The City of Philadelphia is the cornerstone of history in the United States — it’s the birthplace of so many historical sites and people from the Declaration of Independence to Benjamin Franklin to the Liberty Bell to Independence Hall.
The city oozes with historical significance, yet its city leaders refuse to live in the past when it comes to the care and well being of its infrastructure — something that keeps the city thriving and operating on a daily basis. They are using trenchless technology to proactively and aggressively maintain its water and sewer systems, many parts that date back 150 years.
Admittedly conservative in its approach in the past, today the City of Philadelphia is a leader in its use of trenchless technology, looking for new ways to employ the technology to wisely and cost-effectively use the tax dollars entrusted to them by their citizens.
Instead of reacting to infrastructure problems, the Philadelphia Water Department acts to stay ahead of them using various trenchless techniques such as CCTV video inspection to inspect and assess the condition of its pipe before a problem occurs, saving money and headaches in the long-run.
The city’s first venture into trenchless technology came in the mid-1980s, using cured-in-place pipe (CIPP) to rehab what was considered a tough, off-street location that would have been difficult to use open-cut methods. The success of that project triggered more CIPP projects, initially doing one to two projects every few years. Today, as much as 5 to 10 miles are planned for rehab each year.
“Early on, it was real expensive, probably four to five times the cost of digging up the pipe. But times have changed and we’ve gone from using [trenchless technology] in extreme cases to using it for run-of-the-mill projects that we would not have considered in the past,” says Jeff Twardzik, assistant engineering supervisor for the City of Philadelphia Water Department. “We now consider it alongside reconstruction and in most cases, it’s preferable to reconstruction, depending on the location and situation.”
At 1.54 million people, the City of Philadelphia is the sixth-most populous city in the United States and is considered a major commercial, educational and cultural center — and a popular tourist destination. The City has 3,300 miles of water lines and more than 3,300 miles of sewer lines to service its more than 1.5 million residential and commercial customers, as well as customers in Bucks, Montgomery and Chester counties.
The average age of the water and sewer lines is approximately 75 to 80 years old. Twardzik describes their condition as being in pretty good shape when compared to other municipalities of similar size, with pockets of deterioration and standard problems that come with aging infrastructure. The City has a lot of brick sewers that were built at the turn of the 20th century, as well as many built of clay and concrete. Over the years, reinforced concrete pipe has been the primary pipe of choice, with ductile iron and steel being used sparingly in areas with challenging soils. The water mains are primarily ductile iron, cast iron and steel.
“We do a lot of CCTV inspection and we have found that these old brick sewers are actually holding up very well. Clay and brick have been used throughout the city’s existence. The brick has held up but it’s the mortar that tends to gets eaten away by chemical attack or erosion. We hope to get as much life out of them as possible,” Twardzik says. “The clay is very brittle and tends to crack and can break apart very easily. We tend to rehab more of our clay sewers compared to our brick sewers in a lot of cases.”
Twardzik credits the solid condition of the water and sewer systems to the proactive and aggressive approach the City of Philadelphia Water Department takes when it comes to maintaining its underground infrastructure. He notes that the department has standard age issues that come with an older infrastructure, such as an occasional large water main break or sewer collapse that disrupts the city but the ongoing maintenance program minimizes those occurrences and the upgrades in equipment over the years allows workers to tackle most issues that arise.
Twardzik has been with the Philadelphia Water Department for more than 16 years and manages its lining programs. When he came aboard the department, he had no experience with trenchless technologies but he was soon charged with researching the various trenchless methods and companies for the department, most notably CIPP.
Early on Insituform was the only CIPP company around and the City worked with them as it took its first tentative steps into trenchless technology, not knowing what to expect. “At that point, they were the only company that did CIPP. They held the patent,” Twardzik said. “So we took a leap of faith and worked with them. Once the patent expired, the market just opened up. A lot of companies came into the CIPP market but they didn’t have the experience or expertise. We had to sift through those companies to determine which were the good companies and the ones we wanted to work with. Luckily we had the opportunity to take the necessary time to do the research.”
Today, the City of Philadelphia is a leader in the use of trenchless technologies, employing several of them such as CIPP, gunite, microtunneling, jack-and-bore, cleaning and cement lining, horizontal directional drilling and sliplining. The City is currently working on an HDD project under the Schuylkill River that is in its design phase.
“We’ve done a lot of different things,” Twardzik says. “We haven’t done any pipebursting yet, although we have considered it in the past. We have a lot of utilities especially in center city, and with so many congested areas, we just don’t want to take the chance of damaging them.”
In the last year, the City has also completed a spray-on epoxy water main lining project involving a 30-in. line that had two leaks. Not enough time has elapsed to determine the end-result of this project. The City has 700 to 800 miles of transmission mains and typically replaces approximately 20 miles of water mains each year, of which less than a mile is more than 20 in. in diameter. Using trenchless lining on its larger water mains is something Twardzik notes that the City would like to use but it’s cautious, given that not much CIPP trenchless lining has been done on large water mains yet.
“We are interested in relining the mains that are 16 to 60 in. in diameter,” Twardzik says. “It’s like [CIPP] was 15 years ago and there weren’t many companies doing it and the market didn’t have a wealth of experience yet. In the next five years, I’d like to have installed a few of these [CIPP]. If it works out well, [water relining] will probably go the way of our sewer relining program. We hope to potentially be lining a mile or two a year using cured-in-place in the future.”
The City also rehabs a portion of its 85,000 manholes each year but does so by incorporating them into planned relining projects — which is similar to what many municipalities do.
Philadelphia Trenchless Program
The City has developed a pretty exhaustive inspection program, targeting 200 to 300 miles of the system each year for inspection and assessment. The department has eight to 10 video inspection units and trucks, using equipment from CUES, Envirosight and R.S. Technical.
“We outline a 20- to 30-block radius and proactively inspect all the pipes in that particular neighborhood,” Twardzik says. “We are looking for the worst locations. Obviously the older sections of the city are in the worst condition. We try to target areas where we’ve seen past problems and focus our inspection efforts in those areas.”
The City spends approximately $2 million to $3 million annually on its sewer assessment program and that has included upgrades to its video inspection equipment as well as expanding the areas that are included in inspections.
“In the last five to 10 years, we’ve really stepped it up. We use our CCTV equipment as a diagnostic tool to
figure out what’s going on,” he explains. “We used to be reactionary and now we are really proactive. We inspect approximately 1 percent of the system every year.”
Typically, the City targets approximately 20 miles of water line for replacement each year, using a system that determines which ones are in the worst condition based on the number of breaks, leaks, low pressure, age of the main, material, etc. From the sewer side, on average, seven to 10 miles of sewer lines are replaced each year — but the use of trenchless technologies allows the city to rehabilitate rather than dig-and-replace many of those aging lines.
While using trenchless on the water side of things is still in its early stages in Philadelphia, Twardzik sees this as an untapped, viable method to cautiously pursue. But on the sewer side, trenchless techniques are employed whenever the situation allows and have become a key component to its infrastructure maintenance program.
The problems that Philadelphia’s infrastructure presents are no different than any other large city, with age of the pipes being the primary factor. Twardzik says the pipes don’t have a lot of problems with hydrogen sulfide affecting them. “Really it’s just age. The system has been fairly well built over the years. We have [sewer] pipes that are in some cases 150 years old. At some point they are going to break down, but we have been able to maintain and rehabilitate them over the years.”
CIPP has become the cornerstone of the city’s sewer maintenance program, averaging approximately $4 million to $5 million of the $40 capitol improvements budget. “We’ve held steady at that amount over the last five years or so,” Twardzik says. “We haven’t been able to expand but this past fiscal year was probably the most productive year in our CIPP program. We’ve been very aggressive, putting out six or seven projects totaling 10 miles which are now awaiting bids, and we have another $17 million worth of design work ready to be completed and sent for bids in the next three to five years. We will string them out over next few years.”
The City has also implemented chemical root control as part of its regular maintenance program, which helps keep the pipes clear of roots and debris. In the past, lining contractors would just cut the roots as necessary but now the City is addressing this as a long-term solution to pipe maintenance.
But spending money on underground infrastructure projects as it has done the last 10 years wasn’t always business as usual here. In the early 1990s, the City was in a financial crunch and severe cuts were made in order to get the City on its feet — infrastructure projects felt those cuts. Once the financial crisis was over, funding for infrastructure returned. In the early 1990s, the department was spending $20 million annually on infrastructure projects and $30 million annually by the late 1990s. In the 2000s, the budget reached $40 million.
Twardzik is a vocal proponent of trenchless technologies, noting their cost-effectiveness and social impact. He notes that cost for trenchless methods have come way down over the years, by as much as 50 percent in some cases and bringing them in line with or even lower than reconstruction costs.
From a social standpoint, using trenchless in an historic city such as Philadelphia seems obvious. Home to a booming tourism business, the last thing city leaders want is construction work preventing visitors to their city from getting around to its attractions. Using trenchless allows the work to be done basically right under the nose of those visitors and the community at large.
“We feel like this is helping the tourism industry,” Twardzik says. “We have tourist activity here 24/7 and summertime is a huge market for the city. We have done extensive work with CIPP and gunite in [those historic] neighborhoods in attempt to avoid as much disruption as possible.”
He notes that use of trenchless has been used in Center City and Olde City — two of the oldest parts of the city and home to historical attractions — and has limited disruption to those businesses and tourist sites.
Twardzik says his department stays abreast on the latest happenings in the trenchless industry by attending conferences, such as the No-Dig shows, to network with other cities and learn how they are handling their infrastructure. “If you want to be in the forefront of the industry, then you have to keep up with what is going on,” he says.
Sharon M. Bueno is managing editor of Trenchless Technology.