Renovating a leaky pond - 10/08/09 02:48 AM
I have been studying this site for a while and I have been impressed with the wealth of information here. What’s even better is that you sound like a good bunch of folks. So, I am going to introduce you to my pond project. My wife and I returned to Chapel Hill, NC last year and bought a house and land just south of town. The land had a ¾ acre pond on it and I recognized that it was going to be a project. My first question was “who in the world thought you could put a pond on this gritty looking soil and expect it to hold water”
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234222070969266[/img]
Other than the soil, the site is quite nice. It has a stable forested watershed about 15 times larger than the pond area. Since I am a watershed hydrologist, I had to install a stage recorder and rain gage to monitor the pond while we addressed other projects. So, here is the recorded stage in response to the rainfall for the last year.
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234212658952450[/img]
Yes, it leaks. It loses about .75 to .80 inches a day in the summer and about .4 inches a day in the winter.
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234218814896962[/img]
My neighbor said that he could have told me that before I put in the monitoring equipment. “But”, I tell him, “You could not have appreciated the classic behavior of the forested watershed. It’s so cool: hardly any response to summer rain events and greater response to winter events”. By this time his eyes have glazed over and he is thinking about the batch of beer he is making (a good hobby for a neighbor). Anyway, I would estimate the leakage rate at about .5 inches a day. Summer evaporation in the area is about .25 inches a day and during the winter and spring the inlet stream has continuous flow. The rate is pretty constant regardless of the pond level.
So what do I do about it? I believe that whole thing leaks, but it may leak more from the deeper areas near the dam. I do not see any big leaks in the dam. I have considered the options suggested by the Pond Boss group: bentonite, local clay, or a pond liner. I was sold on bentonite until I heard that another neighbor has some local clay. Then after I drained it and saw all of the muck in the bottom of it, I thought that the expense of removing the muck to make way for the clay or bentonite would make that option too pricey. Why not cover the muck and all with a liner? Ouch! That is expensive too.
I see the pros and cons of the options as:
Local clay
Pros – It is available.
Cons – It will probably take about 200 truckloads and I do not have access for a dump truck to the pond bottom, so the clay would need to be dumped in a staging area and moved to the pond.
Bentonite
Pros – It would take less volume
Cons – It is a long way to ship it from west Texas. About $1800 a load for the material and $2500 for shipping. I would likely need three loads. I will need to remove a lot of rocks before I can till it in.
Question about Clay and Bentonite – Would I need to remove the muck before I put in the material?
Liner
Pros – Seems most likely to work
Cons – Expensive material. I would need to move a lot of rocks. I do not think I would need to remove the muck (might be a good cushion)
Question about a liner – how much professional help will I need to install it?
What about having someone come in with a track hoe and remove the muck from the deepest area and sling it up on to the medium and shallow depth areas? Then fill the deepest area with the local clay and put the clay along the deeper parts of the dam face (maybe 30 loads worth of clay). Then I could try this DB-200 stuff over the slung muck on the rest of the pond. I could refill it and see if it holds. If it does not, I will drain it again and put in a liner. All of the prep work for the liner would already be done.
Do you all have any ideas?
Other info: Target stage would be just below the tree line. It would be up to 15 ft deep at this level. (The water level in the graph is not actual depth)
Other Photos:
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234224146483138[/img]
Before Draining
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234225492416754[/img]
During Draining
[img]http://picasaweb.google.com/chip.chescheir/Pond#5390040450740666514[/img]
Current state, Yuk!!
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234222070969266[/img]
Other than the soil, the site is quite nice. It has a stable forested watershed about 15 times larger than the pond area. Since I am a watershed hydrologist, I had to install a stage recorder and rain gage to monitor the pond while we addressed other projects. So, here is the recorded stage in response to the rainfall for the last year.
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234212658952450[/img]
Yes, it leaks. It loses about .75 to .80 inches a day in the summer and about .4 inches a day in the winter.
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234218814896962[/img]
My neighbor said that he could have told me that before I put in the monitoring equipment. “But”, I tell him, “You could not have appreciated the classic behavior of the forested watershed. It’s so cool: hardly any response to summer rain events and greater response to winter events”. By this time his eyes have glazed over and he is thinking about the batch of beer he is making (a good hobby for a neighbor). Anyway, I would estimate the leakage rate at about .5 inches a day. Summer evaporation in the area is about .25 inches a day and during the winter and spring the inlet stream has continuous flow. The rate is pretty constant regardless of the pond level.
So what do I do about it? I believe that whole thing leaks, but it may leak more from the deeper areas near the dam. I do not see any big leaks in the dam. I have considered the options suggested by the Pond Boss group: bentonite, local clay, or a pond liner. I was sold on bentonite until I heard that another neighbor has some local clay. Then after I drained it and saw all of the muck in the bottom of it, I thought that the expense of removing the muck to make way for the clay or bentonite would make that option too pricey. Why not cover the muck and all with a liner? Ouch! That is expensive too.
I see the pros and cons of the options as:
Local clay
Pros – It is available.
Cons – It will probably take about 200 truckloads and I do not have access for a dump truck to the pond bottom, so the clay would need to be dumped in a staging area and moved to the pond.
Bentonite
Pros – It would take less volume
Cons – It is a long way to ship it from west Texas. About $1800 a load for the material and $2500 for shipping. I would likely need three loads. I will need to remove a lot of rocks before I can till it in.
Question about Clay and Bentonite – Would I need to remove the muck before I put in the material?
Liner
Pros – Seems most likely to work
Cons – Expensive material. I would need to move a lot of rocks. I do not think I would need to remove the muck (might be a good cushion)
Question about a liner – how much professional help will I need to install it?
What about having someone come in with a track hoe and remove the muck from the deepest area and sling it up on to the medium and shallow depth areas? Then fill the deepest area with the local clay and put the clay along the deeper parts of the dam face (maybe 30 loads worth of clay). Then I could try this DB-200 stuff over the slung muck on the rest of the pond. I could refill it and see if it holds. If it does not, I will drain it again and put in a liner. All of the prep work for the liner would already be done.
Do you all have any ideas?
Other info: Target stage would be just below the tree line. It would be up to 15 ft deep at this level. (The water level in the graph is not actual depth)
Other Photos:
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234224146483138[/img]
Before Draining
[img]http://picasaweb.google.com/chip.chescheir/Pond#5389234225492416754[/img]
During Draining
[img]http://picasaweb.google.com/chip.chescheir/Pond#5390040450740666514[/img]
Current state, Yuk!!