SW3230603_Response To Comments_20230821

rBRECEngineering I Planning I Environmental
Ice
August 21, 2023
NCDEQ-DEMLR
Brianna Holland
512 N. Salisbury Street, Office 640E
Raleigh, NC 27604
RE: Dollar General Store #25122— Rockwell
Stormwater Permit No. SW3230603
The following responses are pertaining to the final review letter that was received on August 21,
2023.
1. C) BUA: The project does not appear to meet the requirement of Runoff Treatment
(15A NCAC 02H .1002(43)). For a project to meet Runoff Treatment, the net
increase in BUA must be captured and treated in one or more primary SCMs. The
driveway's BUA does not appear to be captured and treated. If it is not practicable
to capture and treat all of the required BUA, the bypassed areas can be permitted
as a low-density area (provided that the bypass area meets the low-density
requirements). Occasionally, there are situations where it is not practicable to
capture all of the required BUA in an SCM and it is not possible to permit the
bypass areas as a low-density area, these situations require a variance/waiver in
accordance with 15A NCAC 02H .1003(6). Revise the package as necessary and
indicate which of the options is being pursued..
R) The driveway stem contains 1,690 sq. ft. of BUA that cannot be routed to the SCM
due to topographic constraints. A variance is being requested for this area. We
have noted this in our report and in the updated supplemental form.
2. Supplement-EZ
C) lx hard copy of the complete, original Supplement-EZ Form is required per
Sections V& VI, 3 of the Application
a. Vegetated Setbacks
The following items are required per 15A NCAC 02H.1003(4) & .1017(10)).
1520 Meadowview Drive • [e-mail] , 336.844.4088
Wilkesboro NC 28697 www.brec.biz Cry

C) i. Cover, Line 7: While there is no surface water, and therefore no
vegetated setbacks associated with this project,please revise as 30 feet.
R) Revised.
C) ii. Cover, Line 8: The vegetated setback must remain vegetated, so please
fill in as "Yes" or"N/A."
R) Revised.
C) iii. Cover, Line 9: BUA proposed in the setback must meet 15A NCAC
02H .1003 (4) (cd), so please fill in as "Yes" or"N/A."
R) Revised.
C) iv. Cover, Line 10: Please fill in as "No" or "N/A."
R) Revised.
C) b. Drainage Area Information, Entire Site Column, Line 7: The entire site
column is an accounting of the entire project area and the drainage area
column is an accounting of the entire area draining to the SCM). The
"Entire Site" Column should include the area that is being treated by the
sand filter, so if 894 SF of offsite drainage area is being directed to the
sand filter, it is also part of the entire site. Please revise.
R) Revised entire site column to include off-site area that cannot be
redirected away from the SCM.
C) Note that offsite drainage area is area located on adjacent or upstream
property that the applicant does not own, and which generates runoff that is
draining onto the applicant's property, and which will be treated by the
currently proposed SCM.
R) Noted. The SCM design accounts for this off-site area at an assumed 100%
BUA.

C) Per 15A NCAC 02H .1003(3)(b) any off-site areas that drain to the SCM
must be accounted for at their full build-out potential. This can be
accomplished by having the property owners enter int a legal agreement
limiting the amount of BUA and drainage area directed from the off-site
property to the SCM or by assuming that the off-site area is 100%BUA(its
full build-out potential). Bypassing off-site drainage area around the SCM
is recommended.
R) Off-site drainage assumed to be 100% BUA.
C) If desired, you can clarify what the offsite BUA is in the "Additional
Information(Line 22)."
R) Noted in line 22.
C) Line 12: Please clarify the difference in parking area BUA between the
entire site and sand filter columns.
R) The difference of 1,690 sq. ft. is the portion of driveway stem that cannot
be routed to the SCM. A variance is being requested for this area.
c. Sand Filter
C) Line 2: Please revise the minimum required treatment volume per the
Calculations—Comment B below.
R) The difference between our calculations was due to rounding in our
internal spreadsheets. We have corrected that. The treatment volume
has also been revised to reflect our updated grading plan.
C) Line 6: Retaining walls, gabion walls or other engineered side slopes are
not shown on the plans; please revise to "No"unless these are proposed.
R) Revised.
3. C) 3. Plans
2x hard copies of revised sheets of the Application with the following corrections made:
(This item is required per 15A NCAC 02H.1042(2)(a) and per Section VI, 1 of the
Application)
C) a. Please ensure that the most up to date hard copies of the plans are submitted.
Email correspondence on 8/15/23 confirmed that hard copies will be provided
with the next submittal, and that the electronic copies were to be reviewed at
this time.

R) This submission and calculations is reflective of our most current plans. Our
grading plan changed in response to zoning comments after our initial NCDEQ
submission. No further changes are anticipated.
C) b. The Supplement-EZ, Line 3 states that level spreader is the mechanism for
distributing flow over the sand surface. Please call out the level spreader on the
plans.
R) The stone dam separating the chambers acts as a level spreader. We will update
the label.
C) c. Sheet C904, Sand Filter Detail 1:
i. The plan details shall include all conveyance devices, including inlet
device, bypass structure,pretreatment area, flow distribution device,
underdrains, outlet device, and energy dissipater. Please include the
elevations and dimensions of all conveyance devices and the emergency
spillway on the plan and section view per 15A NCAC 02H .1042 (2) (h)
(ii).
R) We have replaced detail C904 with a detailed view port of the sand filter on sheet
C202 that is to scale and includes the items referenced above.
C) ii. Please show the vegetated side slope of the SCM in the plan view per General
MDC 3.
R) Site slopes labeled as 3:1 in plan view.
C) iii. Please specify that the sand media be ASTM C33 or equivalent on the plans
per Sand Filter MDC 6.
R) Sand was previously noted as ASTM C33 on detail C904. All notes have been
moved to the revised detail on sheet C202.

4. C) 2. Calculations:
lx signed, sealed, and dated hard copy of calculations with the following corrections
made: (This item is required per Section VI, 7 of the Application)
C) a. Please ensure that calculations reflect the updates shown in the July 5, 2023
plans. Drainage areas and piping appear to have changed which has an impact on
various calculations.
R) Calculations are reflective of most current plans. See explanation above.
C) b. Please revise the water quality volume calculation(and subsequently the
discounted design volume.
WQV 3,630 * 1.0 in * 0.67 * 1.50 ac 3648 ft 3,636 ft
R) The discrepancy was the result of an excel rounding which has been corrected.
C) c. Sand Filter MDC 8 requires that the sand filter shall be maintained in a manner
that results in a drawdown of at least two inches per hour at the sand surface. If
the sand is 18 inches deep, the sand chamber should drain in 9 hours or less. To
find the maximum number of hours that stormwater should take to drain through
the sand chamber, divide the depth of sand by two inches per hour(the minimum
allowed infiltration rate). The drawdown in the calculations was provided as 24.8
hours.
R) See email correspondence.
Thanks,
BREC, PA