605 Underdrains

1. Specification:

Item 605.02, 712.10 C&MS

Item 603 C&MS

2. Sampling and/or Inspection Requirements:

Use approved granular material consisting of No. 8, 9 or 89 size air-cooled blast furnace slag, furnace slag, limestone, or gravel for underdrain backfill only but not for underdrain outlet pipes.

All underdrain installation operations should have a Project Inspector present at all times to ensure the work is in accordance with the specifications. All work is documented on a 605CA-P-2 Structure Underdrain Inspection Form. Document the following on the 605CA-P-2 Structure Underdrain Inspection Form for each structure type:

Project Number



3. Method of Tests:


ASTM D4716