3)Pasture land that is cut through by a naturally eroded ditch. When looking at contour lines this looks like a great site to significantly reduce the required excavation. It seems that it is almost made for building a lake to my dimensions. This ditch only carries water during rains but quickly dries up once the runoff from about 400 acres of land that empties through this location. Obviously the main problem would be silting since most of the watershed to this area is cropland. If I interpreted the Illinois NRCS calculations correctly, the silt would fill in at a rate of about 0.5”/year. Since the silt would be more of an issue near the inlet, this likely would require periodic digging (every 5 - 10 years?) to maintain the depth of the pond. Rental of a long reach excavator might have to be in the ongoing budget.
There are ways to reduce silt. In the case above one should consider building the long narrow lake beside the ditch. Install a control gate and silt filter at the intake. This allows the excessive spring runoff to route around the pond. I believe your excavation estimates are a little steep. If one was to simply dig a pit that was 10'x 250'x 2300' your talking about 213k yards of dirt. The going rate around my part of the world is 1.25 to 1.50 per yard (Otto can confirm it has been 2 years sense I hired a dirt contractor). @ 1.50/yd = 320k$ max. Also you should never have to dig the pit to 10 ft because you can use the dirt that is removed to berm around the pond and store water above ground greatly reducing the amount of soil that has to be excavated. Storing water above ground is the most efficient means of building a pond of any type.
I have a friend that lives on a private ski lake community. Apparently there is a certain way they cut and slope the sides to reduce wave action. Here is a link that a person in the community wrote about their experiences
http://www.utoronto.ca/ski/water/faq/stmanmade.htmlYou can google “private ski lake justin texas” and see an aerial of the place. It has a ski lake and jump lake side by side. 12 homes in the community.
There are many sites and companies that specialize in this type of lake design you should consult some of them.
Good luck with your project
Rocky
