How to get rid of water with high water table?

[jim_wilson]

Last year I dug down the foundation on my house and waterproofed the entire rear foundation wall and added a footer drain that currently goes about 20ft into the rear yard where it just ends ( I need a drain field but havent had time to put it in). I also had a problem last year after digging the excavation to install a garage foundation where it filled in with water to the point where I had about 2feet or so of water in the excavation and the water line was about 2 feet or so below grade (in a 4 ft deep hole) . Well we are getting a ton of rain again over the last week or so and while my waterproofing / drain pipe work seems to be doing it's job of keeping the basement dry my forms guy isn't going to be happy next week when he comes back to pour concrete because the excavation has about 2ft of water in it again.

I am not 100% sure this water in the excavation is where the water table is - but a few weeks back when I was cleaning out the excavation to get it ready for the formwork I came back a day later and I had about 4 inches of water in the hole - this was after we had not had rain in at least 2 weeks - so I know I have somewhat of a groudwater problem.

So here is the thing - in order for my drain system around the house to work properly I need to drain the water off somewhere - but I do not have enough grade to get the water below the level where I think the groundwater rises to when we get a lot of rain. In other words when the groundwater level rises significantly (based on what I see in the foundation excavation) that groundwater level is just slightly below where the bottom of my house foundation is -giving me nowhere to drain to. I am going to confirm this theory by digging a test pit once it stops raining and see if that fills up with groundwater.

Is there a way I can dig deeper and get below the groundwater - so I have somewhere to drain - for instance could I dig a deep drywell and maybe get to some better draining soil that would give my drainwater somewhere to go? Not being a hydrologist I have no idea what the characteristics of ground water are. I do not have a lot of land to work with - this is on a 1/2 acre suburban houselot so I cant just create a huge leech field to get rid of the water either.

Thanks

 

[beenthere]

From what I envision from your explanation, is you have water and no where to drain it, and you plan to pour concrete below the water level (table). Not good idea.
Only solution I see is to drain it to a sump pump, and pump the water table down below your concrete 'floor'. Water won't run uphill, so you will have to pump it up hill.
OR, build above the water table. /forums/images/graemlins/tongue.gif

 

[jim_wilson]

The pouring of the concrete for the garage foundation is a temporary issue - as soon as the rain tapers off I plan on getting out with a pump and draining out the hole. I have also been told by the building inspector that having the foundation actually surrounded by water is not a big deal as long as it is resting on stable ground - which it is.

My real concern is that the waterproofing and drain pipe job on the main house will ineffective if the drain pipe is essentially sitting in groundwater - for it to work it needs to be able to drain the water off somewhere - which if what I am seeing in the garage foundation excavation is true is something I dont have - the leech field for my house foundation drain pipe will be filled with groundwater - giving nowhere for the drainpipe water to go. Which is why I was wondering if I could going down below a few soil layers might get me to something that drains better.

 

[JimMorrissey]

Jim,

The water table is high water mark. I suppose it's possible that there is a layer of drainable soil down below somewhere, but that's not realistic. The water table is the level where the soils are saturated below. You'd have to pump the water under pressure to this layer if it exists.

I've got two sump pumps in my basement. One on one side and one on the other. They work pretty well and are good option for your situation. You cut a hole in the concrete and excavate by hand and/or small shovel....then drop a tub in there and lower the pump in. Obviously you'll need to pipe the pump to the outside. They work well and aren't too hard to install (weekend project). Two are better than one, so if one fails the other can make up for it somewhat before you get a chance to replace it.

Regarding you drains: I think you are saying you installed perimeter drains, but did not pipe them to daylight? You don't need a negative pitch for them to be effective. The hydraulic pressure at that level will fill them up and move the water out. You need to get the pipes to daylight somehow. Is this possible for you without going uphill? I'm having a hard time visualizing what you are saying......Forget about going below to avoid the watertable and finding more drainable soils.

 

[jim_wilson]

I already have a sump pump and a french drain inside the basement. I added a foundation footer drain and waterproofed the foundation wall along the back of the house last fall and so far it appears to be doing it's job reasonably well - we have just gotten a ton of water - I have standing puddles everywhere on the property and am seeing water in places I have never seen it before. The footer drains essentially cannot be pumped to daylight - there is not enough grade on the lot to do it. If I get a chance tomorrow I may take the backhoe out and dig a test hole - to see if I hit water at the same level that the foundation excavation is at - that should tell me whether I have I high water table problem or if there is just water accumulating in the hole. If I cant get rid of the water by going down further - like by drilling a well hole or something similar, the only other option I can think of is a decent size drywell that is then backed up by a pump that will pump out to the storm drain on the street at the corner of my property - not sure how well the DPW would take to that though.

 

[beenthere]

Around here, punching through the ground to drain surface water into the sub-layers of underground water would be a definite "NO". Our wells have to have at least 50' of casing or casing that goes through bedrock to seal off any surface water from getting into the 'well' water so it isn't contaminated.
Your drilling into this sublayer would be bypassing the natural filtration of surface water. Hopefully you don't have neighbors with wells. Around here a well driller wouldn't do it for you.
Building above water level is what I'd suggest, as anything else will be a headache sooner or later, sorry to say. Constant water pressure on the outside of basement walls is a disaster waiting to happen.
I sure hope you can find a solution.

 

[Egon]

You may have to resort to a soils type Engineer to evaluate the drainage pattern/soil in your area and then design a system to keep your basement and garage dry.

Egon /forums/images/graemlins/grin.gif

 

[JimMorrissey]

If you dig down to create a "dry well" you'll likely just find the water table again and nowhere to get rid of the water. You could dig a large hole above the water table and like you said, pump it out. I've seen people in similar situations drain to large plastic tank then pump from the the tank. You place the tank just below the bottom of the footer drain for slight negative slope. This allows you to have a place to drain to. I'd pump it somewhere in the vacinity of the town system and let it find its own way....maybe some kind of french type drain that's covered with topsoil and grass /forums/images/graemlins/smile.gif I guess it all depends on how important it is to you....seems like it should be pretty important.

I'm sure you've detailed you gutter system and have that properly draining a good distance from the foundation /forums/images/graemlins/smile.gif

You have options. I'd definitely dig the test pit and cover it with a tarp to keep the direct rain water out. That should give you a pretty good idea.

 

[jim_wilson]

It is raining like crazy out again today - so I don't think I will a chance to dig a test pit. Maybe tomorrow if the rain slows down I might get the chance to do it. I was thinking a little bit about it last night and I think that I could design a drainage system similar to what you are describing - where the water drains to a tank of some form - and from there I could go to a leech field and have the tank setup in such a way that if the water table rises and the leech field is ineffective I could pump the water out to the street and dump it in the gutter to be taken away from by the storm drains. At this point something like that seems like my only option. Until we got all this recent rain the system was working good and the water was leeching into the ground - I not 100% sure on this but I believe we have gotten around 6 inches of rain over the course of the last week or so - and it's not going to stop for another week at least according to the weather reports. This is an experiment - apparently my design needs some modifications to stand up to the amounts of water we have been getting.

 

[LarryD]

Since you're in a surburban area and you can't daylight a drain to any neighbors property, I think you're only option is to send it down the city storm drain. That's where I would start looking. I don't believe that's an unusual situation.

What about adding a water feature to the property. Ground water could be collected in a pond and any excess could be pumped to the storm drain.