Annual Loading Estimates of Selected Metals and PAHs in CSOs, using a Continuous PCSWMM Approach
Hamilton Harbour, Ontario, is an industrial port principally for the steel manufacturing industry, but also is a waterbody that increasingly supports recreational activities such as sailing, windsurfing, and fishing. While extensively used by a diverse group of interests, the harbour has been designated by the International Joint Commission (lJC) as one of 43 Areas of Concern (AOCs) around the Great Lakes due to environmental impairments. These impairments include: loss of habitat; high bacteria levels; fish consumption advisories; and high levels of metals and organic compounds in bottom sediment, particularly along the industrialized south eastern shore (e.g. lJC, 1989; Murphy et al., 199 1; RAP, 1992; Poulton et al., 1996). Most of the contamination of the harbour is the result of long-term stormwater runoff, combined sewer overflows, sewage treatment plant input, atmospheric input, and direct industrial discharges (Paul Theil and Beak Consultants, 1991; RAP, 1992; Chariton and LeSage, 1996; Diamond and Ling-Lamprecht, 1996).
Remedial programs to control contaminant discharges to the harbour have been implemented over the last 15 years and this work has resulted in improved water quality (e.g. lJC, 1989; Murphy etal., 1995; Diamond and Ling-Lamprecht, 1996). One of these programs has been the development and implementation of Hamilton-Wentworth Region's Pollution Control Plan (PCP). The PCP was developed by Paul Theil Associates and Beak Consultants (1991) under the direction of the Region and in consultation with the Province. Using SWMM to estimate flows, the PCP indicated that typically 23 combined sewer overflow (CSO) events occurred per year (May I to October 3 1) at each of more than twenty outfalls, resulting in a discharge of approximately 4.33 million m3 of combined sewage to Hamilton Harbour and Cootes Paradise. Since the adoption of the PCP in 1992, Hamilton-Wentworth Region has begun implementation of several of the recommendations. For example, the construction of four off-line storage tanks was completed between 1993 and 1997 at a cost of approximately $43 million. These tanks have a storage capacity of approximately 123,000 M3 and complement the previous (1988) construction of the Greenhill CSO tank that provides 70,000 m3 of storage (Stirrup, 1996). In addition, an in-line CSO storage tunnel is being considered, a microcomputer-based real-time control system is being implemented to optimize operation of the combined sewer system, and work has begun on improvements at the Woodward Avenue sewage treatment plant (Stirrup, 1996).
The PCP developed contaminant loading estimates for the CSOs in addition to examining overflow frequency, duration, and volume. However, due to budget constraints, a sampling program was not conducted under the PCP to determine contaminant concentrations for the loading estimates. Instead, the PCP relied on a literature search to determine representative pollutant concentrations (Paul Theil Associates and Beak Consultants, 1991). There clearly is some need to assess contaminant levels from CSOs based on actual sample collection.
Our group recently has focused on source evaluations to an industrial boat slip area of Hamilton Harbour that has undergone a demonstration in situ remediation of contaminated bed sediment. The intent of this source evaluation project is to determine the relative loadings of metals and PAHs (polynuclear aromatic hydrocarbons) to the boat slip from CSOs, non-point industrial stormwater runoff, coal pile runoff, and direct industrial discharges. Contaminated sediment remediation is being increasingly considered as a cleanup option for aquatic ecosystems, but it is important to understand how current contaminant loadings may affect the success of the remediation effort. The objectives of this chapter are:
1. to discuss the levels of selected metals and PAHs associated with CSOs from one major outfall, the Kennilworth St. outfall, to the study boat slip based on a preliminary sampling program conducted in 1996. These data also will begin to fill knowledge gaps identified in the PCP; and
2. to estimate the annual load of selected metals and PAHs for a "typical" year from CSOs. These loading estimates eventually will be compared with loading estimates from other sources to the boat slip.
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