Constructing and Maintaining Parks and Recreational Facilities with Chicago Biosolids: Expanding Local Markets by Going Beyond Part 503 to Demonstrate Safety
Abstract:The Metropolitan Water Reclamation District of Greater Chicago (District) services Chicago and 124 suburban communities in Cook County, Illinois. The District collects and treats wastewater from a population equivalent to 11 million people and generates approximately 180,000 dry tons of biosolids annually. The District is committed to managing biosolids beneficially and economically. The District operates a diverse biosolids management program which includes using biosolids as a soil conditioner or soil substitute in the Chicago metropolitan area (Chicagoland).
The District operates its local program under a Controlled Solids Distribution permit issued by the Illinois Environmental Protection Agency. This is a unique umbrella permit that covers all projects and minimizes regulatory hurdles for its customers. The District has primarily undertaken projects at suburban sites which can be expensive due to long hauling costs. The District recently placed an emphasis on increasing biosolids use in the City of Chicago because it is economical and potentially sustainable. The District undertook a large demonstration of the use of biosolids for reclaiming brownfield sites having steel mill slag based soils in partnership with the Chicago Park District. It ran from 2000 through 2003 and demonstrated that turf and trees could be successfully grown on slag using biosolids as a soil component with no significant environmental impacts. Despite these results, the Chicago Department of Environment requested the District to demonstrate that its biosolids were equivalent to “clean fill” by utilizing the Illinois Environmental Protection Agency's Site Remediation Program soil clean-up objectives that define “how clean is clean.” These objectives include risk-based soil concentrations for 135 compounds (including nine trace elements regulated in the Part 503 biosolids rule) based on 10−6 risk level for inhalation, ingestion, and groundwater contamination with residential or commercial/industrial exposure scenarios.
The District's exceptional quality biosolids from the Stickney and Calumet Water Reclamation Plants were tested for the listed contaminants in 2000, 2004, and 2005, and the concentrations of most of the contaminants were found to be lower than the Tier I default remediation objectives (ROs) for residential property. Only six polyaromatic hydrocarbons and arsenic were found at concentrations above the ROs generated by the soil ingestion pathway. An alternative approach is allowable under which a site specific risk analysis can be utilized to generate ROs that are based on specific receptor/exposure scenario combinations. The risk assessment considered: athletic fields, playgrounds, picnic areas, community gardens, multiuse trails, parking lot landscaping, and park building landscaping in combination with adult workers and recreational visitors. Subsequently, a risk analysis was conducted specific to biosolids use at Chicago Park District recreational facilities. This represents a 5,000-acre market for the District biosolids. The risk assessment was conducted for benzo(a)anthracene, benzo(a)pyrene, benzo(b) fluoranthene, benzo(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, and arsenic. The risk assessment considered a dermal contact pathway, a soil ingestion pathway, and a dust inhalation pathway.
The results of the risk assessment convinced the Chicago Department of Environment that the District biosolids are safe for use on properties owned and managed by the city. Guidelines were developed that allow biosolids to be incorporated into soil at rates up to 20 percent by weight and to be topdressed onto turf at rates up to 20 tons/acre. The District is now marketing biosolids to the City of Chicago agencies for use on properties that they manage beginning with the Chicago Park District. The District is also pursuing sustainable use of the City of Chicago market indirectly by exploring partnership with topsoil vendors who will be allowed to utilize biosolids in topsoil blends up to 10 percent by weight without any regulatory restrictions in Illinois.
Document Type: Research Article
Publication date: 2007-01-01
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