On the level: New manholes keep Kansas City streets smoother

Manhole cover
Manhole cover

Traditionally designed manhole covers or other street castings can contribute to problems such as bumpier streets, affecting the quality of life in cities for pedestrians, cyclists and vehicle occupants. The SELFLEVEL® access assembly by EJ is an innovative solution, with easy installation, providing infrastructure coverage that remains aligned with the surface over time. Its unique design allows a range of movement and continuous alignment with the finished road surface.

The city of Kansas City, Mo., has the SELFLEVEL specified to be used whenever an existing manhole is being repaired, as part of its Smooth Streets Initiative. Likewise, any and all other utilities with a manhole in the street are required to do the same, including Kansas City Power & Light, AT&T, Time-Warner (fiber-optic cable) and Qwest/CenturyLink. The product is viewed as meeting two key criteria of the initiative: it provides a solution for the effects of heavyweight vehicles in traffic, as well as for varying pavement slope resulting from the crown of the road.

As conditions of the pavement change or degrade, traditional castings may be observed to rest significantly higher or lower than the street surface. Causal factors can include heaving/uplift due to ground frost, settling of the entire manhole structure, site deterioration, cracking of concrete or asphalt and inclined street surfaces. The SELFLEVEL's unique configuration consists of a below-ground guide frame and an upper frame that allows for movement in position, so that a cover or grate will "float" (i.e., remain level with the surface).

The city of Kansas City performed an initial test installation in 2009, and the first permanent units were installed in fall 2010. Completion is ongoing, specified for use whenever an existing manhole is to be repaired or replaced. Although highway use is not unusual, the most common application for the product is in a metropolitan area, and in this case many are installed in the urban core of Kansas City.

The product responds well to heavy traffic. Many are located in Kansas City bus lanes, with no failures reported. They meet AASHTO loading, as would be expected for heavy traffic locations. These access assemblies work well in areas with wide climactic variability and have common use in extreme cold regions such as Canada or North Dakota, proving very suitable for winter-weather climates where they are subject to snow, snowplows and salt. Temperatures in the Kansas City area range from -20 to 105°F.

Cost-benefits are based not only on road life and pavement integrity but also labor and material for a minimum of one to possibly three manhole adjustments with future pavement overlays/restoration. The longevity of the solution should be at least as long as the pavement service life. If properly installed, the casting should exceed the expected life of the roadway surface. One can expect this type of casting to last as long as traditional castings.

Combined with SELFLEVEL, the optional INFRA-RISER® reduces traffic vibration, further prolonging life of underground structures and surrounding pavement.