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Flood Grouting for Infiltration Reduction on Private Side Sewers (WERF Report INFR5R11)
Citation:
Burke, M., M. Merrill, R. Jacobsen, AND H. Twenter. Flood Grouting for Infiltration Reduction on Private Side Sewers (WERF Report INFR5R11). Water Environment Research Foundation, Alexandria, VA, 2013.
Impact/Purpose:
This report describes in detail how to conduct a flood grouting project. Actual lessons-learned from completing a flood grouting project are presented. The report describes how to calculate the effectiveness of the project. A description is included of the Seattle Public Utilities’ business case methodologies for approving projects and of the public outreach campaign used to gain public acceptance.
Description:
The sewers in Seattle’s Broadview neighborhood, built in the 1950s, experience significant inflow and infiltration. Intense wet weather events have resulted in sewer overflows into private residences and the environment and previous work indicates that the majority of this excess flow comes from infiltration. As a result, an infiltration reduction project was investigated to reduce overflows. To reduce infiltration and achieve maximum success, all components of the sewer system – mainlines, maintenance holes, and private side sewers – have to be addressed. Seattle Public Utilities determined through a business case that to reduce infiltration, flood grouting was the most cost-effective, least-disruptive methodology. Flood grouting involves applying two chemicals in separate steps to treat an entire section of the sewer system between two maintenance holes, including the side sewers. The segment is filled completely to the maintenance hole rim and utilizes hydrostatic pressure by the chemical fluid to apply the grout to the system. To determine the success of the project, flow meters were installed in the system to document before and after conditions for modeling analysis. The effectiveness of this approach at reducing infiltration compared to the cost, the challenges associated with working on private property, and lessons learned are documented in this report. [NOTE: The link below connects to a WERF site where the Final Report can be downloaded for free, after registering at the WERF site. To view the WERF registration link, which is on the WERF home page (www.werf.org), it may be necessary to move the page so the top right corner is visible. For some projects the Executive Summary is available and can be downloaded for free without registering on the WERF site.]
