Overview

The next time you drive over a manhole, you just might be driving over recycled plastic. One Minnesota company, Ladtech, Inc., manufactures molded plastic manhole adjusting rings - the part used to raise manhole covers up to street level after road surfacing. These 100% plastic rings can replace traditional non-recycled concrete rings. As many as 50 milk jugs and detergent bottles are recycled to make a single 27-inch plastic ring, and the product can last up to three times longer than concrete.

Performance

In tests for impact resistance and compressive strength, recycled plastic rings have performed similarly to concrete.

In other important ways, the plastic rings outperform their traditional counterparts. The recycled plastic rings weigh just over five pounds, while conventional concrete rings weigh about 85 pounds. Because the plastic rings can easily be handled by one person, they alleviate the need for heavy lifting equipment. This benefit can reduce the time and cost needed for installation and lower the risk of employee injury.

More durable than concrete rings, recycled plastic rings typically are not prone to cracks, breaks, or corrosion caused by exposure to salt. In practice, maintenance schedules for city, county, and state road repairs vary widely; some overlay roads every three years while others may wait up to 15 years. No matter when maintenance is performed, concrete adjusting rings usually need replacing. Although the actual life cycle of the plastic rings is still to be determined, the manufacturer provides a 15-year warranty. This warranty is in addition to their normal "no charge" replacement for any rings found broken prior to installation.

Recognizing the advanced quality of this product, the Minnesota Department of Transportation (Mn/DOT) in 1996 approved plastic rings for statewide use. Refer to Appendix E for Mn/DOT's technical memo on plastic adjusting rings.

Today, many Minnesota cities use Ladtech's post-consumer HDPE manhole adjusting rings in their street rehab projects, including Apple Valley, Brooklyn Center, Brooklyn Park, Duluth, Fergus Falls, Forest Lake, Woodbury, and Wyoming.

Availability

Recycled plastic rings are readily available through a limited number of distributors as well as directly from the manufacturer.

Cost

The initial price of the recycled plastic ring is about three times that of the concrete ring. However, the cost of installing and maintaining the recycled plastic product is likely to be lower. Unlike concrete, plastic rings rarely break during shipping and installation. The plastic rings are also durable and much lighter, requiring no heavy equipment to install. Furthermore, the recycled plastic will not corrode over time, greatly reducing maintenance and replacement costs.

Specifications

Despite the fact that recycled plastic rings are more durable and long-lasting than concrete rings, contractors typically use concrete rings in road projects because the plastic product is relatively new to the industry and tends to cost more initially than concrete. To ensure that contractors use the longer-lasting rings made from recycled plastic, consider using the following construction job specification:

"In lieu of concrete adjusting rings, all manholes shall utilize plastic adjusting rings made from post-consumer recycled content."

Vendors

Ladtech, Inc. is the only known manufacturer of post-consumer manhole adjusting rings in the Midwest. For a list of Minnesota distributors, contact the manufacturer or visit its web site.

Ladtech, Inc.
Contact: Dwight Wiedrich
Lino Lakes, MN
651/415-1252 or
877/235-7464 (toll free)
fax: 651/415-1090
Products: Molded plastic manhole adjusting rings made with 100% HDPE plastic. Post-consumer recycled content varies with product size and may be as high as 100%.

Success Stories

Sources

"The Resource," Volume 8, Number 3
Minnesota Office of Environmental Assistance
Summer 1998