Environmental Impact Assessment(EIA) Registration for the ...

REVISED PROJECT DESCRIPTION AND ENVIRONMENTAL IMPACT ASSESSMENT (EIA) REGISTRATION
FOR THE NEPISIGUIT FALLS GENERATING STATION MODIFICATION AND REHABILITATION PROJECT
Construction of the Coffer Dam will require between 2 and 4 weeks. The Coffer Dam will be
constructed of clean, non-ore bearing rockfill to an elevation of approximately 102.7 m (337 ft)
and a length of approximately 41.1 m (130 ft) (Drawing 2, Appendix C). These estimates are
based on preliminary engineering design and the length of the Coffer Dam may vary slightly
during final engineering. The rockfill will be transported to the Project location by dump truck
along existing roadways, and placed or lowered into the water. The rockfill will be placed into
the water from the north bank until it has reached the design elevation of 102.7 m (337 ft).
Prior to the placement of rockfill, the area of the forebay floor will be cleared of debris using a
backhoe to provide a stable, clean surface for the Coffer Dam. Debris collected will be disposed
of according to NB Power’s WAWA Permit.
Once the rock berm has reached its design elevation, an impermeable geomembrane will be
placed in between two layers of geotextile (to provide protection) over the upstream face of the
berm, and anchored in place by divers. The geomembrane will be covered with rip rap to create
an impermeable surface.
Rockfill and rip rap will be obtained for the Coffer Dam construction from an approved borrow
source to be chosen by the contractor after contract award. The location of this site will be
identified by the contractor for approval by NB Power and NBENV prior to Construction.
Following completion of the Coffer Dam, the residual water that has not drained through the
turbines and remains between the Coffer Dam and the power house will be removed using
drains in the power house, and by pumping. Water collected in the sediment pond would be
pumped out over existing vegetation a sufficient distance (at least 30 m from the watercourse)
from the river to prevent suspended solids from re-entering the river. During the final stages of
this dewatering process, a fish biologist will be on site with a fish-out team to monitor fish
presence and undertake fish rescue as required. Any remaining pools in the dewatered forebay
will be fished out using seine or dip nets, and the fish will be relocated to fish habitat upstream.
Floating debris that collects on the upstream side of the Coffer Dam will be removed, and
disposed of in accordance with NB Power’s WAWA permit.
2.2.2 Installation of the Working Platform
A temporary working surface will be constructed on the upstream side of the spillway dam, at an
approximate elevation of 102.7 m (337 ft), as shown on Drawing 5 (Appendix C). The
temporary working surface will be constructed of clean, non-ore bearing rockfill (0 cm to 91.4 cm
(0” to 36”) in size), and will be approximately 3.7 m (12 ft) wide and will extend on both sides of
the Coffer Dam along the spillway dam.
A temporary Working Platform will be built on the downstream face of the spillway to allow
workers access to the downstream face. Debris fencing will be installed below the Working
Platform to capture falling debris.
Page 16 June 15, 2011