Citizens Energy Group made a significant change to their Septic Tank Elimination Program (STEP) by electing to install only low pressure sewers (LPS). The LPS have smaller pipe diameters which can be installed via directional drilling. This greatly reduces the impact on the neighborhoods. Additionally, the LPS sewers eliminate potential inflow and infiltration into the sewers, a major consideration for this project area as it is in the ﬂoodplain of the White River.
This project was also the ﬁrst STEP project for Citizens Energy Group that was completed as a design-build project. Shrewsberry partnered with Miller Pipeline to perform the design engineering, permitting and construction administration services.
The project includes over 60,000 linear feet of low pressure sewer to serve approximately 900 homes. During the project, Shrewsberry worked with the Citizens Project Manager, Miller Pipeline, and the grinder pump manufacturer to optimize the LPS for more efficient installation and more effective maintenance. This included drastically reducing the number of ﬂushing stations and air/vacuum release valves, and installing isolation valves.
In order to ensure long-term operation of the LPS, Shrewsberry speciﬁed the required vent type for each grinder pump. Three different vent types were specified based on the expected ﬂood depth during a 100-year ﬂood event.