Infiltration and inflow repairs on Nethery Street

At the December 18 Henderson City Council meeting, Assistant City Manager Mark Warren reported that infiltration and inflow repairs are being conducted on the Nethery Street sewer.

The work, which consists of cleaning and repairing, has resulting in the discovery of “serious issues”.

According to Warren, a smoke test has revealed substantial storm water infiltration into the system.

In smoke testing, smoke is created using either a smoke bomb or liquid smoke. Smoke bombs are lit and placed on a grate or in a holder on top of a fan or liquid smoke is injected into a fan via a heating chamber. The fans create a pressure differential that forces the artificial smoke into the sewer at a pressure just above atmospheric. With properly installed plumbing the traps will prevent the smoke from entering a house and redirected it out the plumbing vents.

Defective plumbing systems or dry traps will allow smoke to enter the inside of a house.

The area around the section being tested is searched for smoke plumes. Plumes coming from plumbing vents or the interface between the fan shroud and manhole rim are normal. However, smoke plumes outside of the manhole rim are not. Plumes are marked, usually with flags, and defects are noted using measurements from stationary landmarks like the corners of houses. The plumes or markers may also be photographed.

“Infiltration” occurs when groundwater enters a sewer system through broken pipes, defective pipe joints, or illegal connections of foundation drains. “Inflow” is surface runoff that enters a sewer system through manhole covers, exposed broken pipe and defective pipe joints, cross connections between storm sewers and sanitary sewers, and illegal connection of roof leaders, cellar drains, yard drains, or catch basins.

Virtually every sewer system will have some infiltration or inflow.

The Assistant City Manager reported to the council that all repairs are being documented, and that an estimate of infiltration and inflow taken out of the system was being prepared.

As a result of the discussion, Henderson Mayor Clem Seifert noted that a fact sheet on water concerns may need to be added to the list of legislative concerns which is going out to Henderson’s federal delegation. He stated that the water system might have a better chance of obtaining federal money because it is regional rather than local.

Henderson City Council member Elissa Yount advised the Mayor to make sure that the fact sheet came from the Kerr Lake Regional Water System rather than the City of Henderson.