Tuesday, April 12, 2011

Basement Groundwater Blues


Sometimes we need to be reminded that we live in the desert. It seems Mother Nature is more than happy to confuse the climatology of this region often enough to keep us on our toes. I had an RPR follower who is new to the area ask me to do a post on the subject of groundwater and basement flooding, and being somewhat knowledgeable on the subject (I'm a big nerd) I decided to oblige.

First of all, there is a huge difference between groundwater and a water table. I'll put some of your fears to rest that your collective basements are below the water table of either the Jordan River, or that salty monster west of us - most of them are not. There is a chance that if your home is West of the Jordan River and has a fairly deep subterranean basement, you could be below the water table during high run-off periods, but not during normal flow. Footings for a home could have never been successfully installed below an existing water table (total mud fest). If you look at the diagram below you'll gain a better understanding of what a "water table" is and how it would effect someone who's home is near a substantial body of water.

Now moving on to the real culprit of most of our spring flooding woes - groundwater. Groundwater is the water that is trying to make its way through the soil moisture belt, into the zone of aeration and eventually to the water table. Unfortunately, most of the "soil" in Rose Park was trucked in as top-soil and is only a few inches deep in most places. Below that are different layers of stratified clay and sediments. Clay is a notoriously difficult substance to permeate because of how dense it is, as opposed to sand which creates tiny air pockets for the water to seep through. What does this mean? It means that when a lot of rainfall comes all at one time, the water gets backed up as it waits its turn to seep below the water table. This backed up water is subject to gravity, just like you and me. It will find the path of least resistance to its final destination, even if it means going through your basement to get there.

What can I do to minimize my chances of flooding?

The good news is that all of you can do a few things to minimize your chances of flooding. I'll cover them one at a time in order of importance.

Number One, rain gutters can either be your best friend or your worst enemy. A properly installed rain gutter can flush your worries down the drain while an improperly installed or dysfunctional rain gutter can bring the problem to your doorstep, (or in this case - basement). Lets do some math. A home of 1,000 square feet with a roof pitch of 4/12 has 33% more surface area on the roof than the floor plan, making the roof 1,333 square feet of surface area. Each of those square feet has 144 square inches. Now, lets say an inch of rain falls in a day. That inch of rain is a measure of volume and therefore calculated by cubic inches. Each cubic inch occupies one square inch of your roof making your total roof rainfall (1,333 X 144) 191,952 cubic inches of rain. There are 231 cubic inches in a gallon of water making your roofs total diversion capability 830 gallons of water. That is a lot of water folks. If your rain gutters are not functioning properly, you could have just increased that little spot on your lawns annual rainfall from less than a gallon to a veritable deluge of biblical proportions and some of that water is going to make into your basement. Your rain gutter downspouts should be carried away from your house as far as they can, 4-5 feet at a minimum and preferably in excess of 10 feet during the wet season. There should also be plenty of them, for a 1,000 square foot home, 4 downspouts is the minimum. Another nifty arrangement would be to capture the rain from your downspouts in 50 gallon water barrels with only the overflow being diverted away from the home, that would prevent 200 gallons of water from saturating your soil and would go a long way toward responsibly watering your plants and garden over the next month. In fact, you can go much farther and purchase an underground cistern capable of holding thousands of gallons of water now that the state of Utah has made rain collection a legal homeowner enterprise.

Number Two, Make the grade - the grade away from your house that is. For the uninitiated, grade is another word for slope or level. In this instance, you want your soil to be sloped away from your foundation for 10 feet around the perimeter of your home. This can be as easy as adding a little top soil to your flower bed, or as complicated as changing the pitch of your driveway if it abuts your foundation. There are a lot of things one can do to help reduce water seepage between driveways and foundations. (Remember, a driveway is the same thing as a roof, if it drains all of its rainfall to one small area, you'll have a problem). The method I prefer for sealing these joints is a product called Sika Flex. You can buy it at Home Depot in various formulas but as long as it remains flexible, it will cope with the shifting driveway elevation when and if frost heave becomes an issue.

Number Three, Install a sump pump. A few things should be noted in regards to sump pumps. First, they do not make up for good drainage design and proper preparation. If they did, I would have listed them first. Second, though they can help, they are not a guaranteed fix for ground water seepage. Their location in the home will have an effect on how useful they are. If the pump is centrally located in the basement, it may not draw the water away from your footings and foundation walls the way you'd like it to. If you have a "problem area" in your basement, its due to numerous factors ranging from poor rainfall drainage to a cracked foundation wall. Once you have done all you can to fix the underlying problems, its wise advice to install a sump pump as close to that problem area as you can. By addressing both issues you stand a much better chance of not having any basement water seepage.


Number Four, Think long term and plant water needy plants in the high water drainage areas surrounding your house. Make sure you have a good idea where your water supply line comes in, but more importantly, where your waste line leaves your house. In the 1940's when our houses were constructed, the subterranean waste lines were made of clay pipe. In most cases, these pipes actually work very well but their weakness lies in their joints. The joints are large enough to allow tiny fibrous root material through the seam in search of the water you just flushed down your toilet. Plant a tree too close to this waste line and you'll be trading basement flooding for a clogged sewage main which requires professional help to maintain. However, do it right and you'll have a hand full of thirsty friends waiting for every drop that rolls off your roof. I have a Freemont Cottonwood tree in my backyard that drinks up to 300 gallons per day in the summer months! Tree Beard (as we call him) has kept our house from flooding since the day it was built. My parents have had similar results (with one or two minor exceptions) since planting a Black Walnut.

Conclusion, though the forecast keeps saying rain and many of you are dealing with flooded basements, there are things that can be done right now to improve your situation. Start with your rain gutters, they are the biggest cause of spot flooding in a home. When things ease up a bit, take a close look at how your homes water drainage system is designed and keep this in mind before you make any major changes to the landscaping or layout of your yard. When summer hits, make a few calculated changes to help protect yourself from future flooding.

If you have any further questions, post a comment and I'll do my best to answer them.

26 comments:

  1. nicely presented info and helpful too!

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  2. Awesome! We have graded the soil away from the North side of our house and installed 10 foot gutter extenders. We also sealed the spot between the driveway and foundation. In November we installed a sump pump. Even after all of this we still have water seeping in so we used hydraulic cement in the basement. Since our cracks are so minute and we can't find them to chisel out we just laid it over and after this last rain we STILL have water seeping in. It's not in a certain area....it's everywhere. Each crack in the floor and it's seeping in places where there are no cracks! Any other ideas?? Thanks again!

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  3. {B}, What you are describing sounds pretty severe. Without seeing your house and more importantly, your yard, grade, and rain gutters, I can only assume that you have taken every precaution for what I call "reactionary repairs" which is what most of us do. It sounds like you guys have been pretty vigilant in trying to snuff this out. When did the gutter extensions and crack sealing take place? And do you have seepage near the sump pump as well? The next step beyond what I have described in the article is to excavate and seal your foundation walls from the outside, which is far more effective that the inside. It's a highly invasive undertaking that will solve any water coming in through the walls but the floor is another story. If there ever was a time where a sump pump was needed it would be to take care of floor seepage which it almost always does. The other things I'd check is your water supply line, sprinkler systems if you have them, and make sure you don't have a leak somewhere that is pre-saturating your soil before spring ever gets here. Next time you go on vacation, shut off your water main from inside your house, call the water company and ask them the best way to see if your water usage continues with the water shut off. I had a friend who was losing 600 gallons a month due to a crack in his water main. Strangely, his house never flooded as a result.

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  4. Thanks for the article RPR Editor, this can be helpful for residents in normal years. However, as the previous commenter stated, most of us in Rose Park have tried all of these solutions and are still getting water this Spring. I even went so far as to have American Leak Detection come and check every pipe and water line to verify there were no leaks and sure enough, no leaks. Water is still bleeding in all over in the basement floor (even after a good vacuum with a shop vac, it returns minutes later, even just a foot from the sump pump and there has been no rain now for several days. The soil around the house is dry, no water in the gutter or on the driveway for days. Still water coming in. The water table may have been low when they built the homes, but it rises and falls. Additionally, my home is at least a full mile east of the Jordan River and neighbors both to the North and South of me have the same issue. In my opinion, the city should have never allowed basements north of North Temple. In any case, I do appreciate your interest in Rose Park and your great website. Thanks for your contributions.

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  5. RPR, I will definitely check my sprinkler supply lines. We bought the house in November and they said they shut them off but you never know! In the beginning of our water woes we put in the sump pump. That fixed the problem for about a month. Then we had water again. We used hydraulic cement to fix the pinholes in the cement between the floor and wall. That worked for another month. Now after this series of storms we are experiencing seepage not only from the floor/wall joint but from every angle. cracks in the floors that have never been wet are now seeping. Glen, is your basement finished at all or unfinished? We bought this house with the promise of "never had water" and were excited to finish the basement to expand our family. Now we're thinking that's a pipe dream.

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  6. Also, you said that some people have had success in solving these issues. I'd like to hear how they did it. Did they do it themselves or hire in? Thanks again! We live on the "flower" street. :)

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  7. B, I know it is discouraging now, but keep your chin up. It depends how long you would like to stay in your home. With the precautions you already took, floods like this will only give you a headache once every 25 to 30 years. My basement is finished but I took precautions. Metal studs, waterproof sheetrock and industrial vinyl flooring (no carpet except a throw rug here and there). Most furniture in the basement sits on metals casters (an inch or so above the actual floor). You can finish your basement with a little innovation.

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  8. {B} Don't give up just yet on the dream of refinishing your basement. I grew up in a Rose Park basement, I personally own a finished Rose Park basement and have worked on many others. Water is not inevitable though it may seem like it now. I have a sibling who lives in a subdivision just north of Foxboro, substantially closer to the lake than we are and most of that subdivision has full basements. They can do that because of preparations made during the construction process that were not as well understood in the 40's including hydro-statically treating the exterior of the foundations, providing good drainage, and better than required soil grading. Though I agree with Glen, water tables do rise and fall with every season, but a quick perusing of hydrological data for the Salt Lake valley will show that the water table is ultimately falling as the lake level falls. This year is unique in that we have had above average fall moisture, above average winter and spring moisture, and very little drying time in between. Like Glen said, these years are very rare and with planning and awareness, should not prevent you from finishing your basement. BTW, a cistern is probably the best option for eliminating roof water runoff from saturating your soil. However, it would take a 2,500 gallon cistern to handle an average spring rain which is around $2,500 plus installation but you'd be able to water your lawn and garden guilt free when its 104 outside and save money while doing it.

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  9. Glen, just curious, have you tried a cistern or water barrels? I don't get any water in my basement (My tree seems to take care of all that for me.) though I am contemplating a cistern for ethical reasons. Just wanted to know if you had any advice, you mentioned you had tried all of the solutions I mentioned so I was hoping to get a few design pointers. Thanks!

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  10. Thanks so much guys! My husband and I are trying to keep our heads above water (pun intended) but it's a daily task to keep the water at bay. I'm seriously considering the water barrel. I've always been a fan of them. Glen, have you patched with cement or the like? What are these metal studs you're talking about? We've looked into the floor tiles that prevent mold, is that what you have? Right now we're lucky because everything is either up off of the ground on casters or in plastic totes. I'm just really worried about our water heater, furnace and washer/dryer. Thanks again! This really gives me hope!

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  11. {B}One more thought, the Freemont Cottonwood is Native to Utah, grows fast (up to 18 feet in 3 years) loves water and has a life span of over 130 years. It is a big tree though, mine has an 18 foot circumference! if you have the space on your lot, I highly recommend planting one as a groundwater insurance policy. It's leaves are also frequently listed in the top 5 best mulch leaves if your a gardener. Just a thought.

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  12. We have a pretty good sized backyard but i'm not sure if we can afford the area for that big of a tree. I'm definitely looking into plants/trees that suck up water, good idea!

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  13. Just an update! We had a friend come over and help us jackhammer the wall edges in our basement and fill them in with hydraulic cement. Hopefully this holds. So far so good. Also, we had an inspector from the city come by and he told us that we could try putting in a french drain. It would entail digging out a foot down inside our basement and putting in a pipe system. Also, he informed us that we are breaking the law by running our sump pump to the sewer line. We're supposed to run it back out onto the property....which just means it would come back in!!!

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