scope:

Purpose.

The purpose of this document is to provide interim guidance for design of levees to minimize the adverse effects of levee underseepage. This ETL recommends exit gradients and associated minimum acceptable factors of safety. Use of this guidance should minimize emergence of adverse levee underseepage and initiation of sand boils along flood-control levees with a landside top stratum. EM 1110-2-1913, Design and Construction of Levees, currently contains design recommendations for levee seepage control. Except for the changes recommended in this ETL, all other definitions, design equations and procedures recommended in EM 1110-2-1913 should be followed. Where changes are recommended, the specific EM reference is noted in brackets. Currently, EM 1110-2-1913 is in the process of being updated to incorporate these recommendations and other changes. This ETL will be rescinded when the EM is revised.

Applicability.

This ETL applies to USACE commands having civil works responsibilities.