Looking for a Phase I ESA in Portola Valley, CA? Describe your project once and up to three environmental consultants who work in Portola Valley and San Mateo County get back to you with a quote. It's free and there is no obligation.
Portola Valley is home to about 4,282 people (2024 Census Bureau estimate), a shrinking community (−3.9% since 2020). With 471 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.
Portola Valley at a glance
- Population (Census Bureau estimate, 2024)
- 4,282 (−3.9% since 2020)
- Rank in California
- 435th of 482 cities and towns
- Land area
- 9.1 sq mi
- Population density
- 471 people per sq mi (semi-rural)
- Type
- Town (Portola Valley town)
- Main county
- San Mateo County
What to check before hiring in Portola Valley
- 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 Portola Valley
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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 Portola Valley
How much does a Phase I ESA cost in Portola Valley, CA?
It depends on the size and history of the property and the turnaround. Describe the property: consultants who serve Portola Valley 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 Portola Valley 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.