Turning Drought to Advantage: Dam Rebuilding?

[Dobber30052]

Hi all, we are in drought mode again this year, which might be turned to my advantage...
My dam was reconstructed several years ago by someone else and only has a spillway for drainage. Problem is, the spillway has eroded and is unsightly. With the water being so low, I have been tempted to install a pipe for overflow (if we ever overflow again!!), but, I would sure hate to screw it up worse. Please look at the photos at: <A target="_blank" HREF=http://kevinkaley.home.mindspring.com/Temp1.htm>Dam/Spillway pics</A> and advise.
The standpipe is useless as far as I can tell, other than it still closely represents spill level. I have some 12" pvc that I can use. In a nutshell, the "plan" right now would be to bust out the existing concrete, trench for new pipe, install a tee with extension below (drive the lower part into the pond bottom, maybe a foot or two), adjust the height to spill level, connect the horizontal drain part on a slight tilt, then bury the pipe to match the rest of the dam.
That would be the first and main part, after that I can consider piping and burying the rest of the drain down to the lower pond!
Any ideas, tips, etc are appreciated!
Thanks,
Dob

 

[ChuckinVA]

Kevin,

First of all I love your home page ! Good job !

I have absolutely no experience with dams. That being said, I would be concerned about digging around even with the water level on your pond down. It would take just a small mistake to drain your pond completely.

What is wrong with the existing standpipe ?

Looks like the concrete was put there as a overflow for high water that could not be released fast enough through the standpipe. I would think you would want to maintain that as otherwise you would have erosion problems during high water times ( If / When we get high water again ) Just my thoughts.

 

[karmakanic]

Hi Dob,

A couple of thoughts about using the plastic pipe. You will need to construct some type of barrier to keep water from seeping along the sides of the pipe. With metal pipes the normal practice is to weld a square plate around the pipe, perpendicular to it's axis, located 3 or 4 feet into the dam bank on the water's side.

I would also be concerned about erosion of the plastic over time from the dirty water that's going to be flowing thru it. Also keep in mind, plastic does not like the sun, will the top of the pipe be able to withstand UV rays?

You don't want to have to redo this job anytime in the future. I think I'd be more comfortable with a steel pipe, if I was gonna use an overflow pipe.

Personally, I don't like the looks of an overflow pipe. They look more out of place then a beached whale when the water's below full. And here in Texas, the water's below full more often then not.

I attached a pic of how I made the spillways for the ponds I've constructed. However I'm lucky, or cursed perhaps, to have heavy clay soils. This method won't work if you've got porous soil in your dam. Basically my spillways are constructed of large boulders laid like flagstone with a clay base and clay used as grout. The boulders I used average 2 ft thick, but you don't have to use ones that thick. I did it this way cause I had the rock available, I needed to be able to drive the tractor and dozer over these spillways, and I hate concrete spillways even more then overflow pipes.

Good luck whichever way you go.
Dave Perry

 

[Dobber30052]

Chuck, thanks for the kind words about dp.com, it needs updating badly - no tractor pics!
The concrete standpipe was abandoned some time ago. A water main in the street directly in front of the pond has burst twice as I understand, and washed the dam out both times. the 2nd time, the property was owned by the son of the prior owner, and the son was a cheap SOb - you can tell everything around here that he had a hand in. This dam/spillway is one of them.
At overflow stage, the concrete pipe is covered, but only fills up, it does not drain. I suppose I could investigate further, but it appears and I have been told it is of no value, other than for something to cast at.
Dob

 

[Dobber30052]

Dave, thanks for the insight. I have the pipe, and maybe it's me being a cheap SOb (see above) that prompted my potential use of it! We're not talking much here, if I move ahead, I think I'll get steel.
I too would prefer a spillway, maybe I should consider just replacing it, but the soil in the dam is more porous than not having been farmland many years ago and I'm afraid it would revert to the ugly mess I have right now in short order. The catch here is that I need something "solid" to prevent erosion, but when something "solid" (like concrete) goes in, the erosion move under and around the concrete, which to me makes for harder repair. The other issue is that the drop on the back side is 6-8' from full pool, rgth now there is ugly concrete leading most of the way, but again, it has eroded around the edges and who knows how much underneath. I think to have a "proper" spill, I'd need to backfill A LOT, perhaps invading the fenceline nearby.
I'll keep studying...
Dob

 

[Dobber30052]

Is anyone familiar with a siphon system? It was recommended on another site. <A target="_blank" HREF=http://www.ponddampiping.com/syphon1.html>Here's the idea.</A> Sounds functional, both mechanically & aesthetically. Any first hand knowledge out there?

Dob

 

[ChuckinVA]

Dob,

If this is going to be a long term repair, I'm not sure I would recommend the steel standpipe as Dave mentioned. We have a 9 acre lake in our neighborhood that several years ago the steel standpipe which was a corrugated pipe rusted out about 4 feet below normal pool for the lake. The lake level dropped 4 feet overnite. The neighborhood association had to have it repaired and when they did they went back with a concrete pipe. No rust ! Good luck with the repair !

 

[karmakanic]

Well,,,I wouldn't recommend corrugated pipe either. More like something with 3/8" or better wall thickness.

The soil conservation lake at the back of our place has been in place for about 30 years with a steel pipe overflow.

Dob, that link you posted of the syphon system looks really interesting. It has the real advantage of not emptying the pond if something happens to the piping. As Chuck's experience shows, that's the real danger with an overflow pipe system. And it shouldn't be too hard to artfully hide the pipes, which satisfies my other objection to pipe overflows. As long as it can handle the volume needed, I'd certaintly look into it if I was looking to build another pond.

Dave

 

[Dobber30052]

Thanks Chuck & Dave, at this point the siphon system seems like a no brainer. My only concern with it would be if (when?) we switch from drought to monsoon. I've lived here for 4 years and have seen it overflow 4 times. the old timers here, remember it constantly running over, but the county grabbed many thousands of gallons when they put in the storm sewer in the ditch at the head of the pond. I intend to grab some back by installing a small catch trap with pipe from the ditch to the pond, but that's a while away. Anyway, When the weather system does change and we have abundant water, could I exceed the flow of the pipe? Well, I know I COULD, but how likely? I have ZERO knowledge about flow rates etc, and could not even begin to guess how to start to figure that. Now having said that, I cannot imagine enough water to max out an 8" pipe, am I paranoid?

Thanks again,

 

[_RaT_]

Interesting pictures. Out here in California we simply do not get rain all summer long so we are in a drought mode every year, except that we have mountains covered with snow that continue to give us some run off almost the entire spring to fall into some fairly large reservoirs.
Out here, metal pipe is very rarely used for drainage of any kind. There are better alternatives unless your dealing with large internal pressures. ADS piping works great and comes in many sizes as well as being available with smooth inner walls and corrugated exterior allowing easy installation and will still flex. Its crush strength (ADS smooth wall) easily exceeds corrugated steel, never rusts and has many fittings available as well. All the highway projects use it anymore. The reservoir we put in nearby uses a great lake drainage system. It pulls off the bottom to rid itself of the least oxygenated water, is self leveling which is easily adjustable, also can be used to act as a surface skimmer and has a dam gate setup allowing one to easily lower the level of the lake at will in 12" graduations. The bottom pipe is only 6" but will keep the lake at the desired level unless a large inflow occurs from a storm. At that point the skimmer will pick up the excess. All of this dumps into an 18" pipe, that pipe is ADS. The 6" is schelude 40 PVC. If your really curious, I could snap a few pictures of it to better explain the design. It works very slick. Rat...