Pond Boss Forums POND CONSTRUCTION Building a dam Best way to keep spillway from washing out?

I have a small 1/2 acre new pond in an area with quite a bit of watershed. Sometimes we get so much rain that my 12" pipe can't handle it and the water fills up and goes over the emergency spillway.

What is the best and cheapest way to keep the spillway from turning into a grand canyon? I've already got some pretty big gullies from the last heavy downpour.

I was thinking about using my box blade (no FEL) to smooth out the gullies into a rounded channel at the back of the dam and then fill it with stone. Good idea? What size and type stone would stay in place and slow the water down to prevent erosion?

Thanks...

I worry about anything that restricts emergency water flow. Trash hanging up on rocks scare me. Is there any way that you can concrete it? I know a guy who actually put some big pipe in the overflow to handle emergencies. However, those somewhat washed out.

Joe, if you don't have the funds to concrete it as Dave mentioned above you can widen it and make it as flat as possible. The more you can spread the water out the less it will tend to cut and cause the gully erosion. You have to get good vegetation on it as well. This is usually the toughest part.

joerocker:
Your idea about filling in the back of the dam with stone is a good idea. Use stones no smaller than 12" and wrap a chain link fence around the stones. If you get a chance to add topsoil and get grass planted then stake square hay bales across it to slow done the water enough to let your grass establish. If you need more information or would like to talk to me directly you can call my office at 1.800.822.3478 or email me at [email protected] and Sheri will set you up a phone appointment. She is in the office from 8 to noon monday thru friday.
Otto

joerocker,
I seeded my spillway with rye and fescue which held like concrete the first year but before it re-seeded itself it started washing out so I had to sod mine with bermuda. It is working great now. No way (almost) it can wash out.

I've had good luck with cement soil. Just till up the spillway, dump about an inch of dry portland cement, and till it in about 4" deep. Assuming your soil is at least a little bit damp, pack it down good by running over it with something heavy. It's the best of all worlds. It's very hard to wash out, yet grass will evenutally take it over.

Thank you all...

The thing with mine is this: There is one emergency spillway on each side of the dam. Each about 15' across. It's pretty flat for the 50' or so that makes up the dam. Then it drops...like 3' in 3' to the neighbors property. What happened, the builder dug me another dam core because I was convinced that the dam was leaking. So, now instead of a nice slow gentle slope to the neighbors property, I now have a LONG gentler slope and then a drop off. I want to fix the drop off "cliff" and keep it from eroding into canyons.

I want to go as cheap as possible...I like the "cement soil" idea! Though it would seem to be a LOT of bags to cover the 1,500 square feet I will need. Anyone know how many bags to cover 1" at 1,500 sq ft. bobad? 125 maybe?

I guess I could probably get away with less bags and just make it thicker, if I only do the steep slope?. I'll have to think about it...

Two Quickrete bags is roughly one cubic foot or roughly 12 sq. ft. at 1" thick when they are MIXED. At that rate, you would need 250. I am guessing that 1" dry wouldn't be too much of a difference, but I don't know for sure. If anything, you would have more coverage and can take back the extra bags as long as they don't get wet.

I would just pay to have a cement truck come out and poor 4 inches of reinforced concrete on the steep slope areas. Most concrete companies will deliver a minimum of 4 yards in our area for a cost of about 260$. I like Bobads idea, I think I might try that myself but I think it would be a waist on a 45 degree slope as you have discribed. A 4in thick 6ft wide x 50 ft long slab is about 4.5 yds of concrete. Reality with rebar and the beer you have to buy your buddies to come help is going to run you about 350$ to 400$

joerocker,

The pure stuff (Portland cement) goes a long way. Each sack can cover around 8 square feet 4" thick. If you till it in shallow, it can be stretched a lot farther. I think I only used 3 sacks on a sloped 20x20' driveway that kept washing out. Since a spillway has little or no wheeled traffic, I think you could till in 1/4" of Portland to a depth of 1" and get away with it until the grass is well established. It all depends on the water depth and speed. If you can keep the water shallow (which prevents it from gaining speed)it's not critical. If the water gets deep and gains momentum, nothing less than high quality concrete will keep it from washing out.