The1950s-era concrete pipe sanitary sewer system in Seattle’s Broadview neighborhood experiences significant wet weather inflow and infiltration. Extreme wet weather events have resulted in sewer overflows into private residences and the environment. Previous work indicates that the majority of flow during wet weather is infiltration. For an infiltration reduction project to achieve maximum success, all components of the sewer system—mainlines, maintenance holes, and private side sewers—have to be addressed. An alternative analysis indicated that infiltration reduction using flood grouting, as provided by Sanipor®, was the most cost-effective, least disruptive methodology. Flood grouting involves isolating and treating an entire section of the sewer system between two maintenance holes, including the side sewers, with two chemicals in separate steps. The segment is filled completely to the rim and utilizes hydrostatic pressure by the chemical fluid to apply the grout to portions of the system that are prone to leakage. Because of this technique, there is little risk that potential infiltration sources will be missed. To determine the success of the project, flow meters have been installed in the system to document before and after conditions for modeling analysis. Infiltration removal rates, costs, challenges associated with working on private property, and lessons learned from this flood grouting project are documented in this paper. Flood grouting has been used in limited applications in the U.S., but never in the Pacific Northwest. This is the largest flood grouting project in the U.S. to date.