A University of Texas at Arlington team will inspect 350 concrete manhole shafts for corrosion in the city of Arlington and develop a method to prioritize which manholes need protection from corrosion the most.
The Arlington City Council approved the three-year $474,723 project that will measure the hydrogen sulfide and multiple other parameters that influence manhole corrosion. Each manhole is four to five feet in diameter and in Arlington can range from four to four-and-a-half feet tall.
Corrosion of manhole shafts can threaten the structure integrity of sanitary sewer mains and can allow rain and other runoff from the surface to enter the wastewater system.
Buzz Pishkur, city of Arlington's water utilities director, said, "The new study will give Arlington water engineers and other cities across the country the data they need to protect vital infrastructure and spend funds wisely. UTA is a renowned center for the study of pipe technology and evaluation of alternate pipeline materials to meet the needs of cities. We are fortunate to have a center of research in our city and value the partnership on this and other key infrastructure efforts."
Melanie Sattler, UTA associate professor and the Syed Qasim Endowed Professor of Civil Engineering, will lead the project. Victoria Chen, the George & Elizabeth Pickett Professor in the Department of Industrial and Manufacturing Systems Engineering; and Arpita Bhatt, an adjunct professor in civil engineering; are on the team.
"It makes sense for Arlington to develop a system for prioritizing protection of its manholes," Sattler said. "Manholes can corrode because of the creation of hydrogen sulfide gas. Some readings can be really, really high. We will determine which manholes need a protective coating to protect them from corrosion. To coat all of them would not be feasible."
Microbes in the sewer convert the hydrogen sulfide gas to sulfuric acid, which then corrodes the manhole concrete. Sulfuric acid also corrodes the pipes adjacent to the manholes.
Sattler said the team will use sensors to measure the amount of hydrogen sulfide, study velocity of flow and inspect corrosion that might already be underway to determine which manholes need help first.
Arlington has more than 19,000 manholes citywide. The UTA project will inspect different categories, types and geographic locations of Arlington manholes.
Although the study will prioritize corrosion protection of the 350 manholes, the more important aspect of the project is to use the data from the 350 to develop a system so the city can prioritize the rest of the manholes.
Sattler said this is a companion project of sorts with UTA's Ali Abolmaali's Large Diameter Sanitary Sewer Assessment Program with the city of Arlington that was granted in 2015.
That project employs a robot to inspect miles of the city's sewer pipes. It, too, will be used to prioritize the city's pipes so that better decisions can be made to repair the ones that need it most.
"It's exciting that UTA is at the forefront of helping the city of Arlington," said Abolmaali, chair of the Department of Civil Engineering and the Tseng Huang Endowed Professor of Civil Engineering. "UTA professors further investigate and discover the tools of their trade in these collaborations. UTA students receive vital field work experience in collecting the data in these projects."