SW6231107_Response To Comments_20240314

FNGINFERS
PFANNF RS
SURVEYORS
March 14, 2024 MOORMAN,KIZERaREITZEL,INC.
115 Broad)ootAvenue
Ms. Brianna Holland P 0 Box 53774
Stormwater Engineer Fayetteville.North Carolina28305
DEMLR Post-Construction Stormwater Program [phone]
Fax [phone]
[e-mail]
www.mkrinc.com
[phone]
For FedEx/UPS:
512 N. Salisbury Street, Office 625Y
Raleigh, NC 27604
For USPS:
1612 Mail Service Center
Raleigh, NC 27699-1612
Re: Stormwater Permit No. SW6231107
High Density Subdivision—2 Wet Ponds
Kingston Village, Hoke County
Dear Brianna:
We have addressed your comments per your 2/13/2024 letter and updated the drawing set to reflect
these changes. Below you will find your comments listed along with our responses in blue. Also included
with this letter are additional calculation tables, NCDEQ forms, and the revised drawing set. Please don't
hesitate to call or email with any additional questions or concerns.
1. The provided O&M Form is 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). Please
note that a complete O&M Agreement Form will have 2 or more pages and uses macros to
generate the relevant sheets based on the information entered into the cover page. 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).This item is required per
General MDC 11-12.
A revised O&M form with macro generated pages is included with this submittal.
2. Ensure that General MDC 8 and 9 are met. Wet Pond B does not appear to have an
easement/maintenance access that includes the entire SCM system.
Wet Pond B has a 10' access maintenance aisle around its entire perimeter.This aisle will be
grassed and have a 2%cross slope draining toward the pond. Access to the pond from the cul-
de-sac is relatively flat except for the final approach to the pond perimeter aisle, where it has
maximum 8H:1V slope for a short distance.
The pond, including the 10' wide perimeter access, is located entirely inside a stormwater
Responses to NCDEQ Comments,Page 1 of 5

control access and maintenance easement.The access from the cul-de-sac, the pond inflow pipe
from the cul-de-sac, and pond outflow pipe are located inside 20' wide drainage easements.
Refer to drawing sheet 4 (included with this submittal) of the overall plan set where these
easements are shown and labeled.
3. Wet Ponds must maintain a permanent pool,therefore, a wet pond that infiltrates would not
meet Wet Pond MDC 7.
Each pond has been designed as a wet pond. Permanent pool elevations are 245' and 248.5' for
Ponds A and B respectively. We have added a liner for Wet Pond B because of its elevation vs.
the seasonal high water table. Refer to drawing sheet 23 of the overall plan set for additional
detail.
4. Clearly delineate the drainage area that will be treated by each SCM on the main set of plans
as required per the Application Section VI,80.
Drawing sheet 4B (included with this submittal) of the overall plan set shows the drainage areas.
5. Application,Section IV, 10, Drainage Area 1:The 320,350 SF impervious area in the On-site
Buildings/Lots category does not appear to correspond to the provided lot deed restrictions of
5,000 SF/lot.
This figure has been recalculated to include updated information concerning the community
parcel. It now sums to 320,800 sf.This considers 64 lots at 5,000 sf/lot impervious+800 sf
building on the community parcel, 64 x 5,000 sf+800sf= 320,800 sf.The remaining 11 lots drain
to Pond B.
Included with this submittal are revised pages 3 and 4 from the application. Items IV.8 and IV.10
have been updated.
6. The Supplement-EZ was not provided and could not be reviewed for correctness at this time.
The Supplemental-EZ is included with this submittal.
7. Design Requirements for High Density Projects
a. As designed,the project does not appear to meet Runoff Treatment or RunoffVolume Match. In
order for a project to meet Runoff Treatment,the net increase in BUA must be captured and
treated within one or more primary SCMs and in order for a project to meet Runoff Volume
Match,the annual runoff volume before development cannot increase by more than 10%(NOTE:
This requirement refers to annual runoff volume, not a flow rate from a design storm). Please
refer to 15A NCAC 02H .1002(43)&(44) and .1003(3)(a). Please ensure that all of the new BUA
(or an area of BUA equal to the net increase in BUA) is being treated in one or more primary
SCMs. Please revise as needed.
b. Per General MDC 1,the design volume of SCMs shall take into account the runoff at build out
from all surfaces draining to the system. Drainage from off-site areas may be bypassed.The
combined design volume of all SCMs on the project shall be sufficient to handle the required
Responses to NCDEQ Comments,Page 2 of 5

storm depth.
See Part B of the Manual for information on how to calculate the volume of stormwater
runoff.
The ponds are sized for the net increase in BUA using the SA/DA method. It should be noted that
Pond A is sized conservatively as it considers flow from the small portion of impervious near the
entrance which cannot actually be conveyed to the pond due to elevation constraints. Pond sizing
calculations are included with this submittal. Each pond is designed to handle the one-inch design
storm above the permanent pool and discharge that storm between the required two and five
days.
8. In order to verify storage requirements, please provide the Stage Storage information in
tabular format,or label the points.
These tables are included with this submittal.
9. The forebay must be excluded from sizing calculations, per Wet Pond MDC 1. Please clarify
the provided calculations to show separate forebay and main pool calculations.
a. Per Wet Pond MDC 5(a) Forebay volume shall be 15 to 20 percent of the volume in the main
pool.
The sizing information and stage-storage tables are included with this submittal.
10. Per Wet Pond MDC 1,The main pool of the wet pond shall be sized using either:The Hydraulic
Retention Time(HRT) Method; or The SA/DA and Average Depth Method. Please provide
clarifying calculations demonstrating the method used to size the wet ponds.
The ponds were sized using the SA/DA method.The sizing information is included with this
submittal.
11. Please provide average depth calculations. Per Wet Pond MDC 2,The average depth of the main
pool shall be three to eight feet below the permanent pool elevation.The applicant shall have
the option of excluding the submerged portion of the vegetated shelf from the calculation of
average depth.
At permanent pool elevation,the Pond A main pool will have volume of 106,290 cf and surface
area of 25,834 sf.This is from elevation 240'which accommodates the required 6 inches of
sediment storage below. Dividing the volume by surface area yields an average depth of 4.11'.
At permanent pool elevation, the Pond B main pool will have volume of 15,546 cf and surface area
of 4,702 sf.This is from elevation 240.5' which accommodates the required 6 inches of sediment
storage below. Dividing the volume by surface area yields an average depth of 3.31.
12. Per Wet Pond MDC(3),The inlet(s)and outlet shall be located in a manner that avoids short
circuiting. Wet Pond 1 has an inlet that bypasses the forebay, and therefore creates short
Responses to NCDEQ Comments, Page 3 of 5

circuiting.
The stormpipe that bypasses the forebay carries runoff collected at inlets ST-10 and ST-20. As the
road slopes downward toward the entrance,these inlets are placed to maximize capture and
conveyance of runoff to the pond.This placement, however, places the stormpipe too low to
connect to inlet ST-50 and therefore the forebay. It should be noted that inlets ST-10 and ST-20
collect runoff from a combined 0.75 acres, 3.2%of the 23.49 total acres of drainage for which
Pond A is sized and therefore should not materially affect the pond's overall functionality. We can
construct a small forebay around that pipe inlet upon your direction.
13. Per Wet Pond MDC 5(b),the forebay entrance shall be deeper than the forebay exit, please
revise the plans.
The plans have been changed to reflect this. Refer to sheets 4, 22, and 23 (included with this
submittal) of the overall plan set.
14. Provide separate tables for the volume stored beneath the permanent pool, and the volume
stored between the permanent pool and temporary pool so that sizing calculations can be
verified.
a. Ensure that the sediment storage is excluded from these calculations per Wet Pond
MDC 3.
These pond stage-storage tables are provided with this submittal.The ponds have been sized
per the SA/DA method from elevation at top of sediment storage.
b. Ensure that the design volume(the volume between the temporary pool elevation and
permanent pool elevation)shall draw down to the permanent pool level between two
and five days, per Wet Pond MDC 7.
The drawdown from each pond was modeled using AutoCAD Storm and Sanitary Analysis
software. Included with this submittal are the tabular and graphical output for each pond
drawdown. This information shows that the design storm will discharge from each pond
within the required time frame of two to five days.
15. Per MDC 11(a)The dam structure, including front and back embankment slopes,of the pond
shall be vegetated with non-clumping turf grass; trees and woody shrubs shall not be allowed.
Per MDC 11(b)The vegetated shelf shall be planted with a minimum of three diverse species of
herbaceous, native vegetation at a minimum density of 50 plants per 200 square feet of shelf
area. Revise the planting schedule to remove plants,such as shrubs,that do not meet these
requirements.Specify the specific plants(species,size, and number)to be used on the vegetated
shelf and dam/embankments.
The planting specifications on the pond detail sheets (sheets 22 & 23) of the overall plan set have
been updated per these requirements and are included with this submittal.
Responses to NCDEQ Comments,Page 4 of 5

16. Per General MDC 4,the inlets SCMs shall be designed to protect the SCM from erosion resulting
from stormwater discharges.The outlets of SCMs shall be designed so that they do not cause
erosion immediately downslope of the discharge point during the peak flow from the 10-year
storm event as shown by engineering calculations. Provide these calculations and ensure that
the protection shown on the plans has consistent sizing with the calculations.
Sheets 12A and 12B of the overall plan set are included with this submittal. These plan sheets
show rip rap and erosion control placement as well as flowrate, velocity, and rip rap sizing
information throughout the project.
Please don't hesitate to call or email with any additional questions or concerns.
Sincerely,
David Despeaux, PE
Moorman, Kizer& Reitzel, Inc.
115 Broadfoot Avenue
Fayetteville,NC 28305
910-484-5191
[e-mail]
Responses to NCDEQ Comments,Page 5 of 5

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Pond A Stage-Storage Tables
Forebay
elev area volume !volume
(ft) sf cf (cf)
240 2917
244.5 4566 16,836.75 16,836.75
245 4971 2,384.25 19,221.00
Main pond
elev area volume 1 volume
(ft) (sf) cf (cf)
240 17,435.00
244.5 24,241.00 93,771.00 93,771.00
245 25,834.00 12,518.75 106,289.75
Total pond
elev area volume 2 volume
(ft) (sf) cf (cf)
240 20,352.00
244.5 28,807.00 110,607.75 110,607.75
245 30,805.00 14,903.00 125,510.75
245.5 33,356.00 16,040.25 141,551.00
249 40,988.00 130,102.00 271,653.00
249.2 46,410.00 8,739.80 280,392.80
Note that the forebay volume of 19,221 cf is 18.1%of
the main pond volume of 106,290 cf.
An additional 6" depth is provided for sediment
storage.
Permanent pool is at elevation 245'.

Pond B Stage-Storage Tables
Forebay
elev area volume 2 volume
(ft) (sf) (cf) (cf)
242.5 123
248 696 2,252.25 2,252.25
248.5 850 386.50 2,638.75
Main pond
elev area volume 2 volume
(ft) JAL_ cf (cf)
240.5 44
242.5 659.34 703.34 703.34
248 3,951.29 12,679.23 13,382.57
248.5 4,701.53 2,163.21 15,545.78
Total pond
elev area volume 1 volume
(ft) (sf) (cf) cf
240.5 44
242.5 782.34 826.34 826.34
248 4,647.29 14,931.48 15,757.82
248.5 5,551.53 2,549.71 18,307.53
249 6,751.65 3,075.80 21,383.32
252 9,971.11 25,084.14 46,467.46
252.2 14,146.68 2,411.78 48,879.24
Note that the forebay volume of 2,639 cf is 17.0%
of the main pond volume of 15,546 cf.
An additional 6" depth is provided for sediment
storage.
Permanent pool is at elevation 248.5'.

Pond A
Drawdown Pond water surface elevation begins at water surface elevation of 246.57'.
This is the water surface elevation reached by adding the 1" design storm to
"` Mal pond above the permanent pool elevation.As shown in the table,the
Outflow outflow rate drops to zero at hour 114.This fits within the allowable 2 to 5
Time from Pond day range to return to permanent pool level.
(hrs) (cfs) Pond A
0.02 0.51 Drawdown Outflow
1.00 0.50 0.60
2.00 0.49
3.00 0.48 0.50
4.00 0.47
0.40
5.00 0.46
6.00 0.45 6 0.30
7.00 0.44
8.00 0.43 0.20 Outflow reaches zero and
9.00 0.42 pond reaches permanent pool
0.10 10.00 0.41 elevation at hour 114.
11.00 0.40 0.00
12.00 0.39 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00
13.00 0.39 hours
14.00 _ 0.38
15.00 0.37
16.00 0.36 Total Total Total
17.00 0.35 Outflow Outflow Outflow
18.00 0,34
_ Time from Pond Time from Pond Time from Pond
_ 19.00 0.33 (hrs) (cfs) ( s) (cfs _ (hrs) (cfs)
20.00 0.32 46.00 0.07 72.00 I 0.02 99.00 0.01
21.00 0.31 47.00 0.07 73.00 0.02 100.00 0.01
22.00 0.30 48.00 0.06 74.00 0.02 101.00 0.01
23 00 0 29 49.00 0.06 75.00 0.02 102.00 0.01
24.00 0.28 50.00 0.06 76.00 0.02 103.00 0.01
25.00 0.27 51.00 0.05 1 77.00 _ 0.02 104.00 0.01
26.00 0.26 52.00 0.05 l 78.00 0.02 105.00 0.01
-
27.00 0.25 53.00 0.05 i [ 79.00 0.02 106.00 0.01
28.00 0.24 54.00 0.05 80.00 0.01 107.00 i 0.01
29.00 0.23 55.00 0.04 81.00 0.01 108.00 0.01
30.00 0.22 56.00 0.04 82.00 0.01 109.00 0.01
31.00 0.21 57.00 0.04 _ 83.00 0.01 110.00 0.01
32.00 0.20 58.00 0.04 84.00 0.01 111.00 0.01
33.00 0.19 _ 59.00 0.04 85.00 0.01 112.00 0.01
34.00 0.18 60.00 - 0.03 86.00 0.01 113.00 0.01
35.00 0.16 r 61.00 _ 0.03 87.00 0.01 114.00 0.00
36.00 0.15 62.00 0.03 88.00 0.01 115.00 0.00 -
37.00 0.14 63.00 0.03 89.00 0.01 116.00 0.00
-
38.00 0.13 64•00 0.03 90.00 0.01 117.00 0.00
39.00 0.12 _ 65.00 0.03 91.00 0.01 118.00 0.00
40.00 0.11 _ 66.00 0.03 92.00 0.01 119.00 0.00 -
41.00 0.10 67.00 0.02 93.00 0.01 120.00 ' 0.00
42.00 0,09 L 68.00 0.02 95.00 0.01 121.00 0.00
43.00 0.09 69.00 0.02 96.00 1 0.01 ,
44.00 0.08 70.00 0.02 97.00 0.01 '
45.00 0.08 Ir 71.00 L 0.02 98.00 1 0.01

Pond B
Drawdown Pond water surface elevation begins at water surface elevation of 249.76'.
This is the water surface elevation reached by adding the 1"design storm to
Total the pond above the permanent pool elevation.As shown in the table,the
Outflow outflow rate drops to zero at hour 56.This fits within the allowable 2 to 5
Time from Pond day range to return to permanent pool level.
(hrs) (cfs) Pond B
0.02 0.51 Drawdown Outflow
1.00 0.28 0.60
2.00 0.18
3.00 0.13 0.50
4.00 0.09 0.40
5.00 0.07
6.00 0.06 0.30
7.00 0.05
8.00 0.05 0.20 Outflow reaches zero and
9.00 0.05 pond reaches permanent pool
0.10 10.00 0.05 elevation at hour 56.
11.00 0.05 0.00
12.00 0.05 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00
13.00 0.04 hours
14.00 0.04
15.00 0.04
16.00 0.04 Total Total Total
17.00 0.04 Outflow Outflow Outflow
18.00 0.04 Time from Pond Time from Pond Time from Pond
19.00 0.04 (hrs) (cfs) (hrs) (cfs) (hrs) (cfs)
20.00 0.04 46.00 0.01 72.00 0.00 99.00 0.00
21.00 0.04 47.00 0.01 73.00 0.00 100.00 0.00
22.00 0.04 48.00 0.01 74.00 0.00 101.00 0.00
23.00 0.04 49.00 0.01 _ 75.00 0.00 102.00 0.00
24.00 0.03 50.00 0.01 1 _ 76.00 0.00 103.00 0.00
25.00 0.03 51.00 0.01 77.00 0.00 104.00 0.00
26.00 0.03 52.00 0.01 78.00 0.00 105.00 0.00
27.00 0.03 53.00 0.01 79.00 0.00 106.00 0.00
-
28.00 0.03 54.00 0.01 - 80.00 0.00 107.00 0.00
29.00 0.03 55.00 0.01 - 81.00 0.00 108.00 0.00
30.00 0.03 56.00 0.00 _ 82.00 0.00 109.00 0.00
57.00 0.00 _ 83.00 0.00 110.00 0.00
31.00 0.03
32.00 0.03 58.00 0.00 - 84.00 0.00 111.00 0.00
33.00 0.03 59.00 0.00 _ 85.00 0.00 112.00 0.00
34.00 0.02 60.00 0.00 _ 86.00 0.00 113.00 0.00
35.00 0.02 61.00 0.00 _ 87.00 0.00 114.00 0.00
36.00 0.02 62.00 0.00 -188.00 0.00 115.00 0.00
37.00 0.02 63.00 0.00 - 89.00 0.00 116.00 0.00
38.00 0.02 64.00 0.00 _ 90.00 0.00 117.00 0.00
65.00 0.00 91.00 0.00 118.00 0.00
39.00 0,02
66.00 0.00 92.00 0.00 119.00 0.00
40.00 0.02
67.00 0.00 93.00 0.00 120.00 0.00
41.00 0.02
42.00 0.02 68.00 0.00 - _ 95.00 0.00 121.00 0.00
43.00 0.02 69.00 0.00 - 96.00 0.00
44.00 0.01 70.00 0.00 _ 97.00 0.00
45.00 0.01 71.00 0.00 L 98.00 0.00