SW3230303_Response To Comments_20230803

azeri Hazen and Sawyer
9101 Southern Pine Blvd,Suite 250
Charlotte,NC 28273•704.357.3150
August 2,2023
Brianna Holland
512 N. Salisbury Street, Office 640E
Raleigh,NC 27604
Re: Twelve Mile Creek WRF 9.0 MGD Expansion
Post Construction Stormwater Application—SW3230303
Dear Ms. Holland,
Please find enclosed the requested revisions to this application. Included are two(2)hard copies of the
revised drawing set and one(1)hard copy of the revised narrative,which includes an updated
supplement-EZ Form,calculations, and wetland certification statement. This response letter addresses the
comments received on July 7, 2023.
Review Comment 1: Please verify that the deed is the correct deed for the property. Per the Union County
GIS, the parcel number associated with the property is 06162001 and the associated area is 56.655 acres,
which corresponds to the area listed on the application and narrative.The provided deed references 132.004
acres.A copy of the most current property deed is required per the Application Section VI, 10.
• The deed provided is the property's current deed per Union County Water.
Review Comment 2a: Low Density — Sheet is missing. This page is generated when "load forms" is
selected after"low"is selected for Line 5 on the cover page. Please provide.
• This sheet has been provided in Appendix E of the narrative.
Review Comment 2b: Cover Page, Line 7—Per 15A NCAC 02H .1017 (10), the vegetated setback shall
be at least 30 feet in width. Please show vegetated setbacks on plans so that built-upon area requirements
within setbacks can be verified(required per Section VI, 8o).
• This update has been provided on sheet C21. The BUA was not affected by this change.
Review Comment 2c: Cover Page,Line 8—Per 15A NCAC 02H.1003 (4)(b),the vegetated setback must
remain vegetated.
0
0
• Updated and provided.
hazenandsawyer.com

Hazen Brianna Holland
August 2,2023
Review Comment 2d: Drainage Areas, Line 16 — "Existing area that is already permitted" is "245,430
SF,"however,there is not an existing permit for this property, so this line should remain blank.
• That line has been updated as requested.
Review Comment 3a: Dimension project or project phase boundary with bearings&distances per Section
VI, 8i of the application and 15A NCAC 02H .1042 (2) (g) (ii).
• Sheet C4 updated to include property boundary with bearings and distances.
Review Comment 3b: Wetlands noted in the narrative should be delineated on the plans if they are on-
site. (Must be delineated by a qualified person. Provide documentation of qualifications and identify the
person who made the determination on the plans, required per Section VI, 8m of the application and 15A
NCAC 02H.1042(g)(iii).The U.S.Fish and Wildlife Service National Inventory is not a qualified person.
If no wetlands are on site, provide a note on the plans stating that there are no wetlands located on-site
along with the qualifications of the individual that made the determination.
• Included the names of investigators on the plans.
• Please see Wetland Investigation Summary in Appendix F of the Narrative. Hazen performed
the jurisdictional determination of WOTUS within and abutting all project areas. With the
exception of Twelve Mile Creek and Twelve Mile Creek Tributary No. 3, no jurisdictional
WOTUS were found to be present in the project areas.National Wetlands Inventory appendix
was removed from consideration.
Review Comment 3c:Ensure that existing drainage pipe sizes and drainage easements are labeled on plans
for all existing pipes as required per Section VI, 8n of the application. Note that most of the pipes shown
on the plans were labeled,but there were a few that did not have the size noted.
• All existing pipes that are shown in the viewports on the plans set, in and outside of the limits
of disturbance,have been labeled with their size as well as material composition.
Review Comment 3d: Please provide Sheet C-22 so that the rip-rap apron sizing can be verified to
correspond to the provided calculations or clarify rip-rap sizing on the provided sheets. Detail C-22-0312
was referenced on the plans and seems to show this information but not included for review and inclusion
with the permit set.
• Detail C-22-0312 is included on Sheet CD2 with pertinent sizing information.
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hazenandsawyer.com

Hazen Brianna Holland
August 2,2023
Review Comment 3e: The BUA information shown in the Application, Supplement-EZ Form, and
calculations should be able to be verified from the plans,please provide dimensions for BUA on the plans.
This item is required per Section VI, 8j of the Application.
• Summary of BUA dimensions included on Sheet C6.
Review Comment 3f: Verify that the existing conditions map is accurate, aerial imagery showed
differences in the site layout. Update the BUA on the Supplement-EZ, Application, and calculations if
necessary.
• Reviewed the drawings compared to aerial imagery and existing conditions. There were no
found discrepancies.
Review Comment 4a: Provide engineering calculations that exhibit that stormwater outlets are designed
so that they do not cause erosion downslope of the discharge point during the peak flow from the 10-year
storm event. Currently, the velocities are shown, but additional information is needed to exhibit if they
would be erosive on the site. Please ensure and provide calculations showing that the stormwater outlets
are stable in accordance with 15A NCAC 2H .1003(5).
• The engineering calculations are provided in the form of rip rap splash pad calculations. They
were performed and implemented on the plans at all outlets that were affected or modified by
this project.
Thank you very much for your consideration of the enclosed resubmittal. Please do not hesitate to reach
out to me with any questions by email([e-mail]) or telephone[phone]).
Respectfully submitted,
44;ct,.._p --2. p..._/,-------f
Michael Parker,PE
Enclosure
cc: Thomas Mann (Union County Water)
Grant Moore (Union County Water)
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