Spirally Wound Pipe Solves Atlanta Rehab Challenge

Sekisui SPR Americas LLC has been in Atlanta for more than six years. During that time, the company has worked closely with local municipalities, contractors and consultants. The City of Atlanta’s underground infrastructure is more than 100 years old and deteriorating in many places, with infiltration a major problem during rain events.

From 2007 through 2008, Atlanta witnessed some of the lowest rainfall amounts in years, causing a drought. The city recorded just over 31 in. of rainfall for 2007. Then in 2008, things turned around. Atlanta received 70-plus in. of rain, which caused flooding through 2009. It also highlighted problem areas within the infrastructure for Atlanta.

One area that stood out was a 90-in. trunk sewer line that was nearly 100 years old. The Atlanta trunk sewer is a cast-in-place sewer pipeline. Although it is referred to as a 90-in. pipeline, it is not circular. It is an arch-shaped pipe constructed with four individual pieces. The original construction allowed the concrete to be set in place with cold joints. The pipeline is very shallow to the crown, and at points in the line, above-ground and exposed.

The sewer pipe typically runs at 50 percent of capacity. During rain events, the pipe will take on excessive infiltration and surcharge. Combined with the extra flow from the flooding in the Atlanta area in 2009 and the lack of cover in some areas of the pipeline, the cold joints were detaching and allowing severe overflow.

Currently, the infiltration whereabouts are still unknown and inspections and cleaning is ongoing to find the largest problem areas.

Several external repairs were initially added to the original host pipe on the areas that are above-ground. The previous repairs were not proving to be sufficient enough to stop the overflows during major rain events.

The City of Atlanta decided to use Sekisui spiral wound pipe renewal technology (SPR) to permanently repair the host pipe and stop the overflows that were occurring place during heavy rain events and flooding. Sekisui SPR Americas LLC was made aware of the problems in late 2008 and proceeded to introduce the city to the proposed green solutions it could offer.

The pipe length to be rehabilitated totaled almost 2,500 lf. For 1,200 ft, the crown of the pipe was exposed completely; 100 lf are on a golf course and within a gated community and the remaining pipe had minimal depth of cover to the crown.

The City of Atlanta specified a minimum 50-year design life for the rehabilitated pipeline. Access to the pipe was difficult due to heavily wooded areas, private residences and a golf course. Bypass of the existing flow would increase the cost of the emergency project for the city of Atlanta, which was already witnessing strains in its budget due to the flood’s damage. A small footprint was required for construction within the community to cause less disruption to the private residence.

Sekisui SPR was the solution. An 84-in. circular, monolithic profile with dual locking mechanisms was machine wound into the host pipe to create a new pipe, within the surcharging cast-in-place concrete. The construction started in spring 2010. The winding operation commenced on the pipeline in late summer 2010.

The contractor had many advantages by using the machine wound method. It’s environmentally friendly and no chemicals are released during installation. The carbon footprint at the worksite was minimal. No excavation was required for the SPR process. A fully structural design was given back to the city. The pipeline’s flow capacity was minimally impacted and the monolithic profile used during the SPR winding process created an infiltration free, rehabilitated pipeline.

Grouting was completed on the project in late 2010. The SPR profile has been wound creating the new pipe inside the host pipe.

The flooding of 2009 revealed a surcharge problem on an existing 90-in. trunk sewer in a private neighborhood in Atlanta. The budget was strained for the city, and the need for a rehabilitation project was dire. Sekisui SPR Americas LLC was able to offer a completely trenchless solution. The machine wound, spiral pipe renewal process provided an alternative rehabilitation process to the city that was: environmentally friendly, truly trenchless, efficient and affordable, capable of installations with less disruption to the private residence and golf community and capable of completing the long lengths of pipe that had minimal access points or manholes without excavation.

Jonathan Vaccaro is business development manager for Sekisui SPR Americas LLC, based in Atlanta.

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