Air Technology Systems Limited have provided a specialist ventilation solution within the new main shaft pumping Station at Beckton Sewage Treatment Works, says Pete Dimmick
The four-mile Lee tunnel, constructed for Thames Water, will run beneath the London Borough of Newham from Abbey Mills to Beckton and will help prevent more than 16m tonnes of sewage mixed with rainwater overflowing into the River Lee each year, by capturing it and transferring it to Beckton Sewage Treatment Works, which is being expanded to enable it to deal with the increased volumes of sewage and flood water.
A new main shaft pumping station is being constructed within a 38 m-diameter, 80 m-deep shaft at Beckton and linked to the main Lee Tunnel.
The main area of the pumping station will be divided into two dry well compartments, which will house the pumps and motors to pump the storm water into Beckton STW for treatment.
The pumping station has two designated access shafts to allow safe ingress and egress from the pumping station for maintenance.
Air Technology Systems (ATS) was approached by MVB to quote for the ventilation for this specialist project – involved from the get-go were ATS managing director Steve Boon and Rebecca Clisset, ATS operations director.
MVB began construction of the pumping station in 2010 and awarded ATS the ventilation package in 2013, where we began to work with the MVB design team.
The ventilation systems to serve the main shaft are designed to achieve a safe working environment for operatives due to the risk of hydrogen sulphide being present, but additionally to overcome the huge heat gain from the large pumps.
Air is supplied to both sides of the shaft via large plants located outside the shaft, with large vertical ductwork being used to distribute air evenly throughout the drywells.
The use of our Jetflo nozzles are key to achieving a high ventilation efficiency by thoroughly mixing the air, diluting any heat and contaminants such as hydrogen sulphide and creating the best possible working environment.
Air is extracted from low level from both sides of the shaft, another key design feature being that hydrogen sulphide is heavier than air and so collecting air at low level is another way we have increased the ventilation efficiency. Pumps are also located at low level and so we are able to capture heat at source and exhaust to outside.
The access shafts had different design requirements with a need to provide both general ventilation to the stairways, but also to pressurise the entire access shafts for firefighting.
The system has been fully designed in accordance with BS EN 12101-6:2005 to provide a Class B system for means of escape and firefighting.
The design process has been challenging. The entire main shaft ductwork system is 316 stainless steel in order to achieve a 20-year design life and, with some of the ducts being 2.2 m diameter, we have used specialist construction techniques.
Due to the depth of the pumping station, replacement of ductwork will be very difficult and so selection of the correct materials is important.
The entire access shaft ductwork systems are 316 stainless steel, but fire-rated for 4 hours.
Pete Dimmick is contracts manager at Air Technology Systems