This project profile documents a Preliminary Site Investigation Project Profile from 2022 — an IDOT PSI A3 Environmental Consultants performed at the Vandalia Maintenance Yard. A PSI is the corridor- and facility-scale equivalent of a Phase 2 ESA — if you’re new to the process, start with what a Preliminary Site Investigation (PSI) is and how it follows a Preliminary Environmental Site Assessment (PESA).
Weston Solutions is an engineering and environmental consulting company located in West Chester, Pennsylvania. Serving the Chicago metropolitan area out of Lincolnshire, Illinois, Weston Solutions partnered with A3 Environmental Consultants on various projects for the Illinois Department of Transportation (IDOT).
Inside This Preliminary Site Investigation Project Profile
A3E was subcontracted by Weston Solutions to perform a Preliminary Site Investigation (PSI) and report for the Illinois Department of Transportation, investigating potential subsurface contamination within the proposed area for a new maintenance building at the IDOT Vandalia Maintenance Yard 712 (Vandalia Yard) in Vandalia, Illinois as part of PTB-179. The investigation was undertaken to determine the presence and nature of subsurface contamination in specific areas of the existing and proposed IDOT Right of Way (ROW), and to evaluate the lateral and vertical extent of contamination within the proposed construction area that could prevent timely completion of the IDOT construction project.
From PESA to PSI
The Illinois State Geological Survey completed a Preliminary Environmental Site Assessment (PESA) for this property and determined that further subsurface investigation was warranted. A3E advanced a total of nine borings across the site to a depth of 8 feet. We evaluated the data to determine the contaminants of concern in the soil and compared them to Clean Construction & Demolition Debris (CCDD) Maximum Allowable Concentration (MAC) values for soil disposal at a clean fill facility. A3E coordinated the field efforts and subcontracted the drilling firm for the project, kept Weston informed of the field schedule, and communicated analytical results ahead of the report being issued. A3E completed the report in a timely manner that allowed the project to move forward within the IDOT construction timeline.
Client: Weston Solutions
Location: Vandalia, Illinois
Key Staff: Dave McCoy, Evan Meinzer, Sarah Clark
Duration: 1 Month
Value: Undisclosed
See More PSI Work
For more examples of our IDOT corridor work, see our 2025 IDOT PSI programs across Chicagoland and our IDOT PSI on McConnor Parkway in Schaumburg.
Frequently Asked Questions
What was the Vandalia Yard PSI?
A Preliminary Site Investigation A3E performed for IDOT (via Weston Solutions) at the Vandalia Maintenance Yard 712, advancing nine soil borings to 8 feet to evaluate subsurface contamination ahead of a new maintenance building under PTB-179.
What is the difference between a PESA and a PSI?
A PESA is the records-and-reconnaissance first step, like a Phase 1 ESA. A PSI is the subsurface sampling follow-up, like a Phase 2 ESA, performed where the assessment flags a concern — exactly the progression that happened at Vandalia.
Why compare soil results to CCDD MAC values?
Comparing contaminants of concern to CCDD Maximum Allowable Concentration values determines whether excavated soil can go to a lower-cost clean fill facility — a key driver of disposal budgeting on IDOT corridor projects.
Need a PSI for Your IDOT or Corridor Project?
A3 Environmental Consultants delivers defensible, schedule-driven Preliminary Site Investigations for IDOT and municipal projects across the Midwest. Learn more about our Preliminary Site Investigation services, or call (888) 405-1742.
We Fix Gnarly Environmental Problems
Reviewed by the A3 Environmental Consultants team, headquartered in Chicago, Illinois, under the supervision of a licensed Professional Geologist (P.G.).
