Pacifica sinkhole caused by waves undermining Beach Blvd
A sinkhole measuring 11 feet deep and 30 feet wide has opened below the sidewalk on Beach Blvd near Pacifica Pier, reports Julia Scott in the County Times.
Sinkholes are common along Beach Boulevard, although rarely do they go undetected for so long, according to Holmes. He said the city had already detected two smaller gaps developing under the sidewalk closer to Paloma Avenue, a quarter-mile away. The last big problem developed after the El Niño winter storms of 1998, when part of the seawall was so weak that it pulled away from the street and collapsed into the ocean. The water rushing in created a sinkhole about 30 feet north of the current one, according to Holmes.
...Public Works parks supervisor Ron Fasconda, explained that over time, the force of the waves had eroded the protective metal sheet at the base of Pacifica Pier. The water then worked its way behind the concrete-reinforced rocks piled up behind it and started digging the sand and dirt out from underneath the sidewalk. He said the repairs would only take a couple of days once begun.