Inspection Results Prove 85-Year-Old Reinforced Concrete Pipe Remains in Serviceable Condition

Reinforced Concrete Pipe (RCP) is known for its inherently long service life that is unmatched by alternative products. Engineered and manufactured to get stronger with time, RCP continues to prove reliable, as it endures natural and manmade elements for many years in a variety of applications.

In the spring of 2020, Foth Infrastructure & Environment, LLC worked with the City of Sheboygan, WI, to inspect and evaluate the city’s Southside Interceptor System, comprised of 60-inch diameter RCP and concrete manholes, that was installed in the 1930s. The system stretches 9,300 linear feet alongside Lake Michigan and leads to the city’s wastewater treatment facility. In recent years, the lake’s rising water levels have begun to submerge some of the system’s manholes, exposing them to large waves and seasonal freezing. These conditions have eliminated access to several parts of the system and have made it impossible to perform routine maintenance checks and cleaning in the affected areas. With rising water levels and the system’s age in mind, city officials asked Foth to research and determine if the interceptor system remains in serviceable condition or warrants replacement.

Foth consulted County Materials’ Technical Resource Engineer Brian Kolden to discuss the condition of the system and to determine which types of inspection should be conducted. A visual inspection, using CCTV technology, was used to take a closer look at the RCP’s interior, which appeared in good condition. These results were confirmed by the astonishing findings found in the coring inspection later conducted. It was determined by several core samples that the 85-year-old RCP became stronger over time and is now outperforming current industry standards. The cores tested at 8260 psi, 7930 psi, 8960 psi, and 8110 psi. From these findings, Foth recommended the continued use of the system with armoring and minor repairs to the manholes and regular monitoring of the pipe system.

Sheboygan’s Southside Interceptor System has been in service for 85 years and continues to serve the city in excellent working condition. This study demonstrates the longevity and reliability of RCP and how these benefits result in substantial project life cycle savings.