The City of Santa Rosa, Calif., is not unlike most cities across North America when it comes to the upkeep of its underground infrastructure — one of its most important assets. The City strives to make the system operate in such a way that its customers don’t have to give it a second thought as they go about their daily routines.
But what Santa Rosa folks don’t realize — as well as many people across North America — is that it’s a jungle down below the surface, with utility officials working to keep capacity, flow and a sound system structure operating at top efficiency.
One of the issues that Santa Rosa deals with is the battle of roots trying to intrude and maneuver their way through the underground sewer pipes where they can wreak severe problems on the collection system, causing capacity problems, impede flow and create blockages and overflows. Lucky for the people of Santa Rosa, its Utilities Department has been proactively fighting and winning this battle through its root control program that has been in place since the early 1990s.
“The root control program has proven to me that it’s well worth its cost,” says Mark Powell, deputy director of local operations for the City of Santa Rosa Utilities Department. Powell has been involved with water and wastewater for his entire professional career, coming to his city position in 1990 after working more than three years with another city and 15 years with a services contractors, dealing with municipal maintenance (including root control), repairs and replacement of sewers, storm/area drains, septic and other projects.
The City of Santa Rosa is located about 55 miles north of San Francisco, with a population of approximately 165,000. The City’s Utilities Department services some 53,000 residential, commercial and industrial customers through its 589 miles of sewer main, ranging in diameters of 4 to 66 in. Like all municipal systems, the Santa Rosa system is aging, with a portion of its sewer mains more than 80 years old, some even approaching 90 years old. Portions of the system are operating beyond its 50-year expected service life.
All things considered, the system is in pretty good shape, Powell says.
Among the City many attributes is that it is recognized as a Tree City USA city, which means there are an abundance of trees throughout the city, dotting the landscape in all their vibrancy, shade and beauty. But with those trees comes “out of sight, out of mind” problems for collection system operators, such as Powell.
“We have a lot of trees and people have planted them in their yards and easements, right next to or on top of sewer lines and laterals,” he says. “People don’t realize the problems trees create underneath the ground. If the root senses water, it can weave its way the size of hair into a pipe and expand, causing damage to the pipe.”
That damage can be in the form of blockages or joint breakage, which affects wastewater flow/interruption of service, especially on the smaller diameter pipes.
Before Chemical Treatment
Before there were accepted chemical treatments for abating and retarding roots from underground pipes, cities relied on mechanical rodding machines to cut and remove them — but that method did not rid the pipe of the problem and in some cases, made them worse. “Prior to the late 1970s and early-1980s, the only way cities really dealt with roots was to remove them by mechanical rodders or hand rodders,” Powell says. “And just like any tree or bush when you prune, which is what you are doing with the roots, it re-sprouts and can get even more vibrant. So root pruning is not always the best answer.”
The City of Santa Rosa turned to chemical treatments for its root problems in 1989, recognizing the benefits of — no pun intended — getting to the root of the problem. Recognizing the long-term benefits of using chemical treatments, the City developed a chemical root control program. Today, the Utilities Department chemically treats 38,000 ft of sewer main a year and treats the mains every other year.
“We treat the lines every other year and in the “off years” we verify the effectiveness of the process, with CCTV,” Powell says. “The chemicals retard the root growth not only inside the pipe but outside as well, retarding future growth.”
Mechanical rodding is also still a part of the program, used in combination with the chemicals to ensure nothing is missed. “I’m old school,” Powell says. “We will go in and [cut] the roots in the lines the first time that we’re going to treat and then let them sit for 90 days before we apply the chemical treatment. What was happening was the people were treating the lines that had massive root balls in them and the chemicals would work, eating the roots away but the root ball would go down the pipe further and plug it up. My experience has been to pre-rod the lines before treatment to prevent that from happening.”
According to Powell, the City annually spends approximately $52,000 on its root control program — which includes material, labor, equipment, maintenance and replacement cost — and has been in full swing since 1992. The Utilities Department does all its root control work in-house, using its 29-member staff, two of which are licensed applicators. All Utilities Department employees have California Department of Health Services Water Distribution licenses and CWEA Collection System Maintenance certification at different grade levels.
Pipe Maintenance and Repair
The Utilities Department does more than implement an effective root control program to maintain and extend the lifecycle of its sewer mains. Powell says they use CCTV (operating two video inspection trucks daily), as well as an asset management program to determine how to best manage its system. “We inspect the entire system within seven years using CCTV,” he says. “On the bigger diameter lines and trunk lines we use robotic scanning to determine what other issues may be going on, plan for replacement, capacity issues, illegal connection and so on. We try to clean all pipes that are 36 in. and smaller every five years.”
All the information is gathered into one system/place, which is reviewed by the collection operations, and asset management staff and prioritized for future replacements as budget allows.
Powell further notes that the workers clean the city’s 36 siphons monthly, as well as maintain 17 wastewater lift pump stations.
Through the City’s Environmental Compliance department, a Fats, Oils and Grease (FOG) program is enforced and every commercial and industrial businesses are permitted and inspected. FOGs can be a serious source of damage to sewer lines and Powell says enforcement, education and regular cleaning are deterrents to long-term FOG problems.
“They do a great job,” Powell says. “We all work together as a team. If our crews are out cleaning or making repairs and they see something that’s abnormal, we let them know. Most of the time we are the first to find an issue.”
The City also incorporates trenchless technology when addressing the rehab needs of the system, including pipe bursting and cured-in-place pipe (CIPP), the latter first being used in 1992.
All of these efforts have resulted in less service interruption for customers — which Powell says is the department’s No. 1 goal — as well as decreased the number of blockages, stoppages and overflows over the years. “During the early 1980s, we would have three or four overflows a month,” he says. “Today we probably have one every six months.”
Powell says when cities are researching whether to create and implement a root control program, they need to ask themselves this question: Is it cost-effective for their area or system? Being proactive regarding maintenance issues is a critical in this era, as more is being asked of cities with less resources at their disposal.
Having such an extensive professional career in dealing with municipal underground infrastructure (a career that started in 1972), you would think there wasn’t much Powell hasn’t seen. Think again, he says.
“Have I seen it all? No way— just when you think you have, something new comes up,” Powell says, chuckling. “There’s always a new wrinkle somewhere, which makes our jobs challenging and interesting.”
Sharon M. Bueno is managing editor of Trenchless Technology.