The Metropolitan Water Reclamation District and Forest Preserves of Cook County are partnering in a flood relief study in the southeast suburbs that could bring a new reservoir.

The two agencies announced a 20-month study to assess the potential for the district and forest preserves coordinating and sharing costs for the planning, design, construction and maintenance of a Deer Creek-Third Creek Reservoir.

If feasible, the system would provide naturalized stormwater storage for flood-prone communities in Glenwood, Ford Heights, Lansing, Thornton, South Holland, Calumet City, Dolton and unincorporated areas.

The proposed project could cover nearly a square mile area along Deer Creek and Third Creek within the Little Calumet River Watershed near Glenwood and Ford Heights, where stormwater storage can help mitigate increasing flooding concerns, according to the MWRD and forest preserve district.

The reservoir would be located roughly near Cottage Grove Avenue between Glenwood Dyer Road and Lincoln Highway within the Deer Creek Watershed in Cook County, according to the MWRD, but many of the specifics will be researched during the study.

The district said the reservoir might not be a single water-holding structure but could include adjacent wetlands, creeks, ponds and lakes.

The MWRD said new rainfall data published by the Illinois State Water Survey in 2020 shows raised flood elevations along the Little Calumet River in South Holland, Dolton, Calumet City and Lansing.

Flood waters from Deer Creek and Third Creek flow into Thorn Creek before reaching the Little Calumet River.

Proposed channel improvements along Deer Creek would direct flood water into new flood storage areas adjacent to the creeks. The new stormwater conveyance and storage improvements would give the region more room to accommodate increasing stormwater demands, according to the MWRD and forest preserves district.

The land in the project could potentially be larger than one square mile, which would accommodate more than 500 million gallons of naturalized stormwater storage, according to the agencies.

In planning stormwater projects, the MWRD has said it looks at the increased frequency of major storm events in the Chicago area, including one-day and multiday storms that can overwhelm sewer systems in older communities.

In some suburbs, combined sewer systems carrying both sanitary and storm water lead to a combination of backups of sewage and rainwater.

As part of its Tunnel and Reservoir Plan, also referred to as Deep Tunnel, the MWRD built the Thornton Reservoir on the north side of Interstates 80/94 in South Holland. It was designed to divert both sanitary and stormwater flow from Chicago’s South Side and south suburbs and has a capacity of just under 8 billion gallons.

In September 2022, the district completed work on the Thorn Creek overflow tunnel that diverts stormwater from the creek into the reservoir.

Along with the Thornton reservoir, the MWRD operates smaller reservoirs in Ford Heights, Hazel Crest, Lynwood, Markham and Tinley Park that have a combined capacity of just under 1 billion gallons and handle stormwater runoff from the Little Calumet River watershed.

The proposed Deer Creek-Third Creek Reservoir has already received grant funding assistance through the American Rescue Plan Act, the federal government’s COVID-19 assistance program, and the Federal Emergency Management Agency, according to the MWRD.

The committed budget for the 20-month feasibility study is $1.7 million, excluding construction costs, according to the district.

Between the resecue plan funds and FEMA, more than $1.2 million has been obligated to fund preliminary work, including the study, according to the district.

The MWRD will pay for the remaining costs of the feasibility study, but the overall estimated cost of the project has not yet been determined.

The MWRD and forest preserve district said they will continue to pursue additional funding assistance for future phases of the project.

Once the feasibility study concludes in the fall of 2026, community meetings will be held to gather public input, according to the MWRD and forest preserve district.

In June 2023, the MWRD authorized a negotiation of an intergovernmental agreement with the Forest Preserves to study flood control in the southeast suburbs.

The agreement, formalized this past May, calls for the MWRD to pay for concept planning and preliminary engineering design while the Forest Preserves will pay for acquiring property.