Title: Introduction Text: This Web Tool provides an overview of two innovative technologies for monitoring the migration of contaminants from groundwater to coastal surface water. The Trident Probe and the UltraSeep System were developed by the Navy and Cornell University to provide a direct measurement of groundwater discharge rates and chemical loading rates to surface water. These technologies offer a significant improvement over the use of uncertain predictions from modeling and terrestrial monitoring well results. The improved site knowledge gained from direct measurement will allow for the selection of more effective and often less expensive remedial alternatives in coastal areas.

Title: Coastal Contamination Migration Concepts Text: This conceptual model illustrates the processes that drive migration of contaminants from groundwater to coastal surface water. The primary driver for groundwater seepage (or migration) in near-shore environments is often the hydraulic gradient in the terrestrial aquifer. The hydraulic gradient is the pressure difference between two points caused by different water levels, which drives the flow of the groundwater. However, groundwater circulation induced by tidal stages also may contribute significantly to seepage. In coastal areas with strong tidal fluctuations, the movement of seawater into the aquifer may create a tidal mixing zone. This zone may be important in controlling the exchange of groundwater at the interface due to a process referred to as “tidal pumping.” Tidal pumping occurs when seawater mixes with groundwater at high tide. As the tide recedes, the seawater and groundwater are then drawn out into the coastal waters. Because this process repeats with every tidal cycle, there is potential for large volumes of groundwater to be extracted over time.

Title: Potential Impact of Trident Probe and UltraSeep Text: The Trident Probe and the UltraSeep System are direct measurement technologies for the groundwater and surface water interface and offer an integrated approach to quantify natural attenuation rates and human health and ecological risk. The two tools are typically applied as an integrated system. The Trident Probe is used first to survey potential groundwater discharge zones based on differences in conductivity and temperature and to map the subsurface distribution of contaminants of concern (CoCs) in relation to the identified discharge zone. The UltraSeep System is applied next in key areas to quantify the groundwater discharge rates and CoC concentrations.

Title: Trident Probe Text: The Trident Probe is a multi-sensor sampling device developed to screen for groundwater discharge into surface water and to map the subsurface distribution of CoCs in relation to the discharge zones identified. The differences observed in temperature and conductivity along the bottom of an ocean, estuary, or bay help to indicate areas where groundwater discharge may be occurring. The Trident Probe allows large areas to be rapidly mapped to identify these areas of contrast for temperature and conductivity. The integral pore water sampler can also be used to confirm the presence of freshwater or contaminants of concern. Conductivity - detects contrast in salinity and/or clay content in unconsolidated sediments. Temperature - detects groundwater by thermal contrast with surface water. Porewater Sampler - allows contaminant characterization and detection of groundwater specific tracers.

Title: Trident Probe Components (1 of 3) Text: The major components of the Trident system include: Water sampling probe Standard filter cartridge Sand pack filter system Conductivity and temperature sensing probe Reference conductivity and temperature probe Depth control plate Global Positioning System (GPS) unit with antenna Deck unit Latest version of TridentTalk (trademarked) software 12 meter total length push rod, in 2 meter sections The depth rating for the Trident Probe conductivity and temperature sensors is 150 meters. Temperature resolution is 0.001 deg C. Conductivity output is given as specific conductance at 25 deg C with a resolution of 0.01 mS/cm. The conductivity range is 0 to 80 mS/cm. Click here for more detailed specifications on the Trident Probe.

Title: Sand Pack Adapter (2 of 3) Text: The latest version of the porewater sampler has a sand-pack adapter that allows the collection of porewater samples in fine-grained sediments.

Title: Trident Probe Deck Unit (3 of 3) Text: The Trident Probe is connected to a deck unit on the surface through a bundled cable that includes the temperature and conductivity signal wires, sampling tube, and pneumatic air-hammer hose. The deck unit includes a laptop that integrates the temperature and conductivity signals with readings from a GPS sensor mounted on the probe. The laptop uses a specialized software package Trident Talk (trademarked) to collect, store, and display these signals and to apply calibration and temperature corrections. The data then can be reviewed in numeric format or displayed spatially using geographic information system software such as AGIS (trademarked). The spatial display capability provides for real-time evaluation of the most likely groundwater discharge areas based on temperature and conductivity contrasts.

Title: Deployment of the Trident Probe (1 of 2) Text: A Trident Probe survey is conducted by inserting the probe into the bottom of the ocean, estuary, or bay. A submersible air-hammer is provided to assist in driving the probe into the sediment. The Trident Probe can be deployed in several ways depending on the depth of the site. These methods include: Shallow (0 to 3 ft): The operator walks or wades to the sampling point and manually pushes the probe to the desired depth. Without the air-hammer, the probe can be pushed by hand to about 1 ft (30 cm). Mid-depth (2 to 50 ft): The probe is easily deployed from a small boat using an aluminum push rod, along with the air-hammer. The push rod can be lengthened in 6.6 ft (2 m) increments to a total length of 50 ft (15 m). The boat must be well anchored to minimize lateral loading on the probe. Deep (greater than 50 ft): Beyond the reach of the push rod, the probe can be deployed by a diver or attached to a landing frame.

Title: Deployment of the Trident Probe (2 of 2) Text: This video shows deployment of the Trident Probe by a diver. The video illustrates the use of the air-hammer to drive the probe into the sediments.

Title: UltraSeep System Text: The UltraSeep System is an integrated seepage meter and water sampling system for quantifying discharge rates and chemical loading from groundwater to coastal waters. This innovative technology combines automated sample collection with continuous flow detection. The data can be produced over a tidal cycle to show a time series of groundwater flow, contaminant concentration, and associated sensor data. This information allows a direct measurement of advective flux and contaminant concentration at a sampling point.

Title: Components of UltraSeep System Text: The major components include: Battery: A submersible battery housing with three 12 V batteries allows the system to run continuously for up to four days. Funnel: A stainless steel, open-bottomed chamber to funnel the seepage water to on-board sensors. Water Sampler: Up to 10 seepage water samples can be collected in 1-liter sample bags. The samples are collected with a low-flow peristaltic pump in proportion to the measured discharge rate. On-Board Sensors: Temperature and conductivity measurements are collected by on-board sensors and stored in the data logger/control unit that also controls water sampling events. Ultrasonic Flow Meter: A flow meter is used to continuously measure the specific discharge or recharge in the range of approximately 1 to 1000 cm/day. Click here for detailed specifications for the UltraSeep System.

Title: UltraSeep Water Sampling Schematic Text: At coastal sites, a typical UltraSeep deployment runs over a 12 to 24 hour period to capture an entire semi-diurnal or diurnal tidal cycle. During this period, the seepage rate is continuously monitored and recorded by the data logger/control unit. A unique feature of the UltraSeep System is that the water samples are collected in proportion to the seepage rate, enabling the direct quantification of the chemical loading associated with the groundwater discharge. The control unit evaluates the flow sensor signal over a five minute averaging time and determines the current seepage rate. If the seepage rate is positive, the water sampler pump is activated and the pumping rate is set at the current seepage rate. This process is repeated every five minutes and the pump flow rate is adjusted accordingly. The pump flow rates range from 0 to 13 ml/min at steps of 1 ml/min. The control unit switches samples after the bag is full based on volume pumped and/or after a user-defined sampling interval.

Title: Deployment of the UltraSeep System (1 of 2) Text: As shown in this video, the UltraSeep System is lowered to the bottom either directly from a boat or by divers using a lift-bag. Once the unit is settled on the bottom, the seal is checked by divers. A period of 2 to 3 hours is generally allowed to ensure that any response associated with the deployment activities has dissipated (e.g. sediment suspension in video). The control unit then initiates data logging and sample collection. At the end of the deployment, the meter is recovered using either a lift line to the boat or diver assistance.

Title: Deployment of the UltraSeep System (2 of 2) Text: The UltraSeep System can be deployed in several configurations: Flow Only: Measures rate of discharge/recharge. Flow and Sensors: Measures rate of discharge/recharge and measures temperature and conductivity. Flow, Sensors, and Sampling: Measures rate of discharge/ recharge; measures temperature and conductivity; collects water samples to quantify contaminant concentrations.

Title: Advantages of Trident and UltraSeep (1 of 3) Text: Allows direct sampling at the groundwater/surface water interface. Allows mapping of the groundwater discharge zone. Allows collection of pore water and seepage water samples. Allows continuous measurement of discharge flow rates. Demonstrated and validated by ESTCP at Navy sites. Independent technical evaluation of the technologies is planned under the California EPA Hazardous Waste Technology Demonstration Program.

Title: Limitations of Trident Probe (2 of 3) Text: Trident is limited to water depths of about 50 feet for push-pole deployment. Conductivity contrast can be confounded by sediment characteristics (e.g. clay content). Temperature contrast can be confounded by other influences such as thermoclines, direct radiation, and shading. Pore water collection may be limited in very fine sediments. Push depth into sediment may be limited by substrate. Trident is not amenable to rocky, rip-rap, coral or other hard bottom conditions.

Title: Limitations of UltraSeep System (3 of 3) Text: UltraSeep has a limited range of water depths from a minimum of 3.3 ft (1 m) to a maximum of 230 ft (70 m). Sample volume collected is limited by flow rate (low flow rates may result in insufficient volume for analysis). Samples may be a mixture of surface water and discharge water; funnel initially captures ~5 L of surface water and this volume must be displaced by discharge water. This factor can be corrected for in post-processing of the results. UltraSeep is not amenable to use in rocky, rip-rap, coral or other hard bottom conditions.

Title: Cost Information (1 of 2) Text: The cost of an integrated Trident/UltraSeep survey is expected to be on the order of $120,000 for a typical site. This cost is based on the site scale and design parameters shown in the table presented here. A breakout of the costs for labor and non-labor is shown on the following slide.

Title: Cost Information (2 of 2) Text: This table shows the cost breakout for a typical Trident/UltraSeep survey. Labor costs, including reporting and project management, typically account for approximately 70 percent of the costs while non-labor costs, consisting of equipment, materials, and travel, account for about 30 percent of the cost.

Title: Case Studies Text: Several full-scale field deployments have been conducted to demonstrate the use of the Trident Probe and UltraSeep System. Two case studies are presented here for sites in Florida. These projects were designed to test the field application of the Trident Probe and UltraSeep System and to validate the results obtained from the technologies.

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Title: Panama City Field Demonstration (1 of 8) Text: A field demonstration of the Trident Probe and UltraSeep System was performed at Naval Support Activity (NSA) Panama City, Florida. The objective of the project was to demonstrate and evaluate the effectiveness of these tools for characterizing coastal contamination migration under field conditions. Also, the results were used to evaluate the validity of monitored natural attenuation as a corrective action alternative for Area of Concern (AOC) 1 at NSA Panama City, which lies on St. Andrews Bay along the Florida panhandle.

Title: Site Background (2 of 8) Text: From the 1950s to 1970s, AOC 1 was used for firefighter training that generated waste oils, fuels, paint/thinners, and bilge water. The source area was remediated, but there was still some question over the potential for discharge of a 1,1-dichloroethene (DCE) plume that extended to the shoreline. In groundwater adjacent to the shoreline, 1,1-DCE was detected at concentrations exceeding the Florida Marine Surface Water Target Cleanup Level (SWTCL) of 3.2 μg/L. However, since there were no wells or direct push locations within the bay, it was unknown if significant discharge to surface water was occurring. The Trident Probe and UltraSeep System were used to identify areas of discharge and to asses if the contaminants would attenuate to achieve the SWCTL (through biodegradation, dilution, and dispersion).

Title: Experimental Design (3 of 8) Text: The Trident Probe was used to map the distribution of temperature, conductivity, VOCs, and water quality characteristics at 30 stations. These sites were located along five offshore transects extending eastward from the shoreline with six sampling stations each. The sample spacing was approximately 100 ft. Results from the Trident Probe were then used to select two sites for deployment of the UltraSeep System to measure discharge rates and sample for VOCs in seepage water. As shown here, piezometers in transect T-3 were used to validate the data collected by both the Trident Probe and the UltraSeep System.

Title: Trident Probe Deployment (4 of 8) Text: These photos show deployment of the Trident Probe in St. Andrews Bay. Because the Bay is relatively shallow, the Trident Probe was deployed manually by an operator wading to the site. The probe was inserted to a depth of approximately 2 ft below the sediment surface. Trident sampling was timed to occur during the falling tide when groundwater discharge conditions were most favorable. Thirty Trident stations were sampled for temperature/conductivity contrasts and pore water VOCs.

Title: UltraSeep Deployment (5 of 8) Text: These photos show the UltraSeep System being deployed in St. Andrews Bay. Two UltraSeep stations were monitored for specific discharge rate, VOC discharge, and temperature/conductivity of the discharge. Sampling locations for the UltraSeep were selected based on the results of the Trident survey. The locations were selected to target areas of highest potential groundwater discharge. UltraSeep measurements extended over a complete diurnal tidal cycle. Seepage water samples were collected approximately every 2.5 hours in proportion to discharge rate.

Title: Trident Probe Results (6 of 8) Text: The Trident Probe was used successfully to map areas of groundwater discharge from the site to St. Andrews Bay. As shown in Figure 1, groundwater discharge was identified by areas with lower conductivity (heavy blue-dashed line). The zone of discharge appeared to be limited to a band parallel to shore between about 100 to 300 ft offshore (between the white lines). All VOC analytes (including DCE) at all Trident stations were below the Practical Quantitation Limit (PQL) in both pore water and seepage water samples. Figure 2 shows that the 1,1-DCE concentrations were all non-detect including areas near the localized discharge zones based on conductivity (heavy blue-dashed line).

Title: UltraSeep Results (7 of 8) Text: UltraSeep was used successfully to quantify groundwater discharge rates and VOC discharge concentrations in two discharge zones identified with the Trident survey. Groundwater discharge was detected at both stations sampled and was always positive with rates ranging from about 2 to 8 cm/day. The maximum discharge rate occurred near the time of high tide. The 24-hour mean discharge rate was 5.1 cm/day. All VOC analytes (including DCE) in all UltraSeep samples were below the PQL with the exception of toluene. The low level of toluene detected in some samples was attributed to cross-contamination from the sampling system and/or vapors released by roofing sealants at the laboratory during the analysis. Results from three shallow piezometers installed adjacent to each UltraSeep station validated the results obtained from the UltraSeep.

Title: Conclusions (8 of 8) Text: Overall, the project was successful in demonstrating the utility of the Trident Probe and UltraSeep System in assessing coastal contamination migration. Groundwater discharge zones were defined based on conductivity differences. In general, temperature contrasts across the site proved to be too small to be useful in identifying groundwater discharge zones. The results demonstrated that DCE concentrations in the discharge zones offshore from AOC 1 were below detection. This finding facilitated the determination that monitored natural attenuation was a feasible remedy for AOC 1, providing a potential cost avoidance of $1,250,000 for active remediation.

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Title: NTC Orlando Demonstration (1 of 7) Text: At the Naval Training Center (NTC) Orlando, Florida, a pump-and-treat system was used to contain groundwater contaminated with VOCs and to prevent migration toward a nearby surface water body. The Trident Probe and UltraSeep System were deployed to further characterize the site. The objectives of the demonstration were to assess the following issues: 1. With the pump-and-treat system shut down, were VOCs discharging to Lake Druid from Operable Unit (OU) 4 at levels that pose an unacceptable risk to the environment? 2. Were natural processes effectively attenuating the remaining VOCs before they reach Lake Druid?

Title: Site Background (2 of 7) Text: The conceptual site model for OU 4 at NTC Orlando is shown here. VOCs released from a former dry cleaning site migrated downward into the groundwater creating the potential for discharge of the plume into the nearby marsh and lake.

Title: Experimental Design (3 of 7) Text: The pump-and-treat system was shut down 30 days prior to the start of the demonstration project. The Trident Probe was used to map the distribution of temperature, conductivity, and VOCs at 32 stations. The Trident Probe results were also used to identify UltraSeep sampling locations. Three UltraSeep stations (shown in blue) were selected for discharge rate monitoring and VOC seepage water sampling. Both Trident and UltraSeep results were validated based on a comparison to data from piezometers.

Title: Deployment (4 of 7) Text: These photos show deployment of the Trident Probe and UltraSeep System in Lake Druid using a small boat.

Title: Trident Probe Results (5 of 7) Text: The Trident Probe successfully identified two zones of potential groundwater discharge: Near-shore zone: extends ~50 to 100 ft offshore (~3 to 5 C cooler than surface water). Offshore zone: extends ~200 to 300 ft offshore (~3 to 5 C cooler than surface water). The Trident Probe successfully mapped the VOC distribution: Elevated VOCs were concentrated in near-shore zone. Some VOCs were also detected in offshore zone (previously unknown). All VOC detections were within discharge zones identified by moderate to strong temperature contrasts as measured by the Trident Probe.

Title: UltraSeep Results (6 of 7) Text: All three UltraSeep stations showed groundwater discharge. The strongest discharge occurred near-shore at 12.7 cm/day (T3-7) and the weakest offshore at 1.1 cm/day (T2-3). As shown in the graphs, VOCs were detected at all three UltraSeep stations. The highest VOC concentrations were detected near-shore (T3-7) including trichloroethene (TCE) at 6 μg/L, DCE at 646 μg/L, and vinyl chloride (VC) at 57 μg/L. However, VOCs were also detected offshore (T2-3 and T2-5). At these offshore locations, DCE and VC were detected at levels ranging from 47 to 57 μg/L and 7.6 to 24 μg/L, respectively. Most stations showed good correlation with piezometer results.

Title: Demonstration Results Schematic (7 of 8) Text: This schematic illustrates the transport and concentrations of contaminants based on the results of the Trident and UltraSeep demonstration at Orlando OU4.

Title: Conclusions (8 of 8) Text: The Trident Probe and UltraSeep System worked well under significantly different conditions from the Panama City demonstration. The results were found to be consistent with piezometer validation results. The conclusions of the demonstration were as follows: VOCs were found to be discharging to Lake Druid without operation of the pump-and-treat system. VOCs were detected in an offshore discharge zone that was not previously identified. Monitored natural attenuation alone was not likely to be a protective remedy at this site due to the rate of VOC discharge from the groundwater to the marsh and Lake Druid.

Title: Conclusions Text: The Trident Probe and UltraSeep System should be considered for application at a site when: There is clear identification of a terrestrial contaminant plume migrating to the shoreward boundary of a surface water body. Applicable or relevant and appropriate requirements (ARARs) or other compliance/cleanup drivers require identification of contaminant exposure levels in the surface water or at the interface. Hydrogeologic modeling results are ambiguous or require field validation. The area where the plume is impinging needs to be clearly delineated to address risk and/or remedial options (Trident Probe). The rate of discharge and associated contaminant loading requires delineation to address risk and/or remedial options (UltraSeep System).

Title: References Text: Chadwick, B. 2005. Coastal Contaminant Migration Monitoring Assessment, Naval Construction Battalion Center (NCBC) Site 07, Calf Pasture Point Davisville, Rhode Island. Draft Project Report. Revision 3. January. Chadwick, B. and A. Hawkins. 2005. Monitoring of Water and Contaminant Migration at the Groundwater-Surface Water Interface, Demonstration Site I: Naval Support Activity Panama City. Technical Report. Final. October. Chadwick, B. and A. Hawkins. 2007. Final Technical Report. Monitoring of Water and Contaminant Migration at the Groundwater-Surface Water Interface (ER200422). Draft. Environmental Security Technology Certification Program (ESTCP). January. Chadwick, D.B., M. Kito, A.C. Blake, and B. Harre. 2003. Technical Report 1898. Coastal Contaminant Migration Monitoring Technology Review. SPAWAR Systems Center San Diego. Space and Naval Warfare Center, San Diego (SPAWAR). 2003. Technical Report #1902. Coastal Contaminant Migration Monitoring: the Trident Probe and UltraSeep System, Hardware Description, Protocols, and Procedures.

Title: Contacts Text: For more information on the Trident and UltraSeep technologies, please contact: SPAWAR POC: (619) 553-5333 NFESC Technology POC: (805) 982-4890 NFESC T2 POC: (805) 982-1656 Case Study POC: (843) 820-7357