Development and deployment of an ultrasonic groundwater seepage meter: a reliable way to measure groundwater seepage

Abstract

Submarine groundwater discharge can significantly influence the near shore transport of chemicals into surface waters. Quantification of the sources and rates of such discharge is critical to development of management strategies. Quantification requires a groundwater seepage meter that provides continuous measurements at high resolutions over an extended period of time. An ultrasonic flow meter has been developed for such measurements in the subsurface environment. Connected to a collection funnel the meter houses two piezoelectric transducers mounted at opposite ends of a cylindrical flow tube. By monitoring the perturbation of fluid flow on the propagation of sound waves inside the flow tube, the ultrasonic meter can measure both forward and reverse fluid flows in real time. Laboratory and field calibrations show that the ultrasonic meter can resolve groundwater discharge on the order of 0.1 /spl mu/m/s and is sufficiently robust for deployment in the field for several days. A parallel effort has applied a direct contact resistivity probe used by divers to identify areas of groundwater seepage. These tools have been applied to identify areas of groundwater seepage. These tools have been applied to quantify ground water seepage and associated contaminated loads from landfills, Superfund/industrial sites, and agricultural sites and to develop nutrient budgets for computer modeling. These techniques have been used in deployments with the US Navy, Battelle Labs, the Suffolk County Health Services and the United Nations. Equipment has now been developed that integrates this meter with an automated sampling device that can be deployed for 4 days and collect seepage flow regulated samples.