The Dan Region of central Israel has in recent years experienced significant population growth in line with revitalisation of the area. Subsequently, the Dan Regional Association for Environmental Infrastructure, also known as Igudan, had concerns that the regions wastewater network capacity may not cope with this growth.
Inspection of the 40-year-old wastewater system highlighted some significant defects and Igudan started looking for a solution that would mitigate these faults. Several different rehabilitation options were investigated with ultimately a sliplining solution being the option selected. The pipeline in question for this work was the Igudan Q Line South, which is located near the coastal town of Bat Yam.
In selecting sliplining as the preferred option for rehabilitation of the pipeline, Igudan chose what is believed to be the first and largest project in Israel using this technology. The contractor selected for the work was E.R Itshaky-Microtunneling Israel, which has since its establishment in the 1960s serviced the Israeli civils engineering sector, which in later years included water and wastewater projects.
Sliplining was deemed to be the only practical solution for the Q Line South work due to the crowded buried infrastructure in the area, which negated the installation of a new tunnelled pipeline or any open cut option.
The required liner pipes were however of significant size, being up to 10 ft (3 m) in length and up to 78 in (2,000 mm) diameter. Therefore, a system of the right capacity to handle such pipes was needed. Yaki Itshaky, who heads up the contacting company said: “Each section required equipment suitable for high jacking forces and execution under streaming sewage. The uniquely designed SLS100 sliplining system complies with these two main parameters.”
The Akkerman SLS100 operates without the need to install bypass pumping as it will work in live sewer flows, so negating any service interruptions to consumers during the works. It comprises an all-in-one pipe jacking system that can accommodate pipes of up to 102 in (2,590 mm) diameter when utilising spaces and frame extensions.
Comprising the jacking frame, power pack and pipe specific thrust rings, the unit is remotely controlled using wireless systems by the operator. An LCD screen enables the operator to see all operational functions together and provides live data logging via a VPN and customised web dashboard.
Given the ‘live flow’ nature of the works undertaken, the addition of pipes to the liner
string is controlled by hydraulically linked pipe elevators with a drawbar-mounted
thrust ring which engages with the pipe to provide axial advance. The system also uses
a retention winch and grips which negate pipe buoyancy and counter live flow forces to
keep the pipe string aligned during the jacking process.
Overall, the sliplining works required for the Q Line South project comprised the installation of some 4,970 ft (1,515 m) of liner pipe across three diameters from 70 in (1,800 mm) to 78 in (2,000 mm) diameter with some 60% of the work being under live flows. Liner pipe lengths varied from 8 ft (2.5 m) up, to 10 ft (3 m) depending on the location, with shorter pipe lengths being utilised where a curvature existed in the host pipeline.
Timing of the works was vital given that the installation window available for jacking was limited to when the live flows were at less than 50% of the host pipe diameter. This usually comprised working for two hours in the early morning hours, followed by a rest of one hour whilst flows retained by a control valve upstream were allowed to pass through the system, followed by a further two hours of lining before normal day-time flows were again reached.
Limited access space and the need for minimal disruption around the launch shafts was also a consideration.
The first shaft was positioned for minimal disruption to local residents under a park area. The shaft was 17 ft (5.4 m) wide, 32 ft (9.7 m) long and 24 ft (7.3 m) deep, to accommodate the Akkerman jacking frame.
Before the sliplining work could proceed, the contractor ran a prover through the host pipeline to remove any debris deposits and to enable the cutting out of the top half of the host pipe for access from the jacking shaft.
The second project site, also under live flows, required the lining of some 1,980 ft (600 m) of host pipe and was completed in just one week after completion of the set-up. Here installation rates of up to 45 pipes per shift were achieved, using 8 ft (2.5 m) jacking pipes.
Finally, the longest installation section was some 2,510 ft (765 m), which included a 492 ft (150 m) long curved section which exited into the multi-level, deep shaft. Here short length pipes were installed to provide the curvature required to complete the lining process.
“Israeli regulations exist to protect underground water pipes which are adjacent to sewage, so the last section was performed in two stages in a dry environment. The first stage was pipe jacking as a protection layer for the host pipe, and the second was sliplining in the new jacking pipe.” said Itshaky.
Whilst anticipating further similar works using the Akkerman SLS100 unit, Itshaky concluded saying: “Sliplining with the Akkerman SLS100 system technology helped us to complete this challenging project efficiently and effectively. E.R. Itshaky is proud to have successfully introduced this new technology to Israel for the benefit of Igudan, and further trenchless options in the urban area.”