There are some areas of the U.S. that truly have impervious soils, but they are not common. Generally, if you commonly have septic tanks in your region, your soils have a sufficient perk rate for pervious concrete pavement.  A layer of clean washed #57 stone (35-40% voids) under the pervious concrete paving (15-25% voids) can store the design volume of water for percolation over several hours.

If you have completely impervious soils in your area, pervious concrete pavements can still offer important advantages. From a hydraulic viewpoint, pervious concrete pavement functions in a manner similar to natural ground cover. In a rainstorm, water first wets the surface of the pervious concrete pavement then percolates into the layer where it is temporarily stored or begins a slow flow downgrade through the layer. A five inch thick layer of pervious concrete can absorb and detain nearly an inch of rain, even in impervious soils. In many parts of the country most of the rainfall occurs in events of one inch or less. In rain events greater than one inch, the pervious concrete pavement "fills up" with water, and the rough texture slows the remaining surface flow in a manner similar to grass sod. Therefore, regardless of the soil type in an area, pervious concrete pavement offers the advantage of detaining the rapid runoff of water from a paved area, reducing the need for large detention ponds.

"If the subgrade soil under the pervious concrete pavement gets saturated will it become very weak and cause the pavement to fail?"

Pervious concrete pavements are recommended for auto parking only. Occasional trucks can be accommodated, but heavy semi traffic is not recommended. (Although there have been some subdivision streets in Florida with pervious pavement installed.)  Pervious concrete pavement should not be placed directly on subgrade soils, but a layer of granular base at least 2-3 inches thick should be placed under the pervious concrete layer for additional strength and separation from the fine grained subgrade soils.

Autos only place 30 - 50 psi stress on the surface of a pavement and the load "spreading" ability of pervious concrete and aggregate base material reduces the ultimate stress on the subgrade soils to a very low number.  Unless the soil is extremely poor, auto traffic loads should be readily accommodated by pervious concrete paving. 

"Is freeze-thaw a problem?" 

This should not be an issue in the Sunbelt, but freeze/thaw could be an issue, if you have winter weather that includes snow/ice that stays on the ground for an extented period of time. If the right combination of conditions occur where the entire void structure of the pervious concrete is filled and freezes, damage to the structure can occur.  Water drains through pervious concrete very rapidly so completely filling the void structure completely may be unusual, particularly in the Sunbelt Region.  Installations of pervious concrete have been in place in Raleigh N.C., Boone, N.C. and Chattanooga, TN. for as long as 12 years, without freeze-thaw problems. 

A pervious concrete pavement installation in Pennsylvania placed directly on soil subgrade has not suffered from freeze/thaw damage of the concrete.  Winter frost heave lifts the pervious concrete several inches for a few weeks and settles back in the spring without damage to the pervious concrete (so far).  Obviously, a gravel layer under the pervious concrete will serve as a reservoir as well as protection against frost heave. Weather conditions in your area should be considered.

"What about clogging?"

Clogging is mainly a matter of design. If the site plan design allows stormwater from outside of the parking lot to flow across, introducing fines into the system, some clogging can occur in the vicinity of the flow. Areas of the pavement not exposed to this flow will remain unclogged, resulting in the "average" performance of the entire parking lot to remain good. If the parking lot is designed to take care of the rain that falls directly on it’s surface, the only source of fines will be wind blown or tracked in on vehicle tires.  Coring studies in Florida indicated that, on well-designed pervious concrete parking lots, less than 10% loss of internal volume has occurred due to infiltration of fines after 12 years. 

Sweeping, blowing, vacuuming and other normal methods of maintaining parking lots are important in minimizing the materials available to clog pervious concrete pavements. Landscape maintenance personnel should be cautioned to avoid introducing fine materials onto the surface of pervious concrete pavements. Tests in Florida indicate that the pervious concrete pavements can be vacuumed or pressure washed to remove fines.

It is not unusual for the pervious concrete paving option to be less expensive than other alternatives. When the parking lot doubles as the storm water management system: the cost of the land for detention ponds, the cost of detention pond construction, and the cost of "first flush" mitigation facilities are saved. The cost of pervious concrete can be 20% higher than regular concrete due to additional material costs to the supplier.