SW6230104_Response To Comments_20230414

III0^
McCLURE'"
1700 Swift Street, Suite 100
North Kansas City, MO 64116
P 816.756.0444
www.mccIurevision.com
April 14, 2023
0
w
Jim Farkas
512 N. Salisbury Street, Office 640E
v Raleigh, NC 27604
tN
a
N
Z Re: Dunn, NC Petco review comments — Request for Additional Information
Dear Mr. Farkas:
The purpose of this letter is to respond to the Request for Additional Information as provided on April 13, 2023.
Our comment responses are as follows:
Please correct the following issues with the stormwater narrative/calculations:
1 . The BUA value (48,265 sf), project area (73,050 sf), and percent BUA (61 %) do not correspond with
the other submittal items. Please revise as needed.
RESPONSE: The narrative has been revised to correspond with the application.
2. The minimum required treatment volume of the SCM should be based on the actual drainage area to
the SCM, not the project area.
RESPONSE: The SuppEZ form has been revised per this comment..
3. Infiltration System Design — This SCM is not an infiltration basin so this equation should not be used.
RESPONSE: Comment noted. We are not using infiltration.
Inlet protection refers to protecting the inlets that direct runoff into the SCM (typically pipes or swales)
from erosion.
RESPONSE: The site is drained by swales to the bio pond. Riprap is placed to protect from erasion'
Please correct the following issues with the plans: NOTE: These items are typically caught during the
administrative completeness review process. If these items were addressed as part of the administrative
completeness review, please direct the reviewer's attention to this.
1 . Please either delineate the wetlands located on -site on the plans or provide a note on the plans
indicating that there are no wetlands located on -site. This item is required per 15A NCAC
02H .1042(2)(g)(iii) and Section VI, 8m of the Application.
RESPONSE: Sheet C402, note 2 states this.
Per the provided USGS topographic map, there appears to be an intermittent stream running through
the property. Please include this surface water area and associated vegetated setback on the plans. This
item is required per 15A NCAC 02H .1042(2)(g)(iii) and Section VI, 8m of the Application. Relief from
this requirement may be allowed when surface waters are not present in accordance with 15A NCAC
02B .0714(3)(a).
RESPONSE: The adjacent east site is developed. Any previous drainage path has been diverted to the
highway ditch on the south side of the property.
W L

Please correct the following issues with the design of the bioretention cell:
1 . General MDC 4 — Please provide calculations showing that the inlets and outlet of the SCM are stable
in accordance with this MDC.
RESPONSE: Calculations for this are attached.
2. General MDCs 8 & 9 — Please clearly show the maintenance and access easement on the plans. It
should include the entire footprint of the SCM plus an additional 10 ft around the footprint to allow for
access, and should extend to the nearest public right- of -way.
RESPONSE: This easement is shown on sheet C402.
3. Bioretention MDC 1 — Please clearly indicate the lowest point of the bioretention cell (the bottom of the
gravel trench surrounding the underdrain lines). Please revise as needed.
RESPONSE: Detail sheet C105 section has been updated to show this.
Bioretention MDC 2 — Per the provided state -storage table, the design volume (shown as 3,674 cf in
the Supplement-EZ Form) is not able to be provided within 12" of the planting surface. Per the detail of
the outlet structure, the throat elevation is shown to be at elevation 171 .0' which is in excess of 12"
above the planting surface. Please revise as needed. The entire minimum required treatment volume
must be able to be provided above the planting surface and below the bypass invert. Please revise as
needed.
RESPONSE: The drainage was recalculated to be 1,987 cf. The detail on sheet C105 has been revised
accordingly.
5. Bioretention MDC 3 — Per the plans, the peak attenuation elevation for the SCM is shown at elevation
1 72.0' which is in excess of 24" above the planting surface. Please revise as needed.
RESPONSE: The drainage was recalculated to be 1,987 cf. The detail on sheet C105 has been revised
accordingly. Peak attenuation volume is 171.00
6. Bioretention MDC 4 — Based on the provided soil infiltration information, the in situ soil infiltration rate
is 0.019 in/hr. Since this is less than 2.0 in/hr, internal water storage (IWS) is required. Please ensure
that the top elevation of the IWS is shown on the plans. Please revise as needed.
RESPONSE: IWS was previously included and the top of pipe elevation is shown in the detail on sheet
105..
7. Bioretention MDC 5 — Please clearly indicate the depth of the media layer in the cross -sectional view of
the SCM. NOTE: The 24" media depth may only be used for bioretention cells that are not required to
have an IWS. Please revise as needed.
RESPONSE: Detail sheet C105 section has been updated to show this.
Please correct the following issues with the Application:
1 . Section IV, 7 — The stormwater narrative indicates that the project area is 73,050 sf =
1.68 ac which is different than the shown value (1 .67 ac). Please revise as needed.
RESPONSE: This has been revised.
2. Section IV, 8 — The calculations show 1.062 ac of BUA over a site area of 1.677 ac which equals
a %BUA of 63.3%. Please revise as needed.
RESPONSE: This has been revised.
Section IV, 9 — Since only 1 SCM is being proposed for this project, only one drainage area column
should be provided.
RESPONSE: We show two on the plans as the water is routed to the bio pond..

4. Section IV, 10 — The drainage area column should correspond to the actual drainage area to the SCM.
The plans with the drainage area delineations only show the drainage areas to the curb cuts that drain
to the SCM, not the entire drainage area to the SCM (for example, the surface area of the SCM and
any areas that drain directly to the SCM should be included in the drainage area to the SCM).
RESPONSE: The plan and applications have been revised to reflect this.
Please correct the following issues with the Supplement-EZ Form:
Cover Page:
1 . Line 2 — This value should correspond with the value shown in Section IV, 7 of the Application. Please
revise as needed.
2. Line 7 — Please refer to 15A NCAC 02H .101 7(10) for the vegetated setback width requirement.
RESPONSE: We do not have perennial waterbodies or streams, nor intermittent streams. This 30'
setback is not required.
Drainage Areas Page:
General:
1 . If the project area is not being subdivided, the new BUA should be listed on Line 10 and should be
broken down by type on Line 12.
RESPONSE: The plan and applications have been revised to reflect this.
Entire Site Column:
1 . This column should be an accounting of the entire project area. When asked for a "drainage area" for
the entire site, the entire project area should be used. All BUA located on -site (whether or not it drains
to the SCM) should be included in this column. The project area (Lines 5 & 6) should correspond to the
information shown in Section IV, 7 of the Application, the %BUA for the entire site (Line 18) should
correspond with the information shown in Section IV, 8 of the Application.
RESPONSE: The form has been revised to reflect this.
Drainage Area Column:
1 . Since only 1 SCM is being proposed for this project, only one drainage area column should be
provided and should include the entire drainage area to the SCM. The information in this column
should correspond with the drainage area column in the table in Section IV, 10 of the Application.
RESPONSE: We provided 2 drainage areas with separate inlet locations to the SCM..
2. Line 20 — This value should correspond with Line 22 on the Bioretention Page (see later comment).
RESPONSE: The plan and applications have been revised to reflect this.
Bioretention Page:
1 . Line 2 — Please provide this item. The minimum required treatment volume is calculated using either the
Simple Method or the Discrete NRCS Curve Number Method based on the drainage area to the SCM.
RESPONSE: This number was provided by analysis with the SCS method.
2. Line 18 — The provided value, 1 72.0', does not correspond to the information shown in the SHWT
report (use the higher of the two elevations shown in the SHWT report).
RESPONSE: The form is revised to include the SHWT number from the geotech report..
Line 19 — This item refers to the lowest point of the bioretention cell (the bottom of the gravel trench
surrounding the underdrain lines).
RESPONSE: This number has been revised and noted on sheet C105.

4. Line 21 — This refers to the surface area of the planting surface.
RESPONSE: The form has been revised to reflect this.
5. Line 22 — This volume refers to the volume that can be stored between the planting surface and the
invert of the lowest bypass. This volume must be as least as large as the minimum required treatment
volume.
RESPONSE: The form has been revised to reflect this.
6. Line 26 — The provided value, 1 in/hr, does not correspond to the information shown in the soils report.
RESPONSE: The form will not allow 0.019 to be reflected this.
7. Lines 28 & 29 — This SCM is required to have an IWS.
RESPONSE: The form has been revised to reflect this.
8. Lines 31 and 40 & 41 — The use of grass sod and mulch in a bioretention cell are mutually exclusive.
RESPONSE: The form has been revised to reflect the use of sod.
9. Line 32 — Since this SCM is required to have an IWS, the media depth cannot be 24"
RESPONSE: The form has been revised to reflect this.
10. Line 37 — Please include this value.
RESPONSE: The form has been revised to reflect this.
1 1 . Line 43 — Please indicate the type of pretreatment that will be used for the SCM. NOTE: Providing no
pretreatment is strongly discouraged as it will increase the maintenance frequency needed for the SCM.
RESPONSE: Pretreatment is by provided in the swales leading to the SCM..
Thank you for the initial comments and please advise if any additional information is needed to complete the
review.
Sincerely,
a
6z`w
Brian Kemp
Team Leader