I have a spring that has always run. The banks are about 35 feet deep and sandy with trees and vegetation on most of those banks. about 400 feet from the start of the spring there is an area that someone had tried to damn, but they used sand and it did not hold. Would it work to damn this up or would the banks just cave in. Some of the banks are very steep. I'm thinking of a 1 to 2 acre pond. It would put the spring under the water.