Full Gospel Tabernacle Church - 18080144-01_Comment Response Letter

Draper Aden Associates
Engineering • Surrelvng • Ernvrormrented Services
114 Edinburgh SOLI(h Drive
Suitt 200
Cary, North Carolina 27511
919,827.0864
www.dailxom
03/29/2019
Corey Anen
NCDEQ, Stormwater Program
512 North Salisbury Street
Raleigh, NC, 27604
RE: Full Gospel Tabernacle Church
Draper Aden Associates Project No.18080144-01
Dear Mr. Anen:
Please see the responses to your comments below in bold. If you should have any questions or further
comments, please address them to Austin Jackson at [e-mail] or 336-414-6841.
1. The drainage area and impervious area used in the calculations and shown in the Supplemental
EZ form are different from those in the application. Please correct the discrepancy.
1. All drainage areas and impervious areas have been coordinated. The total drainage
area is 8.66 acres and the impervious area is calculated as 5.55 acres. Please note this
impervious area is for all future planned development and the pond is sized
accordingly to the Master Plan on sheet C5.1.
2. The average depth of the wet pond should be calculated using Equation 2 or 3 in the Wet Pond
Chapter of the Stormwater Design Manual.
2. The average depth is calculated as pond surface area over the pond volume (DAvs
Vpp/App). See excel cell E11.
3. Please provide a cross -sectional detail of the wet pond and details for any outlets or overflows
from the wet pond.
3. A cross sectional detail has been added on sheet C6.0.
4. Please provide a landscaping plan or detail for the vegetated shelf that meets the requirements
in the Wet Pond MDC 11.
4. A landscape detail has been added to sheet C6.0.
5. The drain time must be calculated using the runoff volume from the 1" storm, not the maximum
storage volume in the wet pond.
5. The drain time is calculated from runoff of the 1" storm. See excel sheet cells C22 —
E32.
6. In accordance with Wet Pond MDC 5, the volume of the forebay must be between 15 and 20% of
the volume of the main pool.
6. After conversation with Annette Lucas it has been determined that the forebay is to
be 15 -- 20% of the required pond volume not the provided pond volume. This sets
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Draper Aden Associates
+� Engineering • Surveying • EttrrtnrrtrtetrPnlSerricczs
114 Editibm-gli South Drive
Suitc 200
Cary, Nor(h Carolina 27511
919.827.0864
www.daaxom
a stationary value to target. The forebay volume is greater than 15% of the provided
main pond volume. See excel cells El and El 8. In this case, the forebay is greater
than 15% of the provided pond volume. (15% x 60,231 ft3 = 9,035 ft3 < 9,674ft)
7. In accordance with General MDC 4, engineering calculations must be provided to show that the
inlets and outlets of SCMs are designed so that they do not cause erosion during the 10-year
storm.
7. The concrete weir discharges into a channel. This channel has been designed to be
lined with Class B riprap two feet deep. This is based on a design for permissible
velocity in a channel. See Design of Roadside Channels. Hydraulic Design Series No.
4 from the US Department of Commerce. Publication No. FHWA-NHl-08-090
8. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other
documents. Pdfs must be uploaded using the form at:
htt s: edocs.de .nc. ov Forms SW Project Submittal
8. All revisions will be submitted per this comment.
Sincerely,
Draper Aden Associates
l t
Austin Jackson
Project Designer
cc: file
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