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Occasionally, creosote-treated railroad ties need to be replaced, sometimes in sensitive environments such as wetlands. To help determine if this is detrimental to the surrounding environment, more information is needed on the extend and pattern of creosote, or more specifically polycyclic aromatic hydrocarbon, migration from railroad ties and what effects this would have on the surrounding environment.
Occasionally, creosote-treated railroad ties need to be replaced, sometimes in sensitive environments such as wetlands. To help determine if this is detrimental to the surrounding environment, more information is needed on the extent and pattern of creosote, or more specifically polycyclic aromatic hydrocarbon (PAH), migration from railroad ties and what effects this would have on the surrounding environment. This study is a report on PAH level testing done in a simulated wetland mesocosm. Both newly treated and weathered creosote-treated railroad ties were placed in‍?the simulated wetland. As a control, untreated ties were also placed in the mesocosm. Samples were taken of the ballast, wetland sediments, groundwater, stormwater, and soil cores. Ballast and sediment samples were taken at intervals during the 18 months of the study. Results of the study showed that there was an initial pulse of PAH moving from the treated‍?railway ties into the ballast during the first summer of the study. More PAH moved from the newly treated ties than from the weathered ties at this time. No significant PAH loss was observed from ties during the second summer. A small portion of PAH appeared to move vertically down into the ballast to approximately 60 cm. Small amounts of PAH may have migrated from the ballast into adjacent wetlands during the second summer, but these amounts were not statistically significant. These results suggest that it is reasonable to expect a detectable migration of creosote-derived PAH from newly treated railway ties into supporting ballast during their first exposure to hot summer weather. The PAH rapidly disappeared from the ballast during the fall and winter following this initial loss. Then statistically insignificant vertical and horizontal migration of these PAH suggests that they either evaporated or were degraded in the ballast. Effects of PAH on the environment are discussed in the Appendix.
Timber bridges provide an economical alternative to concrete and steel structures, particularly in rural areas with light to moderate vehicle traffic. Wooden components of these bridges are treated with chromated copper arsenate type C (CCA), pentachlorophenol, or creosote to prolong the life of the structure from a few years to many decades. This results in reduced transportation infrastructure costs and increased public safety. However, the preservative used to treat the wooden components in timber bridges is lost to the environment in small amounts over time. This report describes the concentration of wood preservatives lost to adjacent environments and the biological response to these preservatives as environmental contaminants. Six bridges from various states were examined for risk assessment: two creosote treated bridges, two pentachlorophenol-treated bridges, and two CCA-treated bridges. In all cases, the largest bridges located in biologically active environments associated with slow-flowing water were selected to represent worst-case analyses. Sediment and water column concentrations of preservative were analyzed upstream from, under, and downstream from each bridge. The observed levels of contaminant were compared with available regulatory standards or benchmarks and with the quantitative description of the aquatic invertebrate community sampled from vegetation and sediments. Pentachlorophenol- and creosote-derived polycyclic aromatic hydrocarbons (PAHs) were not observed in the water near any of the selected bridges. However, low levels of PAHs were observed in the sediments under and immediately downstream from these bridges. Pentachlorophenol concentrations did not approach toxicological benchmarks. Sediment concentrations of naphthalene, acenaphthylene, and phenanthrene exceeded the probable effect level. Metal levels at the bridges treated with CCA were less than predicted effect levels, in spite of questionable construction practices. Adverse biological effects were not observed in the aquatic invertebrate community or laboratory bioassays conducted on water and sediments sampled at each of the bridges. Results of this study reveal the need to follow the construction information found in Best Management Practices for the Use of Treated Wood In Aquatic Environments published by Western Wood Preservers Institute. Regulatory benchmarks used in risk assessments of this type need to be indexed to local environmental conditions. The robust invertebrate communities associated with slow-moving streams over soft bottoms were not susceptible to the concentrations of PAHs that would be expected to affect more sensitive taxa, which typically are located in faster moving water over hard bottoms. Contaminants released from timber bridges into these faster systems (where more sensitive taxa are located) are significantly diluted and not found at biologically significant levels.
Creosote is used in Canada as a heavy-duty wood preservative for railway ties, bridge timbers, pilings, and large-sized timber. It is composed of hundreds of compounds, the largest group being the polycyclic aromatic hydrocarbons (PAHs). In this assessment, creosote-impregnated waste materials includes creosote waste products and creosote-contaminated sites. This report gives a summary of information critical to assessment as toxic, including identity, properties, and uses; its entry into the environment; and exposure-related and effects-related information. An assessment of toxic under the Canadian Environmental Protection Act relating to the environment is also included.
Treatment Marshes for Runoff and Polishing represents the most comprehensive and up-date-date resource for the design, construction, and operation of marsh treatment systems. This new edition represents a complete rewrite of the surface flow sections of previous editions of Treatment Wetlands. It is based on the performance hundreds of treatment marshes over the past 40 years. Treatment Marshes focuses on urban and agricultural runoff, river and lake water improvement, and highly treated municipal effluents. New information from the past dozen years is used to improve data interpretation and design concepts. Topics included in this book are Diversity of marsh vegetation Analyses of the human use of treatment marshes New concepts of underground processes and functions Spectrum of marsh values spanning mitigation, restoration, enhancement, and water quality improvement Improved methods for calculation of evapotranspiration and wetland water temperatures Hydraulics of surface and subsurface flows in marshes Analysis of long track records for deterministic and probabilistic behavior Consideration of integrated microbial and vegetative contaminant removals via mass balances Uptake and emission of gases Performance of urban and agricultural wetlands Design procedures for urban and agricultural wetlands Reduction of trace metals, pesticides, pharmaceuticals, endocrine disruptors, and trace organics Updated capital and O&M economics, and valuation of ancillary benefits An updated list of over 1900 references