swale or french drain for wet basement 3

[jay2000]

Hi, I’m receiving water in my basement after a heavy rain. My property borders up to a
large hill. I’ve read several places that a swale or outside French drain could help my
problem. Here are my questions?

1. Which is best swale or outside French drain?

2. I’ve read that a swale should be approximately 10 inches wide and 2 inches deep
with a 1/8 to 1/4 inch drop per linear foot. The length of area I would need to
cover is approximately 70 feet which would mean the drop would be 8.75 for the
1/8 value and 17,5 for the 1/4 inch drop, which I believe would be quite
noticeable in the yard.

3. If I decide to construct a French drain I’ve read that there is a 1 inch bed of
gravel, 4 inch drain tile and another 1 inch bed of gravel followed by a 1 inch
layer of top soil. I’m not sure if I would need some type of surface drains tied
in to the drain tile, or does the water naturally soak through the ground into the
drain tile. I’m also assuming that the ditch depth should be approx. 76 inches
deep. 1 inch for gravel, 4 inches for drain tile, 1 inch for gravel and one nch for
top soil with the same pitch as above 1/8 or 1/4 per foot.

So there’s the situation. Water in basement, swale or french drain,which is best.
Thanks ahead for any advice regarding this isssue.

 

[Grouser]

Focht3

I checked with a colleague and verified the minimum 'treatment' requirement for all sites in Miami-Dade County is the first inch of rainfall. This volume cannot join any surface runoff leaving the site.

It is my understanding that project sites where less than 5 acres of soil will be disturbed are not covered by NPDES and a Storm Water Pollution Prevention Plan (SWPPP) is not required.

 

[Dogface]

Jay2000- your problem/questions interested me because l am dealing with a similar situation. Have you done any of the grading yet? I would like to hear how well it worked.

 

[jay2000]

Dagface, at this point in time I've regraded the area near the house foundation, so that the ground slopes away from the house. I still see some small spots about 5 inches in diamater on one wall, but it's no way near the way it was before I re-graded the soil. I would have an inch of water in my garage. I'm still considering the swale for the back of the house that meets a large hill, as I think water is still loading up at that location. Hopefully this advice is usefull.

 

[jay2000]

Okay everyone it seems I'll need the swale. One final question before I start. Do I need to put a bed of gravel under the swale below the top soil (no drain tile or pipeing)? I've read on several web sites that this is prefered.

 

[Focht3]

I wouldn't - that's really a french drain. Make it a plain swale to start with -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[jay2000]

OK, the only reason I asked about the gravel is I want to keep the swale at around 1%. I was thinking I could dig the trench at 2%, add a layer gravel and a layer of top soil to bring the top up to 1%. This way I would have a slight swale across the top and if the swale pitch wasn't steep enough any water would percolate down to the swale bottom (2%) and be carried away. I realize that your response on June 19, 2003 advised against a french drain. Is this the same thing you advised against?

 

[Focht3]

Yes - it simply provides a path for water to collect and percolate into the ground - and get into the basement. Not a good idea...



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[jay2000]

Thanks for the advice. So do you think the 1% will be adequate?

 

[cvg]

1% is quite a good slope for drainage channels. However, make sure your grades are precise. If you don't get provide a uniform slope on the channel, you might get standing water which will soak into the ground. Check your grading (by using water) when you are done to make sure it drains.

 

[Focht3]

[blue]cvg[/blue] is correct - and the testing afterward is also a good idea. Also test it again in the spring in case "bird baths" develop over time in the surface of the lawn.



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[jay2000]

Thanks for the advice everyone. Looks like this weekend will be the weekend for the project. I'll keep everyone posted as to the outcome. Too bad you van't post photos on this site.

 

[Focht3]

Put them on another web site, then post a link to it. That way we can see your progress -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[dnonnema]

I have a similar issue with my house--sits at the base of a large hill and my back yard is very wet. My sump pump runs frequently.

I recently installed a french drain at the base of the hill, approximately 20 feet from my foundation (3ft deep, 4" perforated pvc pipe wrapped with fabric sleeve, surrounded with 3/4" clean stone). The drain is working great--water has been flowing out of the outlet pipe constantly since i put it in.

One problem--my sump pump is still running just as much as it ever did. I'm talking about a lot of water--the pump is 3/4hp, 1.5" outlet pipe, runs for about 40-50 minutes every 3 hours.

My question--should I have dug my drain deeper? Do i need to take the base of the drain down to the basement floor foundation level to keep the sump pump from running so much? Should I build a new, deeper french drain parallel (closer to my house) to the first drain I dug?

Also, should I wait for the ground to dry up before I excavate again?

Also, apparently my footing drains are blocked. Is their any way to clean out the footing drains without draining my bank account? :-D

 

[Focht3]

[blue]dnonnema[/blue] asked:

I have a similar issue with my house--sits at the base of a large hill and my back yard is very wet. My sump pump runs frequently. ...One problem--my sump pump is still running just as much as it ever did. I'm talking about a lot of water--the pump is 3/4hp, 1.5" outlet pipe, runs for about 40-50 minutes every 3 hours.

That isn't good.

I recently installed a french drain at the base of the hill, approximately 20 feet from my foundation (3ft deep, 4" perforated pvc pipe wrapped with fabric sleeve, surrounded with 3/4" clean stone). The drain is working great--water has been flowing out of the outlet pipe constantly since i put it in. ... Also, apparently my footing drains are blocked. Is their any way to clean out the footing drains without draining my bank account?

I'm glad your new french drain is working, but you should know that the stones will clog over time as the clays work their way into the voids between the stones. That's what probably happened to your footing drains. And there's no way to clean the drains - you'll have to dig them up and replace the stone. This time you should put a filter fabric between the stone and soil, too. Or use concrete sand instead of washed stone.

My question--should I have dug my drain deeper? Do i need to take the base of the drain down to the basement floor foundation level to keep the sump pump from running so much? Should I build a new, deeper french drain parallel (closer to my house) to the first drain I dug?

Are you getting water into your basement? You should hire a local geotechnical consultant to see whether a new, deeper french drain is needed. This is a problem that really needs to be seen -

Also, should I wait for the ground to dry up before I excavate again?

I would!



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[cvg]

If your basement is not getting wet, why are you concerned with constructing another french drain? Another drain will reduce the amount of time the sump pump runs, but will not likely eliminate the water getting to the sump. Your sump is running about 5 hours per day (20% of the time). That's not bad. However, I am estimating that you pump about 9,000 gallons of water per day. That seems like a lot of water and doesn't even include the water you are collecting in the french drain. As I have mentioned before, I would investigate the source of this water. Also, a swale was recommended as a first attempt to reduce the amount of surface water which is soaking into your backyard. Have you tried that?

 

[dnonnema]

jay2000..did you line your swale with anything to promote water flow, and prevent seepage into the ground?