wiredit, i've used imported clay to seal my pond. granted it wasnt bentonite, and i didnt get enough so i still have some leakage, but my 2c: till it in good, and compact, compact, compact....
IIRC, in general, you strive for 30 to 50% clay in the pond bed soil and want a depth of at least 2 feet. compaction is critical....always.......and with bentonite as the clay you might get away with less thickness, but dont risk it, do it right.
its difficult to advise on the exact pound/sq ft becuase we dont know what yer original soil type is. if its already a clay type soil, you wont need as much, and if its a sandy or silty based soil yo'll obviously want to use more....check out some earlier PB issues that discuss bentonite (someone will have to help tell which ones), and getting the book is a great idea. good luck and i welcome another californian to pondboss,
