Camp Blanding digs in with 65 miles of all new lines.
Over time Camp Blanding did its best to maintain the original ductile iron water and clay sewer lines, but the systems took a toll in maintenance dollars. According to Jim Wood, P.E., chief engineer with Pittman, Hartenstein & Associates (Jacksonville, Florida), the Blanding sewer system was so bad that during normal operation the treatment facility, processed mostly groundwater. When it rained, 400,000 to 500,000 gallons of water infiltrated the system and was processed at the treatment plant; in reality the system was only processing 100,000 gallons of actual sewage.
Blanding engineers wanted a low-maintenance, leak-tight system that would be easily added onto and adapted with readily available fittings. The consulting engineer specified two different piping materials with similar flow characteristics and good performance histories: AWWA C 900 PVC and AWWA C 906 HDPE. The project was bid lump sum, regardless of the material.
The PVC pipe uses a gasketed joint; HDPE pipe uses a heat-fused joint. Blanding officials had no experience with HDPE, but the consultant had worked with the material. HDPE meets AWWA standards and is available in ductile iron sizes for compatibility with existing system components.
W.R. Townsend Contracting, based in Jacksonville, Florida, won the $5-million project. The contractor opted lot HDPE pipe manufactured by Plexco, a division of Chevron Chemical Company (Bensenville, Illinois). Dan Reed, project manager for Townsend, explains, "We looked at both materials and decided the Blanding project would be an ideal application for the HDPE pipe."
The manufacturer permanently color codes HDPE pipe for instant identification. Bluestripe pipe was used exclusively for water distribution. The contractor installed 63,000 ft of 12-in.; 158,000 ft of 6-in.; 4,200 ft of 8-in.; and 36,000 ft of 4-in. and smaller pipe. Additionally 18,000 ft of Greenstripe HDPE was used for sewer force mains connecting the pump stations to the treatment plant.
In terms of time, Reed points out that when there are no underground conflicts, HDPE can be installed as fast as the ditch can be dug. On most days, Reed's team installed up to 1,500 ft of pipe. To maintain the pace, hundreds, sometimes thousands of feet of pipe were fused together in lengths in advance of installation. Heat fusion creates a leak-tight joint that is as strong as the pipe itself. Often two fusing crews were on the job for each installation crew.
Reed observes that in turns and curves the flexibility of the HDPE pipe was particularly helpful, often providing a cost saving by eliminating the need for 45- and 90-degree bends. He figures his crews fused the HDPE pipe and fittings about 6,000 times.
Mechanical fittings were used to connect HDPE to other system piping. Each fitting was restrained with a uni-flange. Service connections were made with end-connections and double-strap saddles.
Reed notes HDPE is elastic and testing procedures vary from other pipes. "When HDPE is initially pressurized it stretches and relaxes. The testing methods take that expansion and contraction into account. Once you have pressurized a few lines you quickly get a feel for the process."
All lines underwent hydrostatic testing at 150 lb for two hours with the consultant witnessing the procedure. During testing of miles of pipe, only one fusion failed. The section was dug up and the fusion examined. It had not been fused properly. It was repaired, and the line accepted. Reed says during the fusion process it is easy to see if a joint has been fused properly. "A bead is created during fusion; if the joint is visually inspected, you can catch a problem before the pipe is buried."
Blanding's battle to maintain its old water and sewer systems is over. The new-systems became operational in March 1998. Given the scope of the project, the contractor and consultant agree that ease of installation and reliability of the pipe used made it ideal for Blanding.
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|Title Annotation:||Orange Park, Florida|
|Date:||Feb 1, 1999|
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