This document is the TN 2.04_C Minimum Maximum Cover Heights for HP for Storm Pipe. Overview, minimum/maximum cover applications provided with figures and tables.

This document is designed to provide answers to general cover height questions; the data provided is not intended to be used for project design. The two common cover height concerns are minimum cover in areas exposed to vehicular traffic and maximum cover heights. Either may be considered “worst case” scenario from a loading perspective, depending on the project conditions.

Minimum cover in traffic application pipe diameters from 300 - 1200 mm (12” - 48”) installed in traffic areas (AASHTO H-20, H-25, HL-93 or CHBDC CL-625 loads) must have at least 0.3 m (1’) of cover over the pipe crown, while 60” (1500 mm) pipes must have at least 600 mm (24”) of cover. The backfill envelope must be constructed in accordance with the Installation section of the Drainage Handbook and the requirements of applicable standards such as ASTM D2321. Structural backfill material should extend to the crown of the pipe; the remaining cover should be appropriate for the installation and as specified by the design engineer. If settlement or rutting is a concern, it may be appropriate to extend the structural backfill to grade. Where pavement is involved, sub-base material can be considered in the minimum burial depth. While rigid pavements can be included in the minimum cover, the thickness of flexible pavements should not be included in the minimum cover. A table for minimum cover requirements for ADS HP Storm load is provided.

Wall thrust generally governs the maximum cover a pipe can withstand and conservative maximum cover heights will result when using the information presented in the Structures section of the Drainage Handbook. The table shows the material properties consistent with the expected performance characteristics for SaniTite HP materials for a 100-year design life. The maximum burial depth is highly influenced by the type of backfill and level of compaction around the pipe. General maximum cover limits for ADS SaniTite HP used in sanitary sewer applications are shown in Table 3 for a variety of backfill conditions. A table for ADS HP Storm Mechanical properties and a detail of the HP Storm Trench with uniform backfill and maximum cover provided.