Project Profile: San Antonio Water System Expansion Goes Underground Using HDD for 36″ HDPE Pipe

Creek and ravine crossings navigated with horizontal directional drilling

How do you fuse together, bore and pull a 36-inch diameter, thick-walled high-density polyethylene (HDPE) pipe string that links 45-foot sections into even longer threads? The answer is simple. Basically, the same way you do for any HDPE pipe system – face it, fuse it, bore it. That is how crews dealt with installing a new water main system in northwest San Antonio where one string of HDPE pipe alone ended up being 1,000 feet long. The project required a 20-foot entrance drop and exit rise so that pipe could be pulled under a creek. The water transmission main project here will connect the existing water mains with a recently constructed pump station and to accommodate future demands in the area. San Antonio Water System selected the contractor and method in a bid process based on best price.

“This new water main will connect the gap between the new pump station and the existing main to provide additional capacity for future growth in our city,” explained Juan G. Rodriguez, P. E., project engineer, production and transmission engineering department for San Antonio Water System (SAWS). “It goes through a very rough area that has a lot of rock and ravines – not the easiest terrain to bore through – plus we had to deal with an active creek. The HDPE pipe is tough and provides the type of deflection you need for directional drilling and has the best cost effectiveness.”

San Antonio Water System HDPE Fusion Water Main

Sections of 36-inch diameter HDPE pipe are fused together by the Gajeske crew for a new potable water line, adding to the San Antonio Water System (SAWS) which pumps an average of 180 million gallons a day to serve some 1.3 million customers with nearly 5,100 miles of distribution mains ranging from four to 60 inches.

“This was a very challenging installation, but perfect for HDPE pipe,” observed Tony Radoszewski, executive director of the Plastics Pipe Institute, Inc. (PPI), a non-profit, manufacturing-based trade association dedicated to expanding awareness about economics, performance benefits and environmental advantages of plastic pipe systems. “And it’s not a typical Horizontal Directional Drilling (HDD) HDPE pipe project because SAWS elected to use very thick walled pipe – greater than four inches in thickness – in a larger diameter size to meet its design specifications. But, even at this extreme, the HDPE pipe installs easily and delivers a highly sustainable, completely leak-free system with fused joints. And these characteristics are the norm when using HDPE pipe.”