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The Trident Probe and Ultra Seep System are two tools that were developed to directly assess the flux of COCs in groundwater discharging through sediment into the overlying surface water. These tools were demonstrated under ESTCP Project ER-200422 to be effective at locating areas where groundwater is discharging and being able to sample the discharge water for contaminants.
For long term monitoring at active cap remedial sites, diffusive flux can be measured using passive samplers, advective flux via groundwater requires tools that can directly measure both the velocity rate passing through the underlying contaminated sediments and remediated surface sediments, as well as capture water samples to measure the levels of COCs.
The Trident probe is a direct-push, integrated temperature sensor, conductivity sensor, grain-size sensor and porewater sampler developed to screen sites for areas where groundwater may be discharging to a surface water body. Differences in observed conductivity and temperature indicate areas where groundwater discharge is occurring. The integral porewater sampler can be used to rapidly confirm the presence of groundwater constituents and map the subsurface distribution of contaminants of concern.
The UltraSeep system is an integrated seepage meter and water sampling system for quantifying discharge rates and chemical loading from groundwater flow to coastal waters. Traditional seepage technology was modified and improved to include automated multiple sample collection and continuous flow detection with ultrasonic flow meters. The UltraSeep makes direct measurements of advective flux and contaminant concentration at a particular location.
The data produced are time series, over tidal cycles of groundwater flow contaminant concentration, and associated sensor data. These data allow an accurate determination of the presence or absence of groundwater flow and associated contaminant flux from a terrestrial site into a bay or estuary.
Both units are available commercially (Zebra-Tech; CMA); a detailed description of the hardware, protocols and procedures is available online (SPAWAR Technical Report 1902)
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