SW3191101_Responce to Comments_20200414

Bohler Engineering NC, PLLC
1927 South Tryon Street, Suite 310
Charlotte, NC 28203
980.272.3400

April 13, 2020
North Carolina DEQ
Energy, Mineral, and Land Resources
512 North Salisbury St.
1612 Mail Service Center
Raleigh, NC 27699

Attn: Jim Farkas

Re: Comment Response Letter
Cambridge Village MF
Permit No. SW3191101
North Pilot Knob Road
& Cresset Dellinger Road
Denver, North Carolina
BE #NCC172159.1

Bohler Engineering is pleased to submit on behalf of North Pilot Knob Road, LLC, the revised Construction
Documents for the Cambridge Village Multi-Family Development located at the corner of North Pilot Knob Road and
Cresset Dellinger Road in Denver, North Carolina. The following is our comment response letter addressing
comments received from the North Carolina Department of Environmental Quality dated February 4, 2020. Each
comment is addressed and responded to as follows:

Comment 1: As designed, the main pool volume of wet pond 2 is too small. The SA/DA value from the table
should be interpolated based on the actual percent impervious cover of the drainage area (35%)
and the actual average depth of the wet pond (4.3 ft). Interpolating from the SA/DA table yields a
SA/DA ratio of approximately 1.04%. This results in a minimum required surface area of 6,867 sf
whereas 6,548 sf is provided. Please revise.
Response 1: Wet pond 2 has been redesigned with the offsite by pass in mind. The new impervious
percentage is 56% and average depth is 5.3 ft. This yields an approximate SA/DA ratio of
1.44 giving a required surface area of 4,993 sf whereas 8,292 sf is provided.

Comment 2: It appears that the “north half” of the project (proposed DAs 1 & 3) eventually drains to Mountain
Island Lake (WS-IV, CA) and the “south half” of the project drains to Forney Creek (C). It appears
to have been switched on the Application (Section IV, 10). Please check with Lincoln County to
ensure that all local Water Supply Watershed rules have been adhered to since Water Supply
Watershed rules are enforced at the local level, not the State level.
Response 2: Noted – thank you. Reseach has been completed and the northern portion of the project is
below the BUA threshold for the WS-IV watershed.

Comment 3: Based on the provided BUA table in the email dated March 24, 2020, please correct the following
issues:

a. Please ensure that the BUA table information is included in the main set of plans. Noted and
included
b. Section IV, 10 (Deviations from Application provided with February 18th Submission)
i. Drainage Area 1

1. Proposed Impervious Area & Impervious Surface Area Total – This value should be the Total BUA
for proposed drainage area 1. Corrected
2. On-site Parking – This value should be the On-site Parking for proposed drainage area 1.Corrected
3. On-site Sidewalks – This value should be the On-site Sidewalks for proposed drainage area 1.
Corrected
ii. Drainage Area 2

Comment Response Letter
Cambridge Village Multifamily
NCC172159.1
April 13, 2020
Page 2 of 3

1. On-site Drainage Area – This value should be the sum of the On- site BUA and On-site Pervious
for proposed drainage area 2. Corrected
2. Off-site Drainage Area – This value should be the sum of the Off- site BUA and Off-site Pervious
for proposed drainage area 2. Corrected
3. Proposed Impervious Area & Impervious Surface Area Total – This value should be the Total BUA
for proposed drainage area 2. Corrected
4. On-site Parking – This value should be the On-site Parking for proposed drainage area 2.
Corrected
5. Off-site – This value should be the Off-site BUA for proposed drainage area 2. Corrected
6. Existing BUA*** - This value should be zero (so the numbers add up properly). Corrected

c. Supplement-EZ Form (Deviations from Supplement-EZ Form provided with February 18th
Submission)
i. Drainage Area Page:
1. Entire Site Column:
a. Line 5 – This item should be the Total BUA for the Proposed Project Area. Corrected
b. Line 7 – This item should be the difference between the Total BUA for the Proposed Project Area
and the Total BUA for the Existing Project Area. Corrected
c. Line 10 – These items should be the difference between the applicable On-site BUA for the
Proposed Project Area and the applicable On-site BUA for the Existing Project Area. Corrected
d. Line 13 – This item should be On-site BUA for the Existing Project Area. Corrected
e. Line 16 – This value should be Line 5 divided by the Total Existing Project Area, expressed as a
percent. This value should correspond to the value shown in Section IV, 8 of the Application.
Corrected
2. Drainage Area Columns:
a. Line 5 – This item should be the Total BUA for the Proposed Drainage Areas. Corrected
b. Line 7 – This item should be the difference between the Total BUA for the Proposed Drainage Area
(Prop DA 1 & Prop DA2) and the Total BUA for the Existing Drainage Area (Ex DA 1 & Ex DA 2).
Corrected
c. Line 8, DA 2 – This item should be the sum of the Off-site BUA and Off-site Permeable areas for
Proposed Drainage Area 2. Corrected
d. Line 9, DA 2 – This item should be the Off-site BUA for Proposed Drainage Area 2. Corrected
e. Line 10 – These items should be the difference between the applicable On-site BUA for the
Proposed Drainage Area and the applicable On-site BUA for the Existing Drainage Area. Corrected
f. Line 13 – This item should be the On-site BUA for the Existing Drainage Area Corrected
Response 3: Please see responses in red above.

Comment 4: Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
i. Line 7 – Please refer to the applicable rules to determine the minimum width of vegetated setback
(from surface waters). Noted
ii. Line 9 – If BUA other than the approved types (Per 15A NCAC 02H .1003(4)(c-d)) is located within
the vegetated setback, this item should be “Yes” otherwise it should be “No”. Corrected
b. Drainage Areas Page:
i. Entire Site Column:
1. Line 17 – Not required. Corrected
c. Wet Pond Page:
i. Line 25, Wet Pond 2 – This value (777.25 ft) does not match the plans and the calculations (778.2
ft). Corrected
ii. Line 34 – Clean out depth is the distance from the permanent pool elevation to the top of the
sediment storage elevation in the forebay. For wet pond 1, this value should be 42 inches (787.5 ft
– 784.0 ft = 3.5 ft = 42 in) and for wet pond 2, this value should be 54 inches (776.5 ft – 772 ft
= 4.5 ft = 54 in). Corrected

Comment Response Letter
Cambridge Village Multifamily
NCC172159.1
April 13, 2020
Page 3 of 3

iii. Line 44, Wet Pond 2 – The forebay exit depth is the distance from the permanent pool elevation to
the forebay exit elevation. This value should be 60 inches (776.5 ft – 771.5 ft = 5 ft = 60 in).
Corrected
iv. Line 48 – Per the provided detail (Drawdown Assembly) on sheets C-911 & C-912, the orifice is
located more than 12 inches below the water surface elevation in the cap on the downward pointing
portion of the T joint. It will draw down from below the permanent pool. These items should be
“Yes”. Corrected
Response 4: Please see responses in red above.

Comment 5: It is recommended that the off-site drainage from upstream properties be diverted around the SCM
since the Applicant cannot maintain control over the development of property that they do not own.
If the Applicant elects to account for off-site drainage, there must be a recorded legal agreement in
place between the Applicant and the Owner of the upstream property in which the Owner of the
upstream property agrees to record a deed restriction limiting the minimum/maximum amount of
BUA on the upstream property that will be treated in the Applicant’s SCM, the locations and sizes
of access and drainage easements, how construction and/or ongoing maintenance costs will be
handled,maintenance responsibility, a list of legal recourses available to each party should one
party fail to hold up their end of the agreement, and any other related legal issues.
Response 5: Bypass storm drainage and ditch provided to route offsite water around proposed BMPs.

Comment 6: NOTE: Per Division policy, the next review of this application will be the final review. Failure to
provide a complete submittal package will result in the project being returned as incomplete. The
return of a project will necessitate resubmittal of all required items, including the application fee.
Response 6: Noted, thank you.

Comment 7: Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other
documents. Pdfs must be uploaded using the form at:
https://edocs.deq.nc.gov/Forms/SW_Project_Submittal
Response 7: PDFs of all revisions, as well as 2 hard copies of revised plan sheets, and 1 hard copy of
other documents have been provided as part of this submission package.

Should you have any questions regarding this project or require additional information, please do not hesitate to
contact me at [phone].

Sincerely,
BOHLER //

Steve Farmartino, PE
Project Manager