Climate Change and Remediation: Droughts Inhibit Site Characterization and Monitoring of Contaminated Sites

Monitoring of groundwater at contaminated sites has become more difficult in drought-stricken areas due to the fact that drought conditions may decrease groundwater elevation causing monitoring wells to go dry, and possibly result in changes in groundwater chemistry and the volume or presence of NAPL.  These conditions can impair hydrologists’ abilities to properly characterize sites and lead to unrealistic understanding of subsurface conditions that may translate into poor decision making and unexpected costs to clients. The drought experienced in the Southwest United States starting in 2010 is part of a hydraulic cycle related to El Niño Southern Oscillation in the Pacific Ocean, and is similar to conditions observed during previous dry periods. However, the National Climate Assessment indicates that projected changes in temperature and precipitation for this region will exacerbate the effects of these shorter term climate cycles, further inhibiting our ability to monitor contamination in the subsurface and increasing uncertainty when planning remediation strategies.

This study examines the effects of the recent drought on groundwater monitoring at four sites in Texas and California: two hydrocarbon contaminated sites in south Texas, one hydrocarbon contaminated site in southern California, and one hazardous waste disposal facility in southern California.  At the two Texas sites, water level decreases resulted in an approximate loss of up to 30% of the monitoring well network. Conditions were more pronounced at the southern California sites, with water level decreases resulting in up to 55% loss of the monitoring well network.  At all four of these sites, the decrease in the water table caused the loss of important spatial and temporal site characterization data. The results of this study highlight the need to consider how short-term and long-term climate change may affect efforts to characterize and remediate contaminated groundwater.