Searching for the ultimate industrial cleaning agent, engineers have turned to washing up liquid to remove a black oil slick from the north east pier of Telford's Menai Bridge. On top of each of the Menai Bridge's masonry piers sits a bath containing around 1m 3of oil, which lubricates and protects the roller bearings to which its suspension chains are attached. Over the last two decades, oil has leaked from the bath on the north east pier, creating a stain from the pier head to deck level. Bridge manager UK Highways took the decision to clean the pier earlier this year, and following trials of cleaning agents including caustic soda, consultant High Point Rendel specified biodegradable Ecover washing up liquid for the job. The Menai Straits, a stretch of tidal water separating Anglesey from the north Wales mainland, is a site of special scientific interest (SSSI). In contrast to conventional cleaners, the Ecover broke down oil leaving the underlying patina of lichens on the pier intact. And it produces nothing more harmful than biodegradable soap suds.