Elliot Burton’s body was recovered from Kirkthorpe Weir in July 2019, four days after he was reported missing.
CCTV footage showed he had entered the unmanned site and fallen into an outlet channel.
Elliot, a non-swimmer, was unable to save himself, an inquest was told yesterday.
After the inquest in which a misadventure verdict was recorded, a senior coroner has written to Yorkshire Hydropower, which owns the site, and Wakefield Council, to urge them to take action to prevent further deaths.
The area is known for attracting trespassers who can easily access the site, which is usually unmanned, and Kevin McLoughlin, senior coroner for West Yorkshire, said he was particularly concerned for children living on the nearby Eastmoor estate as the summer holidays approach.
In a report to Yorkshire Hydropower and the council, seen by The Yorkshire Post, Mr McLoughlin wrote: “During the course of the inquest the evidence revealed matters giving rise to concern. In my opinion there is a risk that future deaths will occur unless action is taken.
“Despite the passage of some 21 months since Elliot Burton’s death, little effective action has been taken to reduce the risk of children being harmed if they are tempted to trespass on this site.”
The site was converted in 2017 to a generating plant that uses the flow from the nearby River Calder to generate electricity.
Yorkshire Hydropower and the council must legally respond within 56 days, setting out a plan of action to prevent further deaths at the site or state why no action should be taken.