The City of Pearland, Texas, 25 miles from Houston, is a microcosm of the trials of wastewater infrastructure management.
Old Town Pearland dates to the 1930s and 1940s, and waves of population since then have created a jumble of sanitary sewers, old and new, leaky and tight. Recently, the city has added hundreds of new connections a month to its system of five wastewater treatment plants, 78 lift stations, and 12 water stations.
Until recent years, operators tracked most of these facilities manually, writing field log books from which supervisors transcribed data into the computer. The city now gathers that data using cellular telephones, saving time and supporting sound system planning.
Better data management
In 2005, Bobby Whisenant, then superintendent of water production and wastewater treatment (now retired), turned to BirdNest Services Inc. of Houston for the new data management solution. The company coded the city’s infrastructure into menus for wastewater and water system operators’ cell phones.
Organized by route and station, the menus take each operator through every item of data that must be captured for every station on a given route. The phones perform basic error checking and transmit the data to a central processing center in Dallas. From there, reports are available almost instantly, to city staff members with a computer and the right password.
“What used to take hours and days now takes seconds,” says Whisenant. “It was great, the money the city saved in overtime.”
Long-range planning
The data can be charted and graphed (see accompanying example), making it easy to spot anomalies and trouble spots for quick repair and remediation. But at the outset, no one realized that the system would also support sound planning.
In 2007, Pearland set out to update its 20-year, $200 million wastewater system capital improvement program (CIP). When Eddie Kirst, P.E., of Kirst Kosmoski Inc. consulting engineers in Houston, took on the project, he was pleasantly surprised to find that since the CIP was developed in 2005, two years of detailed flow data, pump run times, rain dates and rain amounts had been collected. He was able to download it all.
“With the BirdNest data, we were able to dynamically model the whole system — every manhole, every lift station, and every piece of property,” says Kirst. “We found that the city didn’t need some projects we had proposed two years earlier based on estimates and sound engineering judgment, and there were other projects we hadn’t projected that the city would need.”
Design and planning
“In terms of long-range planning, the system gives you better projects and helps you construct facilities only where they’re needed,” Kirst says. “It also helps identify problem areas that can be remediated before sewage backs up in people’s yards.”
Beyond that, Kirst notes another cost advantage for new facilities. Texas mandates that in the absence of local reliable flow data and engineering analysis, sewer systems must be designed to convey about four times the estimated average daily flow to allow for inflow and infiltration.
The data provided by the BirdNest system and the engineering analysis provided by Kirst Kosmoski will allow Pearland to reduce the peak factor on some parts of the system significantly. “That’s a huge cost saving, not only in capital costs but also in daily operation and maintenance costs,” Kirst says.
