SW6230902_Response To Comments_20240103

4006 Barrett Drive,Suite 104
Bowman Raleigh,North Carolina,27609
TEL [phone]
Jurisdiction:NCDEQ
Date: 12/8/23
Subject: Stormwater Comments
Comment Response
1.Please ensure that the off-site portions of the drainage areas to the SCMs ✓ The offsite portion of the site accounts for 22,179 sf and the
are correctly accounted for at their full build-out potential(per 15A NCAC design has been adjusted to assume 100%BUA.Please see
02H.1003(3)(b)).Full build-out potential is determined by either having the the narrative and drainage area in the calculations package as
property owner and permittee enter into a legal agreement limiting the amount well as the updated supplement-EZ and stormwater
of BUA and drainage area being directed from the off-site area to the SCM or application.
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).
2. The USGS topographic map(relevant area attached)indicates that ✓ Updated the topo map in the calculations package to include
additional surface water may be present on the northwestern portion of the the project area.
site.Vegetated setbacks from surface waters are required if the water is shown
on either the most recent version of the soil survey map prepared by the
NRCS or the most recent version of the topographic maps prepared by USGS
per 15A NCAC 02H.1017(10).Please indicate the project area on the most
recent USGS map so that on site surface waters can be verified.
3. Consistency
a.The Application Section IV, 10 lists the on-site streets within the drainage ✓ The application has been updated to 24,984 sf for on-site
area of the SCM as 24,892 SF,but the Supplement-EZ lists the roadway BUA streets and the roadway BUA in the supplement form has
as 41,092 SF,please clarify the inconsistency. been updated to match.24,984 sf is the roadway/cul-de-sac
on the property.
b.Per Sheet C3.0 and the Supplement-EZ,the building BUA is 33,210 SF, ✓ Item 9(BUA on subdivided lots)in the supplement form has
but on the Application,the on-site Buildings/lots is listed as 49.410 SF.Please been updated to 49,410 sf and matches the impervious on-site
clarify. building/lots square footage in the application and sheet C3.0.
c.Per Sheet 6.8,the bottom of the forebay is 167.0',but the stage storage ✓ Updated the bottom elevation of the forebay in the wet pond
table provided in the calculations utilizes a bottom elevation of 167.6',please profile on sheet C6.9 to be 167.6.
revise package for consistency.
d.Per Sheet C6.8 and the calculations,the orifice diameter of the outlet is ✓ Updated the orifice diameter in the supplement form to be
1.3"diameter,but the Supplement-EZ lists the diameter as 1.56". 1.3".

4006 Barrett Drive,Suite 104
Bowman Raleigh,North Carolina,27609
TEL [phone]
4.Application
a. Section IV,6—Please include the on-site surface water area(located on the ✓ Updated this value in the application and highlighted this
northwestern portion of the project area).For streams and rivers,surface surface water area in sheet C2.0.
water area is the area between the banks.
b. Section IV,7&8—Please recalculate as needed per above comment. ✓ Recalculated sections 7 and 8.
NOTE:The project area does not include surface water areas.
5. Supplement-EZ
a.Cover,Lines 2 and 4—Please include the on-site surface water area and ✓ Updated these values to match the stormwater application.
revise the project area to be consistent with the above revisions to the
Application.
b. Cover,Line 7-8—Please indicate the width of the vegetated setback ✓ Updated these lines in the supplement form.Also called out
required from surface waters(30 ft per 15A NCAC 02H.1017(10)).The this 30ft vegetated setback in sheets C2.0,C3.0 and C4.0.
vegetated setback must remain vegetated per 15A NCAC 02H.1003 (5)(b).
c.Drainage Areas,Line 9—Please fill out as the new BUA that is on ✓ Updated line 9 to be the BUA on the subdivided lots.
subdivided lots.
d.Drainage Areas,Line 10—Please fill out as the new BUA that is not on ✓ Update line 10 to be the BUA that is not on the subdivided
subdivided lots. lots.
e.Wet Pond,Line 26—Per the stage storage table provided in the calculations ✓ Updated the supplement form to match the calculations.
the surface area of the main permanent pool is 4,370 SF.Please revise this or
the calculations for consistency.
f.Wet Pond,Line 53—Specify the species of turf that will be used on the dam ✓ Added the species of turf(Bermuda)to the supplement form
and embankment to confirm compliance with 15A NCAC 02H.1053 (11)(a). to match the species called out on the landscape notes.
6. Plans
a.Provide the sizing and class for the riprap apron at FES#200 on the plans to ✓ Added note to sheets C4.0 and C6.9 referencing the sheet that
ensure compliance with 15A NCAC 02H.1003 and 15A NCAC 02H.1050 has the sizing and class information for the rip-rap apron
(4) (C6.1).
b. On the profile of the wet pond detention system,the bottom of sediment ✓ Adjusted this elevation to be 167.1.
storage at the exit of the forebay is listed at 168.6'.This is above the listed
forebay top of sediment storage of 167.0'.