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   DIR Return to: Erie Canal & Embankment Dam Integrity
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       #Post#: 931--------------------------------------------------
       A reminder of the rules regarding embankment dams
   DIR By: Michael Caswell
       Date: January 28, 2020, 10:36 am
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       The following was extracted from a US Army Corps Of Engineers
       document date from April 2014
       ETL 1110-2-583
       c. Vegetation-Free Zones. Vegetation-free zones shall, when dry,
       be mowed to a height of 3–6 in. at any time the grass reaches a
       height of 12 in.. Mowing shall be triggered by grass heights of
       less than 12 in. if important to the health maintenance of the
       particular grass species.
       The maximum height of grasses shall be 12 in.
       The minimum vegetation-free zone requirements for specific
       structures are:
       (1) Embankment Dams.
       At a minimum, for“dry”reservoirs, the entire dam embankment
       surface, including upstream impervious blankets and the upstream
       and downstream areas within 50 ft of the embankment toe, shall
       be a vegetation-free zone (see Figure A-20).
       For “normal pool” conditions, the entire embankment surface from
       the upstream toe of the dam or from the upstream limit of the
       impervious blanket, as applicable, to a minimum distance of 50
       ft from the downstream toe shall be a vegetation-free zone (see
       Figure A-21).
       [attachimg=1]
       (2) Dam Abutments. The dam abutment is defined as the part of a
       natural valley side-wall against which a dam is constructed. At
       a minimum, the vegetation-free zone shall extend for a
       horizontal distance of 15 ft beyond the embankment/abutment
       contact line (i.e., groin).
       (3) Spillways.The safety of embankment dams requires the
       unobstructed operation of spillways. The minimum vegetation-free
       zone shall include the spillways and spillway channels,
       including spillway slopes and approaches.
       (4) Outlet-Works Discharge Channels.The minimum vegetation-free
       zone shall include the entire outlet channel, outlet structure
       headwalls and wingwalls, and surrounding areas to a distance of
       50 ft from the top of the bank of the outlet channel.
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