The city of Santa Rosa faces the same problem as cities through-out California and the United States: a deteriorating wastewater collection system and the need to upgrade and repair it while remaining socially and fiscally responsible.

Mark Powell, deputy director of local operations, carries much of that responsibility as the city works to mitigate the effects of inflow and infiltration. He and his staff are committed to doing better. Santa Rosa, the largest city north of San Francisco to the Oregon border, has strict regulations aimed at I&I control. The department spends about $12 million a year on pipe replacement and hopes to double that in the next five years.

To maximize efficiency and hold down cost, Utilities Depart-ment Director Miles Ferris, city engineers, and operations staff have applied a variety of construction technologies, including trenchless methods. The latest focus development of an in-house lateral pipe bursting program that replaces laterals in the public area from the city main back to the property line.

Multiple methods

According to the city’s I&I report, inflow comes from conditions such as leaky manhole covers, uncovered cleanouts, and private property downspouts, sump pumps, and yard and foundation drains illegally connected to the sanitary sewer system. Infiltration enters through cracked, collapsed and just plain leaking pipes.

Santa Rosa officials estimate it costs $7.50 per thousand gallons to treat and dispose of the clear water entering the pipes. In December 2002, after seven days of rain, flows through the treatment plant peaked at 60 mgd, versus average September flows of 16.2 to 18 mgd.

The wastewater collection system consists of some 520 miles of pipe ranging from four to 66 inches. The older areas typically have sewer mains of vitrified clay pipe (VCP) installed throughout the 1970s. Some of these are fairly brittle, and ground movement from seismic activity, has promoted joint separation and cracks. Root intrusion is also a problem.

The city engineering and capital improvement program (CIP) teams initiated a program of replacing the VCP sewer mains through a wide range of methods, including cured-in-place pipe lining, static and pneumatic pipe bursting, and open-cut construction where appropriate. The city takes an educational and legal approach to codes that prohibit connection of clear-water sources to a building sewer or sewer service lateral connected to a public sewer. Whether it’s a physical repair or an educational effort, success comes from having qualified staff.

The right team

The city’s success against I&I issues is attributable to all Utilities Department staff involved and to sound educational practices. “The keys to success include several important components,” says Powell. “First is our director, Mike Ferris, who is proactive and very involved. Second is the quality of staff. And third, our Board of Public Utilities understands our business, and we take the time to educate them. We provide new board members with a two-day training course. That education is very important, and our entire board appreciates it.

“There is a classroom program where we go through the organization and how budgets are developed. There’s a field portion where we take them out to see firsthand what happens. When we’re talking pipe bursting, for example, we show them what it is, what it does, and why it’s a money-saver. They get the full realm of what they are governing over. But ultimately, I can’t say enough about our director and staff, and the quality job they do. And that goes from the employee at the call center to the person in the field.”

The final component of a successful team is the general public. The city works to involve them in the process through outreach. The program focuses on topics like water conservation, FOG, pharmaceutical take-back, and inflow issues. The department utilizes everything from bill stuffers to a booth at the local farmers’ market, to a Water Fair to make contact and educate the community about water and wastewater.

Lateral replacement

An issue that directly affects homeowners is the city’s lateral replacement program. The push for lateral replacement began long before the city actually purchased equipment and began pipe bursting.

“The bursting program was in the works for more than two years before we purchased the unit,” says Powell. “We budgeted for it and we demonstrated different machines before going to bid, so we knew what the process was and how each machine functioned. We wanted local support, in addition to the items the crews needed to do their jobs better.” The city ultimately purchased a Grundotugger lateral pipe bursting system from TT Technologies.

“The laterals are maintained by the property owner. But, at our discretion, and as a service to our customers, we will repair or replace the portion of the lateral in the public right-of-way at no charge to the homeowner. With the costs associated with trenching, backfill and patching, we purchased a pipe bursting unit so we didn’t have to cut and cover.”

To develop a priority schedule for replacement, the city’s asset management team uses a ranking system that looks at each segment of the system for:

• Condition (age, material, inspection data, service requests).

• Performance (future and existing hydraulic capacity, design standards, flow characteristics).

• Risk (proximity to sensitive areas such as highways and creeks, absence of redundancy for backup, imminent major failure mode).

In addition, the staff considers locations of upcoming road projects and redevelopment areas to determine which sections will be replaced or repaired next. Once a segment is designated for replacement, the job is assigned to the field crews or the CIP team.

All of the city’s operational staff is cross-trained. “They do water and wastewater,” Powell says. “If they go to a job and there’s a water line in the sewer trench and it needs to be replaced, they do that, too. Basically, we have three general repair crews and two leak crews. We also have a weekend crew, as our operations run seven days a week, nine hours a day, 6:30 a.m. until 4 p.m.”

In the trenches

For lateral bursting, crews first identify launch and exit pits, which typically measure 5 feet square. Once the pits are excavated, crews place the bursting system’s winch line through the existing lateral. At the launch pit side, an expander is connected to the first segment of new pipe, in this case, high-density polyethylene (HDPE). The expander and pipe are then connected to the winch line.

At the exit pit, the winch line is connected to the hydraulic bursting unit. Once the hydraulic power pack connections are made, bursting begins. Crews can choose to fuse together the entire length of HDPE at once, or fuse segments during bursting operations. During the bursting process, the expander, which is larger in diameter than the existing lateral, is pulled through the host pipe, breaking it apart and forcing the fragments into the surrounding soil. The new HDPE pipe is pulled into place simultaneously.

While ultimately Santa Rosa homeowners are responsible for the portion of the lateral on their property, Powell knows that replacing the portion in the public right-of-way helps mitigate I&I while providing outstanding customer service. Being able to replace those laterals through trenchless pipe bursting keeps residents happy and saves time and money.