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High Bridge
Completed in 1848, High Bridge is the oldest extant bridge in New York City. It originally had fifteen stone masonry arches spanning the Harlem River Valley and resembled an ancient Roman aqueduct.
The Old Croton Aqueduct was New York City's first major water supply system. Completed in 1842, project was a remarkable engineering achievement for its time, consisting of a masonry dam on the Croton River in northwestern Westchester County, a 40 ½-mile (65 km) long gravity-fed aqueduct, and two reservoirs in Manhattan. The Croton Water Supply System served as a prototype for subsequent water supply projects in New York City and throughout the world, including the Catskill and Delaware water supply systems, which presently supply about 90 percent of New York City's drinking water.

Before the city developed its first water supply system, its residents had to rely upon cisterns, wells, and natural springs. Sources of drinking water were most limited on Manhattan Island, which is surrounded by brackish water on all sides, and some water even had to be transported over from Brooklyn by boat. As the city's population grew, the task of obtaining fresh water became increasingly difficult. The over pumping of wells near the rivers led to salt water intrusion and unsanitary conditions caused some of the water sources to become polluted, quickly spreading diseases such as Asiatic cholera and yellow fever through the population. In 1832, a cholera epidemic killed 3,516 people, which represented nearly two percent of the city's population.

Manhattan's scarce water supplies also made it difficult to fight and contain fires. The rapid expansion of wood framed houses caused an increased amount of fires and the limited amount of water pressure made it difficult for firefighters to get water to the tops of buildings. In December 1835, a significant fire lasted for two days and destroyed 674 buildings in an area covering much of Lower Manhattan. These types of problems pressured New York City to search for a new supply of clean water.

As early as 1774, Christopher Colles proposed creating a reservoir in Lower Manhattan and filling it with water pumped from wells and Collect Pond by steam engines. Land was purchased along the east side of Broadway (between the present day Worth and Walker Streets) and a reservoir was constructed with a capacity of 20,000 hogsheads (approximately one million gallons). In 1776, water was pumped out of the reservoir through hollow pine logs buried under the streets but the project was abandoned during the Revolutionary War.

The search for a water source outside of Manhattan began in 1798 when Dr. Joseph Brown recommended to the Common Council that water from the Bronx River should be brought to the city. A detailed investigation of the Bronx River source was made the following year by civil engineer William Weston, but was not acted upon. Over the years, other sources considered included the Croton River, the Housatonic River in Connecticut, the Passaic River in New Jersey, and even the Hudson River (by building a large dam with locks for ships). Although the Bronx River was deemed the most feasible location, there were doubts on the total quantity of water that its watershed could produce.

Croton Aqueduct Gatehouse
Three gatehouses from the Croton Aqueduct remain on the Upper West Side of Manhattan: 113th Street at Amsterdam Avenue, 119th Street at Amsterdam Avenue, and 135th Street at Convent Avenue.

The city's first water supply system was constructed by the Manhattan Company, which was incorporated by an act of the State Legislature in 1799. Although the company held the exclusive right to distribute water to New York City, it was actually a clever ruse by Aaron Burr to create a bank to compete against the city’s only two banks—the First Bank of the United States and the Bank of New York—both of which were influenced by Alexander Hamilton. To raise the capital needed to construct the water works, the company was allowed to pursue other types of business ventures and it primarily focused on banking, later becoming the Chase Manhattan Bank. The Manhattan Company installed 25 miles (40 km) of wooden piping to serve Lower Manhattan, but only dug additional wells and did not seek sources of water beyond the island.

In 1822, the Common Council employed American civil engineer Canvas White to make a detailed survey and cost estimate for bringing water from the Bronx River to New York City. After receiving a favorable report about the feasibility two years later, a charter was given to the New York Water Works Company, but the company was unable to proceed with construction because its charter conflicted with the Sharon Canal Company, which one year earlier had been chartered and given the right to transport water to the city from the Housatonic River.

A Board of Water Commissioners was created in 1834 to "examine and consider all matters relative to supplying the city of New York with a sufficient quantity of pure and wholesome water for the use of its inhabitants." The commissioners were given the power to employ engineers and surveyors and the following April, voters approved the plan of the Board of Water Commissioners to construct an aqueduct from the Croton River. Major David B. Douglass served as the first chief engineer of the project and developed the preliminary plans and routes before he was succeeded by John B. Jervis in October 1836.

In 1837, New York City started to build its new water supply system. The project began with the construction of a 250-foot (76 m) wide and 55-foot (17 m) high dam approximately 6 miles (10 km) upstream of the mouth of the Croton River. The first significant masonry dam in the United States, the Old Croton Dam was built from square blocks of granite and cement and was 70 feet (21 m) wide at its base and 7 feet (2.1 m) wide at its top. It raised the level of the Croton River by 40 feet (12 m), creating a 5-mile (8 km) long reservoir that was 400 acres (161 ha) in size, had a capacity of 500 million gallons (1.8 million cubic meters), and was located at an elevation of 166 ½ feet (51 m) above sea level.

Built near ground level, the Old Croton Aqueduct was constructed from stone, brick, and hydraulic cement and covered with approximately three to four feet of earth to serve as protection from frost. The 7 feet 5 inch-(2.2 m) wide and 8 feet 5 ½ inch-(2.6 m) tall masonry conduit was shaped like a horseshoe and could transport approximately 90 million gallons (340,000 cubic meters) of water per day. Along the route, hills were cut through and valleys were filled in to keep the aqueduct at a constant slope of 13 ¼ inches per mile. Traversing other physical barriers required the construction of sixteen tunnels ranging from 160 to 1,264 feet (49-385 m) in length and 114 culverts ranging from 1 ½ to 25 feet (0.5-7.6 m) in length. Near Ossining, a large arch bridge with a span of 88 feet (27 m) was built over the Sing Sing Kill. Ventilators were placed along the aqueduct every mile (1.6 km) to supply fresh air inside the tunnel and six waste weirs were built along the aqueduct to allow surplus water to be discharged.

High Bridge
In 1927, five of the stone masonry arches on High Bridge were replaced with a single steel arch to improve navigation for ships on the Harlem River.

At the point where the Old Croton Aqueduct crossed the Harlem River, a monumental structure resembling an ancient Roman aqueduct was built. Jervis originally prepared plans and cost estimates for both high and low bridge crossings of the Harlem River valley and selected a low bridge with a single arch because it would be half the cost and easier to build. However, before construction began, the State Legislature passed a law requiring the crown of any bridge arches to be at least 100 feet (30 m) above the river. A tunnel crossing was also investigated, but when faced with the uncertainties in the associated cost with tunneling through rock, Jervis was forced to redesign the bridge in accordance with the new law.

High Bridge (officially Aqueduct Bridge) is the oldest extant bridge in New York City. Completed in May 1848 (six years after the aqueduct), the 1,450-foot (442 m) long and 140-foot (43 m) high structure originally consisted of fifteen stone masonry arches across the Harlem River valley, eight of which had spans of 80 feet (24 m) and seven of which had spans of 50 feet (15 m). Before the High Bridge was completed, water in the aqueduct crossed the Harlem River valley in a temporary 36-inch (91 cm) diameter inverted siphon. Water was not carried in a masonry conduit across the bridge to prevent leakage because the freezing and expansion of water could damage the structure below. Two 36-inch (91 cm) diameter cast iron pipes were initially used on the bridge; a 90-inch (2.2 m) diameter pipe was added in December 1861 to provide increased capacity.

The 185-foot (56 m) tall High Bridge Water Tower stands next to the west end of the Aqueduct Bridge and was also built after the Old Croton Aqueduct opened. Water was pumped into an 10.8-million gallon (40,900 cubic meter) reservoir near the base of the tower (completed in 1869, now the site of the swimming pool in Highbridge Park) and pumped up to a 47,000-gallon (178 cubic meter) tank at the top of the water tower (completed in 1872) to provide water pressure to parts of upper Manhattan elevated above the aqueduct. From the High Bridge, the Old Croton Aqueduct continued south down Amsterdam Avenue; an inverted siphon was used to cross the Manhattan Valley in Harlem.

Two reservoirs were constructed near the terminus of the aqueduct in Manhattan. The York Hill Reservoir (the receiving reservoir) covered an area of 31 acres (13 ha), had a capacity of 150 million gallons (568,000 cubic meters), and was located between Sixth and Seventh Avenues and 79th and 86th Streets (now the site of the Great Lawn in Central Park). From this point, two three-foot (91 cm) diameter pipes carried the water south under Fifth Avenue to the Murray Hill Reservoir (the distributing reservoir). Located on the west side of Fifth Avenue between 40th and 42nd Streets (the current site of the New York Library), the distributing reservoir covered an area of four acres (1.6 ha) and had a capacity of 20 million gallons (76,000 cubic meters). The walls of the reservoir were decorated in Egyptian cornice and had an average elevation of 44 ½ feet (14 m) above the street. Water was then circulated from the Murray Hill Reservoir throughout the city in a network of 170 miles (274 km) of pipes ranging in size from a diameter of 6 to 36 inches (15 to 91 cm).

Central Park Reservoir
The Central Park Reservoir opened in 1862, expanding the capacity of the original receiving reservoir located on the site of the Great Lawn.

On the morning of June 22, 1842, water first began flowing through the Old Croton Aqueduct and to celebrate the occasion, the water commissioners and engineers took a unique ride through the aqueduct on the "Croton Maid," a four-person boat that was sixteen feet (4.8 m) long and four feet (1.2 m) wide, specifically built for the purpose. Traveling at a leisurely speed of about two miles per hour (3.2 kmh), the crew took turns riding in the boat and arrived at the High Bridge the following afternoon. On June 27th, the boat was carried across the Harlem River and placed back in the aqueduct, where it continued its journey through the aqueduct, arriving at the York Hill Reservoir to a greeting of a salute of by 38 artillery guns.

Water began to fill the Murray Hill Reservoir on 42nd Street on July 4, 1842. New York City officially celebrated the completion of the Croton Water Supply System on October 14th when a 50-foot (15 m) high geyser crystal pure Croton water, transported from Westchester County, gushed forth from a fountain in City Hall Park and was marked with a hundred gun salute. Citizens were given a day off from work and there was a long parade that proceeded from the Battery to Union Square and then to City Hall Park.

While the Croton Aqueduct provided a reliable source of water, New York City continued to grow, with its population tripling between 1840 and 1870. In 1885, construction began on a larger aqueduct to carry water to the city, which was placed into service in July 1890. The New Croton Aqueduct had a capacity of 340 million gallons (1.2 million cubic meters) per day, tripling the capacity of the original aqueduct, and still remains in use today. Constructed as a straight tunnel for nearly all of its 31-mile (50 km) length to the 135th Street Gatehouse, the New Croton Aqueduct included a seven-mile (11 km) long inverted siphon across the Harlem River tunneled with diamond drill borings that descended to a depth of 300 feet (91 m) below the surface.

Beginning in 1858, a new reservoir was also constructed in Manhattan with a capacity of 1.03 billion gallons (3.9 million cubic meters), covering an area of 96 acres (39 ha). In 1852, the site for the new reservoir was selected between Fifth and Seventh Avenues and 86th and 96th Street. With Central Park created the following year, the reservoir was laid out to follow the natural contours of the land instead of having a rectangular shape. The reservoir was completed on August 19, 1862 and called "Manhattan Lake." The rectangular York Hill Reservoir was later drained in 1930 and converted into the Great Lawn and Turtle Pond. The Murray Hill Reservoir was also removed beginning in the spring of 1899 to make room for the New York Public Library, which opened in 1911.

New Croton Dam
The New Croton Dam (Cornell Dam) was the highest dam built at the time of its construction.

To further increase the yield of the Croton watershed, a larger dam was built on the Croton River approximately three miles (5 km) downstream of the original dam on the property of A.B. Cornell. Construction of the New Croton Dam, also known as the Cornell Dam, began in September 1892 and was not completed until January 1906. A masonry gravity dam, the New Croton Dam stands 297 feet (91 m) above its rock foundation, which is 130 feet (40 m) below the riverbed. The masonry is 206 (63 m) feet thick at the base and 15 feet (4.5 m) wide at the top. The dam is 1,600 feet (488 m) long and has a 1,000-foot (305 m) long curved spillway with a stepped chute designed to maximize energy dissipation. The New Croton Dam created the 19-mile (31 km) long New Croton Reservoir, submerging the Old Croton Dam and necessitating the displacement of hundreds of families.

In the 1920s, the United States Army Corps of Engineers expressed concerns that the arches of the High Bridge were too narrow and posed obstructions to large ships and barges navigating the Harlem River. At that time, water no longer flowed across the pipes of the Old Croton Aqueduct, instead using the newer tunnel drilled beneath the Harlem River. To address the navigation issue, the New York City Commissioner of Plant and Structures and the Board of Estimate recommended the entire removal of the High Bridge. In 1923, the ASCE New York Section and the New York Chapter of the American Institute of Architects made efforts to preserve the historic structure of the High Bridge. The two organizations drew up plans and prepared cost estimates for alternatives that could save as much as possible of the original structure and rebuild the river portion so as to remove the obstructions to navigation. In 1927, the City accepted a plan to preserve the bridge and replaced five of the original arches across the Harlem River with a single steel arch.

The Old Croton Aqueduct ran alongside the Hudson River through the villages of Ossining, Briarcliff Manor, Sleepy Hollow, Tarrytown, Irvington, Ardsley-on-Hudson, Dobbs Ferry, Hastings-on-Hudson, and the city of Yonkers before entering the Bronx at Van Cortlandt Park. Today, much of the aqueduct's route through Westchester County has been preserved as hiking trails through the creation of the Old Croton Aqueduct State Historic Park in 1968.

The Croton Water Supply System was designated as a National Historic Civil Engineering Landmark by ASCE on October 16, 1975. A bronze plaque marking the landmark designation was mounted on the gate house along Croton Dam Road near the top of the spillway. The Croton Aqueduct was added to the National Register of Historic Places in 1974 and was designated as a National Historic Landmark in 1992.

New Croton Dam 100th Anniversary

New Croton Dam Plaque Dedication

The ASCE Lower Hudson Valley Branch unveiled a bronze plaque commemorating the 100th year of service of the New Croton Dam (also known as the Cornell Dam) at Croton Gorge Park in Cortlandt on October 9, 2006. Built between 1893 and 1906, the New Croton Dam was a remarkable civil engineering achievement and part of an expansion of the Croton Water Supply System. It became the highest dam yet built at its time of construction.

The dam remains the largest of cut stone masonry construction (as compared to concrete construction). With its curved, stepped spillway spanned by a steel arch bridge and situated at the edge of a 97-acre (39 ha) park, the New Croton Dam is one of the most beautiful spots of the Lower Hudson Valley area. Croton Gorge Park serves as the trailhead for the Old Croton Aqueduct State Historic Park, a 26.2-mile (42 km) long linear park that follows the route of the Old Croton Aqueduct through Westchester County to the New York City line.