RE water quality issues (3)No, the lake did not rise last night due the rain.
The rpms can be lowered on the pump so that the flow can be reduced.
If we were to decrease the pumping rate it will cause an increase in
cost that will have to be dealt with as well. DWU has control of the
gates that release water from Grapevine and Lewisville, they should have
the ability to increase the release from the lakes to help dilute the
water. They won’t really be wasting any water, they just won’t get any
of the “free” water from North Lake.
From: John Rutledge [mailto:JLR@freese.com]
Sent: Tuesday, May 13, 2014 2:34 PM
To: Suarez, Michael; Keith Marvin
Subject: water quality issues
I talked with Ken Delregno with DWU. I asked several questions wanting
to get an understanding so we could figure what, if any, adjustments are
needed, He expressed concerns about the hardness, chlorides and
fluorides. Says it has been going on a few weeks and took him and his a
staff a while to realize the possible linkage with North lake. He said
that the chlorides are what some clients are concerned about,
particularly hospitals. They can treat it, but they don’t like it and
have been complaining to him. He said they are doing some more tests and
will likely have some results and be in a position to talk tomorrow. He
say he would most likely ask us to cut the pumping rate in half or some
other significantly reduced rate.
I checked USGS records for the last few weeks and at the gauge at 348,
flows have generally been between 100 and 200 cfs, so our pumping has
been roughly half the flow. Right now the flow on the elm fork is up
around 600 cfs at Hiway 348 so there should be considerable dilution
going on currently. It peaked at about 850 last night. I will let you
know what he says tomorrow.
It will likely be back to 200 cfs by sometime tomorrow morning.. Its
clear North Lake’s chlorides are about double the natural in the river
and so we may need to work out releases as a percentage or something.
Michael, did you get any rise in the water level from the rain?
I know you’ve pumped about 2/3 of the water. Other than the obvious
longer time, what is the impact to you and the project of a lower
pumping rate? Is it a variable speed pump that could be reduced or is it
an on/off type pump? I would like to figure out some options to have
handy when I talk to him tomorrow.
Thanks,
John
John Rutledge
Freese and Nichols, Inc.
4055 International plaza, St 200
Fort Worth, TX 76109
(817) 735-7284
jlr@freese.com <mailto:jlr@freese.com>
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