If I have a 4" shelf at the edge of my pond (submerged), this section, and even perhaps my much wider 6" deep shelf, will freeze solid in ice this winter. If I have river pebbles (3/8"), will the expansion and force of the accumulating and descending ice during the winter months push the gravel against the sides and bottom of the liner with enough force so that punctures are formed? I use a 45mil EPDM liner.



Also, what if i made an 18" wall out of 6"x10" fieldstones submerged in the water, surrounding a trench which has no slope introducing it. If i dont touch it, will it yet damage the 45mil liner; how about with ice pressure from above, in the winter.

Lastly, I live in northern (not too north) N.J. A lot of people insist, from the area, that ice will only get about 6" in our winters here - that since its underground,etc. I know that the frost line for my area is 18" - does this mean, on the contrary, that the ground and therefore WATER will freeze down around 16"?

I have shallow areas of my pond with both fieldstone and pea gravel submerged under the water where those areas freeze solid in the winter. I have not yet experienced any problems with the rocks or gravel puncturing the liner, from the ice or all by themselves. I wouldn't worry about that.

The frost line into the ground does not match the freeze line into water. I live in Central MD, Zone 6/7 (on the line). The worst winters, I've had more than 6" of ice. In fact, I looked at my site newsletter archives and found at least one instance where I noted the ice was 8" thick (on http://www.fishpondinfo.com/news/0203.htm). I do NOT think the ice will freeze down 16" in your area (unless something extraordinary were done).

If you get about 6", how much do you think i would get? is northern nj zone 6?

You should get about what I get, maybe a few extra inches. My ice is rarely over 6" but has gone to at least 8". This is only during the hardest parts of winter and not every year. But, of course, prepare for the worst.