Originally posted by Rangersedge:
Making plans to finish those sediment basin dams later this year. I had a couple people with some pond construction experience advise me not to bother with a keyway on them since it probably wouldn't make any difference and a little seepage under the dam wouldn't be a problem since it would just go into the lake then anyway. I'm a little leary thinking what's to prevent a little seepage from becoming a big seepage. Soils are mostly clay and seem good for pond building. What are your thoughts? Would you try to save a little time and money by not doing the keyway on the sediment basin dams?
Rangersedge, I have not seen many on this forum discuss a sediment basin, and there are probably many different types for many different objectives...not sure exactly what your's will be designed for. I've been off forum for a while, but your post caught my eye, as I built a sediment basin in the upper end of my pond. My pond receives pretty violent run-off from two creeks during rainy season. I built mine to create an upstream catch basin to slow down the water so it can drop its load before entering main pond body. I constructed dam with a keyway for strength, material was rock mined out of upper end of pond. Rock was perfect cause it also filters water before level gets above top of dam. Key way was excavated out about 6 to 8 feet and we partially filled the bottom with as many old concrete bags me and my neighbor could find (about 50). Rock was then pounded in using excavator bucket (initially mixing w/ pulverized concrete at bottom) and then built up graded and surveyed in so that center portion was below high water line.....see pics. I dont think the concrete really added much, but having the structure extend beyond pond bottom is the real strength. It held up to some real big flow this last winter.
we had a record rainfall this year (55-inches plus) and it did a fantastic job holding gravel, sand, and some silt out of main body of pond. now i'll need to hog the basin out in the fall before the rains come again, but hopefully wont have to do it every year. if i had to do it again i would have put it a little further out in pond. in dry season (like right now), it also provides a bridge to get from one side to the other.
