While the City of Charleston, S.C., has about 118,000 citizens, the Charleston Water System distributes water to almost 400,000 customers in and around the city.

The system is blessed with more than ample surface water to meet its needs for decades. Its greatest challenge is to maintain 1,400 miles of water mains through a diverse terrain that includes a sensitive downtown historic district, tidal flats, corrosive salt water marshes, a harbor, and the beds of Elliot Creek and the Ashley and Cooper Rivers. A program of extensive leak and corrosion detection and aggressive preventive maintenance initiatives helps the system meet those challenges.

When Kanwal Oberoi became director of water distribution in 1996, he found a water department that practiced little routine maintenance, and a repair schedule that made ineffective use of staff.

Today, the department aggressively searches out leaks with a regular detection program and keeps mains, hydrants and valves on a regular program of preventive maintenance. Trenchless technology helps crews repair lines in the city’s historic district with minimal disruption.

First order of business

The first order of business was to get a handle on exactly which functions were being performed and to write procedures that incorporated best practices. Rather than bring in a consultant, Oberoi had the staff write the manuals themselves, in plain English, so that they could take ownership.

“Right now, I have a procedures manual 4 inches thick, and it’s been written almost entirely by the staff,” says Oberoi. “Each employee who contributed to a procedure has his or her name inscribed beside that procedure permanently, so that they retain ownership of that idea forever. It doesn’t just disappear into a group exercise.”

Part of the effort to modernize the department involved the creation of an aggressive leak detection and main repair program that achieved more while saving labor and reducing cost.

“In the 12 years I’ve been here, we have cut the size of repair crews from six people to three, including a supervisor, and cut the average price of a repair from $500 to $400, despite rising wages and material costs,” says Oberoi. “After making the repair crew more efficient, the biggest challenge has been to keep material costs down as well.”

Repair and testing

The main repair and testing regimen involves a combination of preemptive-leak detection and extensive analysis of the condition of mains. The distribution mains are largely made of cast or ductile iron lined with cement, ranging 2 to 48 inches. A few high-service mains coming from the city’s Hanahan Water Plant are as large as 54 inches.

“We have some HDPE pipe and plastic pipe as well, running underneath the river beds,” says Oberoi. Some of the pipe dates back to the 1800s. The leak detection program operates on a five-year cycle. The program is so efficient that it requires only one worker on shift to perform the scans.

The major tool in the leak detection arsenal is a Fuji LC-2500 Leak Noise Correlator, purchased in 1998. It is the only one of its kind in the state. “It has proved its worth by serving us through two full scans of the water main distribution system,” says Oberoi. “It has proved extremely accurate in pinpointing hidden leaks to help us get to problems without false starts and over-digging.”

Because Charleston is on the Atlantic Ocean, much of the distribution system runs through corrosive soils, especially salt marshes. The department has mapped potentially corrosive soils in high-profile areas and performs solid sampling electric potential surveys to find soils that have higher moisture content attributable to leaks. When potential leaks are discovered, a city engineer evaluates the data and prescribes remedies.

Some leaks can be difficult to detect. For example, a leak that affected water supplies to Sullivan’s Island and the Isle of Palms in September 2008 was traced to a break in a main at the bottom of Charleston Harbor.

The entire system has been scanned twice since the purchase of the leak detector. The second full scan showed an overall improve-ment in the condition of the mains. That’s not entirely the result of the leak detection program.

Proactive maintenance

“Between the information we’ve collected and the work of a consultant, we’ve developed our own proprietary matrix to determine which pipes are due for routine repair or replacement,” says Oberoi. The matrix considers such factors as pipe size, age, composition, flow rates, the number of breaks and leaks previously detected, and the corrosiveness of the soil.

The information is correlated to maintenance cost of the existing pipe, the loss of effective pipe size, and the criticality of the pipes, including their location and proximity to other construction projects. A final score determines whether the pipe will be replaced or repaired.

The staff also performs preventive maintenance on some 7,200 fire hydrants and 40,000 in-line valves. Valves are designated critical and non-critical, and larger valves receive special attention. About 70 percent of the department’s budget goes toward preventive maintenance, including an aggressive pre-emptive program to clear mains of mineral deposits through routine flushing of fire hydrants.

Two-person crews perform maintenance according to the system’s standard operating procedures. Like all employees, these crews are monitored according to productivity markers calculated each month that translate into incentives, such as lunch vouchers.

“Crews in every category compete with each other to reach or exceed productivity targets,” says Oberoi. “No matter what type of work is performed in the department, we have a productivity standard that’s expected to be maintained. We also have productivity targets for the entire department. Everyone is rewarded at month’s end if targets are met.”

When a repair is required, the department most often chooses dig-and-replace. “Most of our mains are located only about 4 or 5 feet below the surface of the soil, which obviously never freezes,” says Oberoi. “It’s simply cheaper for us to dig a shallow trench to make water main repairs.”

Cast and ductile iron pipe is usually replaced with more of the same, except for pipes running under the city’s rivers, where some HDPE and plastic is used. In 1998, the department lined 2,600 feet of century-old 6-inch cast iron main with epoxy.

While the relining improved flows, the cost totaled about 55 percent of the cost of a new ductile iron main. “Because of the graphitization of the cast iron main, and because the epoxy did not provide any structural support, the life expectancy of the relined pipe was estimated at only 20 to 40 years,” says Oberoi. “Installation of a new cement-lined ductile iron main has a life expectancy of 100 years, so the math favored replacement.”

Historical challenges

The city’s historic district, where cobblestone streets and period architecture date back to the 18th century, requires special attention. The downtown area carries the highest traffic densities and contains the oldest mains in the system.

“Over the past 10 years, we’ve located and repaired or replaced a lot of the problem mains in that area,” says Oberoi. “When we began to concentrate on the area, we ran the water at 40 psi to make sure that we didn’t rupture any mains that were already compromised. Since we’ve focused our attention here, we’ve been confident enough to increase the pressure to 50 psi.”

The work in the historic district is exacting. Repair crews are required to call in an archaeological expert each time they excavate. “Anything we remove, we’re respon-sible for putting back exactly as we found it,” says Oberoi. “If we remove a cobblestone, we have to number it, and we have to return it to its original location.”

In one case, an archaeologist helped repair crews identify a large, spherical metal object they unearthed. “It turned out to be a bomb — a live bomb — from the Confederate era,” says Oberoi. “We had to call in the military to dispose of it.”

It’s in the historic district that the department is aggressively exploring trenchless technology, particularly since the cost of relining has decreased since the 1998 pilot project. “In an open area, it’s still cheaper to excavate, but our department bears the full cost of rehabilitating the area after a dig,” Oberoi says. “If we can eliminate the cost of historic restoration, trenchless technology makes economic sense here.”

Charleston is looking at two products. Insituform Blue Thermo-pipe by Insituform Technologies Inc. is a polyester-reinforced polyethylene structural liner for severely deteriorated pipes. Another product under investigation is Aqua-Pipe by Sanexen Environmental Services Inc., a structural liner impregnated with thermoset epoxy resin.

“Whatever we choose, the product needs to provide structural support to the mains, or the investment won’t pay off,” says Oberoi.

System continues to grow

Charleston continues to grow, and the water system will grow with it. Oberoi is proud of the recognition the system has garnered so far, including ISO 14001 certification for environmental management, one of the country’s first departments so recognized. The system was also awarded the state’s 2006 Area Wide Optimization Program Excellence Award for treating drinking water beyond what’s required by regulation.

“This type of recognition, in addition to meeting or exceeding our own productivity targets, shows us that we’re on the right track,” says Oberoi. “We received a Governor’s Award for being the best-run utility in the state.

“In the next five years we want to be considered for the President’s Award for the best-run corporation in the country, and we want to achieve that while providing quality water at a fair price. Our customers will let us know if our efforts at continuous improvement are taking us there.”