Question:  The Astor Bridge carries State Road 40 over a river that his how long?

Passages:
State Road 40 (SR 40) is an east–west route across central Florida, running from US 41 in Rainbow Lakes Estates eastwards through Ocala over the Ocklawaha River and bridge and through the heart of the Ocala National Forest to State Road A1A in Ormond Beach.  Names of the road include Silver Springs Boulevard in Ocala, Fort Brooks Road from Silver Springs through Astor, Butler Road in Astor, and Granada Boulevard in Ormond Beach.  Former sections in Ormond Beach are named "Old Tomoka Road" and "Old Tomoka Avenue." The Bert Dosh Memorial Bridge, also known as the Delks Bluff Bridge, carries State Road 40 over the Ocklawaha River in north-central Florida, east of Silver Springs. The Astor Bridge is a single-leaf bascule bridge located in Astor, Florida that carries State Road 40 over the St. Johns River.  The first bridge on the site was built in 1926; the current bridge dates from 1980. The Sir Leo Hielscher Bridges are a side-by-side pair of road bridges on the Gateway Motorway (M1), which skirts the eastern suburbs of Brisbane, Queensland, Australia.  The western bridge carries traffic to the north and the eastern bridge carries traffic to the south.  They are the most eastern crossing of the Brisbane River, the closest to Moreton Bay, crossing at the Quarries Reach, between Eagle Farm and Murarrie.  The original bridge (formerly named the Gateway Bridge) was opened on 11 January 1986 and cost A$92 million to build.  The duplicate bridge was opened in May 2010, and cost $350 million. The Third Avenue Bridge carries southbound road traffic on Third Avenue over the Harlem River, connecting the boroughs of Manhattan and the Bronx in New York City.  It once carried southbound New York State Route 1A.  The Third Avenue Bridge carries traffic south from Third Avenue, East 135th Street, Bruckner Boulevard, and Lincoln Avenue in the Bronx, to East 128th Street, East 129th Street, Lexington Avenue, and the Harlem River Drive in Manhattan, traveling over the Metro-North Railroad Oak Point Link, the Harlem River, and Harlem River Drive.  The bridge was formerly bidirectional, but converted to one-way operation southbound on August 5, 1941 on the same day the Willis Avenue Bridge was similarly converted to one-way northbound. The Millard E. Tydings Memorial Bridge carries Interstate 95 (I-95) over the Susquehanna River between Cecil County and Harford County, Maryland.  The toll bridge carries 29 million vehicles annually.  It is upstream from the Thomas J. Hatem Memorial Bridge, which carries the parallel U.S. Route 40 (US 40). The Savanna–Sabula Bridge is a truss bridge and causeway crossing the Mississippi River and connecting the city of Savanna, Illinois with the island city of Sabula, Iowa.  The bridge carries U.S. Route 52 over the river.  It is also the terminus of both Iowa Highway 64 and Illinois Route 64.  The bridge carries an average of 2,400 vehicles daily as of 2005. The St. Johns River (Spanish: "Río San Juan" ) is the longest river in the U.S. state of Florida and its most significant one for commercial and recreational use.  At 310 mi long, it winds through or borders twelve counties, three of which are the state's largest.  The drop in elevation from headwaters to mouth is less than 30 ft ; like most Florida waterways, the St. Johns has a very low flow rate 0.3 mph and is often described as "lazy".  Popular belief in the St. Johns area holds that it is one of the few rivers that flow north, although north-flowing rivers are common.  Numerous lakes are formed by the river or flow into it, but as a river its widest point is nearly 3 mi across.  The narrowest point is in the headwaters, an unnavigable marsh in Indian River County.  The St. Johns drainage basin of 8840 sqmi includes some of Florida's major wetlands.  It is separated into three major basins and two associated watersheds for Lake George and the Ocklawaha River, all managed by the St. Johns River Water Management District. Volusia ( , ) is an unincorporated community in Volusia County, Florida, United States on the eastern shore of the St. Johns River, about three miles south of Lake George and across the river from the town of Astor in Lake County.  Volusia is one of the oldest European settlements in Florida.  The main route through the town is State Road 40, which crosses the St. Johns on the Astor Bridge. The Granada Bridge is a high-clearance bridge that spans the Halifax River and Intracoastal Waterway, linking the mainland and beach peninsula parts of Ormond Beach, Volusia County, Florida.  Granada Bridge carries four lanes of State Road 40 and Granada Blvd.  The Casements, along with City Hall Plaza, Fortunato Park, and Riverbridge Park reside at the four corners of Ormond Beach's Granada Bridge, which give their collective name to the annual "Four Corners Festival" in Ormond Beach.

Supporting sentences:
The Astor Bridge is a single-leaf bascule bridge located in Astor, Florida that carries State Road 40 over the St. Johns River. The St. Johns River (Spanish: "Río San Juan" ) is the longest river in the U.S. state of Florida and its most significant one for commercial and recreational use.  At 310 mi long, it winds through or borders twelve counties, three of which are the state's largest.