The sewer rehabilitation work required to comply with the AO cannot be completed by City crews due to lack of manpower, equipment and expertise in some of the type of repairs. Therefore, construction contracts are being designed by several engineering firms with the projects being completed by sewer construction contractors.
In accordance with TDEC State Revolving Fund (SRF) loan program requirements, the contracting process includes review of the project by TDEC, advertising the project in the newspaper, a mandatory prebid conference, submittal by formal sealed bid with a public opening, approval of the project by City Council, approval of the bid process by TDEC, and a preconstruction meeting attended by a TDEC representative. The entire process takes approximately twelve to fourteen weeks to complete.
Methods of repair the sewer system include:
- Pipe Bursting – Pipe bursting is a trenchless method of replacing buried pipelines without the need for a traditional construction trench.
- Pipe Lining – Pipe lining sewer repairs were introduced as a way to eliminate the need for deconstruction when fixing plumbing issues.
- Cured-in-Place — CIPP (Cured-In-Place Pipe) is a process where a liner is inserted into a pipe impregnated with a thermosetting resin, which is expanded and cured to form a tight-fitting liner within the host pipe, a pipe within a pipe.
- Point Repair – Point Repair is a cost saving process of lining only the areas that require repair versus lining the entire length of pipeline.
New Technology for Sewer Line Inspection
Continuing our task to find methods of being more cost efficient in maintaining the City’s sewer system, the Public Works Department purchased a new device called the Sewer Line Rapid Assessment Tool (SL-RAT). The SL-RAT is specifically designed as a portable, cost effective tool comprised of two components, the transmitter and the receiver. The SL-RAT helps prioritize maintenance operations based on a rapid assessment of the conditions within sewer line segments.
The transmitter sits on top of an open manhole and the receiver sits on top of an open adjacent manhole. It uses sound waves instead of sight to determine if a sewer line is open or to what degree a blockage may exist. The transmitter emits a repeating series of tones similar to a musical scale to the receiver and in open areas can be heard over long distances. The tones emitted by the machine, while harmless, are low enough in frequency that residents nearby may be able to feel them.
With this new technology, Public Works will be able to greatly reduce the need for cleaning and videoing each and every sewer line segment and concentrate more on the lines that were discovered with the SL-RAT to be blocked to some degree, indicating the need for further maintenance and possibly repairs. This will allow the crews to inspect the system quicker and more efficiently.
Click the link of the YouTube link of the SL-Rat from the Jack Doheny Companies demonstrating the detailed operation of the SL Rat Sewer Line Rapid Assessment Tool
If you have any questions, please call 425-1875.