What is flood grouting?

Flood grouting is a two-step process that simultaneously seals large portions of a structurally sound sewer system (Grade 3 and better) subject to joint leakage and minor cracking.

It was included in the July 2006 EPA publication Emerging Technologies for Conveyance Systems (832-R-06-004) and the Water Environment Research Foundation’s 2009 Methods for Cost-Effective Rehabilitation of Private Lateral Sewers (Project No. 02-CTS-5).

The International Society for Trenchless Technology describes the process like this:

  • The main is cleaned and desilted by flushing with a high-pressure water jet.
  • Main and laterals are sealed by pneumatic rubber plugs.
  • The sewer is filled with the first of two chemical solutions from a manhole or other access point. Hydrostatic pressure forces the solution into the soil, surrounding the pipe at defect points.
  • The first solution is pumped out, leaving the defect and nearby soil saturated.
  • The pipe is refilled with a second chemical solution that reacts with the first to form a concrete-like matrix that binds the soil and consolidates the ground around defects. When the chemical reaction stops, the second solution is pumped out.
  • The pipe is flushed, seals removed, and returned to service.

Sanipor, the product that Seattle Public Utilities used, is not chemical grout. Rather, the process uses soluble silicates made of sand and potassium that are melted into an amorphous glass that can be dissolved in water.

This was not the first U.S. use of Sanipor:

  • The City of St. Petersburg Beach, Fla., spent $80,000 in 1992 on vitrified clay pipe placed on an island community. CCTV inspection a decade later showed no seawater infiltration.
  • The City of Mequon, Wis., reported an almost 100% drop in infiltration after a June 2007 pilot project.

For more information on these projects, including preconditions, visit here.

For lessons learned, such as side sewer plugs being the Achilles heel of the process, visit here.

—Stephanie Johnston

Cities test business case software

A patent-pending cloud-based plug-in for computer-aided design (CAD) tools is to be beta-tested on stormwater projects for the City of Tucson and Pima County, Ariz.

Impact Infrastructure LLC’s AutoCASE automates business case analysis for infrastructure and public building projects, providing a critical advantage in competition for merit-based public funding and securing private impact capital. An off-the-shelf solution that doesn’t entail the expense of a customized economic assessment, the software deploys risk-adjusted social and environmental metrics to assess environmental, social, and governance (ESG) metrics.

“Combined with a joint marketing agreement with Autodesk, AutoCASE can become the evaluation standard for the infrastructure finance and delivery,” says Impact Infrastructure CEO John Williams.