The El Dorado Irrigation District (EID) in northern California has stepped up its efforts to rid its service area of unwanted and damaging blockages by implementing a comprehensive, integrated chemical root control program.

The results of that program — created as a pilot program in 2007 — show a significant drop in sanitary sewer overflows (SSOs) and better maintained and stronger infrastructure, as well as a significant drop in sanitary sewer overflows (SSOs).

“The integrated root control program, in conjunction with our CCTV inspection program, has provided us with
excellent results,” said Mark Haverson, senior construction maintenance worker, who helped design the EID program. “We have seen firsthand the roots decomposing and breaking down. We have evaluated a lot of root-infested pipes and we have gotten great results. The main goal of our department is to alleviate and lessen the number of SSOs.”

And they have. Haverson said that before the pilot program began, EID had 10 SSOs per 100 miles of pipe. In 2010, that number was reduced to five SSOs per 100 miles of pipe. To date in 2011, the number of SSOs is approximately one half of 2010’s total.

“Many factors have contributed to our success but chemical root control is a major factor,” Haverson said.

Background


El Dorado Irrigation District is a water utility serving nearly 100,000 residents in northern California’s El Dorado County, which is situated east of Sacramento and extends to  Lake Tahoe. The district’s 220-sq mile overall service area, with 77 sq miles comprising the collections system’s service area, includes portions of Cameron Park, Camino, Diamond Springs, El Dorado, El Dorado Hills, Placerville, Shingle Springs, Pollock Pines and Rescue.

Formed in 1925 under California’s Irrigation District Law, EID operates 334 miles of gravity sewer lines, 83 miles of force mains, 7,700 manholes, 64 lift stations and 18,600 service laterals. Located in northern California’s mountainous region, EID is home to mainly an affluent community, as well as senior citizens.
A relatively new underground infrastructure system, the oldest pipe in the ground right now was installed in 1961; pipes range in size from 4 to 36 in. and are made up of PVC, ductile iron, asbestos cement and vitrified clay.

Like many utilities, EID has been dealing with root-intrusion issues on a daily basis. Haverson understands how detrimental roots can be to a system. “They cause separation of pipe joints and have negative effects on the integrity of our infrastructure,” he said. “When roots get in there, they impede the flow of the pipe, creating SSOs. They also can create a buildup of grease behind the blockage, causing even more problems.”

In the past, crews would use mechanical and hydraulic means to clear blocked pipes but Haverson said continued and constant use of this method would jeopardize the integrity of the pipe. “We learned we were actually impeding the integrity of the pipe by constantly beating it up and cutting it,” Haverson said. “Also, when we would cut the roots, they would grow back faster and even thicker. You are really defeating the purpose and it would actually take longer to cut through the root mass. So that cutter has to be in the pipe longer to cut it out, and you end up tearing the heck out of the pipe.”

EID decided an alternate method was needed to be used in conjunction with its CCTV and mechanical root control work. Haverson and EID researched the chemical root control products available and selected Vaporooter as their choice.

“What we found is that it’s more efficient to use chemical root control,” he said. “Some areas it’s really warranted because of the sensitivity of the area. If you are looking at a pipe and it has Redwood trees around it, such as in El Dorado Hills, which is a very wealthy community, you are going create problems if you want to take the trees down.”

Haverson describes EID’s integrated root control program in three parts. First is the evaluation of the infrastructure’s condition using EID CCTV crews to inspect the pipes. “We need to know the severity of the root problems and where they are located,” he said. EID uses Pearpoint cameras and data software for this work, handling the work in-house.

The second part of the program is to use mechanical and hydraulic means to remove roots. “If we have this huge root mass and it’s really dense, we will give it a hair cut and remove it and then apply a chemical application to it. If we don’t cut it first, it will die [after the chemical application] and break off, creating
another blockage further down the pipe.”

The third part involves putting the pipes on a chemical application cycle, which keeps the pipe maintained.
The first chemical application occurs six to eight weeks after the roots have been cut and then is scheduled for a re-application in a year and then a third hit in two years. Once this cycle is completed, a CCTV inspection is done to evaluate the progress. Afterward, the pipe goes on a three-year maintenance program.
Haverson credits the success of the program in part to the good work of the EID inspection crew. “They are the eyes in the pipe. We do our own televising, inspection and chemical application. It’s more cost-effective for us to do it this way because we know our system and we know our district policy,” he said. “[The CCTV crew] give[s] us a before and after look [of the pipe] and that’s big selling point for a municipality if they want to use an integrated root control program.”

EID and its board of directors are more than happy with the results. “Now everything is on a maintenance schedule,” Haverson said. “With CCTV inspection, hydro-cleaning and chemical root control to supplement our  pipeline maintenance program, we are now dealing with any existing issues that we have, as well as proactively addressing potential issues.”

Sharon M. Bueno is managing editor of Trenchless Technology.

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