Skunk River Basin, Waste Load Allocation Study, 1974

(1974) Skunk River Basin, Waste Load Allocation Study, 1974. Natural Resources, Department of

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Abstract

The Skunk River Basin encompasses an area of approximately 4,355 square miles as a long, narrow drainage basin flowing from central to southeast Iowa. Topography is rolling and the drainage pattern of the basin is tree-shaped (dendritic). Stream flows per square mile in the Skunk River Basin are generally less than those of the state of Iowa as a whole, especially for the 7-day, 1-in-1O year low flow. Most of the main streams in the basin have a Class B (warm water fisheries) water quality criteria classification. There is a lack of comprehensive water quality data on existing conditions within the basin. Within the basin, 78 communities are incorporated. Of these, 51 have wastewater treatment facilities. Also, there are 28 industrial and 27 semipublic wastewater dischargers. Twenty-five municipalities maintain wastewater treatment facilities which will not be required to adopt a controlled discharge mode of operation under the National Pollutant Discharge Elimination System (NPDES). To determine allowable waste load allocations for these 25 dischargers, a computer model based upon a modified Streeter-Phelps equation was utilized. Input data to the model included such physical characteristics as length of reach, water temperature, channel slope, river width, roughness coefficient, deoxygenation rate constants, wastewater discharge characteristics, and flow and characteristics of groundwater and tributaries. The model approximates the impact of dischargers on stream quality for the specified winter and summery low flow conditions. Wherever stream quality criteria were not met by secondary treatment, reductions were made in the allowable wastewater discharges until satisfactory conditions prevailed.