Rehabilitation of 23 Manholes at University Park, Sarasota, Florida

A comprehensive video inspection of the 409 manholes in University Park identified a number of deteriorated manholes and a five-year plan was put in place to repair approximately 100 of them.

With its mature landscape and sprawling natural beauty, University Park is the premier award-winning, resident-owned community located in Sarasota, Florida.

The community’s wastewater infrastructure was built in the mid-1990s and has been rehabilitated with a variety of liner systems since the 2000s and onward after an attack by H2S biogenic corrosion causing deterioration of the Portland cement.

The 23 manholes in the worst condition showed that the previous liner product was failing to offer protection against severe H2S corrosion and groundwater infiltration into the sewer system. The repair of these 23 manholes was scheduled for the summer of 2021. This was the first time a manhole repair program of this type had been performed in the University Park community.

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Condition of manhole prior to repair

The owners were looking for a solution that would restore structural integrity, and provide a rock-solid barrier to infiltration together with proven biogenic corrosion resistance to protect the assets for generations to come. In addition, ease of application and a strong manufacturer’s warranty were key selection criteria.

The list of recommended manhole repair vendors from Manatee County, the City of Naples, and Sarasota County was reviewed, RFQ’s were sent out, and three proposals were shortlisted to be evaluated in further detail. One proposal was a urea based rubberized coating, another proposal was a type of cement, and the third proposal was SewperCoat with the bid presented by Maxx Environmental.

After conducting a detailed literature review of the three different techniques being proposed Maxx Environmental was selected as the contractor and SewperCoat was selected as the manhole repair solution.

“Our research identified a considerable amount of favorable information regarding the resistance of SewperCoat to H2S biogenic corrosion in a wide range of applications and conditions and that it was the easiest to apply in terms of required dryness, cleaning etc.” said Tom Christopher, president of the University Park Community Association.

Manhole after repair

SewperCoat is a 100 percent calcium aluminate mortar (both cement and aggregate system); 100 percent of the product has the ability to neutralize acid and inhibit bacterial activity. SewperCoat can be applied in a live sewer environment, offers rapid return to service, and brings 30 years of proven performance protecting wastewater infrastructure assets against H2S biogenic corrosion.

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The manufacturer’s warranty was a significant factor in selecting SewperCoat for the University Park community. The warranties from the other vendors were backed only by the service vendors’ assets and both companies were relatively small. Maxx Environmental’s warranty is provided directly by Imerys, a large multinational company with more than 40 years being in business in the United States.

At the owner’s request, Imerys sent two factory representatives to view the application of SewperCoat, to provide traceability to the particular cement bag used, and to explain the manufacturer’s warranty in detail.

MAXX Environmental Crew at University Park.

The application was performed by Maxx Environmental, an approved SewperCoat applicator specializing in the rehabilitation of aging sewer and drainage infrastructure throughout the state of Florida and southeast United States.

A week before the project started Maxx Environmental sat down with the owners for an extensive readiness review meeting where the details of the project were laid out. Prior to repair, each manhole was sandblasted, all debris from the sandblasting were cleaned out, then the manhole was pressure washed to remove any leftover debris and the substrate was pre-soaked before application. H2S gas levels were checked and ventilation provided via vacuum style forced air. SewperCoat, manufactured by Imerys, was applied using wet spray at a low-pressure, then lightly flat troweled and wet brushed to give SewperCoat its unique finish.

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SewperCoat was mixed at a ratio of approximately 1.3 gallons of water per 65-lb bag (~14 percent by weight of dry mortar). This mixture utilized the hydraulics of the machine to pump the SewperCoat through a progressive cavity type pump. One coat of SewperCoat was applied to the manholes with a minimum ½-in. nominal thickness. Maxx Environmental personnel applied the Sewpercoat by hand and it was smoothly handled with a limited amount of cement “debris.” The application thickness was verified by “direct depth measurements” throughout the area coated by the cement.

The manholes were inspected by the owners after six months of service and the 23 repaired manholes are in excellent condition.

Each manhole was returned to service within two hours. The repair of 23 manholes was completed over a seven-day period.

The manholes were inspected by the owners after six months of service and the 23 repaired manholes repaired are in excellent condition. Prior to the inspection, a gas meter was lowered into the chamber and the H2S gas reading was registered. The manhole surface was checked for any cracking or signs of deterioration. The surface was struck with a manhole cover pick confirming the visual inspection. The SewperCoat is rock solid after six months in these 23 structures. The owners and residents were completely satisfied with the performance of SewperCoat and with the knowledge and professionalism of the team at Maxx Environmental.

The owners plan to visually inspect all 23 repaired manholes annually for the foreseeable future. The owner also plans to use SewperCoat for future manhole and other wastewater infrastructure repairs within the University Park community to extend the life of assets for decades to come.

Joseph Talley and Clair Brown are with Imerys.