Roadway higher than driveways?

[gjeppesen]

I have a small commercial site (1.5 acres) I'm designing in an older neighborhood. The zoning requires that I improve the private roadway that fronts my project from the arterial road it connects to to our driveway (only like 180').

The arterial roadway is relatively new and higher than the private roadway. I can design the commercial site to today's water management design standards and dump the runoff to the arterial roads drainage system. However, I can't raise the private roadway when I improve it because of a hotel parking lot that drains to it (I'll flood them out). If I keep the grade the way it is and send the runoff to the arterial drainage system, it'll back up in a larger storm and flood the area. Right now this private road is no more than a 14' asphalt path. I'm widening it to 24' wide with curb and gutter.

I guess this is the same as newer arterial roads being constructed in older commercial neighborhoods. But if the driveways can no longer sheet flow to the road that front it because it's raised, what keeps things from flooding?

 

[BigH]

This is a problem of providing "equilibrium" passages.
We had a similar problem (different circumstances) in a mountainous area of Laos. In this case, I suggested (but when you aee in construction, nobody wants to make improvements) the use of a gabion matress (300mm thick) for some 20 to 30m in roadway length that would permit the water to flow under the road surface but yet still provide a good base onto which I could place my road. You might try this - of course, you have to ensure that the matress has sufficient volume handling capabilities.
On my current project we use pipe culverts as "equilibrium" passages so that one side of the embankment dosen't allow flood water to be "higher" than the other.
I hope that the above ideas meet or can be modified to, perhaps, help on your project.

 

[dicksewerrat]

Does the hotel have a "right' to this drainage channel? I would suggest that they take care of their drainage problem. It is ussually not good and insome places illegal to let your water drain onto another owner's land. Investigate how the hotel came to drain this way.That may make your job a little easier.

 

[gjeppesen]

They have the right. It's considered "historically" draining to it so I'm out of luck there.

Thanks though.

 

[TVE]

You say "If I keep the grade the way it is and send the runoff to the arterial drainage system, it'll back up in a larger storm and flood the area." Does that happen now?

If it does, then you aren't worsening the situation and the municipality can't really make you pay to clean up a problem on their land.

If it doesn't, then the problem doesn't seem to be one of the road being lower or higher but providing sufficient stormwater storage so that you don't cause flooding during the larger storm events.

Dave

 

[nimrod2]

have you thought of using french drains to supplement your drainage system

 

[gibfrog]

This sound like you need to:

1) Raise/widen the private roadway and use curb & gutter.

2) Place a few yard drains, back of sidewalk inlets, trench drains or ditch bottom inlets outside the roadway, but within the easement, to accomidate the hotel parking lot runoff. Coordinate it with the hotel if possible. - They may be real nice if you redo their driveway connection or they may not. (You may need to widen the easement, and the hotel may not grant you any new land, then widen it on your side.)

3) Investigate whether this will increase existing flooding of the hotel parking lot and consider the use of flap valves if necessary. Although I sort of doubt any increased flooding due to your project, especially if you are connecting to an arterial roadway system.



Clifford H Laubstein
FL PE 58662

 

[gjeppesen]

If I raise the private roadway, you are right, I could put in drains for the hotel. However, those drains would have to drain to the arterial road drainage system. The design flood elevation of the arterial road system is about a foot higher than the motel parking lot and I think about the same elevation as the motel finished floor.

I thought about flap gates, and that would work beautifully...until they fail.

I'm better off keeping the two systems separate, and just not making the situation any worse than it is.

Thanks for the input.

 

[kirkussent]

What I have seen in Arizona residential subdivisions has been the use of detention basins. These detention basins catch the water during the monsoon season and also serve as parks for the residents.

 

[cvg]

rather than detention, most of them are retention basins. drainage policy in arizona generally requires onsite storage for the 100-year, 2-hour storm. the retention basins are usually drained with dry wells, although bleed off lines connected to a nearby storm drain or wash outfall are often permitted. sometimes, pumps must be used to dispose of the water in the retention basin