SHN performed settlement surveys on nine closed landfills in Siskiyou County. Landfill closure monitoring requires the County to conduct iso-settlement surveys that meet exacting permitting requirements (CCR Title 27, Section 21090(e)(2)). Monitoring closed landfill settlement precisely and accurately is important because any ponded water on the landfill cap has the potential to infiltrate to the waste below, creating landfill leachate that can affect soil underneath the landfill, or shallow groundwater if it is present.
Using unmanned aerial vehicles (UAVs) and traditional surveying techniques, SHN surveyors, UAV pilots, and geographic information system (GIS) specialists created maps and images that were used by the County to assess settlement and erosion at the nine landfills. The maps met the requirements for permit compliance. Should the County wish to observe landfill cap conditions in greater detail, high resolution photographs are also available, which would not have been the case had we created the maps using only standard surveying techniques. SHN was able to underlay the photographs as backgrounds to the topographic maps, providing additional information for the County as it assesses the current status of their closed landfills.