I don't see how to add a drawing here, but I can describe it: We had a 42" steel riser pipe with a trash catcher on top going down into what I think is a concrete pad (it's under spring water and mud). Attached to that riser was a control valve wheel controlling a very thin steel gate that must have been inside that concrete pad at the bottom of the riser (likely 15 feet under water). It blew out and we have the twisted, thin remains of the gate.
The riser rested in a 42" culvert running under the earth dam and emptying into a natural creek. From the outlet end of the pipe to the riser end is maybe 60 feet? The riser rested probably 25-30 feet "offshore." The control valve was never operated once the pond filled 13 years ago, and I doubt it ever could have been as the wheel was up in the air maybe 10 feet above the surface of the pond so even a man standing up in a boat could not reach it.
I forget without looking if there was a ladder on the riser, but still, a person would have to exit a boat to get onto the ladder.
The pond is naturally spring-fed for maybe 60 gallons a minute (pure guess), so when the pond was built 13 years ago, I guess when the pond was ready for filling, they adjusted the opening of the control gate until they saw that the lake was staying at an acceptable level (maybe 6 vertical feet from the top of the dam.
The level of the pond never changed in any heavy rain and there is no flow of surface water into it; just the occasional flow from a grassed lot when there was a very heavy rain. Water never flowed into the trash catcher.
Another source told me that a plastic sleeve inside the metal riser would not work because concrete will not stick to the plastic, but I could wrap it in roofing tar paper and the concrete may stick to that. One contractor we are talking to says a siphon system would have to be bored into the pond.
I haven't seen any designs on anything. We are waiting for a young, skinny guy to crawl into the culvert with a strong flashlight, yardstick, and cell camera to get a good look at where the water is coming into the culvert now in order to assess if the culvert and riser is anywhere close to a clean break.
Ideally, I guess we would like to use the siphon system so there is nothing mechanical to fail in the future, but one contractor is talking about boring to install it. I don't know enough to question why we can't use the existing culvert to run through the dam. If someone here can explain why we can't, I would appreciate it.
