Pond Boss Forums POND CONSTRUCTION Building a dam spillway questions

Grass or rocks I have heard both sides ... Better grass not rock and Better rock it not grass? Thoughts?

I prefer natural ground running over grass.

Me too. Unless they are held by cement, IME rocks wash our easier than good sod. Unless you're using rocks that are way bigger than I 1) want to place by hand and 2) want to run a mower over.

I have one of each, the grass one backs up a pair of 6" overflow pipes and the rock/concrete one has a lookout, well at least during the sunny days.

Had I, it to do over, I would go with grass, the concrete masks problems in my experience.

Grass- It is easier to work on if you need to.

What do you want it too look like when it'd done? I have grass in mine and mow it a few times a year. When there is no water flowing through it, it's a nice grassy area. Mine is very shallow and almost level, so when there is water in it, the water flows real slowly. When mowed, it's a nice area that blends into the rest of the landscaping and looks real nice.

Eddie

The grass needs to be as thick as the grass on a golf course.

That is hard to do but that is the best.

After the pond is full it can be irrigated with a slamm gas pump.
That would really let it get established.

Dave be sure to check my spelling.
Thanks

Done, but I don't know what a slamm gas pump is. I have spell checking working on mine but don't know how or why.

If you are using the spillway to control the TSEL of the lake I would suggest Rip-Rap, a quick calculation could be performed to determine the velocity of the outflow at some storm event, say 100 yr. then the Type Rip-Rap could be selected. If the velocity is less than 7 fps Rip-Rap that can be hand place will do just fine in GA thaat would be Type 2 Rip-Rap. It will actually keep down on any erosion.

Conversley if the spillway is an emergency overflow then grass would be great!

I have a 7 acre lake (pond) that has a 100ft 36" drain pipe through the middle of the dam, unfortunately one of the 20 ft sections collapsed and the enitre 100ft of plastic nneds to be replaced. Would it be better to just dig up the pipe and refill and use the emergency overflow by lowering it to the desired watrer level (about 2 ft) and filling this with rip rap and putting down filter fabric. My lake drains about 300 acres and the width of the emergency overflow is 24ft wide and 60 feet long.

IMO it might be cheaper but not better. With that much watershed I wouldn't want to rely on the EMERGENCY spillway as the primary drain.

Welcome to the forum TCW!

How long does plastic pipe last? I have never heard of the pipe itself failing, although I have heard of it collapsing due to inadequate packing of fill around he pipe.

Hello TCW and welcome to Pond Boss. Keep reading and you'll get more feedback.

RAH, if I'm not mistaken Mike Otto wrote an article that appeared in Pond Boss several issues back that discussed the advantages and disadvantages of the various pipe materials. Does anyone recall that issue or have any feedback?

I plan to lower it to the highth of the old overflow, it will be 12 feet wide versus the old overflow box of 4 square feet with a 36 inch pipe

You are absolutely correct, the old pipe had not been packed suffciently along the sides allowing the pipe to flatten out more than 30%, it took 22 years for it to finally collapse.

Non-Dec 2008, "OVERFLOWING WATER KNOWLEDGE…CHOOSING PIPE"
Otto tells what to do when drain pipes fail. Includes types of pipe, pipe terms, and varities.

Google " turf reinforcement mat" lots of geotextiles available for this purpose. Inexpensive, easy to install, easy to maintain. I think Brettski used some. Contact one of the manufacturers and they'll tell you what you need.

That Turf reinforcement mat is something I might need depending on the route I go next year on my pond... assuming I have to dam up the creek and need a spillway.

Welcome aboard. Glad to have you.

If I was going to dig up the pipe and remove it, I would replace it. Half of the work is done---Ric is leading you in the right direction. That may be to much water for the emergency spillway.

Assume this lake drains approximately 300 acres and the 100 year rainfall would equal 20 inclhes in 6 hours, how wide would the overflow need to be and how thick would the rip rap need to be?

Damn wide----deep too! Mine is 16 feet wide and 2 feet deep. My watershed is 30 acres and a 10" rain in 6 hours put the 1.5 acre pond within 6 inches of topping my dam.