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Line 26: + + + + + − ==Planning considerations== − Permeable pavements are surfaces that encourage infiltration. They can be used in place of conventional asphalt or concrete pavement. These alternatives contain pores, spaces and joints for allowing stormwater to pass through to a stone base, where it infiltrates into underlying native soils or is temporarily detained. Types of permeable pavement include: − *Pervious concrete − *Porous asphalt − *Permeable interlocking concrete pavers (PICP, or just permeable pavers)
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* monitoring wells and clean-outs
* monitoring wells and clean-outs
==Planning considerations==
===Infiltration===
Permeable pavements can be constructed over any soil type, but hydrologic soil group (HSG) A and B are best for achieving water balance objectives. Native soil infiltration rate at the proposed facility location and depth should be confirmed through in-situ measurements of hydraulic conductivity under field saturated conditions. A liner will be required if native soils are contaminated.
Systems located in low permeability soils with an infiltration rate of less than 15 mm/hr (i.e., hydraulic conductivity of less than 1x10<sup>-6</sup> cm/s), require incorporation of a perforated pipe underdrain. Pavements require an impermeable geomembrane where the underlying soils are contaminated or the pavement is within two year time-of-travel wellhead protection area (see local drinking water source protection plan)
===Geometry and Site Layout===
===Geometry and Site Layout===