Southern Illinois Reliability Project

Ameren Illinois is rebuilding an existing 230 kV transmission line and associated facilities from Cahokia to Joppa. The existing line was originally built in the 1950’s and will be rebuilt as a 345 kV line to better align with Ameren Illinois' current energy system and to create additional customer benefits. Replacing the aging infrastructure and enhancing this transmission line will improve energy reliability, promote access to renewable energy like solar and increase transmission capacity. The rebuild will occur in six construction phases along the existing transmission corridor. The Southern Illinois Reliability Project is proposed to be in service by Fall 2023.

The Project will improve energy reliability, promote access to renewable energy like solar and increase transmission capacity for Illinois residents, businesses and communities.

The Southern Illinois Reliability Project will rebuild aging infrastructure and enhance our energy system to improve reliability for the future energy needs of our customers, businesses and communities. This project increases transmission capacity and promotes access to renewable energy sources like solar.

The Project is located in the following Illinois counties: St. Clair, Washington, Perry, Franklin, Williamson, Johnson and Massac counties.

We anticipate beginning construction in Fall 2020 and completing the project by Fall 2023.

 

Ameren Illinois is currently in the public outreach phase of the Project. There will be ongoing outreach with stakeholders, landowners, businesses, and other community members before, during, and after construction. Our schedule currently anticipates seven construction seasons starting in Fall 2020. Preconstruction activities will begin in Summer 2020.

Transmission lines are similar to the interstate highway system in the way they allow energy from generation sources, including renewables, to travel short or long distances, as needed at any given moment.

In June 2019, Ameren Illinois representatives will begin reaching out to landowners along the transmission route. Letters will be mailed to landowners requesting a meeting to discuss project details, which will include property rights needed, compensation and property access.

The Project will be utilizing steel h-frame structures directly embedded into the ground. They will be approximately 80 ft tall. Structures will span approximately 800 ft depending on topography and area features, meaning there will be an average of six to seven structures per mile. The conductor clearance standard for the rebuilt 345 kV line is 25 ft from conductor to grade.

The current 230 kV wooden H-frame structures are approximately 65 ft. tall and directly embedded into the ground. The minimum ground clearance for the existing 230kV line is approximately 23 ft. There is roughly 8 structures per mile and an average of 600-700 ft. spans.

The Commodore to St. John segment will be using double-circuit, steel monopole structures. The structures will be approximately 125 feet tall with a 9-12-foot diameter poured concrete foundation. There will be approximately six to seven structures per mile. 

Before construction begins, Ameren Illinois will access each property survey for legal boundary, depth of foundation and environmental sensitivities. These preconstruction activities are necessary to ensure sound design and planning of the project and help us address and understand any concerns or unique property features that may be present.

To properly design each transmission line structure, our engineers need information about the soil where the structures will be located. The soil data we gather will help our engineers determine the final design and structure locations, and help to minimize impacts to cultural and biological resources during construction.

The collection of soil information is completed using the following steps by our project team:

• Partner with our real estate team Salem Group to request property access.
• Gather samples by our geotechnical field crews from site location by digging a 4-6 inch wide hole into the ground, known as a soil boring. Soil boring areas will be back-filled in after the survey.
• Review the soil samples to determine the physical properties and layering of the soil.
• Use the soil information collected to design each foundation and structure dimensions.

Ameren Illinois is committed to providing safe, reliable and dependable energy to our customers, businesses and communities. To deliver on that commitment, our vegetation management team must ensure proper clearances around the lines required by federal and state agencies. Trees and other vegetation growing around the lines can hinder our ability to safely and reliably deliver electric services. They can make the job of storm restoration more difficult, extend restoration times and pose additional hazards to our line crews. For safety and reliability reasons, incompatible vegetation such as incompatible trees, and tree limbs throughout the Project area will be removed from the ROW.

Construction is scheduled to begin in Fall 2020 and will occur over the course of four years. Preconstruction activities will begin in Summer 2020. The Southern Illinois Reliability Project's construction will occur in the following six phases:

Segment 1: Cahokia-Prairie State- Fall 2020-Spring 2021
Segment 2: Prairie State-Aster- Spring 2021
Segment 3: Aster-Commodore- Fall 2021
Segment 4: Commodore-St. John- Fall 2023
Segment 5: St. John-Jordan- Spring 2022
Segment 6: Jordan-Massac- Fall 2022- Spring 2023

The Southern Illinois Reliability Project cost is approximately $385 million.