Forensic Engineering Analysis of Residential Underdrain Design Methodologies, Performance, and Failures

Abstract

In 2014, the basement of a single-family home in a residential subdivision flooded. The homeowner’s insurance company engaged an engineer to conduct forensic investigations, which ultimately determined that the resultant flooding was caused by blockage of an underdrain system to which the home was connected. This system included a main line in the street and a lateral that connected the underdrain to the home’s foundation drain. Subsequent to this event, other homes in the subdivision reported flooding in the basements and crawlspaces. The author was engaged by the subdivision homeowners association (Common Interest Ownership Community or CIOC). The CIOC’s declarations and recorded documents contained no information regarding the existence of the underdrain system. In addition, there was no clear information about the ownership or maintenance responsibility. The author’s field investigations determined the underdrain was not constructed to the applicable minimum standards, and the developer did not provide adequate flow capacity for the number of homes served by the underdrain. The CIOC entered into litigation against the developer, and the author evaluated issues associated with the design, construction, transition, and maintenance of the underdrain system.