I have sealed many ponds using sand wash that you can get from your local sand pit. It should be applied at least8-12" thick and knitted into pond bed and banks up to the top deck.
Where water flows in should be covered with filter fabric and covered with stone to prevent leakage at this point. It does work and well with pond depths up to 20 feet.


Scott Trava
Catskill Pond
http://catskillpond.com
scott@catskillpond.com
Returning Catskill Waters To A Simpler Time
EST. 1923