By C.V. Moore
OAK HILL —
City officials are getting closer and closer to an understanding of Oak Hill's aging sewer system and how it might one day be improved, thanks to a study of the system by an outside consultant.
The Inflow & Infiltration study, part of a much larger $14 million sewer improvement project aimed at cleaning up the New River, is now three-quarters complete.
Oak Hill’s sewer system works well under normal circumstances, but during heavy rains, storm water gets into the system through breaks in lines, manholes, and illegal connections to gutter downspouts. The wastewater overloads the city’s sewage collection and treatment system and overflows into Arbuckle and Loop creeks, which feed the New River.
Known as “inflow and infiltration,” or “I&I,” this phenomenon is most often caused by aging infrastructure that needs maintenance and repair.
The purpose of the study is to identify deficiencies in the system in order to develop a rehabilitation project for the areas of critical concern. It will also provide data so that city officials can undertake long-term planning. When the project is complete, the sewer system will be mapped in the city’s new GIS system.
“This is going to go a long way in mapping our sewer system. We don’t have a good grasp of what all is out there in the ground,” said Oak Hill City Manager Bill Hannabass when the project was launched earlier this year. “It’s going to give me a tool to plan better to not only operate the system but maintain the system.”
Pentree Engineering, which is undertaking the study, reports the existing system is “in typical condition for a municipality such as Oak Hill. Much of the old system has the normal deficiencies found in gravity collection networks.”
“Leaking structures, root penetration, corrosion, erosion, concrete deterioration are prevalent throughout the network. There was also evidence found of backups due to sagging lines and lack of proper design effort. There are portions of pipeline laid on top of the ground.”
Pentree employees have been searching for the city’s 882 manholes, but that can be difficult given the system’s age. Some have been buried or paved over. The rights of ways are often blocked by trees, brush, and thick undergrowth.
So far, surveyors have located 555 of the manholes.
Five flow meters are also set up and monitoring the sewage collection system. Flow metering will continue through 2013.
The New River Clean Water Alliance, a grassroots group of locals working on water quality in the region, just wrapped up a water monitoring project in Arbuckle Creek — with monitoring points above and below wastewater plants — to better understand where fecal coliform pollution is coming from in the creek. Arbuckle Creek is a major source of pollution in the New River, according to a report released by the group last year.
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