Pond Boss Forums INTRO Questions & Observations Pond Depth Recommendations

I'm getting closer to moving forward with my approximately 1/2 acre pond. I'm working with the contractor on getting the price down into my budget. I was able to get there but had to drop down in size to a .4 acre pond. The main cost driver is the amount of excavation material that needs to be removed from the pond and leveled afterwards. From the beginning I've been shooting for 25% of the pond to be at 15' depth, based on an article I read regarding Michigan ponds.

So here is where I'm looking for some input. The proposed pond has 2:1 slopes on all sides except one that will be 3:1 for swimming access. The sides go straight down to 15'. I've been thinking that I should consider an underwater island up to around 4' or 5' under water surface. This would allow less excavating in the proposed pond (less $), which with the savings I could use to enlarge the surface area of the pond. The main problem I see is that I wouldn't be able to maintain the 25% at 15' depth. What do you guys think? I'm also concerned with excessive weed growth on the underwater island - maybe I don't need to worry? Based on a test hole dug, I expect the water to have a stained appearance. Maybe this will help reduce weed growth?

Another question: given the pond slopes at 2:1 and 3:1, will bluegills have enough shallow water to use for bedding?

Here are a couple pics of the pond site pre excavation.

http://i713.photobucket.com/albums/ww139/NonTypicalCPA/IMG_2326640x480.jpg

http://i713.photobucket.com/albums/ww139/NonTypicalCPA/IMG_2325640x480.jpg

If you plan on walking into the water for swimming, I'd suggest a (small) 4:1 "beach" area for access. IME many people have trouble walking in & out of my ponds' 3:1 shallows. It's not a bad slope on dry land, but 3:1 slippery muck is another matter. Of course, my family prefers entering the water from the end of the dock (via a ladder) for swimming anyway (to avoid the slippery muck altogether).

I do not think BG will have trouble spawning in sufficient numbers in your proposed design. They may even utilize the underground island (if it's more towards 4') - it depends on water clarity IIRC.

I think a 15' "refuge" less than 25% of the total area would suffice if the pond is properly aerated wrt to both Summer and Winter regimens (deep and shallow, respectively, are how I try to aereate).

I don't have enough aquatic plants to have a good opinion on them.

Get it dug as deep as you can afford. Not only will the pond settle with time, it will also fill with organic materials and get shallower with time.

Also in Michigan its necessary to have additional depth to provide a buffer against fast changes in water temp and droughts.

I have never heard anyone complain about a pond that is too deep.

In Texas, it is almost impossible to go too deep. You can never really be sure of rain.

2:1 bothers me if there are any chances of kids or livestock getting in there.

I love the idea of the underwater island or hump.

I'm 30 miles South of the IN/MI border. The previous owner had the pond dug by someone that didn't know what they were doing and made the banks between 2:1 and 1:1, with the pond bottom dropping off 1:1 or steeper once below water level to get depth. When I bought the house 3 years after the pond was dug, it was impossible to walk down the bank without sliding down to the water (now this is on sand or sandy/loam). I was told that the pond was 20' deep and I thought that was O.K. because it was around 1/3 to 1/2 ac. and that I could get by without aerating during the winter because of the depth. I closed on the house right before Thanksgiving and took possession the end of February.

Come ice out I noticed a bunch of dead catfish, bass and bluegills. Massive winterkill. I checked the depth and the deepest spot was 8'. What happened was the steep slopes collapsed and filled in the lowest point in the pond, causing the banks to be even steeper, and the deepest part shallower. For the next 3 years I aerated and climbed up the banks on all 4's, that's how steep the banks were. The banks were slowly falling into the pond, and getting steeper every year. I didn't lose any more fish during the winters due to the aeration, and ended up renovating the pond last year.

We dug the pond with a slope of 4:1 for a swimming area, and with 2 different flat areas at 24" to 30" depth for spawning. We then dug a deep hole down to 22' below full pool at a steeper angle to get the depth, with the rest of the banks and underwater area at 3:1 slope. Once we hit 14' depth, the sand turned into clay and clay/gravel mix.

I went out on the pond this winter and dug some holes thru the ice to get a depth reading. With the pond 18" below full pool, the water was only 14' deep. I couldn't believe that the pond filled in that much, but since I personally took the depth measurements during the digging, and the stake was still on the bank for the 22' depth reference, the tape didn't lie. The pond filled in at the deepest spot roughly 6'.

So, I believe that unless you have concrete vertical walls, or are digging/blasting thru solid rock, the steep walls to get to a 15' depth won't work. Stay with a 3:1 slope, and whatever depth it ends up at, so be it. It's my opinion that if you make it deeper by making the terrain steeper, it will fill in within a very short time until a 3:1 slope is reached.

The areas in my pond that were dug to 10'-12' deep, that are surrounded by 3:1 slope are still that depth, they didn't fill in at all.

This past winter (the first one after the renovation), I didn't aerate, nor did I shovel any snow from the ice. Granted, the pond isn't at carrying capacity, but I didn't lose a single fish this winter due to Winterkill.

If you have pure clay (common in MI) the sides wont collapse as bad as esshup's did, but they will still fill in some. I would get as deep as you can with a 3:1 slope and have a 4:1 area for a beach, it worked good for my kids and they are 4 and 7 years old.

Thanks for the replys. I don't expect any clay in this spot within the first 10 feet. It's all water sand and I expect it will collapse to a certain degree, but hopefully not to the extent that esshup had. Sounds like the 3:1 slopes is what I need to stick with.

I was really surprised that it filled in that much. The clay that came out is a really sticky hard blue clay. When the excavator was in the thick of it, it couldn't break out a bucket full, it was that hard to come apart. The previous owner said that the dragline wouldn't go down any farther, and I can see why.

If you keep the slope 3:1, how deep can you get?

If your pond builder knows what he is doing he will use all the clay from the middle of the pond to line the sides of the pond all the way to the top and compact it with a dozer. I had sand down to about 8 feet and pure clay the rest of the way, and there was plenty of clay to line the pond with some left over.

On the steep side of the pond he even cut "steps" in the side and they did not collapse at all even though the slope was about 2:1

With his equipment max depth is 15 to 18 feet. He offered to bring in a long reach for a day, but that was going to cost over $3,000! I passed.

The problem I have with your technique is that the water table is within a foot of grade - unless he's got a new submersible dozer that I haven't heard about.

All you need is a pump, however my pond was dug in the fall rather than the spring. Late summer and fall are the best times to dig anything when the water table is lower.

A long reach excavator is not necessary for more than 15' of depth, unless there is no way the equipment can drive in the pond area. Excavators have extra wide tracks which provide a ton of flotation in mud and wet sand. Unless you have seen a couple ponds dug its hard to visualize, but when mine was dug all sand was removed first leaving a big square about five feet deep. Then the excavator dug progressive rows throwing the clay up to fill the areas vacated by the sand that was removed. In the end the pond was sealed extremely well so that I had a 20' hole in the ground for weeks without rain and only about a foot of water seeped in over that time.

I have a high water table also as my pond was dug in a floodplain.

The pictures of the digging are here on page 2
pond pics

Nice pics! Thanks for sharing. We havn't discussed pumping out water during the digging. However based on my test hole, it would have to be a pretty stout pump to keep up with the water flowing into the hole. I'll have to mention it to the contractor.

Nice clay by the way.

I used this pump to stay ahead of the water. If I ran it for 12 hr before the digging started for the day the hole was 95% dry when the excavator operator showed up. I rigged a 6 gal. outboard motor fuel tank to it and it would burn approx. 5 gal in 12 hr.

The water would filter thru the sand until it hit the clay at 8',then fill up the bottom of the hole, sounds like the same problem you will have.

Lessons learned:

1) make sure that it's on a stable platform & that the soil won't wash out from under the platform. (It WILL tip over and try to fall into the pond, trust me!)
2) use an innertube to float the suction strainer up off the bottom. a) it won't pick up sand and fill up the discharge hose b) it won't dig itself a hole in the bottom of the pond and get stuck. Because the sand packed discharge hose is so heavy you will be tempted to pick it up with the excavator bucket. It will work until 90% of the hose is up in the air, then it'll rip in half - been there, done that. I also tore the suction hose trying to get the strainer unstuck from the bottom of the pond. I couldn't wade in because of all the slop that washed in was like quicksand, in fact the excavator operator did at one time have to bring the bucket over so I could grab on and get myself unstuck......

We used a flexible 3" hose 50' long and then transitioned to 4" pvc solid drain pipe (the type with a bell on the end) to get the water away from the pond. I ended up using 30' of ribbed suction hose to get the strainer out to where the water was and keep the unit safe.

A buddy had a Mitsubshi motor pump almost identical to this one, and it tipped over on it's side and ran without oil - it cooked the piston, cylinder and rod before stopping. The Honda motor has a low oil shut-off. Even tho it has a warranty, it isn't much help when it takes 2 weeks to get fixed and the piece of equipment is sitting idle while the pump is fixed. I ran it the first day with Shell Rotella diesel engine oil, then switched it out to synthetic Mobile 1.

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_122115_122115

Because of the length of the hose on the aux. tank I had to keep the tank 3' to 4' above the pump or it wouldn't pull the gas thru the line.

The contractor was probably planning on using a pump at night and in the morning, it will probably be impossible to dig a pond without it. As esshup says, the pump will vibrate all over the place and even bury itself in the mud. A piece of OSB underneath it is a must.

A diaphragm pump is excellent for pumping the really muddy thick water when the hole gets nearly empty