Pacifica has been struggling to hold up under nasty El Niño conditions. First off, the pier was closed last week due to massive waves, and now those waves have created a sizable sinkhole.

The Chronicle reports that the collapse occurred yesterday amid nearly 20-foot waves, with the National Weather Service issuing a high surf warning through 4 a.m. this morning and a coastal-flooding warning through 7 a.m.

But the Pacifica Department of Public Works wasn't blindsided by conditions, as officials told ABC7. Crews had large eight- to 10-ton boulders on hand nearby to fill in the hole.

Crews have been working on the sinkhole all day, attempting to preserve whatever material is still available for the job. "We're going to reassess the condition and come up with a final design on how to fix this," Pacifica Department of Public Works Director Van Ocamp told CBS SF.

Previously: Poseidon Looses Wrath, Closes Pacifica Pier