Design of Logan City's Storm Water Conveyance System

Megan Gordon, Utah State University


Logan City is located in northern Utah’s Cache County. The average annual rainfall for Cache Valley is between 15 and 20 inches (PRISM 2016). Several times a year, the incomplete storm water system causes flooding, which risks industrial and agricultural lands. The current system collects storm water between 200 West and 1000 West, and discharges the water directly along 1000 West.

Cutler Reservoir, Swift Slough, and the Lower Bear River in Cache Valley do not comply with water quality regulations. The Clean Water Act of 1972 mandates that all municipal separate storm sewer systems (MS4) comply with EPA regulations, expressed as Total Maximum Daily Loads (TMDLs). Logan City’s untreated storm water might contribute to the pollution in these water bodies. The pollution threatens surface water, groundwater, and wildlife in the area.

Logan City plans to implement a new wastewater treatment process. However, the new treatment process is not designed to use the existing polishing ponds. Consequently, Logan City hopes to use these polishing ponds to treat storm water.

The implementation of this design improves storm water management. 10th West Engineers (10WE) had three goals. First, design a system to transport water from the discharge locations to the holding pond. Second, design a system that provides irrigation users access to water during a storm. Third, comply with the goals of the client: design a gravity-fed system, minimize effect on wetlands, and produce an economical design.