Hillingdon Council have we have evidence of blue green algae at Ruislip Lido which can be harmful to animals and toxic to humans. The algae is a natural occurrence in hot and sunny weather.
The advice from the Environment Agency is that landowners should assess risk, ensure adequate signage is in place and consider restricting access. Algal blooms: advice for the public and landowners – GOV.UK (www.gov.uk)
They can control the bloom by covering it and controlling the supply of nutrients to the water, but this is practically very difficult on the Lido.
Given the evidence of dogs and visitors accessing the water, as a precaution they have temporarily fenced off the waterline to restrict access and placed signs on the entrance / exit points around the Lido and also on the fencing. The beach remains accessible.
They will review the position early next week. The Corporate Communications Team are sharing updates with residents through the usual channels.