Watermain infrastructure is often overlooked by the public unless there is an emergency like a watermain break or fire hydrant without enough pressure. Many northeastern cities that experienced growth in the first half of the 20th century are now plagued with aging systems.
The cost of 24/7 operation and maintenance of water systems increases annually. In many towns and cities, municipalities are supporting systems that are designed to supply more than the current population requires. Existing cast iron watermains can become clogged progressively over time due to the buildup of iron oxide. Low water pressure and volume are a result of the clogging. Managing system maintenance and repair/reconstruction efficiently is essential to ensure financial success.
Conventional watermain replacement consists of constructing a parallel watermain to the existing watermain. Full reconstruction of the watermain requires full length excavation for installation and associated trench restoration. The trench restoration, especially in city projects with tighter right-of-ways usually requires expensive pavement or sidewalk restoration. Final restoration of the trench is typically delayed until after the watermain is constructed, disinfected, and tested.
Cleaning and Relining as an Alternative to Full Replacement
As an alternative to complete reconstruction, which disrupts the entire neighborhood’s daily life with roadway restriction and closed sidewalks during the full duration of construction, cleaning and lining the existing watermain can be a viable and cost-effective option to address these issues.
The structural soundness of the watermain is determined by the accurate record keeping of breaks and maintenance to the existing watermain. Once deemed structurally sound, the cleaning process mechanically removes the tuberculated buildup of iron oxide.
Cleaning is facilitated by excavation of access ports throughout the project area. The access locations are typically spaced every 600 to 800 feet and consist of approximately 20 to 30 feet of disturbance centered around each access port. The cleaning equipment is inserted into the system at the access ports and the watermain is mechanically “cleaned” and flushed between access ports.
After cleaning, the relining equipment utilizes the same access ports and re-establishes the cement lining within the watermain. The access ports are “closed” with new waterline installation and the smaller disturbed area is restored to pre-construction conditions. This process rejuvenates the watermain, extending its service life while improving service pressure and volume.
Using the cleaning and relining method reduces the amount of watermain to be replaced by 90%. Because cleaning and relining takes the existing watermain temporarily out of service, temporary water service must be established while the watermain is being rejuvenated. With the successful completion of a project, the cleaning and relining effectively extends service life of the existing watermain with increased area-wide pressures on a shorter, less disruptive schedule.
