20140123 Ver 1_Emails_20140319

Fox, Tim
From: andrew@confluence'engzom
Sent: Tuesday, March 18'201411:11 AK4
To: Fox, Tim
Cc [ranfoni[huck;[e-mail]
Subject: RE: Ansley at Roberts Lake
Attachments: ANSLEYPRELIK4 STREAM PLANSU3l8l4.pdf, Riffle Sizing [a|cs.pdf
Tlm — thanksforthecomment .
We sized the riffle materials using a shear stress analysis, (unit wt. of water x hydraulic radius x slope) and compared
those values to the Shield's curve for particle mobility, using Rosgen's data. I've attached a summary of the calculations
for both reaches, looking at the bankfull stage and 2x bankfull stage (roughly the 10 year storm).
As for the bentonitepellets, we've found that they really help seal up the voids between the step boulders that the filter
fabric and smaller stone sometimes cannot seal. The bentonitevvou|d be placed away from flowing water and steps
would be taken to limit downstream migration. Once it's in place, it's buried by smaller stone and becomes an inert plug
in the backMUzone. |f you strongly object to its use, vve can take it out of the detail.
In looking back at the drawings for the permit submittal, I realized that you may not have the latest. VVe did afew
updates in February that | may have failed to pass along toClement. So, I've attached the latest plans in case that's true.
From: Fox, Tim
Sent: Tuesday, March 1O 20148:48AM
/m:
Cc: Cranford, Chuck; Clement Riddle
Subject: Ansley at Roberts Lake
Hope you are well. I am reviewing the Ansley at Roberts Lake Project and have a few questions for you.
How are you sizing the rock material used in-stream for riffle construction.
9 The use of bentonite used for in-stream structures. Is there an alternative solution so bentonite does not have
to be used?
|amin the field today but should bein the office most of the day tomorrow. | can get the approval out once these two
items are addressed.
Thanks,
Tim
Tim Fox

North Carolina Dept. of Environment and Natural Resources
Asheville Regional Office
DivisionofVVaterResources — VVater[lua|ityPrograms
2O9OU.S.7OHighway
Svvannanoa,N[2Q77Q
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