The Las Virgenes Municipal Water District (LVMWD), Calabasas, CA. provides potable water and wastewater treatment services to residents of Agoura Hills, Calabasas, Hidden Hills, Westlake Village, and surrounding areas of Los Angeles county. The facility is considered to be a model for wastewater treatment and environmental stewardship.
Recently an eight-inch ductile iron force sludge main deteriorated beyond the point of operation. LVMWD Facilities Manager David Lippman needed to find an effective, efficient and environmentally friendly pipeline replacement method. Lippman said, “The loss of this sludge line really put a strain on our operations. We needed to replace the line in a short amount of time, but, because of its location, we wanted a method that minimized social and environmental disruption.”
After reviewing method recommendations, Lippman chose static pipe bursting. J. Fletcher Creamer, California Operations, Sylmar, CA. was contracted and trenchless equipment manufacturer TT Technologies, Aurora, Ill. was contacted for technical support.
The LVMWD was formed in 1958. Today, in addition to potable water, the district also offers wastewater and water recycling services. Recycled water from the district’s Tapia wastewater facility is used to irrigate golf courses, school grounds, highway medians and other areas. A percentage of biosolids (waste removed from the wastewater) is transferred to the Rancho Las Virgenes Composting Facility four miles away. At Rancho, the biosolids go through a process that produces 20,000 cubic yards of soil amendment a year.
Two state-of-the-art fuel cells at Rancho take the methane gas by-product and use it to create energy to run the facility. This fuel cell arrangement is one of only five similar plants in the world. The district and its facilities have been recognized nationally for quality operations.
For all its advancements, the LVMWD still faces the same infrastructure problems treatment facilities around the country are facing. The recent replacement of a section of force main between the Tapia plant and the Rancho facility highlights the issue.
Lippman said, “We have two force sludge mains running from Tapia to the Rancho facility, a six-inch main used prior to the development of the composting facility and the eight-inch, PE wrapped main. In October of last year we experienced a failure in the eight-inch main. It was determined that a microbiological induced corrosion caused the failure.”
In October of 2002, a 40-foot section of the ductile iron main was replaced. In December, the pipe failed again. The 8-inch pipe was taken offline and the 6-inch main was used instead. Lippman began putting together a plan to correct the problem. After reviewing several methods, static pipe bursting was chosen and J. Fletcher Creamer and Son was contracted.
J. Fletcher Creamer and Son has a distinguished history as a multifaceted contractor. Over the last 75 years the company developed into one of the most respected contractors in the United States. With offices throughout the country, J. Fletcher Creamer has developed a reputation for dependability, progressiveness and innovation.
Both California based J. Fletcher Creamer and Son Area Manager George Mallakis and Lippman agreed that trenchless pipe bursting was a good option for this project. Mallakis said, “The location of the pipe made a trenchless option very attractive. The pipe ran along Las Virgenes road, the main artery between Highway 101 and the Pacific Coast highway. This is a highly traveled two-lane road. The less disruption the better. Trenchless bursting was a good choice.”
Static Pipe Bursting
During the static bursting process, specially designed bladed rollers are pulled through an existing line by a hydraulically powered bursting unit. As the bladed rollers are pulled through, they split the host pipe. An expander attached to the rollers forces the fragmented pipe into the surround soil while simultaneously pulling in the new pipe.
The specially designed bladed rollers actually split the host pipe instead of ripping or tearing it. This is a clean process and prevents potential damage to the product pipe.
Patented Quicklock bursting rods are linked together, not screwed together like traditional drill stems or other systems. This speeds the installation process as well as the breakdown procedure. The rods can be quickly removed one at a time at the exit pit as bursting is in operation.
Approximately 700 feet of the main was designated to be replaced and upsized with 10-inch HDPE SDR 9 pipe. The run was divided into two 350-foot sections with an exit pit dug in the middle. Launch pits were dug on each side of the run.
The crew began by placing the Grundoburst 800G bursting unit from TT Technologies in the exit pit and inserting the locking bursting rods through the first run to the launch pit. A flexible guide rod attached to the front of the first rod was used to help ensure the smooth installation of Quicklock rods.
Once at the launch pit, the J. Fletcher Creamer crew removed the guide rod and attached the bladed cutting wheels, bursting head, expander and new 10-inch HDPE. The entire configuration was then pulled back through the host pipe by the hydraulic bursting unit. The 8-inch ductile was effectively split and the new HDPE was installed without incident.
After a day of heavy rains, the bursting unit was repositioned 180 degrees in the exit pit and prep began for the second run. The procedure was repeated and the second section of main was successfully replaced. Crews then set to work connecting the new pipe with the existing pipe and restoring the exit and launch pits. Once connected, the entire system was pressure checked before being put back into service.
Mallakis was pleased with the static bursting results. He said, “This was a project that needed to be done quickly. It had to be done in a way that didn’t impact traffic and open cutting wasn’t competitive. The static method allowed use to meet the requirements of the job.”
Lippman said, “By using the static system they only needed to open up three sections, a pit on each end and one in the middle. That had a very minimal impact on traffic. If we had used traditional open cut methods, we would have had to close a lane. The static method worked very well in this situation.”
Orton said, “Working with the J. Fletcher Creamer crew is always a pleasure. And I think the forward thinking that is so much a part of the Las Virgenes facility showed through in their willingness to look at different construction methods and choose the best one for the project.”
by Jim Schill