Alleged Pesticide Drift Incident in Kern County, CA
Overview
This litigation case dealt with alleged drift of pesticides from aerial applications, with claimed damage to neighboring growers’ crops. The sprayed herbicide was Gramoxone, whose active ingredient is Paraquat. The spray was performed over a few days in February 2015 using an Air Tractor AT-802A aircraft.
EnviroComp's Role
We were hired by the defense attorneys and asked to review all available documents and plaintiffs’ claims. We collected and examined all the meteorological data available in the region, including satellite pictures taken at the time of the spray. Our meteorological analysis concluded that, during the times of the aerial spray, the meteorological conditions were favorable for on-target application of pesticides (e.g., appropriate wind, speed and directions, and there were no ground-based temperature inversions or fog). We analyzed the SATLOC files created during the aerial spray. These files were useful to visualize the exact trajectory of the aircraft and the extent of the sprayed areas (see an example in Figure 1).
Using all the available information - including: type of aircraft, swath width, nozzle properties, field locations, chemical properties, meteorological data - we chose the AGDISP computer model to simulate the extent of drift of materials away from the target fields. AGDISP was developed by the USDA Forest Service and designed to optimize agricultural spraying operations. The model has detailed algorithms for simulating the trajectories of sprayed droplets, including partial evaporation and the possible interaction with the wake of the aircraft. AGDISP simulates the release, dispersion, and deposition of pesticides over and downwind of the application area.
Our AGDISP results showed, for all the aerial applications, an extremely limited drift, even under conservative assumptions. As shown in Figure 2, total deposition outside the target fields is orders of magnitude lower than the values calculated in the target field and goes quickly to zero within half a mile. The same results shown in Figure 2 were also visualized over a map, as shown in Figure 3.
As a result of our role and assignment, the defense attorneys were able to use our modeling analysis to obtain a positive outcome.
Visuals
