District of North Vancouver Rehabs Manhole Grade Rings
The District of North Vancouver (DNV) faced a problem in the spring of 2015 when it was tasked with the rehabilitation of existing manhole grade rings that were located off-road in easements. The DNV had a list of approximately 50 manholes that required attention. Using a traditional concrete grade ring system made this project look daunting for the DNV, as the manholes were spread out amongst remote locations.
Matt Pirrotta from Martech Inc. (representative for Cretex Specialty Products) met with DNV Utilities Supervisor Chris Alexander to discuss the advantages of using the Cretex PRO-RING™ Manhole & Catch Basin Adjustment System over traditional methods. Alexander saw an opportunity for the product and quickly gave the go-ahead for a demonstration on one of the many manholes that required rehabilitation. The manhole was located in a residential area, tucked away in the backyard of a residence.
The PRO-RING system is manufactured from expanded polypropylene (EPP), an engineered plastic that is lightweight, has a very high strength-to-weight ratio and is ideal for the harsh conditions found in sewer manholes and stormwater catch basins. It meets AASHTO M306 for HS-20 and HS-25 traffic loading to withstand repeated impacts without damage and is resistant to many chemicals. A traditional concrete grade ring would require up to four people or equipment to lift, while a 6-inch-thick PRO-RING unit weighs 14 pounds - one person can install the system in a few minutes.
The system consists of three types of rings: grade rings, finish rings and angle rings. Grade rings are used to raise the manhole to within an inch or two of the final elevation. A finish ring is applied in the final layer between the grade rings and the manhole frame casting. Angle rings are used to match sloping roadways or when the surface surrounding the manhole is sloped. The entire ring system is assembled and bonded together in minutes using a construction adhesive/sealant to create a watertight, testable system. PRO-RING is available in round, square and rectangular shapes and is backed by a 25-year material warranty.
The system proved to be effective in this application, allowing crew members to easily handle the rings with little risk of injury. Aside from the obvious ergonomic benefit that the system provides, the DNV experienced the following positive results:
- Less time spent on job site
- Less material required on job site
- Smaller crew required on site
The DNV was pleased with the results and decided to go with the PRO-RING system instead of using traditional concrete. The key here was using a system that was ergonomically beneficial due to remote access of off-road manholes. In addition, they are now using a system that has a design life of 50 years, which will far outlast traditional concrete. The DNV will be completing the remainder of their project in spring and summer of 2016.
Cretex Specialty Products is exhibiting at WEFTEC.16, Booth 1319. For more information, visit www.cretexseals.com.