Aggregate selection and cost for impervious surface reduction.

This paper investigates the possibility that some aggregate gradations could be considered functionally ‘pervious’, based on comparison of an aggregate's permeability with either natural soil permeabilities or local rainfall intensities. Permeability was estimated by calculation for 27 American standard gradations, based on their porosity, coefficient of uniformity and effective particle size. In addition aggregate's cost relative to other urban surfaces was estimated. The results show that gradations of ASTM D448 No. 9, 89 and larger have high permeabilities relative to both the most permeable soil and the most intense rainfall in the central and eastern United States and so could be considered pervious surfaces in that large region. Denser gradations have lower permeabilities and less claim to be considered pervious. Properly selected aggregate's combination of high permeability and low cost make it an attractive option for reducing impervious cover, under the detailed traffic types for which it is suited. [ABSTRACT FROM AUTHOR]