Category talk:605 Underdrainage
Our office has found what appears to be a conflict between the Standard Plans and the current online spec book.
The standards show that the type 1/5 base placed on top of the underdrain. The spec states that the type 1/5 is to be placed and compacted first. Since the EPG, says to review the Standard and spec prior to installation. The two of these need to agree or be clearified.
http://www.modot.mo.gov/business/standards_and_specs/documents/60510.pdf
605.10.2.2 Trenching, placement, and backfill of underdrains shall be performed only after Type 1 or Type 5 base is placed and compacted. Backfill material shall be compacted by three passes of a vibrating pad or drum-type compactor approved by the engineer.