Case Studies - January 2020

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Manhole cutter makes Hawaiian road repair more efficient

Problem / Major road construction companies like Grace Pacific maintain Hawaiian roads. These roads have an unusual number of manholes and water valve structures, which present a problem for pavers. Most paving projects in the islands require milling the road before paving. The milling and paving are much easier if the manholes and water valve structures are removed and steel plated. This process allows the milling and paving machine to operate as if the structures are not there. Not having to work around these structures makes for a much smoother roadway. 

Solution / Grace Pacific purchased the Mr. Manhole system for testing on the islands and subsequently made a second purchase. The company currently has two crews performing lowering and raising operations in conjunction with the paving crews. The crews have to maintain traffic during all operations so speed is very important. A typical lowering consists of cutting and pulling the manhole or water valve frame and placing a steel plate. The structure is GPS located, and after milling and paving, it is located and marked. The crews use the same cutting equipment to cut and restore the structure. The crews average about 25 minutes per structure to lower and about 30 minutes to raise a structure.

Result / Grace Pacific has completed 1,200 repairs to date with many more to come. 419-741-9075;

Municipality finds solution to fill gap between lining on manholes

Problem / After relining many of its old and deteriorating manholes, a Georgia municipality needed a solution to fill a 3- to 5-inch gap between the new liners and the manholes.  

Solution / Precision Fill from Prime Resins was chosen to fill this space due to its high expansion rate, the fact that it is hydro-insensitive and because its slower set time allows for a more consistent pour and prevents void pockets from forming. The project included several manholes, and each one used between 8 and 12 gallons of material. Recommended uses for Precision Fill include undersealing and stabilizing concrete slabs, compaction grouting of soils, stabilizing soils and filling voids behind pipes, walls, manholes and other structures.

Result / The process of lining and filling the annular space cost roughly a third less than tear-out and replacement. 800-321-7212;

Lining system used to rehabilitate force main

Problem / A 2-mile 27-inch force main that carries sanitary flow from a major pump station in Towson, Maryland, was incredibly deteriorated. The pump station hammer pressure produces extreme air and water pressures at the head of the flow that led to the complete structural failure of several brick structure outfall manholes. It ultimately caused the surrounding earth to enter these structures, producing major sinkholes in the area. 

Solution / The solution required trenchless rehabilitation technologies that address two priorities: providing a verified structural design for lining thickness based on third-party-verified physical strengths, as well as the ASTM F1216 standard, and the capability for immediate reinstatement of the sanitary flow to the structure. Bypass of this force main flow was not feasible, and only a two-hour shutdown was allowed at the pump station. Infrastructure rehabilitation contractor Abel Recon used the SprayWall polyurethane lining system from Sprayroq since the contractor and product were able to meet and exceed the requirements for this project.

Result / The contractor was successful in meeting the tough demands of the project while providing a long-term, verifiable, structural solution in an extremely short time window. The manholes are expected to service this densely populated area for many decades. 800-634-0504;


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