The City of Lacey’s topography consists of rolling terrain that has resulted in 47 lift stations, 2,500 septic tank effluent pump (STEP) systems, numerous grinder pumps, and gravity sewers to serve the residents of the City. BHC developed a comprehensive system wide dynamic model to determine deficiencies in the existing system, plan for system expansion, and review opportunities for lift station abandonment. The STEP system was represented in the model by clustered pump stations to mimic changes in flow and pressure without adding unnecessary complexity and adversely impacting model runtimes. The model was calibrated using measured flow and STEP system pressure data. Because of the large number of pressurized systems needed to overcome the terrain, future sewer expansions could connect to several existing trunks, allowing the City to optimize the capacity of their existing infrastructure. BHC analyzed several alternatives for sewer expansion in order to come up with a recommendation to optimize the capacity of the existing piping and pumps. After reviewing the results for the STEP expansion alternatives, an efficient, prioritized CIP was developed to help the City address existing capacity concerns and plan appropriately for growth.
- InfoSWMM model of a sewer with 47 pump stations and 2,500 STEP systems
- Modeling used to optimize existing infrastructure and minimize capital costs in future system expansion
- Prioritized capital improvement program