McHenry County Division of Transportation

IL Route 31 Algonquin Western Bypass

A Much Needed Improvement, a Long Time in the Making

The final design of the IL Route 31 Algonquin Western Bypass was a result of many years of planning and coordination with several agencies including the Illinois Department of Transportation, the McHenry County Division of Transportation, the US Army Corps of Engineer, the Illinois Environmental Protection Agency, the McHenry County Conservation District and the Village of Algonquin. 2.5 mile segment of this principal arterial roadway was constructed along a new alignment through an existing gravel mining operation. The final project scope of work was a result of a Congestion Mitigation Feasibility Study initiated in 1996 to develop solutions to the congestion experienced at the IL Route 62/IL Route 31 intersection in the downtown district of the Village of Algonquin. The study included reviewing traffic which passed through the communities of Algonquin, 山间湖泊, 凯里和水晶湖. The final alignment of the Western Algonquin Bypass provided the most capacity to handle traffic with the least impacts on the communities involved.

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Complex Site Preparations

In order to build the proposed improvement, four contracts had to be let; building demolition, hazardous materials mitigation, 质量分级, 和道路建设. 单独的PS & E’s were developed for each contract. Due to the manufacturing that took place on some of the acquired parcels, the presence of heavy metals was found in the soil during the Preliminary Environmental Site Assessment (PESA) and Preliminary Site Investigation (PSI) which required including clean up with the proposed improvement. The 质量分级 contract was let in advance of the Roadway Construction Contract. The contract consisted of the grading needed to prepare for the proposed new four lane divided roadway. 这项工作, 在阿尔冈昆路以北, included storm sewer and culvert removal, 树删除, installation of 风暴下水道 and drainage structures, detention basin construction, earthwork and restoration of disturbed areas to prevent erosion.


The roadway construction contract included a new four lane divided highway and diamond interchange at Algonquin Road, as well as four new bridges, 大量的挡土墙, 噪音墙, new traffic signals at five intersections, 道路照明, 风暴下水道, and utility improvements for the Village. The Village of Algonquin’s Towne Park was reconfigured as part of the contract and included many enhancements. Crystal Creek was relocated back to its natural alignment within Towne Park. The new bridges were designed with aesthetic elements and decorative lighting and are all within view of the park. The McHenry County Conservation District multi-use path was realigned to now wind through Towne Park providing its users with parking, 卫生间, benches and drinking fountains. Also, the improvements also included a new 100-stall parking lot.

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Improving Capacity for Years to Come

The final project, completed in 2014, provided a grade separated interchange at IL Route 62. Traffic signal timing was revised to allow more green time on IL Route 62 improving traffic flow dramatically along both routes and eliminating the typical 15-minute intersection delays experienced during the peak travel periods. Traffic flow through downtown was improved and heavy truck traffic was moved off of Main Street. The improvement increased capacity, minimized operational and safety deficiencies, and satisfied travel demands projected to 2030 within the corridor.

This Project Incorporates the Following:

  • Increasing traffic capacity while minimizing community impact
  • 工业场地清理
  • Multiple interrelated contracts
  • 溪搬迁
  • 立体交叉
  • 停车场设计
  • Meeting travel demands to 2030


  • Roadway and Highway Design
  • 排水设计
  • 地形测量
  • Traffic Signal and Signal System Design
  • 照明设计
  • Geotechnical Investigation
  • 路面设计
  • 跨部门协调
  • Preparation of Contract Plans,
  • Specifications, and Estimates
  • 公路桥梁
  • Bikeway and Pedestrian Facility Design
  • Type, Size, and Location Drawings

Learn more about this project

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