Spray-Applied Structural Lining Proves Its True Worth and Properties as Part of an Unusual Manhole Rehabilitation Demonstration
Still Standing Strong
By Suzan Marie Chin Aug 20, 2014
Mishawaka, Ind. — locally known as “the Princess City” — lies along the meandering path of the beautiful St. Joseph River with a history steeped in romance and folk lore that can still be found throughout the city today.
Founded by settlers in 1831 in conjunction with the discovery of large iron ore deposits, the region was originally known as St. Joseph Iron Works. Following a period of prosperity, three other local small towns nearby were incorporated into one to become what is now modern-day Mishawaka. Today, Mishawaka occupies one of the busiest intersections in “America’s Crossroads,” making it an ideal location for transporting people and goods across the nation and home to a diverse population of more than 50,000.
Mishawaka’s sewer collection system service area includes the City of Mishawaka and portions of adjacent Clay, Penn, and Harris townships. The system covers approximately 16.92 sq miles and is comprised of an estimated 200-plus miles of storm sewer, sanitary sewer and combined sewer. The system’s pipes range in size from 8 in. in diameter for its standard sanitary sewer pipes and up to 120 in. in diameter for its largest storm sewer line.
Like any old city, Mishawaka is feeling the age of its underground infrastructure and the problems associated with it. Mishawaka Mayor Dave Wood takes the position that Mishawaka’s government and residents cannot take the City’s infrastructure for granted and, to that end, has established a proactive program for maintaining, planning, rehabilitating and constructing vital systems that contribute to the City’s public health and safety and also attract jobs and grow the local economy.
One such project was the removal and replacement of existing pipelines and associated manholes in a densely populated area of the City on Lincoln Way. HRP Construction of South Bend, Ind., was contracted as the prime contractor to perform the excavation and replacement. This project opened up a great opportunity for another local specialty contractor, Conco Spray Solutions of Indianapolis to approach Mishawaka with an unusual proposition.
Conco Spray Solutions is the certified installer of Sprayroq spray-applied polyurethane products for the Midwest region. The company believed that its product could be of great benefit to Mishawaka for its ongoing wastewater collection system rehabilitation projects. Seeing is believing and one sure way Conco could to prove to the City that its technology was a viable solution was for the City to actually see it in action.
Conco Spray Solutions was already subcontracted by HRP to rehabilitate the manholes on the project. When plans changed and it made sense for the City to remove and replace several manholes that were receiving new pipelines, Conco Spray Solutions president Jennifer Hoop approached Peggy Biggs of Lawson-Fisher Engineering, proposing that the City allow Conco to apply the Sprayroq SprayWall material to one of the scheduled manholes to be demolished as a way to demonstrate the strength and structural rehabilitation properties of the lining material.
The City agreed and Conco was allotted a manhole at the intersection of Monmore Avenue and Lincoln Way Avenue for its demonstration. The manhole selected had severe structural issues along with inflow and infiltration requiring light prep work to be performed before the lining of the old brick manhole in order fill in voids and pipe connections.
With any lining material, proper surface and preparation is the key to successful application so Conco followed a detailed protocol that included power washing of the manhole to remove all debris followed by the drying of the structure. This was followed by the application of A.W. Cook Silatech mortar to profile any voids in the brick surface substrate. Once the surface was fully prepared and dry, the Conco crews applied a 250 mls thick lining of Sprayroq SprayWall structural polyurethane to the structure.
The entire process of preparation took two hours with the lining application completed in a single pass in one hour with a return to service immediately after the invert was sprayed. The City was impressed with the speed and application of the product and its ability to provide huge savings in the quick return to service and true structural properties. Mishawaka recognized its viability for future projects for rehabilitation and protection of newly installed structures to extend asset life.
What no one counted on was what occurred during the demolition.
A few months after Conco had completed the structural rehabilitation of the manhole structure, the HRP construction crews arrived onsite to perform the scheduled demolition. “We had total confidence in the strength of the Spraywall lining material but no one expected that it would be able to withstand the punishment of an excavator,” says Hoop. “The day of excavation definitely impressed everyone present.”
In addition to Hoop and Conco operations manager Barry Hubbard, representatives from HRP Construction, Lawson-Fisher Engineers and the the City of Mishawaka Engineering Department were on hand to witness a most unusual and memorable manhole demolition. Hoop had video and photo documented all steps of the original installation of the lining on the manhole and wanted to follow up during the demolition. The images shown were taken during the initial demo installation and throughout the follow up demolition process. The operating weight of the HRP excavator used for the demolition was approximately 65,000 lbs with a ground pressure of around 8.82 psi and bucket break out pressure of 39,000 psi. The lined manhole was subjected to multiple hits from the excavator and even after this, with its brick structure crumbling all around, the lining material inside was still standing strong.
The Sprayroq lining certainly proved itself to be a true structural rehabilitation solution for underground infrastructure this day.
Suzan Marie Chin is owner of Creative Raven, a Div. of Thompson Data Systems, Ltd., based in the Greater Los Angeles area.