SW4231202_Response To Comments_20240311

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t ng nee>rnng, Inc.
—Since 1974—
I Engineers Surveyors Planners
March 8, 2024
Brianna Holland
512 N. Salisbury Street, Office 625Y
Raleigh,NC 27604
Re: The Townes at Bermuda Run Phase 1 (SW 4231202)
Response Letter
Comment:
1. As designed,this project does not meet Runoff Treatment(defined in 15A NCAC
02H .1002(43) and required per 15A NCAC 02H .1003(3)(a)). NOTE: 15ANCAC
02H .1003(3)(a) does also allow for a project to meet treatment requirements via Runoff
Volume Matching. In order for a project to meet Runoff Treatment,the net increase in
BUA must be captured and treated in one or more primary SCMs.
• If meeting Runoff Treatment,the use of another primary SCM will be required,
or the BUA can be directed to either proposed wet pond. Examples of primary
SCMs found within the manual that can be used as cartridges in the inlets
proposed include Bayfilters (Chapter D-4) and StormFilters (Chapter D-1)
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). As shown,the area currently shown as low-density does not meet the
requirements. Low-density drainage areas must be designed to maximize dispersed flow through
vegetated areas and minimize channelization of flow(15A NCAC 02H .1003 (2) (b). In order for
this area to meet low-density criteria,the requirements for curb outlet systems outlined in 15A
NCAC 02H .1003 (2) (d) must be met.
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).
Response: Project being proposed to be all High Density. For BUA not captured in a SCM Variance/Waiver
was approved per the attached waiver request letter.
Comment:
2. Please ensure that the off-site portions of the drainage areas to the SCMs are correctly
accounted for at their full build-out potential (per 15A NCAC 02H .1003(3)(b)). Full
build-out potential is determined by either having the property owner and permittee enter
4609 Dundas Drive
Greensboro,NC 27407
Phone [phone]
License#C-0168

vans
ngineering, Inc.
—Since 1974—
I Engineers Surveyors Planners
into a legal agreement limiting the amount of BUA and drainage area being directed from
the off-site area to the SCM or by assuming that the off-site area is 100% BUA, its full
build-out potential. It is recommended to bypass off-site drainage areas around proposed
SCMs as the permittee has no control over how off-site areas are developed (which is
why they are required to be accounted for at their full build-out potential). Indicate which
option is being pursued and revise the package as necessary. See additional information
on this item at the conclusion of this letter.
Response: Off-site drainage areas is being assumed 100%BUA
Comment:
3. There appears to be a discrepancy between the total BUA allocated to the lots as shown
in the Application(71198 SF+88392 SF= 159,590 SF=3.66 ac) and plans (2.02
ac+1.64 ac=3.66 ac), and the sum of the individual lot allocations as shown in the deed
restriction document(2,200 SF/lot * 74 lots= 162,800 SF=3.74 ac). Please revise as
needed for consistency. The SCMs should be designed for the maximum amount of
BUA that is allowed, so if the deed restrictions allow for 3.74 ac,the SCMs should be
sized accordingly, and the package should consistently reflect that value.
Response: BUA area per lot revised to reflect numbers shown on plans.
Comment:
4. Ensure the area of surface waters below the Normal High Water Line is excluded from
the project areas in the percent BUA calculations for the low density and high density
portions of the site per 15A NCAC 02H .1003 (1)(c).
Response: %BUA values revised per area blow the normal high water line.
Comment:
5. 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).
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).
4609 Dundas Drive
Greensboro,NC 27407
Phone [phone]
License#C-0168

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—Since 1974—
I Engineers Surveyors Planners
Response: Current form has been provided with resubmittal package.
Comment:
6.If resubmitting as a mixed density project,note the following changes are required:
a. Supplement-EZ, Cover, Line 5—Select high and low density so that the low-density
supplement pages will be generated and available for review.
b. Similarly, O&M Agreement will need to be revised to include the low-density O&M
maintenance requirements.
Response: No mixed density being proposed.
Comment:
7.Please make the following revisions to the Supplement-EZ
a. Drainage Areas Page,Line 12: This item is for BUA not on subdivided lots. The roof
values used in this section seem to correspond to the buildings/lots value provided in
the table Application Section IV, 10 for the on-site lots value. Please revise or clarify.
b. Wet Pond Page,Line 2: Please fill in.
c. Wet Pond Page,Line 32: These values could not be verified, as the stage storage
tables provided did not appear to exclude sediment storage (Wet Pond MDC 3).
d. Wet Pond Page,Line 35: Revise this item to reflect the volume stored between the
temporary pool and permanent pool per the Wet Pond Manual.
e. Wet Pond Page, Line 42—There do not appear to be berms and baffles provided in
these ponds to increase the length of the flow path from the inlet to the outlet.
Response:EZ form has been revised to reflect the comments above.
Comment:
8.Please make the following revisions to the plans
a. Provide a detail of the entirety of the wet ponds in cross section view per 15A NCAC
02H .1042(2)(h). Include dimensions, side slopes, and elevations with a benchmark
for clean-out.
i. Per Wet Pond MDC 3 there is a minimum depth of 6 inches within the forebay
(this depth must be maintained at the entrance and the exit). The sediment storage
note provided does not meet this requirement as it references the storage provided
in the forebay as 740 to 740.5,but the bottom of the forebay at the entrance is
shown to be 741. At the entrance,the top of sediment storage should be a
minimum of 741.5 to meet this MDC. Please show the cleanout benchmarks for
the forebay in the cross-section per 15A NCAC 02H .1042(2)(h).
b. Clearly show and label the recorded easements on the main set of plans (Section VI,
4609 Dundas Drive
Greensboro,NC 27407
Phone [phone]
License#C-0168

j vans
ngineering, Inc.
—Since 1974—
I Engineers Surveyors Planners
8n). 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. Maintenance accesses shall:
(a) have a minimum width of ten feet;
(b) not include lateral or incline slopes that exceed 3:1 (horizontal to
vertical); and
(c) extend to the nearest public right-of-way.
See 15A NCAC 02H .1050 (8) and(9)for additional information on maintenance
accesses and easements.
Response:Easements added to plans. Cross section detail of the entire pond added to pond detail sheets.
Comment:
9. Please revise the stage storage calculations as including the sediment storage in the
volume calculations overestimates the volume provided,per Wet Pond MDC 3.
a.Note,the average depth calculation provided and Wet Pond 1 Line 27 of the Wet
Pond Page of the Supplement-EZ are correct.
Response: Stage/Storage tables revised to separate permanent sediment storage volume from main pool volume.
Comment:
10. It is unclear what size storm is the design flow values used in the riprap calculations
derive from. Please provide additional information in these calculations so that
compliance with 15A NCAC 02H .1003 (5) and General MDC 4 can be confirmed.
a. Ensure outlet protection calculations and sizing specifications are shown for all
outlets, such as the road crossing at the northern portion of the site, and the outlet
associated with Pipe 74.
Response: Storm pipe chart and sizes added to plans. All rip-rap aprons below storm sewer
pipes are sized per the design flow on the pipe chart. Rip-rap aprons at the pond barrel outlet
are designed per the calculated flow through the barrel with the pond at full stage.
Comment:
11. Ensure the electronic repository is complete Plan Sheet C5.1 was not found within the
repository.
Response: C5.1 added to the repository
Comment:
12. 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.
Response: Requested documents provided.
4609 Dundas Drive
Greensboro,NC 27407
Phone [phone]
License#C-0168