Minimum Grades
Minimum Grades
(OP)
Designing a concrete parking lot on flat terrain. What would be the minimum slope for the pavement, both from constructability and drainage aspects?
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RE: Minimum Grades
Mike McCann
MMC Engineering
RE: Minimum Grades
RE: Minimum Grades
Minimum slope can be 0% - for certain small areas, that can stand to have a little standing water on it after a rain. 0% is "constructible", since floor slab contractors routinely construct level and smooth concrete. Aircraft aprons are required by FAA criteria to be 1% maximum. I've seen large areas paved (asphalt) to 1%, and large concrete hardstands at 1% and less, without any obvious problems. Of course more care needs to be taken to achieve that with minimal birdbaths.
If a slope which promotes rapid runoff isn't possible, other methods could be used to prevent excessive ponding during rainfall, such as trench drains.
RE: Minimum Grades
Depending on the size of the parking lot, 1% is pretty flat. Usually a parking facility of any size has peaks and valleys that drain into catch basins (inlets) that lead to an outfall, storm sewer etc.
If the pavement is flexible in material(s) it would not be wise to have standing water...that would deteriorate the pavement over time.
RE: Minimum Grades
CarlB lists some good variables that should be taken into consideration.
RE: Minimum Grades
Note that runoff will tend to pond for longer periods on concrete because it is not pervious. Asphalt is more pervious and any ponding rainwater will tend to infiltrate through the pavement and saturate the subgrade, possibly causing subgrade failure.
RE: Minimum Grades
RE: Minimum Grades