Squeeze technique works for leachate pipe

Improvement works on a landfill leachate pipeline eliminated waste tankering costs with an innovative approach, reveals Ming Zhu, technical manager of Alpheus Environmental

Waste Recycling Group (WRG) has a 4.5km-long,180mmdiameter HDPE discharge pipeline, built 10 years ago, which sends treated landfill leachate at Stewartby Landfill site, Bedfordshire, to a public sewer. Flow through the pipeline has been gradually decreasing over the years with fouling and/or blockage considered to be the major contributing factor.

The pipeline does not have any cleaning or washout chambers along its entire length, making pipe cleaning a difficult task. Alpheus Environmental, which is part of the Anglian Water Group, carries out maintenance work on pipeline air valves and was engaged by WRG in 2010 to address this issue.

Alpheus proposed the construction of several manholes along the pipeline to allow for a combination of jetting and pigging operations to be carried out. In constructing the first manhole in December 2010, careful consideration was made about how to break into the pipeline.

Due to the nature of the pipeline profile and lack of isolation valves for 2km length, up to 35m3 of leachate would need to be drained and tankered away, involving significant downtime and tankering costs.

Working with its civil partner, Bedford-based Alpheus used a pipe squeeze technique where the HDPE pipe at two ends of the manhole position was clamped to isolate the flow, eliminating the need to tanker large volumes of leachate.

After installation of two new valves, the clamps were removed and the pipeline put straight back into service. Due to the thermal plastic nature of HDPE pipe, its shape was practically restored after 24 hours.

Construction of the manhole went successfully and required only six hours of downtime for the pipeline.

WRG project manager Patrick Bailey commented: “Alpheus managed the construction work really well, kept everyone informed, and required minimal input from us. Their use of the pipe squeeze technique simplified the whole construction operation and was particularly well received by our operation team at the leachate treatment plant.”

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