Construction of the new I-69 corridor between Evansville and Indianapolis was vitally important to the economy’s growth and mobility for southwestern Indiana. This interstate helps bring jobs and improve healthcare and education access to those throughout the region and Indiana.
Section 5 began south of Bloomington in Monroe County at SR 37 and continues northward for approximately 21 miles to SR 39 on Martinsville’s south side in Morgan County. The project included converting the existing SR 37 with several at-grade crossings to a limited access interstate quality highway. DLZ reconstructed twenty-one miles of mainline pavement with added travel lanes in key locations. DLZ constructed or reconstructed thirty bridges to accommodate the conversion. Also built or rebuilt were interchanges at key locations. Construction along the s-lines at the interchanges included both roundabout and signalized intersections.
Initially organized and financed as a Public-Private Partnership, in August 2017, the project transitioned to an INDOT-sponsored design-build structure. Throughout the project, DLZ supported the construction oversight teams, complete roadway design, bridge, small structure design, drainage design, utility coordination, and traffic maintenance plans. Additionally, design teams worked to finalize preliminary plans with input from field construction personnel in a design-build environment.
Tasks for the design of I-69 Section 5
The constructability review included a technical review of plans to ensure that the contractor could construct the plans as shown. The proposed design met the standards set by the project’s Technical Provisions and the Indiana Design Manual. This was in part to review hydraulic designs completed by others outside of DLZ.
DLZ was responsible for completing the hydrology and hydraulics designs for numerous small structures (less than 36-inches) drainage culverts needed along access roads and driveways where previous structures did not exist. This also included underdrain to the entire 22 mile stretch of the project.
The addition of travel lanes and proposed limited access interchanges generated the need for several new culverts to be included in the final design. DLZ worked on sizing several large structures (culverts larger than 36-inches) throughout the project. These also included new structures to replace existing drainage culverts that are undersized to meet the new standards. DLZ designed 38 new structures constricted with Jack and Boring method, 22 structures lined with HDPE or slip lined, and two structures and completed them with a newer Centrifugally Cast Concrete Pipe technology. To achieve these structures, DLZ used HY8 and other INDOT approved computer modeling software to size replacement structures adequately.
The addition of access roads and driveways created challenges along the route regarding new ditches and drainage swales due to the narrow right-of-way, soil and bedrock, and varying slopes. DLZ designed several ditches, drainage features, and detention areas to facilitate positive drainage throughout the project within these limited spaces using HydroCAD and HEC-HMS to meet design criteria.
I-69 Storm Sewer Design
A large stretch of I-69 required creative storm sewer design in the median. This was due to limited cover, greatly varying slopes, and a large amount of additional impervious area for the project. This required innovative solutions, including a modified inlet design in a trunk line sewer that would function properly to allow for proper drainage and eliminate erosion control problems created before vegetative growth. Design of the trunk line sewer utilized in the project saved millions of dollars by eliminating numerous expensive borings under the new travel lanes.
DLZ also did the detention basin design for over 215 basins throughout the corridor. Several basins were interconnected, requiring complex modeling in HEC-HMS to complete. Multi-stage basin outlet design, grading, and riprap protection were included in each basin design.
DLZ was responsible for overseeing and completing several permit modifications regarding 401 and 404 compliance.