Mechanical Joint Sealing System Provides Solution to Long Standing Issues in Large Diameter RCP Storm Sewer
A City in the Midwestern Corn Belt installed a new 84-in. Reinforced Concrete Pipe (RCP) storm sewer collection system in the early 1990s to provide relief from flooding. RCP has for many years had a reputation of having poor, weak or inconsistent joints. The concrete pipe industry as a whole has designed and built joints to meet certain standards; however proper installation techniques need to be employed and workers must be trained to ensure a quality installation of the piping system.
This RCP storm sewer was installed in a historic part of the City and was designed using a confined O-ring gasketed joint. These O-ring joints meet the strict requirements of ASTM Specifications C361, Reinforced Concrete Low-Head Pressure Pipe and C443, Joints for Circular Concrete Sewer and Culvert Pipe, using flexible, watertight rubber gaskets. It also meets the requirements of the Bureau of Reclamation specification for the type R-4 joint and is ideally suited for reliable yet economical transmission of water at internal pressure heads of up to 125 ft.
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The pipe was designed to be watertight and provide many years of service, but almost immediately the pipe began to show signs of infiltration and exfiltration through the joints. It became apparent that there had been problems during installation of the pipe and the City now was faced with finding a solution to seal approximately 230 joints in the pipe segment.
Traditional repair methods, such as excavation, were not an economical option, so the City researched a variety of trenchless methods to make the repair from the inside of the pipe, including chemical grout, cured in place pipe (CIPP) and mechanical internal joint seals. In 2010, the City decided to do a trial installation of the HydraTite Internal Joint Seal System for the purposes of evaluation. Two 84-in. HydraTite Internal Joint Seals were furnished and installed by Cretex Specialty Products, a distributor of manhole and pipe joint sealing technologies located in Waukesha, Wisconsin. After approximately six years of successful service on the two trial seal installations, the City hired a consulting engineer to design, bid and construct the repairs utilizing the HydraTite Internal Joint Seal System.
In fall 2016 the project was put to public bid and awarded to the low bidder, HydraTech Field Services LLC, located in Cincinnati. The bid included furnishing and installing 231 HydraTite Internal Joint Seals of varying sizes, including 215 at 84 in., 1 at 72 in., 10 at 60 in. and 5 at 48 in. There were also bid items for traffic control, storm sewer cleaning, lift hole patching, manhole chimney rehabilitation and other miscellaneous items.
Work commenced in mid-January 2017, starting with a preconstruction meeting held with the City, the engineering firm and the contractors. Traffic control was then setup and the sewer cleaning contractor started the process of removing sediment from the 84-in. line. In conjunction with the cleaning, all the lift holes in the pipe segments were filled with a non-shrink repair mortar.
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Access to the storm sewer for the material, tools, equipment and crew personnel was through a single 2.5-ft X 3.5-ft entryway in the roadway, which posed no problems for the HydraTite system. Once the first portion of the pipe was cleaned, the HydraTite internal joint seals, retaining bands and tools were loaded into the pipe through the access point and the installation process commenced.
The system of installation required that technicians verified a proper sealing surface for the seal to cover over the joint and repaired if necessary. Each joint was air tested for leakage and was inspected by the engineering firm to verify each joint was watertight and free of any leaks. During the eight-week project, there were some delays due to weather events such as snow and rain. On those days the HydraTite Seal installation was not performed due to higher than normal flow in the pipe; however the project was still completed on time.
Since the project was completed in April 2017, the area has not experienced any of the infiltration or exfiltration problems previously found in this storm sewer collection system.
Lee Haessig is general manager at Cretex Specialty Products, Waukesha, Wisconsin.
