Battelle Chlorinated Conference Event Abstract 

Estimating Stockpile Volumes Using Drone Surveying Technology

Background/Objectives:

A 20-acre parcel located in Los Angeles contains numerous stockpiled soil and debris/fill material deposited from past undocumented City construction project activities. A Site walk was conducted to observe the numerous stockpiles which consist of various heterogeneous stockpiled soils, dredged materials, and construction debris.  In order to estimate the volume of stockpiled material, a strategic approach was created to grid the Site using an unmanned, overhead drone fly-over to survey and map the field grid to identify the areal extent of stockpiled materials. The Site is located in a Class E airspace which allows the operation of overhead flying of unmanned aircrafts. Prior to mobilizing to the Site, a Temporary Entry Use Permit was obtained from the local agency for operating an unmanned aircraft over the Site. The stockpiled soils, dredge materials and concrete debris will require  sampling for chemical analysis to determine if stockpiled materials can be reused at the Site or will be hauled offsite for proper disposal.

The purpose of the drone evaluation is to determine ground surface elevations, to differentiate stockpile material types, and to estimate the volume of stockpiled soils and debris materials in order to develop a sampling plan.

Approach/Activities:

A Phantom 4 Pro unmanned Drone flew over the Site to survey the ground surface, obtain topographic elevation, identify proposed stockpiled sampling locations, and estimate the material type and volume of stockpiled materials. A drone flight plan was created by establishing a flight pattern consisting of longitudes/latitudes (waypoints) that navigated the Drone into east-west grid paths. By utilizing ground control points, the accuracy of the results from the drone survey were within a few centimeters. Global Positioning System (GPS) ground-based survey equipment was used to collect coordinates and elevations of each ground control point.  Following the drone flight, our DroneDeploy software platform was used to process the aerial images and coordinate data into three-dimensional (3-D) models, which were then utilized in ArcGIS to create digital elevation maps. Due to the number of different stockpiles with unknown origins consisting of various compositions and colors, they were managed as individual stockpiles for categorization and discrete sampling and analysis. Based on this evaluation, it was estimated that 48 representative discrete samples be collected for chemical analysis.

Results/Lessons Learned:

The Drone survey revealed approximately 550 individual stockpile locations. Each stockpile was plotted and elevations estimated to provide the volume of the stockpiled material either individually or in groupings. An orthomosaic map with elevations was then created showing the proposed stockpiled soil and concrete material sampling locations. Coordinates of the collected sample points were incorporated into the 3D model and connected spatially, creating multiple lines emanating from each point. The DroneDeploy software platform then reanalyzed the new spatial data and identified the shared points. The map categorized the stockpiles based on material type, size and estimated volume. The estimated stockpiles consisted of soil/dredged stockpiled material, concrete/asphalt, construction debris and gravel/boulders/cobbles for a total volume of approximately 2,700 cubic yards which were differentiated with various colors.

The analytical results of the stockpiled samples will be illustrated by showing the constituent of concern concentrations detected along with their waste stream designation of either non-hazardous, non–Resource Conservation and Recovery Act (RCRA) or RCRA hazardous waste.

Co-Author: Anthony Lizzi, PG, CHG
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Presenter: Jared B. Recla, FAA Part 107, USDOT, Caltrans
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