Just started construction on my new home and have encountered water while digging. I am at the bottom of a hill so Im not sure whether this is storm water rolling off the hill or if its a high water table. Currently I have around 4-5 inches of water at the excavation site. Is it possible to pump the water out and pour the foundations? Anyone have any suggestions?

Yes to pumping the water out, yes to pour the foundation, no to any other suggestions.

Just remember that this water will probably still come back once the house is there so I would take good care to waterproof and a good solid draintile, gravity draining if you could.

Personally I get a little nervous building a foundation directly on top of the water table. Call me paranoid but sometimes we run into this we call for a soil boring to confirm the soil bearing capacity. This is usually only a problem if there is a swamp next to or on the property though. Costs about $2000 but has saved my butt at least twice in the last 6 years.

Thanks for the feedback guys. I have already done boring tests as this is a requirement to build a house where I live. The whole neighborhood is known to have crappy soil and a high water table but I think Im also getting a double wammy with storm water rolling down the hill. One last question... who does the draintile? Is it a plumber?

Definitely get some soil borings to tell you what kind of soil you are on and where the water level is. Water tables are not always level, but do follow the terrain to a bit.

What is terrain and surface moisture like downhill from your lot.

You may just be draining soil out of the hill, but you could also be at or near the water table. Definitely do the best you can to waterproof your walls.

Also since you know there is water present, it could return, so install drain tile and drain to "daylight" (down the hill further. At the stage you are at, the cost of a drain tile system is very cheap insurance.

If you are at the bottom of the hill and cannot drain to daylight, you have a more critical situation requiring a good water removal system. since that water can also come up (daily or seasonally) and no one has ever invented a "waterproof" floor that handles rising water.

Find out what you are really facing and plan well. - Good luck!!!

Plumbers are not needed, except for a pumping system. A good foundation contractor should be ables to do that after the footing are in. Some prefer to do it and the backfill after the walls are up. Others like to do the draintile just after the footings, but before the walls are built. This just requires some care to keep from plugging the granular fill during wall construction.

Make sure you have well draing bacfill around the basement walls.

I'm at the bottom of the hill so I'm guessing I would have to pump the water out somehow. My confusion is whether the water I'm seeing is the water table or if it's water coming down the hill. Is there any guaranteed way to tell?

There is no guarantee when it comes to weather, rain, natrual soil or Mother Nature.

Either way, you know you have water now (not just moisture, but standing water) that can come again.

You now have an oppurtunity to get the water away from the foundation and not rely on a thin barrier wall barrier (no floor waterproofing)that can be a never ending chase. Just take a look at Jay's previous post and advice.

Since you are in a wet area at the bottom of a hill, check with others and determine if you have a way to dispose of/get rid of the water or you will be at the mercy of the "waterpfoofers" that feast on poor planning and construction.

If you have a street or a ditch you can pump to plan on being able to do it even if you are lucky enough to never have to resort to it. If you do not, make sure your foundation walls are designed to withstand the pressure of saturated soils and whatever backfill is used.

Your soil boring report will tell you if it is the water table or not.

Hopefully there is a place where your footing drains can discharge to daylight without pumping. "Waterproofing" foundation walls means applying a membrane, whether it's sheet material, or liquid-applied. Dampproofing is not waterproofing. Make sure you have at least 4 inches, and preferably six inches, of gravel under your basement floor, and make sure that the vapor retarder sheet has all joints lapped at least 6 inches and taped, and that it is turned up on all walls and other penetrations like posts and pipes, and taped in those locations also. And don't forget to have them backfill your foundation with pea gravel or the equivalent, to within maybe 8 inches of finished grade. A little glob of gravel just at the footing drain won't do the job.

Old school - Keep in mind the boring only give the water table information at the time the boring were made. They can go up or down, depending on the season, recent weather conditions or changes in grading. A drain tile systen can lower the long term water level, but it is not a magic cure-all, but it is much cheaper to do it early when you anticipate a problem.

Richard -
Well said about he importance of a well-drained material as a backfill to make the water collection system take the load off the wall coatings/surfaces and minimizing water pressure under the slab.

You only can tell if the water is ground water or run off once its pumped out and sits for a while and its not raining out

You must have dry footings to pour. The township inspector will require this. It may be necessary to install a drainage system that will keep the underlying soil dry.

One of the reasons for this is ground swell due to water in the soil. And there are many others as well. But once the soil gets wet it expands some soils more then others. If you were to place a footing down for the foundation it would be in effect floating on soft soil. Once the soil drys out it shrinks thus allowing the foundation to settle. Now you know one of the many reasons walls in basements crack.

Pump it out and see if it dries. If it does wait a few days to allow it to dry out as much as possible. Then place the gravel and cement footing

what if I pump it out and still have a muddy condition? From what I'm understanding it's looking more and more like I'm going to need an engineer come and design some type of drainage system.

It might be a good idea to find out where the actual water table is. Even if you de-water and pour the footings, the water will come back in service and lower the bearing capacity of the soil as well as cause increased lateral pressures on your basement walls. Depending on the height of the water table, it could even cause some uplift on your basement slab that could cause cracking.

If you pump it out and its still muddy and it does not dry out your at the water table. At that point you need to dig some more and place gravel/drainage to keep this area dry. You simply cannot pour on an area that holds water in any fashion.

My suggestion is that you get a soils engineer that understands the soils within your area and have them take a look see. With their knowledge they should be able to assist you on what you need to be done so you can pour this properly without future issues down the road.

What ever you do now will affect the future dryness and stability of the foundation This is in my opinion the most critical part of building a structure. As it usually costs the most to fix when something goes wrong if its not done right.

Any soils report that I have had done have told me any answer to questions you have here. It should give include recommendations on the type of foundation required and it will tell you if you can pour a footing on water or not. I've poured a couple spread footings directly on the top of the water table, but only because my soils report said the bearing capacity of wet soil was adequate. Of course these were all sandy conditions, I wouldn't do do it in clay.

Thanks guys... I do think Im right by the water table so Im going to have to consult with my architect and a soils engineer. If I am at the water table and the soil is good enough to hold the weight of the building how do I waterproof the bottom of the slab in order for it not to take in water from the bottom? Is that possible?

The slab itself will stop water if it's thick enough and made of strong enough concrete. the vapor retarder will help, too, but the best defense is the gravel which should be installed beneath the slab, 4 inches minimum and preferably 6 inches deep. Then, have a sump pit installed when you pour the slab. The ground water will flow through the gravel and find its way to the sump, where a sump pump will get rid of it.

If you wanted to be extra safe, since it costs very little to do when starting from scratch, you could install an interior drain system of perforated pipes, leading to the sump pit also.

Do not connect the sump discharge to the exterior french drain piping!! Pipe the sump discharge separately to wherever the exterior drain discharges.

One more question... I am going to have floor drains in my basement and pipes below my slab and footings since my sewer elevation is higher than my basement slab. Can the ground water freeze below my foundation in the winter months and can that affect those pipes? Im around 6 and a half feet below grade.

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Richard,

My slab will be 4 inches thick with a minimum of 4 inches of gravel beneath it. Im sure its going to take a lot of gravel to compact it into a nice and tight floor. Do you think its a wise idea to do a sump pump and a french drain? I will also have a drywell installed on my property, dont know if that makes a difference in my situation.

This message has been edited. Last edited by: OldSchool,