SW3240501_Response To Comments_20241004

KL E/NFEL DER
Bright People.Right Solutions.
September 26, 2024
Kleinfelder File No.
Brianna Holland
DEMLR Post-Construction Stormwater Program
512 North Salisbury Street
Raleigh, NC 27699
SUBJECT: PLAN REVIEW COMMENTS—PROJECT HOIST
COMMENT RESPONSE LETTER
Kleinfelder Project No.: 24003220.001A
Stormwater Permit No.SW3240501
Dear Holland:
1. General:
a. The State's definition of a sand filter includes not only the sand layer through
which stormwater runoff filters but also the above-ground detention in both
the sediment chamber area (forebay) and sand chamber(area above the layer
of sand). While the 'dry detention ponds with sand filters' configuration are
common in the locally regulated Charlotte area,they are not officially
recognized as a combination of stormwater control measures (SCMs) or as a
distinct SCM by the State.Therefore,the proposed system would be classified
as a 'sand filter' rather than a 'dry detention pond with sand filter'. Please
revise as needed.
b. 15A NCAC 02H .1003(3)(a)—The proposed SCM design does not meet the
definition of Runoff Treatment. In order fora project to meet Runoff
Treatment, the net increase in BUA must be captured and treated in one or
more primary SCMs. Currently,there is BUA associated with this project that is
not directed to a primary SCM (shown in the clip below). (If it is not possible to
direct all BUA to an SCM,the bypassed area of the project can be permitted as
a low-density area, provided it meets all of the requirements outlined in 15A
NCAC 02H .1003(2)).
Response:
a. Please see the revised plans and reports.All mention of dry detention pond have been revised
accordingly to state sand filter.
b. Please see the revised spreadsheets provided in the stormwater report.
2. Consistency:
Please revise the following items for consistency:
a. The narrative states "The proposed project has an impervious area of 7.72
acres of the 10. 95 acres draining to the sand filter, or 70. 5%of the total is
impervious.The Application Section IV, 1 states: "Total impervious of 6.98
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acres..."
b. Line 2 of the Supplement-EZ Cover Page should be revised to match the
project area listed in the Application Section IV,7.
Response:
a. Please see the revised Stormwater Management Permit Application Form which has been
revised to maintain consistency with the stormwater report and plans.
b. Please see the revised Supplement-EZ Cover page which now maintains consistency with the
stormwater management permit application.
3. SUPPLEMENT-EZ FORM
lx hard copy of the complete, original Supplement-EZ Form is required per Sections V
& VI, 3 of the Application.
a. Drainage Areas Page:The Entire Site Column appears to have been
removed and therefore could not be reviewed at this time for correctness.
Include this column in your resubmission.This column should be an
accounting of the entire project, including what is not being directed to the
SCM.
b. Drainage Areas Page, Line 19:The design storm used to calculate the design
volume listed in Line 20 is 1 inch. Please revise for consistency.
c. Sand Filter Page, Line 9: Please explain what "other" is in Line 43.
d. Sand Filter Page, Line 18:The provided SHWT report states the SHWT is
estimated at an elevation of 755.
e. Sand Filter Page, Lines 23, 26, 30:These values could not be found in the
calculations in order to verify their accuracy. Please direct the reviewer to the
source of these values.
f. Sand Filter Page, Lines 25, 31:The Sand Filter Cross-Section Detail provided
in the plans indicate that the sediment and sand chamber have the same
bottom elevation. Please revise the plans or Supplement-EZ for consistency.
Note: The bottom of the sand chamber refers to the top of the sand layer.
g. Sand Filter Page, Line 32:This value refers to the cross-sectional area of
the sand chamber(not just the sand layer) at the top of the sand layer
elevation.
h. Sand Filter Page, Line 33:The physical depth of the sand chamber does not
refer to the depth of the sand layer that is provided, but rather the physical
depth provided above the sand layer(similar to Line 27 for the sediment
chamber).
i. Sand Filter Page, Line 34—The ponding depth of the sand chamber is the
depth from the lowest bypass invert (Line 35)to the top of the sand layer
(Line 31).
j. Sand Filter Page, Line 35-36:The detail sheet indicates the lowest bypass is
(2) 3'W WEIRS ELEV. 768.40.
k. Sand Filter Page, Line 37:The plans indicate this is accomplished through a
rip rap berm,
1. Sand Filter Page, Line 38: See earlier comment with regard to Sand Filter MDC 6.
m. Sand Filter Page, Line 39:This value refers to the depth of the sand
layer being provided above the underdrain pipe.
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Response:
a. Please see the revised EZ Form which now includes the missing columns.
b. Line 19 of the drainage areas tab has been revised for consistency.
c. Other has been removed.There is nothing unique about the sand filter design. Kleinfelder has
revised this to be pump.
d.The EZ form has be revised to maintain consistency with the plans and design.
e. Please see the additional Pond volume tables provided for the sediment chambers and Sand
Filter within the stormwater report. Line 23, and 26 can be found in the tables. Line 30 can be
found by subtracting the sediment chamber volume table total storage from the total storage
volume table value. 84,888 cu.ft.—31,000 cu.ft. = 53,888 cu.ft.
f. We have revised lines 25 and 31 to be consistent with plans and volume tables.
g. See the volume tables for the values used to generate the calculation.The surface area at 767
for the total volume table—the surface areaw at 767 for the sediment chambers is how this
number was generated. 16,937-4,637=12,300.
h.The calculation is from 768.40'—766' = 2.4' = 28.8 inches.This line has been revised.
i.The calculation is from 768.40'—766' =2.4' = 28.8 inches. See EZ form for revisions.
j.The sand filter calculation has been revised to show the correct bypass.
k. Line 37 has been revised to maintain consistency with the plans.
I. Line 38 in the EZ form has been revised to the appropriate specification.
m.This has been revised to 30 inches or 2.5'.
4. CALCULATIONS:
1x signed, sealed, and dated hard copy of calculations with the following corrections
made: (This item is required per Section VI, 7 of the Application)
a. The provided stage storage table is for the sand filter as a whole,this is
acceptable, but please additionally provide stage storage tables that
separate the sand chamber and sediment chamber so that compliance with
Sand Filter MDC 2 may be verified.
Response:
a. See the revised stormwater report which now includes stage storage tables for the sand
filter, and the sediment chambers.
5. Plans:
2x hard copies of revised plan sheets with the following corrections made:
(This item is required per 15A NCAC 02H.1042(2)(g) and per Section VI, 8 of the Application)
a. Per the notes provided on Sheet C-600, "All sand filters shall have a min. 20'
access easement connecting to a dedicated public right of way.Access road
shall have a min. 12'stabilized width, max long. Grade of 15%, max cross-
slope 5%. In addition, a 10-foot wide permanent easement must be provided
around the perimeter of all BMP's to allow for adequate maintenance and
repair."These are acceptable parameters for an easement, but a delineated
easement meeting these criteria was not found on the plans. Please direct the
reviewer's attention to this easement, or provide a revised plan sheet
showing the easement that is to be recorded. Easements must be shown on
plans per 15A NCAC 02H .1042 (2)(g). Ensure the entirety of the SCM is shown
within the easement including the outlet of the SCM.
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b. Sand Filter MDC 6—Please specify that the sand to be used in the sand filters
must be ASTM C33 or equivalent. It is noted that "concrete sand" is specified
on the plan sheets however we require "ASTM C33 or equivalent" be
specified.
c. Per Sand Filter MDC 9,the clean out pipe shall be capped. Please note the cap
on the detail sheet. It is recommended to specify a PVC pipe that has glued
clean-outfittings
d. with screw type caps.
Response:
a. Please see the revised sheet C250 which includes the maintenance access path from the
roadway access to the BMP.
b.All the text is exploded to lines so we need to figure out the font that was used and the size.
Just to change "concrete"to "ASTM C33"
c. Please see the revised callout on sheet C-600 in the "SAND FILTER CROSS-SECTION" detail
which reads "PVC PIPE CLEANOUT W/GLULED CLEAN-OUT FITTINGS WITH SCREW TYPE CAPS.
MAXIMUM SPACING =50'.THE ENDS OF EACH UNDER DRAIN PIPE SHALL BE CAPPED."
5. Please ensure the items that were submitted as hard copies to make the
application administratively complete are uploaded to the electronic
repository.
The following items were noted to be missing:
• The Applicant is Beacon Acquisitions LLC, please provide documentation
supporting the signatory authority of Jon Morris and that Beacon
Acquisitions LLC is in good standing with the Secretary of State, per 15A
NCAC 2H.1003( e) and 15A NCAC 02H .1040(1).
Response:
a.The appropriate documentation has been included with this resubmittal.
6. Please provide a Response to Comments letter indicating, in a point-by-point
manner, how each of the above comments has been addressed.This item is
required per 15A NCAC 02H .1042(3)(b).
Response: Noted.
7. 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 the form at:
https://edocs.deq.nc.gov/Forms/SW-Supplemental-Upload
b. Hard copies must be mailed or delivered to the following address:
i. For FedEx/UPS:
Brianna Holland
512 N. Salisbury Street,
Office 625Y Raleigh, NC
27604
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ii. For USPS:
Brianna Holland
1612 Mail Service Center Raleigh, NC 27699-1612
iii. Hand Delivery:
Please reach out to me prior to hand delivering a submission to make
sure that I (or someone else in my group) will be able to receive the
submission. Do not leave the package in the foyer with the security
guard.
Response:
a. Noted.
b. Noted.
While not acquired to be addressed, the following is recommended:
• There is no maximum drainage area for sand filters; however, sand filters
with smaller drainage areas (less than five acres) usually have fewer
maintenance issues. Multiple sand filters can be used throughout a
development to provide treatment for larger sites.
• Sand Filter MDC 8 —While not required, it is recommended to increase the
sand surface area to encompass the entire bottom of the sand chamber (as
shown in Figure 1 in Part C-6 of the Stormwater Design Manual). As the
sand filter ages, it becomes clogged with sediment and the infiltration rate of
the sand decreases, which can result in the sand filter being out of
compliance with this MDC.
Response: Noted.
Sincerely,
KLEINFELDER
Michael Patterson
Project Professional
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