If you choose to drain and de-muck, I can give you my experience...

1/4 acre pond, originally 10 foot deep, after years of filling in the water was only 2 foot deep.

Broke the dam in early June with a mini excavator and managed to drain all but about 100 square foot in a low spot (water was about 10 inches deep.

The pond hole set while the weeds took hold in the muck, before the slightly dry summer was over the weeds where 5 foot tall and the ground could be walked on but it would pump under your feet even with 1 inch wide cracks that went 1 foot deep.

My dirt guy attacked it in October of that year by cutting the dam further with a track loader so that his track loader could drive through it then he started at the original shoreline and started removing the muck and putting on the back side of the dam. It did not take long for it to get real soupy again. If you would try and walk on the muck pile on the back side of the dam, you would sink and not return (or at least sink up to your hips I suspect). The muck at it's deepest was 8 foot thick and we found the original clay base and stopped there. So long as he dug the muck out as he went into the depths of the original pond, he kept his loader from getting stuck.

Once the muck was all but gone, he scavenged enough clay from the perimeter, making the banks steeper, and filled in the break in the dam. He did this 6 inches at a time all the while compacting with the tracks. Not exactly the most risk-free approach, but it work real well. The extra muck that did not nicely fit on the back side of the dam was spread out in a nearby field to dry, all clumpy and ugly. It dried well enough to move and work into some low areas of the surrounding yard by the end of the summer. It was anywhere from 1 to 2 foot thick.

The pond did not fill back up until the next late spring and only the top foot or two of the backside muck could be worked with a rubber tired skid steer. It would pump under the weight of this midsized skid loader which worried the operator imensly because the muck,in places, was 10 foot deep. By the end of the summer and 4 visits from the skid steer the muck had been worked and smoothed out well enough for me to grade with my 8N tractor and spend countless hours with a rake removing rocks...I have a lot of rock at my place. Then I seeded with a fescue/rye mix and it turned back into a pond, eventually. Luckily, we did not get a lot of heavy rains that summer because most of the summer the dam was bare dirt getting worked and worked again.

This work cost about 4.5 to $5000 and included the breaking of the dam, all the de-mucking, the 60 foot of 15" plastic corrugated drain pipe with trash guard and install(the dam was extra wide now), the skid steer work, and grass seed. I don't knokw how to scale the cost up for your size of a pond, but the steps and time frames should still apply.

My many days of labor was free, but I still have nightmares about picking up rocks.

Right or wrong, that's how it happened!

Fish on!,
Noel