Regional DNO Substation
A regional DNO had identified that a bund protecting a transformer at an electricity substation would benefit from relining. The deterioration of bunds is a widespread problem for DNOs, who are subject to strict regulation by the Environment agencies in the UK (the EA, SEPA, NRW, and NIEA), and risk paying penalties if bunds fail to contain spills. Adler and Allan was asked to inspect the site and carry out the relining, but our inspection revealed more fundamental structural problems with the bund. We found cables laid loose under stone and into broken ground with no protective ducting; crumbling mortar at the join of the bund wall and bund base; and crumbling mortar beneath the transformer plinths, which exposed vulnerabilities in the bund base. All these problems had to be remedied before relining could commence.
Our priority was to carry out the works with the minimum disruption to the DNO’s operations, and we modified our techniques as needed, to reduce the need to switch out equipment. As is always the case in a hazardous environment, the works were supervised by an Adler and Allan client approved Competent or Approved Authorised Person. The procedures we follow in such cases are:
- Audit and testing. We inspect the site, and price and prioritise works. Bunds that are thought to be in good condition are hydro tested to check for leaks.
- Stone removal. Any aggregate is removed by hand or vacuumation unit, depending on ease of access, to allow closer inspection and access for repairs.
- Cleaning and preparation. The bund walls and floor are cleaned and surface treated, and minor holes are plugged, to prepare a smooth surface for liner application.
- Repair. We repair significant defects in the bund walls and base. We construct new cable ducts and paths, raising manhole covers where necessary.
- Relining. We apply a state-of-the-art epoxy lining, suitable for use in in a hazardous electrical environment.
- Testing and completion. The bund is hydro tested to ensure that it does not leak. After replacement of any aggregate, the bund is certified and all works guaranteed.
Adler and Allan was contracted to restore all the bunds in the DNO’s region into a fit-for-purpose condition. Our approach, combining traditional repair methods with innovative technologies, allows the work to be done quickly - often within one day - and with little or no impact on the supply of electricity. The DNO benefits from a lower cost per bund compared with using only traditional repair methods, and is protected from the risk of paying environmental penalties. Bund restoration also enhances the value of the DNO’s assets.