20111013 Ver 1_Public Comments_20120106

11 /013
Mcmillan, Ian
From Heather [nverkeeper @ptrf org]
Sent Friday January 06 2012 1 09 PM
To Mcmdlan Ian
Subject martin manetta
Ian
Looking at the Corps website they ve actually officially extended the comment period to January 18th
Link
http //www saw usace army mil /Wetlands /Notices/ 2012 /201102235 %20SUPPLEMENTAL%20PN Pdf
I don t have much compiled yet taking lots of calls that is eating away at my time But I wanted to share some
information from 2 ECU professors on concerns of downstream impact to the stream channel for your consideration 111
be including these in my comments
111 forward you Mike 0 Driscoll s email b/c it contains relevant attachments
From Scott Lecce
Essentially what they did was to estimate the bankfull discharge and compare it with the flow resulting from the
addition of 12 M gal /day (18 6 cfs) from the mining operation (plus baseflow) What they found was that in three of the
four channels the addition of the 18 6 cfs would produce flows that equal or exceed the bankfull discharge which could
lead to channel instability in the form of widening or incision I agree with Mike that this could produce knickpoints that
migrate upstream Although the stream power and shear stress values estimated in their scenarios appear to be fairly
low I would also be concerned that substantially increasing the discharges experienced by these streams even to flows
less than bankfull have the potential to produce channel adjustments I assume these elevated discharges would be
experienced continuously and this could impact vegetation and the stability of channel banks Bankfull flows normally
experienced by these streams may occur several times each year but only for a few days in duration not continuously
throughout the year The report also does not comment on what happens during storm events when stormflow is also
conveyed by the channel in addition to baseflow and the 18 6 cfs? I assume there would be some restriction on
discharging the 18 6 cfs during such periods
One more thing if this project is approved there should definitely be some monitoring of potential instability in these
streams by establishing baseline channel cross section data and resurveying them periodically
And of course from my layman terms I add this
For their discharges they say that because their daily discharge will be within the bankfull limits and will slowly increase
there shouldn t be any harm And for UT2 where the discharge will be right at bankfull they say the stream channel will
migrate and settle out in a well protected riparian zone so there will be no problem I don t see any support for those
conclusions or any consideration of what happens when the discharge is added to normal storm flows
Thanks and look for more next week'
Heather Jacobs Deck
Pamlico Tar RIVERKEEPER
Pamlico Tar River Foundation
P 0 Box 1854
Washington NC 27889

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