Changing a pond spillway

joefromga · Apr 29, 2016

Pond school? Wow, you learn something new every day.

I know a guy that works in pond restoration and management. He says he can take a green pond and make it swimmable.

I figured if it was big enough it wouldn't overfill. . I guess it also depends on a lot of things such as the surrounding areas being able to absorb the rain.

All the ponds near my property are low to full. I never see them topped out but our soil is very absorbent. It rains all the time.

Creamer · Apr 29, 2016

joefromga said:
I figured if it was big enough it wouldn't overfill. . I guess it also depends on a lot of things such as the surrounding areas being able to absorb the rain.

Now that's a new one! If one keeps pour water in a container at some time it overflows. Where I grew up in the Dakotas we did not really have drainage, i.e. water ran to the bottom of the hill and stopped and then it was dry enough that the water evaporated to lower the level over time until it rained again. Then in the 90's they started getting more rain and soon one state highway in SD was under 17 feet of standing water in August and they had built a new road out around the pond that had developed. Then a few years later the water subsided and they rebuilt the road straight through the middle where it had been. Most of the rest of us have drainage though, i.e. it fills up and it overflows.

A real interesting story is Devils Lake, ND where a very large lake rose nearly 30' engulfing huge amounts of surrounding area. Devils Lake (North Dakota) - Wikipedia, the free encyclopedia

Creamer · Apr 29, 2016

Here's a better account of Devils Lake. Where the Roads End in Water: The Lake That Won't Stop Rising - The Atlantic

rekees4300 · Jun 30, 2016

rekees4300 said:
I'm facing a similar situation. My 1 acre pond has a 6" PVC pipe going thru the middle of the dam. ASAP I (actually a contractor) is going to remove it and install a 8" double wall at the end of the dam. In January, a large area by the PVC pipe broke loose and slide down the back of the dam. I think it was caused by water leaking around the outside of the pipe? Anyway, IMO, it makes more sense to place an overflow pipe in the stable ground at the end of the dam instead of just putting the new pipe in the same unstable location as the old pipe.

Yesterday the contractor did the repair. He verified the reason for dam slippage was the 6" PVC pipe leaking around the outside and said he has seen many other ponds with same PVC pipe problem. He removed the PVC and installed the 8" double wall (corrugated on outside, smooth on inside) at the end of the dam. Hopefully this change will solve the slippage problem permanently.

ovrszd · Jun 30, 2016

I've installed a couple hundred dual wall corrugated plastic pipes of sizes ranging from 12" to 54". I've never had one seep around the outside. That problem will be solved with this change you are planning. Whether the new 8" dual wall can handle the flow is yet another question.

rekees4300 · Jul 1, 2016

ovrszd said:
I've installed a couple hundred dual wall corrugated plastic pipes of sizes ranging from 12" to 54". I've never had one seep around the outside. That problem will be solved with this change you are planning. Whether the new 8" dual wall can handle the flow is yet another question.

Good to learn that from someone who is experienced, thanks. :thumbsup: I'm not worried about the new 8" handling the flow since the old 6" was adequate 99% of the time. The capacity of an 8" pipe is almost double a 6" pipe. Even with a 1,000 year flood like they had in West Virginia, I'm confident the new 8" pipe plus emergency spillway (20 feet wide) would be adequate to prevent water from topping the dam.

Pipes - Water Content