This month, around 1,500 residents of Whaley Bridge were evacuated from their homes as a precaution taken in the event of a nearby damaged dam collapsing. The dam held back 1.2m tonnes of water from the Toddbrook reservoir, and was put under strain after a sequence of heavy rain and thunderstorms threatened to cause overspill into the nearby town. Whilst the residents were safely allowed to return to their homes, the general upkeep of the dam has been called into question by government officials and industry experts alike. Heavy rain is expected in the north of England and structures are built with it in mind. It was however, the extent of the damage to the dam’s spillway which led to the evacuation of Whaley Bridge, leading engineers to question what went wrong.
For some, the presence of vegetation on the dam has led experts to put the collapse down to an excess of water entering the structure itself. Plants and grass growing on the slipway suggest a weakness in the dam’s structure as roots create cracks and holes in the slabs which allowed water to enter and for slabs to come off. Failure to reinforce the slabs with steel also means the dam might have been weaker than it should have been, even before the extremely heavy rainfall. Though the extent of the dam’s internal weakness is yet to be determined, the issues being raised underline the crucial importance of investing in and maintaining structures after the opening ribbon has been cut, to avoid life-threatening disrepair.
Engineering involves a 360 degree view of a site and its structure but it also involves thinking forwards and backwards in time. Good engineering means planning for the future and weather proofing is a crucial part of design work. Of course, there are extreme weather events for which you can never be fully prepared, but understanding the context of a site is incredibly important. Whether it’s site sloping, the load paths of existing structures or water drainage, a thorough site investigation is an absolutely vital part of the engineering process. It’s only by doing your homework and fully understanding a site’s context that you’ll be able to find the best engineering solutions and be able to build for longevity.
However, building for longevity nowadays involves another angle: building sustainably. Extreme weather conditions are linked to climate change, so to further protect our built environment, we need to protect the natural one. That’s why Lyons O’Neill, along with over 80 other engineers have signed the UK Structural Engineers Climate & Biodiversity Emergency Declaration. This pledge recognises the crisis of climate breakdown and commits to ‘meeting the needs of our society without breaching the earth’s ecological boundaries’. It’s a pledge that informs our practice, and our team is always looking to use the most sustainable methods in our work, from our use of Cross-Laminated Timber, to designing Sustainable Drainage Systems (SuDS) and helping clients achieve high BREEAM ratings.
]The aversion of the dam’s complete collapse is one of the better stories of 2019 and testament to the round-the-clock efforts to reinforce its slabs. Though it was incredibly fortunate the town didn’t flood and no one was hurt, the reservoir threat is still ongoing for Whaley Bridge and it’s clear there’s much work to be done. This episode also has crucial lessons to teach us around the design and upkeep of structure, which construction teams would be foolish to ignore.