Answer: A company called CETCO (521 East Epsom Rd., Unit 1-B, Towson, MD 21286, ph# 410/339-7424) sells bentonite clay for this purpose, and Seepage Control, Inc. (PO Box 51177, Phoenix, AZ 85076-1177, ph# 800/214-9640) sells a polymer emulsion sealant. If you haven't already done a bit of research on pond building, let me recommend some: Earth Ponds Sourcebook, by Tom Mattson, Countryman Press, ph# 800/223-4830 (there's a companion video available, too); Building a Pond for Food & Fun, by D.J. Young, Bulletin A-19, Storey Communications, Pownal, VT ph# 800/441-5700). Enjoy!
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