
Lateral Rehabilitation for the Greater Peoria Sanitary District
As part of its 75-year sewer rehabilitation goal, the Greater Peoria Sanitary District (GPSD) is allocating funding to grow its lateral rehabilitation program.
GPSD serves Peoria, Peoria Heights, Bartonville, West Peoria and Bellevue, plus adjacent unincorporate areas located in Central Illinois.
Early Focus on Mainline Pipes
In the last 30 years, municipalities and system owners have invested heavily in projects that solely focused their efforts on the rehabilitation of mainline pipes. As the industry matured, time and experience have a way of identifying the need for a holistic mindset.
When sewer systems were first installed, the mainlines were often installed first and then lateral connections were added later as home locations were determined. The lateral connections were achieved by cutting or breaking a hole in the pipe and inserting a tap connection.
Structural defects, including cracks, fractures, broken pipe, holes, and offsets, are commonly found in lateral tap connections and the lateral pipes.
These defects create weaknesses within the mainline pipe and the shifting of the lateral that are a result from the loss of backfill material migrating into the pipe from the faulty connection. This can lead to pipe blockages, collapses or even sink holes in roads or parkways.
As mainline joints are eliminated through lining, the only entry points within the mainline become the lateral reinstatements. Root intrusion, infiltration and deposits are maintenance problems that can occur at an accelerated rate at the lateral connection once the mainline has been lined.
Effect of Unaddressed Laterals
The ability of groundwater to migrate along the sewer trench allows for water to find its way to lateral connections that have not been properly addressed. The same is true for tree roots seeking nutrients and water from a sewer line. Roots around break-in connections begin to grow rapidly into the newly lined sewer main from the lateral reinstatements creating blockages in the laterals and in the mainline.
Sewers that have been lined are not candidates for root removal using traditional root blades due to the possibility of damaging the liner.
Regardless of ownership or financial responsibility, unaddressed lateral pipes and interfaces affect a wastewater system by contributing a significant amount of inflow and infiltration (I&I). This in turn greatly lowers the overall carrying capacity, creates the potential for sanitary sewer overflows (SSOs), and increases the amount of clean water that must be treated at wastewater plants.
Forward thinking municipalities have already begun to address these areas within their collection systems as part of their rehabilitation and I&I reduction programs often as part of their lining programs.
GPSD’s Sewer Rehab Plan
The Greater Peoria Sanitary District is a special unit of local government that was formed in 1927 to collect and clean the domestic and industrial wastewater within GPSD’s service area. GPSD currently serves approximately 140,000 customers across an area of over 66 sq miles from 716 miles of sewer.
As GPSD approaches its 100-year anniversary, the self-funded organization is focusing efforts on a continuous multi-area rehabilitation program.
Several years ago, GPSD implemented a “75-year sewer rehabilitation” goal, wherein GPSD inspects and, if necessary, lines neighborhood sewer as a base average remaining life of 75 years. Since implementation of the program, GPSD has invested nearly $60 million into its collection system, with an estimated 20-year capital investment of $135 million.
The organization has also committed to an additional $121 million toward the rehabilitation of its treatment plant, built in the late 1920s and early 1930s. GPSD is expanding its rehabilitation programs further to cover lateral pipes and the mainline-lateral intersections, thus increasing its efforts to address defects within these areas that commonly plague other system owners that have only used mainline rehabilitation measures to renew their pipes.
GPSD has used lateral connection lining minimally in the past decade to address difficult repairs. Beginning in 2024, the district added 55 lateral connections repairs using cured-in-place pipe (CIPP) methods to its CIPP lining program. An additional 100 lateral connection repairs have been added to the 2025 CIPP lining program.
Using CIPP Technology
Utilizing CIPP technology, laterals and connections can be structurally rehabilitated to solve both structural and O&M defects using an installation technique from the mainline.
Centered at the mainline, a full 360-degree liner is attached to the lateral liner sock and includes a hydrophilic gasket at the mainline to lateral connection and O-Ring bands located at the endpoint of the sock.
The resin saturates a felt or fiberglass/felt hybrid liner and is then inverted into the lateral via a removable bladder and cured using steam, UV light, or ambient heat. The hydrophilic seal and bands swell when contacted by water, completing the seal.
The liner sock can be installed in laterals from the connection up the lateral of lengths up to 20 ft reliably without an exterior cleanout, of up to lengths of more than 200 ft to an exterior cleanout to address structural or O&M defects at the connection and throughout the lateral to the extent that is desired.
If a cleanout is available, lining the lateral can be achieved through the inversion of the CIPP liner from the cleanout towards the mainline or back towards the home, addressing only the lateral pipe and not the mainline interface. If a cleanout is not available, one can be installed by traditional open-cut methods or via vacuum excavation.
Vacuum Excavated Lateral Repair
If done by vacuum excavation, the process is simple.
The lateral is located at a structurally sound section from either the mainline via a lateral launch camera with a locating sonde, or from an interior cleanout or vent stack in the roof with a push camera with a sonde.
A 16-in. to 20-in. vacuum excavated hole is made, exposing the lateral section. A cleanout saddle tee, complete with a riser pipe and hydrophilic adhesive on the saddle is snapped on to the exposed lateral section. It is then backfilled and restored immediately, allowing it to cure for a minimum of 12 hours.
The cleanout rise is then filled with a water column for five minutes to verify it’s watertight, and the crown of the lateral is cored out to expose access to the lateral through the newly installed cleanout. The vacuum excavation method can be cost-effective due to the quick installation time and the minimal surface restoration necessary.
As GPSD looks ahead toward investing its capital spending program, the organization has begun to adopt the holistic approach to sewer rehabilitation, expanding into lateral renewal, manhole rehab, and a continued effort in mainline lining.
Andrew Hoerr is vice president of Hoerr Construction Inc. John Manijak is in business development with Hoerr Construction Inc.