A new water filtration plant under construction in The Bronx is the centerpiece of the largest single construction project in the history of New York City.
The filtration plant is designed to ensure that water from the Croton System watershed is aesthetically pleasing and meets or exceeds all drinking water quality standards. When completed in 2012, the plant will provide roughly 10 percent of New York City’s 1.4 billion gallon average daily demand for water. During drought or other conditions affecting other watersheds servicing New York, the new plant can deliver up to 30 percent of in-City water needs.
To achieve a design capacity of 320 million gallons (1.2 million cubic meters) per day, each link in the filtration process chain has been engineered for the optimum in reliability and performance. That is why An-Cor Industrial Plastics made 38 fiberglass-reinforced polymer (FRP) composite tanks for the filtration plant to standards set by the American Society of Mechanical Engineers (ASME) and the Fiberglass Reinforced Plastics Institute (FRPI).
The following table summarizes the An-Cor products, functions and dimensions:
How the tanks were made
To achieve performance requirements, An-Cor used Vipel® vinyl ester resins from AOC. The inner corrosion barriers of each vessel were made withVipel F010 bisphenol-A epoxy vinyl ester because of its excellent corrosion resistance and U.S. Food and Drug Administration (FDA) compliant properties. The barrier liners were formed using hand lay-up of the resin with veils and fiberglass mats. In addition to the standard barrier, each tank designed to hold sodium hypochlorite added a 116 mil (2.95 millimeter) thick corrosion allowance for extending the equipment life.
Structural laminates were manufactured with Vipel K022 bisphenol-A epoxy vinyl ester. The high performance resin meets project specifications for high strength, excellent chemical resistance and, with synergist addition, Class I fire-retardant properties per ASTM E84.
“The Vipel resins were selected for their ability to meet critical end-use performance specifications,” said Rob Merrill, An-Cor (Vice President-Operations). “The technical support that AOC provided with the resins was excellent. AOC Corrosion Specialist Bill Holtzclaw’s knowledge of FRP processing and quality standards was very helpful. Both Bill and AOC Product Leader Scott Lane were quick to respond when we needed to optimize processing.”
The corrosion barriers of the cylinders were made using the hand lay-up method utilizing fiberglass taped goods. Depending upon the diameter of the tank, the structural portion of the cylinders were built using mechanical applications of chop strand mat, woven roving, and/or winding glass.
The top and bottom heads of the 10- and 12 -foot (3- and 3.7-meter) tanks were resin-infused using Vipel K022EBB resin. Balsa wood cores were encapsulated into the glass fiber-reinforced laminate to achieve higher stiffness. The heads of the smaller tanks were made by hand lay-up of fiberglass and resin. All tanks were post-cured in a convection oven prior to shipment.
The tanks that An-Cor delivered to the Croton Project were backed by certification from two prestigious industry associations — the American Society of Mechanical Engineers (ASME) and the Fiberglass Reinforced Plastics Institute (FRPI). An-Cor is the first composite manufacturer to be certified by both organizations.
ASME is a not-for-profit professional organization whose mission includes the establishment and maintenance of engineering codes and standards. An-Cor is among the elite group of composite fabricators that meets certification requirements for ASME RTP-1 “Reinforced Thermoset Plastic Corrosion Resistant Equipment.”
ASME certification ensures design rules, fabrication methods, testing procedures and quality control programs are followed. Each tank was successfully hydro tested after installation at 5 psi (0.3 bar) to validate designs in accordance with the standard.
FRPI is a non-profit membership organization that audits and tests laminates of corrosion-resistant equipment on a job-by-job basis. “The versatility of FRP composites allows corrosion-resistant equipment to be custom-designed to meet specific project needs,” said Gary Arthur, Executive Director and President of FRPI.
“FRPI certification tells specifiers and buyers that the FRP equipment materials for their project meet their specification,” Arthur said. “This provides confidence that the equipment will meet objectives for quality, consistency, reliability and performance.”
In addition to meeting manufacturing standards; tanks, subassemblies and components that come into contact with chemicals stored to treat drinking water meet FRPI specifications that facilitate conformance with FDA food-grade standards.
Engineer and Construction
The project sponsor was the New York City Department of Environmental Protection, who will ultimately be responsible for running the plant. The main contractor is a Skanska/Tully Construction joint venture. Haley & Aldrich was geo-technical consultants, digital automation architecture was provided by Emerson, and a Hazen & Sawyer/Metcalf & Eddy joint venture acted as client consultant. URS provided support in construction management, cost estimating plus resident engineering, geotechnical engineering and tunneling inspection.
Case study courtesy of An-Cor.