SW4220301_Response To Comments_20221214

FEI
CIVIL ENGINEERS AND LAND SURVEYORS
Resubmittal December 14, 2022
Reference SW4220301, Woodhaven Subdivision
Please correct the following:
Prior Comment 2b — The provided specification pages for the Curlex I & II erosion control
blankets indicate that they are not permanent (Curlex I has a functional longevity of no more
than 15 months and Curlex 11 has a functional longevity of no more than 30 months). The swales
must remain stable in perpetuity. Please revise.
FEI Response: Swale calculations have been updated to reflect a temporary state (installation of
the matting prior to the establishment of permanent ground cover) and then a permanent state
with the establishment ground cover (grass). Swales in question were modified such that the
maximum velocity allowed in the permanent grass state remained under 5 ft/s. Shear stresses and
velocities for the other materials specified met the manufacturers specifications.
Prior Comment 2c — Please provide the sizing calculations for the energy dissipaters
downstream of the stormwater outlets (FES 100, EW 200, FES 300, & FES 400). This item is
required per 15A NCAC 02H .1003(5).
FEI Response: Energy dissipator calculations are shown on sheet 1 using the NYDOT method for
velocity dissipation.
The provided calculations indicate that the side slopes of the vegetated conveyances are 3:1
(left side) and 2:1 (right side). Per 15A NCAC 02H .1003(2)(c)(i) the side slopes of the vegetated
conveyances must be 3:1 or flatter (or you will need to provide a site specific soil investigation
to demonstrate that the soils will remain stable). Please revise as needed.
FEI Response: All swales were modified to have a 3:1 slope on both sides of the channel. Velocity
calculations were repeated following this modification.
• Supplement-EZ Form:
o Drainage Area Page:
■ Line 18 — Per the calculations, the %BUA should be shown as 21% (152,460 sf /
737,950 sf = 20.7% which rounds up to 21% (since the form only shows whole
numbered percents)).
FEI Response: Line 18 was corrected.
Low -Density Page:
■ Line 4 — See earlier comment, if multiple side slopes will be used for the
vegetated conveyances, please elaborate in the additional information section
(revise if needed).
!!:rAFEI
Civil Engineers and Land Surveyors

FEI Response: Side slopes were updated to 3:1 for all ditches. Velocities were also revised
based on the updated side slopes.
■ Line 5 —The calculations indicate a maximum velocity of 10.8 fps (swale 8).
FEI Response: As mentioned above, ditches were modified. The new maximum velocity based on
the modifications was 9.32 ft/s and line 5 was updated to reflect this.
Please provide the following:
• 1x hard copy & 1x electronic copy of the revised pages of the calculations.
• 1x hard copy & 1x electronic copy of the revised pages of the Supplement-EZ Form.
• 2x hard copies of the revised plan sheets (as needed).
• 1x hard copy (2x hard copies for plan sheets) & 1x electronic copy of anything else needed to
address these comments.
Hard copies should be mailed to me at the following address:
For Fed Ex/UPS:
Jim Farkas
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
For USPS:
Jim Farkas
1612 Mail Service Center
Raleigh, NC 27699-1612
Hand Delivery:
Please reach out to me prior to hand delivering a submission to make sure that I (or someone
else in my group) will be able to receive the submission. Do not leave the package in the foyer
with the security guard.
NOTE: Hard copies should not be sent to a Regional Office. Doing so will delay the review
process and the submission package may be lost while being sent from the Regional Office to
me in the Central Office.
!!:rAFEI
Civil Engineers and Land Surveyors

Electronic copies should be uploaded at the following location:
https://edocs.deg.nc.gov/Forms/SW-Supplemental-Upload
Feel free to let us know if there are any other changes/modifications.
!!99' F E I
Civil Engineers and Land Surveyors