Deterring Illegal Wild Swimming in Dangerous Quarry Lakes

Swimming in quarry water is dangerous. Following large scale trespassing at Chinnor Quarry, owners Taylor Wimpey selected White Horse Contractors to deploy an environmentally safe dye to deter trespassers from swimming in two large lakes.

Key Achievements

  • Acquired and operated a pontoon to survey and clean the lakes

  • Removed all litter and waste left by large volumes of trespassers

  • Helped to limit disruption to wildlife habitats

  • Successfully dyed large chalk pit lakes

  • Reduced trespasser ingress and risk of injury or fatality from illegal swimming

The Challenge

With their appealing colour, clear waters, and beautiful backdrop, Chinnor Quarry pit lakes drew huge crowds of illegal trespassers during the 2020 Covid-19 lockdown (as reported on BBC News). However, old quarries are dangerous and unsafe for swimming. Water depth can drop suddenly, temperatures can reduce rapidly below the surface, and chemicals can be present causing skin irritations and stomach upsets.

Concerned for public safety site owners Taylor Wimpey quickly deployed security staff to the site. Whilst this deterred some members of the public, many found their way back to the quarry. For Taylor Wimpey, their next source of discouraging people from the site was to reduce the attractiveness of the lakes. The High Wycombe based company sought an innovative contractor, with experience in water engineering and environmental services, who could meet the urgency of their needs.

The Solution

The British housebuilder selected White Horse Contractors to oversee the project, thanks to their awareness of our range of services and ability to turn this time-sensitive project around. Within three weeks of the initial enquiry, we were on-site testing our proposed solution, an environmentally safe black dye that is normally used to reduce algae growth in ornamental lakes.

With these tests meeting our clients required criteria, our team designed and constructed a purpose-built mixing station for the dye. Our expert operators mounted the station to a brand-new floating pontoon, acquired specifically for the project. Once applied to the lake the dye blocked UV light from entering the water body. This innovation reduced the visual appeal of the water and meant that potential wild swimmers and cliff-jumpers could no longer see the bottom of the pit, ultimately reducing the chance of them entering the water, deterring the public from using the quarry as a social setting.


With the lakes successfully and safely dyed the site was far less appealing to the public, reducing trespasser rates and meeting Taylor Wimpey’s aspirations for the project. Over a period of 4 weeks, the works were completed, and in-house Water Engineering specialist Nathan Jackaman was very pleased with the results of the Water Engineering division’s work:

“I’m glad we’ve been able to find a solution for Taylor Wimpey, sourcing the dye was relatively straightforward, but distributing this into the quarry was an exciting challenge for us as we had to fabricate a bespoke piece of machinery! It’s something we've never done before to this scale, but we can definitely say this was a success for everyone!”

Nathan Jackaman, Water Engineering Specialist, White Horse Contractors

For more information call 01865 736272 or email