20061302 Ver 2_More Info Received_20080905

A R T I F E X i n c
ENVIRONMENTAL DESIGN
2363 Blake Street, Suite 202
Denver, CO 80205
[phone] phone
[phone] fax
www.artifexed.com
September 2, 2008
Ms. Cyndi Karoly
410 Oversight/Express Review Permitting Unit
1650 Mail Service Center
Raleigh, NC 27669-1650
RE: North Carolina Museum of Art-Museum Expansion Project
Stormwater Management Plan
House Creek [030402, 27-33-13, C, NSW]
Dear Ms. Karoly:
Flo-1301, Ua
rL-43 V(

We have reviewed the request for more information dated August, 4 2008 regarding the Stormwater
Management Plan for the North Carolina Museum of Art-Museum Expansion Project (DWQ Project #
06-1302). We have revised the plans where necessary and provide the following responses.
Please note the following responses, and find the attached supplemental application package.
1. The vegetated shelf comment seems to refer to the east side of the pond, as shown in the
grading on SW106. This was not shown due to the fact that this area represents the existing
dam embankment, which we chose not to disturb, and changes of these elevations have an
impact on flood control and water quality volumes.
In order to expedite the review, we have submitted a revised plan including an aquatic shelf on
the east side of the pond. We have modified grading to provide equivalent water quality and
flood control volumes. Our intention is to provide the required shelf grades, and to continue the
seeding appropriate for the near embankment region, as specked on the planting plan.
As previously submitted, the west side of the pond will be occupied by the stormwater wetland.
2. The outlet control device and outfall structure for the existing detention pond are existing
features. Revisions to the outlet control device to provide the water quality volume drawdown
are shown on Sheet SW104 detail 7. We have enclosed a copy of the survey of the outfall
structure in the supplemental package.
The outfall channel downstream of the pond is an existing riprap lined Swale, with stone 9-24"
in nominal diameter. This channel provides a stable outfall for flows greater than the ten year
storm, for both pre-development and post-development conditions. Calculations are included
in the supplemental package.
• Page 2
September 3, 2008
Enclosed are the revised SW106 Stormwater Wetland Plan, the outfall surrey, and the outfall channel
velocity calculations. Please contact me directly if you have additional questions regarding this
application, or if you require any further information.
Sincerely,

Stephen H. Blake, P.E.
Director of Engineering
Encl.
Cc: Dan Gottlieb, NCMA
Jeffrey Lee, PBC&L
Walt Havener, LHPA
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AR T I F E X E I n c 2363 Blake Street, Suite 202
Denver, Co 80205
t. 720 855 3721 f. 720 855 4210
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