Combined Sewer Relief (CSO)

As part of the City’s Combined Sewer Overflow (CSO) Long-Term Control Plan (LTCP) to reduce wet-weather sewer overflows, a new large-diameter interceptor sewer was installed along a major city thoroughfare and within a very tight schedule of 18 months for design and construction.

Originally scheduled for construction in 2019, the project was expedited several years in order to complete construction prior to the State Street Renovation, a joint project between the City and Purdue University which included major roadway improvements in this same area. Installing the new Interceptor earlier avoided disturbing and replacing the new roadway improvements. Design of the project started in July 2015 and construction was completed in February 2017.

In order to expedite the project schedule, the City utilized the Guaranteed Savings Contract (GSC) method of procurement. GSC is a form of design-build, where the contractor is selected based on experience and qualifications and becomes part of the project team, working alongside the engineer for final design. Wessler worked closely with the contractor during 60% and 90% design, conducting value engineering workshops to modify the design to improve constructability and reduce construction costs without compromising quality and performance. A Guaranteed Maximum Price based on 60% design documents was submitted in December 2015, at the same time of permit submittals, to meet the construction start date of March 1, 2016.

The new Interceptor includes 4,500 feet of new 60 inch and 96 inch sewer along two lanes of River Road. The new sewer intercepts two combined sewer overflows, which would otherwise flow to the Wabash River. The 3,400 feet of 96 inch pipe provides an in-line storage volume of 600,000 gallons, which is stored and slowly conveyed to WWTP for treatment. The project is designed to meet a 10-year/1-hour design storm without overflows. Oversizing the sewer to provide in-line storage avoided adding that storage at the WWTP, which was estimated to cost $6,000,000.

Major traffic and pedestrian routes were impacted by the project. A Maintenance of Traffic (MOT) and pedestrian detour plan was developed, including a major street closing at State Street and River Road, one of the busiest intersections in the city and a main artery from the City of Lafayette. Media releases and maps were prepared to notify the public of the traffic and pedestrian detours, including a highly publicized public and media presentation, a dedicated project website with continuous updates, texts, radio and television news announcements, and numerous newspaper articles.

A very quick turnaround for permits was needed for the project to stay on schedule. The IDEM (Indiana Department of Environmental Management) Construction and Rule 5 Permits were submitted in December 2015 and received in less than 2 months, allowing construction to start on schedule in March 2016.