Getting manholes on grade with a resurfaced street is often a difficult task. Heavy concrete risers are often used to build up the chimney so the cover and its frame can be raised, but those rings are cumbersome and require heavy machinery to install.

As an alternative, Cretex Specialty Products offers the PRO-RING system, a series of lightweight expanded polypropylene (EPP) risers. These rings come in various shapes and sizes, including round, square and rectangular. The round rings are available in a variety of inner and outer diameter configurations, the latest version with an inner diameter of 24 inches and an outer diameter of 34 inches. According to Cretex general manager Lee Haessig, the new size is a fit for several Midwestern states.

“We were seeing municipalities in Illinois and eastern Iowa with this-size manhole cone, so it made sense for us to offer our riser system in that size as well,” he says.

The key to the riser’s ease of use is its construction material, engineered plastic foam that is lightweight and has a very high strength-to-weight ratio. It withstands repeated impacts without significant damage, resists water, chemicals and most oils, and performs in temperature extremes from -22 to 230 degrees F.

One man can install the PRO-RING system in just minutes to within a quarter-inch of finished grade, and they are watertight. Where concrete rings break and may cause injury, the PRO-RING eliminates the hazard, helping minimize the risk of injury. The system is also designed to dramatically speed up manhole installation and repair time.

“When you factor in less weight for hauling, ease of install and durability, this is a system that is going to be more cost-effective in the long term,” says Haessig. “This is a durable system with a 50-year design life.”

Haessig notes that while it can take up to four men to lift some concrete grade rings, a 6-inch-thick PRO-RING unit weighs 14 pounds. One man can install the system in a few minutes, allowing a site to be closed in one day at 20 to 30 percent reduced cost versus conventional methods, according to the company. No water, sand, mortar or bricks are needed.

Haessig pointed out that while the rings are intended for use in municipal water and sewer systems, they are a fit for other utility uses, and have even been utilized as septic system risers.

“Basically, they are going to be a good fit for anyone working with an underground structure with manhole-type access.” 800/345-3764; www.cretexseals.com.