Effects of CSO Basin Discharge on River Water Quality

The water quality of the Iron Mountain/Kingsford, Michigan's combined sewer overflow events and the impacts of the overflow on the water quality standards of the Menominee River are presented in this paper.The Menominee River is a major scenic and recreational river and is also the boundary between the state of Michigan and the state of Wisconsin. It flows along the southern edge of the Iron Mountain-Kingsford sewer service area. Forty CSO overflow events occurred during the years 1994 through 1997. Four of the overflow events occurred during the impact evaluation period between June 15, 1997 and October 13, 1997. In-stream monitoring established conditions in the river during and after discharge events. Water quality data of the overflows, and water quality upstream and downstream of the CSO Basin discharge are evaluated.Water quality monitoring probes in the Menominee River upstream and downstream of the CSO Basin discharge collected dissolved oxygen, temperature data of the river at fifteen-minute intervals throughout the study period. Grab sample data from the effluent of the CSO Basin during each discharge event was collected. Data evaluated presented and include the following parameters: DO, BOD, TSS, TKN, Ammonia N, Nitrate N, Nitrite N, P, Cd, Cr, Cu, Ni, Pb, Zn, Hardness, Temperature and Total Organic Carbon.Based on the data collected and the results presented in this paper, the overflow from the CSO retention basin does meet the Michigan Water Quality Standards during the overflow discharge events. The results of the evaluation presentation indicate the combined sewer overflow retention basin provides at least the equivalent of primary treatment and the overflows are disinfected.The results of the evaluation presented demonstrate the annual load of suspended solids and BOD from the basin overflows are insignificant compared to the background characteristics of the Menominee River upstream of the CSO outlet. The data presented in this paper also demonstrate the overflows from the combined sewer retention basin has little, if any, effect on the sediment oxygen demand in the Big Quinnesec flowage of the Menominee River. Data and information further demonstrate the total load of pollutants discharged from the CSO Basin during the duration of each discharge are insignificant compared to the total load in the river for that same time period.The results of the river monitoring demonstrate the dissolved oxygen at the monitoring point downstream does not go below the Menominee River water quality standards following discharge events. The data collected, analyzed and presented in this paper demonstrate dissolved oxygen at the monitoring point downstream of the outfall did not fall below the Menominee River standards following discharge events. The results presented in this paper demonstrate the CSO overflow events had little, if any effect on the downstream dissolved oxygen concentrations.Mass balance calculations to demonstrate overflow discharges meet the Rule 57 values for cadmium, chromium, copper, lead, nickel, and zinc after mixing with 1/4 of the actual Menominee River flow during an overflow event. The mass balance calculations demonstrate the combined sewer discharges comply with the effluent-based water quality effluent limits for toxic substances. The information presented within the paper, demonstrate the CSO effluent concentrations fall well below the requirements of Rule 57.In summary, this engineering paper presents the results of the water quality sampling of the CSO Basin overflow and Menominee River. The paper also provides an evaluation and analysis of the effects of the CSO Basin overflows on the physical and chemical characteristics of the water quality of the Menominee River. It demonstrates the water quality standards are not violated due to overflow events from the Iron Mountain-Kingsford combined sewer overflow retention basin.