Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
Seeding is expected to discourage surface erosion and minimize noxious weed establishment
in advance of natural revegetation. Following the initial seeding during the spring following
dam breaching, subsequent localized spot seeding may be necessary to accomplish
performance criteria for revegetation. This work is expected to be completed by the fall of
the same year as initial seeding. Subsequent reseeding would be conducted as needed with
the goal of reaching the vegetative cover performance criteria within two years.
3.3.2 Management of Sediments and Woody Debris
Most of the estimated 24,000 cubic yards of woody debris would be washed downstream
along with the sediment during the initial movement of the sediment out of the reservoir.
Whatever remains behind in the sediments would be moved downstream by subsequent high
flow events. PacifiCorp proposes to allow this large woody debris to be released over time
along with the sediment within which it is contained. According to the USFWS Biological
Opinion (USFWS 2005), although the gradient and confined channel would preclude large
accumulations of large woody debris, some would collect, at least temporarily, below the
dam and may be beneficial in the creation of backwater zones and niches for juvenile fish
and the production of macroinvertebrates. However, intervention in this process would occur
if woody debris were to cause unstable slope conditions, as defined in the Bank Stabilization
Plan, Section 2.4 of the Project Description (PacifiCorp 2004), or if woody debris were found
to be adversely affecting fish passage. A decision to remove large woody debris would only
be made with the guidance of the fish management agencies.
When this condition exists, the preferred action would be to mechanically remove the woody
debris using equipment such as dozers and excavators and move the woody debris to a
storage area until it can be recycled or utilized for habitat enhancement. If the debris is in a
location that is unsafe to access with equipment, or if doing so would cause adverse
environmental impacts, the materials would be dislodged manually or with explosives and
allowed to mobilize downstream. Since this material would then be washed downstream
where it could potentially cause physical fish passage issues, the stream below the action area
would be assessed after the reservoir is drained. If the woody debris has accumulated or
positioned itself where it is creating a physical fish barrier, it would be remobilized or
removed at the downstream location.
3.3.3 Monitoring
Monitoring is proposed to demonstrate that performance criteria are met for several of the
management plans included in the Project Description (PacifiCorp 2004). For several of
these plans, monitoring would continue during the post-removal management period. The
proposed monitoring would include:
• Continuous turbidity monitoring at a minimum of three new water quality monitoring
sites using electronic data loggers
• Visual inspection of all fugitive dust sources and effectiveness of dust control
methods
• Monitoring revegetation and presence of noxious weeds
3-22