Looking for a Phase I ESA in Oak Brook, IL? Describe your project once and up to three environmental consultants who work in Oak Brook and DuPage County get back to you with a quote. It's free and there is no obligation.
Oak Brook is home to about 8,188 people (2024 Census Bureau estimate), a stable community (+0.4% since 2020). With 1,027 people per sq mi, it is a semi-rural area. Commercial sales and loans here routinely require a Phase I, especially for former industrial, gas station and dry cleaning sites.
Oak Brook at a glance
- Population (Census Bureau estimate, 2024)
- 8,188 (+0.4% since 2020)
- Rank in Illinois
- 257th of 1,294 cities and towns
- Land area
- 8.0 sq mi
- Population density
- 1,027 people per sq mi (semi-rural)
- Type
- Village (Oak Brook village)
- Main county
- DuPage County
What to check before hiring in Oak Brook
- Qualifications: the report is signed by an Environmental Professional under the EPA All Appropriate Inquiries rule; some states also license environmental consultants.
- Lender requirements: check whether your lender has its own scope or reliance letter requirements.
- Timing: order early: records requests and the site visit take time.
- Price drivers: property size and history, number of buildings and turnaround.
Useful official resources
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EPA: brownfields
All Appropriate Inquiries and brownfields programs.
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ASTM International
Publisher of the E1527 standard.
Services available in Oak Brook
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Phase I Environmental Site Assessment
Records review, site visit and interviews to ASTM E1527 by an Environmental Professional, for a purchase or a loan.
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Phase II Environmental Site Assessment
Soil, groundwater or vapor sampling when a Phase I identifies a recognized environmental condition.
Frequently asked questions in Oak Brook
How much does a Phase I ESA cost in Oak Brook, IL?
It depends on the size and history of the property and the turnaround. Describe the property: consultants who serve Oak Brook send a proposal.
How long does it take?
Often two to three weeks; rush service is usually available.
What if the Phase I finds something?
A Phase II may be recommended to sample soil or groundwater and assess the extent.
Which environmental consultants will contact me?
Up to three independent environmental consultants who serve Oak Brook and the surrounding area, chosen for the service you need. Your details are shared only with your consent.
Source: U.S. Census Bureau, Population Estimates Program (Vintage 2024) and Gazetteer Files (public domain), imported on 10/31/2026. Figures describe the incorporated place or county as published; they are shown for information only.