Pump Tests and Flood Bunds
Hello hello! Long time no see! It’s been a hectic, busy, busy time over at Alba Dewatering HQ, alongside working on several projects that were strictly confidential until some unknowable time in the future – which means, there’s not been a lot to talk about in the newsletter.
As these periods come and go, we’ve decided to not stick to a once-a-month schedule, but release new issues when we’ve got news we can share or things to discuss.
With that in mind, this issue is going to be discussing a site that was supposed to be rather straight forward, but ended up being a touch more complicated than expected. Check it out below:
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Potwell Dyke, Case Study
“Tackling storm overflows in England is a government priority. It is an issue which has received significant public attention, and the government is firmly committed to a step change on action to protect public health and the environment from storm overflow discharges.
“There are around 15,000 storm overflows in England, and in 2020 there were over 400,000 sewage discharges, totalling over 3 million hours. It is the government’s strong view that this is unacceptable.”
Department for Environment, Food & Rural Affairs, Retrieved 15.11.2023 https://consult.defra.gov.uk/water-industry/storm-overflows-discharge-reduction-plan/
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Contractor: Structural Soils
Nature of Project: Pump Test
Project Outline: As part of flood alleviation plans for Southwell village in Nottinghamshire, an earth flood bund was proposed in the location. This earth flood bund would have a control valve that would effectively dam Potwell Dyke (a small stream) should storm conditions and a risk of flooding occur in the area. Such a measure would help protect some 100 homes downstream from flooding.
However, there were valid concerns on the impact of such an earth flood bund on ground conditions, with operation of the control valve potentially leading to flooding on the northern side of the bund. A pump test was therefore needed to determine the efficacy of an earth flood bund and analyse the hydrogeological properties of the proposed site.
As the Dewatering Contractor, it was Alba Dewatering’s (Alba) duty to perform the pump test to the specifications agreed and outlined by the client. Alba supplied all necessary equipment – including suction pumping and recharge equipment, alongside pipework, valves, and tanks – as well as risk assessment and method statement (RAMS), labour, personnel management, and the provision of data-loggers over the period of the testing.
On-Site Insight
Initial delivery of Alba equipment was made to the site on Monday 16th October, ready for the first pump test which was planned and carried out the following day. The first and second pump test were carried out without issue and to the specifications outlined in the initial test plan.
The third pump test was initiated on the Friday (20th October), but was abandoned due to heavy rain fall, causing Potwell Dyke to overflow into the neighbouring fields where the test was being conducted. As a result, the third pump test was carried out the following Monday. Pump tests were successfully completed on every day following the 23rd, until the 27th, when the equipment was demobilised and stripped out ready for collection. With the exception of the Friday surge, everything else went smoothly, and the schedule was maintained.
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Ultimately, the team are well versed in doing pump tests in a variety of conditions, but they were given first-hand experience of why the flood alleviation measures were considered such a priority for the village and its inhabitants. “The Friday we were on site was particularly wet, with torrential rain non-stop over the entire day. The water levels quickly spilled over the banks, across the field and into the area we were doing the tests. The village flood warden visited the team and gave us some insight into the history of flooding in the area – which was relatively persistent year on year, with building and road closures. The water levels were consistently high while we were on site, adding some difficulty to the work.”
Commentary by an Alba Representative on site
