In the not-too-distant future, the Iowa Department of Transportation plans to replace a major bridge across the Mississippi River in the City of Lansing. Cultural resources surveys is required for the project. In 2018, the agency contracted with Tallgrass Archaeology LLC for an archaeological survey of the impact area, which is located in a heavily developed portion of Lansing’s historic riverfront district. The project posed a challenge in that the city is built on ancient landforms of the Mississippi River, portions of which were undoubtedly preserved beneath the built environment. The Tallgrass Archaeology’s first task was to locate where these landforms are preserved, a task that required geoarchaeological services.
Impact7G offers a broad range of geoarchaeological services, which for the Lansing project included both GIS-based mapping and geological coring. We not only identified and mapped the buried landscapes of the project area, we identified places where archaeological sites were most likely to be found, how deep the archaeologists would need to test to find them. In addition, Impact7G’s senior geoarchaeologist Joe Artz had previous experience conducting successful geoarchaeological projects in several Iowa cities. He also had worked directly with Tallgrass Archaeology as well as the Iowa DOT on many projects, and was familiar with the needs and expectations of both.
- By coring to depths of up to 16 ft, Impact7G located two areas where soils untouched by urban development were preserved. In one area, the preserved landscape was buried under 5-7 feet of fill, but in the other, the intact soils were preserved at the modern ground surface in yards between houses and even beneath the existing Mississippi River bridge itself.
- Tallgrass archaeology subsequently tested in these areas, identifying archaeological sites buried up to 2 m that will need to evaluated and mitigated prior to impact, to meet the DOT’s compliance requirements.
- Impact7G’s project provides the Iowa DOT with yet more evidence that, even in towns and cities, ancient, irreplaceable cultural resources worthy of protection are preserved.