SW1200501_Responce to Comments_20201009

10 Shaping Communities Together
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August 18, 2020
Mr. Jim Farkas
Environmental Quality Section
North Carolina Department of Environmental Quality
1612 Mail Service Center
512 North Salisbury Center
Raleigh, North Carolina 27699
RE: Response to Comments
Fairview Elementary School — Car Rider Lane Improvements
Permit No. SW1200501
Buncombe County, North Carolina
Dear Mr. Farkas,
Thank you for your review of the stormwater plan submittal for this project. Below are our
responses to your comments listed in the Request for Additional Information letter, dated July 31,
2020. Your comments are shown followed by McGill's responses. All plan sheets that have been
revised will include revision clouds and dated accordingly with this re -submittal. See revision block
on each sheet for corresponding revision.
1. Section II, 2 — Since all three parcels are owned by the Buncombe County Board of
Education, you do not need to consider the proposed SCMs as off-stie facilities. The only reason
it would be beneficial to consider these proposed facilities as off -site facilities is if the Board of
Education plans on selling off either of the lots that the proposed SCMs are located on in the near
future. Please let me know if you would like to keep either proposed SCM as an off -site facility as
there is some legal paperwork that needs to be completed to ensure the long-term functionality
of the off -site facility.
Section II, 2 has been revised to indicate a High Density Project. The "Offsite" drainage box has
been unchecked. We do not anticipate the Buncombe Board of Education selling off any lots
within the Fairview Elementary School area in the foreseeable future.
2. Since there are two proposed SCMs for this project, the drainage area to each should be
reported in Section IV, 10 of the Application. Since the Limit of Disturbance (LOD) is being used
as the project area, any portion of the drainage area to these proposed SCMs that is outside the
LOD should be considered as off -site drainage.
Section IV, 10 of the application has been revised to delineate both drainage areas separately.
Off -site drainage areas to BioCell #2 have been included.
MCG ILL ASSOCIATES 55 BROAD STREET, ASHEVILLE, NC 28801 / 828.252.0575 / MCGILLASSOCIATES.COM

3. No off -site areas are shown in Section IV, 10 of the Application. Either Section IV, 11 is not
needed or the off -site drainage areas should be shown in Section IV, 10 of the Application.
Off -site areas have been included in Section IV, 10 of the application.
4. Please provide a hard copy of the Supplement-EZ Form with an original signature (Section
V & Section VI, 3).
Acknowledged, a hard copy of the Supplement-EZ Form will be provided with this re -submittal.
5. Please ensure that the entire O&M Agreement Form is included in the submission (Section
V & Section VI, 3). The O&M Agreement Form uses Macros to generate the needed pages based
on the information entered on the cover page. Please ensure that all of the pages have loaded
(Enable editing, enable Macros, click on the "Click to update Manual' link about midway down the
cover page). The form will need to be re -signed.
Acknowledged, a complete O&M Agreement Form will be provided with this re -submittal.
6. Please provide an additional copy of the Application Form (Section VI, 1). Only an original
hard copy was provided. The additional copy does not require an original signature.
Acknowledged, an additional copy of the Application Form will be provided with this re -submittal.
7. Please provide a USGS topographic map that clearly shows the project area (Section VI, 6).
A USGS topographic map has been provided in the updated stormwater report.
8. The provided SCM design calculations are lacking (Section VI, 7). Please provide
calculations for the following:
a. The Design Volume — Using either the Simple Method (For the entire drainage area to
each proposed SCM) or the MRCS Discrete Curve Number Method (For the pervious and
impervious parts of the entire drainage area to each proposed SCM) and the design storm
of 1.0 inches (See later comment).
b. The actual depth of the Design Volume in each SCM — This value should be
calculated/interpolated from a stage -storage table (see later comment).
c. Peak Attenuation Volume — Provide calculations showing how the peak attenuation
volume is calculated.
d. The actual depth of the Peak Attenuation Volume in each SCM — This value should be
calculated/interpolated from a stage -storage table (see later comment).
e. Media Drawdown Rate — Calculations showing that a drawdown rate of at least 1 inch
per hour can be maintained through the media and underdrains (Bioretention MDC 9).
Items "a" through "d" are addressed in comments further below. For item "e", a Media Drawdown
Rate calculation has been provided in the updated report. The calculation shows that we meet
the minimum drawdown rate of 1 inch per hour.

9. Please clearly show and dimension the project boundary being used for this project, including
the bearings and distances (Section VI, 8i).
Sheet CE-101 now contains the bearings and distances of the property lines of the outermost
boundary. Internal lot lines between parcels owned by Buncombe County Board of Education
were not provided.
10. Please clearly identify and dimension the BUA for this project for both existing and proposed
conditions (Section VI, 8j). The information shown in the calculations, Application, and
Supplement-EZ Form should be verifiable on the plans.
Exhibits showing both the pre -development and post -development conditions of the site have
been provided in the updated report, delineating the impervious areas within the project limits.
11. Please delineate the wetlands on the plans or provide a note stating that no wetlands exist.
Provide documentation of the qualifications and identity of the individual who made this
determination (Section VI, 8m).
No wetlands exist on the site and a note has been placed on sheet CE-101. This determination
was made by our Environmental Services Manager, Jon Swaim.
12. Please show the drainage areas for the proposed SCMs on the main set of plans (Section
VI, 8c).
Drainage areas for both SCMs have been shown on sheet C-105.
13. Please provide a soils report showing the Seasonal High Water Table (SHWT) elevation
information for the two proposed SCMs (Section VI, 9). The Web Soil Survey should be used in
conjunction with, not as a replacement to actual on -site borings.
The project soils report has been provided in the updated report. Per soil borings B-5 and B-6,
the SHWT is more than 10-15' below the surface of the SCM.
14. Since the Property Owner is the Applicant, Section IX should not be included. If Tony Baldwin
is a more appropriate person to be signing on behalf of the Board of Education, he should be
listed in Section III, 1 & should sign Section X (This would require a new, original signature on the
Application). If Clark Wyatt will remain the Applicant signatory, I can, with your permission, cross
out the provided signature in the original, signed, hard -copy of the form in Section IX (The form
would not need to be resigned, but the electronic version of the form would need to have this
section crossed out as well). Please let me know how you would like to address this.
Clark Wyatt is the appropriate signatory for this application. Since changes have been made to
the overall application to address other comments listed in this review, a newly signed application
is being provided with this resubmittal.

15. Please refer to the latest version of the Stormwater Design Manual for the latest design
requirements (The calculations appear to reference an old version of the Manual). The Manual
can be found at the following link: https://deg.nc.pov/about/divisions/energy-mineral-land-
resources/energy-mineral-land-permit-guidance/stormwater-bmp-manual
The Simple Method calculation spreadsheet has been updated to reference the latest NCDEQ
Stormwater Design Manual.
16. The design volumes do not appear to be calculated correctly (General MDC 1). Please use
either the Simple Method (for the entire drainage area to each proposed SCM) or the MRCS
Discrete Curve Number Method (For the pervious and impervious parts of the entire drainage
area to each proposed SCM). More information can be found in the Design Manual, Part B.
The Simple Method has been used to calculate the design volumes for both SCMs. Calculations
for each SCM are provided in the report. In order to meet Buncombe County stormwater
requirements, the design volume calculation is based on the 1-year storm, not the 1-inch.
17. Per plan sheet C-505, the side slopes of the proposed SCMs appear to be steeper than 3:1
(General MDC 3). Please revise.
SCM details on sheet C-505 have been revised to show the 3:1 slopes. Our grading plan has
been confirmed to show 3:1 slopes as well.
18. Please ensure that there is at least a 2 foot separation between the lowest excavation point
of each proposed bioretention cell and the SHWT associated with these locations (Bioretention
MDC 1).
Per the soils report that accompanies the updated stormwater report, no groundwater was found
at depths of 10-15' below the surface at the location of each SCM.
19. If the proposed SCMs are being used for peak attenuation, please show the peak attenuation
elevation on the plans (Bioretention MDC 3).
Both SCMs have been deepened an extra foot in depth (to the 24" max depth) to achieve
additional volume storage above the 1-year design. The total available storage for each SCM is
now provided with a stage -storage calculation, included in the revised report.
20. Please provide a stage -storage table for the proposed SCMs so that the temporary ponding
depth (Bioretention MDC 2), peak attenuation elevation (Bioretention MDC 3), and design volume
(General MDC 1) values can be verified.
Stage -storage table has now been provided in the revised report.
21. Please provide a detailed plan view of the proposed SCMs (15A NCAC 02H .1042(2)(h)).
This will, among other things, allow for verification of the locations and quantities of the
underdrains.

A new sheet, C-106, has been added to the plan set that shows a detailed plan view of each
SCM. Details, such as the underdrains, have been shown and labeled.
22. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
a. Lines 7-10 — Since there are no surface waters located on -site, these items should
be "N/A"
b. Drainage Areas Page:
a. Please complete the Entire Site column. This is an accounting of the area within
the project area. Lines 4, 8, 9, & 17-19 do not need to be completed.
b. Lines 5, 7, 10, 13, 16, & 18 — Revise as needed in accordance with earlier
comment. This should be an accounting of the entire drainage area to each
proposed SCM, not just the impervious areas within the project area.
c. Line 17 — The design storm depth for this project is 1.0 inches (Per 15A NCAC
02H .1017(5)).
c. Bioretention Cell Page:
a. Line 9 — Please specify in the Additional Information box (Line 44).
b. Line 18 — Please include this item.
c. Line 19 — The bottom of the bioretention cell is the excavated bottom of the SCM,
not the top of the media layer.
d. Line 20 — This should be based on the actual temporary ponding depth associated
with the design volume (Based on the design storm of 1.0 inches).
e. Line 27 — Plan sheet C-505 indicates that the underdrain diameter of bioretention
cell 1 is 6 inches whereas 8 inches is shown in the Supplement-EZ Form. Please
revise for consistency.
f. Line 37 — This value should be "<50" since a specific value was not specified.
g. Lines 39, 42, & 43 are required, please complete these items.
For Cover Page items, lines 8-10 only allow for "Yes/No" answers, so they are left as "No". Line
7 has been revised to "N/A". For Drainage Area items, fields have been updated with totals. Line
17 has been left at 2.67 inches (spreadsheet rounds to 3 inches) to meet Buncombe County's
stormwater requirement of meeting the 1-year storm, not the 1-inch. For Bioretention Cell items,
Line 9 has been revised to Drawdown Orifice. Line 18 refers to a note in Line 44 that SHWT was
not found at depths of 10-15' below the surface (see soils report). For Line 20, the actual ponding
depth to meet the design volume is 12 inches. An additional 12 inches is provided above this for
extra storage volume.
23. 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:
httns://edocs. deg. nc. pov/Forms/SW Proiect Submittal
As previously mentioned in each of the comments above, the below has been included in this
submittal for final erosion control permit approval:
• Two (2) revised complete plan sets
• One (1) revised erosion control report

• Two (2) revised Stormwater Applications (one original and one photocopy)
• One (1) revised Stormwater EZ Form
• One (1) revised Operation & Maintenance Agreement
If you have any questions or require additional information, please feel free to give me a call at
828-707-6749.
Sincerely,
McGILL ASSOCIATES, P.A.
i
SCOTT BURWELL, PE
Project Manager
Enclosures
P:A2019\19.00154-BuncombeBOE-Fairview Elem Car Rider LaneADesign\Permits\Stonnwater\jfl7aug20 Response Letter.docx