Campaigners fighting to save Llanishen Reservoir are appealing for public support to prove to an inquiry it has a future.
The supporters plan to dispute claims from owner Western Power Distribution that the 60-acre site could never be used for sailing again as restoring the facilities would be too expensive.
Western Power is understood to be using this argument to support their application to build 324 homes on the listed Victorian reservoir.
But when the public inquiry restarts next week, after a break of nearly a month, the Echo-backed campaigners hope to prove the US-owned electricity giant wrong.
The campaign, which has been fighting the development for a decade, has the support of Cardiff council and has received offers of help from people with the expertise to help rebuild the sailing facilities.
Baroness Jenny Randerson is now leading a bid to enlist more support.
She said: “I would urge the many people who feel strongly about this issue, and I know there are many thousands who do, to offer your help in kind and in expertise.
“That would be immensely helpful in showing that the community and the council are continuing to co-operate strongly to support sailing at Llanishen Reservoir as they have done throughout this campaign.”
Cardiff council’s operational manager, Simon Howell, has also written a letter which will be submitted to the inquiry underlining the local authority’s determination to support sailing at the reservoir.
He wrote: “I can confirm that the council’s intention remains to resume sailing activities at the reservoir as soon as water levels return to an appropriate level.
“The campaigners believe sailing could restart safely within four years, although it will not be full for around eight years.”