Background/Objectives
Much attention has been paid to surface flooding as a result of sea level rise. Recent studies also indicate the potential for increasing groundwater elevations due to sea level rise. Especially concerning is mobilization of subsurface contaminants at chemically impacted sites currently being remediated or that have been closed but where residual contaminants remain. Future mobilization of contaminants caused by sea level rise can impact ground water in localized areas and surface water at nearby shorelines. Sustainable management of maritime infrastructure requires innovation – and must begin with adequately understanding both subsurface distribution of contaminants and potential changes to site conditions as a result of sea level rise.
Following delineation of near-shoreline soil contamination, the Port of Oakland is currently studying effects of vadose zone contaminants on groundwater quality at one of its environmentally challenged legacy sites. Specifically, soluble lead concentrations in near-shoreline soil, coupled with frequent high-amplitude groundwater elevation fluctuations, clearly have the potential to affect groundwater and surface water quality.
Approach/Activities
Northgate has prepared an investigation program to assess the presence of lead in groundwater. The program will also inform sustainable adaptation measures while sea levels continue to rise and potentially mobilize subject contaminants. Based on results of the initial investigation, a follow-up investigation was developed to assess existing conditions subject to tidal influences and to allow for assessing future scenarios including sea level rise.
Results/Lessons Learned
Analytical data indicate concerning concentrations of lead. Northgate is prepared to make recommendations regarding further evaluation of fate and transport mechanisms, to help formulate a conceptual site model. This approach may also help manage coastal sites where effects of sea level rise may result in threats to environmental and human health. They may additionally help with long-term financial planning (i.e., jurisdictions must set aside adequate resources in advance). Site-specific adaptive solutions may include continued monitoring, risk management, or mitigation by treatment, removal (excavation to a landfill or extraction), or cutoff/encapsulation.