Mill Avenue Bridges

Mill Avenue Bridges
Mill Avenue Bridge (built 1931) about 83 years old
Coordinates	33°26′00″N 111°56′30″W / 33.433335°N 111.941575°W / 33.433335; -111.941575Coordinates: 33°26′00″N 111°56′30″W / 33.433335°N 111.941575°W / 33.433335; -111.941575
Carries	Motor vehicles, pedestrians, and bicycles
Crosses	Tempe Town Lake
Locale	Tempe, Arizona
Maintained by	City of Tempe
History
Opened	Mill Avenue Bridge in August 1931 and the New Mill Avenue Bridge in 1994
Statistics
Toll	Free both ways

The Mill Avenue Bridges consist of two bridges that cross the Salt River in Tempe, Arizona at the north end of the shopping district on Mill Avenue. The first bridge opened in August 1931 and the second bridge opened in 1994.

The original bridge was built in 1931 but was not dedicated until 1 May 1933. The dedication celebration lasted for two days. Attending the celebration was Benjamin Baker Moeur, a former Tempe doctor and the governor at that time. The creation of this bridge replaced the Ash Avenue Bridge which was a one-lane highway bridge which was originally completed in 1913. It was demolished in 1991. In the Phoenix area, it was the sole crossing at the Salt River for some time.

Water flowed down the Salt River until the 1940s, when dams were constructed upstream. The water flow almost ceased, creating a dry river bed to support the growing Southwest. For years, southbound traffic used both lanes of the bridge, while northbound traffic utilized an unbridged crossing in the riverbed. (see note in the "talk" page)

Despite the Salt's being a dry river, water occasionally flowed. When reservoir levels got too high, the dams were required to release water, causing water to flow once more. Due to monsoon storms heavy rains would fall, and washes and street runoff emptied into the river. At such times the unbridged crossing was closed, and the bridge was opened to north- and southbound traffic, one lane in each direction.

The bridge faced many strong floods that raged through the Salt River Valley. In 1980 all but two of the bridged crossings on the Salt River were closed for safety reasons (principally erosion of the approaches) due to severe flooding. The Mill Avenue Bridge and one other bridge, the Central Avenue bridge in Phoenix were the only bridges that remained open. This was because they were structurally sound to stand up to the raging currents. Water hit the bridge at 200,000 cubic feet per second (5,700 m³/s), which far surpassed the expected strength of the bridge. In one 24-hour period during this flood, 92,000 vehicles crossed the bridge.