SW5231201_Response To Comments_20240410

II • ArchitectureEngineering An Employee Owned Company
Environmental
10/ 1 Land Surveying
Companies
April 1, 2024
Brianna Holland, Environmental Engineer
DEMLR Post-Construction Stormwater Program
North Carolina Department of Environmental Quality
Division of Energy, Mineral, and Land Resources
Raleigh Regional Office
1612 Mail Service Center
512 North Salisbury Street
Raleigh,NC 27699-1612
Re: Mavis Tires#2094
Stormwater Permit No. SW5231201
Dear Ms. Holland:
We are in receipt of your comments dated March 19, 2024, requesting additional information
regarding the project noted above. Our responses are indicated below in bold italic text and are
as follows:
1. As designed, the SCM is just a sand filter and not a dry detention basin & sand filter(the
sand filter SCM includes the sand layer in addition to the storage provided above the sand
layer in the sand chamber and sediment chamber). Please revise the submittal materials as
needed to reflect this.
Response: Narrative has been revised to remove discussion of dry detention pond.
2. Since this project drains to the Tar River(a Nutrient Sensitive Watershed), please ensure
that the project is also compliant with the Tar-Pamlico Nutrient Strategy Rules 15A
NCAC 02B .0731.
Response: The sand filter reduces the nitrogen load to 7.63 lbs and the phosphorus
load to 0.52 lbs. The remaining required reduction will be accomplished by purchasing
nutrient credits from an acceptable NC credit bank.
3. Per the provided USGS topographic map, surface water exists within the project
area. Revise the package accordingly to account for this surface water and provide
vegetated setbacks. All surface water that appears on the latest USGS topographic
map must be accounted for and depicted on the plans per 15A NCAC 02H .1017
(10). Please do the following:
3420 Toringdon Way,Suite 210 • Charlotte,North Carolina 28277 • T(704)565-7070 • www.blcompanies.com

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Response: The site boundary on the USGS map was drawn incorrectly. There is no
surface water on the site.
a. Please include the on-site surface water area in Section IV, 6 of the Application. This
information should also be included on Line 4 of the Cover Page of the Supplement-
EZ Form.
Response: The site boundary on the USGS map was drawn incorrectly. There is no
existing surface water on the site.
b. Please recalculate the total project area as shown in Section IV, 7 of the Application.
This information should also be updated on Line 2 of the Cover Page of the
Supplement-EZ Form, on Lines 5 & 6 of the Drainage Areas Page of the Supplement-
EZ Form, and in the table in Section IV, 10 of the Application.
Response: Property area has been updated to be the area treated by BMP(2.08Ac)
c. Please recalculate the project percent impervious area as shown in Section IV, 8. This
information should also be updated on Line 18 of the Drainage Areas Page of the
Supplement-EZ Form and in the table in Section IV, 10 of the Application.
Response: Property area has been updated to be the area treated by BMP(2.08Ac)
and percent impervious revised appropriately.
d. Provide vegetated setbacks on the plans per 15A NCAC 02H .1017 (10).
Response: A 50 foot setback from the existing pond on the adjacent parcel has
been provided.
4. Per the provided narrative, "Mavis Tire will occupy 0. 99 acres of the size while the
balance of the site will remain under separate ownership and be developed at a later
date."Note that if the property is being subdivided, deed restrictions will need to be
recorded limited the amount of BUA that is allowed on this adjacent property, or the
offsite area will need to be accounted for as 100% BUA in the sizing of the SCM.
Response: The remainder of the drainage area to the pond on Lot 2 has been designed
to 100%BUA.
5. Per General MDC 8 and 9: All SCMs and associated maintenance accesses shall be
located in permanent recorded easements. The SCM shall be shown and labeled within
the easement.The SCM system includes the side slopes, forebay, riser structure, SCM
device, and basin outlet, dam embankment, outlet, and emergency spillway. Maintenance
accesses shall extend to the nearest public right-of-way. Revise the easement to meet
these requirements.
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See 15A NCAC 02H .1050 (8) and(9) for additional information on maintenance
accesses and easements.
Response: The maintenance access easement for the BMP runs from the SWM
Easement through the proposed storm drain easement and uses the common access
easement to the R/W
6. PD-1 Drainage Area Map—Please ensure the drainage areas provided correspond to the
proposed contours and stormwater piping system provided. It appears that there is
currently a discrepancy. Note that drainage areas do not always directly correspond to
property lines.
Response: Offsight drainage has been added to more accurately describe the drainage
to and through the site.
7. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
i. Line 7—Per 15A NCAC 02H .1017(10)the minimum required vegetated setback
width is 30 ft.
Response: 50'Buffer has been shown.
ii. Lines 8 & 9—Please revise as needed.
Response: Revised
b. Drainage Areas Page:
i. Complete the requested information in the "Entire Site" Column. Note that the
"Entire Site" Column is intended to represent the entire project area, and not just
the drainage area to the SCM, which is provided in the adjacent column.
Response: Entire Site column has been added.
ii. Line 19—Per the provided narrative, this value is 1 inch.
Response: Revised
iii. Line 20—Per the provided narrative, this value is 4,839 cf.
Response: Revised
iv. Line 21 -Per the provided narrative, the "Simple"method was utilized.
Response: Revised
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c. Sand Filter Page:
i. Line 4—Are there contaminated soils located on-site? If there are,you are not
allowed to use SCMs that allow for infiltration(per General MDC 2).
Response: There are no contaminated soils.
ii. Line 9—Please show the drawdown orifice used to dewater the SCM in the plans.
Note this is distinct from the drawdown orifice shown at the water quality
elevation, as this is intended to dewater the SCM completely during maintenance.
Pumps are recommended instead of drawdown orifices.
Response: Pump will be used for dewatering
iii. Line 11 —The maintenance access must comply with MDC 8.
Response: Maintenance complies with MDC 8
iv. Line 18—This is required in order to ensure compliance with Sand Filter MDC 1.
Response: Per the geotechnical report no ground water was encountered in
any onsite boring, therefore it is believed ground water is at an elevation below
298.Additional SHWT test has been requested and will be forwarded to you as
soon as it is complete.
v. Line 26—This could not be confirmed as a sediment chamber stage storage table
was not provided.
Response: Forebay Stage Storage chart included in Appendix B
vi. Line 27—The physical depth of the sediment chamber is the depth from the
lowest bypass invert(Line 35) to the excavated bottom of the sediment chamber
(Line 25).
Response: Top of Forebay Wall is 305 to the bottom of the forebay at 303 is
24".
vii. Line 28 —Per Line 24 there is no permanent pool.
Response: Corrected
viii. Line 29—Revise this item or the plans for consistency. The elevation is listed as
304.60 on the plan view and 305.50 on the detail, so it is unclear what the
correct elevation is.
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Response: 305.50 is correct
ix. Line 30—Provide. This is required in order to ensure compliance with Sand Filter
MDC 2.
Response: Volume has been included.
x. Line 32—This could not be confirmed as a sand chamber stage storage table was
not provided.
Response: Stage storage table has been included in appendix B.
xi. Line 33 —The physical depth of the sand chamber is the depth from the lowest
bypass invert (Line 35)to the lowest excavated point of the sand chamber(below
the underdrains).
Response: 48"
xii. Line 34—The ponding depth of the sand chamber is the depth from the lowest
bypass invert(Line 35) to the top of the sand layer(Line 31).
Response: 12"
xiii. Line 35 —This appears to be 305.35 per riser structure detail provided on the
plans.
Response: Revised to 306.50
xiv. Line 36—This appears to be an outlet control structure/riser structure.
Response: Revised
xv. Line 37— Stormwater flow may be distributed over the surface of the sand
chamber via a level spreader, a pipe distribution system, or a series of weirs.
Response: Distributed by the forebay weir
xvi. Line 39—This value refers to the depth of the sand layer being provided above
the underdrain pipe.
Response: 24"
8. General MDC 4—Please provide calculations showing that the inlets and outlet of the
SCM are stable in accordance with this MDC.
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Response: These have been included in Appendix C.
9. Per 15A NCAC 02H .1003 (5), stormwater outlets shall be designed so that they do not
cause erosion downslope of the discharge point during the peak flow from the 10-year
storm event as shown by engineering calculations.
Response: Rip Rap calculations for the ourlet pipe have been included in Appendix C.
10. Per Sand Filter MDC 1, the minimum separation between the lowest point of the sand
filter system and the SHWT shall be two feet for open bottom designs. Provide
documentation that the SHWT was determined within the footprint of the SCM and show
the SHWT elevation on the cross-sectional detail of the plans. Per the boring location
diagram provided, it does not appear that the location of the SCM was investigated.
Response: SHWT investigation has been ordered and will be provided upon its
completion. Per the geotechnical report no ground water was encountered in any
onsite boring, therefore it is believed ground water is at an elevation below 298 which
would be 2'below the bottom of the trench.
11. Per Sand Filter MDC 2: Please ensure that the volume stored in each chamber of the sand
filter is equivalent. Please provide a separate stage-storage table for the sediment
chamber portion and a sand chamber portion so that the volumes can be compared.
Response: Sediment Chamber is designed to hold 20% of the water quality value as
stated in the NCDEQ SWM Manual. Stage Storage charts for forebay and main
chamber have been included in Appendix B.
12. The Sand filter Area calculations provided in the narrative seem to have had a printing
issue and were not shown. Please ensure the minimum surface area is provided, guidance
can be found in the manual with Sand Filter MDC 3.
Response: This has been fixed.
13. Please provide a clean-out pipe at the low points of the underdrain lines on the plans per
Sand Filter MDC 9. Note that cleanout pipes shall be capped.
Response: Cleanout pipes have been added.
14. The provided O&M Form is outdated and therefore incomplete. Please use the most up to
date form, which can be found on our website at the following address:
https://www.deq.nc.gov/about/divisions/energy-mineral-and-land-
resources/stormwater/stormwater-program/stormwater-design-manual (O&M EZ Form).
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NOTE: It is recommended to get a second copy of this form signed&notarized for the
Applicant's records (it will be helpful when they go to record it with the Register of
Deeds).
Response:Acknowledged
15. Please ensure the electronic repository is complete. The following items were noticed to
be missing:
• Official documentation supporting the titles and positions held by the persons listed in
Contact Information, item la per 15A NCAC 2H.1003(e). (Required per
Section VI, 11)
Response: Official Documentation has been provided
• Official documentation displaying the corporation is active and in good standing with
the NC Secretary of State. (Required per Section VI, 11)
Response: Official Documentation has been provided in this submittal
• A partial Supplement-EZ was uploaded.
Response: Supplemental EZ form has been uploaded
• O&M Agreement
Response: Updated O&M Agreement has been uploaded
16. Provide PDFs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other
documents, and a response to comments letter briefly describing how the comments have
been addressed.
a. PDFs must be uploaded using the form at:
https://edocs.deq.nc.gov/Forms/SW-Supplemental-Upload
b. Hard copies must be mailed or delivered to the following address:
i. For FedEx/UPS:
Brianna Holland
f512 N. Salisbury Street, Office 625Y
Raleigh,NC 27604
ii. For USPS:
Brianna Holland
1612 Mail Service Center
Raleigh,NC 27699-1612
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iii. Hand Delivery:
Please reach out to me prior to hand delivering a submission to make sure that I
(or someone else in my group)will be able to receive the submission. Do not
leave the package in the foyer with the security guard.
We trust this addresses your concerns. Should you require additional information, feel free to
contact me at 704-851-7102.
Sincerely,
Andrew R. Mueller, P.E.
Senior Engineer
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