SW3190506_Response to Comments_20190820

August 20, 2019
Jim Farkas
Environmental Engineer
North Carolina Department of Environmental Quality
Division of Energy, Mineral, & Land Resources - Stormwater Program
512 N. Salisbury Street
1612 Mail Service Center
Raleigh, NC 27699-1612
RE: SW3190506 -Response to 2nd set of Comments — Sealand Office
CardnaC
Cardno
9800 Southern Pine Blvd
Suite I
Charlotte, NC 28273
USA
Phone [phone]
Fax [phone]
vnvw,cardno.com
Mr. Farkas,
Cardno,is pleased to provide the attached response to comments provided by your office dated August 15'
2019. The comments from the referenced letter have been reproduced below and addressed as follows:
The distinction between high density and low density is more nuanced than just
percent impervious cover. As iterated to you in an email on June 27th, 2019, the
project does not qualify as low density since it is not designed to maximize
dispersed flow through vegetated areas and minimize channelization of flow as per
15A NCAC 2H .1003(2)(b). An abundance of non -vegetated conveyances also
prevents this project from being classified as low density. Please ensure that the
project satisfies all of the requirements associated with a high density project.
Please refer to the NCDEQ Stormwater Design Manual for clarification on low
density requirements:
Response: Applications now reflect high density development
2. The "% Impervious Area"`" (total)" row of the drainage area table is specific to the
drainage area. Since there is 102,095 SF of proposed impervious area and the
size of the drainage area is 257,004 sf, the "% Impervious Area" (total)" would be
102,095 sf / 257,004 sf = 39.7%. Please revise (Section IV, 10),
Response: Section IV, 10 has been updated
3. Please provide facility sizing calculations (Section
Response: Sand Filter Sizing calculation has been added to this submittal
4. Please show the wetlands on the plans (Section VI, 8, m).
Response: Wetlands are not in the portion being developed at this time. They
have been shown on the cover sheet for areas outside of the developed area.
Please clarify what happens downstream of FES-2. Based on the contours, it
appears that water would flow from FES-2 to the 687 foot contour line, via the
proposed ditch. Since the berm of the sand filter is at 688 feet, the flow would not be
able to go over the berm and into the sand filter. It appears that the water would go
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August 20, 2019
Cardno®
around the facility and leave via the emergency spillway area. If this is the case, the
drainage area to the facility should be revised to reflect this, if not, please provide
clarification for how the water from FES-2 will enter the sand filter (Section VI, 8, o).
Response: 15" RCP has been extended into the sand filter forebay
6. The stage -storage table used in HydroCAD does not match the stage -storage
table in the plans. Please revise for consistency.
Response: Plan has been updated to match the stage storage table in
HydroCad
7. On the Supplement-EZ form:
a. Change the density from low to high.
Response: revised to High
b. The project does not appear to use an off -site SCM. Please correct the formor
provide information on the off -site SCM.
Response: Corrected, there is not an off -site SCM
c. The information for the drainage area to the SCM should be filled in under the
"1" column, not the "Entire Site' column of the drainage area information table.
The "Entire Site' column should have the information for the entire site.
Response: Sand Filter drainage are moved to 1 column
d. Please enter the SCM design volume on line 2 of the sand filter sheet.
Response: design volume has been added to line 2
e. Please fill in the information on the following lines of the sand filter sheet:3, 4,
15,18, 28, 34, 35, 36, and 37.
Response: the above lines have been updated in the Sand Filter sheet
8. Provide pdfs of all revisions, 2 hardcoaies of revised plan sheets. and 1
hardcopy of other documents (The last submission did not include any hard
copies). Pdfs must be uploaded using the form at:
https://edocs.deg.nc.gov/Forms/SW Project Submittal
Response: 2 hard copies of these revised plans and the last submission has
been mailed to you. This submission has also been electronically uploaded,
If you have any questions or need any additional information pertaining to the response to comments, please do
not hesitate to contact me.
Sincerely,
Frank Cantrell, PE
Senior Project Manager
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