Parking Lot

[daviv]

We are constructing a pervious pavement for a parking lot which is very closed to water. Our contractor has graded and started compacting the soil to try to get 95% compaction. However, it turned out that the groundwater is very close to the grade and the contractor can only get 77% compaction 8” below. What are some solutions? Is this issue simply a matter of groundwater? We do have a soil curve for the soil. And how deep do we have to worry about the sub grade compaction? If we are getting 77% compaction at 8”, just imagine what it is at lower depth.

 

[oldestguy]

Might as well forget getting 95 percent. Just design for a weaker subgrade, probably calling for an inch or two greater base thickness. What sort of loads on the parking lot? If just cars, no big problem. For heavy trucks its the slow turning movements that call for strength in the pavement layers, not necessarily asking for high subgrade density.

 

[Mad Mike]

All depends on the scale of the project- if higher budget, subgrade improvement and drainage; if lower budget, exactly as OG says- just thicken the base layers.

Those saturated subgrades come back to bite you if not properly addressed...if it is wet now, imagine it during a 1 in 10 year flood event.

All the best,
Mike