Theme: 11. Advanced Diagnostic Tools

Topic Area: 11b. Remote Sensing, Drones, and Other Unmanned Systems for Remote Monitoring and Site Assessments

Formatted Title:

Drone Applications to Optimize Long-Term Operational Success of a Phytoremediation Facility

Background/Objectives:

Historical chemical manufacturing operations, at a site located in California, resulted in the creation of several solid waste management units (SWMUs) including a former landfill and a former pond that contained byproducts from a chlor-alkali plant. The site borders the Sacramento-San Joaquin River tidal delta and has a semi-arid climate characterized by warm summers and cool, wet winters.

At closure, a 15-acre pond area was capped with a geosynthetic clay liner (GCL) in 2000. A groundwater monitoring network was established to monitor groundwater conditions impacted by mercury, chlorinated organics, and pockets of high pH (>11). However, after elevated mercury concentrations persisted in groundwater in the 1-acre area in the western portion of the closed SWMUs, an Engineered Phytoremediation System (EPS) was approved to mitigate localized contaminant migration. The objective of the EPS was to influence the existing hydraulic gradient of shallow groundwater beneath the capped area west of the SWMU to prevent or reduce contaminant migration.

On-going vegetation assessments are critical to successful EPS operations including quantifying biomass change, plant vigor, water balance, disease, and drought effects. This study presents the transition from manual to digitally based assessment of key plant metrics using drone technology and image processing.

Approach/Activities:

This study documents an evolution in operation and monitoring techniques to support on-going assessment of EPS plant vigor, aerial vegetation coverage and application of adaptive design principles and attentive maintenance. The study describes the EPS from pilot stage through full-scale planting, a grow-in period, and full-scale operations.

EPS drone imagery was recently incorporated into operational and performance evaluations. By analyzing canopy coverage by species with visible wavelengths, the drone imagery provided accurate measurements of canopy cover, and augmented the assessment of overall plant health and vigor for the entire population of plants on site. Review of both overhead and oblique imagery was useful to visualize the 3-D features of the canopy. The use of drone technology resulted in significantly greater detail, safer operations and lower cost compared to traditional manual vegetation data collection means.

Results/Lessons Learned:

The operational challenges of an EPS in a semi-arid climate are discussed as it responds to changes in local climate, rainfall, and groundwater conditions. Changes to operations and maintenance practices were made over the life of the facility to improve facility performance. Means and methods of using drone imagery analytics to evaluate key success metrics of the EPS facilities are presented.

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Mark Madison