Home to Birmingham, and more than 660,000 residents, Jefferson County is Alabama’s most populous county. The sewer network the county maintains includes 3,600 miles of pipe and 80,000 manholes. That last figure represents a sizable amount of annual maintenance; though manholes themselves are durable infrastructure, they do need to be kept at grade—level with the top of the pavement—to prevent inflow and infiltration (I&I), and to avoid roadway degradation and traffic hazards.
So whenever Jefferson County roads are paved or repaved, manholes usually need to be raised to match the new roadway thickness. And that responsibility falls to the Jefferson County Commission's Environmental Services Department, who maintains the sewers for the whole county including all municipalities. “We’re responsible for raising our manholes to grade whenever a road is being repaved,” says Jefferson County Commission Sewer Construction Maintenance Supervisor Brian Champion. “The municipalities let us know whenever they have road work scheduled, and we work with contractors to raise the manholes just before paving.”
The amount of manholes raised annually depends on the amount of paving done by municipalities, and is unpredictable. Some years, the department raises as few as 50 manholes, but fairly often that number rises to 300 manholes or more. This much variability in annual manhole maintenance costs can be a budget buster, especially if the manholes are raised conventionally by digging out utility frames and building them up with brick and mortar. That process can be a day’s labor for a crew, plus the expense and sustainability costs of hauling waste.
Fortunately, Jefferson County rarely needs to raise manholes the traditional way, with the rare exception being when the paving lift is about 4 in. But most of the time, the county uses manhole risers—specifically, Pivoted Turnbuckle Manhole Risers made by American Highway Products. These risers are used by sewer departments all over the U.S. and are based on a simple, even obvious, concept—tough, galvanized, flexible rings of U.S. steel are placed in old manhole rims and expanded with a pivoted turnbuckle (turned by hand with a screwdriver) that exerts thousands of pounds of force. This sets the riser (and new rim) tightly and precisely into old rims, even if they're worn or out of round. The risers are quick and easy to install, safer for crews due to their relatively light weight, and cost-effective compared to jackhammering and manual lifting.
The risers have an overall good track record with Jefferson County, where the risers have been used for at least 18 years.