SW4190901_NCDEQ Stormwater Response Letter_1/20/2020

January 10, 2020
North Carolina Department of Environmental Quality
ATTN: Corey Anen
450 West Hanes Mill Road, Suite 300,
Winston-Salem, NC 27105
RE: Request for Additional Information
Stormwater Permit No. SW4190901
O'Reilly Auto Parts Lexington, NC #3
Davidson County
Corey,
We received email comments from you on August 15, 2019. Below are responses to
your comments:
Comment 1: In Part III.4 of the SWU-101 application, please provide the contact
information for the local jurisdiction for building permits.
Response 1: Contact for local jurisdiction added.
Comment 2: In Part IV.10 of the SWU-101 application, each drainage area in the table
should represent one SCM. Therefore, the entire drainage area to the sand
filter should be presented in one column.
Response 2: All drainage areas have been revised.
Comment 3: In Part IV.10 of the SWU-101 application, please fill out the second table
and provide a breakdown of built -upon area for the site.
Response 3: Built upon area updated on all forms.
Comment 4: Please complete and resubmit a maintenance plan and agreement using the
most up -to- date version of O&M EZ.
Response 4: 0&M EZ updated per comment.
Comment 5: Please complete and submit a signed and sealed copy of the Supplement
EZ form. This can be found on our Stormwater Design Manual website.
Response 5: 0&M EZ updated per comment. Signed and Sealed
Comment 6: Please provide calculations showing that the outlet from the sand filter is
adequately designed to prevent erosion from the 10-year storm [I 5A NCAC
02H .1050(5)].
Anderson EngineeringInc.com
2045 W. Woodland, Springfield, Missouri 65807 • Phone: [phone] • E-mail: [e-mail]

Response 6: Rip Rap calculations added to stormwater report and rip size updated
Comment 7: Please show a maintenance access and easement that meets the requirements
of General MDC 8 and 9 [15A NCAC 02H.1050(8) & 15A NCAC 02H
.1050(9)].
Response 7: Maintenance easement added to plans. Sending to O'Reilly for
description writing.
Comment 8: On Sheet Cl. 1, Key Note C 19 should reference Sheet C 1.7 in addition to
Sheets C1.10, 1.11, and 1.12 for the sand filter design.
Response 8: This has been revised on sheet C1.1 and C1.3.
Comment 9: Please provide a detail of the outlet control structure for the sand filter
including the inverts of any overflow devices.
Response 9: Details of Storm Trap system updated showing outlet box.
Comment 10: Calculations must be provided to show that the sand chamber has enough
storage above the sand surface to store at least 50% of the design volume
and the sediment chamber has enough storage above any permanent pool
to store 50% of the design volume. This volume shall be calculated
below the invert of the first overflow device.
Response 10: Storm Trap details show the required volume on Sheet 1.0 of the design
plans. There is no desired permanent pool. SO% of the design volume is
in each chamber of the sand filter/sed basin.
Comment 11: The sand filet detail on Sheet C 1.7 (StormTrap Sheet 1.0) should show the
underdrain pipes and how they will be embedded in the sand layer.
Response 11: Underdrains shown on sheet 1.0 and sheet 2.0 of the StormTrap Plans
Comment 12: Please provide the design information for the underdrain pipes and
calculations to show that they will be sufficient to convey drainage from the
sand filter. Calculation guidance can be found in Part B of the Stormwater
Design Manual.
Response 12: The Underdrains are treated like and orifice. The orifice equaton for the
underdrain pipes is included on the 2.0 sheet of the StormTrap plans.
Comment 13: Please add a note to the plans that the sand filter must be maintained to
have a drawdown of at least 2 in/hour at the sand surface [15A NCAC 02H
.1056(8)].
Anderson EngineeringInc.corn
2045 W. Woodland, Springfield, Missouri 65807 • Phone: [phone] - E-mail: [e-mail]

ANDERSON A' ENGINEERING
EMPLOYEE OWNED
Response 13: NOTE added to sheet 2.0 of StormTrap plans on sheet C1.7 of plans.
Comment 14: Please provide at least one clean -out pipe at the low point of each
underdrain line [15A NCAC 02H .1056(9)].
Response 14: Cleanouts added to underdrains on StormTrap sheets.
Comment 15: Please provide plans for the Family Dollar to verify built -upon area and
proper drainage into the sand filter system.
Response 15: We are trying to obtain the plans from the County. At this time is does
not appear they are available.
Comment 16: 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: https://edocs.deg.nc.gov/Forms/SW Project Submittal
Response 16: NOTED.
Sincerely,
Dylan Gideon P.E.
Anderson Engineering
ATH/djg
Anderson EngineeringInc. corn
2045 W. Woodland, Springfield, Missouri 65807 • Phone: [phone] • E-mail: [e-mail]