20090259 Ver 1_More Info Letter_20090407

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NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
April 7, 2009
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
COL William E. Johnson
North Carolina National Guard
4105 Reedy Creek Road
Raleigh, NC 27602
DWQ EXP No. 09-0259
Wake County
Subject Property: NCNG Raleigh Armed Forces Reserve Center Joint Force HQ
REQUEST FOR MORE INFORMATION
Dear COL Johnson:
On April 6, 2009, the Express Review Program of the Division of Water Quality (DWQ) received your
application dated March 30, 2009, to fill or otherwise impact 173 linear feet of intermittent stream and
10,480 square feet of Zone 1 Neuse River basin protected riparian buffer, and 6,533 square feet of Zone 2
Neuse River basin protected riparian buffer, to construct the proposed North Carolina National Guard
Headquarters at the site. The DWQ has determined that your application will require additional
information. Please provide the following information so that we may continue to review your
project and prevent denial of your application as required by 15A NCAC 2H .0506:
Additional Information Requested
1. Wet Ponds:
a. The average depths of both ponds are inadequate. North Carolina regulations establish 3.0
feet as the minimum average depth for wet pond. Please redesign each pond by increasing the
nominal pond depth in order to increase the average depth.
b. Please also note that, the computation of the average depth, and hence required surface area
of a wet pond, is an iterative (often a 2-step) process. For instance, if assigned initial depth is
4.0 feet (i.e. assumed average depth), and the average depth is computed as 3.22 feet, then a
second SA/DA value shall be read corresponding to the new average depth of 3.0 feet and the
percent imperviousness.
c. The orifice size for wet pond 1 is inadequate. For both ponds, please select an orifice size in
the range of 1.5 - 2.0 inches.
d. This office recommends the use of a submerged orifice with a typical configuration as shown
in Figure 10-4 in the NC DWQ BMP Manual.
e. Since no soil report and seasonal high water table information were included in the
application, please specify on the construction plans that the soil material at the bottom and
sides of each wet pond shall be verified by a geotechnical engineer to be a silty-clay or clayey
material, and shall be compacted to minimize infiltration and thereby maintain the water at
the permanent pool level.
f. Please revise the anti-flotation calculations using the outer dimensions of the riser structure
for the computation of volume, and hence weight of water displaced.
401 Oversight/Express Review Permitting Unit
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
Location: 2321 Crabtree Blvd., Raleigh, North Carolina 27604
Phone, 919-733-17861 FAX: [phone]
Internet: http://h2o.enr,state.nc.us/ncwetlands/
NorthCarolina
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An Equal Opportunity 1 Affirmative Action Employer
North Carolina National Guard
Page 2 of 3
April 7, 2009
2. Bioretention Areas:
a. Please revise the cross sections to depict the underdrains and cleanout pipes in the plan views
as close as possible. Please extend the underdrains along the base of the cell as long as they
could possibly be (to the left/west side) to clearly mimic how they are shown in the plan
view.
3. Constructions plans should describe the installation or construction sequence of the BMPs. In
particular, clearly describe how and when the Sediment Basins (S & EC structures) would be
converted to Stormwater BMPs.
4. For FES 42 and FES 48, please design the outlet structure as a triangular or trapezoidal riprap channel
to dissipate as well as convey the water. Please show cross sections of channels.
5. Please provide an enlarged circular scour hole at the confluence of FES 21 and 48 to prevent scouring
in the receiving draw.
6. Planting Plans:
a. Bioretention - Grass bioretention areas must be planted with sod as discussed in the pre-
application meeting. Prepared seed mixes are not acceptable. Centipede grass sod is highly
recommended.
b. Wet Pond - Please identify the nursery source(s) of your proposed littoral shelf plants.
Provide sizing information for each plant (4" container, etc.). Additionally, although the
following plants are listed in the BMP manual, it is recommended that you choose other
options:
i. Zizania aquatica (Wild rice) - bird fodder
ii. Hehanthus angustifolia (Swamp sunflower) - anaerobic intolerant, poor survivability
iii. Hibiscus moscheutus - no drought tolerance (recommend Hibiscus coccineus or other
choice)
iv. Hymenocallis euloe (spider lily) - does not grow in NC, also no local nursery source
7. Riparian Buffer Impacts - Please enumerate riparian buffer impacts on plan sheet C 1201 in square
feet. Converting submitted acreage to-square feet does not match the square footage listed on the
PCN form. Also, in Stream Impact 41, 0.036 acres of Zone 2 is mislabeled as Zone 1.
Please respond within five (5) days of the date of this letter by sending two (2) copies of the above
information in writing. The Express Review Program is a process that requires all parties to participate in
a timely manner.
This letter only addresses the application review and does not authorize any impacts to wetlands, waters or
protected buffers. Please be aware that any impacts requested within your application are not authorized (at
this time) by the DWQ.
Please contact Joseph Gyamfi or Lia Myott Gilleski at 919-733-1786 if you have any questions regarding or
would like to set up a meeting to discuss this matter.
Sincerely,
'0' Cyndi Karoly, Supervisor
North Carolina National Guard
Page 3 of 3
April 7, 2009
401 Oversight/Express Review Permitting Unit
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Article Addressed to:
COL William Johnson
NC National Guard
4105 Reedy Creek Rd
Raleigh NC 27602
DWQ EXP 09-0259 Wake Co
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