant will be covered with fill and replanted for use as a driving range. The 400,000-sq-ft plant, designed under a $50-million contract by a joint venture of Metcalf and Eddy (now AECOM) and Hazen & Sawyer, both New York City, is divided into two identical but independent parallel treatment trains, each able to treat at least 50% of the plant’s capacity. Raw water will be boosted by four 55,400-gallonper-minute vertical turbine pumps, which will propel it into three mixers that add coagulants and polymers to help remove solid particles. Sulfuric acid also is to be added for pH correction and sodium hypochlorite for disinfection. Water will then move to 48 dissolvedair floatation tanks, 24 in each treatment train. The 22-ft-x-36-ft open-top concrete structures are stacked to reduce the size of the plant’s footprint. Flocculators force any coagulated solid particles to float to the top to be skimmed off before flow is sent through the filter. “Stacking allowed us to effectively treat the water as well as maximize the space we had,” Daly says. Filtered water will pass through a sand-and-charcoal media on its way to 20 ultraviolet treatment units for disinfection. After a final mixture of chemicals is 4 7/1/09 1:28:05 PM Cover Story Drinking Water 䊳 䊴 DEP would not provide specific information on cost increases. A spokesman says they are tied to “general inflation in the construction industry and the highly competitive labor market in New York City. Cost increases are consistent with similar increases on many other heavy construction projects nationally.” To excavate the site to 80-ft to 100ft depths, Schiavone removed 186,000 cu yd of soil and 920,000 cu yd of rock, constructing concrete secant wall where the rock was high as well as soldier piles in the deeper reaches. “We came in and things were already behind, and we were able to get going right away because the site was ready,” says John Crecco, project executive for Skanska. “It’s rare that we come across a project like this where the excavation is done for us. We started at bedrock, and we were able to hit the ground running.” In August 2007, Skanska-Tully began placing the 4.5-ft-thick reinforced concrete mat foundation using mass concrete, which uses a larger aggregate and lower cement content to better control temperatures within the structure. DEP required foundation walls between 20 ft and 40 ft high to be placed against the existing rock face, which crews were able to do using a one-face form system that incorporates a vertical A-frame design. “At heights greater than 30 ft, we used a specially designed A-frame since that height has never been done before,” says Crecco. The upper-level perimeter walls required a custom-designed, vertically braced one-face wall-form system that braces back to the buttresses, spaced at 20 ft. “It allowed for the mechanical works to proceed at the lower levels, while we constructed the upper levels of the structure,” Crecco adds. Maintaining flexibility to keep both mechanical and civil teams proceeding simultaneously has been one of the biggest challenges in fast-tracking. The sequencing of each section of the site gives a slight lag to the mechanical installation. 1-26450083.indd 5 PHOTO TOP BY THE NEW YORK DAILY NEWS/HOWARD SIMMONS; BOTTOM BY JACK BUEHRER FOR ENR Tight Fit. Crews encountered existing water lines while blasting a new raw-water tunnel that connects the filtration plant to the New Croton Aqueduct. 7/1/09 1:28:05 PM As soon as openings are created in the structure, mechanical teams begin installing equipment and closing it up. Then it’s on to the next floor. As the structure rises, “the pipes follow,” says Don Fusco, Skanska vice president of operations. “We’re moving so fast that as soon as we have a portion of the foundation set, we go vertical in that area,” he adds. “It’s an extremely layered site. We have the roof poured in some areas, and the baseslab is still being poured in others. It’s a snapshot of various stages of a project.” In addition to all mechanical work, Skanska-Tully is self-performing concrete operations, rebar and sitework. In all, the joint venture is using 95% direct labor, which has also helped keep the project moving on schedule. “This way, we didn’t have to go bid a bunch of jobs, hire a bunch of subs and manage a bunch of subs,” says Fusco. Currently the team has about 650 workers on-site. Fusco anticipates total manpower will peak around 850 “once the mechanicals really get going.” Access and site logistics have created the biggest challenges on-site. The massive 400,000-sq-ft footprint is still considered small for a project so large it requires nine cranes; the three tower cranes and six crawlers are the most cranes on any jobsite in the city, says Skanska’s Crecco. Skanska’s team early on built an access ramp into the hole for direct delivery of mechanicals and equipment. Once the ramp was removed, the only access to the site was by stairs or by hook. “When we had the ramp, we were able to get 95% of the foundation 䊴 Massive. The 400,000sq-ft footprint has room for nine cranes, more than any other New York City site. “We started at bedrock. We were able to hit the ground running” John Crecco, project executive, Skanska Northeast “We’re being very aggressive. It’s the driving part of the project.” Bernard Daly, project manager, NYC Dept. of Enironmental Protection slabs completed,” says Crecco. “With sequencing, we were able to construct about 10% of the roof level. That allowed for greater access into the structure by driving on the roof.” Tunnels A joint venture of Schiavone and John P. Picone Inc., Lawrence, N.Y., completed the 865-ft-long raw-water tunnel that connects to an existing line from the aqueduct. The 12-ft-dia tunnel was built using drill-andblast techniques, and crews were cautious to avoid disrupting water service of nearby lines. “We were clear of all the underground water lines,” says Paul Scagnelli, chief engineer and executive vice president for Schiavone. “But they’re so close we had to be extremely careful.” The Schiavone-Picone contract also included construction of the two tunnels to move treated water to the Jerome Park Reservoir, about a mile away. Contractors used a 13.6-ft-dia TBM to bore the 3,600-ft-long highservice and 4,270-ft-long low-service treated-water tunnels through “pretty hard rock all the way,” Scagnelli says. But what has been one of the most locally controversial components of the project still awaits: In the fall, crews are expected to start blasting rock at the reservoir for the shaft and meter chamber, a decision staunchly opposed by the community and local leaders. The shaft, which requires removal of about 5,800 cu yd of rock, was originally planned to be built using a raise bore. When NYCDEP decided to blast the shaft to speed up construction, community members balked, filing a lawsuit to block the change of plans. Project officials say periodic blasting is more efficient and less disruptive to the community. 䡲 Reprinted from Engineering News-Record, June 15, 2009, copyright by The McGraw-Hill Companies, Inc. with all rights reserved. This reprint implies no endorsement, either tacit or expressed, of any company, product, service or investment opportunity. #1-26450083 Reprinted by The YGS Group, 717.399.1900. For more information visit www.theYGSgroup.com/reprints. 1-26450083.indd 6 7/1/09 1:28:09 PM