Jonathan De Graaf, Anthony Harbaugh, and Austin Van Vuren
We worked with the City of Sioux Center to create two possible storm sewer designs for a residential housing subdivision being planned for the undeveloped farmland to the west of the current hospital. The proposed storm sewer will collect and channel surface street runoff away from the development.
Our first design utilizes a buried 48-inch diameter concrete pipe that would handle most rain events and would work in combination with the street to channel runoff from large rain events. The estimated cost for this design is approximately $250,000. Our second proposed design utilizes a concrete or grass open-channel to accommodate the runoff from any rain event at an estimated cost of $40,000-$110,000 (depending on how the channel is lined). For comparison, we estimated the cost of an all-pipe design to be $850,000. We presented the city with the benefits and drawbacks of each design alternative so that they can make an informed decision as they move forward in laying out the development.
Both designs incorporate a dry detention basin (meaning that the basin will only be filled with water during large rain events). This detention pond will be centered on the stream that presently runs to the east of the development allowing the stream's flow to be adjusted as needed to accommodate the un-detained water from the subdivision. This design will also mitigate the effects of the development on downstream locations by ensuring net-zero increase in flow from the pre-development conditions.