North Lake Dam -- Irrigation SystemHi, Keith-
Per our conversation this afternoon, I've given a brief description of our proposed options for the irrigation system at North Lake Dam.
Performance Spec -- If you want to keep the irrigation system in place, we recommend issuing it as a performance spec, providing the schematic information available from Luminant. The
contractor would be required to remove the portions of the system affected by lowering the dam crest and provide a similar and appropriate replacement to accommodate the new crest elevation.
This would also include installation of new pump(s) on city-owned property. Shop drawings would need to be submitted for approval, signed and sealed by a licensed irrigator.
Abandon System -- The purpose of the irrigation system is to control the moisture level of the downstream slope in order to maintain a more stable slope and prevent surface slides, which
have historically been an issue at North Lake Dam. Because we will be reducing the load on the embankment by removing a significant portion of the crest, it may be possible mitigate
the issues of these slides by flattening the downstream slope. We would accomplish this by using part of the downstream slope as borrow material, along with material from the crest of
the dam. If we are able to achieve a flat enough angle, the slope should stabilize without the need for irrigation. In this case, the contractor would be given more specific limitations
on how to remove the embankment material for borrow, and would also be required to remove the irritation system entirely. A brief analysis of the slopes possible with the existing geometry
is still necessary to confirm the feasibility.
Feel free to give me a call or email with any questions you might have. I'll be in the field all day tomorrow. So, if you can't reach me at my desk, you can call my cell at 817-734-9151.
Thanks.
Patrick Miles, P.E.
Water Resources
Freese and Nichols, Inc.
4055 International Plaza, Suite 200
Fort Worth, Texas 76109
817-735-7236
817-735-7491 fax
www.freese.com<http://www.freese.com>
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