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#488446 - 04/11/18 12:23 PM Spillway or Drainage pipe??
trapsht Offline

Registered: 05/19/11
Posts: 22
Loc: Northern Illinois
After fighting leaks for a few years, I think my 1 acre pond is back in business. When we built this pond 6 years ago we never put in a spillway nor a pipe. After renovation and other changes, my pond has actually flooded over the dam twice now and I need to put in something to maintain water levels after heavy rains and snow melts. My dam is anywhere from 30-50' wide.

Is a spillway or a pipe the best way to go? My pipe plan was to trench down to my desired water level, place pipe and backfill with dirt. My spillway plan is to make a wide trench with my skid loader and back fill with rock or potentially feather it out and plant grass.

I have a skid loader, but would have to rent an excavator to put in a pipe. Thoughts on any of this?

#488448 - 04/11/18 12:36 PM Re: Spillway or Drainage pipe?? [Re: trapsht]
BrianL Offline

Registered: 03/31/14
Posts: 781
Loc: Paris, TX
My thought is both. DO a bottom siphon pipe at your desired level and an emergency spillway 6" above that level.
1.8 acre pond with FHM(gone), CNBG, RES, HSB, and LMB
Trophy Hunter feeder.

#488449 - 04/11/18 12:36 PM Re: Spillway or Drainage pipe?? [Re: trapsht]
canyoncreek Online   content

Registered: 05/07/13
Posts: 1965
Loc: West Michigan
Before your disturb your dam, where were the leaks and how did you fix them? What is typical water depth up against the dam and how much does it fluctuate? Pictures help too if you can attach them.

#488450 - 04/11/18 12:42 PM Re: Spillway or Drainage pipe?? [Re: trapsht]
RAH Offline

Registered: 05/17/09
Posts: 4283
Loc: Indiana, Boone County, 25 mile...
My preference is to install a pipe (when water is low) that has the steepest slope that is practical and use an anti-siphon device (so it carries the most water when full). I also have an emergency spillway at an elevation above the top of the pipe that only gets used during severe flooding. Having an earthen spillway, even with rocks, can get eroded if used continuously or excessively. The pipe needs to be packed well with clay soil to prevent leaks around it. I personally spend the extra money on gasketed schedule 35 PVC sewer pipe, but many use double-wall plastic culverts. A trash guard will help prevent clogging.

#488453 - 04/11/18 12:57 PM Re: Spillway or Drainage pipe?? [Re: RAH]
trapsht Offline

Registered: 05/19/11
Posts: 22
Loc: Northern Illinois
I'll try to post some pics tonight. Not sure where the original leaks came from. I drained the pond a few years ago, and had it dug deeper and smoothed in anticipation for clay. All of the excess dirt was packed on the backside of the dam(dam is very big now). Long story, but the clay never happened. I let it fill back up and dug a few trenches from higher ground to direct rain water. As a result of all this, it now holds water. I still think it fluctuates with ground level water, but I'll take it. Most of last summer it was at the top of the dam level.

Water depth at the dam goes from 18-10 depending if its at flood stage or not. Ideally, it should be at 10-12 ft.

I'll have to research a siphon pipe. I was just going to lay down a pipe horizontally in the trench. I mostly just have to deal with big spring rains and snow melt. Right now its at a good level, but spring rains are around the corner

#488460 - 04/11/18 02:40 PM Re: Spillway or Drainage pipe?? [Re: trapsht]
Quarter Acre Offline

Registered: 06/10/16
Posts: 963
Loc: West Central Missouri
A pipe AND an emergency spillway is a good way to go as it balances money spent, effort and results. There are bagillions of ponds out there that have a "low spot" in the dam as an overflow that do just fine. I would be willing to bet that the watersheds for those ponds are light for the pond's sizes. Adding a pipe to this scenario with larger more appropriate watersheds allows the owner to pick the size of pipe that allows pond drainage under normal rainfall/snow melt events while using the freeboard (distance from pipe to top of emergency spillway) as a catch basin so that the E. Spillway rarely gets used. The excessive water overtakes the drain pipe, but the pond will still hold more water until it starts to flow over the dam at the E. spillway. This reduces the E. spillways usage which reduces the erosion and allows grasses and such on the E spillway to recover before excessive waters are experienced again.

My 1/4 acre pond has an excessive watershed, a 15 inch doublewall corrugated drain pipe, 2 to 3 foot of freeboard and may use the E.spillway once every few years (cross my fingers). The pond was initially installed as a catch basin to reduce the flooding of the home and cattle yard. It does it's job and has been affordable.

The siphon type drains have many advantages...takes water from the bottom of the pond which is usually low in oxygen and high in sediments. If set up right, they can also be used as a drain to empty the pond. But, they may cost you more money, especially when installing in a filled pond. You'll have to check into the siphon costs for your pond's specifications to determine if its affordable for you. You can imagine the cost difference between a 15 siphon drain (what I would need) compared to a 6" PVC siphon drain for a pond with less watershed.
Fish on!,

#488481 - 04/11/18 06:46 PM Re: Spillway or Drainage pipe?? [Re: trapsht]
Redonthehead Offline

Registered: 04/03/07
Posts: 207
Loc: Missouri
Originally Posted By: trapsht

I was just going to lay down a pipe horizontally in the trench. I mostly just have to deal with big spring rains and snow melt. Right now its at a good level, but spring rains are around the corner

Great feedback from the others. I would suggest reading THIS THREAD regarding another forum member's recent issue with a short pipe through the dam. You will want to extend it down the backside to below the toe of the dam, in order to prevent erosion of the backside of the dam.

But then what diameter pipe is needed? I recommend visiting the county NRCS office to see if they will run a calculation for you.


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