Drainage across driveway

[LittleBittyBigJohn]

Morning all. I have a question for the brain trust here. I got my driveway formed up this week. There is a decent fall from the house side to the shop side of the yard between the house and shop. When I did my dirt work I had envisioned the rainwater just running over the top of the driveway. Now that the forms are in place, I feel like it may be too much to get the grade back up to where it would need to be to make that happen. The transformer pad is almost the same elevation as the top of the forms.

I think it may be easier to add a drain on the high side and run a pipe under the driveway. Do any of you have pointers or advice?

 

[RustyA]

Change the grade to divert the water behind the shed? That shed roof is going to move a lot of water. Make a swale and pull that material up by driveway to create your drainage? How far is it to your property line?

 

[ruffdog]

It doesn't look bad to me but I don't know your soil/rain conditions. Very seldom I will get runoff from rain or snow melt that goes through the back yard. But that is coming from about 150 acres of sloped land.

 

[LittleBittyBigJohn]

Change the grade to divert the water behind the shed? That shed roof is going to move a lot of water. Make a swale and pull that material up by driveway to create your drainage? How far is it to your property line?

I would love to do that but it's not an option. There is more fall than it looks like and I'm handcuffed by the pad mount transformer.

 

[ponytug]

That shop roof is going to dump more than a little water. A square foot of roof with an inch of rain is 0.6 gallons. I would think that you would want to get the water away from the shop perimeter ASAP. I think a sloped sidewalk, gutters into drains, rock lined swales are all possibilities. Depending on your rainfall patterns and soil(s), drains into dry wells may be an option.

I can't tell from the photos how the slope is, so I think that it is hard to advise. Is downhill behind you from the view of the photographs? What is the slope? (House to transformer, house to shop, shop back to front, shop to beyond the driveway 50'?) Good drainage needs 1-2%, you can get away with a little less in a pipe, but less is a risk.

All the best,

Peter

 

[paulsharvey]

I would form a mild swale crossing in the drive, maybe a 5 ft long area, about 1-1.5" lower then the adjacent parts of the drive, and tilt it towards the way you want the water to go. Maybe 2% cross flow,

The grades don't look nearly different enough to really use a pipe, unless your talking something like 4" flex pipe, and that stuff is going to clog.

Also, do your self a favor, run 2-2" conduits under the drive, stubbed about 2 ft beyond the edge of the forms, for future use, and maybe a 3-4" pipe, that you can run water/irrigation, or whatever though in the future.

 

[paulsharvey]

Looking at a picture, it's very hard to see grades/slopes, But, looking at it, I would place the swale in the concrete diagnoly from the inside corner to the outside corner, allowing water from both the house area, and garage area, as well as the new concrete to be channeled away.

It 'looks' like you have a water holding area, above the drive, between the shop and house, and by placing the swale diagnoly, at that corner, it seems like it gets the water to where it wants to go naturally, and away from your important areas.

 

[CliffordK]

Does the shop have gutters to direct the water away from the shop walls and away from where you don't want it? That will help a lot from the concerns above.

It is hard to judge elevation from your photo But, you could put in a very subtle V in the driveway near where the corner is.

Actually what I'd probably do is that while the garage and shop floors are undoubtedly flat, I'd add a subtle twist in the outside pad, say drop the forms on the left side of your shop down 1" or 2" off of level. That will force any water to run off of the drive. Same thing at the house, force your water to quickly run off of the driveway.

 

[CliffordK]

You could add a river rock border along the side of the driveway. The add a french drain and pipe the water to wherever you wish. Although, I have no idea how people keep river rock clean.

 

[paulsharvey]

A minor swale in the concrete is free, effective, and zero maintenance.

 

[paulsharvey]

So when I suggest a swale or someone said, a V in the concrete, you want it spread over a pretty decent area, maybe 5 ft transition down, 5 ft back up; maybe 3ft and 3 ft; but you don't want a true valley gutter. A true valley will create an annoying bump, and also really focus water, volume and velocity, into a since area; causing future erosion issues at the outside corner area. It doesn't take much at all; I don't mean a 3" deep swale, literally just a minor low point, with a mild cross slope.

 

[LittleBittyBigJohn]

I did actually have them slope the whole driveway downhill on the cross slope section. I'll throw the laser on it to see how much fall it's got. I'm thinking an inch or so over 20'.

 

[bigtiller]

As others said, a swale in the concrete is best. I have one in my approach to the tin shed that drains half the house and a parking area. During dry times it is hard to see so I sprayed a paint spot on both ends so I can find it....I sometimes shovel snow by hand just for exorcise.

 

[CliffordK]

So when I suggest a swale or someone said, a V in the concrete, you want it spread over a pretty decent area, maybe 5 ft transition down, 5 ft back up; maybe 3ft and 3 ft; but you don't want a true valley gutter. A true valley will create an annoying bump, and also really focus water, volume and velocity, into a since area; causing future erosion issues at the outside corner area. It doesn't take much at all; I don't mean a 3" deep swale, literally just a minor low point, with a mild cross slope.

Thinking of the design of my parent's house, there was a moderate slope down towards the house entry. I'm not quite sure why we didn't raise the house more, although that would have thrown the back entry and porches out of whack.

We had drainage along the driveway which then went through a culvert and was directed down a ditch about 50 feet in front of the house. That would take the bulk of the water away from the house.

Then the driveway moderately sloped towards the house. So about a foot in front of the garage, a V depression was put into the driveway that directed water to the side of the house. I'm not sure if there is a drain picking up that water beyond the driveway. The depression is visibly noticeable, but really isn't any kind of inconvenience. It doesn't take much to keep the garage dry.

In our case, the "V" was fairly sharp because we were forming with 2x4s. However, if one had planned better, one might have formed with 2x6 or 2x8 boards and put in an "S" curve into the forms with a jig saw or band saw.

For the OP, it appears as if there is a significant slope down from the shop. So runoff on the concrete won't be a huge problem if tilted off from level.

I would probably put in a small French Drain in the curved area and direct the water under the driveway.

Then, landscape so that the ground level is even with the edge of the concrete, and thus no place for the water to pool.

 

[Streetcar]

I would put a pipe under driveway if you can get grades to work. Arkansas can get heavy rain or freezing weather. Both can cause issues with overland drainage

 

[LittleBittyBigJohn]

I'm leaning towards getting a roll of 3 or 4" corrugated pipe and putting it under the driveway so it's there. Then if i can't get the grade to take the water over the driveway at least i have a backup.

 

[2manyrocks]

I'd recommend 4" solid pipe instead of corrugated because it's harder to pitch corrogated without bends/dips and water/debris flows better through solid pipe. Solid pipe is also more resistant to collapsing.

 

[ruffdog]

The 4" probably would flow twice what the 3" would....go bigger.

 

[ponytug]

I'm leaning towards getting a roll of 3 or 4" corrugated pipe and putting it under the driveway so it's there. Then if i can't get the grade to take the water over the driveway at least i have a backup.

Don't use corrugated pipe; it is prone to clogging, the walls are thin, and it just does not have any sort of longevity. Use a 4" or better yet a 6 or 8" pipe. It is hard to go too big with a pipe.

As @paulsharvey mentioned suggested above, I would however vote for a concrete swale over a pipe. They don't clog, and they can't be overloaded when that extra heavy rainstorm/ hurricane remanent that sweeps in.

All the best,

Peter

 

[2manyrocks]

A broad swale can't be crushed like a pipe, especially a pipe that isn't buried very deeply.