If I were to guess at the construction of the dam, it wan't excavated down to an impervious layer to build a keyway before being built. The seepage you are seeing is water making its way through non-compacted soils under the dam.
If I were to buy a little "insurance" and wanted to assure another 20 years of decent pond, I would do as suggested:
Test the depth of the pond. If adequate:
1. Remove or make more permanent the disabling of the old drain.
2. Remove trees, stumps, roots as much as possible.
3. Create a new key-way and dam behind the current dam, re-enforce the dam and widen it, compacting properly.
4. Install a siphon system drain with a bottom draw.
If not adequate depth:
1. Remove old drain, drain pond out gap.
2. Wait a season for the muck to dry out as much as possible.
3. Excavate pond basin, shove muck out the gap on the backside of the dam.
4. Steps 2->4 above
Or
Optional elevate the new dam to gain depth instead (may cost less).
2->4 above
Cody's note: also IMO remove a majority or most of the trees and brush around the pond. Every tree there has contributed to the amount of muck and slop that is in the bottom. From the pictures it appears there are easily 3 to 4 ft of muck as mostly dead leaf matter in the pond belly. Tree leaves shorten the lifespan of the pond plus add nutrients for plant growth depending on how many leaves enter the pond. Leaves are rarely good for long tern pond ecology.
Last edited by Bill Cody; 01/06/20 06:49 PM.
