Your Dam Your Responsibility (PDF~1.2MB)
Your Dam Your Responsibility (PDF~1.2MB)
Your Dam Your Responsibility (PDF~1.2MB)
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Appendix B utlet Works and Concrete Structures<br />
Problem Possible Causes and<br />
Potential Harm<br />
Outlet Releases Eroding<br />
Toe of <strong>Dam</strong><br />
Piping Along Outlet<br />
Note: Do not allow anyone to<br />
enter the water to try and block<br />
the outlet when water is flowing.<br />
Outlet Pipe <strong>Dam</strong>age<br />
(these can be difficult to diagnose<br />
because of occurring internally<br />
within the embankment)<br />
Cause:<br />
1. Outlet pipe too short.<br />
2. Lack of energy-dissipating<br />
pool or structure at<br />
downstream end of conduit.<br />
Harm:<br />
1. Erosion of toe over-steepens<br />
downstream slope, causing<br />
progressive sloughing.<br />
2. Eroded material causes<br />
environmental damage.<br />
Cause:<br />
1. Fracture or joint failure in<br />
outlet pipe.<br />
2. Seepage along outside of pipe<br />
(poor construction).<br />
Harm:<br />
1. Will get progressively worse<br />
and cause embankment<br />
failure.<br />
2. Can be difficult to stop once it<br />
progresses beyond a seep.<br />
Cause:<br />
1. Settlement; impact.<br />
2. Rust (steel pipe) pitting.<br />
3. Settlement or poor<br />
construction practice.<br />
Harm:<br />
1. Excessive seepage, possible<br />
internal erosion.<br />
2. Provides passageway for<br />
water to exit or enter the<br />
pipe, resulting in erosion of<br />
internal materials of the dam<br />
and possibly dam failure.<br />
Action Required<br />
B<br />
Action:<br />
1. Extend pipe beyond toe<br />
(use a pipe of same size and<br />
material, and form watertight<br />
connection to existing<br />
conduit).<br />
2. Protect embankment with<br />
riprap over suitable bedding.<br />
Action:<br />
1. Investigate cause by probing<br />
and digging.<br />
2. Determine if leakage is<br />
carrying soil particles and<br />
monitor flow rate changes.<br />
3. If flow increases lower dam<br />
water level as quickly as<br />
possible.<br />
4. A suitably qualified<br />
engineer should inspect<br />
the dam and recommend<br />
further actions to be taken.<br />
Action:<br />
1. Check for evidence of water<br />
either entering or exiting pipe<br />
at crack/ hole/etc.<br />
2. Tap pipe in vicinity of<br />
damaged area, listening for<br />
hollow sound that shows a<br />
void has formed along the<br />
outside of the conduit.<br />
3. If there is any suspicion at<br />
all of a progressive failure,<br />
request urgent engineering<br />
advice from a suitably<br />
qualified engineer.<br />
4. Install upstream valve to<br />
isolate pipeline and enable<br />
inspections.<br />
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