20001195 Ver 9_More Info Received_20090820

CDM
301 South McDowell Street, Suite 512
Charlotte, North Carolina 28204
tel: [phone]
fax: [phone]
August 19, 2009
Mr. Ian McMillan
North Carolina Division of Water Quality
Wetlands/401 Certification Unit
2321 Crabtree Boulevard, Suite 250
Raleigh, NC 27604-2260
Subject: Charlotte-Douglas International Airport
Airport Drive Roadway Improvements
Pre-Construction Notification for Nationwide 14
CDM Project No. 76560-67708
Dear Mr. McMillan:
t' ?? ? E 1
UdETLr?,DENNpWAT R G' A ITY
G !Nr ER 8PANGH
Following field meetings held July 29, 2009 between CDM, Charlotte-Douglas Airport Staff, and
Alan Johnson of the Mooresville Regional DWQ office; several modifications were discussed
relative to the subject project.
Enclosed please find the following:
Letter to Alan Johnson addressing his comments from the field meeting and noting
revisions to be completed
• Revised PCN Project Form Page 5 showing revised stream impacts
• Revised Drawing Sheet C-9 with bubbled areas indicating those items added since your
previous review.
With this information you should have the necessary paperwork to complete the approval of the
request for a Nationwide 14 permit for the subject project. If you have any further questions or
need any additional information please don't hesitate to contact me.
Sincerely,
qjnathan S. Lapsley, P. .
Project Manager
Camp Dresser & McKee
Enclosures
cc: Mr. Elmo Langley, CLT
P: \Charlotte- Douglas Airport\Airport Drive Project\Permits\401-404\McMillan 08192009.doc
consulting • engineering . construction • operations
CDM
301 South McDowell Street, Suite 512
Charlotte, North Carolina 28204
tel: [phone]
fax: [phone]
August 14, 2009
Mr. Alan Johnson
North Carolina Division of Water Quality
Surface Water Protection Section
610 East Center Avenue, Suite 301
Mooresville, North Carolina 28115
Subject: Charlotte-Douglas International Airport
Airport Drive Roadway Improvements
NCDENR Request No. 00-1195-V9
CDM Project No. 76560-67708
Dear Mr. Johnson:
CDM, NCDENR, and representatives from Charlotte-Douglas Airport met onsite on July 29,
2009 to discuss the subject project and NCDENR concerns. During this meeting four items
were identified as potential improvements to the design for this project. For various reasons,
three of these items are not recommended to be implemented by CDM. Below is a summary
of the recommendations discussed at our field meeting, with a description of investigations
completed by CDM, and our recommendation regarding each improvement noted in italics.
Re-route 42-inch storm drain pipe to discharge to the existing detention pond on the
west side to separate the flow from the storm water collection system and improve
water quality.
The 42-inch pipe in question is being re-routed from its existing location to move it out of the
fill embankment. This pipe is currently connected to the storm water collection system and does
not directly discharge to the pond. It is the intent of CDM's design to keep the existing systems
"as is" and not contribute more flozv to the pond as investigating the capacity of the pond zvas
not the intent of this project. CDM recommends the 42-inch pipe be connected to the storm
zvater collection system as shozvn in the original submittal.
2. Delete the rip-rap apron at the confluence of the new open channel with the existing
Taggart Creek Tributary.
Rip-rap zvas included at this location because the new open channel meets the existing
tributary at a right angle. Concentrated storm water flows through the open channel will have
to make this turn zvhich could lead to erosion of the channel bottom. CDM recommends the rip-
rap remain as shozvn in the original submittal to prevent erosion of the channel.
consulting • engineering • construction . operations
? j -1-
Mr. Alan Johnson
August 14, 2009
Page 2
3. Re-route the 18-inch outfall carrying stormwater collected from the new roadway to
allow overland flow of the run-off before entering the proposed open channel. The
overland flow will improve water quality of the runoff before entering the Taggart
Creek Tributary.
CDM investigated several options for addressing this request including, overland flozv
discharge through a rip-rap apron, plunge pools, and level spreaders. The re-routing of the pipe
is complicated lnj the alignment of relocated zvater, sewer, and overhead electric lines
perpendicular to the proposed I8-inch pipe discharge forcing the discharge elevation to be
raised significantly. While the use of a plunge pool or step pool structure could be utilized to
create sheet flozv from the 18-inch pipe discharge, this flozv will likely transition to shallozv
concentrated flow before it reaches the top of the nezv channel bank. The 10-year peak discharge
from the I8-inch pipe is approximately 22 cfs. If this much concentrated flozv travels dozvn the
side of the channel (with 2H:1 V side slopes), from top to bottom, the shear stress and velocity
will far exceed the capacity of the permanent matting. To avoid long term issues zvith erosion
in this area CDM recommends that the 18-inch pipe be joined to the stormzater system as
shown in the original submittal.
4. Install live staking on the new open channel banks.
vVe will revise the drawing to include this revision and agree this will aid in stabilizing the
open channel banks.
Thank you for your time discussing these issues on the phone with me over the past
several weeks and reviewing the above recommendations. Please review these issues and
let me know at your earliest convenience if you agree with our concerns. Following your
approval of this letter we will resubmit the revised PCN sheets and a revised construction
drawing for final review and approval.
If you have any questions please do not hesitate to contact me at the number above.
Sincerely,
Jonathan S. LapsltP'
Project Manager
Camp Dresser & McKee
cc: Mr. Elmo Langley, Charlotte-Douglas Airport
P-\Charlotte-DouglasAirporVAirportDriveProject\Permits\401-404\Johnson08142009. doc
C. Proposed Impacts Inventory
1. Impacts Summary
1a. Which sections were completed below for your project (check all that apply):
? Wetlands ® Streams - tributaries ? Buffers
? Open Waters ? Pond Construction
2. Wetland Impacts
If there are wetland impacts proposed on the site, then complete this question for each wetland area impacted.
2a. 2b. 2c. 2d. 2e. 2f.
Wetland impact Type of jurisdiction
number - Type of impact Type of wetland Forested (Corps - 404, 10 Area of impact
Permanent (P) or (if known) DWQ - non-404, other) (acres)
Temporary T
W1 ? P ? T ? Yes ? Corps
? No ? DWQ
W2 ? P ? T ? Yes ? Corps
? No ? DWQ
W3 ? P ? T ? Yes ? Corps
? No ? DWQ
W4 ? P ? T ? Yes ? Corps
? No ? DWQ
W5 ? P ? T ? Yes ? Corps
? No ? DWQ
W6 ? P ? T ? Yes ? Corps
? No ? DWQ
2g. Total wetland impacts
2h. Comments:
3. Stream Impacts
If there are perennial or intermittent stream impacts (including temporary impacts) proposed on the site, then complete this
question for all stream sites impacted.
3a. 3b. 3c. 3d. 3e. 3f. 3g.
Stream impact Type of impact Stream name Perennial Type of jurisdiction Average Impact
number - (PER) or (Corps - 404, 10 stream length
Permanent (P) or intermittent DWQ - non-404, width (linear
Temporary (T) (INT)? other) (feet) feet)

S1 ®P ? T Culvert
Replacement/Rip Taggart Creek ? PER ® Corps
15
274
Rap Tributary ® INT El DWQ
S2 ®P ? T Culvert Taggart Creek ? PER ® Corps 15 140
Daylighting Tributary ® INT ? DWQ

S3 ®P ? T Transition to
Taggart Trib w/ Taggart Creek ? PER ® Corps
22
37
Rip Rap Tributary ®INT ?DWQ
S4 ? P ? T ? PER ? Corps
? INT ? DWQ
S5 ? P ? T ? PER ? Corps
? INT ? DWQ
S6 ? P ? T ? PER ? Corps
? INT ? DWQ
3h. Total stream and tributary impacts 451
3i. Comments: Approximately 180 feet feet of existing culvert pipe will be removed and this area restored to an open channel
to carry the attenuated intermittent stormwater flows from the adjacent retention pond to the existing open channel tributary of
Taggart Creek.
Page 5 of 11
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