Canton Viaduct

Canton Viaduct is a blind arcade cavity wall railroad viaduct in Canton, Massachusetts, built in 1834–35 for the Boston and Providence Railroad (B&P).
At its completion, it was the longest () and tallest () railroad viaduct in the world; today, it is the last surviving viaduct of its kind. It has been in continuous service for years; it now carries high-speed passenger and freight rail service.
The Canton Viaduct's walls are similar to the ancient curtain wall of Rhodes (built about 400 BCE) with rusticated stone. It supports a train deck about above the Canton River, the east branch (tributary) of the Neponset River. The stream pool passes through six semi-circular portals in the viaduct, flowing to a waterfall about downstream.
The viaduct was the final link built for the B&P's then mainline between Boston, Massachusetts; and Providence, Rhode Island. Today, the viaduct serves Amtrak's Northeast Corridor, as well as Massachusetts Bay Transportation Authority (MBTA) Providence/Stoughton Line commuter trains. It sits 0.3 miles (0.5 km) south of Canton Junction, at milepost 213.74, reckoned from Pennsylvania Station in New York City, and at the MBTA's milepost 15.35, reckoned from South Station in Boston.
Inception.
The Canton Viaduct was erected in 1835 by the B&P, one of the first New England railroads, shortly after its 1831 founding. Thomas B. Wales, one of the original families of Boston, and owner of the T.B. Wales & Co. Shipping Company, was the first president of the B&P, The Taunton Branch Railroad, as well as the Western Railroad Corporation. Due to his friendship with prominent New England families, including the Revere family, they were able to bring the Canton Viaduct to fruition. The T.B. Wales & Co. clipper ships brought raw materials for manufacturing companies from its dock (Wales Wharf) and Counting House (Long Wharf) to various areas in New England. Without the influence of individuals such as Thomas B. Wales, Joseph Warren Revere, owner of the Revere Copper Company and major stockholders (most of whom were Board members), the Canton Viaduct would not have been built. There were better routes through other towns for the location of the railroad line from Boston to Providence. However, building the railroad through Canton placed the line close to Paul Revere's Copper Rolling Mill, where a half mile spur (using strap rails and horse power) connected the mill to Canton Junction and undoubtedly gave a boost to Revere's copper business. The other influencing factor that caused the Canton Viaduct to be built was a fatal accident in 1832 on the Granite Railroad, which used inclined planes to cross a valley. The original plans called for the use of inclined planes to cross the Canton River Valley (Canton Dale), but they were changed after the inclined plane accident, and a viaduct was built instead. This unique viaduct was designed by a U.S. Army Corps of Engineers Officer and West Point graduate - Captain William Gibbs McNeill. He was assisted by engineers, Major George Washington Whistler (McNeill's brother-in-law), Major General Isaac Ridgeway Trimble and General William Raymond Lee. McNeill and Whistler were the uncle and father of the artist James McNeill Whistler. The viaduct was built by the Dodd & Baldwin company from Pennsylvania; the firm was established by cousins Ira Dodd and Caleb Dodd Baldwin. Around this time, Russia was interested in building railroads. Tsar Nicholas I sent workmen to draw extensive diagrams of the Canton Viaduct. He later summoned Whistler to Russia as a consulting engineer to design the Moscow–Saint Petersburg Railway, on which two viaducts were modeled after the Canton Viaduct. A viaduct of similar design is on display at the Oktyabrsky Railroad Museum in St. Petersburg.
Design and construction.
Classification.
This Canton Viaduct is the first and possibly only viaduct to use both a blind arcade and cavity wall structure. The structure is often referred to as a "multiple arch bridge", but it does not fit the classic definition of spanning a distance between two points. Although the deck arches appear to extend through to other side, they do not; each deck arch is only four feet deep. The deck arches support the spandrels, deck (beyond the walls), coping and parapets; they are not tied to the longitudinal walls. The only arches that extend through to the other side are six river portals and two roadway portals. The 'buttresses' are also unique in that they extend through to the other side, so they are actually transverse walls. Due to its use of double walls and lack of open arches, the Canton Viaduct is more accurately described as a blind arcade cavity wall. The Thomas Viaduct (Maryland, 1835) and Starrucca Viaduct (Pennsylvania, 1847) are classic examples of multiple arch viaducts, as their primary support system consists of open semi-circular arches spanning the distance between piers, without any walls.
Materials.
The Canton Viaduct contained 14,483 cubic feet (15,800 perches) of granite, which weighs approximately prior to its concrete redecking in 1993. Each stone has a Mason's mark to identify who cut the stone. Each course is 22" - 24" high and laid in a pattern closely resembling a Flemish bond. Exterior stone for the walls, wing wall abutments, portals, deck arches, coping, parapets and the foundation stone are riebeckite granite mined from Moyles quarry (a.k.a. Canton Viaduct Quarry) located on the westerly slope of Rattlesnake Hill in Sharon, Massachusetts; now part of Borderland State Park. This type of granite was chosen because it does not stain as it weathers, but retains its original color. Interior stone for the foundation, walls, wing wall abutments, binders, stiles, deck, Dedication Stone and capstone are of a different type of granite mined from Dunbar's quarry in Canton, Massachusetts.
Location.
The majority of the viaduct is over land (71%), while 29% is over water. In addition to the six river portals, one roadway portal was originally provided. The distance between the transverse walls at this section is wider than all the other sections of the viaduct. The overall length is with a one degree horizontal curve that creates two concentric arcs. This makes the west wall slightly shorter than the east wall producing a slight keystone shape in the cavities. Originally unnamed, it was referred to as "the stone bridge" and "the viaduct at Canton" before it was eventually named after the town.
In 1840 the road under the viaduct was known as "the street leading from Neponset Bank by Elisha White's to near Joseph Downes." Sometime after, it was known as "Rail Road St.", and in 1881, it was finally named "Neponset St." after the river. It serves as a major artery in Canton connecting its main street (Washington St.) to Interstate 95.
Freemasons.
The stone cutters and masons who worked on the viaduct were Scottish Freemasons from local area lodges. In addition to the workmen, the majority of the B&P's Board of Directors were Freemasons, including Thomas B. Wales and Joseph W. Revere.
The foundation stone was laid on Sunday, April 20, 1834 with a Masonic Builders' rites ceremony. Following to Masonic tradition, the foundation stone was located in the northeast corner of the structure.
Construction.
The Canton Viaduct cost $93,000 to build ($ today). Construction took 15 months, 8 days from laying of the foundation stone on April 20, 1834, to completion on July 28, 1835.
The first and last transverse walls (next to the wing wall abutments) are only 3 feet wide, all the other transverse walls are 5 feet, 6 inches wide. The wing wall abutments are 25 feet wide where they meet the viaduct; they are curved and stepped and were excavated by William Otis using his first steam shovel. From the top of the wing walls to midway down, the stones are of 2' wide; from midway down to the bottom of the wing walls the stones are 4' wide.
The coping is supported by 42 segmental deck arches (21 on each side) that span the tops of 22 transverse walls beyond the longitudinal walls. The longitudinal walls are five feet thick with a four-foot gap between them joined with occasional tie stones. More construction details are available in the original . When the viaduct had a single set of tracks, the rails were placed directly over the longitudinal walls as the cavity's width is less than standard gauge. When the viaduct was double tracked in 1860, the inside rails were placed directly over the longitudinal walls and the outside rails were supported by the deck arches.
The viaduct was "substantially complete" in June 1835 from various accounts of horse-drawn cars passing over it during that time. The viaduct was built before the advent of construction safety equipment such as hard hats and fall arrest devices. Surprisingly, no deaths were recorded during the construction, but deaths have occurred at the viaduct since completion; mainly from people crossing it while trains passed in opposite directions. Charlie, the old white horse who had hauled the empty railcars back to Sharon, Massachusetts (4 miles), was placed upon the flat car and hauled across the viaduct by the workers, thus becoming the first "passenger" to cross the structure.
A June 6, 1835, in the "Providence Journal" describes it. As reported by the "Boston Advertiser" and the "Providence Journal", "Whistler" was the first engine to pass over the entire length of the road. The engine was built by Robert Stephenson in 1833 in England and named by William Gibbs McNeill in honor of his brother-in-law George Washington Whistler. The trip from Boston to Providence cost $2 one way.
There are examples of Fibonacci numbers and golden ratios in the Canton Viaduct:
Aside from seasonal vegetation control and occasional graffiti removal, the viaduct requires no regular maintenance other than periodic bridge inspections from Amtrak.
Dedication Stone.
The capstone was laid in the south end of the west parapet. This stone sat atop the Dedication Stone and it was the last stone to be laid in the viaduct.
The Dedication Stone is actually two stones now held together with two iron straps on each end. The overall dimensions are approximately 60" long × 36" high × 18" wide (golden ratio), and it weighs approximately 3,780 lbs. The Dedication Stone was originally topped with a 63" long × 8" high × 24" wide capstone with double beveled edges, creating an irregular hexagonal profile. Due to its breaking in 1860, the Dedication Stone is about 1" shorter today than its original height. The damage obscured two directors' names, W. W. Woolsey and P. T. Jackson. Woolsey was also a Director of the Boston & Providence Railroad & Transportation Co. (B&P RR&T Co.) in Rhode Island (incorporated May 10, 1834) which owned the Rhode Island portion of the Boston and Providence rail line. The B&P RR&T Co. merged with the B&P on June 1, 1853.
Railroad track.
During the 1993 deck renovation, two 18-inch-deep troughs were discovered recessed into the granite deck stones running the entire length of the viaduct and spaced at standard gauge width ( inches). The troughs contained longitudinal baulks and were part of the original construction. The baulks supported the rails without the need for transoms as the gauge was maintained by the longitudinal troughs. This is the only known instance of transomless baulks recessed in granite slabs; the original tracks before and after the viaduct used baulks making the B&P originally a baulk railroad. A 1910 photo taken atop the viaduct shows dirt between the cross ties and tracks, so this material may have been used before traditional gravel ballast.
Baulks were used to support strap rails or bridge rail. These early rails would have been replaced with flanged T-rails by 1840. These photos show baulks at Canton Junction in 1871. An 1829 report from the Massachusetts Board of Directors of Internal Improvements describes how the railroad from Boston to Providence was to be built. The report states, "It consists of one pair of tracks composed of long blocks of granite, about one foot square, resting upon a foundation wall extending to the depth of ' below the surface of the ground, and 2' wide at the bottom". The report also calls for using horse-drawn wagons and carriages at 3 MPH on the rail line, not steam locomotives.
Construction sequence.
The Canton Viaduct was constructed in the following sequence:
Waterway.
Spillway Dam at Neponset St. - a.k.a. Canton Viaduct Falls impounds Mill Pond. It is a weir or low head dam that is owned by the MBTA. The 16' high by 90' long granite dam was built in 1900 and currently (2009) averages 78 cubic feet/second annual discharge. Water power was supplied to nearby businesses via water wheel from the canal starting at the waterfall's enclosed plunge pool and continuing about 200' under the Neponset St. bridge. There were also two channels located between the viaduct and the waterfall (one on each side) referred to as sluices, headraces and flumes in various maps. They were filled in sometime after 1937 (U.S. Army Corps of Engineers National Inventory of Dams No. ).
Renovations and repairs.
Project challenges.
It was necessary to maintain the historic fabric of the structure so all work was consistent with the Secretary of the Interior's Standards for Treatment of Historic Structures. The viaduct is located within Massachusetts DCR's Fowl Meadow and Ponkapoag Bog ACEC(Map Tile #7g) so protecting endangered species in the nearby wildlife refuge presented a challenge. Working in and over the Canton River required extensive permitting and close monitoring by environmental groups. The project was also located in a designated National Environmental Study Area.
An excerpt from the September 1998 "Railway Track & Structures" article reads,
It was initially believed that the top of the viaduct was composed of solid granite blocks (originally carrying a single track). After the track and ballast were removed from the structure, troughs were discovered recessed into the granite capstones. The 18" deep troughs ran the entire length of the viaduct and were spaced approximately 56" apart (standard railroad gauge). In some locations, the trough contained a solid piece of oak, including some abandoned spikes. It is believed the troughs held wooden sleepers for the original single track railroad. These loose materials were removed from the deck, and lean concrete was placed to fill the voids. Archival photographs of the sleepers were taken and their remnants will be turned over to the local historical commission. At the approaches to the viaduct, a series of granite walls were uncovered running perpendicular to the tracks. These walls were approximately 7' on center, and it was thought that they might have carried a timber approach structure. The locations of the walls conflicted with new abutments for the PPC beams, and they made it difficult to install sheet piling for the contractor's support of excavation system. The walls were left in place undisturbed beneath the new track structure. HDR, Inc. redesigned the abutments to minimize their depths, eliminate the conflicts and reduce the loading of the temporary support of excavation system.
When the railroad was complete except for the viaduct, trains ran to the viaduct abutments where passengers would exit and descend the embankment. Passengers crossed the river on a hand-operated cable ferry, boarded horse-drawn carriages on a temporary wagonway to cross the valley, then ascended the embankment to board a waiting train at the opposite abutment. The approach walls are believed to have supported the temporary (covered) train platforms to which wooden staircases were attached. These wooden staircases led from the train platforms to stone abutment staircases (with railings) for passengers to descended to the valley floor. A photo from 1871 may have captured one of those walls (bottom left), at the north end, west side of the viaduct. The approach walls may have also served as foundations for the guard houses during World War II.
Many coping stones were discarded during the deck replacement project; they were placed in the field behind the viaduct. Some Canton residents recovered smaller stones from the massive pile before it was hauled off to an unknown destination. Portland Cement Association's "Historic Canton Viaduct" case study has more project details.
Three interior inspections were performed in the winter by two structural engineers using rock climbing equipment to scale the interior walls. The inspectors noticed small, insignificant cracks in the walls and larger cracks in the deck stones that eventually led to the deck being replaced. The stones of the viaduct were placed in such a way as to allow interior access at just three locations. Between the longitudinal walls occasional tie stones connect the walls together. Some tie stones have large, loose stones placed on them to support work planks. The local film crew noticed rock crystal formation taking place, associated with the moist air inside and a rotting wooden platform. They also noticed some thin wood or iron pieces connecting the walls. It is unknown if these iron pieces or the platforms were used during construction or inspection. Stone stiles protrude into the airspace but do not reach the opposite side. The stiles were used to support work planks instead of traditional scaffolding due to the narrow space between the walls.
Proposed renovations.
Over the years the town of Canton has proposed the addition of pedestrian portals to provide safe passage under the viaduct but owners have consistently rejected these proposals.
Critical infrastructure.
In a letter to Canton's Board of Selectmen on February 27, 2002, former Police Chief Peter Bright noted that Massachusetts Emergency Management Agency training for worst-case situations highlights the destruction of the Canton Viaduct for its disruption of the national railroad system; the Federal Government also considers the viaduct a high-risk target.
Public safety.
The Canton Viaduct is a congested, high volume traffic area with an average of 16,400 motor vehicles passing under the viaduct each day. There are many safety issues with the Canton Viaduct and surrounding area:
The lack of sidewalks, crosswalks, signage and lighting, plus the narrow roadway, limited lines of sight and low clearance makes the Canton Viaduct a dangerous crossing for pedestrians and vehicles.
Current status.
In June 2004 the town of Canton developed a Master Plan that identifies what should be preserved and enhanced to meet evolving needs and improve the quality of life. Items from the Master Plan related to Canton Viaduct include:
Some of these items have been implemented and others are in the planning stages.
The Canton Viaduct celebrated its 175th anniversary (demisemiseptcentennial or quartoseptcentennial) on Wednesday, July 28, 2010. A committee was established in 2009 with members of the Canton Historical Commission and Canton Public Library Trustees to plan the anniversary celebration.