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Your Dam Your Responsibility (PDF~1.2MB)

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D<br />

Figure C-4: Design guide for a farm dam not exceeding 3 metres in height or 20 ML capacity with<br />

no potential hazard.<br />

A<br />

EMBANKMENT ELEVATION (Cross-Section of Creek)<br />

Preferable to crown the crest approximately 10%<br />

of bank height to allow for initial settlement<br />

Natural Surface<br />

Strip off top soil and organic material<br />

Freeboard<br />

1<br />

Strip off top soil and organic material<br />

1<br />

2<br />

2<br />

Core trench excavation<br />

See Figures<br />

C3, C4<br />

Core trench excavation<br />

Spillway cut into natural material.<br />

Batter slope may be steeper<br />

than shown if in sound rock<br />

Creek Bed<br />

Concrete Cut-off collar<br />

PIPE TRENCH DETAIL<br />

Compacted backfill<br />

Note:<br />

Selected earthfill (clayey material) should<br />

be placed in layers so that the compacted<br />

material is no thicker than 150-mm.<br />

200-mm outlet pipe in<br />

trench in natural material.<br />

(see detail)<br />

1<br />

A<br />

1<br />

1<br />

Concrete encasement to<br />

1<br />

top of outlet pipe to minimise<br />

seepage problems<br />

Drawing is Not to Scale<br />

3.5-m wide crest with 150-mm thick<br />

crest capping of well graded gravel<br />

Crest Slope<br />

Valve Operating Shaft<br />

Embankment freeboard<br />

(1.2-metre minimum)<br />

Topsoil to be spread 150-mm thick<br />

Top Water Level<br />

1<br />

Topsoil to be spread 150-mm thick<br />

<strong>Dam</strong> Height<br />

(3-m maximum)<br />

1<br />

Compacted Selected Earthfill<br />

3<br />

Upstream Guard Valve<br />

2.5<br />

Outlet Conduit (200-mm minimum diameter) Gradient 1 in 100<br />

Creek Bed<br />

Creek Bed<br />

1<br />

Isolating Valve located at least<br />

1-metre clear of embankment toe<br />

Core trench to be constructed under<br />

whole bank length to a minimum depth<br />

of 0.5-metres into impermeable foundation<br />

1<br />

Outlet pipe to extend 1.5-m beyond<br />

embankment and 0-6-m above<br />

ground level to prevent blocking 150-mm thick reinforced concrete anti-seepage<br />

cut-off collars to extend 1-metre into undisturbed<br />

ground around and under pipe and 1-m above<br />

pipe into embankment fill<br />

3-m<br />

minimum<br />

81

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