Mark Dance’s N scale Columbia & Western Railway models the Canadian Pacific’s Boundary Subdivision in southeastern British Columbia, a line that in reality required nine major bridges totalling nearly 4,000 feet to cross the region’s rivers and creeks. In model form that would amount to more than 25 actual feet of bridgework, so careful planning and measured compression were essential from the start.
Planning for those bridges began long before benchwork was built. Mark spent considerable time sketching and then developing CAD drawings to determine how each bridge, its approaches, and its supporting terrain would fit within the layout’s complex multi-deck design. The result is a railroad where large bridges act not only as engineering highlights but also as integral scenic compositions, each planned in detail to fit within the available space while maintaining believable proportions.
The Kootenay River Bridge
The first of the signature bridges models the CPR crossing of the Kootenay River at Taghum, a 763-foot structure of nine spans over two islands. The prototype combines a 157-foot through truss with multiple half- and full-deck plate girders. Space on the layout allowed for just under three feet, so Mark used selective omission to compress the scene without losing its identity.
A BLMA 150-foot brass through truss stands in for the prototype’s main span, slightly different in panel arrangement but visually accurate. One of the islands and three of the half-deck girder spans were omitted, and the remaining spans slightly shortened. The result retains the recognisable truss crossing over deep water that dominates prototype photographs, yet fits comfortably within the available space.
A solid base of ¾-inch plywood extends the full length of the bridge to support all piers and abutments. This ensured consistent alignment and level track, and simplified the fitting of each of the six spans and eight supports. The scene occupies nearly five feet of the layout next to an aisle only three feet wide, which makes side-on photography challenging but realistic in proportion.
The Slocan River Bridge
Just west of the Kootenay crossing lies the Slocan River Bridge, at milepost 14.6 of the Boundary Sub. The prototype structure is 332 feet long and 69 feet high, with two 85-foot deck girders flanking a 157-foot deck truss. The model reproduces the key visual cues: the symmetric girder–truss–girder sequence, the recessed truss deck, the combination of stone and concrete piers, and the gradual reduction in truss member size toward the centre.
Only 200 scale feet of layout space were available, 60% of the prototype length. A uniform 40% compression would have left the bridge looking too small in proportion to the trains, so Mark used non-uniform compression. The deck girders were shortened by about 50%, while the truss span was reduced by only 20% in both height and length, maintaining the correct angles of the diagonal members. The deck was also set slightly lower between the trusses to balance the visual height of passing rolling stock.
He tested alternatives in CAD, producing three versions—uniform compression, reduced panel count, and mixed compression—and shared them with fellow modellers. The hybrid option, using selective and non-uniform compression together, proved the most convincing and was adopted.
A solid plywood base again extends beneath the river and piers, though in this case the abutments were built onto the ends of the approach roadbed. Mark later noted that continuing the plywood beneath them would have simplified construction.
The McCormack, Farr, and Barr Creek Bridges
Further up the line the McCormack Creek, Farr Creek, and Barr Creek bridges are modelled in the layout’s tilted-benchwork section, part of its mushroom-style double-deck design. Each prototype bridge is a tall steel trestle, and each was uniformly compressed by about 30% in height and length. To accommodate their scale height without increasing the overall deck separation, Mark tilted the middle deck’s open-girder framework so it was lower at the front and higher at the back.
This created roughly 20 inches of usable vertical scenery space for the bridges, compared with only 9 inches if the deck had been level. The compromise required an angled sky backdrop behind Slocan City, the lower scene beneath this section, but access for switching the mill remained adequate. The tilt provided about 150 scale feet of additional height—enough to portray the 190-foot-high trestles convincingly.
Each bridge site was pre-planned in CAD, including scenery profiles showing flat pads for piers and abutments. These were transferred to ¾-inch plywood profile boards fixed beneath the roadbed. Scenery, including trees, was completed long before the bridges themselves were installed. When construction finally took place, small holes were cut through the scenery and the finished piers and abutments dropped through to rest on the pre-set profile boards, which ensured correct height and alignment. The bottom edges of these boards also defined the “air rights” above the lower deck and provided attachment points for the angled backdrops.
The Kettle River Bridge
The fifth and final major bridge is the Kettle River Bridge at the western foot of Farron Hill. The prototype structure is 505 feet long and 80 feet high, consisting of three deck-truss spans interspersed with deck girders, all supported by a distinctive pair of angled steel towers. Mark had cycled across the surviving structure and was determined to reproduce it at full scale, without compression.
The challenge was that this bridge sits directly above Castlegar Junction, one of the busiest operating areas on the layout, containing a yard, multiple meets, and the Kraft mill complex. Lower-deck access was essential, so the solution came through what Mark calls “negotiated air rights.”
- The upper deck benchwork was narrowed to 12 inches, while the lower deck was widened to 24 inches.
- The upper deck was dropped by 5 inches at the bridge site using 1×2 framing with ¼-inch plywood sheathing.
- Clearance between decks was reduced to 8 inches under the bridge, increasing to 14 inches elsewhere.
- Low-profile fluorescent fittings and LED strips were installed between the framing to light the lower deck.
- Tracks and turnouts on the lower level were routed forward around the low-clearance zone.
- A 4–6 inch operating alcove was created beside Castlegar Junction to allow the Kraft Switcher operator space to work comfortably.
This arrangement allowed a full-scale model of the bridge and its approach fill to occupy its rightful place while keeping the lower level functional for switching. In operation, the scene works well, though aisle congestion occasionally mirrors the prototype’s traffic jams.
Design Outcomes
The Columbia & Western’s bridges show how forethought, engineering realism, and artistic composition can coexist in limited space. Each structure was planned using CAD before benchwork began, with surfaces prepared for future installation and scenery often completed years before the bridges themselves. The layout’s double-mushroom configuration, tilted benchwork, and negotiated clearances give every major bridge the vertical space it needs without compromising accessibility.
Through patient design and careful compression, Mark Dance’s N scale Columbia & Western succeeds in capturing the grandeur of the Boundary Subdivision, its rivers, and its towering steelwork within the confines of a basement railway.
SCALE: N (1:160)
SIZE: 16′-6″ x 20′-0″
PROTOTYPE: Canadian Pacific
LOCALE: southern British Columbia
PERIOD: 1970
STYLE: multi-deck walkaround with double-
mushroom peninsula
MAINLINE RUN: 230 feet
MINIMUM RADIUS: 18″ (main), 14″ (branch line)
MINIMUM TURNOUT: no. 5
MAXIMUM GRADE: 2.5 percent
BENCHWORK: open grid
HEIGHT: 30″ to 76″
ROADBED: 3 ⁄4″ plywood
TRACK: Peco code 55 flextrack
SCENERY: plaster gauze shell
BACKDROP: hand-painted linoleum
CONTROL: Digitrax Digital Command Control with
JMRI/PanelPro control
Construction started in June 2005 after 3 years of planning. Housed in a two-car garage. Designed for operation.
All built with 3/4″ plywood.
The primary switching area is around 42″ (107cm) off the floor.
Operating
Nearly 20 trains in a normal operating session.
- Nelson West Switching Job – Primary Classification Switching Job for the layout.
- Nelson East Switching Job – Run hostling as well as switching the east end
- East & Westbound Wayfreights over the boundary subdivision
- East & Westbound Orefreights between Phoenix and West Staging and Tabanac and Trail – because of weights and lengths these often require pusher helpers to get up to the summit at Faron.
- Plough Trains
- Kraft Switcher – from Nelson to Castlegar and back
- Slocan Branch
More Information
- Dance, Mark. “The Columbia & Western.” Railroad Model Craftsman, vol. 81, no. 12, May 2013, pp.54-61.
- Dance, Mark. “Developing an N Scale ‘Mushroom’ Layout.” Great Model Railroads, 2016, pp. 28-37.
- Dance, Mark. “Planning for Big Bridges.” Model Railroad Planning, 2016, pp. 56–63.
- Turner, Robert D. “CPR’s Boundary District.” Railroad Model Craftsman, vol. 81, no. 12, May 2013, pp. 47-53.
- Model Railroader August 2016
- Railroad Model Craftsman (February2014)(March 2014)
- Model Railroad Planning (2012)(2017)
- N Scale magazine
- Canadian Railway Modeller August/September 2012
- Dispatcher’s Office (April 2014)(October 2014)
- Layout Design Journal (#37).