Long-standing issues require thoughtful solutions
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 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. They also meet the requirements of the Bureau of Reclamation specification for the type R-4 joint and are suited for reliable, yet economical transmission of water at internal pressure heads of up to 125 ft.
The pipe was designed to be watertight and provide many years of service, but it began to show signs of infiltration and exfiltration through the joints almost immediately. 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, Wis. 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 the fall of 2016 the project was put to public bid and awarded to the low bidder, HydraTech Field Services LLC of Cincinnati. The bid included furnishing and installing 231 HydraTite internal joint seals of varying sizes, including 215 84-in., one 72-in., 10 60-in. and five 48-in. seals. There also were 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 set up, 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. Access to the storm sewer for the material, tools, equipment and crew personnel was through a single 2.5-ft-by-3.5-ft entryway in the roadway, which posed no problems for the HydraTite system. After 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 that it 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.