In the summer 2009, the Seattle Public Utilities (SPU) discovered two joint leaks in one of its 66-in. ID raw water transmission pipelines.
This particular pipeline was installed in 1959 and is a Pressure Class 100, Concrete Cylinder Pipe, with rubber gasket Carnegie joints at every 16 or 32 ft, depending on the pipe length that was used. Internal inspections by SPU revealed that the leaks were the result of the pipe joints being pulled apart longitudinally, which was attributed to a deep seated land slide in the area. Six other joints of concern were also discovered during the internal inspection. However, the pipeline was found to be in good condition and did not require complete replacement. Additionally, conventional dig-and-replace methods would be relatively expensive and time consuming.
SPU needed to return this pipeline to service quickly in order to perform other scheduled water system maintenance. Due to the short available work window, as well as several unknowns, SPU decided to repair the pipeline using internal joint seals. While only two leaks were found, SPU elected to install internal joint seals on all eight damaged joints found during the internal inspection.
In September 2009, Tri-State Construction, Bellevue, Wash., was awarded the general contract to commence all work as specified on Tolt Pipeline #1 and Tolt Pipeline #2. Tri-State selected J. Fletcher Creamer & Son Inc. (JFC), Hackensack, N.J., as its sub-contractor to supply and install a total of 11 In-Weg Internal Seals that would be used to properly seal the eight problematic joints on Tolt Pipeline #1. This work needed to be completed before Tri-State could perform the work on Tolt Pipeline #2. The 11 In-Weg Internal Seals consisted of six Standard Width seals including three 4-ft long rubber SLEEVES and five Extra Wide seals. The use of SLEEVES is occasionally required to internally repair and seal longer sections (up to 14 ft) of pipe.
The In-Weg Internal Seal is a rubber seal that is made from non-toxic EPDM (ethylene propylene diene M-class) rubber and is used to permanently eliminate leaks at internal pressures of up to 300 psi. The seal can be trenchlessly installed on a variety of pipe materials and pipe diameters of 16 in. to 18 ft and larger. The seals are safe to use in potable water applications, as well as wastewater, storm sewer, natural gas and industrial applications. In all cases, the existing pipeline is in good condition; however, the only problem is that the joints are leaking. These leaking joints may be the result of: poor installation, deteriorating joint compounds, aging gaskets, soil settlement and movement or earthquakes.
As with any In-Weg Internal Seal installation, preparation of the existing pipe surface is necessary to properly “seat” the seal. JFC trained and certified In-Weg installation crews needed to grind down the spiral-weld of the existing concrete cylinder pipe in all areas where the In-Weg lip-seal would come in contact with the existing pipe surface. This was a relatively difficult and time-consuming aspect of the overall project, but a critical requirement that would ultimately lead to a successful bottle-tight installation.
The amount of time that this pipeline was out of service was critical to Tri-State Construction and SPU. Therefore, JFC crews were mobilized on Sept. 27 and completed all aspects of the installation of these 11 seals by Oct. 12. Overall site preparation and coordination was provided by Tri-State Construction Inc., with site inspection provided by the City of Seattle.
Tri-State project manager Ashley Sharples said that “[Tri-State was] pleased to have J. Fletcher Creamer & Son Inc. working as our sub-contractor. With only a short time period between contract award and when the work had to begin in order to meet the deadlines for completion, JFC stepped up to the plate and made it happen. The quality of their work, concern for safety, willingness to do what was necessary to satisfy the owner’s concerns along with their previously established working relationship with Seattle Public Utilities all contributed to the success of this project.”
After installation of the seals, SPU leak tested the pipeline and found no leaks. The pipeline was then returned to service in time for Tri-State Construction to complete the other critical system work on Tolt Pipeline #2.
Robert Biase is the director of business development for J. Fletcher Creamer & Son Inc., which is headquartered in Hackensack, N.J.