Soils and Growing Mediums

Policy

A previous land use risk assessment has been performed for all crop production areas and is recorded below. Only land with a history of minimal risk of contamination is used in crop production. If previous land use is deemed a risk, the site is tested for contaminants and preventative measures are taken to mitigate the known risks. There is no evidence of flooding in production areas and all new materials have been used in production areas.

Previous Land Use Risk Assessment

Low areas near the Portage Creek had been previously filled with soil from unknown sources (“historical fill”) to raise elevation for building. Historical fill material is typically found to contain elevated levels of heavy metals such as lead, arsenic, manganese, mercury, copper, and cadmium.

Industry along the Portage Creek, as well as previous commercial and light industrial use of the site, has caused some buildup of other potentially hazardous materials in the soil.

Following is a list of contaminants tested on site:

• PCBs (polychlorinated biphenyls) were present in wastewater discharged into the Portage Creek by the paper industry,
• PNAs (polynuclear aromatics, also known as PAHs or polycyclic aromatic hydrocarbons) are a remnant of motor oils, diesel fuels, other “Heavier” petroleum sources, and also coal.
• VOCs (volatile organic compounds) are a remnant of solvents, such as those used in cleaning, and of other petroleum products.
• Heavy metals: arsenic, barium, cadmium, chromium, copper, lead, manganese, mercury, nickel, selenium, silver and zinc.

Testing Methods

• Prein & Newhof, a Michigan-based civil and environmental engineering firm, conducted the soil and groundwater analysis for the entire Bronson Healthy Living Campus site.
• A total of 50 soil samples were taken between September 2013 and May 2014 and tested for heavy metals, PNAs, and VOCs. An additional 15 samples were tested for PCBs. Samples were generally taken from the top 2.5 feet of soil, but some were as deep as 5 feet. Low flow groundwater samples were also tested for metals, PNAs, and VOCs.
• EPA conducted a separate analysis on soil samples for PCBs near the Food Innovation Center building; some EPA samples were also tested for VOCs and heavy metals.

Summary of Findings and Actions Taken During Construction

Various soil samples exceeded the levels of contaminants allowed, using Part 201 Generic Criteria for Residential Areas from Michigan’s Natural Resources and Environmental Protection Act of 1994.

• Low levels of PCBs were found in certain areas of the property.

Actions Taken

PCB-contaminated soil was removed and disposed of properly in a regulated landfill. The remaining PCB levels were found to be below regulatory cleanup criteria, so these soils were left in in place and covered with clean fill, as described below.

• Heavy metals Arsenic, Cadmium, Copper, Lead, Manganese, Mercury, Selenium, Silver, and Zinc were found in soil samples at actionable levels (at concentrations that exceeded Part 201 Generic Residential Cleanup Criteria) in various combinations throughout the site. Arsenic, copper, lead, manganese and mercury were found in groundwater samples with concentrations that exceed Part 201 Criteria Residential Criteria. Risks for exposure to these heavy metals are through ingestion of groundwater, direct contact with soil, or in some cases inhalation of small particles of soil. It was determined that the overall risk of exposure to soil contamination would be minimized by leaving the soil undisturbed in place and capped with clean soil, as described below.
• Contaminated soil was covered by an orange demarcation barrier to mark its level, and covered with at least 6 inches of clean topsoil to protect against direct contact.
• While some soils were moved within the site during grading (so that buildings are above flood levels), no material was removed from the site, and efforts were made to prevent accidental dispersal of soil off the site.
• PNA and VOC levels in soil samples were found to be elevated in certain limited areas on the site. The risk for exposure to PNAs and VOCs is through direct contact to certain PNA compounds and inhalation of certain PNA and VOC gases as they are released from the soil, which can infiltrate buildings.
• Contaminated soil was covered by an orange demarcation barrier to mark its level, and covered with at least 6 inches of clean topsoil to protect against direct contact.
• All buildings were constructed with an impermeable vapor barrier (“Liquid Boot”) and vapor mitigation system to prevent infiltration of gases into the building.
• Soils found at 619 E. Crosstown to exceed concentrations for ambient air quality were removed entirely and disposed of properly in a regulated landfill.

Produce Grown on Site

The threat of exposure to people comes primarily through direct consumption, inhalation, or absorption through skin of contaminated soil, either from not properly washing hands after handling contaminated soil, or from not properly washing vegetables that came into contact with contaminated soil including splashing soil. Some research suggests there can also be uptake of heavy metals by vegetable plants and deposition in edible parts.

To mitigate these risks to the produce-consuming public, we have adopted the following policies:

• The entire site has been covered in a marker barrier to note the presence of contaminated soil.
• This barrier was then covered with 6 inches of clean topsoil to prevent people from coming into direct contact with the contaminated soil and thereby preventing direct consumption and absorption, and to prevent the creation of contaminated soil dust particles that can be inhaled.
• Produce grown outdoors is grown in raised beds which are filled with clean topsoil, with a double barrier of heavy duty groundcloth and 6 mil plastic to prevent roots from coming into contact with any soil outside of the raised bed, and preventing the roots from reaching any potentially threatening soil.

Growing Mediums

The following growing mediums are used in place of contaminated and potentially contaminated soil present on site:

• Topsoil
• Commercially produced compost