HomeMy WebLinkAbout12.29.20 BOS Correspondence - FW_ Project Operations Compliance Report submitted in FERC P-2107-000 by Pacific Gas and Electric Company,et al.
From:Schuman, Amy
To:Alpert, Bruce;Bennett, Robin;Clerk of the Board;Connelly, Bill;Cook, Holly;Kimmelshue, Tod;Lambert, Steve;Lucero, Debra;McCracken, Shari;Paulsen, Shaina;Pickett, Andy;Ring, Brian;Ritter,
Tami;Rodas,
Amalia;Sweeney, Kathleen;Teeter, Doug
Subject:BOS Correspondence - FW: Project Operations Compliance Report submitted in FERC P-2107-000 by Pacific Gas and Electric Company,et al.
Date:Tuesday, December 29, 2020 8:24:45 AM
Good morning,
Please see the email below from FERC.
Amy Schuman
Associate Clerk of the Board
Butte County Administration
25 County Center Drive, Suite 200, Oroville, CA 95965
O: 530.552.3300 |D: 530.552.3308 | F: 530.538.7120
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Sent: Tuesday, December 29, 2020 6:45 AM
Subject: Project Operations Compliance Report submitted in FERC P-2107-000 by Pacific Gas and Electric Company,et al.
.ATTENTION: This message originated from outside Butte County. Please exercise judgment before opening attachments, clicking on links, or replying..
On 12/29/2020, the following Filing was submitted to the Federal Energy Regulatory Commission (FERC), Washington D.C.:
Filer: Pacific Gas and Electric Company
PGE (as Agent)
Docket(s): P-2107-000
Lead Applicant: Pacific Gas and Electric Company
Filing Type: Project Operations Compliance Report
Description: Pacific Gas and Electric Company Submittal Regarding Poe Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control Assessment Plan - Request for Approval for the
Poe
Hydro Project under P-2107.
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December 28, 2020
Via Electronic Submittal
Ms. Kimberly D. Bose, Secretary
Federal Energy Regulatory Commission
888 First Street, NE
Washington, DC 20426
Subject: Poe Hydroelectric Project, FERC Project No. 2107-CA
Poe Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control
Assessment Plan Request for Approval
Dear Secretary Bose:
Attached for your review and approval is the Poe Bardees Bar Tunnel Spoil Pile Slope
Stability and Erosion Control Assessment (Assessment Report) (Enclosure 1) for Pacific
Gas and P-2107) (Project).
The Federal Energy Regulatory Commission (FERC) issued a new license for the Project
on December 17, 2018 (License). Subsection (a) of Article 401 of the License requires
PG&E to submit the Plan for FERC approval within one year from License issuance, after
the final Plan has been approved by the State Water Resources Control Board (SWRCB)
and by the Forest Supervisor of the Plumas National Forest (Forest Service). The spoil pile
is discussed in two license conditions, as follows:
Pile Revegetation: Within one year of license issuance, the Licensee shall file a
Bardees Bar Spoil Pile Revegetation Plan with the Deputy Director for review and
and any required modifications, with
pile near the North Fork Feather River.
Fore
Pile: Within one year of License issuance, Licensee shall file with the Commission a
Bardees Bar tunnel spoil revegetation plan, approved by the Forest Service for the
purpose of id
include an implementation schedule, site preparation and planting techniques, number
of planting sites, plant species to be established and follow-up measures to ensure
The plan shall be coordinated with the removal of the Bardees Bar Bridge
Ms. Kimberly D. Bose, Secretary
December 28, 2020
Page 2
The plan shall also include an evaluation of the stability of the undercut concrete
features located at the foot of the spoil pile as well as a schedule for stabilization or
removal of undercut concrete from the stream channel.
Following issuance of the Poe FERC license, PG&E consulted with the SWRCB, Forest
Service, and FERC to determine how best to address these conditions. It was agreed that
a phased approach would be most appropriate. This approach, described in extension of
time requests filed with both the SWRCB and Forest Service in late 2019, began with
PG&E preparing the attached Assessment Report. PG&E submitted an Extension of Time
(EOT) request after coming to a consensus with agencies that more time was needed to
develop a multi-year phased approach to stabilize the Bardees Bar Tunnel on December
12,2019. FERC approved the EOT request on January 8, 2020, extending the deadline to
submit the final Plan to December 31, 2020. The initial draft Assessment Report was
shared with agencies on May 26, 2020.
The Assessment Report discusses potential issues related to revegetation of the spoil pile,
including substrate coarseness and associated rapid drainage, exposure (heat and dry
conditions), and access to the steeper portions of the slope (making access to revegetate
the slopes extremely unsafe). However, there are areas of the spoils pile that currently
support plants, primarily yellow star thistle (an invasive weed) and grasses. This indicates
that at least early successional native species may be successfully planted on the site.
As noted in the Assessment Report, the concrete feature at the southern end of the spoil
pile was not constructed by PG&E and was put in place in 1997 by Union Pacific Railroad
(Geomatrix 2003). PG&E does not recommend additional toe protection in this area
because of the shallow bedrock outcrops visible near the river, and the satisfactory
coordinated with Union Pacific Railroad. Although Condition 15 also requires erosion
improvements at the top of the berm and on the north end will provide the appropriate
erosion control.
To improve stability and address existing invasive weeds on the tunnel spoil pile, PG&E
requests approval of the following course of action:
1. 2021 2022
Prepare and submit for approval a Bardees Bar Tunnel Spoil Stability Plan
(Stability Plan) that includes an analysis of site constraints, drainage control
engineering, and design drawings for drainage control measures on the top and
northern portion of the site. Site constraints include railroad property, electric
transmission corridor, topography, soils, etc. The Stability Plan will include a
post-construction slope stability monitoring plan with monitoring and reporting
every 5 years. Reporting and consultation with the Forest Service and SWRCB
will be completed after each monitoring event, with the draft report delivered to
Ms. Kimberly D. Bose, Secretary
December 28, 2020
Page 3
the Forest Service at the annual consultation meeting required under Condition
No. 3 and copied to SWRCB. After the meeting, the final report will be submitted
to FERC and a copy will be provided to both Forest Service and SWRCB.
Prepare and submit for approval a targeted (short-term) Revegetation Plan to be
implemented concurrently with the Stability Plan. The Revegetation Plan will
address management (control) of existing invasive weeds and include measures
to support growth of appropriate native plant species. The Revegetation Plan will
focus on the top, flat portion of the site, and will not encroach upon the railroad
property (100 feet either side of their tracks).
2. 2022 SWRCB, Forest Service, and FERC approval of Stability Plan and
Revegetation Plan.
3. 2023 construct drainage control measures as described in the Stability Plan, with
as-built report at end of construction; coincidentally implement the Revegetation
Plan.
Since the Assessment Report, including proposed next steps, was submitted to SWRCB
and Forest Staff on May 26, 2020 for review, PG&E has consulted with agency staff on
August 11 and October 13, 2020 with calls to confirm acceptance of the final Assessment
Report and to continue incorporating staff suggestions on this approval request letter. On
October 22, 2020, PG&E submitted the Plan for formal approval from the SWRCB and the
Forest Service. The Forest Service approval letter, dated December 16, 2020, is included
in Enclosure 2, and the SWRCB conditional approval letter, dated December 21, 2020, is
included in Enclosure 3. The SWRCB also e-filed their approval letter with FERC.
Senior License
Coordinator, Matthew Joseph, at 415-264-5244 or at matthew.joseph@pge.com.
Sincerely,
Matthew Joseph
(for) Elisabeth Rossi
Supervisor, Hydro Licensing
Enclosures:
1 Poe Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control Assessment
2 Forest Service approval letter dated December 16, 2020, , dated
October 22, 2020, requesting approval
3 SWRCB conditional approval letter dated December 21, 2020.
Enclosure 1
Poe Bardees Bar Tunnel Spoil Slope Stability
and Erosion Control Assessment
Memorandum
Prepared For:Steve Bauman,Sr. Power GenerationLicense Project Manager
Prepared By:Robert McManus, GE,Geotechnical Engineer
Emmons McKinney, GIT, Geosciences Intern
Reviewed By:Emily Steen,GE, Geotechnical Engineer
Copies:
Date:May 26, 2020
Subject:Poe Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control
Assessment
Note: This document contains links to figures.
To return to the text after jumping to the figure press the Alt+LeftArrow keys
1 Introduction
As requested, the PG&E Geosciences Department (Geosciences) has prepared this report summarizing
our investigation of erosion and slope stability of PG&E’s Bardees Bar spoil pile of the Poe hydroelectric
project. Our investigation includes a site visit with helicopter overflight, review of historic photographs
and images, and analysis of recent LiDAR data, including topographic information and flow analysis. We
have several recommendations for improvement of drainage to reduce erosion during heavy
precipitation events.
2 Executive Summary
The Bardees Bar tunnel spoil pile was constructed as part of the Poe hydroelectric project (FERC No.
2107) in the mid-1950s. The location is in Butte County in northern California on the east bank of the
North Fork Feather River (NFFR), about two miles south of the town of Pulga.
There are three prisms of fill adjacent to the NFFR south of the Bardees Bar construction bridge: 1) Fill
from the upper and lower side hill cuts for an abandoned access road, 2) Fill from the Union Pacific
Railroad track, and 3) tunnel spoil from the construction of part of the Poe project water tunnel and all
of Adit 1. The first two fill prisms pre-date the Poe project and were not constructed by PG&E. Thus, this
assessment is limited to the item (3). The existing concrete feature on the southern end of the spoil pile
Page 1 of 44
Memorandum
1
was not constructed by PG&E and evidently was placed in 1997 by Union Pacific Railroad. Because of
the shallow bedrock outcrops visible near the river in this area, and the satisfactory performance of the
fill slope above the concrete, we do not recommend additional toe protection in this area.
3
The tunnel spoil from the Poe project has a volume of about 400,000 yds. The fill can be divided into
two regimes, 1) a moderately sloped top bench that is triangular in plan, about 800 feet long, and 100
O
feet wide at the apex; and 2) the western slope that drops down at a uniform angle of about 38 to
canyon bottom, about 150 vertical feet below the edge of the bench. Most of tunnel spoil is separated
from the low river channel by a boulder bar which has a width of up to 120 feet adjacent to the fill.
Erosion of the Poe project tunnel spoil prism can be attributed to two major causes – overland flow from
seasonal rainfall and slow melt, and toe erosion by flooding of the NFFR. The prism is well situated
because most water flowing overland down the canyon walls is intercepted by the railroad drainage
ditch and diverted south away from the site. The only natural drainage from the canyon flows down a
gully that passes over the railroad tunnel and then discharges onto the fill bench. Otherwise, only rain
that falls directly on the fill prism contributes to erosion.
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The west slope has an average angle of 38 which is sufficiently stable for well-graded angular rocky fill.
There is no evidence of deep slope failures in the fill prism and they are not expected to occur in the
future if this slope angle is maintained.
The surface of much the west slope is subject to slow raveling of gravel to boulder-sized rock. This
makes it very hard for vegetation to survive because of the surficial movement coupled with rapid
drainage and hot summertime sun exposure. Despite the lack of vegetation, image analysis shows very
little erosion of the slope since 1993, and there is little eroded slope material apparent on the boulder
bar below where differences in color and angularity make identification of rock source possible.
The second source of erosion and localized slope sloughing and raveling is toe cutting by the NFFR
during significant floods. Downcutting of the river in this area appears to be curtailed by bands of
erosion-resistant bedrock in the riverbed. These bands can be identified by polished bedrock outcrops in
the river – little changed since 1955, and the elevation drops and rapids that occur near the downstream
edge of the bands. Because of the favorable conditions that have limited toe erosion of the northern
portion of tunnel fill prism, we do not recommend additional toe protection at this time.
Although gully erosion of the west slope has been limited by the coarse nature of the tunnel spoil and
very limited basin in which runoff water can collect, several potential improvements were identified as
shown on Figure 40. The 1997 drainage swale and berm which have helped to control flow over the
edge of the top bench should be deepened on the south end where there is evidence of water going
over the berm at several locations, and lengthened to keep bench runoff from the entire west slope. At
the north end of the fill, collected runoff could be directed to the river over several alternative paths.
1
Geomatrix, 2003
Page 2 of 44
Memorandum
The final decision among these alternatives should be based on constructability and environmental
review.
3 Background
The Bardees Bar tunnel spoil pile was constructed as part of the Poe hydroelectric project (FERC No.
2107) in the mid-1950s \[Ref 1\]. The location is in Butte County in northern California on the east bank of
the North Fork Feather River (NFFR), about two miles south of the town of Pulga. See Figure 1. The NFFR
cuts through the Sierra Nevada mountains within a steep v-shaped canyon several thousand feet deep.
The Poe Project takes water from the river at Poe Dam and transports it through a water tunnel within
the east wall of the canyon to the Poe powerhouse. The water tunnel is about 24-feet in diameter and
6.4 miles long See Figure 2.
Excavation of the water tunnel started in 1955 and continued until February 1957. Construction of the
project continued into 1958 \[Ref 2\]. The tunnel was driven from six headings simultaneously – from the
intake and powerhouse portals, and from two headings each at two mid-length adits (Adits 1 and 2).
Rock encountered in the tunnel and placed in the spoil piles was about 60 percent serpentine, 35
percent undifferentiated metamorphic rocks, and 5 percent meta-gabbro. Less than 1 percent of
granodiorite, limestone, and amphibolite were also encountered \[Ref 2\]. Much of the rock was closely
jointed, a factor which, along with rock type and blasting method, influences the size distribution of
particles ultimately deposited in the spoil piles.
Rock from the tunnel excavation (also called “tunnel muck”) at Bardees Bar was blasted from the tunnel,
transported out of the tunnel through an access adit (Adit 1), and deposited in a broad swale above a
wide section of the NFFR canyon. The tunnel spoil deposited at Adit 1 came from the tunnel from the
halfway point between the Poe power dam intake and Adit 1 in the upstream direction, a distance of
about 8,500 feet, and the halfway point between Adit 1 and Adit 2, a distance of about 6,500 feet. The
spoil from the Adit 1 excavation (about 900 feet long) was also deposited at Bardees Bar. The volume of
3
tunnel spoil at Bardees Bar from the Poe project is estimated to be 400,000 yds, based on the
theoretical volume of the tunnel and adit, including factors for tunnel overbreak and bulking when going
from in-place rock to granular fill with void spaces. A PG&E drawing from the 1950s indicates a shoulder
was graded along the outer edge of the upper fill at the top of the steeper slope \[Ref 3\].
Figure 3 shows key aspects of the site. The NFFR runs generally north to south in this area, but just north
of the site it makes three abrupt turns around an erosion-resistant ridge of rock that forms a peninsula
(Bardees Point). On the south side of this resistant ridge, the canyon bottom is broader and wider, with
the river channel occupying the west side of the wider segment. East of the river channel is a boulder
bar about 800 feet long and up to 175 feet wide. At the south end of the broader reach, the canyon
walls narrow, and the river is forced back toward the east canyon wall, where the channel makes a
sweeping turn to the southwest past another more erosion-resistant rock slope.
The top of the tunnel spoil fill is a bench that slopes moderately to the west toward the river. The bench
top is roughly triangular in plan, about 800 feet long, and 100 feet wide at the apex. The western face of
O
the fill prism drops at an angle of about 38 to the boulder bar adjacent to the river, a vertical height of
Page 3 of 44
Memorandum
about 150 feet. The Union Pacific railroad track runs along the east edge of the spoil prism. The railroad,
which pre-dates the Poe project, excavated its own tunnel (Tunnel 9) through the resistant ridge of rock
forming the peninsula described above. Some of the spoil from this tunnel was deposited as fill to the
south of the Poe spoil site. Railroad fill underlies approximately the southern half of the Poe generated
spoil pile.
The “Utah Construction Road” was excavated into the south wall of the resistant ridge to support
railroad construction in the early 1900s. Rock from this excavation was placed on the slope adjacent to
the road, to the north of the eventual site of the Poe spoil pile. An improved bridge for this road which
was built in the 1950s spans the NFFR at the west end of the resistant rock ridge. This bridge has not
been maintained and is no longer passable. Therefore, the spoil pile is not accessible by road.
4 Historic Images of the Bardees Bar Spoil Pile
Figures 4 through 6 show the Bardees Bar site in 1954 and 1955, before the Poe spoil pile had been
placed. In Figure 4, fill from the railroad and access road that pre-date the Poe Project is visible. Figure 5
shows the boulder bar with river channels on both sides. Figure 6 shows the spoil pile site from farther
north than the previous figures. We were able to find the turnout on Highway 70 from which the 1955
photo was taken to closely recreate the view.
On Figure 7 the 1955 photo from Figure 6 is superimposed on the same view from 2019. Many common
features can be seen in both views, including the bridge, transmission tower bases, edge of road, and
rock outcrops (red outlines). The common features were used to align the historic view with the recent
one. The large number of rock outcrops or large boulders visible in the river channel in both view shows
that the riverbed has not had significant downcutting or changes in channel width between 1955 and
2019, a period of 64 years. There were several significant floods during this period, including events in
1955 (after the photos were taken), 1986, and 1997 that caused severe erosion of highway and railroad
fills adjacent to the river.
The shoreline and lower access road from the 1955 image are outlined in yellow. In Figure 8 these
outlines show that the west shoreline of the boulder bar has not changed. The east channel around the
bar no longer contains water at low river stage. The size of the largest alluvium particles (boulders with
infilling of cobles, gravel, and sand) indicates they would have to have been deposited by significant
floods. Except for the southern end of the filled channel, the toe of the spoil pile lies to the east of the
boulder bar. The lower access road, also outlined in yellow, is buried by the spoil fill to the north of the
bar. To the south, the road appears to have been washed away where it was adjacent to the outside
sweeping bend in the river.
5 Historic Google Earth Images
Historic images available on Google Earth allow us to see changes in the spoil pile during the period
1993 to 2018. See Figures 9 to 14. Figure 9 shows the area in 1993. Some gullying of the steep west
slope of the spoil pile is apparent, as well as shallow sloughing of the fill below the railroad track at the
south end of the site.
Page 4 of 44
Memorandum
The next photo from 2005, Figure 10, is after the large 1997 flood. Additional sloughing of the railroad
fill has occurred, and the railroad has installed concrete filled riprap as erosion protection below the
sloughed area. Gullying of the west slope of the spoil pile does not appear to be different from the 1993
image, and the location of the toe of the slope north of the concreted riprap repair appears to be the
same, with vegetation intact. It is apparent in the 2005 image that grading on the top of the bench had
been conducted. This grading improved a shallow swale and berm that directs water to the north along
the edge of the bench. The grading ends at the top of a shallow swale near the north end of the bench
where water is directed into the swale and then down the steep western slope. The access road bridge
over the railroad track to Adit 1 had also been removed by 2005.
The 2007 image (Figure 11) more clearly shows the sloughed slope below the railroad and the erosion
protection installed after the 1997 flood. A near horizontal scour line at the toe of the west slope, likely
from the 1997 flood, is more clearly visible in this higher resolution image. Below the scour line it
appears that several feet of material have been eroded leaving a small oversteepened scarp at the top.
On the 2012 image (Figure 12), sediment is visible originating in the area of the railroad track, which
then flows over the spoil pile to the swale near the western edge of the bench, then north along the
swale. It does not appear that any of the sediment made it to the swale and down the steep western
slope of the spoil pile. This appears to be a one-time event as fresh sediment is not visible in any of the
other historic Google Earth images between 1993 and 2018.
Figure 13 image was taken in 2017. The condition of the spoil pile is similar to that seen in the 2012
image except for headward erosion that is visible where gullies in the west slope intersect the 1997
flood scour line. It appears that this erosion is caused by water running down the gullies rather than
undermining of the toe by the river.
Figure 14 from 2018 shows very little change from the previous year, except the sun angle is lower
which creates shadows to more clearly evaluate the condition of the gullies in the west slope. On Figure
15, the 2018 image can be compared with the image from 2008, which has a similar low sun angle.
Except for the headward erosion in the three gullies first noted in the 2017 image, the condition of the
gullies is virtually unchanged over that ten-year period.
6 Site Observations
Figures 16 through 34 are from our on-site inspection August 5, 2019. Access to the site was from a
helicopter flying out of PG&E’s hydro facility at Rodgers Flat. Figures 16 and 17are taken from the
helicopter. The top bench of the fill is almost completely covered with grass and other low vegetation.
Trees and brush on the bench are sparse but are establishing primarily in shallow swales and along the
berm on the west edge. The western slope is vegetated with grass over most of the southern one third,
while the middle half to the north is almost devoid of vegetation. The northernmost segment of the
west slope is vegetated with grass. The scour line near the toe of the slope and subsequent headward
erosion is apparent, as is the concrete riprap below the railroad fill at the south end of the site. See
Figure 17.
Page 5 of 44
Memorandum
Figure 18 shows the railroad track and tunnel, as well as the bridge abutments from the abandoned
access road to Adit 1. Note the dried sediment in the shallow ditch west of the railroad track which
indicates overland flow coming south along the track or underneath it through the open graded gravel
ballast.
Figure 19 looks north along the west edge of the bench and the drainage swale and berm. In the middle
distance is the area where water from the railroad track area comes into the swale from the east. The
Figure 20. The berm is low
tree seen on the berm in the upper left of Figure 19 is shown in closeup on
here and water in the swale flows over the side causing erosion and gullying on the west slope.
Figure 21 is an overall view of the bench showing nearly complete coverage by grasses and thistles, with
some brush and trees growing near the center of the bench.
Figures 22 and 23show the broad swale in the west slope where most of the drainage from the bench is
directed to flow over the edge. There is a smaller incised channel within the broad swale. This channel is
armored with cobble-sized angular rock.
Figures 24 and 25show the upper access road between the NFFR bridge and the Adit 1 bridge location.
There are remnants of paving on the road surface. The road is located on a side slope cut and fill in
erosion resistant rock. The road is in very good condition with no gullying from overland flow.
Vegetation is well established on the road.
Figures 26 and 27show the lower access road. Similar to the upper road, the condition is good, with no
gullying or erosion of the road surface, The cut slope above the road has had some minor rock falls. The
road is well covered with brush but the brush appears to have been burned recently. Where the road
enters the boulder bar there has been scour from past floods to a height several feet above the bar. The
road material is well compacted and cohesive and has been resistant to scour.
Figure 28 is a view upstream of the boulder bar between the north end of the spoil pile and the river
channel. The lower access road comes down the slope in the middle right of the image. The top of the
boulder bar is about 15 feet above the river channel at this point.
Figures 29 and 30show the northern end of the spoil pile slope from below. The slope here is composed
of raveling loose cobble- to boulder-sized angular rock with a matrix of sand and gravel. Vegetation is
not able to grow on this raveling and well drained material. A flood scour line is not visible here.
Rounded gray boulders in the bar are river deposits, while the more angular brown boulders that have
rolled out a small distance from the slope are derived from tunnel spoil. The toe of the slope is well
armored with large boulders in this area.
Figure 31 shows the upstream end of the concreted riprap placed by the others following the 1997
flood. There appears to be an older generation of cementitious material below the grayer concreted
riprap. The river channel narrows here, and the boulder bar is no longer present at the toe of the slope.
Note the steeper scarp at the upper edge of the image with raveling rock below. This is the scour line
from significant past floods. Figure 32 is taken from the same location but looking in the upstream
Page 6 of 44
Memorandum
direction. There is a remnant of concrete paving on the old access road between the slope and the river,
which affords limited erosion protection. The nature of the spoil pile material can be seen in this image.
In places it consists of loose angular cobbles and boulders with gravel. In other places there is a cohesive
clayey matrix of angular sand, gravel, and cobbles. This matrix material is very hard and strong when
dry, and likely somewhat weaker when wet. The cohesive nature of this material has allowed it to
maintain much of the steep scour line scarp from the 1997 flood for many decades.
Figure 33 shows two generations of cementitious armoring at the south end of the fill below the
railroad. The lower layer is believed to date from the 1950s or earlier, while the upper layer of concreted
riprap was placed following the 1997 flood. The lower layer has been undermined by river flows to
unknown depth, but large rocks are visible in the water below the concrete.
Figure 34 is a photo taken from about the same location as Figure 33. It shows the river channel to the
west of the spoil pile toe (concreted riprap armoring seen on the right edge of the image). There are
numerous outcrops of erosion resistant bedrock in the river channel here, visible in the foreground, mid-
channel, and far bank. This rock limits downcutting of the river channel adjacent to the Bardees Bar spoil
pile. Note the boulder bar in the distance.
Figure 35 shows the lower end of the only natural gulley that crosses over the railroad and drains onto
the spoil pile bench. Water coming down this gully flows toward the broad swale in the west slope
visible in Figures 22 and 23. Some water may also flow down the old access road to the left in this
image.
7 LiDAR Analysis
Aerial LiDAR data was obtained at the site in May 2019. Analysis of the LiDAR data provides a better
understanding of the slopes on the site, areas of erosion, and drainage patterns.
On Figure 36 a photographic image has been overlaid with the five-foot contours from the LiDAR survey.
The NFFR drops about 25 feet between the Bardees Bar bridge and the south end of the railroad fill.
About 15 feet of the drop occurs at the waterfall/rapids near the north end of the spoil pile. The boulder
bar adjacent to the spoil pile is close in elevation to the low river channel at its upstream end near the
erosion resistant ridge and then drops about ten feet in elevation over its length. At its downstream
end, adjacent to about the midpoint of the spoil pile, the top of the bar is about 15 feet above the river
channel. The concreted riprap installed by the railroad at the downstream end of the site rises about 15
vertical feet above the river channel.
The horizontal spacing of the contours on the west slope is very consistent, indicating a uniform slope.
Contours are slightly closer together in the area below the 1997 scour line at the toe of the slope,
indicating slight steeping. The bench top is about 150 feet above the bottom of the canyon. The vertical
height of the west slope is greatest on the downstream end of the spoil pile and decreases to the north.
Page 7 of 44
Memorandum
The bench top slopes moderately steeply toward the river and slopes gently in the upstream direction
(north). The drainage swale graded in 1997 near the outer edge of the bench can be seen in the
contours. At the south end of the drainage swale the contours are not curved very sharply, indicating
the relief of the swale is small. This corresponds with our observations at the site of runoff going over
the edge of the bench at the south end of the swale.
In Figure 37 the image has been shaded according to local slope steepness. On the bench top the slopes
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range from 0 to 20, while the west slope ranges from 30 to over 50. Steeper areas, indicated by
brown shading, are found near the 1997 scour line at the toe of the slope and in the walls of some of the
erosion swales.
Figure 38 shows the location of three profiles based on the LiDAR topography. The profiles are oriented
roughly parallel with the fall line of the slopes to show maximum steepness. Section A-A’ is drawn
O
through the bottom of the most prominent swale. The swale has an average slope angle of 37. The
slope is slightly steeper near the bottom, starting at about 50 feet above the river. Profile B-B’ is located
O
on the slope next to the swale in Profile A-A’. The average slope angle is 38. The average bench slope
O
along this profile is about 12. Profile C-C’ is drawn at the ridge next to the swale where most of the
bench runoff goes over the west slope. The upper end of this profile also lines up with the natural ravine
O
that discharges onto the apex of the spoil pile. The average angle of the west slope is 37.5, the bench
OO
slope is about 13, and the natural ravine slope is about 38along this profile.
Figure 39 shows the accumulated runoff at each LiDAR pixel. This makes it easier to see where flow
accumulates on the slopes of the spoil pile. Although the spoil pile is located near the bottom of a high
canyon wall, most of the runoff coming off the canyon is intercepted by the railroad track. At the
railroad track, flow is diverted in a drainage ditch to the south where it crosses under the track in a
culvert and then flows down a rocky slope to the river. Therefore, the runoff that drains from the spoil
pile is limited almost entirely to the rain or snow melt that falls directly onto the bench and west slope.
The only natural ravine in the canyon wall discharging onto the spoil pile bench is the ravine over the
top of the railroad tunnel that ends near the apex of the tunnel fill. Some of this water coming down this
ravine flows toward the gully in the west slope where the bench top runoff is also directed, and some
flows down the old access road. It is possible some of the water accumulating in this ravine flows below
the surface of the fill in the natural swale that was buried by the tunnel spoil.
The west edge shoulder fill and swale directs flow to the north along about ¾ of the bench length before
flowing over the west slope at the ravine shown in Figures 22 and 23. North of this ravine there is no
edge swale and runoff flows down the west slope in several other ravines.
8 Discussion
There are three prisms of fill adjacent to the NFFR south of the Bardees Bar construction bridge: 1) Fill
from the upper and lower side hill cuts for an abandoned access road, 2) Fill from the Union Pacific
Railroad track, and 3) Tunnel spoil from the construction of part of the Poe Project water tunnel and all
of Adit 1. The first two fill prisms pre-date the Poe project and were not constructed by PG&E. As such
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they were not included in this investigation. The material in the two pre-Poe Project fills derive mainly
from the erosion-resistant ridge north of the fill area. These fills are composed of relatively large-sized,
good quality rock. Rock from the Poe tunnel was generally of lower quality than the rocky ridge,
consisting of 60 percent serpentine, 35 percent undifferentiated metamorphic rocks, and 5 percent
meta-gabbro closely jointed in place. The Poe tunnel was built using the drill and blast method, further
breaking down the rock into smaller pieces. Therefore, the spoil rock from the Poe tunnel is of smaller
average size than the adjacent fills and contains cohesive (clayey) fine matrix in areas.
The Poe tunnel and the spoil pile were constructed in the mid-1950s. Tunnel spoil was placed at an area
where the steep-sided canyon has a relatively wide bottom. The site is downstream of a rocky ridge
which forces the river channel to the west and then back east through a series of tight curves before
returning to its predominant north/south direction. The insides of these turns contain relatively flat bars
consisting of sub-rounded sediment up to the size of large boulders. The tunnel spoil was placed in a
broad swale above one of these large boulder bars. A small amount of Poe fill appears to have been
placed on top of the railroad fill on the downstream end of the site.
The size of the boulders in the bars indicate these materials are transported only during extremely large
floods – much larger than any observed historically. Comparison of photos from 1955 and 2019 show
that many large rocks in the river (likely outcrops of bedrock rather than loose alluvium) have not
changed significantly over this time period of 64 years that includes at least three large floods in 1955,
1986 and 1997. Additionally, the shoreline of the boulder bar next to the main channel of the river has
not changed over this time.
A May 2019 LiDAR survey shows the river channel drops about 25 feet between Bardees Bar Bridge and
the downstream end of the railroad fill. About 15 feet of this drop occurs in one rapid/waterfall adjacent
to the boulder bar at the north end of the spoil pile. The outsides of the turns in the river appear to be
areas of ongoing bank erosion. At the outside bend below the railroad fill, comparison of the 1955 and
2019 photos show the shoreline has moved to the east. Undercutting of the railroad fill during the 1997
flood prompted the railroad to place concreted riprap at the toe of the slope over a distance of about
300 feet. Erosion of the toes of natural slopes north of the Bardees Bar bridge has created rocky raveling
slopes that are similar in appearance to the west slope of the spoil pile. See for example the slope below
the rocky ridge northeast of this bridge (Figure 16).
Downcutting of the riverbed adjacent to the spoil pile appears to be controlled by a series of erosion-
resistant bands of bedrock. Downstream of each of these bands, the river drops in elevation and
whitewater is evident on historic satellite images when flow conditions are right. One of these bands
crosses the river below the Bardees Bar bridge. This band is an extension of the rock ridge that diverts
the river course in a series of sharp bends. Another resistant band crosses at about the mid-length of the
fill, under the boulder bar. Just downstream of this band the river drops 15 feet. Comparison of historic
and recent photos shows large rocks mid-river between these two bedrock bands have not materially
changed since 1955. The third band is at the downstream end of the railroad fill. Numerous polished
outcrops can be seen on the east and west banks and mid-river here and there are steep cliffs in the
east canyon wall showing the higher quality of the rock.
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3
The tunnel spoil from the Poe project has a volume of about 400,000 yds, based on an estimate of the
volume of the tunnel excavated from two headings at Adit 1 and the volume of the adit itself. The
surface of the fill can be divided into two regimes, 1) a moderately sloped top bench that is triangular in
plan, about 800 feet long, and 100 feet wide at the apex; and 2) the western slope that drops down at a
O
uniform angle of about 38 to canyon bottom, about 150 vertical feet below the edge of the bench.
Most of tunnel spoil is separated from the low river channel by the boulder bar which has a width of up
to 120 feet adjacent to the fill.
A series of historic images from Google Earth allows analysis of changes in the spoil pile between 1993
and 2018. Following the 1997 flood, the Union Pacific Railroad placed concreted riprap at the toe of the
railroad fill to protect the slope below the track. Some surficial slumping of this fill may have occurred
during the 1997 flood, and replacement of some this fill may have occurred as part of the railroad repair
2
work. A horizontal scour line can be seen at the toe of the Poe fill following the 1997 flood. Up to
several feet of material may have been eroded by the flood below this line, resulting in a scarp at the
top that is visible as a shadow line in the Google Earth images. This scour line, starting about 15 vertical
feet above the boulder bar, is still visible today. This scour line remained virtually unchanged until the
2017 image, when headward erosion is visible at the lower end of three of the gullies where they
intercept the scour line scarp. It is likely this new erosion was caused by water running down the face of
the west slope, rather than renewed cutting of the toe. The scour line is not visible at the toe of the
northern third of the fill. This is likely because the canyon bottom is much wider there, resulting in lower
water velocities during floods. These low flood velocities are shown by sand deposited between the
boulders in the boulder bar. Some raveling of the loose slope material on the northern end of the fill
slope may have obscured this line. There is no apparent erosion of the slope toe just upstream of the
concreted riprap.
Almost all the tunnel spoil is separated from the low river channel by the boulder bar. At the south end
the boulder bar is 15 feet above the river. Therefore, river water does not flow against the toe of the fill
except during extreme floods such as those in 1986 and 1997.
The top of the fill prism is moderately sloped to the west at an average angle of about 13 degrees.
Additionally, a graded swale along the west edge off the bench slopes gently to the north where runoff
water is directed over the edge of the fill into a broad swale with a small incised channel. At the south
end of the fill, we noticed the drainage swale was relatively shallow and some water flow is going over
the edge into gullies on the west slope.
The northern edge of the bench top does not have an edge swale and runoff water there flows over the
edge into established ravines.
The bench top is almost completely covered with vegetation, primarily grass and thistles. Some brush
and trees are also established, primarily near the center of the bench and along the western edge. These
2
The scour line may have been present in 1993 but the image is not sharp enough to detect it.
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locations may be more favorable for this type of vegetation because of the availability of more water
during the winter and spring.
The west slope of the fill prism is about 800 feet long and about 150 vertical feet high. The southern
quarter of this slope is either railroad fill or a thin veneer of Poe tunnel fill overlying the railroad fill.
There are numerous shallow gullies and ravines on the face of the slope. These appear to have been
established prior to 1997 when the grading work improved the drainage swale to keep bench runoff
from flowing over the edge. There is little difference in appearance between these gullies in 1993
images and the present. Google Earth images from 2008 and 2018 with similar low sun angles show
virtually no difference in these gullies over that time period.
O
There is no evidence of deep-seated failures of this slope, such as ground cracks or slumped areas. 38 is
a reasonable slope angle for well graded angular rock fill and deep slope failures are not expected in the
future as long as this slope angle is maintained.
The face of the slope is poorly vegetated. The south 300 feet of railroad fill is about two-thirds covered
with grass. The central part of the slope is sparsely vegetated, while the northern quarter, north of the
drainage ravine, is almost totally covered with grass and other low vegetation. The top 25 feet of the
slope is well vegetated over the entire length of the fill prism. On the southern segment this may be
related to the grading of the edge swale that occurred in 1997. Trees and brush are also present on the
southern edge.
The lack of vegetation in some areas of the west slope appears to be controlled by the type of material
on the surface. The less vegetated slope appears to have large particle sizes and a lack of fines. These
materials may slowly ravel, which destroys any vegetation that begins to grow. These materials are also
very well drained, which means water is not present for plants, especially during the late spring and hot
summer. The lack of water is coupled with a hot southwest sun exposure to create unfavorable
conditions for plant growth.
The lack of vegetation does not appear to result in much material being deposited into the river channel
below the slope. The tunnel spoil has a different color and angularity from the river deposits in the
boulder bar. There is very little tunnel spoil visible on the top of the bar, except at the base of the
drainage swale, where the rock size is very large, and particles are unlikely to be eroded even during
very large floods. The gullies in the west slope are eroding very slowly over time. There is little change in
the appearance of these gullies since 1993, except for recent headward erosion of three of the gullies
where they intercept the low scarp created by the 1997 flood.
9 Conclusionsand Recommendations
Erosion of the Poe project tunnel spoil prism can be attributed to two major causes – overland flow from
seasonal rainfall and snow melt, and toe erosion by flooding of the NFFR. The prism is well situated
because most water flowing overland down the canyon walls is intercepted by the railroad track
drainage ditch and diverted south away from the site. The only natural drainage from the canyon wall
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flows down a gully that passes over the railroad tunnel and then discharges onto the fill bench.
Otherwise, only rain that falls directly on the fill prism contributes to erosion.
The fill prism is divided into two regimes – the top bench and the west slope. The top bench is
moderately sloped at an average angle of about 13 degrees. The bench is almost completely covered
with vegetation with no areas of active erosion. A shoulder berm and drainage swale establish in the
mid-1950s at the end of construction and possibly re-graded in 1997 at the western edge of the bench
directs water to a broad swale near the northern end of the fill. The edge swale appears to have been
successful in keeping water off the slope except at the southern end where it is shallow and there is
some evidence of water going over the edge into ravines.
O
The west slope has an average angle of 38 which is adequate for well-graded angular rocky fill. There is
no evidence of deep slope failures in the fill prism and they are not expected to occur in the future if this
slope angle is maintained. The surface of much the west slope is subject to slow raveling of gravel to
boulder-sized rock. This makes it very hard for vegetation to survive because of the surficial movement
coupled with rapid drainage and hot summertime sun exposure. Despite the lack of vegetation, image
analysis shows very little erosion of the slope since 1993, and there is little slope material apparent on
the boulder bar below where differences in color and angularity make identification of rock source
possible.
The second source of erosion is toe cutting by the NFFR during significant floods. Downcutting of the
river in this area appears to be curtailed by bands of erosion-resistant bedrock in the riverbed. These
bands can be identified by polished bedrock outcrops in the river – little changed since 1955, and by the
elevation drops and rapids that occur near the downstream edge of these bands.
The river makes several sharp bends in the area of the spoil fill, with boulder bars deposited on the
insides of these curves and apparent bank erosion occurring on the outside of the curves. Erosion of the
bank below and downstream of the railroad fill is apparent in comparing a 1955 photo with a 2019
photo from the same location. Much of this bank erosion likely occurred during the three large floods of
1955, 1986, and 1997. The 1997 flood prompted the railroad to armor the toe with concreted riprap.
Although the bottom of this concreted riprap has been undermined, the proximity of nearby bedrock
outcrops suggests further downcutting will be slow and limited.
Toe scour of the northern portion of the west fill slope has been limited to a volume a few feet deep and
about 25 feet high up the slope. Even this limited erosion required the extreme flows of three large
NFFR floods since 1955. The oversteepened scarp at the top of the toe erosion has not progressed very
far up the slope except where headward erosion occurred at three gullies, first noted in the 2017 Google
Earth image. Scour of the northern 500 feet of the fill prism is expected to be limited because the
canyon bottom is relatively wide and straight, and the toe is separated from the main channel by a
boulder bar up to 120 feet wide with a surface up to 15 feet above the low river channel. Where the
slope toe abuts the concreted riprap, there is no evidence of ongoing erosion of the toe above the
riprap.
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Because of the favorable conditions noted above that have limited toe erosion of the northern portion
of tunnel fill prism, we do not recommend additional toe protection at this time. Additionally, because
of the shallow bedrock outcrops visible at the southern end, and the satisfactory performance of the
southern end of the tunnel spoil fill slope, we do not recommend additional toe protection in this area
upstream of the concreted riprap.
Although gully erosion of the west slope has been limited by the coarse size of the tunnel spoil and very
limited basin in which runoff water can collect, several potential improvements were identified as
shown on Figure 40. The shoulder berm and drainage swale which has helped to control flow over the
edge of the top bench should be deepened on the south end of the fill where there is evidence of water
going over the berm at several locations. Deepening the swale will also allow it to continue to function if
there is sedimentation as seen on the 2012 Google Earth image. Currently this swale ends several
hundred feet from the north end of the bench., From this point there are four alternatives that will
require additional engineering analysis to make the final recommendation:
1.First, the water could be diverted down the west slope, most likely in the swale between the
tunnel fill and the access road fill (Option (1) on the figure). If the rock on the surface is large
enough, water could be discharged directly onto the slope. If the swale rock could be subject to
erosion from the concentrated flow, a pipe and energy dissipater could be used.
2.The second alternatives is to discharge the water onto the old access road. The road surface is
currently in good condition, as it is composed of rock cut or rock fill. The LiDAR contours show
that that it would be possible to gravity flow water in this swale further to the north. An edge
berm might be required to keep storm runoff on the road. Once on the upper road, water would
be diverted onto the lower access road and then onto the boulder bar in the most favorable
location, possibly over the rock cut in the erosion resistant ridge (Option (2) on the figure).
3.The third alternatives would be to divert the water from the upper access road to the river over
the natural rock cliff that currently forms the abutment for the abandoned bridge (Option (3) on
the figure).
4.Status quo, which is to leave the site as-is.
Final decision among these alternatives should be based on constructability and environmental review.
The water that comes down the natural ravine to the apex of the fill bench currently flows out onto the
slope, and there is no evidence of localized erosion at this point. This water could be diverted down the
access road as well, however, this would deprive vegetation on the bench top from this water and is
therefore not recommended.
10References
\[Ref 1\] PG&E History of Poe Tunnel Construction from April 14, 1955 to July 31, 1958
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\[Ref 2\] Lydon, Phillip; “Geologic Section and Petrography Along Poe Tunnel, Butte County California”;
California Division of Mines Special Report 61; 1959
\[Ref 3\] PG&E drawing 421283, Cleanup required by W.P.R.R vicinity of Adit 1 Poe Tunnel, 1958
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Figure 1 – Location map for Poe Bardees Bar Tunnel Spoil Pile
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Figure 2 – Site map for Poe Bardees Bar Tunnel Spoil Pile.
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Figure 3 – Project features for Poe Bardees Bar Tunnel Spoil Pile.
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Figure 4 –1954 photo showing the future location of the Bardees Bar spoil pile in the center of the image. Note fill from
railroad grade and existing access road cut into the rocky ridge on the left
Figure 5 – Another 1954 photo of the future spoil pile site, looking down river.
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Figure 6 – A 1955 photo showing the spoil pile site. By this time the improved bridge had been built across the river to access
Adit 1 for the Poe hydroelectric tunnel. Compared to Figure 5, most of the trees have been removed from the slope that will
receive tunnel muck.
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Figure 7 – The 1955 photo in Figure 6 superimposed on the same view from 2019. Many common features can be seen in
both views, including the bridge, transmission tower frames, edge of road, and rock outcrops (red outlines). The shoreline
and road from 1955 are outlined in yellow.
Figure 8 – This is the 2019 view. The west edge of boulder bar has not changed, although the channel on the east side of the
bar is now dry, this appears to be from natural sedimentation rather than fill from the Poe spoil pile, the toe of which is
primarily to the east of the old shore line.
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Figure 9 – Google Earth image of Bardees Bar spoil pile taken 1993-07-31. Note indications of slope surface sloughing below
railroad grade (outlined in yellow).
Figure 10 – Google Earth image of Bardees Barspoil pile taken 2005-06-11. This is about nine and one half years following the
large flood of 1996-7 flood. Concreted riprap has been placed at the toe of the railroad grade fill (right arrow).
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Figure 11 - Google Earth image of Bardees Bar spoil pile taken 2006-05-31. This image shows more clearly the area of the
railroad fill that appears to have sloughed down during the 1996-1997 flood (yellow outline). Compare with the smaller
sloughed area on the 1993 image.
Figure 12 – Google Earth image of Bardees Barspoil pile taken 2012-07-09. Note muddy sediment that washed down from
the area of the railroad track.
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Figure 13 – Google Earth image of Bardees Bar spoil pile taken 2017-07-02. Increased headward erosion can be seen at the
lower end of three of the gullies near the center of the steep slope (white arrows).
Figure 14 – Google Earth image of Bardees Bar spoil pile taken 2018-12-11.
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Figure 15 – These two Google Earth images from 2008 (top) and 2018 with deep shadows show the extent of gullying and
erosion on the steep face of the spoil pile. Except for the three higher scarps at the toe of the slope, there is very little
apparent change over these ten years.
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Figure 16 – Helicopter view of spoil pile looking south. Image taken August 5, 2019.
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Figure 17 – Helicopter view of spoil pile looking east. Image taken August 5, 2019.
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Figure 18 – View of railroad track looking north. Note dried sediment in ditch to west of railroad track ballast. Runoff water
apparently flows down this ditch toward photographer and turns west onto the spoil pile at the bottom of the image. Image
taken August 5, 2019.
Figure 19 – Composite view looking north along the western edge of the spoil pile bench. Runoff water flows down the swale
in the foreground away from the photographer. Image taken August 5, 2019.
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Figure 20 – Composite view of the western edge of the upper bench. Tree on the left is the same tree in the upper left on the
previous image. Some of the water in the swale goes over the edge of the low berm and down the gulley below this tree.
Image taken August 5, 2019.
Figure 21 – Another composite view of the shallow swale on the western edge of the bench looking to the north. The bench
is well vegetated with some bushes and trees starting to establish. Image taken August 5, 2019.
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Figure 22 – This broad swale down the west slope of the spoil pile is where most of the water collecting on the bench flows
down to the toe of the slope and the river. There is an incised channel within the swale. Image taken August 5, 2019.
Figure 23 – A composite view of the broad swale seen in the previous image, this time looking to the south. Note the incised
channel in the middle distance that is armored with cobble- to boulder-sized rocks. Angles are distorted in this composite
image. Image taken August 5, 2019.
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Figure 24 – A view up grade on the old access road on the north end Figure 25 – A view down grade from the same location as the previous image.
of the spoil pile. There are remnants of paving as seen on the right of The road was made with a rock cut as seen in the distance. Image taken August
the image. Image taken August 5, 2019. 5, 2019.
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Figure 26 – View south down the lower leg of the old access road after it makes a sharp bend at the abandoned bridge. Note rock cut to the left and the slope of the spoil
pile in the distance. There is a broad and flat boulder and cobble bar between the toe of the slope and the main river channel. Image taken August 5, 2019.
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Figure 27 – Point where the lower access road enters the top of the boulder bar. The road base is well compacted, and cohesive. Scour along the edge of the road has
occurred during past significant floods. Image taken August 5, 2019.
Figure 28 – View upstream of the boulder bar between the north end of the spoil pile on the right and the river channel to the left. The lower access road comes down the
slope in the middle right of the image. The top of the boulder bar is about 15 feet above the river channel at this point. Note the waterfall in the distance where the river
drops about 15 feet in elevation while going over an erosion resistant rock ridge.
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Figure 29 – View south of the northern end of the spoil pile slope showing the lower end of the broad swale with incised channels. Note the boulders in the bar. Rounded
gray boulders to the right appear to be river deposits, while the more angular brown boulders to the left are from the tunnel spoil pile. The toe of the spoil pile is well
armored with large boulders in this area. Angles are distorted in this composite image. Image taken August 5, 2019.
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Figure 30 – Image of the broad swale near the north end of the spoil pile slope. There are incised gullies on the margins of the swale. The tunnel muck is slowly raveling, and
the surface is well drained, preventing the establishment of vegetation. Note flood-borne sand deposits between the boulders in the foreground. Image taken August 5,
2019.
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Figure 31 – View south of the spoil pile slope showing the concreted riprap armoring on the south half of the fill toe There appears to be an older generation of cementitious
material from the 1950s, or earlier, below the grayer concrete applied following the 1997 flood. The river channel narrows here and the boulder bar is no longer present at
the toe of the slope. Note the steeper scarp at the upper edge of the image with raveling rock below. Image taken August 5, 2019.
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Figure 32 – North half of the spoil pile slope. Note steep scarp at upper edge of image with raveling rock spoil below. There is a remnant of concrete paving on the old access
road between the persons. Note boulder bar in distance where the canyon bottomis wider. Image taken August 5, 2019.
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Figure 33 – South toe of fill slope showing two generations of cementitious armoring. The lower layer is believed to date from the 1950sor earlier, while the upper layer of
concreted riprap dates from the 1990s. The lower layer is undermined by river flows to unknown depth, but large rocks are visible in the water below. Image taken August 5,
2019.
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Figure 34 – View of the river channel to the west of the spoil pile toe (concreted riprap armoring seen on the right edge of the image). There are numerous outcrops of
erosion resistant bedrock in the river channel here, visible in the foreground, mid-channel, and far bank. Note boulder bar in the distance. Image taken August 5, 2019.
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Figure 35 – View of the natural gulley that crosses over the railroad tunnel. Water flowing down this gully discharges onto the north end of the spoil pile bench. Image taken
August 5, 2019.
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Figure 36 – Topography with five-foot contours overlaid on photographic image from 2019 LiDAR survey.
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Figure 37 –2019 LiDAR analysis of slope steepness overlaid with five-foot topography contours.
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Profile A-A’
Profile B-B’. Profile C-C’.
Figure 38 – Locations of profiles with 2019 LiDAR slope shading and five-foot contours.
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Figure 39 – Flow accumulation map based on 2019 LiDAR survey.
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Figure 40 – Potential alternatives for additional engineering analysis. Includes Options 1, 2, 3 and status quo. The black lines
represent engineered alternatives and the blue lines represent surface drainage.
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Enclosure 2
Forest Service approval letter dated December 16, 2020
and PG&E’s letter dated October 22, 2020
requesting approval
Logo Department Name Agency Organization Organization Address Information
United States Forest Pacific Southwest Region 159 Lawrence Street
Department of Service Plumas National Forest Quincy, CA 95971
Agriculture 530-283-2050
TDD: 530-534-7984
Fax: 530-283-7746
File Code: 2770
Date:December 16, 2020
Steve Bauman
Senior Relicensing Manager
Pacific Gas and Electric Company
Mail Code N11D
P.O. Box 770000
San Francisco, CA 94177
SUBJECT:FOREST SERVICE APPROVAL OF RESOURCE MANAGEMENT PLANS AND
EXTENSIONREQUESTSFORPACIFICGASANDELECTRICCOMPANY’SPOE
HYDROELECRTRIC PROJECT, FERCNO. 2107
Dear Mr. Bauman:
This letter is regarding seven Resource Management Plans (“Plans”), required by the Federal
Energy Regulatory Commission (FERC) License for Pacific Gas and Electric Company’s
(PG&E) Poe Hydroelectric Project (P-2107). The Forest Service filed revised final Federal
Power Act (FPA) Section 4(e) Conditions in July of 2018, including a requirement to develop
these Plans, and these Conditions became part of the new FERC license for the Poe
Hydroelectric Project, issued on December 17, 2018.
The new license for the Poe Hydroelectric Project requires 15 Plans, establishment of a
Recreation River Flow Technical Group with two associated Memoranda of Understanding
(MOU) covering river recreation, and development of an operations water balance modelwithin
one year of license issuance; i.e., by December 17, 2019. Two additional Plans are required
within one-two years of license issuance; i.e., December 17, 2020. Attached is the Forest
Service’s understanding of the current status of all these Plans.
By letters to PG&E (dated December 6, 2019, and March 19, 2020), I previously approved six
Plans, and the operations water balance model. In addition, these letters provided concurrence
on Plans and an MOU required by the State Water Resources Control Board, and my approval
for PG&E’s extension requests for the remaining Plans. I signed the MOU (required within
Forest Service Condition No. 26) on August 12, 2020. On September 25, 2020, I approved the
Recreation Enhancement, Construction, and Implementation Plan (Forest Service Condition
No. 26).
Over the past two months, PG&E has submitted four additional completed Plans, one revised
Plan, and two extension requests. With this letter, I approve the following:
Bald Eagle Plan (Forest Service Condition No. 35) - PG&E final plan approval request
dated October 19, 2020.
Caring for the Land and Serving People Printed on Recycled Paper
2
Steve Bauman
Assessment and phased implementation plan for the Bardees Bar Tunnel Spoil
Revegetation Plan (Forest Service Condition No. 40) - PG&E approval request dated
October 22, 2020
Long-Term Ramping Rate Plan (Forest Service Condition No. 23, Part 5) – six-month
extension to complete Plan - PG&E request dated October 29, 2020
Sediment Management Plan (Forest Service Condition No. 23, Part 3A) - minor revision
to previously approved Plan - PG&E approval request dated November 19, 2020
Heritage Properties Management Plan (Forest Service Condition No. 31) – one-year
extension to complete Plan - PG&E request dated December 3, 2020
Road Management (Forest Service Condition No. 37) –PG&E final plan approval
request dated December 15, 2020
Integrated Vegetation Management Plan (Forest Service Condition Nos. 29 and 34) –
PG&E final plan approval request dated December 15, 2020
Thank you for working with the Forest Service on these resource plans for the new Poe
Hydroelectric Project license. If you have any questions about this letter, please contact Amy
Lind, Hydroelectric Coordinator, Regional Hydropower Assistance Team, at (530) 478-6298,
amy.lind@usda.gov, or Emily Moghaddas, Recreation, Engineering, Lands, and Minerals Staff
Officer, Plumas National Forest, at (530) 283-7772, emily.moghaddas@usda.gov.
Sincerely,
CHRISTOPHER CARLTON
Forest Supervisor
cc: Dawn Alvarez, Amy Lind, David Brillenz, Emily Moghaddas, Hilary Maxworthy
3
Steve Bauman
ATTACHMENT
Status of Management and Monitoring Plans and MOU's for Poe Hydroelectric Project (FERC No. 2107) new license implementation.
Plan or MOU (Forest Service Condition Original Due Date to the Amended Due Date to the
Status
No. or SWRCB Condition only) FERC FERC
Fish and Benthic Macroinvertebrate Plumas National Forest (PNF) staff have reviewed and PG&E
Dec. 17, 2019 Completed in 2019
Monitoring (Condition No. 25) addressed comments. Final Plan provided to PNF and FERC.
RO and PNF staff have reviewed and PG&E addressed
Hazardous Substances (Condition No. 5)Dec. 17, 2019 Completed in 2019
comments.Final Plan provided to PNF and FERC.
Final version provided to
Operations Water Balance Model This is a working model/tool. License condition due date met, Not required to have Forest Service on Dec. 9,
(Condition No. 23, Part 2) and model will be updated as needed. FERC approval 2019; Not required by the
FERC
PNF staff have reviewed and PG&E addressed comments.Final
Gaging (SWRCB) Dec. 17, 2019 Completed in 2019
Plan provided to PNF and FERC.
PNF staff have reviewed and PG&E addressed comments. Final
Water Temperature Monitoring (SWRCB) Dec. 17, 2019 Completed in 2019
Plan provided to PNF and FERC.
SWRCB and Forest Service approve, but do not sign. PNF staff
MOU1 (SWRCB) -Recreation Technical
have reviewed and PG&E addressed comments; other signatories Dec. 17, 2019 Completed in 2019
Review Group
are complete.
PNF staff have reviewed and PG&E addressed comments. Final
Amphibian Monitoring (Condition No. 25) Dec. 17, 2019 Completed in March 2020
Plan provided to PNF and FERC.
PNF staff have reviewed and PG&E addressed comments. Final
Tributary Access Observation (fish) Dec. 17, 2019 Completed in March 2020
Plan provided to PNF and FERC.
(Condition No. 23, Part 6)
Completed in March 2020;
Sediment Management (Condition No. 23, PNF staff have reviewed and PG&E addressed comments. Final
Dec. 17, 2019 Minor revisioninNovember
Part 3A) Plan provided to PNF and FERC.
2020
Fire Prevention and Response (Condition PNF staff have reviewed and PG&E addressed comments. Final
Dec. 17, 2019 Completed in March 2020
No. 7) Plan provided to PNF and FERC.
PNF staff have reviewed and PG&E addressed comments. Final
MOU2 -Poe Interagency Recreation River Prior to first full recreation Completed/fullysigned in
MOU provided, but PNF is waiting on signatures from other
Flow Management (Condition No. 26) season. August 2020
parties.
PNF staff have reviewed and PG&E addressed comments. Final
Riparian Monitoring (SWRCB) Dec. 17, 2019 Completed in March 2020
Plan provided to PNF and FERC.
4
Steve Bauman
Plan or MOU (Forest Service Condition Original Due Date to the Amended Due Date to the
Status
No. or SWRCB Condition only) FERC FERC
PNF staff have reviewed and PG&E addressed comments. River
Recreation Enhancement, Construction,
flow plan required under MOU2 is included as an attachment to Dec. 17, 2019 Completed in September 2020
and Implementation (Condition No. 26)
this Plan. Final Plan provided to PNF and FERC.
PNF staff have reviewed drafts, participated in field condition
Road Management (Condition No. 37) assessments, and PG&E has addressed comments. Final Plan Dec. 17, 2019 Dec. 31, 2020
provided to PNF.
Regularly meeting with PG&E and other stakeholders to discuss
Long Term Ramping Rates (Condition No. approach and content of this Plan; PG&E provided a draft Plan
Dec. 17, 2019 June 30, 2021
23, Part 5) provided to stakeholders in July 2020. Tied to upstream
hydroproject – further discussion needed to complete Plan.
PG&E provided aTechnical Assessment(TA)to PNF inMay
2020, which was reviewed by PNF staff. In October 2020, Plan is now phased Plan and
Bardees Bar Tunnel Spoil Revegetation
PG&E provided a revised TA along with a plan and schedule for Dec. 17, 2019 split into two Plans; expected
(Condition No. 30)
completing: the stability plan, a targeted revegetation plan, and completion 2021-2022
implementation of both plans.
PG&E provided an Archeology Report to PNF in late May 2020;
Heritage Properties Management
Traditional Cultural Properties study is ongoing with interviews Dec. 17, 2019 December 31, 2021
(Condition No. 31)
delayed due to Covid; pending draft of full Plan from PG&E.
PG&Eprovided draft Plan in July 30, 2020; PNF reviewedPlan
Bald Eagle Management (Condition No.
and discussed with PG&E in August. PG&E addressed Dec. 17, 2020 No change
35)
comments and provided a final plan provided to PNF.
Combines two Forest Service License Conditions; PG&E
Fuel Treatment and Invasive Weed
provideddraft Plan on Aug. 10, 2020. PNF staff have reviewed
Management (Integrated Plan) (ConditionDec. 17, 2019 and 2020Dec. 31, 2020
drafts, and PG&E has addressed comments. Final Plan provided
Nos. 29 and 34)
to PNF.
245 Market Street
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San Francisco, CA 94105
Mailing Address:
Mail Code N11D
P.O. Box 770000
San Francisco, CA 94177
October 22, 2020
Mr. Erik Ekdahl Mr. Christopher Carlton
Deputy Director, Division of Water Rights Forest Supervisor
California State Water Resources Control United States Department of Agriculture,
Board Forest Service
th
1001 I Street, 14 Floor Plumas National Forest
Sacramento, CA 95814 159 Lawrence Street
Quincy, CA 95971-6025
RE: Poe Hydroelectric Project, FERC Project No. 2107-CA
Actions to Comply with SWRCB Condition 15 and Forest Service Condition
No. 40 Regarding Bardees Bar Tunnel Spoil Revegetation Plan
Dear Messrs. Ekdahl and Carlton:
Pacific Gas and Electric Company (PG&E) seeks your approval of the attached Poe
Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control Assessment
(Assessment Report) and the actions outlined in this letter explaining how PG&E plans to
comply with the Bardees Bar Spoil Pile revegetation requirements of the Poe Hydroelectric
Project Federal Energy Regulatory Commission (FERC) license (FERC P-2107). The spoil
pile is discussed in two license conditions, as follows:
State Water Resources Control Board (SWRCB)
Pile Revegetation: Within one year of license issuance, the Licensee shall file a
Bardees Bar Spoil Pile Revegetation Plan with the Deputy Director for review and
spoil pile shall be revegetated with appropriate local endemic
pile near the North Fork Feather River.
Forest Service ar Tunnel Spoil
Pile: Within one year of License issuance, Licensee shall file with the Commission a
Bardees Bar tunnel spoil revegetation plan, approved by the Forest Service for the
include an implementation schedule, site preparation and planting techniques, number
of planting sites, plant species to be established and follow-up measures to ensure
Mr. Erik Ekdahl
Mr. Christopher Carlton
October 22, 2020
Page 2
and obl
The plan shall also include an evaluation of the stability of the undercut concrete
features located at the foot of the spoil pile as well as a schedule for stabilization or
removal of undercut concrete from the stream channel.
Following issuance of the Poe FERC license, PG&E consulted with the SWRCB, Forest
Service, and FERC to determine how to best to address these conditions. It was agreed
that a phased approach would be most appropriate. This approach, described in extension
of time requests filed with both the SWRCB and Forest Service in late 2019, began with
PG&E preparing the attached Assessment Report. The report was shared with agencies
on May 26, 2020.
The Assessment Report discusses potential issues related to revegetation of the spoil pile,
including substrate coarseness and associated rapid drainage, exposure (heat and dry
conditions), and access to the steeper portions of the slope (making access to revegetate
the slopes extremely unsafe). However, there are areas of the spoils pile that currently
support plants, primarily yellow star thistle (an invasive weed) and grasses. This indicates
that at least early successional native species may be successfully planted on the site.
As noted in the Assessment Report, the concrete feature at the southern end of the spoil
pile was not constructed by PG&E and was put in place in 1997 by Union Pacific Railroad
(Geomatrix 2003). PG&E does not recommend additional toe protection in this area
because of the shallow bedrock outcrops visible near the river, and the satisfactory
Any changes to this feature should be
coordinated with Union Pacific Railroad. Although Condition 15 also requires erosion
control measures at the toe of slope, PG&E drainage control
improvements at the top of the berm and on the north end will provide the appropriate
erosion control.
To improve stability and address existing invasive weedson the tunnel spoil pile, PG&E
requests approval of the following course of action:
1. 2021 2022
Prepare and submit for approval a Bardees Bar Tunnel Spoil Stability Plan
(Stability Plan) that includes an analysis of site constraints, drainage control
engineering, and design drawings for drainage control measures on the top and
northern portion of the site. Site constraints include railroad property, electric
transmission corridor, topography, soils, etc. The Stability Plan will include a
post-construction slope stability monitoring plan with monitoring and reporting
every 5 years. Reporting and consultation with the Forest Service and SWRCB
will be completed after each monitoring event, with the draft report delivered to
the Forest Service at the annual consultation meeting required under Condition
No. 3 and copied to SWRCB. After the meeting, the final report will be submitted
to FERC and a copy will be provided to both Forest Service and SWRCB.
Mr. Erik Ekdahl
Mr. Christopher Carlton
October 22, 2020
Page 3
Prepare and submit for approval a targeted (short-term) Revegetation Plan to be
implemented coincidentally with the Stability Plan. The Revegetation Plan will
address management (control) of existing invasive weeds and include measures
to support growth of appropriate native plant species. The Revegetation Plan will
focus on the top, flat portion of the site, and will not encroach upon the railroad
property (100 feet either side of their tracks).
2. 2022 SWRCB, Forest Service, and FERC approval of Stability Plan and
Revegetation Plan.
3. 2023 construct drainage control measures as described in the Stability Plan, with
as-built report at end of construction; coincidentally implement the Revegetation
Plan.
Since the Assessment Report, including proposed next steps, was submitted to SWRCB
and Forest Staff on May 26, 2020 for review, PG&E has consulted with agency staff on
August 11 and October 13, 2020 with calls to confirm acceptance of the final Assessment
Report and to continue incorporating staff suggestions on this approval request letter. In
addition, Forest Service Condition No. 30 requires coordination regarding the removal of
were 10(a)
recommendations that FERC did not require in the License and they are therefore not
included in PG&E plans.
Coordinator, Matthew Joseph, at 415-973-8616.
Sincerely,
Janet Walther
Senior Manager, Relicensing
Attachment
Poe Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control Assessment
cc: via email
Savannah Downey (SWRCB)
Amy Lind (Forest Service)
Emily Moghaddas (Forest Service)
Enclosure 3
SWRCB letter dated December 21, 2020 providing
conditional approval of the Plan
State Water Resources Control Board
December21, 2020
Mr. Steven Bauman, P.E.
Senior Relicensing Project Manager
Mail Code N11D
P.O. Box 770000
San Francisco, CA 94177
Sent via email: sjb2@pge.com
Poe Hydroelectric Project
Federal Energy Regulatory Commission Project No. 2107
Butte County
North Fork Feather River
CONDITIONAL APPROVAL OF POE BARDEES BAR TUNNEL SPOIL PILE SLOPE
STABILITY AND EROSION CONTROL ASSESSMENT AND IMPLEMENTATION
PLAN
Dear Mr. Bauman:
On October 22, 2020, Pacific Gas and Electric Company (PG&E) submitted the Poe
Bardees Bar Tunnel Spoil Pile Slope Stability and Erosion Control Assessment
(Assessment Report) and associated implementation schedule to the State Water
Resources Control Board (State Water Board) Deputy Director of the Division of Water
Rights (Deputy Director) for review and approval. PG&E developed the Assessment
1
Report and schedule per the requirements of Condition 15 of the Poe Hydroelectric
2
Project’s (Project) water quality certification (certification).
Condition 15requires PG&E to develop a plan to revegetate a construction spoil pile
and implement erosion control measures to prevent potential water quality impacts. In
consultation withUnited States Forest Service (Forest Service), Federal Energy
Regulatory Commission (FERC), and State Water Board staff, PG&E developed a
phased approach to implement certification Condition 15.The Assessment Report,
which is part of the first phase of Condition 15 implementation, summarizes
observations of spoil pile erosion and slope instability and provides recommendations
1 TheAssessment Reportsatisfiesa portion of the Condition 15 requirements.
Submission of additional plans by PG&E is still required.
2
The Project certification was issued by the State Water Board Executive Director on
December 28, 2017.
Mr. Steven Bauman-2-December 21, 2020
for improving drainage and reducing erosion during precipitation events. These results
and recommendations will inform the development of the Bardees Bar Tunnel Spoil Pile
Stability Plan and a Revegetation Plan (collectively referred to as the Bardees Bar Spoil
Pile Revegetation Plan in Condition 15 of the certification).
The Assessment Report includes the following proposed schedule for implementing the
remaining portions of Condition 15:
2021 – 2022: Prepare and submit a: (1) Bardees Bar Tunnel Spoil Pile Stability
Plan (Stability Plan); and (2) Revegetation Plan that targets revegetation on the
top and flat portion of the pile;
2022: Appropriate agencies review and approval of the Stability Plan and
Revegetation Plan; and
2023: Commence implementation of the Stability Plan and Revegetation Plan.
PG&E shared the draft Assessment Report with Forest Service and State Water Board
staff on May 26, 2020. PG&E worked with agency staff to address comments and
finalize the Assessment Report that was submitted for Deputy Director approval in
October 2020. State Water Board staff reviewed the Assessment Report and PG&E’s
3
proposed schedule and finds that it complies with Condition 15 with the conditions
outlined below. The Assessment Report and proposed schedule are hereby approved
with the following conditions:
PG&E shall submit the Stability Plan and Revegetation Plan to the Deputy
Director for review and consideration for approval no later than June 30, 2022.
PG&E shall implement the Stability Plan and Revegetation Plan upon receipt of
Deputy Director and any other required approvals.
PG&E shall file this approval with FERC.
During the current Coronavirus 2019 emergency, most State Water Board staff are
working from home. Accordingly, if you have questions regarding this letter please
contact Savannah Downey, Project Manager, by email at
Savannah.Downey@waterboards.ca.gov. Written correspondence should be
directed to:State Water Resources Control Board; Division of Water Rights – Water
Quality Certification Program; Attn: Savannah Downey; P.O. Box 2000; and
Sacramento, CA 95812-2000.
3
On February 5, 2020, the State Water Board Executive Director issued a certification
amendment that extended the deadlinefor submittal of the Bardees Bar Spoil Pile
Revegetation Plan from December 17, 2019 to December 31, 2020.
Mr. Steven Bauman- 3 - December 21, 2020
Sincerely,
Erik Ekdahl, Deputy Director
Division of Water Rights
ec:Ms. Kimberly D. Bose, SecretaryMr. Patrick Pulupa, Executive Officer
Federal Energy Regulatory Commission Central Valley Regional Water Board
Via e-filing Patrick.Pulupa@waterboards.ca.gov
Mr. Paul Gosselin, Butte County Mr. Randy Wilson, Plumas County
PGosselin@buttecounty.netRandywilson@countyofplumas.com
Ms. Beth Lawson, CDFW Ms. Sarah Lose, CDFW
Beth.Lawson@wildlife.ca.gov Sarah.Lose@wildlife.ca.gov
Ms. Amy Lind, Forest ServiceMs. Leigh Bartoo, USFWS
Amy.Lind@usda.govAondrea_Bartoo@fws.gov
Mr. Dave Steindorf, American Mr. Chris Shutes, California Sportfishing
Whitewater Protection Alliance
Dave@americanwhitewater.org blancapaloma@msn.com