North Lake Dam -- Rock Riprap QuantitiesAs another follow up to our list of action items, we have reviewed the
quantities for rock riprap – both what will be required and what is
available on the Main Dam and Saddle Dam. In the original cost estimate,
we had estimated approximately 9,600 CY of rock riprap needed for
additional protection along the face of the Main Dam and for placement
around the spillway area.
With the northern arm of the dam (extending along the lake edge below
the former power plant property) not officially on city-owned property,
this segment of the may not be as available as previously assumed as a
borrow source for riprap. We’ve analyzed the quantities of rock
available along the Main Dam and Saddle Dam and determined two
alternatives:
Alternative #1 involves removing rock along both the Main Dam and
Saddle Dam to approximately elevation 500 ft-msl, with additional borrow
from the northern arm. This would require some coordination with the
current property owners (Luminant/Energy Future Holdings, I believe).
However, this elevation is the preferred alternative from a dam safety
standpoint.
Alternative #2 involves removing rock from both the Main Dam and Saddle
Dam to approximately elevation 495 ft-msl. From our estimates, this
alternative would not require additional borrow from the northern arm.
For both alternatives, the elevations are approximate, and it is
possible that additional rock may be necessary. The additional rock
would likely come from the northern arm on Luminant property.
Please let us know how you’d like to move forward or if you have any
questions or concerns.
Thanks.
Patrick Miles, P.E.
Water Resources
Freese and Nichols, Inc.
4055 International Plaza, Suite 200
Fort Worth, Texas 76109
817-735-7236
817-735-7483 fax
www.freese.com
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