Union City Sinkhole Repair to Last Indefinitely

Repairs to a sewer line below a Union City intersection where a large sinkhole opened up earlier this month will go on indefinitely, keeping at least one lane of the street closed, Union Sanitary District officials said Wednesday.

The 33-inch-diameter sewer line running 20 feet below Alvarado Boulevard has been difficult to access because of ground conditions there.

The first step in repairs will be for crews to dig three wells, each 30 feet deep and 2 feet wide, to pump groundwater out, sanitary district officials said. One lane in each direction of Alvarado Boulevard between Fair Ranch Road and New Haven Street reopened last week but the other two remain closed as repairs go on.

The intersection of Alvarado and New Haven was closed for about a week after the roughly 10- by 12-foot sinkhole opened up in the center of the intersection on the afternoon of Oct. 14.

Crews excavated the hole to roughly 25 by 25 feet to make repairs to a buried water main that burst when the ground collapsed.

Once repairs to that main, which runs about 10 feet above the sewer line, were complete, crews backfilled the hole to stabilize the pavement and reopen one traffic lane, according to the sanitary district. Determining the extent of the damage has been challenging because of unstable soil conditions and high levels of groundwater in the area.

Once the groundwater is pumped out, crews will be able to better assess the damage and determine how to make repairs, sanitary district officials said. Sewer service has been routed through a temporary aboveground bypass line and the sanitary district is working to complete an underground bypass line.

Once that line is ready, estimated to be in the middle of next week, sanitary district officials hope to open another eastbound lane of Alvarado.

“Our objective in this project is to protect the safety of motorists and others in the area while performing a repair that will be permanent and effective,” Union Sanitary District general manager Paul Eldridge said. “This work has been our number one priority, and it will remain our priority until the repair is complete and the street is fully reopened,” Eldridge said.

Bay City News

Photo of repair work on Oct. 16 courtesy Alameda County Water Department