Omaha Botanical Garden Flourishes with Reclaimed Foundation

Project

Lauritzen Gardens/City of Omaha

Location

Omaha, NE

Challenge

Landfills are eyesores and can be bad for the environment, but with science and the right engineers with a vision for potential, that can change.

Terracon’s Omaha office began geotechnical, environmental, and materials services at the Lauritzen Gardens, Omaha’s botanical center, in 1995. Occupying approximately 100 acres, Lauritzen Gardens sits partially atop an undocumented landfill and former balefill operated by the City of Omaha. A balefill is a type of landfill where solid waste is compacted and baled and wrapped with steel strapping or plastic.

The biggest challenges were identifying how deep the landfill materials were buried, how much settlement the new buildings could withstand, and what needed to be removed to provide a solid foundation for the site’s new facilities. The team ultimately discovered landfill deposits in excess of 20 feet below the surface.

There were also environmental concerns about potential volatile organic compounds produced by the landfill and released to the atmosphere via the landfill gas collection system, and the condition of the landfill gas collection system.

Solution

To document the landfill deposits, the team conducted subsurface exploration and geophysical testing, and made geotechnical recommendations for multiple buildings, including the visitors’ center, a miniature version of Mount Fuji in the Japanese Gardens, and an elaborate entry gate structure. We also provided forensic consulting services for a roadway and segmental block retaining wall structure built in a drainage swale which was constructed over landfilled materials.

An impressive glass rainforest building was constructed as a later expansion and included a collection drains system underneath the building slab, based on our recommendations.

We also prepared a limited human health risk assessment to evaluate potential risks resulting from exposure to landfill materials and byproducts. Since the former balefill materials were unknown, our environmental team conducted data collection and evaluation, a toxicity assessment, and an exposure assessment at the site. The human health risk assessment indicated exposure/risks from landfilled materials were below the Environmental Protection Agency’s standard acceptable risk thresholds.

Results

The subsurface exploration allowed the City to create and execute a realistic budget and framework for the project. With the data from our reports, they didn’t start digging without knowing the extent of the deposits beneath the surface. After removing landfill materials from below settlement-sensitive buildings and designing other structures for anticipated settlement, the City was able to reclaim the area that otherwise wouldn’t have been used.

The development was a “green” project as Lauritzen Gardens wanted to save as many trees as possible and dispose on-site those that were cut down. We provided recommendations on where and how the tree root balls could be buried on-site.

The attraction now boasts a 32,000-square-foot visitor and education center which includes a 5,000-square-foot floral display hall, an education wing, and one of the region’s only horticultural libraries. The visitor and education center further serves the community as home to hundreds of festivals, special events, adult horticulture and children’s education classes, and weddings.