Gravel

From LID SWM Planning and Design Guide
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For advice on decorative surface aggregates see Stone

  • Granular material for underdrains should be clear crushed 20 or 50 mm diameter stone graded in accordance with ASTM D 2940,
  • The 20 mm clear crushed aggregate permits the use of an overlaid layer of high performance bedding (HPB) as a choker layer,
  • The void space ratio should be > 0.35 (or > 35%)

All gravel should meet the following criteria:

  • Maximum wash loss of 0.5%
  • Minimum durability index of 35
  • Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions