Shallow Groundwater & Sea Level Rise Impacts on Contaminated Sites in San Mateo County
Thanks to the work of researchers from Pathways Climate Institute, the San Francisco Estuary Institute, the University of California–Berkeley, and the U.S. Geological Survey (USGS), among others, scientific understanding of groundwater rise is rapidly advancing. Shallow groundwater is fresh water that is stored in soils below the ground surface. Shallow groundwater often contains pollutants from fertilizers, roadway runoff, and past and current industrial land uses. As sea levels rise in response to climate change, salty San Francisco Bay and Pacific Ocean water can move further inland, pushing the groundwater up through the soil in a process known as groundwater rise. The closer the groundwater table is to the ground’s surface, the more likely that heavy rains will cause flooding of roads, streets, and homes.
Beyond flooding, researchers have found that groundwater rise is likely to corrode and disrupt below-grade infrastructure, increase pollution entering the San Francisco Bay, mobilize soil contaminants, and raise the risk of soil liquefaction during earthquakes.
Many of the San Francisco Bay Area’s industrial sites are located along the San Francisco Bay shore. Rail stations, chemical manufacturing plants, landfills, recycling centers, refineries, military sites, and underground storage tanks have left legacy contaminants in the soil.
Our Concern: Shallow groundwater rise will mobilize contaminants at these legacy industrial sites and put residents at risk. East Palo Alto alone has about 50 industrial sites vulnerable to groundwater and sea level rise. Research shows that soil contaminants, such as volatile organic compounds (VOCs) found at legacy industrial sites, can travel into cracked storm and sanitary sewer pipes and enter nearby homes. Even remediated industrial sites, such as sites that have been "capped", should be revisited to assess contamination risk with groundwater and sea level rise and to protect residents from health impacts. Very little research has been completed to assess this risk in low-lying neighborhoods in San Mateo County. Without more data, it is difficult to drive policy change to clean up these toxic sites. The Peninsula Accountability for Contamination Team (PACT) is seeking partners to conduct research and understand more about these risks and the health impacts on our community.
We will be updating this page soon to provide more information on these risks to our community. For now, please take a look at SPUR and Nuestra Casa's report, Look Out Below: Groundwater rise impacts on East Palo Alto — a case study for equitable adaptation to learn more.