SW5240601_Response To Comments_20241024

000.
•:
TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
Project: SBI Headquarters Addition & Renovation
Date: 10/09/2024
Contact: Trevor Morrison
Phone: [phone]
Email: [e-mail]
Comments from NCDEQ review has been addressed below. Our responses are in red.
Construction Document Submittal First Submittal Comments—06/10/2024
Construction Document Submittal Second Submittal Comments—10/09/2024
NCDEQ REVIEW COMMENTS
Jacob Beeker (919-707-9214,[e-mail])
1. Per the provided USGS topographic map, there appears to be a surface water located
within the project area (located in the northeast corner of the project area). Please
ensure the following:
a. The surface water is clearly shown on the main set of plans (per 15A NCAC 02H
.1042(2)(g)(iii)).
b. Clearly identify and delineate the top of banks of the stream in the main set of
plans (Section VI, 8h). If it is not possible to delineate the banks of the surface
water (as would be the case for a narrow stream), please show the centerline of
the surface water and provide a callout listing the surface area of that surface
water that is within the project boundary. Note that the surface area of the
surface water is the area between the top of the banks of the streams and normal
pool of impounded structures. Ensure the vegetated setback is measured
horizontally from the top of bank of each side of streams for all perennial and
intermittent stream waters within and adjacent to the site.
c. The required vegetated setback/buffer from the surface water is clearly shown on
the main set of plans (per 15A NCAC 02H.1042(2)(g)(iii)) and Section VI, 8p.
d. The surface area of this surface water is indicated in Section IV, 6 of the
Application and the Supplement-EZ Form (Cover Page, Line 4).
e. The surface area of this surface water is excluded from the project area in
Section IV, 7 of the Application and the Supplement-EZ Form (Cover Page, Line
2 & Drainage Area Page, Entire Site Column, Line 5).
f. The percent BUA for the project area is recalculated in Section IV, 8 of the
Application and the Supplement-EZ Form (Drainage Area Page, Entire Site
Column, Line 18).
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g. The design is revised as needed to ensure that it complies with 15A NCAC
02H.1003(4).
TG Response: "SITE" boundary has been updated to show proper limits of
construction/disturbance. There are no surface waters located within project area; there
is surface water in the property's overall parcel, but these are not being modified or
impacted. C-100 OVERALL SITE PLAN is provided to show the location of the creek
with respect to project area, with associated riparian buffers.
2. Per 15A NCAC 02H.1003(3)(b), off-site areas that are not bypassed around an SCM
must be accounted for at their full build-out potential (in proposed conditions). The full
build-out potential of these off-site areas can be determined by having the property
owner(s) enter into a legal agreement limiting the amount of off-site BUA and drainage
area draining from the off-site areas to the SCM(s) or by assuming that these off-site
areas are 100% BUA (their full build-out potential).
TG Response: There is no offsite drainage, and the pond is sized for all future buildout.
The pond is sized for an additional 55,417-SF of future impervious.
3. This project is located within the Neuse River Basin and is subject to the requirements
set forth by 15A NCAC 026.0711 and .0233, which include nutrient loading requirements
(or Runoff Volume Matching) and the presence of 50-ft riparian buffers, respectively.
The SNAP tool is the approved tool for regulatory compliance with stormwater
requirements in all Nutrient Management Strategy watersheds, including the Neuse.
Please provide calculations demonstrating compliance with 15A NCAC 02B.0711 and
provide the necessary riparian buffers (see comment 1) as required by 15A NCAC
02B.0233.
TG Response: C-100 OVERALL SITE PLAN is provided showing the location of the
creek with associated 50-ft Riparian buffers.
The SNAP tool version 4.2.0 has been added to the stormwater narrative. Per the
SNAP tool, nutrient buydown will be purchased for nitrogen.
4. The parking area located north of the Wet Pond cannot be considered to be captured
and treated in the SCM as is. It is noted that this area will sheet flow to the SCM's main
pool and forebay, but the runoff that flows into the main pool in this manner is not
considered treated, since it does not flow into the forebay, then into the main pool. This
short-circuiting is not allowed per Wet Pond MDC 4. For this area to be considered
"captured and treated," it must be directed into the forebay like the rest of the captured
BUA, so that it may be properly treated. Please revise the project package so that the
BUA associated with this impervious surface is captured and treated or remove it from
the BUA accounting associated with the SCM.
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TG Response: A permanent diversion ditch is provided directly south of the parking area
to direct flow into the forebay.
5. Consistency
Please revise the following for consistency:
a. The Existing BUA to be Removed is listed as 126,000 sf on the Supplement-EZ
form but is listed as a total of 3.38 ac (147,233 sf) on the provided plans.
TG Response: The existing BUA to be Removed has been corrected on the
Supplement-EZ form as 147,233-sf.
6. Application
a. Section IV, 4 — Please revise this value to correspond to the project area
delineated in the main set of plans, prior to the accounting of surface waters.
TG Response: Section IV, 4 has been revised to correspond to the project area
delineated in the main set of plans (15.29 AC).
b. Section IV, 6, 7, and 8— See Comment 1.
TG Response: There are no surface waters located within project area; there is surface
water in the property's overall parcel, but these are not being modified or impacted. C-
100 OVERALL SITE PLAN is provided to show the location of the creek with respect to
project area, with associated riparian buffers.
Sections IV 6, 7, and 8 now have corresponding quantities to the 15.29-ac per the actual
project area.
7. Supplement-EZ
a. Cover Page
i. Line 2 — Please revise to match Section IV, 7 of the Application.
TG Response: Section IV, 7 has been updated to 15.29-ac.
ii. Lines 4 and 7— See Comment 1.
TG Response: There are no surface waters located within project area; there is surface
water in the property's overall parcel, but these are not being modified or impacted. C-
100 OVERALL SITE PLAN is provided to show the location of the creek with respect to
project area, with associated riparian buffers.
b. b. Wet Pond Page
i. Line 12 —The information on Line 55 is noted, but please revise this to
say "Yes" to demonstrate compliance with the MDC.
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TG Response: Line 12 on Wet Pond Page has been updated to indicate "Yes."
ii. Line 37 — If possible, please adjust the rounding in Excel so that the
proper orifice diameter can be shown. If this is not possible, you may add
a note to Line 55 indicating the diameter.
TG Response: Line 37 has been updated to round to nearest hundredth. Proper
diameter is shown.
8. Plans
a. Please include the SCM maintenance access on the plans and ensure that it
meets General MDC 8. Please note that maintenance accesses must extend to
the nearest right of way and include the entire SCM footprint, including all outlet
devices.
TG Response: SCM maintenance access has been included on sheet C-501 GRADING
& DRAINAGE PLAN (LOGISTICS BUILDING).
b. The profile view of the Forebay indicates that the top of sediment storage is at
both 325.5 and 326.5. Please revise to indicate one elevation for the top of
sediment storage.
TG Response: Top of sediment storage is 325.5. This has been updated on sheet C-
803 NOTES & DETAILS.
9. O&M Agreement
a. The Bottom Elevation refers to the elevation associated with the bottom of
sediment storage. Please revise the value provided for both the Forebay and
Main Pond.
TG Response: Bottom elevation has been updated to display 324.5 in both the forebay
and main pond sections.
10. Calculations
a. Please include screenshots of the SNAP tool to demonstrate compliance with
15A NCAC 02B .0711. See Comment 3.
TG Response: SNAP tool has been provided as part of the stormwater narrative in the
calculations section.
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5410 TRINITY ROAD, SUITE 102 • RALEIGH, NC 27607 • PHONE [phone] • FAX [phone]• WWW.TIMMONS.COM