Lot of good advice listed above, especially Ewest and Bob, you have to look down the road with this type of project.
I do this kind of work across the River and from what you have mentioned so far there are a few red flags, most of which have been mentioned and include:
1) lack of overall design including shoreline depth and topography plus total yardage; 2) no mention of watershed size which dictates outlet requirements; 3) no specific design on water control structure or emergency spillway; 4) no specifications on interior/exterior side slope requirements; 5) no minimum levee top criteria; 6) has a test pit been dug, are you excavating to a clayey or sandy soil? The list goes on...
If YOU are going to be the "contractor" for this build, you need answers to all the above plus more. The levee design and yardage is easy, we do it every day from an RTK survey or LIDAR data.
Where the dam will sit is at 195' elevation. The top of my property is 200'. The dam will be 6' with 2' of freeboard. From grade we are going down 4' for a total of 8' deep.
Your holding water within 1 ft of your neighbor, given a 100 year rain event will the outlet capacity prevent flooding on your neighbor’s property? Do you have an engineered design stating that? Do you have a dam permit (if required)?
Your prices on moving dirt are in line with going rate, but where are your design specifications? Is this a "guesstimate" of time or yardage? If so add 25%.
Forget the corrugated pipe if you have any agricultural runoff, especially rice. Single wall corrugated is good for 10-15 years in that situation, we replace it every day. Double wall is better but a pain in the butt to fool with and not as good as steel. Used steel pipe is reasonably priced and will last MUCH longer.
After moving dirt pull soil samples for lime requirements, consider pier/dock construction and gravel structure placement. This of course is in addition to overall depth and contour...
Many factors to consider but, do it right and do it once. The second time costs a WHOLE lot more. Your contractor may be good to go, but you need:
1. Solid levee design including total yardage with defined side slopes
2. Overflow AND emergency spillway design
3. Benthic profile of the finished product.
Good luck!
