Pond Boss Forums POND CONSTRUCTION Building a dam A Spring Below My Dam?

I've got an interesting problem with my pond (constructed Sept. '05). I've got a supply of running water coming out the back side of my dam. A leaky dam was my first thought, but I just don't think that's the case.

Last week we had full sun and temps in the 90's with fairly high humidity. I lost about 1/4" per day on a half acre pond. From my reading here, I'm thinking that's a pretty reasonable amount to lose to evaporation. Given the rate of flowing water below the dam, I would expect a much greater loss if it was in fact a leak.

This is leading me to believe I've got a spring down there. When the pond was constructed, a good 6-8 feet of dirt was removed from this area for use in the dam. I'm thinking that a spring was uncovered. We didn't have this flow of water previously. It's running down off my land and onto my neighbors place, making a mudhole down there, so I need to fix this.

The water coming up is very rusty, if that matters. I have contacted my contractor and he's been out to look at it and is monitoring the water level. He also took a sample out of the pond and from the flowing water. He claims he can have this tested and determine if the flowing water is coming from the pond. I'm skeptical that a test could tell him this. I'm waiting to hear back from him.

Any ideas on how to proceed?

Thanks,

Shawn

Water tests can show a big difference between water from a pond and underground water. One example is iron content (rust) which is common in underground water (springs)and not so in ponds as it settles out if it is there.

I would wait on the contractor and see what he says , but keep checking both the status of the test and the spring for any changes. I assume the spring is not effecting the dam.

The dam is damp about 1/3 of the way up and the water is running below the dam. It's also on the far side of the dam. I don't THINK it's causing a problem, but there is significant erosion downhill from the running water. It's definitely sloppy down there, as my tractor will rut it up pretty good if I try to mow through there.

If it is a spring, I'm going to have to do something about it, as it is really muddying up my neighbors land.

I figured that pond water filtered through the base of a wide dam (I'd say at least 50 feet) would be very similar to spring water. If you guys know otherwise, I'll readily believe you, as this is most certainly not my area of expertise.

A correctly constructed dam of impermeable clay should not have water filtering through any of it (max 1 ft.) much less 50 ft. Iron is only one example as there can be many differences between rain water runoff and underground water. I would not expect pond water to pick up iron from a dam as the dam clay should not have much soluble iron in it.

Is the dam wet on the non-water (back side) ? If so does this appear to go through the dam to the front side? Is there a core trench in the dam ? Is there water running down the back side of the dam? I can't imagine how a dam could be built with a core directly on top of a spring.

There is a core trench. I watched the daily progress of the pond and it appeared to be constructed as I've read they should be here on Pond Boss.

Yes, the dam is damp on the non-water side. Maybe a third of the way up. The water coming out of the ground is downhill of the damp areas and not really on the dam, but on the ground downhill of the dam.

The damp side of the dam is where the 6-8 feet of earth was removed for the dam. This is maybe a 50x60 area and also where the water is coming up from the ground. It sits back perhaps 20-30 feet from the core trench and downhill from the edge of the dam, where it ties in with the bank.

That is an ugly description. I will try to get some pictures posted here in the next day or so, as I am really interested in what you guys think.

I'm thinking that when they removed the clay from this area to use in the dam, a spring was exposed. It's just unfortunate that they used the clay from this area and exposed the spring at what ended up being the edge of where the dam tapers off.

I still haven't gotten around to any pictures yet, but I did talk to my contractor today. He's been monitoring the pond level for the past couple weeks. Here in the last week we haven't had any rain, so it was a good week to look at.

He had previously brought a 5 gallon bucket out and put some water in it. He had the bucket down 1 5/8" over the week and the pond down 2 1/8" over the week. So, even if the dam is leaking, it's a half inch per week, at most. It's not hugely surprising to me that the pond would evaporate a bit more than the bucket, due to wind action.

He also heard back on the water tests he had ran. The water below the dam had 800% more iron and manganese than the water in the lake.

So, now I'm back to thinking this is a spring bubbling up right at the base of my dam.

The contractor suggested putting some perforated tile in and draining it off somewhere else. Recall that it is currently draining downhill (big suprise) onto my neighbors land and causing a bit of a mess. There is a ditch nearby I could drain it to, but I'm not sure if I can get a trench that deep to get to the ditch. There's quite a few feet of rise before you get over to the ditch.

I could possibly get permission from my neighbor to run the drain tile through his property, but that'd be at least 600 feet of drain tile to trench in.

My only other thought is to dig out where the water is bubbling up and try to pack clay on top of it. I'm just wondering if that would cause the water to bubble up elsewhere, perhaps higher up on the dam?

Or, I guess I could just haul in a bunch of dirt to put on top of the area and put it back like it was before.

I'm sure stumped on this one.

Perhaps a you could lay a pipe to the nearby ditch?
Form your description it sounds like a tractor backhoe could dig the ditch. Then lay the pipe in and cover it.
The spring could even be damed some to raise the water level if drainage to the ditch is a probem, or just to get a neat spring fed pool.

It would probably take a backhoe to get the trench deep enough to drain the water to the nearby ditch. That's a possibility.

If I owned the downhill property I would dig another pond down there to make use of the free water source, but alas, I do not. If I dammed up the flow on my property, it would start to eat into my current pond dam.

I would be concerned about any continued wet area near/under/directly adjacent to the back of my dam. I would be concerned with its possible effect on the dams integrity.

Shawn, I inspected a 25+- acre lake y'day. It was full of water. All around the back there was rusty water. I mean everywhere seeping through.

If I were you, I would have one worry, and one worry alone, and that would be the neighbor. If he's OK, you have no problem. It may be seeping through or into a spring, but you lake for all practical purposes, from your prospective is sealed. There is not real water loss. 1/4 inch a day is expected just about anywhere because of evaporation. It is nomimal.

Could make a french drain. Have a backhoe dig a large hole, fill with 2" clean gravel and let water run into. If your soils perk good it should work.

Hi Shawn,
just a couple comments, and please pardon me if i missed something in the above posts.....a couple questions first:

1) how long was it after the pond was built (and filled) did the water begin flowing below the dam? and that you noticed wetness on downstream side of dam?

2) what is the substrate of your pond? is it soil or bedrock?

your situation sounds to me like a hydraulic pressure issue, once the pond was filled, you had a new and improved hydrostatic force on the substrate on the pond side which could be affecting the flow of shallow groundwater causing it to moisten your downstream dam material and create a flow (the spring) where there is no dam material present to keep it from flowing freely....... if you follow me.

in my area, since i have no supplemental water, i would try to figure out how to re-use this water (i.e. pump it back up and let it filter overland back into pond basin). maybe even dig a hole below the "spring" to collect the water for easier pumping.

just a different aspect for you to consider from the left coast

1) I didn't notice the wetness until this spring, but, I was not down below the pond over the winter and early spring. It wasn't wet immediately after the pond was dug, as I planted grass seed a couple weeks later.

2) There is alot of rock in the area, so I'd imagine that's whats below the pond. We hit solid rock about 8.5 feet down when we dug our basement. The guy down the hill hit the same kind of rock about 4 feet down and had to jackhammer his basement in.

Your explanation sounds very reasonable.

A buddy of mine who is a Civil Engineer was in town over the weekend and I had him look at it. He said he doesn't have alot of experience with springs, and the ones he's run into have been out of the way enough that they just throw some riprap on them and leave them.

He suggested perforated tile or a 'level spreader'. As he described it, it is basically a french drain, but you make sure the downhill side is completely level. If the trench fills with water, the water will seep out, hopefully, along the entire length of the trench, and not run off in streams, as it is now.

I'm still undecided on what to do.

Shawn,

Here are some past postings that may give you additional ammo to address your situation.

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=20;t=001163#000005

See Hico's post here. Perhaps you could email him to get an update on his pond.
http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000023

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000081

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000079

Russ