If you need a pond liner, EPDM reinforced membrane is a very good option. This part roll is 10 feet wide and about 100 feet long. Manufactured by Carlisle Syntec Systems. Using the TPO adhesive, and lengths of 10' wide membrane, it is easy to make a huge pond liner that is 20 or 30 feet wide as long as you want. I also have most of a roll of white TPO - perfect for a first class roof membrane, bonded with the TPO adhesive - which I also have. TPO with the TPO adhesive is $200. I am guessing there is about 100 feet x 10 feet wide, left on the roll, and one 5 gallon tin of adhesive. All of this is left over from a commercial roof project. The www.carlislesyntec.com gives insight into the world of TPO. It's a fantastic material, and for a pond liner, is a very low cost solution to keep the water where you want it.