Dean’s Lake Stormwater Pump Station

HR Green was retained by the City of Des Moines to design a stormwater pump station to pump water from the protected side of the U.S. Army Corps of Engineers’ flood levee to the Des Moines River during high river conditions. Previously, temporary pumps were mobilized to perform this task, pulling staff away from other needs of the system. The Dean’s Lake Stormwater Pump Station design involved coordination between the City of Des Moines, Des Moines Wastewater Reclamation Authority (WRA), and the U.S. Army Corps of Engineers.

HR Green conducted hydraulic and hydrologic modeling of the Dean’s Lake drainage basin. The pump station was designed to provide the capacity needed to protect the basin from flooding and to convey the stormwater flow from an I-235 drainage project.

HR Green provided preliminary and final design and construction phase services for the new stormwater pump station. The design had to meet the following objectives: pump 200 cubic feet per second (120 mgd); determine the best screening technology; design the foundation for unsuitable soils; maintain conveyance of design flows under low Des Moines River conditions; maintain levee top as a pathway for travel; perform an economic evaluation to choose between submersible propeller pumps and screw pumps; provide a secure location for the equipment; and provide standby electrical generation for reliability.

Based on this information, a cast-in-place concrete structure was designed to house the pumps and electrical equipment. The pumps and electrical equipment were procured by the City of Des Moines through their service agreement with Electric Pump. The pumps are started using reduced voltage starting equipment to minimize the impact on the utility and surrounding users. Future development of the Dean’s Lake drainage basin is probable with a major transportation corridor being planned for this area. The Dean’s Lake Stormwater Pump Station included architectural features to be pleasing to the eye. A strict construction sequence was prepared to allow for ongoing conveyance of Dean’s Lakes flows and protection from fluctuations of the Des Moines River levels. Milestone dates were incorporated into the documents to maintain these requirements and schedule the work during the winter low-flow time of the year. The design included structural, architectural, process, civil, and electrical disciplines.