February 7, 2018 – Our thanks to Jeff Cox of Holdrege & Kull for sharing this extraordinary time lapse video with our readers. Jeff is a Geologist and an FAA Licensed Drone Operator.

YouTube video

This 3′-48″ time lapse video shows the condition of the Little Wolf Creek Sinkhole between January 11, 2017 and January 10, 2018. The video is composed of a series of geo-referenced Orthomosaics produced from high resolution photos acquired by Holdrege&Kull’s drone.

Located in Grass Valley, California, the Little Wolf Creek sinkhole occurred the morning of January 11, 2017. Holdrege & Kull’s geotechnical team was requested by Mr. Tim Kiser, Grass Valley City Engineer, to meet on-site to access the damage. H&K deployed an engineer and geologist immediately, and their FAA licensed pilot and drone a short time after. The acquired aerial photo and video of the site was used by the H&K team, City officials, and local firm C&D Contractors to assess the damage.

The H&K team was able to quickly and safely determine that the extent of the failure was localized and did not impact the City’s waste water treatment plant located only a few hundred yards downstream. H&K provided geotechnical consulting services related to slope stability analysis, special inspection and testing of shotcrete used to repair the culvert, laboratory soil and compaction testing of fill material, and a storm water pollution prevention plan (SWPPP).

In addition, H&K provided regular drone flights to capture high resolution 4K video, and geo-referenced 20 megapixel still images to document site conditions. H&K shared HD video, 2D maps in the form of Orthomosaics, interactive 3D models, and elevation data illustrations with stakeholders and the media.

Tim Kiser and his team earned the 2017 Geotechnical Project of the Year Award from the Sacramento Chapter of the American Public Works Association for their response to this catastrophe.