In the past, the most conventional way to replace or repair a deteriorated sanitary sewer line was to close the street and dig it up until the underground line was exposed. In the past ten years, a more cost effective and less invasive way has been developed: lining the line. During this period the Marshfield Wastewater Utility has been using this method to eliminate clearwater entry into it's sanitary sewer system. This clearwater comes from groundwater and storm water that finds its way into the sanitary sewer system through these deteriorated, leaking lines. A contractor is hired to perform this lining. A typical project will identify and line about 20,000 ft. The cost of the project is approximately $500,000. The main benefit in lining is that it eliminates the need to excavate the city street. Street excavation causes traffic disruption and may take weeks to complete. In fact, only about 10 lines or less per year could be completed utilizing this method, and it would take nearly six years to complete versus two months utilizing the lining method. The cost to excavate and replace 20,000 feet of line would be over $3,000,000. Thus, the City of Marshfield is saving sewer users over $2,500,000 in costs any year it completes these projects.
Lining begins by measuring a sock-like fabric impregnated with a resin compound.
It is measured to the exact length and size of the pipe to be lined.
This material is then inserted inside of the sanitary sewer pipe with special equipment designed to feed the pliable liner inside the full length of the pipe.
After the liner is installed for the full length of the pipe, either hot water or steam is forced inside of the liner. This accomplishes two things; first, it expands the liner to form fit the inside of the pipe; and secondly, the heat activates a chemical reaction within the resin impregnated liner to facilitate the hardening process.
Depending on the pipe size, this process cures in place for approximately 6 to 10 hours. After that time, the total length of liner has become hardened and has sealed itself to the inside of the original pipe.
Sometimes a resin odor can infiltrate into a home drain system if their drain trap is dry or empty. If this happens, the resident is asked to add water to the drain and the odor generally subsides in time. Residents may also call the Wastewater Utility at 591-2022 if they have further questions or assistance is needed.
Unfortunately, not every sanitary sewer line with defects can be lined. Some are too severely offset or have other major factors associated with them to allow them to be lined. In these cases another option must be chosen such as the street excavation method or another unique method called "pipebursting." This entails inserting a hydraulic ram into the current pipe and bursting it in place. Then another plastic pipe is pulled in behind it to create a brand new pipe without ever having to excavate the street.
These are just a few ways the Wastewater Utility is serving its users to provide the most cost effective methods to attain our mission of maintaining the sanitary sewer system to reduce clearwater intrusion and to provide clean water through its treatment processes for our environment.