Rain causes headaches along Pacifica coast
It is early in the winter 2010 season and already unmistakable signs of fresh groundwater erosion are visible beneath the buildings along Esplanade Avenue in Pacifica. Groundwater, water flowing underground, weakens and separates the layers of soil, sand and clay beneath the buildings, and washes away the surface of bluff. Given enough time groundwater will undermine and destroy the buildings just as surely as winter storms surf.
The dangers to the buildings on Esplanade Ave of uncontrolled groundwater drainage have been known since almost the beginning. A project including channels to control and divert groundwater has been completed at 360 Esplanade, but similar work at 330 Esplanade Ave was abandoned unfinished. (For an early reference to groundwater risks see Esplanade Update – Sunday February 7, 2010.)
The owners, community, and city of Pacifica need to remain alert of the dangers posed to the unprotected buildings along Esplanade Ave. Those buildings, in turn, continue threaten the road, infrastructure and well being of the residents in the nearby neighborhood.
Groundwater Seepage Example
Darkened earth and soil, stained by fresh groundwater, is visible in the following photos of the bluff below the south end of 330 Esplanade Ave. To the left is the flaked and shredded unfinished concrete and soil nail project intended to protect that vacant apartment building. These were taken following a dry period, but the recent storms are starting to make a difference.
310 Esplanade south: November 27, 2010 versus August 15, 2010
The still-occupied apartment building at 310 Esplanade Avenue in Pacifica stands atop a sand and soil bluff that shows significant fresh groundwater-related damage. The vacant buildings just south, 320 and 330 Esplanade are also showing recent weather-related erosion. The base of the bluffs are armored with about 30 feet of massive boulders, and so far the winter storms have not produced surf approaching that height.
In this view we see the south end of 310 Esplanade and neighboring, vacant 320 Esplanade.
310 Esplanade south: detail view
The earth – soil, sand and clay – beneath the protruding drainage pipe has receded since August.
310 Esplanade north erosion, August 15 and November 27
The north end of 310 Esplanade is next to the open “dog park”. More threatening, fresh erosion is happening here, too.
310 Esplanade north erosion detail:
An area of more than 20 square feet has fallen away from the bluff, as shown in these photos. The amount of earth (sand / dirt / clay) that has fallen seems small so far.
11/24: Rain causes headaches along Pacifica coast
The press continues to cover the Esplanade Ave story. KGO-TV, San Francisco (ABC) ran the story Rain causes headaches along Pacifica coast: http://abclocal.go.com/kgo/story?section=news/local/peninsula&id=7806869
For a complete chronology and links to many more photos see Evacuation underway at 330 Esplanade:
See all of my pictures of the Esplanade crisis: