SW6240803_Response To Comments_20240916

Please see my comments below in red. Thank you!
1. Original Comment 1.f.— "Please correct the following general design issues: The provided
calculations are insufficient(calculations are required per 15A NCAC 02H.1042(2)(f)).At a
minimum, calculations should be provided for the following:Minimum required treatment
volume for the drainage area to each SCM.Actual provided treatment volume (design volume)
for each SCM. Riprap sizing/design (in accordance with General MDC 4& 15A NCAC 02H
.1003(5)). Any other calculations needed to show where design values shown in the Supplement-
EZ Form came from."These items were not provided.
a. RESPONSE:This is an older comment concerning the individual pervious paved areas.
These areas were removed in the last design when we changed over to a stormwater
wetland. Outlet design is included in the calculation packet and a drainage area map
has also been included.
2. Original Comment 1.g.— "Please correct the following general design issues: There appear to be
issues with the provided drainage area map. Please revise as needed:Please clarify what causes
the drainage areas to SCMs 2&4 to stop at the entrance/exit driveways to the site. The provided
grading plans appear to show that runoff from the rest of the entrance/exits and some of the
roadway would drain on-site. NOTE:Any off-site runoff not bypassed around an SCM must be
accounted for at its full build-out potential(see note following the comments for more
information on this)."This item was not addressed.A revised drainage area map (required per
15A NCAC 02H .1042(2)(g)(iv)) was not provided.
a. RESPONSE:A revised drainage area map has been included as well as an impervious
area map in the plan set.
3. Original Comment 4— "Please correct the following issues with the Supplement-EZ Form:..."A
revised Supplement-EZ Form was not provided.The provided form is an outdated version of the
form and is not acceptable.Thie Supplement-EZ Form can be found at the following location:
https://www.deq.nc.gov/about/divisions/energy-mineral-and-land-
resources/stormwater/stormwater-program/stormwater-design-manual
a. RESPONSE:An updated form has been filled out and included in our calculations packet.
4. Prior Comment 6— "Provide PDFs of all revisions..."Electronic files were not provided.
a. RESPONSE: See attached thumbdrive.
- General MDC 1&Stormwater Wetland MDC 1/3—Per the provided stage-storage table,the
design volume of the SCM (storage volume provided between the permanent pool surface
(127.5') and the invert of the lowest bypass device (orifice @ elevation 128.5')) is approximately
10,000 cf whereas the minimum required treatment volume (as indicated in the provided
outdated version of the supplemental form) is 13,114 cf. NOTE: Per the provided stage-storage
table,the storage volume provided up to 15" above the permanent pool surface elevation (the
max ponding depth above the permanent pool surface allowable per the MDC) is still less than
the provided minimum required treatment volume (at approximately 12,900 cf).
o RESPONSEStorage volume is actually 13,114 based on autocad model.

- General MDC 8&9—It is noted that the SCM maintenance &access easement is provided,
however,the entire footprint of the SCM system must be included in the access and
maintenance easement, plus an additional ten or more feet around the SCM to provide enough
room to complete maintenance tasks.This SCM system includes the side slopes,forebay, riser
structure, SCM device, and basin outlet, dam embankment, outlet, and emergency spillway.
o RESPONSE:Access easement has been adjusted to include full area.
- Stormwater Wetland MDCs 6-9—As designed, the zone sizing/makeup for the stormwater
wetland does not meet the MDCs. Per the provided information,the planting zones would be as
shown below.The deep pools/forebay areas corresponds to the blue zone (everything below
elevation 126.75', more than 9" below the permanent pool surface),the shallow water zone
corresponds to the green zone (everything between elevation 126.75' & 127.5', 0"-9" below the
permanent pool surface), and the temporary inundation zone corresponds to the yellow zone
(everything between elevation 127.5' &the invert of the lowest bypass device (orifice @ 128.5'),
0"to a max of 15" above the permanent pool). NOTE:The zones shown below do not
correspond to the planting zones shown in the plans. NOTE:As shown in the submittal items,
the sum of the area of the zones does not equal the total surface area of the SCM at the
temporary ponding elevation (the plans show the cross-sectional area of the shallow water zone
as 4,283 sf,temporary inundation zone as 8,079 sf, non-forebay deep pool as 601 sf, and
forebay as 1,120 sf(Sum = 14,083 sf which is larger than what is shown in the stage-storage
table (10,500 sf @ elevation 128.5')). Please also include the spot elevations for the bottom of
the forebay deep pool(s) near the forebay entrance, and the bottom of the forebay deep pool(s)
near the forebay exit as these were not provided (and required to ensure that the forebay
bottom near the entrance is deeper than the forebay bottom near the exit, see Figure 5 in Part
C-3 of the Manual).
o RESPONSE: Please see revised plan set.