We have a drained sewage lagoon that has been left for about 8 years. Would this be good for growing a vegetable garden?
Waste From Sewage Lagoon for Garden Fertilizer
Certified GKH Gardening Expert
The safety of the waste area for gardens is out of my expertise, though I would urge you to use caution.
You may want to start with having the soil tested to see what you are working with.
Here is an article that covers some basic advice.