20201208 Ver 1_Culvert Update Sheets_20201120

Strickland, Bev
From: Johnson, Alan
Sent: Friday, November 20, 2020 9:44 AM
To: Perez, Douglas J
Subject: FW: [External] Re: griffith lake
Attachments: Griffith Lakes Culvert Update Sheets.pdf
20-1208 this is culvert designs for the crossing. Be sure to copy into LF file. Make sure they
are appropriate for the stream
DWR
Division of Water Resources
Alan D Johnson — Senior Environmental Specialist
NC Dept. of Environment & Natural Resources (NCDENR)
Division of Water Resources - Water Quality Regional Operations
610 East Center Ave., Suite 301, Mooresville, NC 28115
Phone: [phone] Fax: [phone]
E-mail correspondence to and from this address may be subject to the North Carolina Public Records Law and may be
disclosed to third parties unless the content is exempt by statute or other regulation.
From: Daniel Kuefler [mailto:[e-mail]]
Sent: Friday, November 20, 2020 9:36 AM
To: Johnson, Alan <[e-mail]>
Subject: [External] Re: griffith lake
I email. Do not click links or open attachments unless you verify. Send all suspicious email as an attachment to
141ov
Alan,
I've attached some more detailed culvert design sheets for Griffith Lakes that the engineers just sent over,
showing the internal sills. Please let me know if you need more information/details than this. Thanks,
Daniel
On Fri, Nov 20, 2020 at 9:00 AM Daniel Kuefler <daniel.kueflerkwetlands-epg.com> wrote:
Alan,

You are correct about the width - that must have been an oversight - it's about an 8' wide channel but base flow
is fairly low - about 3 feet. But, it is a flashy system with a lot of volume at high flow - which is why the need
for the large box culverts with baffles. To that end, the paragraph in the cover letter (pasted below) was taken
almost verbatim from a memo from the engineer when we asked them to provide details, but I see now that
there are no callouts/depictions for baffles/sills on the plans - I'll reach out to the engineer for a quick update to
show those - might even be able to get those to you before the end of the day -
Daniel
"Large box culverts with multiple internal baffles were introduced to create a primary channel for base flows
and secondary channel for higher flow events as well as to help retain the 1 to 2 ft of soil in the bottom of the
culvert added
for aquatic passage. Given the large contributing drainage areas and increasing upstream
development, there is no practical culvert design that would allow discharge rates that would not
require additional energy dissipation at the exit of the culvert. Multiple dissipation measures
were analyzed and the plunge pool lined with stone was found to be the least impactful as it most
effectively reduced velocities to the level needed to avoid downstream erosion of the stream
channel in the design events. The plunge pool was designed minimizing its dimensions to those
required by FWHA's HEC-14 Hydraulic Design of Energy Dissipators for Culverts and
Channels. The plunge pool stone is being set into the bottom of the measure and is
anticipated to partially silt in overtime."
On Fri, Nov 20, 2020 at 8:38 AM Johnson, Alan <alan.johnson o,ncdenr.gov> wrote:
The culvert are two 6 ft wide culverts, the channel is stated as 3 ft. It appears to be about 8
ft, but base flow is about 3 ft. I saw no design for baffles/sills in the culvert
DWR
MA41orr of Water Resources
Alan D Johnson — Senior Environmental Specialist
NC Dept. of Environment & Natural Resources (NCDENR)
Division of Water Resources - Water Quality Regional Operations
610 East Center Ave., Suite 301, Mooresville, NC 28115
Phone: [phone] Fax: [phone]

E-mail correspondence to and from this address may be subject to the North Carolina Public Records Law and may be
disclosed to third parties unless the content is exempt by statute or other regulation.
Daniel Kuefler
Wetlands & Environmental Planning Group
Leonard S. Rindner, PLLC
www.wetlands-epg.com
336.554.2728
Daniel Kuefler
Wetlands & Environmental Planning Group
Leonard S. Rindner, PLLC
www.wetlands-epg.com
336.554.2728

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