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Nationwide Permit No. 12, Pre -Construction Notification — Supplemental Information
• U.S. Army Corps of Engineers — Wilmington District
of the bank if no herbaceous strip exists. Initial grading of the herbaceous strip will bellimited to
the extent needed to create a safe approach to the waterbody and to install temporary bridges.
During clearing, sediment barriers will be installed and maintained across the right -of- ..
way adjacent to waterbodies and within ATWS to minimize the potential for sediment runoff.
Erosion control devices located across the working side of the right-of-way will be removed
during the day when vehicle traffic is present, and will be replaced each night. Alternatively,
drivable berms may be installed and maintained across the right-of-way in lieu of silt fences, coir
logs, and/or straw bales.
Typically, equipment refueling and lubricating at waterbodies will take place in upland
areas that are 100 feet or more from the edge of the waterbody and any adjacent wetlands.
However, there will be certain instances where equipment refueling and lubricating may be
necessary in or near waterbodies. For example, stationary equipment, such as water pumps for
withdrawing hydrostatic test water, may need to be operated continuously on the banks of
waterbodies and may require refueling in place. In this event, the pumps would be refueled in a
secondary containment structure and all fuels stored more than 100 feet from the edge of the
waterbody or adjacent wetlands. Atlantic's Spill Prevention, Control, and Countermeasures Plan
(SPCC Plan) addresses, among other items, the handling of fuel and other materials associated
with the ACP. As required by the Procedures, the SPCC Plan will be available during
construction on each construction spread. The SPCC Plan is provided in Appendix G.
• After the pipeline is installed across a waterbody using one of the methods described
below, the trench will be backfilled with native material excavated from the trench. If present
and moved prior to construction, larger rocks or boulders will be replaced in the stream channel
within the construction area following backfill of the trench. The streambed profile will be
restored to preconstruction contours and grade conditions to prevent scouring. The stream banks
will then be restored as near as practicable to preconstruction conditions and stabilized.
Stabilization measures will include seeding, installation of erosion control blankets, or
installation of riprap materials, as appropriate. Jute thatching or bonded fiber blankets will be
installed on banks of waterbodies or road crossings to stabilize seeded areas. Temporary erosion
controls will be installed immediately following bank restoration. The waterbody crossing area
will be inspected and maintained until restoration of vegetation is complete.
Open -Cut Method
The open -cut or wet trench crossing method will involve trenching through the
waterbody while water continues to flow through the trenching area. Prior to initiating
construction across the waterbody, the crossing section of pipeline will be fabricated (i.e., bent,
welded, and coated) in adjacent ATWS areas. Backhoe -type excavators will then be used to
excavate a trench in the flowing waterbody from one or both banks of the waterbody. Where the
waterbody is too wide to excavate the trench from the banks, equipment may operate from within
the waterbody with approval from the appropriate regulatory agencies. Equipment operating
within the waterbody will be limited to that needed to construct the crossing. During these
operations, flow will be maintained at the crossing as specified in the Procedures. Turbidity
curtains will be installed downstream of the crossing as necessary to minimize suspended solids
in the water.
Atlantic Coast Pipeline 18

I s
Permit No. 12, Pre -Construction Notification — Supplemental Information
`nmc nfFnoinrrre— Wilminofnn rlictrirt
theVI Temporary sidecast material excavated from the trench will be placed on the bank above
high water mark (at least 10 feet from the edge of the water) or placed adjacent to the trench
in the stream (major waterbodies only, in accordance with the Procedures) for use as backfill. A
prefabricated segment of pipeline will then be placed into the trench using side -boom tractors.
Concrete coating (installed in uplands in project workspace) or bag weights will be utilized, as
necessary, to provide negative buoyancy for the pipeline. Once the trench is backfilled, the
banks will be restored as near as practicable to pre -construction contours and stabilized as
described above. Excavated material not required for backfill will be removed and disposed of at
approved upland disposal sites.
Throughout the construction process, Atlantic will follow the Procedures to avoid or
minimize impacts on water quality. Construction activities will be scheduled so that the trench is
not excavated across the waterbody until immediately prior to pipe laying activities. The
duration of in -stream construction activities (excluding blasting, if required) will be limited to
24 hours across minor waterbodies (those 10 feet in width or less) and 48 hours across
intermediate waterbodies (those between 10 and 100 feet in width).
Flume Method
The flume crossing method consists of isolating and temporarily diverting the flow of
water across the trenching area through one or more large -diameter, steel flume pipes placed in
the waterbody. This method allows for trenching activities to occur within a relatively dry
stream or riverbed (beneath the flume pipes containing the water flow), thereby minimizing
sediment and turbidity within the waterbody. The flume method is typically used to cross small
to intermediate flowing waterbodies that support Coldwater or other significant fisheries.
For each waterbody where the flume method is implemented, a sufficient number of
adequately sized flume pipes will be installed in the waterbody to accommodate the highest
anticipated flows during construction. Atlantic will use stream gauge data from the USGS to
determine the highest anticipated flows during the time the flume crossing is in effect. In the
absence of stream gauge data, Atlantic's engineers and Environmental Inspectors will estimate
the highest anticipated flows based on the width of the waterbody at the ordinary high water
mark, the depth of the waterbody, existing flows at the time of the crossing, and the weather
forecast at the time of the crossing. As a contingency, Atlantic will stage additional flume pipes
at the crossing in the event that the volume of flow increases due to a precipitation event.
Prior to installation, Atlantic will inspect the flume pipes to confirm that they are free of
dirt, grease, oil, or other pollutants. After placing the pipes in the waterbody, sand- or pea
gravel -filled bags, water bladders, or metal wing deflectors will be placed in the waterbody
around the flume pipes upstream and downstream of the proposed trench. These devices will
serve to dam the stream and divert the water flow through the flume pipes, thereby isolating the
water flow from the construction work area between the dams.
After installation of the flume pipes, any remaining standing water between the dams will
be pumped out. Pump intakes will be appropriately screened to prevent entrainment of aquatic
species. Fish trapped in the dewatered area will be removed and returned to the flowing
waterbody. Leakage from the dams or subsurface flow from below the waterbody bed may
Atlantic Coast Pipeline 19

Nationwide Permit No. 12, Pre -Construction Notification — Supplemental Information
• U.S. Army Corps of Engineers — Wilmington District
General WQC Activity Specific Condition 5) 50 foot Construction Corridor
Construction corridors in wetlands and across stream channels shall be minimized to the
maximum extent practicable and shall not exceed 50 feet wide for gas utility lines and 40 feet
wide for all other utility lines. Exceptions to this condition require application to and written
approval from DWR.
Atlantic is requesting the waiver for Activity Specific Condition 5 due to the fact that a
50 foot work area through wetlands and across stream channels is not wide enough to safely
install a 36 -inch pipe. Construction of the ACP will require additional workspace beyond 50 feet
in wetland areas. Justification for the additional workspace is as follows: AP -2 in North Carolina
will be 36 -inch diameter pipe, which requires large construction equipment to install. The
construction space in wetlands consists of a trench necessary to accommodate the pipe at an
appropriate depth (3-5 feet beneath the surface), adjacent space to place excavated material from
the trench excavation, and travel of equipment alongside the trench for pipe installation. Soils in
wetlands areas are generally less stable than adjacent upland areas, therefore additional shoring is
necessary to achieve the appropriate trench depth resulting in a trench that is wider than in
adjacent upland areas. In addition, the extra material that is excavated requires more space for
temporary side -casting and the instability of the soil requires that the travel corridor adjacent to
the trench be at a safe distance so that failure of the trench walls does not occur. In addition, the
extra width of workspace maintains space for safe operation of heavy equipment in the already
reduced workspace in wetlands.
• In addition to the construction right-of-way, additional temporary workspace (ATWS)
will be required at various locations along the construction right-of-way, such as at the beginning
of each construction spread for mobilization of construction equipment; for stringing -truck
turnaround areas; where the pipeline crosses under buried features (e.g., foreign pipelines, utility
lines); at road crossings, railroads, wetlands, waterbodies; residential areas, and at HDD
crossings.
ATWS also will be required in areas with side slopes to create a level and safe work
surface across the width of the right-of-way for equipment operation. For the AP -2 mainline,
ATWS measuring 25 by 100 feet will typically be required on both sides of the corridor and both
sides of the crossing at wetlands, waterbodies, roads, and railroads. The FERC's Procedures
require that ATWS be set back at least 50 feet from the wetland boundaries and the water's edge
of waterbodies, except where the adjacent lands consist of croplands or other disturbed areas.
Following construction of the pipelines, ATWS will be restored to pre-existing conditions and
uses.
Atlantic has identified roads which will be used to provide access to the Project
construction rights-of-way, permanent easement, and other facilities during construction and
operation of the ACP. Atlantic will utilize existing roads to the extent practicable, but some new
roads may need to be built in remote areas. Additionally, new roads will need to be built to
provide access to aboveground facility sites (i.e., compressor and M&R stations, valves, and pig
launcher/receiver assemblies) during operations. In some cases, existing roads will require
improvement (such as grading, gravelling, replacing or installing culverts, minor widening,
• and/or clearing of overhead vegetation) to safely accommodate construction equipment and
Atlantic Coast Pipeline 16

Nationwide Permit No. 12, Pre -Construction Notification — Supplemental Information
U.S. Army Corps of Engineers — Wilmington District
vehicles: A sufficient number of roads with regular spacing are needed to minimize congestion
of construction vehicles and equipment on the right-of-way; having fewer access roads would
increase the duration of construction and create unsafe work conditions for workers. If any
existing roads are damaged during construction, Atlantic will restore these roads to
preconstruction condition or better. See Appendix C for access road impacts.
General Construction Procedures
Refer to Appendix D for a discussion on general construction procedures.
Waterbodv and Wetland Construction Procedures
Atlantic will use special construction techniques where warranted by site-specific
conditions, e.g., when constructing across waterbodies, and wetlands. Each of these specialized
measures is described below. Illustrations of select crossing methods are provided in
Appendix E and site-specific plans are provided in Appendix F for crossings of Section 10
waterbodies.
Waterbody Crossings
Atlantic will use the open -cut, flume, dam -and -pump, conventional bore, cofferdam, or
HDD methods to construct the pipelines across waterbodies. In each case and for each method,
Atlantic will adhere to the measures specified in the Procedures; site-specific modifications to
the Procedures as requested by Atlantic and approved by the FERC. As well as any additional
requirements identified in federal or state waterbody crossing permits, including applicable
permits and approvals from the USACE and various state agencies (see Section E5). A complete
list of the waterbodies along the proposed pipeline routes within the Wilmington Distict, and the
construction method proposed for each crossing, is provided in Appendix C. Construction
methods for waterbodies that isolate the pipeline trench from flowing water (e.g. flume, dam -
and -pump, cofferdam) will be utilized where these methods are proposed and perceptible flow is
present at the time of the crossing.
During the clearing and grading phase of construction, temporary bridges will be
installed across waterbodies in accordance with the Procedures to allow construction equipment
and personnel to cross. The bridges may include clean rock fill over culverts, timber mats
supported by flumes, railcar flatbeds, flexi-float apparatuses, or other types of spans.
Construction equipment will be required to use the bridges, except that the clearing and bridge
installation crews will be allowed one pass through waterbodies before bridges are installed. The
temporary bridges will be removed when construction and restoration activities are complete.
ATWS will be required on both sides of waterbody crossings to stage construction
equipment, fabricate the pipeline, and store construction materials. The ATWS will be located at
least 50 feet away from the water's edge at each waterbody (with the exception of site-specific
modifications as requested by Atlantic and approved by the FERC).
Clearing adjacent to waterbodies will involve the removal of trees and brush from the
construction right-of-way and ATWS areas. Woody vegetation with' construction right-of-
way will be cleared to the edge of each waterbody. Sediment barri fs ma , e installed at the top
Atlantic Coast Pipeline 17 St1t�l'I