Underlayment?

[perplexed ponder]

So, I actually got the pond dug this weekend!
I have a question about what everyone uses for underlayment, if anything at all.
We have pretty much solid clay, I'm wondering if i even need one. No big trees nearby and we found only one tiny rock at about a depth of 3 feet. I was wondering if I really should put one down, what if I used Tyvek house wrap? It was difficultfor me to push my car key through. Cost about 100 bucks for  a 9 x 150 ft roll. I could  double up on the bottom if I got that. Also looked at tarps, but it was far easier to push the key through and was only about $40.

[Jerry]

They sell stuff for that, but old carpeting works too. $$$$

[tranquility]

We also have heavy clay soil here--past the first foot or so and its pure clay.....Our first pond I bought underlayment....our 2nd pond-I didn't---our 3rd pond I didn't--and so on....I just use an old tarp or plastic under the liner especially around the sides just incase there is a tree root I miss---other than that no--I only did our sides on the new pond using tarps and didn't bother with the bottom...We just made sure to pick up any large clots of dirt and rocks....so far---so good....
Lawanna

[perplexed ponder]

Jerry,
We priced out the carpet, it was going to be $300! That's what we use don this one, but the neighbor was throwing it out from his garage and it was perfect and FREE!  No such luck this time. 
Lawanna,
gee, I thought I might need it on the bottom and not the sides, I think you are right though. In case the neighbor's tree roots get over there in 10 years or something.
I am excited to put in the liner and fill it to see what it actually looks like. It make the move over there much more bearable. Having a project gives us something to do and something OTHER than cancer to talk about, which is the best kind of therapy!!
Some friends may come next weekend to help me move the retaining wall bricks from here to Mom's if we have good weather, and maybe some shrubs too. Most of the landscaping and rockwork will have to wait until spring. It's getting cold here very soon. We got a great weekend in the high 60's, I'm hoping for a few more like this before it gets cold!

[Jerry]

I did mean free only. carpet stores throw out stuff the installers bring back after removing it from a home

[tranquility]

Even something as simple as newspaper can be used as a underpad...we use it on the bottom of our above ground pool and it worked well...so if your concerned about the bottom just start savin up your news papers --ask friends and family to do the same...
Lawanna