20230767 Ver 2_20230767_v2_StoverNorth_More_Info_Requested_Response_20230921_20230921

Stantec Consulting Services Inc.
801 Jones Franklin Road, Ste 300
Stantec Raleigh NC 27606
September 21, 2023
Ms. Sue Homewood
401 & Buffer Permitting Branch Division of Water Resources
North Carolina Department of Environmental Quality
512 North Salisbury Street
Raleigh, North Carolina 27699
Sue. [e-mail]
Reference: Request for Additional Information: Stover North Data Center; DWR# 20230767v2;
Corps Action ID# SAW-2022-02515; Catawba County
Dear Ms. Homewood,
On behalf of the applicant, Microsoft Corporation (Microsoft), Stantec Consulting Services Inc. (Stantec) is
pleased to submit this response to the North Carolina Department of Environmental Quality (DEQ) Division
of Water Resources' (DWR) request for additional information dated August 21, 2023.
REQUEST FOR ADDITIONAL INFORMATION
Your questions are presented first, followed by our answers in italics.
1. If the USACE requests a response to any comments received as a result of the Public Notice, please
provide the Division with a copy of your response to the USACE to ensure we have all relevant
information to complete our review in accordance with I5A NCAC 02H .0506(b).
Response: A copy of our response to Public Notice comments received from the USACE will be
provided to DWR when they are submitted to the USACE.
2. The profile view of road crossing Impact SD5 indicates that there is a 20-foot paved access road with
approximately 25 feet of unpaved shoulder on either side prior to sloping down toward the stream.
Please explain the reason for the wide shoulders as reduction of this area would provide further
minimization for stream impacts.
Response: The width of the roads at the creek crossings are constrained by the need for utilies to be
located within the roadbeds. As illustrated on the cross-section below (Figure 1) the road crossing at
Impact SD5 will contain:
• A 20-foot-wide roadway in the center.
• One fiber and six concrete encased electrical duct banks to bridge power to the substation.
Design with community in mind

September 21, 2023
Ms. Sue Homewood
Page 2 of 4
Reference: Request for Additional Information: Stover North Data Center; DWR# 2023767v2; Corps Action ID# SAW-2022-00515;
Catawba County
PROPOSED 20' WIDE
PAVED ACCESS DRIVE TO
900 I I SUBSTATION
I �
PROPOSED GONG ENCASED
FIBER DUCT BANK (44"X32")
895 CULVERTS
# s-1 a
INV. : a7asa Li n
890
TEMPORARY 2
IMPACT SG 1
885 PERMANENT
IMPACT SD5
880
875 _ 141�fi 60,, RCP
°@ 3.75%
EXISTING GRADE
870
CULVERT TO BE COUNTERSUNK 12" —�
865
PROPOSED (6)
CONCRETE ENCASED
ELECTRICAL DUCT BANKS
(72"X24"-11' CENTERS)
PROPOSED GRADE
2
1
CULVERTS
it S-13
INV,: B69.38
PERMANENT
IMPACT SD6
900
895
890
885
880
875
870
865
-0+75 -0+50 0+00 0+50 1+00 1+50 2+00
SCALE: HOR 1"=50'; VERT 1" = 10'
Fig 1. Cross -Section at Impact SD5
Duct banks, water lines, sanitary sewers and storm sewers are necessary utilities on data center sites. The
electrical and fiber duct banks make up the bulk of the utilities and are placed in the roadbeds for the
following reasons:
• Drainage issues: Duct banks are installed in such a way that the center of a duct bank run is
higher than both ends. Vaults connect duct bank runs. These slopes drain any condensation or
water that infiltrates the banks to the vaults where the water can be removed by a sump or other
drain. A diagram showing the installation requirements is provided in Figure 2 below (the structure
labeled as "manhole" represents the buried vault and manhole access). Typically, vaults are
installed every 300' although that number can decrease depending on site conditions. A vault is
needed on either side of any stream or wetland crossing.
LE VE L GRCLJNp a URFACE
C5VN43
3 MINIMUM
P UGT RL+N
MANHOLE
https://construction manuals.tpub.com/14027/css/Ducts-and-Trenches-91.htm
Figure 2. Slopes for Duct Runs
Design with community in mind

September 21, 2023
Ms. Sue Homewood
Page 3 of 4
Reference: Request for Additional Information: Stover North Data Center; DWR# 2023767v2; Corps Action ID# SAW-2022-00515;
Catawba County
Placing the duct banks under the streambed in such small, steep stream valleys would make this
type of sloping difficult, if not impossible. Installing short segments would not allow for adequate
drainage and could create conditions conducive to water collection in the duct banks that could
damage either fiber or electrical lines.
Installation of the duct banks: The size of duct bank and the required separation distance
between duct banks depend on the type of duct bank (electrical versus fiber optic). Would lead to
very large areas of temporary impacts and an additional mass grading operation of the surrounding
slopes. Typical duct bank cross -sections for this project are provided on Figure in Attachment 1.
Requirements dictate a 65-foot separation distance between fiber duct banks and the electrical duct
banks must be either 4 or 6 feet apart depending on size. The vaults installed at the end of each
duct bank run are large structures. Electrical vaults are large boxes measuring 11 feet on each side
and fiber vaults measure 12 foot 8 inches by 8 feet or 16 foot 11 inches by 9 feet 1 inch. Please
refer to Figures 2 and 3 in Attachment 1. Installation of duct banks and vaults is a massive
operation as shown on Figures 4 and 5 in Attachment 1.
• Environmental: While constructing the duct banks under the stream would be considered
temporary impacts, installation of the duct banks and the vaults required to connect the duct banks
to the rest of the networks would include large areas of additional clearing and grading. This would
remove large areas of existing tree cover on the stream banks which are currently planned to be
preserved.
Security: Duct banks and vaults must be located within security fencing as these are secure
facilities. If the ducts were placed through stream channels the security fencing would be expanded
around the crossings and, depending on visibility, may require permanent stream impacts for
perimeter access roads for use during daily security inspections.
Safety: Installation of the duct banks in the stream valleys would put vaults more than 20' below
ground. The vaults must be easily accessible for regular inspection and maintenance of the cables.
Additionally, with the construction of each new building the vaults need to be opened for new fiber
installation.
The site plan layout was designed to maximize the area for required buildings and infrastructure
including stormwater ponds while avoiding and minimizing impacts to waters. In addition to the
constraints listed above, the following issues would also apply to the two road crossings:
Impact SD5 — Moving the utilities would not be possible due to the transmission line right of way
upstream of the crossing and the stormwater treatment facility on the northeast side of the road
crossing. Utilities cannot be installed in the slopes of a stormwater facility. Stream SD also has
incised slopes within this area downstream of the transmission line. The site layout around Impact
SD5 is provided in Figure 3 below as well as Figure 6 of Attachment 1. The cross section is
provided in Figure 1 above as well as Figure 7 of Attachment 1.
Design with community in mind

September 21, 2023
Ms. Sue Homewood
Page 4 of 4
Reference: Request for Additional Information: Stover North Data Center; DWR# 2023767v2; Corps Action ID# SAW-2022-00515;
Catawba County
�7 /-
PROPOSED SUBSTATION
e°
/2 i
PERMANENT IMPACT SD6
♦ _ STREAM SD (RIP RAP)
±30 LF (±240 SF)
PERMANENT IMPACTSD6
STREAM SD fClll VFRT1
NOTE
7_ as
a
z St
Pi
01
Figure 1. Site Layout at Impact SD5
Thank you for your assistance with the permit applications. If I can be of further assistance, please contact
me at [phone] or amber.coleman(Qstantec.com if you have any questions.
Sincerely,
STANTEC CONSU TING SERVICES INC.
Amber Coleman, LSS, PWS
Senior Environmental Scientist
Phone:[phone]
[e-mail]
Attachments: Attachment 1: Duct Bank Visuals
Cc: Krysta Stygar (USACE), Claire Wolanski (Microsoft), Loretta Cummings (Stantec)
Design with community in mind

Figure 1. Duct Bank Cross -Sections
FINISH GRADE
3'- s 1rz'
TYPICAL (24) 4" CONDUIT
DUCTBANK CONCRETE ENCASED
UNDER ROADWAY
FINISH GRADE
W
� I
3 1.4MiN
0
o —
PAVEMENT SECTION
WHERE APPLICABLE
COMPACTED SELECT BACKFI__
- DUCT BANK TO BE MARKED
WITH DETECTABLE WARNING
TAPE AS SPECI FIED
3500 PSI CONCRETE WITH #4
REBAR AT 8" O-C.
LONGITUDINALLY AND#4 TIES
AT 24" O-C.
REFER TO SPECIFICATION
SECTION 27 05 43-10 FOR
REQUIREMENTS
4-INCH CONDUIT (TYP" OF 24)
CONDUIT SUPPORTS
EVERY 5'-0°
4" THICK COMPACTED
SELECT BACFILL
PAVEMENT SECTION
WHERE APPLICABLE
COMPACTED SELECT BAC FILL
DUCT BANK TO BE MARKED
WITH DETECTABLE WARNING
TAPE AS SPECIFIED
3500 PSI CONCRETE WITH #4
REBAR AT 8" O-C-
LONGITUDINALLY AND #4 TIES
AT 24" O-C-
REFER TO SPECIFICATION
SECTION 27 05 43-10 FOR
REQUIREMENTS
4-INCH CONDUIT{TYP" OF 12)
CONDUIT SUPPORTS
EVERY 6-0"
IWIDTH AS REQUIRED � 4" THICK COMPACTED
SELECT BACKFILL
TYPICAL (12) 4" CONDUIT
DUCTBANK CONCRETE ENCASED

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