20090430 Ver 3_Modifications_20100824

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community infrastructure consultants
August 16, 2010
Mr. Thomas Brown
US Army Corps of Engineers
Raleigh Regulatory Field Office
331 Heritage Trade Drive, Suite 105
Wake Forest, NC 27587
Mr. Ian McMillan
Division of Water Quality
401 Wetlands Unit
2321 Crabtree Blvd., Suite 250
Raleigh, NC 27604

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DENR -WATER QUAD i
WETLANDS AND STOM V-ATER BFWICH
RE: Johnston County Airport ERSA Permit Modification Request (USACE Permit No. SAW-
2009-00846 and Certification No3822)
Mr. Brown and Mr. McMillan:
On behalf of Johnston County Airport (Airport), WK Dickson is requesting modifications to the
above referenced 401 Certification and 404 Permit. During the final design phase for project
bidding and the Land Quality permitting process several design modifications were made that
affected jurisdictional impacts. Also, a wetland impact calculation error was discovered. This
modification request details those changes and includes a set of bid plans.
During the Land Quality permitting phase temporary wetland impacts were increased to
accommodate temporary erosion control measures such as sediment basins. Following
construction these features will be removed. The disturbed area will be returned to pre-
construction contours and seeded with a permanent wetland seed mix. Temporary wetland
impacts are now 3.75 acres. These features are shown on Sheets C-7A, C-8, and C-11 of the plan
set.
Another significant alteration to the plans was placing the proposed culvert offline to allow for the
existing Reedy Branch channel to remain open during construction. This construction sequence
will significantly reduce opportunities for in-channel erosion during high flow events during
construction and will allow the channel and culvert construction phase to be completed faster than
an in-line culvert. This will also allow for faster stabilization and reduced erosion. This design
modification results in 133 linear feet of additional stream impact. Buffer impacts also increase by
2,154 square feet in Zone 1 and 3,812 square feet in Zone 2. These features are shown on sheets
C-11, C-12, C-15, and C-16.
The previous permit application included a wetland impact calculation error wherein wetland
impacts were not calculated within the riparian buffer overlay. Correcting this error results in
1.20 acres of additional permanent riparian wetland impact.
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The table below summarizes the previously permitted impacts, modified impacts, and mitigation
needs.
Johnston County Air ort ERSA Modified Jurisdict ional Impact Summary
Original Modified Mitigation Mitigation Remaining
Permitted Impacts Units Units Mitigation
Impacts August 2010 Needed Purchased Units
Temporary Riparian

Wetland Impacts (ac) 0.17 3.75 NA NA NA
Permanent Riparian

Wetland Impacts (ac) 7.73 8.93 17.9 10.9 7.0
Stream Impacts (If) 685 818 1,636 0 1,636
Zone 1 Riparian

Buffer Impacts (sgft) 441496 46,650 139,950 0 139,950
Zone 2 Riparian

Buffer Impacts (sqft) 28,474 32,286 48,429 0 48,429
The Airport has made an initial mitigation purchase from EBX of 10.9 acres of Riparian Wetland
Mitigation Units. The Airport is requesting that the remainder of the mitigation needs be procured
from EBX. These will be purchased prior to project construction and USACE and NCDWQ will be
notified that all mitigation has been satisfied.
Please confirm your agreement to these impact modifications and mitigation approach or provide
questions/comments concerning the proposed ERSA mitigation. As previously discussed, the
Airport is not pursuing construction of the Corporate Area at this time. The Airport is bidding the
project and seeks to start construction in Fall 2010. Thank you for your prompt attention to these
important items.
Sincerely,
W.K. Dickson & Co., Inc.
Daniel Ingram
Project Manager
Attachments
cc: Carroll Triplett, WK Dickson
Ray Blackmon, Johnston County Airport
Chastity Clark, NCDOT DOA
Project file, 80324.00.CA