Des Moines Wastewater Reclamation Authority
Westside Pump Station Improvements

The Des Moines Wastewater Reclamation Authority (WRA) Westside Equalization Basin and Pump Station was constructed in the late 1980’s as part of the WRA conveyance system. The facility consists of a 4.8 million gallon underground equalization basin and a 20 mgd pump station. The facility discharges in to the Westside Interceptor that is a force main/pressure sewer. The force main has a capacity of 35 to 40 mgd. The facility is impacted by significant inflow and infiltration. During storm events the facility cannot keep up with the tributary flows and inundation of the equalization facility has occurred on several occasions. Howard R. Green Company was retained to provide preliminary, design, and construction phase services for expansion of the Westside Basin and Pump Station.

Objectives included:
		upgrade the capacity of the pump station from 20 mgd to approximately 40 mgd;
		review the screening installation to determine if a different technology should be used in place of the catenary screens;
		generate a new force main hydraulic model to evaluate downstream effects of upsizing the pumping station including surcharging, transient effects, and force main velocities, etc.;
		wetwell modifications, in accordance with Hydraulic Institutes Standards (HIS), to allow for up to 40 mgd to reach the pumps; and
		parallel force main expansion to allow for the increased flow to reach the 48-inch pressure sewer.

The findings allowed for no more than 36 mgd to be pumped by the station without major improvements in the 48-inch interceptor. Also to get the flow to the 48-inch interceptor a parallel 30-inch forcemain was required. Due to budget constraints, the existing station was retrofitted with the new equipment to meet capacity. Design required accommodating larger equipment installation/removal and larger pipe routing in limited space. A strict construction sequence was prepared to allow for one-half of the station to be removed from service to allow for the new construction. The new pumps, electrical system, and catenary bar screen were put into service before the second half of the station was demolished and modified.

The construction project was completed a few months before the contract completion dates without major issues. The final construction cost was considerably under the project budget amount. The new West Side Basin Pump Station was successfully hydraulically tested.

Read the recent article highlighting this improvements project in Water & Wastes Digest, 2008, Vol. 48, No. 7.