SW6190503_AddInfo_20190612

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
S. DANIEL SMITH
Interim Director
Mr. Stuart Anderson
Interplan, LLC
604 Courtland Street, Suite 100
Orlando, FL 32804
NORTH CAROLINA
Environmental Quality
June 12, 2019
Subject: Request for Additional Information
Stormwater Permit No. SW6190503
KinderCare Learning Center
Harnett County
Dear Mr. Anderson:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on May 7, 2019. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
l . The stormwater narrative incorrectly states that the requirements for stormwater
treatment are to retain the 1-year storm, attenuate the 2- and 10-year storm, reduce total
suspended solids by 85%, and reduce nutrient loading rates. The Stormwater
Management Regulations at 15A NCAC 02H .1000 require treatment of a 1-inch rain
event in a Primary SCM in accordance with the Minimum Design Criteria laid out in 15A
NCAC 02H .1050-.1062.
2. The stormwater narrative and supplemental forms use a variety of terms to describe the
stormwater control measures (SCM), such as bioretention pond, dry pond, rain garden,
bioretention swale, and rain swale. It is unclear what each supplemental form refers to
and which SCMs are intended to provide treatment. For example, the supplemental form
for a dry pond is presumably referring to the system labelled `Bioretention Pond" in the
northwest corner of the site. A supplemental form was submitted for a treatment swale,
but no treatment swale is indicated on the plans. Please use consistent, clear terminology
that references the SCMs named in the Stormwater Design Manual. Also note that dry
ponds and treatment swales are not primary SCMs and thus cannot be used alone to
provide treatment for runoff.
3. Please provide calculations for the water quality volume based on a 1-inch rain event
using one of the allowable methods in Part B of the Stormwater Design Manual.
DNorth Carolina Department of Environmental Quality I Division of Energy, Mineral and Land Resources
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_ 512 North Salisbury Street 1 1612 Mail Service Center I Raleigh, North Carolina 27699-1612
NORTH CAROLINA
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4. Please provide pre -development and post -development drainage area maps for the site.
The post -development maps should break down the areas draining to each SCM.
5. The invert of both outlet pipes in Inlet #11 is the same. Is there a weir or other diversion
device that routs runoff in a particular direction?
6. Many applicable fields in the Supplement EZ forms were left blank. Please complete all
of the fields in the Supplement EZ forms.
7. For the infiltration system:
a. The Supplemental EZ form indicates that the hydraulic conductivity of the soil is
5 inches per hour; however, there is no mention of soil testing in the geotechnical
report. Soil testing to verify the hydraulic conductivity is required for all
infiltration systems (Infiltration MDC 1).
b. Pretreatment is required for all infiltration systems (Infiltration MDC 4).
c. Calculations are required to show that the water quality volume will drain within
72 hours (Infiltration MDC 5).
8. For the bioretention system:
a. The detail on Sheet C4.1 shows the bioretention media depth as 30 inches with
mulch on the surface and the stormwater narrative indicates that there will be
trees in the bioretention cell. The minimum media depth for any bioretention cell
with trees or shrubs is 36 inches (Bioretention MDC 5). In addition, the
landscape plan on Sheet L1 shows that the bioretention area will be Bermuda sod
and does not show any trees. Please revise whichever is incorrect.
b. The Supplemental EZ form indicates that the hydraulic conductivity of the soil is
5 inches per hour; however, there is no mention of soil testing in the geotechnical
report. Soil testing is required to show that the in -situ infiltration rate is at least 2
inches per hour. Otherwise, an underdrain with internal water storage (IWS) is
required for the bioretention cell (Bioretention MDC 4). This is shown on the
detail on Sheet C4.1 but it is not shown on the plan and the Supplement EZ form
indicates that there is no IWS.
c. Please specify on the plans that the media P-index shall not exceed 50
(Bioretention MDC 7).
d. The detail on Sheet C4.1 indicates that the bioretention cell surface is at elevation
335.5, whereas the plans and Supplemental EZ form show elevation 333.5.
9. If the pond in the northwest corner is intended to be designed as a dry pond, it must be
designed with an outlet at the surface to allow it to fully drain between rain events. If it is
to be designed as a bioretention pond the peak attenuation orifice must be lowered to no
more than 18 inches from the bottom of the pond, and routing calculations must show
that the peak attenuation elevation from the design storm is no greater than 24 inches
above the planting surface.

10. Level spreaders are not required prior to discharging stormwater from an SCM. In
addition, runoff should not be discharged perpendicular to the level spreader to avoid
short-circuiting the level spreader. A rip rap apron or other form of erosion control can be
used in lieu of a level spreader; however, if a level spreader is to be used please provide
calculations and additional details to show that it meets the requirements of Chapter C-9
of the Stormwater Design Manual.
11. Please provide calculations that show that the inlet to the pond in the northwest corner is
designed to prevent erosion during the peak flow from the 10-year storm. If a rip rap
apron or other erosion control device will be used for the outlet, please also provide
calculations to show that it is also sufficient (General MDC 4).
12. A maintenance access must be shown on the plans. The maintenance access must be at
least 10 feet wide, have no greater than 3:1 slopes, and extend to the nearest right of way.
The maintenance access and SCMs must also be shown in a permanent recorded
easement (General MDCs 8 and 9).
13. 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:
htlps:Hedoes.deq.nc.gov/Forms/SW ProjectSubmittal
Please note that this request for additional information is in response to a preliminary review.
The requested information should be received by this Office prior to July 12, 2019, or the
application will be returned as incomplete. The return of a project will necessitate resubmittal
of all required items, including the application fee. Please reference the State assigned project
number SW6190503 on all correspondence.
If you need additional time to submit the information, please submit your request for a time
extension to the Division at the contact below. The request must indicate the date by which you
expect to submit the required information. The Division is allowed 90 days from the receipt of
a completed application to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject
to enforcement action pursuant to NCGS 143-215.6A.
If you have any questions concerning this matter please feel free to contact me at
[e-mail] or [phone].
Sincerely,
Corey Anen
Environmental Engineer
Stormwater Program
cc: Fayetteville Regional Office