Important for sewer, stormwater, or water retention systems, manholes give workers access to the lines for maintenance or servicing. The 84-inch flattop manhole is one of the largest we manufacture at Columbia Precast Products, ideal for subdivisions, along city streets, or at business parks with large parking lots.

The base section can be up to eight-feet deep while additional sections can be created up to eight-feet deep. The top is a foot thick with a 25-inch opening for a manhole cover or a custom opening for a Hatch Door. These sections are sealed with mastic or rubber gaskets for a water-tight finish. Grade rings are available in two, three, four, and six-inch thicknesses.

For a closer look at the 84-inch flattop manhole, click here for a downloadable .pdf or continue down the page.

Green Products for Green Bids

In the Pacific Northwest, we don’t take the natural beauty for granted. We enjoy the coast, the mountains, the rivers, and the forests for any number of outdoor activities. When we built our Woodland facility in 2015, we wanted to do our part to preserve the environment – both in what we made and how we made it.

Columbia Precast Products is proud to be the first buried infrastructure plant in the United States to earn SMaRT certification. Why should that matter to you? Many public projects require environmentally sound processes, products, and materials from contractors when submitting bids. With our products, you’ll be able to check that box.

Concrete itself is a “green” product because it’s made from natural and raw materials. What our clients really appreciate is the fact that precast concrete offers the longest-lasting sewer, water, utility, and stormwater systems on the market. Many of our products are engineered to last 100 years.

That means less repair, replacement, and material in a landfill. It goes beyond that, too. Our controlled facility allows us to recycle and reuse wastewater or concrete that doesn’t meet our standards or jurisdictional requirements. And we choose our vendors and partners based on a shared belief system as well as location to cut down on emissions during delivery.

Stay On Schedule

Although poured in place manholes are strong enough, a lot more time and effort are needed for installation. Setting up forms, mixing the concrete, and pouring can take a day or two. Waiting for the concrete to strengthen may take up to a week. Then the forms need to be removed before tying it into the system.

Precast manholes are ready when you are, manufactured well before installation. The weather plays no part in the installation process – precast concrete can be installed in hot, cold, or rainy conditions. This means when excavation is complete, the manholes can be installed and backfilled in a day.

If you have an upcoming project that has a need for manholes, contact Columbia Precast Products to see how we can help. Built to last a century, easy to install, and satisfying all environmental requirements, our precast manholes will save time on the site and meet all WSDOT and ODOT specifications.

Click to download as a PDF.