As a result of strong state, local, and federal legislative actions with overwhelming public support, the cleanup of the Upper Mississippi River in the Twin Cities area is a national environmental success story. Comprehensive water pollution surveys dating back to 1926 documented the magnitude of the problems and provided the technical basis for the implementation of effective engineering proposals for abatement of water pollution in the river. Since enactment of the Clean Water Act in 1972, Minnesota has increased the water quality standard for DO to 5 mg/L and invested in upgrades to obtain better-than-secondary levels of wastewater treatment for the Metro plant and the other wastewater treatment plants operated by the MCES.
In contrast to the excessive effluent loading from the Metro plant during the 1960s, the investment in upgrades to the Metro plant during the 1980s, including nitrification, have succeeded in reducing effluent discharges of BOD5 from 1968 to 1998 by 95 percent (Figure 12-9), suspended solids from 1968 to 1998 by 95 percent (Figure 12-10) and ammonia-N from 1982 to 1998 by 90 percent (Figure 12-11). As a direct result of these upgrades, compliance with water quality standards for DO has been achieved even under the low-flow conditions of the drought of 1988 (Lung, 1998). The accelerated program to separate stormwater and sanitary flow succeeded in achieving compliance with state standards (200 MPN/100 mL monthly geometric mean and 2,000 MPN/100 mL for individual samples) for fecal coliform bacteria at the 71 percent level for samples collected during 1996-1998. As a result of the industrial waste pretreatment program initiated in 1982, the discharge of heavy metals to the Metro plant (and the Upper Mississippi River) has been reduced by about 90 percent (MCES, 1999) and mercury loading from the Upper Mississippi River to Lake Pepin in 1990-1996 declined by almost 70 percent from the 1960s level (Balogh et al., 1999). Despite these significant improvements, MCES has targeted toxic chemicals (e.g., PCBs) and heavy metals (e.g., mercury) as contaminants of concern for monitoring, identification of sources, and reduction of the load discharged to the river.
In contrast to the degraded environmental conditions during the 1950s through 1970s, the Upper Mississippi River is no longer a place to avoid. Parks, trails, and marinas have been developed along the river in areas where no one would have considered making such investments in the 1970s. A thriving riverfront corridor increases the value of both commercial and residential properties along the waterfront. The city of St. Paul, for example, through the St. Paul Riverfront Corporation, has invested nearly $500 million (as of the mid-1990s) for land acquisitions and infrastructure development along the riverfront (Donlan et al., 1995). In the late 1980s, private developers began to respond to riverfront infrastructure investments by obtaining more than $7 million in tax increment financing for development along the riverfront (Donlan et al., 1995). In addition to private development, in December 1999, the Science Museum of Minnesota completed a new museum along the riverfront in St. Paul that features exhibits on the Upper Mississippi River.
The record clearly shows that the Clean Water Act of 1972 profoundly affected every community in Minnesota, including the Twin Cities. The CWA accelerated the cleanup of the Upper Mississippi River by providing federal funds for the construction of new wastewater collection and treatment systems and the upgrading of existing sewage treatment plants. Since the mid-1980s, the resurgence of mayflies and the record of greatly improved compliance with water quality standards for dissolved oxygen and fecal coliform bacteria are key indicators of the effectiveness of the water pollution control efforts accomplished by state, federal, and local governments in the Twin Cities.
By the end of 2005, the Metro plant will have implemented biological removal of phosphorus to meet an annual effluent level of 1 mg/L for phosphorus (MCES, 1998a). As of 1999, "BioP" had been successfully implemented in a portion of the Metro plant and at suburban plants discharging to the Minnesota River. Under the Metro Environment Partnership, the control of urban and rural runoff will be addressed by a $7.5 million commitment from the MCES to reduce pollution from the seven-county Twin Cities metropolitan region (MCES, 1998a). State-of-the-art technology for solids processing, approved in July 1998, will reduce mercury emissions by 70 percent along with other pollutants and odors (MCES, 1998a). Further reductions in mercury dis charges to the river from the Metro plant will be accomplished as a result of a partnership between the MCES and the Minnesota Dental Association to test and evaluate new technologies to filter dental amalgam from wastewater (MCES, 1998b, 2000).
Although significant accomplishments have been made to improve water quality and ecological conditions in the Upper Mississippi River, continued investments are needed to address contemporary issues for continued restoration and maintenance of the ecological integrity of the river. The designation of the Upper Mississippi River as an American Heritage River in July 1998 recognizes both the significant environmental improvements that have been accomplished and the continuing need to address the key ecological issues identified in the 1990s. The key water quality and resource management issues identified for the Upper Mississippi River (USGS, 1999b) for the twenty-first century include the following:
• Point and nonpoint source loading of nutrients, sediments, heavy metals, and toxic chemicals in the Minnesota River and Upper Mississippi River from agricultural and urban land uses.
• Point and nonpoint source loading of nutrients and pesticides to aquifer systems from agricultural land uses.
• Contamination of groundwater with toxic chemicals from industrial activities and leachate from landfills.
• Contamination of surface waters and groundwater in areas characterized by rapid urbanization.
• Degradation of biological communities by riparian and bottom habitat losses, river channel modifications, construction of locks and dams, increasing backwater sedimentation rates and loss of wetlands, effects of reservoir operations on fisheries, and eutrophication.
• Contamination of bottom sediments in the river with toxic chemicals and subsequent benthic release and bioaccumulation of toxic substances within the aquatic food chain.
Water quality in the Upper Mississippi River, as measured by indicators presented in this chapter such as DO, ammonia, fecal coliform bacteria, and sediment levels of mercury, has improved greatly since the 1960s and 1970s as a result of upgrades to wastewater treatment plants required by the 1972 CWA. Despite these improvements, contaminant loading from municipal (nutrients) and industrial (heavy metals, toxic chemicals) dischargers and runoff from urban (heavy metals) and agricultural (nutrients, pesticides, sediments) watersheds continue to adversely affect the ecological integrity of the Upper Mississippi River. In addition to chemical inputs to the river, the Upper Mississippi River Conservation Committee has warned that the ecosystem of the Upper Mississippi River is threatened by structural alterations of the river such as continued stream channelization, flood control levees that separate the river from the floodplain, and the proposed expansion of the commercial navigation infrastructure (UMRCC, 1994). If the current ecological benefits are to be maintained and degraded ecological conditions restored, an ongoing effort will be needed to maintain environ-
mental monitoring and research programs to document the status and trends of the Upper Mississippi River to provide the scientific data needed for effective resource management decisions (USGS, 1998).
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