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What is the process of a Preliminary Site Investigation (PSI)?



A Preliminary Site Investigation (PSI) is the second step in the process of corridor due diligence. We need a finished Preliminary Environmental Site Assessment (PESA) to start the PSI process.



We send a team to the appropriate locations identified in the PESA to take samples for further analysis. We use this process to confirm or deny, and then quantify how high levels of contamination are along the corridor.



We send our samples to a laboratory to have exact environmental analysis done on the property. These results inform all the other advice we'll have regarding the corridor.

PSI Report


Using laboratory analysis, we write a report regarding the corridor. This report is the tool necessary to manage impacted and non-impacted soil for disposal without spreading contamination. We help you save money on disposal with Clean Construction Demolition Debris (CCDD) services.

Frequently Asked Questions About Preliminary Site Investigations (PSI)

A Preliminary Site Investigation (PSI) is the exact same as a Phase 2 ESA only instead of the investigation being done on a particular commercial property, it’s performed inside a corridor of Rights of Way (ROW). Essentially it’s a long and narrow Phase 2 ESA which seeks to confirm or deny the existence of environmental contamination along the corridor which is being assessed. If you're with a financial lending institution looking for a Preliminary ESA, you are most likely looking for a Transaction Screen Assessment (TSA) which can be found by clicking through the link. They are frequently mistaken for PSI.

Before we get too deep, you should check out this post describing a Phase 2 Environmental Site Assessment. It will give you a good base of understanding about PSI.

Who Needs a Preliminary Site Investigation?

First of all, nobody needs a PSI unless the Preliminary Environmental Site Assessment (PESA) shows areas of concern. The PESA is the first step in the process, just like a Phase 1 ESA is the first step in commercial due diligence.

Governments; State Departments of Transportation, Counties and Municipalities typically purchase PESA and subsequently PSI. Governments who are putting in infrastructure like roads and water mains need to understand the environmental conditions around the area they will be working. These road and pipeline projects are linear in nature and cross the Rights of Way of many other landowners.

A road widening along a state highway which passes several dry cleaners, gas stations and industrial parks may all have contaminated soil. A PSI would confirm or deny the existence of contamination.

Why Do Governments Purchase Preliminary Site Investigation?

Governments are interested in the contamination along the corridor for several reasons.

  • They are concerned with contamination for worker exposure. Construction workers potentially exposed to contamination is a health and safety risk and precautions may be required for the workers.
  • They need to budget for the project. Contaminated soil is expensive to haul off-site, Clean Construction Demolition Debris (CCDD) soil is less expensive to haul off but must be clean. Soil can be reused on-site but must be clean, so there could be costs associated with bringing in backfill.
  • Contamination travels along infrastructure such as pipelines. Putting a pipeline through a contaminated area is almost certainly going to transmit the contamination along the pipe, spreading it to adjacent properties.

How Long Does It Take to Do a Preliminary Site Investigation?

The time to do a PSI is dependent on the area covered. Generally there are only small areas of concern along the corridor. If the area is relatively small, expect it to take the same amount of time as a Phase 2 ESA, about 15 to 30 days.

What Does a Preliminary Site Investigation Cost?

Again, this depends on the size of the corridor which is being studied but figure about $6000 to start.

How Long is a Preliminary Site Investigation Good For?

A PSI is typically used once and done. They are used for budgetary purposes and in preparation of work being done in the Right of Way.

Who Performs a Preliminary Site Investigation?

The majority of PSI are completed by environmental consultants. Municipalities typically don't complete them internally. A3 Environmental Consultants does PSI in Illinois, Southern Wisconsin, North West Indiana and Western Michigan. We are headquartered in Chicago Illinois.

What Else Do I Need To Know about Preliminary Site Investigation?

  • In the State of Illinois, the Department of Transportation subs the PESA process out to the Illinois State Geological Survey.
  • If you are having a PSI performed as a government, the work is public record and can be subject to FOIA.
  • Municipalities need permits to drill in state rights of way, the state needs permits to drill in municipality rights of way. Utilities need permits to drill in anyone's right of way.
  • If you'd like to see a sample Preliminary Site Investigation click through the link.

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The A3 Environmental Team completed both a Phase 1 and a Phase 2 for our property and Patrick and I couldn't be more pleased with the work they did!

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I thoroughly enjoyed working with A3E on our Phase 1 studies. We were running up against some deadlines, and they jumped through hoops to get everything completed on time.

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The A3E team did a great job on our Phase 1 report. They were quick , thorough and professional. They were able to give me all of the information that I needed.

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