Work went on day and night after that sinkhole began to open at Alvarado Boulevard and New Haven Street last Wednesday.
It grew to a size of 35 feet by 40 feet.
Crews also needed to replace utility lines before they filled the hole.
Officials don't know what caused the sinkhole to develop.
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Update: Sink hole on Alvarado Blvd is roughly 10ft x 12ft. Depth unknown. Area remains blocked off to traffic. pic.twitter.com/HZlIObRUbv— City of Union City (@UnionCity_Gov) October 14, 2015
sinkhole in front of AMS...the world is ending yo pic.twitter.com/2b5SZcdDhV— C J (@christinegolfo) October 14, 2015
Huge sinkhole near my old elementary school in Union City. NBD right? pic.twitter.com/tnjTwo7I2M— Marjan Rajabi (@_mar920) October 14, 2015
Northbound lanes on Alvarado Blvd are closed btwn Fair Ranch Rd & Fredi St until further notice due to a sink hole. PW crews are on scene.— City of Union City (@UnionCity_Gov) October 14, 2015
Correction:Westbound lane on Alvarado Blvd is closed btwn Fair Ranch Rd & New Haven St until further notice.Crews are monitoring a sink hole— City of Union City (@UnionCity_Gov) October 14, 2015