Landfills and Other Solid Waste Management Facilities
Cambridge Environmental has assessed potential hazards to human health and the environment due to chemical releases from landfills and other facilities that process municipal solid waste (MSW). Such sites and facilities are numerous, given the ubiquitous, longstanding, and ongoing need to manage MSW disposal. Landfills and combustion (typically waste-to-energy) facilities are the major technologies used by the MSW industry. Detailed discussion of waste-to-energy risk assessment, entailing evaluation of multiple exposure pathways that track contaminants through the environment and food web, is provided separately.
Risks to health and the environment due to landfills follow a pattern of hazard identification and mitigation through technology development. Historically, landfills were simply initiated on available lands, or in excavations such as spent quarries, with little environmental consideration. Unlined, uncapped, and indiscriminately accepting of all wastes (including industrial chemicals), many of these landfills evolved to Superfund sites as releases of their leachate contaminated watersheds with salts, metals, and organic compounds. Modern sanitary landfills, properly designed and maintained, prevent contaminant leaching, but enhance the production of landfill gas, the escape of which may cause nuisance odors and raise concerns over potentially toxic constituents. Consequently, landfill gas is collected and treated at many landfills. Because treatment typically involves combustion, air pollutants are released.
Depending on age and development, landfills can potentially release contaminants to all realms of the environment, as can transfer stations, recycling facilities, composting operations, and other MSW management facilities (including novel waste conversion technologies). The keys to assessing potential risks to human health and the environment involve (1) identification and characterization of contaminant releases, (2) estimation of levels of exposure to contaminants through relevant pathways, and (3) evaluation of the toxicological significance of such exposure. These factors differ among facilities and their settings, which must be carefully considered in risk assessment.
Plainville (MA) Landfill
Cambridge Environmental developed a human health and environmental risk characterization for the Plainville Landfill as part of a Comprehensive Site Assessment under Massachusetts solid waste regulations. Risks were evaluated from contaminants in groundwater and surface water due to leachate release. 1,4-Dioxane was identified as a marker chemical, and plume discharge to a nearby lake required a detailed ecological risk assessment, including sampling of fish to determine uptake rates of manganese and other metals. Significant odors from landfill gas emissions were assessed through one of the first real-time ambient monitoring studies of hydrogen sulfide coupled with source-gas analyses. Risk assessment results were used as part of a third-party study of cancer incidence rates in the local population.
Cambridge Environmental developed a risk assessment of a proposed expansion of the Chicopee (MA) Sanitary Landfill to satisfy the Massachusetts Department of Environmental Protection's requirement to demonstrate the project would not significantly increase risks to public health. The study is representative of a number of Cumulative/Facility Impact Assessments designed to evaluate risks from the operation of solid waste management facilities. The U.S. EPA's LandGem model predictions of gas generation were combined with a measured landfill gas composition profile to estimate potential emissions of over thirty Hazardous Air Pollutants (HAPs) identified in landfill gas. Air dispersion modeling was then applied to project incremental concentrations of HAPs in air at locations in the landfill vicinity. Incremental cancer and non-cancer risks were estimated by combining modeled HAP concentrations with toxicity data, and risk levels were found to be lower than target levels. The potential cumulative effects of other air pollution sources were qualitatively assessed by identifying emissions from nearby industries and facilities, and environmental monitoring data on the landfill site were reviewed to identify whether contaminants in groundwater might present risks to local citizens.
Cambridge Environmental has evaluated health risks near a number of landfills plagued by persistent and sometimes severe odors. In a number of cases, odors ensued from using sulfur-rich fines from processed construction and demolition (C&D) debris as daily cover material at municipal solid waste (MSW) landfills. Initially this was thought to be a beneficial use of material, but anaerobic decay of the combined MSW and C&D fines has in some cases increased hydrogen sulfide (H2S) concentrations more than one-hundred fold. Fugitive emissions of landfill gas, unavoidable to some degree even with an efficient collection system, can be odorous. Although landfill gas contains some benzene, vinyl chloride, and many other potentially hazardous chemicals, toxicity evaluations have identified H2S as the principal contributor to health risk, and have thus focused on irritation effects to differentiate significant health effects from nuisance conditions. Landfill gas treatment (through combustion) can also introduce risks from exposure to sulfur dioxide, produced from H2S.
Emissions from truck traffic
Cambridge Environmental evaluated incremental concentrations of particulate matter in ambient air due to the diesel exhaust emissions from increased truck traffic at the proposed expansion of the E.L Harvey & Sons facility in Westborough, MA, a solid waste recycling facility. Future fleet emissions were estimated as input to dispersion models to estimate impacts at nearby homes along the proposed truck route.
Cambridge Environmental developed numerical guidelines for various chemicals contained in compost produced from yard waste and municipal solid waste at the Nantucket (MA) Co-Compost Facility. Guidelines were designed to allow various beneficial uses of the compost, including residential landscaping and home gardening, considering potential avenues of exposure such as incidental ingestion and dermal contact. Of the contaminant levels measured in compost samples, various phthalates were sometimes encountered at levels exceeding risk-based standards. Potential risks were mitigated through process changes to limit contaminant concentrations in compost.