Updated: 04/11/25

Overview

On June 25-25, 2021, the City experienced a historic rain event that produced more rainfall than a 500-year storm and caused citywide flooding. Flooding in the City following a major storm event is primarily caused by undersized combined sewer mainlines, and the City is actively working to address problem areas in a cost-effective manner.

Project Description

The proposed East Street Detention Basin and Sewer Improvements project is a largescale, multi-phase project that will divert and detain stormwater using sewer separation for diversion and detention basins for detainment. The project will also serve as a community asset, providing green space and recreation opportunities to the community.

The location of the East Street basin was determined to be a feasible option to reduce the impacts of storm water runoff in the report titled, 2014 City of Bloomington Stormwater and Sanitary Sewer Master Plans, which included some preliminary citywide hydraulic modeling that is the basis for this ongoing work. The current hydraulic modeling work is utilizing more sophisticated software and more detailed inputs to develop the best recommendations moving forward. It is a large effort using geographic information system data, rainfall data, flooding data, and detailed topography.

Project Map

Click here to download a PDF of the project map.

Phase 1: Pipe Relocations

Phase 1 includes construction of a 60-inch combined sewer pipe located along the south side of the properties where the Citizen Convenience Center, Public Works building, and Public Works yard currently sit, parallel to the railroad tracks. It will connect to the existing sewer on the west side of these properties. This is necessary to intercept stormwater along Oakland Avenue and convey it into the proposed East Street Basin, which will provide relief to the existing combined sewer and reduce flooding upstream and downstream of the basin. This phase also includes relocating existing combined sewer that conflicts with the proposed basin that would be constructed in Phases 2 and 3.

Design of Phase 1 began in March 2025. Additional information will be added as the phase progresses.

Phase 2: Basin East of East Street

Phase 2 includes excavation of the basin, inlet, and outlet flared end sections of the basin, the pipework on Jackson and Prairie Streets, and the pipe connecting to the future Phase 7 Basin West of East Street. Roadwork during this phase would include reconstruction of East Street, Jackson Street, and Prairie Street around the basin.

Design of Phase 2 has not begun at this time. Additional information will be added as the phases progress.

Phase 3: Landscape Design – East Side

Phase 3 includes the Wet Bottom Basin Fountain Waterfall, Trail Connection – East Edge, Story Walk, Wetland Discovery Walk, Modal Parking with One-Way Traffic – Prairie Street, and Parking with Two-Way Traffic – Jackson Street.

Design for Phase 3 has not begun at this time. Additional information will be added as the phases progress.

Phase 4: Oakland Avenue

Phase 4 includes installing a 60-inch by 72-inch horizontal box culvert for storm sewer, replacing the existing combined sewer pipe with a 60-inch by 60-inch box pipe, and constructing a 72-inch equivalent storm sewer mainline parallel to the combined sewer along Oakland Avenue, from Clayton Street to Gridley Street. This is necessary to intercept stormwater along Oakland Avenue and convey it into the proposed East Street Basin, which will provide relief to the existing combined sewer and reducing flooding upstream and downstream of the basin. This phase also includes relocating existing combined sewer that conflicts with the proposed basin that would be constructed in Phases 2 and 3.

Design of Phase 4 began in March 2025. Additional information will be added as the phase progresses.

Phase 5: Baker-Ash Basin

Phase 5 includes upsizing pipes connecting the Baker-Ash Basin and the ditch along the west side of the basin, which would replace the existing basin outfall pipes. These improvements will send more water from the ditch into the basin during peak flow conditions and lower flow into the Big 4 Valley Relief sewer.

Design of Phase 5 has not begun at this time. Additional information will be added as the phases progress.

Phase 6: Clayton-Miller Basin

Design of Phase 6 includes adding new storm sewer pipes along the northern streets of the neighborhood to eliminate 10-year flooding, relieve flow into the combined sewer, and discharge into a proposed basin near the intersection of South Clayton and East Miller Streets. The roadwork for this phase will include street patching along the route of storm sewer installation.

Design of Phase 6 has not begun at this time. Additional information will be added as the phases progress.

Phase 7: Basin West of East Street

Phase 7 includes an additional basin on the west side of East Street, similar to the footprint of the larger East Street Basin and will connect to the pipe work set up during Phases 1 and 2. The West Basin will include sidewalk, lighting, and plantings.

Design of Phase 7 has not begun at this time. Additional information will be added as the phases progress.

Phase 8: Landscape Design – West Side

Phase 8 includes construction of the remaining landscape design amenities, as well as the Wet Bottom Basin, wetland restoration, wet bottom basin central water fountain, wet bottom basin fountain waterfall, north gateway entrance, south gateway entrance, social plaza, and wetland discovery walk.

Design of Phase 8 has not begun at this time. Additional information will be added as the phases progress.

History

Council approved a contract with Baxter & Woodman on October 25, 2021, following the storm events that caused flooding in June 2021. The contract included project coordination and data collection, sewer system assessment, preliminary design, final design, and assistance during bidding.

The Engineering Department and its consultant, Baxter & Woodman, Inc., presented project updates and recommendations for the East Street Detention Basin and Sewer Improvements project at the City Council meeting on November 20, 2023. The presentation reviewed the existing conditions, hydraulic modeling, and engineering work done to date along with recommended alternatives and phasing of proposed improvements.

You can view the video of the presentation below or download a PDF of the presentation here.