Pond Boss Forums POND CONSTRUCTION Selecting a site help with freshly built pond

hi, my dad and i are looking at a piece of land to purchase that has a freshly dug approx 4 acre pond on it. the farmer who owns the land placed a drain tile in the dam to prevent this from filling while they were digging. therefore, the pond has never been filled with water. i have a couple major issues i need to resolve, but i have no idea how to do it.
1. how can i be sure that there is a good clay base that will "hold" the water in.
2. all of the water shed for this pond comes from a field that will either have corn or beans in it. i am concerned about the chemicals that may wash into the pond, but i am not sure if this is a big deal or not.
i live in muncie indiana and there doesn't seem to be anyone around here that has enough knowledge to help me. thanks for any help in advance!
i should also ask, how do i "plug" the drain tile that he currently has in place at the lower part of the dam.
if you can think of any other concerns i should have please bring them to my attention.
this is a HUGE investment for me and i hate like heck to buy it, build my house and have no water in the pond.

Craig,
You got some homework to do, my friend. Read this site, lots of great info. And, be ready, there are several pond pros nearby who will chime in on your question.
Here's my quick two cents worth.
First, find out who built the dam. Ask them how it was engineered, and what type of soils are in the dam. Ask if the dam was cored, how deep and how wide, and backfilled with what kind of material.
If you can't get answers, hire an engineer to analyze the dam site. With a core sample or two or three, it won't take long to figure out if the dam was properly built. It is consulting money well spent.
The tile at the bottom...find out what it's made of, and how long its life should be. Then, find out if anti-seep collars were used during dam construction.
If the tile is good material, and it has anti-seep collar(s), then you can either put an ell with a standpipe, or a gate valve with long stem on the inside. Or, you can put a standpipe on the backside, in the dirt of your dam, where water can flow over the top, through riprap, and back into the creek.
If the tile is no good for an overflow pipe, concrete it, and be sure the emergency spillway will suffice.
Regarding chemicals, that certainly should be of concern, especially if there's no greenbelt between the lake and farmland.
Due diligence, my new friend, due diligence.

Thats all good advice with things that will be helpful and save $$ I live not to far from you and have been constructing ponds a long time as far as I can see you may need someway to channel your runoff water into a holding pond before you let it enter your pond with the no til farming that is the norm in our area it is best to make sure that you dont get chemicals as well as bean and corn stubble in the pond alot of the debree has leftover chemicals in and on them a sediment pond will help if the water is chaneled through it as well as growwing a green layer around your pond. Good luck and keep on reading this site Doc