The background

Barhale/North Midland Construction JV were working on behalf of Severn Trent Water to upgrade the sewer system and increase foul storage capacity within the system in Newark-on-Trent. As part of this scheme two new sewer tunnels have been bored under the centre of Newark. This meant the existing combined sewer overflow (CSO) on north gate needed to be connected into the new tunnel. For this to take place the CSO needed to be over-pumped whilst North Midland Construction carried out the necessary works required to connect the existing CSO into the new tunnel.

The challenge

Whilst dry weather flow was easily achievable at 136 l/s, there needed to be the capability to move flows of up to 1,400 l/s whilst still maintaining a suitable and dry working environment for their staff.

The Selwood solution

Selwood initially attended site to discuss a suitable solution for their challenge. The dry weather flow was easily achieved utilising a standard self-priming pump, however as we had to cover up to 1,400 l/s and with space being at a premium we had to look at another alternative.

The NZ3301 LT pumps fitted the bill perfectly and allowed coverage of approximately 1,450 l/s with four pumps running whilst at the same time being self-priming. The narrow footprint of the NZ stands allowed us to fit the pumps side by side on site. The pumps were controlled by 55kW inverter panels with speed control taken care of by an ultrasonic level controller giving out a 4-20ma signal.

The dry weather flow was powered by a 100kva generator running 24/7 whilst the assist pumps were powered by a single 320kva generator which started on a signal from our ultrasonic level controller.

The result

Selwood managed to successfully over pump the CSO whilst North Midland Construction carried out the works needed over a two week period. The customer was pleased with the result. Pump Solutions Manager, Dominic Devaney commented, “Increasingly we are looking at ways of providing solutions which meet the flow and space requirements, which can be quite challenging. With our vast experience gathered over years of overpumping applications we are able to find ways of using pumps to solve any problem”.

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