I am not sure how the riser is connected to the lateral pipe as it is under water. We are waiting for a young volunteer to crawl into the 43" pipe to video, photograph and measure the break. From the outside, there is mud and a pool of water that means we can't get a good look from the outside so we are going to see what we can see from the outside. I imagine it is pretty simple; a control gate welded into the bottom of the riser that was inserted into the lateral pipe that looks like it rests in a concrete box (now under mud too). Crawling into the pipe is "easy"; there is about a 4" across stream of spring water flowing through it all the time that the volunteer will straddle.
As to how we know the pond is empty in the other comment, we can see it. It is a community pond that I think the developers dug in order to do something with the continuously flowing underground springs. The 13-year old flow control gate simply rusted through and failed, emptying the pond. There were no invasive species of fish or plants.
I keep hearing that a siphon system is the best replacement. Can you put that in the lateral pipe at the bottom of the pond rather than drilling into the pond wall?
