second mainline to improve traffic
flow through the canyon.
Site Considerations
The combination of BNSFs requirements, the canyon shape and the unique environment
of the Southwest make route selection for a second mainline complex. Additionally, BNSFs
desire to be a good corporate citizen dictates that the second mainline minimize impacts to
habitats and cultural resources.
A number of alignments have been evaluated over the past 20 to 30 years, and alternative
locations were examined in an attempt to find a better route from the New Mexico plains
down to a crossing of the Rio Grande River. But with only 38 miles to accommodate a
1,700-foot difference in elevation and 400- to 500-foot near-vertical drops in the Manzano
Mountain range that intersects the route, following the natural canyon drainage that has
served the railroad for 100 years remains the best option.
To maintain a ruling grade of 1.25 percent, the existing track parallels the natural path of the
Abo Arroyo for most of the route. As is typical of older mountainous alignments, following
the most advantageous location based on the necessary earthwork often meant sharper
track curvatures. The Abo Canyon section required four consecutive 4-degree reversing
curves. Through the western half of the canyon, the railroad has to deviate from the arroyo
to maintain the ruling grade, which required the use of substantial structures.
Several surveys and investigations were undertaken to provide additional data in support
of the Final Engineering.
continued on page 2
Coalition Secures $4 Billion
for Freight in SAFETEA-LU
page 4
Advanced Technology
Guides ARRC Bypass at
Wasilla
page 5
Pursuing SMART 70-
Mile Commuter Rail
Corridor in Northern
California
page 7
New Self-Mailing Rail Line
You may have noticed your November
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take another step by transitioning to
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Ken Wall, at RLeditor@hdrinc.com to
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Thank you,
Ken Wall
Rail Line Editor
Between 80 and 100 trains pass through the rugged Abo Canyon segment of BNSFs TRANSCON each day.
i n s i d e
a technical publication of hdr
volume 15 issue 1, November 2005 Cultural Resource Survey
Taschek Environmental performed a pedestrian cultural
resource survey to locate all cultural resources within the
corridor, including archaeological sites, structures more than
50 years old and isolated occurrences of artifacts. The railroad
and the bridges themselves were considered to be historic
cultural properties.
It was determined that working within the curvature design
parameters, no alignment could be developed that avoided
all resources. Although less mitigation would be necessary
along the northern routes than the southern, all of the eligible
sites can be mitigated.
Environmental Constraints
On-site field surveys were performed to identify the limits of
jurisdictional waters within the project area and whether any
biological resources would be impacted by the project.
The results of the water resources survey indicate that
the arroyos delineated within the defined corridor are
jurisdictional under the Clean Water Act, Section 404.
The recommended alignment was developed around this
constraint and will impact a minimum amount of jurisdictional
stream channels and wetlands.
The biological resources survey identified a potential habitat
for raptors and federally endangered Southwestern willow
flycatchers. Although some raptor nest sites were located
within the corridor and some hawks and falcons were
identified during the field survey, no nests will be impacted
by the proposed construction and no endangered raptors
were identified. Surveys for the willow flycatcher identified
two marginal habitat locations. No individuals of this species
were observed during the required study period in 2004 and
2005. The recommended alignment will not physically impact
either of these sites.
The states wildlife agency expressed concerns regarding
train-strikes of bighorn sheep and their habitat that has been
reinstated within the canyon. A wildlife fence will be installed
to protect wildlife from potential accidents with the railroad,
and crossings will be provided through the bridge openings
within the canyon.
Geologic Investigations and Geotechnical
Recommendations
Shannon & Wilson (S&W) performed a geological investigation
based on the visible geology of Abo Canyon to develop
preliminary cut and fill slope recommendations, as well as
an assessment of the excavation methods for constructing
the new track. Bridge foundation recommendations were
developed, as well as an evaluation of rock-fall hazards and
procedures to reduce these hazards. A review of geologic
maps, professional papers, published geologic studies for
the area and other available technical references also were
utilized. Subsurface explorations and laboratory testing were
done during the final design process.
The major geologic hazards were divided into three categories:
differential erosion and toppling failures; structurally
controlled failures; and landslides.
Differential erosion in areas where less erosion-resistant
claystones and siltstone underlie and undermine more erosion-
resistant, higher-strength limestone beds accounted for the
principal rockfall hazards and slope failure mechanisms. This
condition exists in the cuts located on the east side of the
canyon.
Rockfall events may also occur as structurally controlled
sliding along a single discontinuity, or sliding along a
combination of discontinuities in the existing railroad cuts.
Although the S&W analysis indicated that plane shear and
wedge failures are possible, the existing slopes along the
railroad are generally stable, and rockfall probably occurs
only as a consequence of loosening and deterioration of the
rock mass after repeated freeze and thaw cycles. Stable slopes
would be designed into the new second track alignment.
Four relatively large landslides are present within or in
proximity to Abo Canyon, but only one, located in the middle
section of the existing track, would have been crossed by
the second track addition, based on alignment alternatives.
The existing track also lies in this landslide, although the
base of the slide lies primarily on fill material, which tends
to stabilize the failure. However, any of the alignment
alternatives that require excavation of the slide material could
potentially destabilize the material, resulting in additional
slides. The flatter the curve at this location, the greater the
potential impact the excavation could have on the slide. This
midsection slide area had the most influence on the selected
alignment.
HDRs Proposed Alignment
Beginning at the west end of the existing double track at
Scholle (at the east end of the project) an alignment shift
of the existing track will be made to allow two tracks to be
constructed under the US 60 overpass structure.
Double Tracking Challenge...continued from page 1
2
The canyon shape and unique environment of the Southwest make route selection for a second mainline through Abo Canyon complex. 3
The new second track alignment would be constructed by
extending the tangent of the track under the US 60 overpass
for approximately one mile.
Another mile of the alignment will be constructed south of
the existing track including new bridges over the Abo Arroyo.
The new alignment was moved farther south at this location
to provide sufficient room when excavating the existing
cut to minimize rocks falling on the active track during
construction.
Continuing from east to west, a track swap-over would then
be provided after New Bridge 4 (See map, previous page) to
allow the new track to be constructed along the north side of
the existing track. The new second track continues along the
north side for about another mile where it would connect back
into the existing track.
Another track swap would then be made after New Bridge
5 to move the new second track along the south side of the
existing track. Reversing curves where provided to move the
excavation for the new track far enough away from the existing
track to minimize rockfall potential within the existing cut.
The new second track then continues through a rock quarry
along the south side of the existing track, tying back into the
existing double track at the east end of the station of Sais.
Summary
Final engineering produced a second alignment through Abo
Canyon that satisfied all of the requirements prescribed by
BNSF:
Utilize existing alignment as parts of both tracks with
swap-overs, where needed
Minimize need for track and time windows on existing
alignment
Reduce rock-fall hazards