Drainage across driveway

LittleBittyBigJohn · Dec 22, 2023

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 · Dec 22, 2023

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 · Dec 22, 2023

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 · Dec 22, 2023

RustyA said:
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 · Dec 22, 2023

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 · Dec 22, 2023

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 · Dec 22, 2023

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 · Dec 22, 2023

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 · Dec 22, 2023

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.