SW1191201_Response To Comments_20210818

TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
Project: NCNG Morganton Regional RRC Phase II Date: 08/11/2021
Case #: SW1191201
Contact: Frank Slinsky, PE
Phone: [phone]
Email: [e-mail]
Comments from NCDEQ review has been addressed below. Our responses are in
Construction Document Submittal First Submittal Comments — 07/19/2021
NCDEQ REVIEW COMMENTS
Jim Farkas (919-707-3646, Jim. FarkasOncdenr.gov)
Since this Application is a modification of previously issued permit, please provide an
original, signed Designer's Certifiaction (Section I I,1 b). The Designers Certification was
included as part of the originally issued permit.
Response: An original, signed Designer's Certification has been provided. Please note this
project is still under construction and a new certification will be issued once construction is
complete.
2. Please update the stormwater treatment summary (section IV, 1) to mention the second
wet pond as it currently only mention a single wet pond.
Response: The stormwater treatment summary has been updated to mention the second
wet pond.
3. Since there is more BUA being added to this project as a result of the major modification,
the percent imperviousness of the site should increase from what was shown in the
original application (46.7%). Please ensure that the percent impervious area ( Section IV,
8) is calculated correctly for the revised BUA amount).
Response: The percent BUA has been calculated to be 49% and has been updated on the
application, calculations, and plan sheets.
4. The Major Modification Application included in the calculation booklet does not include
the second wet pond drainage area information (Section IV, 9 & 10). This information is
however included in the loose hard copies of the Major Modification Application that
were provided. If you are providing a revised version of the calculation booklet as part of
the resubmittal, please update this item, otherwise, I can just remove this item from the
calculation booklet (There are also some other mismatches between the Major
Modification Application in the calculation booklet and the loose copies of the Application
so these inconsistencies should also be corrected if applicable).
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Response: The calculation booklet has been updated to reflect the additional wet pond
information and to match the included loose hard copies.
5. Please provide original signatures on the Supplement-EZ Form and O&M Agreement
Form (Section V1,3).
Response: Original signatures have now been provided on the Supplement- EZ Form and
O&M Agreement Form.
6. The Application is not signed by the original signing official, Rodney Newton (Section
111,1a & Section X). If you would like to change the Applicant from Rodney Newton to
Kenneth Cook Jr., you will need to complete the Permit Information Update Form
(https:Hdeq.nc.gov/about/divisions/energy-mineral-and-land-
resources/stormwater/stormwater-program/post-construction). If Kenneth Cook Jr. has
delegated signature authority for Rodney Newton, you will need to provided official
documentation of that.
Response: The application has been signed by the original signing official, Rodney
Newton.
7. There are some noted discrepancies between the information from the original
application and this modification. For example, the original application stated that the
pre -development on -site BUA is 5.41 ac. while the major modification indicates that the
pre -development on -site BUA is 6.36 ac. (This example is demonstrative of the nature of
the inconsistencies, not an exhaustive list). Please ensure that all of the information
presented in the Major Modification is consistent with the information from the initial
Application as applicable.
Response: All inconsistencies have been resolved to reflect the original application as well
as the major modification application. Additional existing impervious was added for
pre/post analysis of drainage area B. This existing impervious is outside of the "project
area" so has been removed from BUA breakdowns.
8. The drainage area information for wet pond 1 shown in the Application does not match
the drainage area information shown in the Supplement-EZ Form, nor the drainage area
information shown in the plans. For example, the Application indicates that this drainage
area contains 570,010 sf of BUA, the Supplement-EZ Form indicates 593,666 sf of BUA,
and the plans indicate 563,666 sf (12.94 ac.). Please ensure that the drainage area
information is consistent throughout the submission. If the drainage area information for
wet pond 1 has changed from what was originally permitted, you will need to provide
updated design calculations for wet pond 1.
Response: The drainage area information is now consistent throught the submission.
There have been no changes to wet pond 1.
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9. The drainage area information for wet pond 2 shown in the Application does not match
the drainage area information shown in the Supplement-EZ Form. For example, the
Application indicates that this drainage area contains 149,945 sf of BUA and the
Supplement-EZ Form indicates 163,786 sf of BUA (The breakdown of the proposed
BUA also does not match). Please ensure that the drainage area information is consistent
throughout the submission.
Response: The drainage area information for wet pond 2 has been updated and is
consistent throught the submission.
10. The volume of the main permanent pool of wet pond 2 appears to be calculated
incorrectly. The volume of the main pool should not include any portion of the sediment
storage zone (Plan sheet C8.17 indicates that the sediment storage elevation is at
1206.00, the Supplement-EZ Form indicates this elevation to be at 1207.00, and the
calculations indicate this elevation to be at 1205.00). Please ensure that this volume is
calculated correctly, and revise the submission as needed for consistency.
Response: The volume of the main permanent pool of wet pond 2 has been calculated
correctly. Revisions have been made to ensure the submission is consistent.
11. Using the information from plans and the calculations, the average depth of the main
pool of wet pond 2 is less than the required 3 foot minimum (Wet Pond MDC 2). The
surface area, 5,502 sf was taken from the stage -storage table and the volume of the main
pool was recalculated as approximately 14,860 cf. based on the sediment storage
elevation from the plans. Please revise as needed.
Response: Wet pond 2 has been revised and now has an average depth of 3.25 feet
meeting the 3 foot minimum depth.
12. There is an insufficient amount of sediment storage depth provided in the forebay of wet
pond 2 (Wet Pond MDC 3). Plan sheet C8.17 indicates that the excavated bottom of the
forebay near the exit is at elevation 1206.00 and that the top of the sediment storage zone
is at elevation 1206.25. This results in a sediment storage depth of only 3 inches whereas
6 inches are required. Please revise.
Response: There is now a sufficient amount of sediment storage depth provided in the
forebay of wet pond 2. The plans and calculations have been updated to reflect the
provided 6 inches of sediment storage.
13. The elevations provided in the stage -storage table in the calculations for the temporary
ponding portion of the wet pond appear to be incorrect (These elevations are above
2,000.0 ft whereas the site is at about elevation 1,200.0 ft).
Response: The elevations provided in the stage -storage table in the calculation for the
temporary ponding portion of the wet pond is updated to reflect the on -site elevations.
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14. The drawdown orifice for wet pond 2 is shown on plan sheet C8.17 as having a 3.5 in.
diameter. This results in a drawdown time of less than 2 days for the design volume,
which is not acceptable (Wet Pond MDC 7). Please revise. The outlet configuration is
also unusual in that there are drawdown orifices located both above and below the
permanent pool elevation (both endcaps on the tee are shown to have a drawdown
orifice). Please ensure that this is accounted for correctly in the drawdown calculations.
Response: The drawdown orifice for wet pond 2 has been updated with an orifice
diameter of 1.5 inches located below the permanent pool elevation.
15. The following discrepancies were noted between the plans/calculations and the design
of wet pond 2 as shown in the Supplement-EZ Form (Wet Pond Page). Please revise as
needed:
a) Line 20 —the excavated bottom elevation of the main pool (1206.0 ft) is
shown as 1205.0 ft on plan sheet C8.17.
Response: The excavated bottom elevation has been updated to match the plans and
calculations.
b) Line 21- The top elevation of the sediment storage zone of the main pool
(1207.0 ft) is shown as 1206.0 ft on plan sheet C8.17.
Response: The top elevation of the sediment storage zone of the main pool has been
updated to match the plans and calculations
c) Line 25- The temporary pool elevation (1206.25 ft) is lower than the
permanent pool elevation. This item should be the water surface elevation
of the design volume (slightly over 1212.0 ft).
Response: The temporary pool elevation has been updated for the new elevation of
1212.25 ft. as shown in the plans and calculations.
d) Line 27 — As noted earlier, the volume of the main pool (19,358 cf) should
be closer to 14,860 cf (based on the sediment storage elevation (1206.0
ft) from theplans and stage -storage table from the calculations).
Response: The volume of the main pool has been calculated and updated accordingly.
e) Line 28 — As noted earlier, the average depth (3.52 ft) would be less than
3.0 ft if the revised main pool volume is used in "Equation 2" to calculate
the average depth of the main pool.
Response: The average depth has been calculated and updated to 3.25 ft.
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f) the volume of the forebay (2,968 cf) should be closer to 2,814 cf (based
on the sediment storage elevation (1206.25 ft) from the plans and stage -
storage table from the calculations).
Response: The volume of the forebay has been calculated and updated accordingly.
g) Line 34 — The cleanout depth (54 in) does not match the cleanout depth
from plan sheet C8.17 (51 in). The cleanout depth is the distance from the
permanent pool surface elevation (1210.5 ft) to the top elevation of the
sediment storage zone (1206.25 ft). 1210.5 ft — 1206.25 ft = 51 in.
Response: The clean out depth now has been updated to reflect the depth shown on
the plan sheets.
h) Line 37 —The orifice diameter (1.5 in) is shown as 3.5 in on plan sheet
C8.17.
Response: The orifice diameter has been updated to match the calculations and plan
sheets.
i) Line 40 — As noted earlier, the temporary pool drawdown time (3.6 days)
is calculated as less than 2.0 days based on the drawdown orifice
configuration shown on plan sheet C8.17.
Response: The orifice configuration has been updated on the plans to provide the
calculated temporary pool drawdown time of 3.6 days.
j) Line 44 — The depth of the forebay at the exit (51 in) is shown as 54 in. on
plan sheet C8.17 (The elevation of the forebay is shown at elevation
1206.0 ft and the permanent pool is shown at elevation 1210.5 ft).
Response: The depth of the forebay has been updated to match the depth shown on
the plan sheets.
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16. When uploading the electronic files, please ensure that each different type of file is
uploaded under its appropriate file type (For example, every file that was electronically
submitted for this submission was uploaded under the "Stormwater Report" file type
which led to most of the uploaded files being incorrectly named/classified in our
repository). Additional file types can be added to the upload form by clicking on the
"Add Another Post -Construction File Upload" link immediately following the file upload
section of the form.https:Hedocs.deg.nc.gov/Forms/SW Project Submittal
Response: Noted. When uploading the elelctronic files, each file will be uploaded under
its appropriate file type.
17. Please do not upload copies of the review fee check through the electronic file upload
portal. These electronic files end up in our public online repository that can be accessed
by anyone with an internet connection (we do screen the uploads before releasing them
to the repository to prevent sensitive information from being posted, but it should still be
avoided).
Response: Noted. Copies of the review fee check will no longer be uploaded through the
electronic file portal.
18. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other
documents, and a response to comments letter briefly describing how the comments
have been addressed.
a) Pdfs must be uploaded using this form at:
https:Hedocs.deg.nc.gov/Forms?SW-Supplemental-Upload
Response: PDFs of all revisions, 2 hardcopies of the revised plan sheets, 1 hardcopy of
other documents, and a response to comments letter have been provided.
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b) Hard copies must be mailed or delivered to the following address:
i. For Fed Ex/UPS:
Suzanne McCoy
512 N. Salisbury Street, Office 640K
Raleigh 27694
For USPS:
Suzanne McCoy
1612 Mail Service Center
Raleigh, NC 27699-1612
Response: Noted. Hard Copies will be now delivered to the addresses listed above.
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