Olsson is providing key technical support in soil science for the new landscape design of the Jefferson National Expansion Memorial (JNEM) in St. Louis, Missouri. The major component of this project involves regrading and revegetating the park grounds surrounding the JNEM’s Gateway Arch. Much of the JNEM area and nearby downtown locations are built on old demolition debris from the city's old riverfront industrial area, and was covered with river sediment and relic clay soil.
In the ensuing 50 years since the Gateway Arch was built, maintaining vegetation on the park grounds has required massive inputs of irrigation, fertilizers, and frequent replacement of vegetation that could not survive the poor soil conditions.
Olsson’s understanding of regional and site soils, including drainage, structural stability, and surface soil, has been essential for achieving a successful, sustainable landscape at the JNEM. Starting in 2012, Olsson evaluated site conditions and soils to assess the extent of issues that affected plant sustainability and the potential for ameliorating soil conditions without wholesale replacement. In addition, Olsson worked closely with the project team to develop new soil profiles where structures would be removed and new soil placed.
Key in this effort was to achieve soil conditions that would successfully sustain plant growth and vigor with substantially reduced maintenance needs but would also ensure consistency in landscape features throughout the park. This would involve conditioning soils in place in much of the park to improve infiltration and aeration while also improving water holding and nutrient supplying capacity. The rehabilitated grounds are scheduled to be highlighted as part of the Arch's 50th anniversary in 2015.