Pond Boss Forums POND CONSTRUCTION Selecting a site Pond build in open field - questions

Good Afternoon!

Really glad I found this forum. Lots of information on here!

I'm looking at digging a .25ac pond in my field with a depth of 12-15ft in some spots. Field is cleared and no rock/gravel here so "should" be an easy dig.

All dug material will be used to create a privacy berm around the front of the pond which faces the road.

I'm going to do some test digs soon but my contractor thinks we'll hit mostly clay or silty clay in this area. Really hope we hit some water to fill and provide clean water into it.

Contractor figures around 2 days with a 336 excavator running and a dozer to move the dirt onto the berm.

The location is a natural dip in the field where water accumulates in the spring melt or heavy rain and naturally flows away from the site. Other than that it's dry all year. I'm hoping we can just place riprap at the low end that the water will spill over as needed in melt or heavy rain. Not sure we'll hit a spring. If we do we may need to do something more elaborate to control the water level and overflow.

I had a couple questions:

1. Would I need a dam in this instance if we're just digging out the existing dip in the field? I'm hoping water will just go in/out as it does now and the pond will be in the middle of that flow.

2. For the privacy berm, would 15ft be enough space from the pond edge and where the incline of the berm begins? I'm hoping that will allow for enough space to walk/drive around the pond but also be enough distance to not have a bunch of silt get washed back into the pond until we get some vegetation on it.

3. Does 2 days sound reasonable to build a .25 pond that deep with an excavator and dozer running?

Please let me know your thoughts.

Thank you

"Really hope we hit some water to fill and provide clean water into it."

If you hit a spring, then the level of the spring (or the potentiometric surface) will ALWAYS control the water level in your pond - unless you seal off your pond from the connection to the spring. This DOES NOT mean that if you hit a spring 3' below the surface, then your water level will be at 3' below the surface.

[An easier analogy to understand is drilling a water well. You might hit your good permeable sand/gravel zone at 100' and the aquifer provides a static fluid level in the well at 80' below the surface. That may be an acceptable result, but you cannot increase the water level by any manner of smart engineering.]

If you utilize the local clay to seal the pond from the spring, your pond will now fill with the surface flows of water and drain due to seepage and evaporation.

Do you know how to read a topographic map and determine the "drainage area" above your proposed pond location?

You absolutely need that information to determine the correct answer to your questions about the dam.

Thanks for the info on the spring. As for drainage area, there is no watershed going into this pond. Basically there is a ditch to the north of the pond so really the only surface runoff would be from the surrounding field that isn't going into the ditch or blocked by higher ground such as the driveway. It might be 1-1.5 acre of field that would provide runoff into the pond. I've only ever seen any standing water in this low area during the spring snow melt and after a ton of rain. It disappears quickly. So I'm hoping just a spillway at the end of this dip will be sufficient?

I'm also curious on questions 2 and 3 around the spacing between pond and berm and the time to dig the pond with the excavator and dozer.

Thanks

"2. For the privacy berm, would 15ft be enough space from the pond edge and where the incline of the berm begins? I'm hoping that will allow for enough space to walk/drive around the pond but also be enough distance to not have a bunch of silt get washed back into the pond until we get some vegetation on it."

Yes, 15 feet should be fine for a driving path around the pond.

If you are worried about the silt, I would grade a reverse slope from the edge of the pond to the start of the berm. (The pond edge is higher.)

You could also have a slight reverse slope on the top of the berm, so a heavy rainfall would flow away from the pond and most of the erosion would be on the backside of the berm.

"3. Does 2 days sound reasonable to build a .25 pond that deep with an excavator and dozer running?"

2 days sounds reasonable to me with a 336 excavator and an appropriately sized dozer. (I am not an expert!) UNLESS you hit a lot of wet, sloppy material. Wet sand will not come out in heaped buckets and cannot be spread with the dozer. This problem could double your time (or worse). The excavator can do wet clay, but the dozer will also have trouble with that material.

I have some similar ponds planned for my farm. I am getting some more soil samples from the NRCS drilling rig to finalize my plans.

I would highly recommend that you get some soil samples BEFORE moving in the heavy equipment. Ideally, you want to get a few feet deeper than your projected 15 foot max. depth.

I would also plan the project for the driest time of the year to avoid groundwater as much as possible.

Reading further this definitely will be an excavated pond so I'll have to rely mostly on a spring, spring runoff or rain to fill it up. There really isn't any watershed to go into it.

The big problem with a spring filling a pond is that if the spring is below the water level of the pond you cannot install a one way valve on the spring. When the water pressure in the ground is less than the water pressure in the pond the pond will drain........

That type of pond is also called a groundwater pond.

On one of my spring fed ponds, I used a backhoe to core the areas with springs up to the full-pool level of the pond. Only when the pressure in the ground water allows the spring to flow/seep over this core, will it fill the pond, and it prevents the water from leaving the pond. In essence, it is a one-way valve. So far it has worked very well, although in last year's drought, that pond did drop two feet. My newest (incomplete) pond also has springs and I am not planning to core in front of them. I may regret this later...

Thanks. I had no idea that springs worked this way. I assumed water would bubble up and fill the pond to ground level!


Good to know. I'll report back what I end up finding after digging a few test holes.

"Thanks. I had no idea that springs worked this way. I assumed water would bubble up and fill the pond to ground level!"

It might do that Frogger!

But it might not, that is why the test holes are a good idea before spending all of the money on constructing the pond.

Also, some springs are seasonal. You could have a water level during the wet periods where your pond is full and water is going out of your outlet pipe. However, during the dry periods your pond could drop to the elevation of the spring at the point where it intersects your pond.

If safe, I would leave your test pits open for a year and observe the water level.

However, even that may not indicate the expected water level of your completed pond. Once you construct the pond, the spring will now be losing water to evaporation and seepage. This should not affect a high-volume spring. If you only have a low-volume spring connected to the pond, then your annual pond level will average lower than the water level in your test pits.

Frogger:

My personal pond is a ground water pond. Some years it is flowing out the overflow. (it has surface water running into the pond during times of heavy rainfall and high ground water levels) Most years it's running about 3'-4' below full pool in the Fall.

Right now it's down 7 vertical feet and it is less than half the size it would be at full pool.

I am seriously contemplating putting in a well to keep it full.....