Allright. I have caught the bug. I have been looking at a sight on my 108 acre farm for over a year and am ready to build the lake. My friend just built a 5 acre one in Palestine and got my interest up. I borrowed a surveying instrument and shot some elevations. I can build a 9' spillway above grade and a 350' long dam and impound 7 surface acres. I met with the NRCS last week and although no money is available they will do some preliminary engineering for me. I have dug 3 test holes on the dam sight and believe enough clay is handy to do the project. NRCS agreed. I have a spring 100' upstream of the dam that will be under 7' of water that concerns me but the NRCS said this was a positive as it is being fed at an elevation higher than that from the surrounding hillsides. I am waiting on the NRCS to complete their engineering and am ready to proceed. Using google maps I calculate 100-200 acres of watershed.
Congratulations on your new addiction! Sounds like you have a good start. Keep us updated, ask plenty of questions, and take lots of pictures! Welcome to the forum Mark.
Am meeting with contractors over the next few weeks. The more I look at the sight the more confused I become. The back end of the lake will need some excavating to keep from being too shallow. The length of the lake is 900' with about 1' of fall per 100'. That means if the min depth is 2' I will need to excavate 2' from a 1 acre area and 1' from a 1 acre area. Is 2' too shallow over 2 acres of the back end? That means 1,613 cy per 1 acre/ft for a total of about 5000 cubic yards at the back end. This will be 7 acres total lake with a max depth of 9' in front of dam at grade. I have been accumulating some structure to put in the lake. Am planning on digging holes with my auger and cementing cedar trees vertically in the lake. Have also spotted a large pile of large tires and pallets for free.
Dam volume is 5,200 cy according to NRCS. I calculated 6,000. Core trench is 1,700 cy by my calcs.
I have some serious money set aside and believe it will be necessary.
Am planning on a 12" primary spillway made from smooth bore pipe with 2 antiseep collars made from 1/4" plate. I will control level of lake on downstream side of dam based on height of leg. Will put a tee on downstream leg allowing for potential to drain lake. Have a 8" gate valve in possession. Am debating placing valve 3' from top to lower lake level 3' in the summer to allow for planting of japanese millet. After millet heads and duck season is close closing the valve and flooding the millet.
Got scared enough I decided to do a Geo Survey. First picture is next to spring fed creek in centerline of dam. Do not have results back yet but 1-3' was sand, 3-5' was a water reservoir, at 5' started into a mix of clay/sand and at 8-13' looked to be very good clay, at 15-20' turned into pure white dry sand. My initial interpretation is that the 5' thick clay layer is holding water above it and as long as we do not break through that layer on the core trench I should have a nice seal. My borrow area material looked to be a dry clay/sand mix and I hope it will work as no other material is close enough to make the project feasible. I will post results of soil analysis when I receive them.
