Long known as a forward-thinking area, the west coast city of Palo Alto has completed approximately one half of a 300-day project that has replaced three miles of targeted cast iron water main pipe reaching the end of its useful life out of a project total of six miles to help secure the future delivery of reliable water service to its residents. The success of this initiative has propelled the city to adopt PE4710 pipe, installed as much as possible by horizontal directional drilling, for ongoing system replacements. The City is on track to replace the entire 214 mile system.
Palo Alto is considered the economic hub of Silicon Valley. Covering some 25 square miles, the city has a resident population that swells daily to 198,000 people, employed by some 7,000 businesses including Amazon, Facebook and HP along with Stanford University.
“This is a very high tech community,” explained Greg Scoby, PE, manager of water, gas, wastewater engineering for the City of Palo Alto Utilities Department. “Consequently, the city is fairly progressive and a lot of new approaches are investigated and used in the utilities department. The latest project involves replacing targeted water mains to eliminate leaks and improve the reliability of the system. Current studies indicate that PE materials will provide extended useful service levels over materials previously used for system replacements.”
The water main system currently consists of pipe made from asbestos cement, ductile iron, concrete cylinder, PVC and more than 388,000 feet of cast iron.
The city started to use HDPE pipe because it could be installed by boring instead of the open trench method. The water main replacement program is focused on converting cast iron pipe because the material corroded away over time and leaks.
The advantage of being able to directionally drill (HDD) or bore the HDPE pipe on a horizontal plane is that this method is less disruptive to surroundings, minimizes hauling associated both with excavation and paving, and can result in both lower costs for both installation and material life cycle. The HDPE pipe is also resistant to internal build-up or abrasion and provides a leak-free, fully restrained system.
“There has been a continuing increase in the number of water systems that are using HDPE pipe,” stated Tony Radoszewski, executive director of The Plastics Pipe Institute (PPI), a non-profit trade association. “This is because more and more systems are failing each and every day. The old pipes split, crack and the connections leak. This loss can be stopped, not just slowed or diminished to an acceptable level that communities feel they have to accept as a normal part of having an outdated product. A new system with fused HDPE pipe sections will not leak.”
The process to use PE pipe in Palo Alto started in the mid-1980s with its adoption by the City’s gas utility.
“Because of the age of our infrastructure, we recognized at that time that there were issues with our gas, water and waste water systems,” explained Scoby who was working on the gas system at the time. “The City Council agreed to accelerate the replacement program. The gas system was first. Then waste water, then we went to water.
“We started the increased level of replacement using trenching methods. We actively pursued leaking mains and areas reaching the end of their respective useful lives, focusing initially in the gas system.”