Pond Boss Forums POND CONSTRUCTION Selecting a site 5 acre farm pond - DIY advice!

Hi everybody, I'm new to this site. There's lots of great information here! I'm hoping you all will chip in with thoughts for me as I embark on building my pond. Then I will post updates and hopefully can share my experiences to help others in the future.

We recently bought a wooded parcel of land in central Virginia and am having about half of the acreage logged. The plan is to dam a creek, which will flood 5 acres to create a central farm pond. We have an agricultural exemption from the county and already have a permit from the Army Corps of Engineers. We also have a buddy who is a civil engineer who is advising us on the design of the dam and the culverts, etc.

The creek more or less dried up last summer during the dry season, but the narrow gully where we plan to build the dam has a 160 acre drainage area - a LOT of water passes through during a good rain event. The pond is going to have to be split into two sections by a causeway as we need to get a driveway into the back section and the pond will bisect the property. The dam will be about 12' high and 250' long. The pond will be about 10'-12' at the deepest, but a lot of it will be quite shallow, so we'd like to plant up these areas as wetlands. And we're going plant up the edges and surrounding areas to filter runoff and to establish some native meadows.

I briefly spoke to a contractor who specializes in pond construction, and he spitballed $150k to construct this pond. That's astronomically out of our budget, so I'm planning to enlist a buddy who has an excavator and backhoe to help me.

We're facing several challenges and several unknowns, and I'm hoping your advice can help us out. Here are my initial questions:

1. We have shallow soil on the property and the bedrock is fractured shale. We've been told to avoid digging down at all, just to build the dam and let the pond fill. When digging the trench for the clay core, how far down should we dig? I've read you should dig down only until you hit bedrock. But what if that's very shallow?

2. After logging, do we need to strip all of the topsoil and remove all the stumps and fill them with clay? Or, considering the bedrock, do we just leave everything in place and see if it holds water?

Thanks in advance for your thoughts!

I'm not going to be able to advise much as I know diddly about pond construction, BUT pay full attention to the amount of watershed you have...160 acres is alot for a 5 acre pond. Or, at least, it is for around my neck of the woods.

My little 1/4 acre renovated pond has about 20+ acres of water shed and stays pretty muddy partly because of this. It will also fill in faster due to the extra soils washing in. The feeding ravine at my pond stays dry except for during rain events. Look into diverting some of that extra water to avoid the problems associated with too much watershed and consider createing some settling ponds above the main one. Your overflow/drain system will need to be bigger than the average 5 acre pond, much bigger.

Welcome to the forums!

Hoo boy if I were quoted $150k for 5 ac I'd sure want to know why. 160 ac drainage is massive and dealing with that can be a challenge so maybe that's what he was anticipating.

If you have too much watershed you can be in a tough spot. Even if you have adequately sized overflow and emergency overflow systems that can withstand the deluge, your water chemistry can go wildly out of balance every time you get a significant rain event. You're likely to replace the entire volume of the pond several times over each time it pours with adverse effects on your fish population.

Would it bepossible to place the pond adjacent to the creek and divert water during rainy events?

Thanks for the advice so far!

The watershed is coming in from two directions as two small creeks join together just before the spot where we're going to build the dam, so the pond is going to be L-shaped. The causeway is supposed to act like a silt barrier, so the smaller upper pond (about 1ac.) will likely be more of a wetland. Maybe we will look into building a second causeway to filter incoming water from the other direction. One good thing is that almost all of the drainage area is heavily forested and pretty sandy/rocky, so hopefully there won't be too much mud coming in.

In terms of the watershed, our engineer buddy seems to think we'll be ok with a large overflow pipe and a good-sized spillway, but I'm glad to know your concerns about the watershed and adverse effects on fish population. I'm going to bring that up with him and see what we can do about diverting some of that water.

I'm mostly concerned that the dang thing won't hold water because of the shallow bedrock!

Thanks again for the advice - this forum is fantastic.

Most of the pond building conversations that I have read talk about packing clay over any bedrock that they uncover. Pourous bedrock can allow water to seep out and cracks in the non-porous rock can do the same if the underlying soils allow that water to travel.

Your concern is very valid. My cousin had a small pond that had uncovered bedrock in it and, at best, it was an eyesore. A real heavy rain would fill it up, but a day later it was way down...so much so that fish could not survive the winter. This concept may be where alot of that 150K came from. Do you have clay availbale on the property?

Great advice. I'm not yet sure if we have much clay on our property because it's entirely wooded at this stage, but the county I live in has enormous amounts of high quality red clay, and as there's so much development I should be able to get a lot of it for free (but will have to pay trucking costs, which could add up).

As soon as we have the area for the pond cleared, I'll start ripping out stumps and will try to get as much red clay as possible delivered to the site so I can start spreading, filling holes, and building the dam.

I understand the stream bed will be great habitat for fish, so I don't want to fill that in, but as it's exposed fractured shale bedrock I'm concerned it will leak. Although I suppose the stream seems to hold water, most of the time...probably best to cover it with clay and build other habitat.

The consultant I contacted actually didn't know the site or the bedrock. He quoted about about $15k in tests (digging the core, testing water flow, testing soil), then about $150k for construction. I suppose he thought they'd be digging the whole 5 acre pond. I was shocked at the price, but there are so many rich people around here I suppose they make up most of his clientele.

I'm seeing a lot of references on the forum to NRCS (I had to google what that is). I do have their pond construction booklet. Do they provide any other resources that we might find useful? I'm not quite sure where to go regarding soil tests, etc.

Great book by Mike Otto. Just Add Water

15k for test digs. I would have told him to get back in his truck. I had a lagoon dug, creek smoothed out, and ¼ acre pond dug for 2500 dollars. I know prices change depending on the area but I will be damned if I'm going to let someone retire off me. Just my 2 cents.

We met with the NRCS initially. They provided great recommendations, walked the property and evaluated the watershed. In TX their limit is 1000ac watershed. They also only build new ponds. Ours is 1100ac and a renovation so ultimately we did not qualify. Their dam design for that watershed likely uses the Covid death rates models. They calculated a 200ft spillway. We went with the existing 30ft rock spillway and a 50ft emergency spillway. Had a huge flood and it barely went over the emergency spillway.
They can also provide assistance with controlling plants. Cactus and mesquites here. Crossfencing only. Maybe well drilling but we have saltwater.
Ultimately it's a government program. You submit an application and wait. They only make a decision once per year. You can't do anything until approved. Once accepted into the program you follow their instructions and you pay for everything. At some point they reimburse you up to whatever predetermined limit.
They have a annual budget and advised us to submit the application right at the beginning of their fiscal year...more waiting!
It was a mutual agreement the program was not right for us.
I definitely think they are worth talking to. Great ideas, local resources book, etc. Maybe their timeline aligns with your budget!

I thought the NRCS got out of the pond business.

Perhaps. We talked to them 3 years ago and not since.

They gave me a soil map. That was all, I had to do everything else on my own.

Thanks for all of this input. I’ve contacted my local NRCS office and am waiting to hear back. I’m also ordering Mike Otto’s book.