6.0   Drainage and Detention Design
   The completion of runoff and storage computations for analyzing the water storage available in pervious [2] pavements is a "5 part process". The methodology for the selection of the site's hydrologic design criteria and storage and runoff computations shall be documented in the design calculations for the project and submitted for review with the site plan for TAC Review. The process to determine storage and runoff is as follows.
   6.1   Section of Design Storm
   The selection of the parameters for the design storm and the pre-developed runoff condition for all sites shall be determined in accordance with the City of Noblesville's Stormwater Technical Standards Manual.
   The runoff coefficient used to determine the runoff from pervious concrete pavement for the required design storm shall be 0.95.
   6.2   Determine the Water Storage Capacity of the Pavement
   The storage capacity of the pervious concrete and aggregate base courses of the pavement shall be determined using the individual void ratios for each section.
   The volume of voids in the pavement structure shall be computed as follows:
      vT=(Aa x da x va) + (Ap x dp x vp)
      Where:
      vT   =   Total Volume of Voids for Pavement Structure
      Aa   =   Total Area of Aggregate Base
      da   =   Depth of Aggregate Base
      va   =   Percent of Voids by Volume in Compacted Aggregate Base
      Ap   =   Total Area of Pervious Concrete Pavement
      dp   =   Depth/Thickness of Pervious Concrete Pavement Course
      vp   =   Percent of Voids by Volume in Pervious Concrete Pavement
   6.3   Determination of Storage Volume and Release Rate
   The analysis and design of pervious concrete pavements shall follow the methodology of the Hydraulic Design of Permeable Pavements, July 14, 2000, North Carolina State University's Department of Biological and Agricultural Engineering College of Agriculture and Life Sciences. This publication provides a logical step-by-step method for determining the storage capability for pervious concrete pavements.
   An additional acceptable method of analysis and design can be obtained from the Portland Cement Association, the National Concrete Pavement Technology Center, and the National Ready-Mixed Concrete Association. These groups have combined to create an interactive CD that contains an Excel-based design and analysis program.
   No site plan utilizing pervious pavement shall be approved through The City of Noblesville's Technical Advisory Committee Review without drainage computations in a format compatible with or similar to the two aforementioned procedures certified by a Registered Professional Engineer in the State of Indiana.