Gravel Parking lot

[dakota99]

I am working on a desing for a gravel parking lot, something I have not done a lot of. I have three questions.

1. What is a good minimum grade to use? I am curently using 1.5%

2. is there anything i need to do to the catch basins to protect them from sediment runoff?

3. Should I be specifing under drains in addtion to the catch basins?

 

[jgailla]

I haven't done any gravel parking lots or roads.
1. 1% is probably OK for a minimum grade.
2. You could put a sump in the inlets. That way you could catch at least some of the sediment before it goes downstream if maintained properly.
3. Underdrains generally are used to protect the asphalt or concrete pavement from high groundwater. Underdrains would probably be overkill.

 

[cvg]

1% slope is generally not acceptable for paved lots. for unpaved lots, slope is more critical and harder to achieve or maintain. I would shoot for at least 3 or 4% slope unless you want to see lots of ponding, potholes and mud in your parking lot.

 

[Drumchaser]

What is the prop pavt structure, and is your p-lot just for auto's?

 

[TerryScan]

There are many relevant variables that affect the answere to the original questions. It is a bit like asking "how long is a string?" Everyone must guess at parameters:

1. In some locations, there may be little slope to the overall land and great infiltration. 1% may work there. In other places, cvg may be right-on with 3-4%.

2. If it was a small lot, I would avoid inlets within the lot entirely and try to drain to edges, then have grass swales collect to inlets for pre-filtering. (If this is in the desert, this would not be as practical.) or...

3. Underdrains may be a great ALTERNATIVE to inlets. You will have to do a cost comparison. You could possibly place the underdrains only along troughs (where you would have run collection pipes for inlets anyway). With underdrains, we are already filtering sediment.

 

[saruman26]

A good rule of thumb is to have the minimum grade set at 2% - the same ideal used for vegetated channels. That allows a little wiggle room if the grade only comes to 1% or so.

As for protecting the storm sewer from sedimentation, a grass swale or grass filter strip is a good way to go. A Snout BMP device, or similar oil/grit separator, even a hydrodynamic separator like a Vortechnics unit, is a good way to separate sediment from the runoff.

 

[AUSue82]

Interesting question. I'm working on a similar project here in Georgia--extending a gravel parking lot for trucks. In general the existing slope is 4-5 percent, but in one area it is 2.5 percent, and that's where they're having problems with ponding and drainage. Seems that 4-5 percent might work best in this situation.

 

[Debaser]

When you talk about a gravel surface for thiese parking facilities is that all that is used and you depend on good compaction, or is there some stabilising material, e.g cement to bind the surface?

I'm just thinking that the continual turning movements of cars, or worse, trucks wouldn't be too kind to a loose gravel surface and the owner will end up regrading the ruts and replacing lost material every year?

 

[polariman]

I go with a 2% minimum. 8 - 12" sumps in catch basins. I agree with CBs at the edge of the lot. However, these work the best if there is curbing.

Always assume gravel lots may be paved in the future. Therefore, I would plan it with all overland drainage with grass swales but plan for future curbing and catch basins to be installed later. If there is a possibility of paving within the next 5 years, investing in curbing and catch basins now.