One of our properties has the remains of what used to be a pretty nice pond, but at some point before we owned it decades ago, the dam blew out and now all that is left is the washed out dam and a small area maybe 50' across still holding 3' or so of water. Just hired an excavation contractor to come in; clear and grub all the trees and brush, excavate and re-shape all of the banks, dig out and properly rebuild the dam, then install a new overflow spillway.
When finished it should be 1/2 - 3/4 acre 10' - 12' deep. Said he is going to get started soon, hopefully I can be stocking fish by late summer.
Steiny:
I wouldn't rely on an overflow spillway as the primary means of letting excess water out of the pond. No matter how well you seed it, water will erode the soil, causing the dam to blow out again at that area. I would use either a plastic smooth wall overflow pipe or an automatic siphon system as a primary water removal system and the grassy area as a secondary emergency system. The NRCS in your county should be able to help you figure out how large the primary overflow should be. It needs to be calculated on the watershed that feeds that pond area, and calculated for a 500 year rain event. Common steel corrugated galvanized "culvert" pipe will last 20 years then it needs to be replaced.
Many, many contractors can move dirt. Few can properly build a pond that will hold water.
Here's some cliff notes on building a pond that will hold water and not a leaky pond.
1) Make sure the watershed that feeds the pond is adequate.
2) When the pond is dug, double check the soil and make sure that there is enough clay to seal the pond basin from top to bottom.
3) Compact the entire pond basin from top to bottom with a sheepsfoot roller in 6"-8" lifts and have a total of 3 to 4 total lifts compacted. Dozer tracks or excavator tracks will NOT properly compact the soil. Tracks are made so the heavy equipment will float on the soil and not sink, the opposite of what you are trying to achieve.
4) Make durn sure that the dam has a properly constructed and compacted keyway tied to impervious soil.
5) The dam freeboard between primary and secondary emergency spillway is determined by the watershed, and should be at least 12"
6) Make the slope in the pond no steeper than 2:1 for clay soils, and no steeper than 3:1 for sandy soils. The areas that you will walk to and around the pond I would make no steeper than 4:1 and 6:1 is even better.
7) Plan your humps, bumps and rock piles before the pond is dug, as a more varied bottom contour is more attractive to the fish.
8) Plan your cover placement for the fish before the pond is completed, and install it before it starts to fill with water. Rule of thumb is 20% of the surface area of the pond should be cover for the fish.
9) Finer, denser cover near bedding areas, more open cover away from bedding areas for the larger predators to utilize. Make sure you have some finer cover in the deepest water for the winter, or a great majority of young fish will be eaten during the winter, leaving few to survive for the following year.
10) Depending on the size of the pond, (because you are constrained by the side slope) I like to see a minimum depth of 12' for a pond here in Indiana, and 18' is even better. That way you can lose 4', 5', even 6' of water in a drought year and not have issues with low water levels during the winter. All ponds start to fill up with dust/dirt/muck the minute construction ends. There are ways to mitigate that, but if the pond is only 10' deep to start, in a few years you can have a pond that is only 8' deep or less, and that causes management problems.
If the contractor does not know what a keyway is in a dam, or tells you that you can properly compact ground with tracks from heavy equipment, either look for another dirt guy, or get a contract in writing from him that if the pond leaks (drops) more than 20% of the evaporation rate for your area that he will come back and fix it at no cost to you. Fixing a leaky pond costs just as much as digging one in the first place, so it's imperative that it be done right the first time.
The only way that tracks on heavy equipment can compact the ground properly is if you are starting out with clay that can be used to make pottery and doesn't need compaction in the first place.
