Real projects. Real results. The Manhole Recovery case study library documents rehabilitation programs from municipalities and utilities across North America — capturing the challenges, decisions, technologies, and outcomes that other practitioners can learn from.

Featured Case Studies

City of Columbus, OH: 847 Manholes Rehabilitated in 18 Months

System size: 2,400+ manholes | Project budget: $4.2 million | Primary method: Spray-applied polyurea + chimney seals

Columbus Division of Sewers and Drains identified a critical rehabilitation backlog through a system-wide MACP inspection program. Rather than addressing manholes reactively, they developed a programmatic approach — grouping manholes by neighborhood and contractor access to achieve economies of scale.

Key results: 847 manholes rehabilitated over 18 months at an average unit cost of $4,960. System flow monitoring showed a 12% reduction in wet weather peak flow in the rehabilitated basins, translating to roughly $340,000 in annual treatment cost avoidance. The program was funded through a combination of CWSRF financing and existing capital budget.

Lesson learned: “Mobilization costs are everything in a polyurea lining program. Grouping jobs geographically and scheduling crews for consecutive days in the same area drove our unit costs down by 22% compared to scattered scheduling.” — Division Project Manager

Harris County, TX: Polyurea Lining in Extreme H2S Environments

System size: 180 manholes (targeted program) | Project budget: $1.1 million | Primary method: High-build polyurea with epoxy primer

Harris County Flood Control District manages a collection system in a hot, low-gradient environment with extremely high H2S levels — measured at 50–200 ppm continuously in problem areas. Previous cementitious coating attempts had failed within 3–5 years due to sulfuric acid attack.

A high-build polyurea system (250-mil minimum applied thickness with a moisture-tolerant epoxy primer) was specified. Five-year performance monitoring shows zero coating failures and measurable reduction in MACP condition grade deterioration rate compared to unlined comparable manholes in the same environment.

Lesson learned: Surface preparation quality and applicator certification matter more in high-H2S environments. The county now requires polyurea applicator certification with documented experience in H2S environments as a contract requirement.

City of Portland, OR: Combined Sewer Overflow Reduction Through Manhole Sealing

System size: 310 manholes (Phase 1) | Project budget: $890,000 | Primary method: Chimney seals + watertight frame and cover replacement

Portland’s combined sewer system is subject to both state and federal requirements to reduce CSO volumes. A flow monitoring study identified three basins where manhole inflow was contributing a disproportionate share of wet-weather flow. Rather than expensive pipe relining, the project focused exclusively on the manhole-surface interface.

Results: 310 manholes received chimney seals and 87 received new watertight frames and covers. Wet-weather flow monitoring showed an 18% reduction in peak flow in the targeted basins — exceeding projections — at a project cost of $2,871 per manhole, well below the estimated cost of equivalent pipe rehabilitation.

Rural Water District, Nebraska: Cost-Effective Rehab on a Constrained Budget

System size: 94 manholes total | Project budget: $185,000 (includes USDA RD grant) | Primary method: Prioritized approach: chimney seals (all), polyurea (top 25 priority)

Small rural systems face the same deterioration challenges as large urban systems but with far fewer resources. This Nebraska rural water district worked with Manhole Recovery community members to develop a prioritized approach: address every manhole with a chimney seal first (highest ROI, lowest cost), then apply polyurea lining to the 25 manholes with the highest MACP scores.

Total project cost was $185,000, with $140,000 funded through a USDA Rural Development grant (75% grant rate based on community income levels). First-year flow monitoring shows a 9% reduction in system-wide I/I — meaningful for a system of this size.

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More Resources

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