Cost to bring in clay for pond

Where are you located

do you have at least 15-18% clay? if you don't know go get a soil test. if you have at least that much then you can hold water. i got one of my ponds to hold water and it was +/- 17% clay. you need to add NaCl (plain old table salt) to the ground before filling it with water. the Na makes the clay particles repel each other and close the micro-pores in the soil. this makes the soil more "fat". you cannot mechanical control micro-pores. by mechanically i mean: bulldozers, disks, tillers, etc. the micro-pores have to be chemically altered. liming the soil (adding CaCO3) like you see in construction projects does the opposite, it makes the clay behave in a more granular fashion. DO NOT add calcium/lime to the soil. the trick is to add the correct amount of NaCl so that it is fully adsorbed into the soil matrix without any left over causing you to have salty water. a good soil scientist will tell you how much to NaCl you will need. he will probably tell you Xlbs per sq yard of pond bottom area to treat. you may want to have an engineer or surveyor help with the area calculation (i don't know your educational background).
do the following:
- get in touch with a soil chemist or soil taxonomist at the closest A&M University
- a good soil taxonomist can tell you "by feel" how much clay you have in the soil. this will take the place of getting a soil test.
- tell them what you are trying to accomplish and how you want to go about it. they will understand VERY WELL what info you need
no kidding: a good soil taxonomist can tell you with 1-2% how much clay your soil has by rubbing it between his fingers as he/she looks at it.
good luck