SAN DIEGO (KGTV) - A construction crew working on a retaining wall for a residential tower across from the UTC mall alerted the city to a potential hole under Genesee Avenue.
The crews for Garden Communities stopped the work because they could not drill deep enough into the street without hitting an open space.
In an environmental notice, the city disclosed what it's calling a "geotechnical void".
"They were driving nails in the ground to support, to build a retaining wall, but the ground wasn't hard enough," said geologist Pat Abbott.
The potential void is located on Genesee Avenue just south of La Jolla Village Drive. Thousands of cars pass that intersection daily, and crews are currently building the above-ground trolley line down the middle of the street to terminate at the Westfield UTC mall.
City spokesman Alec Phillipp said a preliminary geotechnical analysis found no danger to the public.
Abbott said the void would not be seismic, but is likely manmade from a prior generation. The area was used as a marine training ground around World War II so some possibilities include bunkers or storage basements. Abbott said old sewers or infrastructure could also be the culprit.
"City maps have improved through time," he said. "Way back in the old days, these were just pieces of paper in file cabinets which can be thrown away or destroyed."
Irene McCormack, a spokeswoman for the San Diego Association of Governments overseeing the trolley extension, said the agency knew about the void and that it poses no threat to the trolley.
Phillipp said the city's initial investigation didn't locate a void. He said a final analysis would be complete likely in October.
Garden Communities did not immediately respond to a request for comment.