Leaking tank

A friend told me this morning how he and his wife spent all day emptying the irrigation tank which was leaking, removing fish and a lot of sludge. I offered to help today to complete the job and I sprayed while he brushed to remove the remaining muck and try to establish where the leak is coming from. It would seem that the concrete has become porous although there are also one or two cracks. A liner would be horribly expensive so the solution may be a delivery of a large amount of concrete to reinforce the base.