20001195 Ver 12_More Info Letter_20120105

Ow
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue
Governor
Mr Jerry Orr
Charlotte Douglas International Airport
Post Office Box 19066
Charlotte NC 28219
Charles Wakild P E
Director
January 5 2012
Subject Property Charlotte - Douglas International Airport
UT to Coffey Creek [030834 11 137 4 C]
Dee Freeman
Secretary
DWQ Project # 00 1195v12
Mecklenburg County
REQUEST FOR MORE INFORMATION MODIFIED STORMWATER MANAGEMENT PLAN
Dear Mr Orr
On May 13 2010 the Division of Water Quality (DWQ) issued a revised 401Water Quality Certification
to impact 1 148 acres of 404 Wetlands 21 669 linear feet of streams 7 522 acres of Open Water (ponds)
to order to expand the Charlotte Douglas International Airport Condition 10 of this certification requires
that a stormwater management plan be submitted to and approved by the DWQ
On December 12 2011 the DWQ received a stormwater management plan (dated November 21 2011)
for the West Boulevard relocation project from your consultant Mr Ronald Geiger PE of HDR The
DWQ has reviewed the stormwater management plan and has found it to be incomplete
Please provide the following information so that we may continue to review your protect
Additional Information Requested
Bioretention Cell #1
1 Does the drainage received by the pipe under West Blvd contain runoff from any
impervious area? If not, it may be better to bypass that runoff around the cell
Bioretention cells work best treating runoff from impervious areas
2 The plans and supplement show the temporary pool at 711', but it should be at the
overflow weir at 710 5'
1617 Mail Service Center Raleigh North Carolina 276991617
Location 512 N Salisbury St Raleigh North Carolina 27604
Phone 919 - 807 6300 \ FAX [phone] \ Customer Service 1877-623 6748
Internet www ncwaterguality ora
An Equal Opportunity \ Affirmative Action Employer
NorthCarolina
Admiall'y

Mr Jerry Orr
January 5 2012
Page 2 of 3
3 The supplement states the planting elevation is at 708 75', but the plans show 708' to
709 5' Bioretention cells must be flat throughout their section to function properly
4 The supplement shows the bottom of the media at 708 58', but it should be the planting
elevation minus the 3' of planting media
5 The supplement shows the depth of sand as an elevation This should be shown as the
depth (thickness) of the sand layer in feet
Bioretention Cell #2
1 On sheet 14B, a spot elevation is needed at the overflow to show that it is to be built to
elevation 704 (as done on sheet 14A)
2 The supplement states the planting elevation is at 702 35', but the plans show 702 7' to
703' Bioretention cells must be flat throughout their section to function properly
3 The depth of sand on the supplement should be shown in feet, not inches
4 The supplement shows the top of the upturned elbow at 700 03 , but the plans show it at
699 7 Please make it consistent
Both Bioretention Cells
1 Please be sure that any changes are consistently reflected on all documents (plans, calcs,
supplement forms, O &M forms, etc )
2 Plans and calculations must sealed, signed, and dated by an appropriate NC licensed
design professional
3 Please verify the drainage area delineations for the BMPs They do not appear to follow
the contours
4 The surface of the cells are sloped Bioretention cells must be flat, not sloped Please
revise
5 The plans show ponding over 12" Ponding shall not be greater than 12" Please revise
6 An original signed O &M Agreement form must be submitted None were submitted It
can be downloaded from http //portal ncdenr ora/web /wq /ws /su/bmp ch12

Mr Jerry Orr
January 5 2012
Page 3 of 3
7 The SHWT elevation was left blank on the supplements Also, a soils report must be
provided that states what the SHWT is based on a boring widim the footprint of each of
the proposed cells
8 The type of grass sod must be specified Also, it should be specified that the sod shall not
be from a farm grown in tight clay soil that would restrict flow through
9 Both supplements state that a vegetated filter strip (VFS) is provided, but there are not
any Note however that a properly designed VFS, per chapter 8 of the BMP Manual, is
not required for bioretention cells
10 Please provide supporting calculations for the drawdown and underdrain sizing for each
cell
Please submit this information or otherwise address this request within 30 calendar days of the date of this
letter Please call Mr Robert Patterson PE at [phone] if you have any questions regarding these
comments or would like to set up a meeting
Sincerely
,� r q
Annette Lucas
Wetlands Buffers and Stormwater Compliance and
Permitting (WeBSCaPe) Umt
AML /aml/rdp
cc U S Army Corps of Engineers Asheville Regulatory Field Office
Alan Johnson DWQ Mooresville Regional Office
Samar Bou ghazale DWQ Mooresville Regional Office
Michael Parker DWQ Mooresville Regional Office
Robert Patterson PE DWQ Stormwater Umt
File Copy
Ronald Geiger PE HDR 128 S Tryon St Suite 1400 Charlotte NC 28202 5004
Femme 001195vl2CharlotteDouglaslntLA irport(Mecklenburg)_SW_Mod_Hold docx