An asset and inventory assessment of Warrenton’s sewer system revealed a number of ongoing problems, mainly related to the condition of terra cotta clay sewer pipes.
Gary Flowers of Municipal Engineering Services Company, PA presented a report during the Warrenton Town Board’s Nov. 9 meeting.
In March of 2018, Warrenton was awarded a $150,000 wastewater system AIA grant from the North Carolina Division of Water Infrastructure for creating a geographic information system map of the town’s wastewater collection system and to conduct a condition assessment of segments of the gravity sewer system.
The funding was a 95 percent grant from the Department of Environmental Quality with the town of Warrenton providing a 5 percent, or $7,500 match, along with a 1.5 percent grant fee in the amount of $2,250.
Flowers said that assessments focused on segments of the sewer system identified by the town as critical due to age, condition, sanitary sewer overflows and suspected inflow and infiltration. This included some 11,900 feet of sewer pipes and 49 manholes.
The study found some cast iron and new PVC piping in the sections that were studied. However, most of the areas that were assessed contained terra cotta pipes which become brittle over time. Flowers said that 92 percent of the pipe system studied was in poor condition.
He said that clay piping becomes brittle over time, making it susceptible to cracking and other problems.
In addition, Flowers said that clay pipes are much shorter than modern pipes. Modern pipes are typically between 15 and 18 feet long, while clay pipes are usually four feet in length. That means that many more pipes have to be connected to construct a sewer system out of terra cotta clay than of modern pipe material, meaning that there are more connection points that can become weaker over time.
The assessment revealed a number of pipe defects, including cracks, fractures, holes, offset joints, roots and pipe sags.
Flowers noted that more than 10,000 feet of sewer pipes would have to be replaced at an estimated cost of $1 million to correct all of the problems. He noted that a number of manholes also were in poor condition, with problems including cracks, holes and roots.
Flowers said that having the asset and inventory assessment would assist the town of Warrenton in planning future work on the sewer system, prioritizing areas of most critical need and securing funding sources such as grants to complete the projects.