I was told that soda ash would work well to ensure the sealing of a new pond. .15 lbs. per sq. ft. Has anyone ever used it? Thanks

You should only use any chemical compound in your pond to address a problem. Soda ash is sodium carbonate And is used to raise the ph of swimming pools. Here is a link explaining why Pond bosses use agricultural lime instead and in what circumstances they should be used.

http://www.ext.vt.edu/pubs/fisheries/420-254/420-254.html

Soada ash is usefull only on certain types of soil, specifically those with a lot of calcium in the clay, often clays formed over limestone. Clays of this type tend to form a clump structure which doesn't seal itself very well. The soda ash helps the clumps to disperse and bond together. Works different than bentonite and only on the right type soil.

Thanks guys

Here's a site that mentions 'soda ash' as a pond sealant. Univ. Tenn. Ponds
[URL=[URL=http://www.cqconcepts.com/chem_sodiumcarbonate.php]]Sodium Carbonate
According to Univ. of Tenn., if you have a high calcium level, it's useful. Hmmm, all I can find is 1 reference that high PH soils have calcium. I have access to some marginal low clay content loam just above my future pond site. Think I'll send off a soil sample for testing this April while in Alabam.

Very good idea !! Try this link for ref. as to the question about Ca.

http://srac.tamu.edu/tmppdfs/127565-464f...8bbc0e621462a54

Carbonates and bicarbonates are the most common and most important components of alkalinity. A
total alkalinity of 20 mg/L or more is necessary for good pond productivity. Total alkalinity is expressed
as milligrams per liter or parts per million calcium carbonate (mg/L or ppm CaCO3). In water with moderate to high alkalinity
(good buffering capacity) and similar hardness levels, pH is neutral or slightly basic (7.0 to 8.3) and does not fluctuate widely.