Revamping 20yo Pond with Light Leakage - Opinions? - 02/18/19 04:53 AM
I've been lurking on these forums for a while, planning a big pond revamp in the shadows, but it's probably time to emerge from hiding and ask for some suggestions.
The situation:
My family's 20 year-old pond was stocked pretty willy-nilly and we only practiced catch and release, so it's badly out of balance and we'd like to start over fish-wise. Though, there are some concerns about the dam's integrity that we'd like to resolve before we start blowing stacks of Benjamins on revamping the fishery (only to have our investment wash down into the creek 0.5mi away, though I'm sure the local trout fishermen would be thrilled to accidentally catch SMB and YP). The dam has held up for 20 years and the water level has always been pretty stable at full pool (see details below about ample inflow), but upon original construction there was a large wet spot (like generalized light seepage) about half to 2/3rds of the way up the dam, for which we drained the pond and had the builder come back and redo the top half of the dam. That top portion has seemed pretty well sealed since, but in recent years we've noticed some wetness on the back of the dam down lower. I'd been away for a decade angling for a career-induced heart attack before 35 but am just recently back home, so I haven't seen this leaky spot with my own eyes, rather I'm relaying what my parents and brother have seen. We'll try to get some pictures once the snow melts and if it ever dries up enough for the leak to show.
It's hard for you guys to confirm the diagnosis without pics, so for now, I believe it could be 2 potential causes. Either:
Potential Cause A. the builders didn't put in a core trench, so if they didn't compact the lifts well enough down low, we might have light seepage through the bottom of the dam (which is 90ft thick at the bottom).
OR
Potential Cause B. there could be water sneaking in at the seam where the vertical overflow pipe or bottom drain pipe hits the dirt/face of the dam.
Other pond details:
3/4ac hill pond (about 6-8ft deep near inlet, sloping to about 17ft near the dam). It's fed by a smaller but quite steady-flowing stream, along with some underground springs. The pond was built into a ravine/hollow with some pretty good "clayish" soil, and the dam was built in lifts out of this clayish soil as far as we know/remember, without any pure clay core trench. IIRC, they did use a sheeps foot, though I don't remember how big the lifts were. They built the dam during the winter, so the freezing and thawing of lifts may have messed up compaction. Our main vertical overflow pipe is currently clogged (which is another urgent matter to resolve), but once that's fixed, we do have a horizontal drain pipe at the bottom of the pond that we could pull the plug on to drain (if it's not covered up by 20 years worth of muck).
Questions:
1. Would draining the pond compromise the integrity of the dam? Could it cause cracking or more leaks, given the mixed clay soil? (Note: I'd like to eventually drain anyway to nuke the current fish population and stock from scratch)
2. If it's Potential Cause A, a generalized seepage, what would you recommend? Soil-floc when the pond is still full, draining and putting on bentonite, or something else?
3. If it's Potential Cause B, leaking through a seam around the pipes, what would you recommend? I'm thinking we would have to drain and pack bentonite around the pipes where they meet the dam.
4. Any suggestions on how to unclog a vertical overflow pipe? What about if it's actually clogged in the horizontal piece? (IIRC, the vertical part is about 17ft tall, but the horizontal piece from pond bottom to outlet stream is probably closer to 90ft long.)
5. Any other general comments, potential causes of the leak, etc.?
Any thoughts or recommendations would be greatly appreciated. Let me know if you'd like any more info.
The situation:
My family's 20 year-old pond was stocked pretty willy-nilly and we only practiced catch and release, so it's badly out of balance and we'd like to start over fish-wise. Though, there are some concerns about the dam's integrity that we'd like to resolve before we start blowing stacks of Benjamins on revamping the fishery (only to have our investment wash down into the creek 0.5mi away, though I'm sure the local trout fishermen would be thrilled to accidentally catch SMB and YP). The dam has held up for 20 years and the water level has always been pretty stable at full pool (see details below about ample inflow), but upon original construction there was a large wet spot (like generalized light seepage) about half to 2/3rds of the way up the dam, for which we drained the pond and had the builder come back and redo the top half of the dam. That top portion has seemed pretty well sealed since, but in recent years we've noticed some wetness on the back of the dam down lower. I'd been away for a decade angling for a career-induced heart attack before 35 but am just recently back home, so I haven't seen this leaky spot with my own eyes, rather I'm relaying what my parents and brother have seen. We'll try to get some pictures once the snow melts and if it ever dries up enough for the leak to show.
It's hard for you guys to confirm the diagnosis without pics, so for now, I believe it could be 2 potential causes. Either:
Potential Cause A. the builders didn't put in a core trench, so if they didn't compact the lifts well enough down low, we might have light seepage through the bottom of the dam (which is 90ft thick at the bottom).
OR
Potential Cause B. there could be water sneaking in at the seam where the vertical overflow pipe or bottom drain pipe hits the dirt/face of the dam.
Other pond details:
3/4ac hill pond (about 6-8ft deep near inlet, sloping to about 17ft near the dam). It's fed by a smaller but quite steady-flowing stream, along with some underground springs. The pond was built into a ravine/hollow with some pretty good "clayish" soil, and the dam was built in lifts out of this clayish soil as far as we know/remember, without any pure clay core trench. IIRC, they did use a sheeps foot, though I don't remember how big the lifts were. They built the dam during the winter, so the freezing and thawing of lifts may have messed up compaction. Our main vertical overflow pipe is currently clogged (which is another urgent matter to resolve), but once that's fixed, we do have a horizontal drain pipe at the bottom of the pond that we could pull the plug on to drain (if it's not covered up by 20 years worth of muck).
Questions:
1. Would draining the pond compromise the integrity of the dam? Could it cause cracking or more leaks, given the mixed clay soil? (Note: I'd like to eventually drain anyway to nuke the current fish population and stock from scratch)
2. If it's Potential Cause A, a generalized seepage, what would you recommend? Soil-floc when the pond is still full, draining and putting on bentonite, or something else?
3. If it's Potential Cause B, leaking through a seam around the pipes, what would you recommend? I'm thinking we would have to drain and pack bentonite around the pipes where they meet the dam.
4. Any suggestions on how to unclog a vertical overflow pipe? What about if it's actually clogged in the horizontal piece? (IIRC, the vertical part is about 17ft tall, but the horizontal piece from pond bottom to outlet stream is probably closer to 90ft long.)
5. Any other general comments, potential causes of the leak, etc.?
Any thoughts or recommendations would be greatly appreciated. Let me know if you'd like any more info.