Typical Filter and Drain Configurations

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Message: Modern practice and guidelines dictate the use of zoned embankments that include, at a minimum, engineered filters downstream of earth cores and around conduit penetrations and toe drains.

Properly sized filters and drains that prevent unprotected exits are crucial to successful embankment repairs and construction.

Sand Filter

Provides a barrier between the core of the dam and the downstream shell. The sand filter captures flow traveling through the embankment and prevents the movement of soil particles. ASTM C33 concrete sand is an excellent filter for most embankment dams.

Drain Rock

Accommodates any concentrated seepage that is greater than the capacity of the filter layer. ASTM coarse aggregate #8 is a common drain material.

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  Typical configuration of a single stage filter.

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  Typical configuration of a two stage filter.

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  Typical filter and drain materials.

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  Construction of an engineered filter using a sand filter and layer of drain gravel.

Note: The content on this page was originally created as part of DamOutletWorks.org (DOWL, 2018). It has subsequently been updated and reformatted as part of the Dam Safety Toolbox.
Revision ID: 4755
Revision Date: 12/02/2022