V&K worked with the City of Des Moines to design a major stormwater drainage improvement project in the River Bend and King Irving area, which received a new sewer pump station after a major flooding event in 1993. With the separation of the sewer in this neighborhood, we concluded that the pump station wouldn’t be able to handle all of the potential stormwater. We started with an extensive stormwater drainage report, which included a digital model of the drainage basin where new improvements would be required, as well as the areas of the existing storm sewer system. The area provided a unique challenge, requiring a new stormwater pump station as the ground elevations are too low for a gravity outlet during flood conditions.
Developed by V&K, the plan involved a five-phase storm sewer improvement program. The unique system is designed to function as a pressure storm sewer that will discharge into the Des Moines River without the need for a pump station. All of the storm sewers above a certain elevation function in a conventional manner, and all of the storm sewers at a lower elevation are isolated pressure sewers with no openings that would allow water to enter or leave the pressure sewer. This design reduced the overall project cost by approximately $5,000,000.
The storm sewer project involves extensive work on street reconstruction and the project phasing was designed to reduce the disruption in the neighborhood. The first three phases involve extending the storm sewers located in the higher elevation, and the two remaining phases involve adding the pressure sewer elements. Construction for the first pressure sewer, phase four, will begin in the fall of 2021, when the Corps of Engineers will allow construction through the levee. The final pressure sewer will be rolled into the 2nd Avenue reconstruction project to be completed in 2023 or 2024.