The sheet is Technical Note 2.11 Duraslot® Burial Depth and Backfill Conditions and provides general design information about Duraslot’s slot height, burial depth requirements and backfill conditions.

The backfill envelope is the primary structural system to resist surface loads and requirements vary depending on loads anticipated. The tech note provides basic configuration details, including burial depth limits for three typical application classes: pedestrian only, roadway and airport projects. The design engineer must specify backfill and other installation details to meet their project requirements.

Duraslot slot height is referenced two ways – from grate to outside crown of pipe and the actual slot height from top of grate to inside crown of pipe and accounts for pipe corrugation. Actual slot height should be used to calculate invert elevations. ADS recommends minimum slot height of 2.5” (64 mm) for pedestrian-only applications and 6” (153 mm) for installations subject to H-20 loads.

Duraslot grates should be recessed into the pavement 0.25” (7 mm) for pedestrian applications and 0.25”-0.5” (7-13 mm) for H-20 loading applications.

The sheet has tables for minimum invert depth below finish grade by pipe size and loading condition and another table for maximum invert depth below finish grade by pipe size.

Installation conditions of Duraslot are also in the tech note. Installation considerations drive the structure’s performance and longevity and vary based on application and project. The section provides general installation recommendations for pedestrian only, roadway and airport projects and gives information and a drawing for each application.