SW6220703_comments_2021028

site
October 27, 2022 solutions
o ut ons
Jim Farkas civil engineering I tand surveying
NCDEQ Stormwater Program
512 N. Salisbury Street
Raleigh, NC 27604 RECEIVED
RE: MAGNOLIA HILLS S/D ADDITIONAL COMMENTS 8
SW6220703 l
DFALR-Stormwater PrW= j
Jim;
We are re-submitting the portions of the Stormwater application and documents that
have been revised/created per the comments below.
r
f
Please correct the following: j
- General: i
}" The swale velocity calculations were not provided.The swa.e vel=ocities were
III
provided in the swuie design table of the Supplement-E2 r orris (as a separate l
sheet), but the calculations showing how the velocities were determined
(specifically which Manning's "n"values were used)was not provided. Please
provide these calculations so that the velocity values can be verified. Please
note that the "n"value should be based on the permanent design conditions,
not on the temporary matting.
■ The report has been updated to include the bare earth and final design
stages in the ditch caics.
,o Electronic files for all of the calculations were not provided. !
a The calcuiations have been uploaded along with the other revisions.
Vegetated Conveyance Design: I$
o Some of the ditches (1, 2, 3, 13, 19, 27,&37) have an actual velocity that is
larger than the Vallowable value shown for these ditches (for example, Ditch#1
has a Vallowable of 5.0 fps and a Vactual of 8.06 fps). Please revise as needed.
■ The ditch data has been updated and corrected.
�o Please ensure that the ditches that are discharging to wetland areas do so at a
non-erosive velocity(2.0 fps for wetlands).
Ditch#1 is the only ditch that has:a direct discharge into a wetland, l
have added a rip rap dissipater to slow the flow at the end of Ditch#1.
Vo The ditch detail on plan sheet C-6.0 indicates to "see plans"for the bottom
width of the ditches. I didn't see the ditch bottom widths shown in the plans. i
Please ensure that this information is specified in the plans.
■ The ditch detail has been modified to indicate all ditches have a 0.5'flat
bottom unless otherwise specified vn the plans. Ditch 1&31 have their
widths noted on the plans.
409 Chicago Drive, Suite 112, Fayettevitte, NC 28306
office l 910-426-6777 fax> 910-426-5777
On time,every time.; wwvvADsitesotutions.corri

Application:
o Section I'v,8 Sty=The%BUA value appears to he incorrect(885,648 sf of New
BUA J 5,044,684 sf of Project Area = 17.6% BUA not 17.8% BUA). Please revise
as needed.
■ % BUA corrected to 17.6%
Supplement-EZ Form:
o Drainage Area Page:
■ Lines 5&6--Please use the project area (115.81 ac/5,044,684 sf)
instead of the property area and please show this value in square feet,
instead of acres.
a Updated
i o Low-Density Page:
■ Line 5—Per the provided swale design table,the maximum velocity in
the ditches during the 10-year design storm is 8.06 fps (Ditch#1). Please
revise as needed.
• Updated,the value was 7.52 due to updating/revising the ditch
data table.
If you find the submittal lacking, please contact me at your earliest convenience.
Sincerely,
4D Site Solutions Inc.
Scott Brown, PE
[e-mail]
Enclosure
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