Sanitary Sewer Evaluation Survey – Subbasins A and E

The City of Sandwich is continuing the investigation of the sanitary sewer collection system to identify the defects contributing to excessive inflow and infiltration. During heavy rain events and snowmelt, the sanitary sewer collection system is often overwhelmed by this extra water entering the system through the pipe and manhole defects. The extra water exceeds the capacity of the system, and in some cases, contributes to basement backups. Further, the extra water is conveyed to the wastewater treatment plant where it is treated at an extra cost to the sewer users.

The City has focused on two areas (“subbasins”) that were shown to have inflow issues for this survey: (MAP)
- Subbasin A is generally the area from Prairie View Elementary School east to Valley West Hospital and down to W. Crofoot Street. Subbasin A was characterized as having “excessive inflow issues”.
- Subbasin E is generally the area from E. Pleasant Avenue/Dekalb Street southerly to Center Street and from Eddy Street easterly to parts of Elm Street.

July 1, 2019 through July 9, 2019 – Sanitary Manhole Investigations
The City has contracted with Engineering Enterprises, Inc. and Midwest Water Group Inc. / RMS Utility Services of McHenry, IL to perform investigations of 125 sanitary manholes. Midwest/RMS will be using a camera system with 360º imaging to televise and catalog structural features, piping arrangements, depths, deficiencies, and defects of the interior of the manholes. Information gathered from this camera work will be used to create the capital improvement plans for funding the repairs and replacements of the sanitary manholes.
Letters were recently mailed to residents and business owners that are located in Subbasins A and E. (Copy of Letter) (Affected Addresses) The manhole investigation work will not impact the sanitary sewer flows and there will be no disruption to sanitary sewer service. Midwest/RMS employees will need access to all of the sanitary sewer manholes to complete the work – including ones located on private property. Individual manhole inspections will generally take less than 30 minutes. On occasion, Midwest/RMS will need to stage the camera truck temporarily within a driveway.

July 22, 2019 through July 26, 2019 – Smoke Testing of the Sanitary Sewer Pipes
The City has contracted with Engineering Enterprises, Inc. and Midwest Water Group Inc. / RMS Utility Services of McHenry, IL to perform smoke testing of approximately 36,000 linear feet of sanitary sewer main pipe (14,000 feet of sanitary sewer service pipe). Midwest will be using a non-toxic liquid smoke safe for people and pets that is air-forced into the sanitary sewer mains at the sanitary sewer manholes. The liquid smoke is similar to what is used in haunted houses and special effects. Sections of pipe between manholes are blocked off while the liquid smoke is air-forced into the sanitary sewer system.
During testing, the air-forced smoke will exit the sanitary sewer system through the defects in the pipes that allow inflow and infiltration into the system. The smoke will be visible coming up from the ground, through roof vents, building foundations, storm sewer catch basins, cleanouts, downspouts, or manhole covers. The smoke cannot enter the interior of a building when the drainage systems are properly plumbed and vented with water in the drain traps.
Letters will be mailed to the buildings to further discuss the smoke testing. Door hangers will be placed on the front doors of the affected buildings and yard signage will be placed throughout the general area a few days prior to smoke testing.

If you have any questions regarding the upcoming sanitary manhole inspections and smoke testing, please call Thomas R. Horak, Director of Public Works at 815.786.8802.