High-speed Rail’s 1835 Underpinning
INCORPORATING SUCH UP-TO-THE- minute technologies as microprocessor control, solid-state electronics, data radio, and a tilting mechanism that banks them around curves, the new 150 mph Acela Express trains on Amtrak’s Washington-New York-Boston Northeast Corridor surely represent cutting-edge transportation for the twenty-first century. But these newest of trains travel over a civil engineer- ing infrastructure that owes much to the skills and foresight of engineers of the very early twentieth, and even the nineteenth, century. Those engineers were men who built well and built to last.
In New York the fast trains will climb high above the East River between the Bronx and Queens on the great steel arch Hell Gate Bridge completed by Gustav Lindenthal in 1917; they’ll reach Manhattan through Hudson and East River tunnels completed by the civil engineers Charles M. Jacobs and Alfred Noble in 1909. But even those are relatively new structures compared with the granite viaduct that will carry the new trains over the valley of a branch of the Neponset River at Canton, Massachusetts. The Canton Viaduct has been in service for 165 years now—and could easily last as many more.
It was built by the Boston & Providence, one of the earliest American railroads, which began laying its 42-mile line south from Boston in 1832. The railroad’s chief engineer was Capt. William Gibbs McNeill, an 1817 West Point graduate and one of a cadre of U.S. Army engineers who helped build the nation’s first canals and railroads. After an early assignment surveying the Atlantic Coast and the Gulf of Mexico with the Army’s topographical corps, McNeill served as aide-de-camp to Andrew Jackson in the Seminole War. In 1828 he was sent to England to study railway-engineering practice and then returned home to help build the pioneer Baltimore & Ohio.
McNeill (whose sister, incidentally, would much later be immortalized by her son, James A. McNeill Whistler, in the painting known as Whistler’s Mother ) drew on his experience on the B&O and other early railroads to lay out a line for the Boston & Providence that was as short and direct as he could make it, but he faced a formidable barrier near Canton, where the route would have to cross the deep valley of the east branch of the Neponset River. So he bridged the valley with a massive multiple-arch granite viaduct that stretched 615 feet and stood 70 feet above the water, laid on a 1-degree curve, with 21 segmental arches on piers 27 feet 6 inches apart. Each pier was 5 feet 6 inches thick and supported the full 22-foot width of the structure. In an unusual departure from normal practice, the arches were filled in with parallel masonry walls 4 feet apart, connected by occasional tie stones. Near the north end of the viaduct, six semicircular arches, each 8 feet 4 inches across, were cut through the walls to provide a passage for the river. A single 22-foot semicircular arch provided space for a roadway near the south end. Stone abutments and a circular wing wall filled out each end of the viaduct, and a great earthen embankment more than 60 feet high completed the crossing of the valley at the north end.
The first foundation stone was laid on April 20, 1834, and then a large crew of stonecutters, masons, and laborers worked for more than a year. The stonemasons who cut the face stones were Scottish Rite Freemasons, and each stone bore the distinctive mark of the man who worked it. The granite all came from within seven miles.
Trains began to cross the viaduct on July 28, 1835, completing the journey between Boston and Providence in only two hours. The structure became the object of great regional pride. The Boston Advertiser predicted that it would “stand for ages an enduring monument of the high talents and high attainments of its accomplished engineer.”
Indeed it did all that and more, for no one then could have visualized just how enduring and adaptable a structure McNeill had built. The Boston & Providence soon was a key link in what would become the New York, New Haven & Hartford’s all-rail Shore Line route between Boston and New York.
The first major change to the structure came in 1860, when the railroad added a second track on it. Stone parapets along each side were removed, and a heavy timber structure projecting several feet out on either side was installed to provide sufficient width for the tracks. In 1880 the timber deck was replaced with an iron structure. In 1910, after one of the stone arches had begun to fail under heavier train loads, the New York, New Haven & Hartford Railroad reinforced the arches with concrete. But aside from that and a second roadway arch cut through the structure in 1952, William McNeill’s splendid viaduct endured little changed through almost the entire twentieth century.
Another round of modifications became necessary when Amtrak and the Massachusetts Bay Transportation Authority (MBTA) decided to develop North America’s first true high-speed train service in the Northeast Corridor. The venerable structure would require reinforcement to safely carry the loads imposed by high-speed trains, and a widened deck would be needed to provide sufficient clearance between the two tracks for the tilting cars that would race through the viaduct’s onedegree curve at 150 mph. This would have to be done without damage to its historic character; the viaduct had been listed on the National Register of Historic Places in 1984.
Thoughtful planning by the Boston preservation architects McGinley Hart & Associates and the firm HDR Engineering did the job. Beginning in 1997, the viaduct’s granite masonry was carefully cleaned and repointed, the concrete reinforcing arches added in 1910 were repaired or replaced, and the masonry structure itself was strengthened and stabilized with novel “minipiles.” Eight of these piles, each 6 inches across, were drilled 60 to 75 feet down through the stone masonry of each pier and into solid bedrock. A high-strength steel rod, 2 or 2½ inches in diameter, was inserted into each drill hole, which was then filled with concrete grout. A concrete cap and bearing pad was installed at the top of each pier, to support a new deck structure.
The 1880 iron deck structure was removed and replaced with the new, wider one made up of 44 pre-cast, prestressed concrete panels. These were cantilevered outward on each side to allow for the extra width needed and a new safety walkway on either side. The color of the concrete was carefully matched to that of the viaduct stone.
To help maintain the viaduct’s historic character, the ornamental wrought-iron railing installed in 1880 was removed, repaired, and reinstalled on the face of the new deck, and supporting poles for the new electric overhead catenary were incorporated into it. The railing was color galvanized to match its original dark green color.
Thus refurbished for its new role in high-speed transportation, Captain McNeill’s 1835 structure stands ready to serve the twenty-first century. Surely few engineering works from the dawn of American railroading have stood the test of time so well.