A Phase I environmental site assessment is a records-and-site-visit review that looks for signs of contamination on a property before it is bought. It does not take soil or water samples. In the United States it is usually done to the ASTM E1527-21 standard, which the U.S. Environmental Protection Agency recognizes as meeting the federal "all appropriate inquiries" rule that buyers need to claim certain liability protections.
Why a Phase I exists
Federal Superfund law can make a property owner responsible for cleanup based on ownership alone. EPA describes this as strict liability: liability for contamination may be assigned solely because someone owns the property. Congress added protections in 2002 for buyers who did not cause the contamination and who looked first. EPA lists three: innocent landowners, contiguous property owners and bona fide prospective purchasers.
To claim any of them, a buyer has to show it made all appropriate inquiries into the property's present and past uses. The Phase I is how that inquiry is documented. EPA's AAI rule, 40 CFR Part 312, took effect on November 1, 2006. EPA states that ASTM E1527-21 and E2247-23 can be used to satisfy it. E2247-23 is the version for forestland or rural property.
Who needs one
EPA says the AAI requirements apply to commercial and government entities buying property, and to all individuals buying property for non-residential use, who may later seek protection from federal cleanup liability. In practice that covers most investor, developer and commercial land purchases. A buyer planning homes, a retail pad or an industrial lot should treat the Phase I as part of due diligence, ahead of the closing date and not after it. A seller can speed things up by already having a current report.
What a Phase I covers
According to EPA, AAI requires interviews with current and past owners, operators and occupants, a review of government records, a visual inspection of the property, and searches for environmental cleanup liens. A published description from a land brokerage lists the typical work this way:
- A site visit by an environmental professional.
- A review of federal, state, local and tribal databases, including those for aboveground and underground storage tanks.
- Historical records such as fire insurance maps, city directories, aerial photographs and topographic maps.
- Interviews with current and past owners and occupants.
- A review of title and judicial records for environmental liens.
The report must also record data gaps. EPA's guidance says the report should document and discuss significant data gaps that affect the professional's ability to identify conditions indicating a release. It must include the professional's opinion on whether further investigation is warranted, if the professional has one. Under E1527-21 it closes with a statement that either finds no recognized environmental conditions or lists the ones found.
A Phase I does not usually cover items outside the standard's scope. EPA's guidance gives examples of optional add-on services: lead-based paint, mold, radon, asbestos, regulatory compliance and indoor air quality.
What you receive
EPA's guidance says the report carries the signature and qualifications of the environmental professional who prepared it. Appendices typically hold the regulatory records documentation, the environmental database report, a site map, vicinity maps and site photographs. They also hold the historical source documents, such as building department records, chain of title documents, tax records, zoning records, aerial photos, fire insurance maps and USGS topographic maps, plus the interview records. Read the conclusions section first, then the data gaps section, then the list of recognized environmental conditions.
How long it stays valid
EPA's rule sets two clocks. AAI must be conducted or updated within one year before the date of acquisition. Certain pieces must be conducted or updated within 180 days before the buyer takes ownership: the interviews, the government records review, the site inspection and the lien searches. If your closing slips, parts of the report may need to be refreshed. Ask your consultant which dates control.
How long it takes
A land brokerage's published guide puts a Phase I at about two to four weeks in total. It says site work on a property with little development history can take about two weeks, and report review often takes several more. Delays come from records access and from the consultant's schedule. Build the time into your contract's due diligence period.
What it costs
Published ranges vary, and none are Arizona-specific. The same brokerage guide says a Phase I generally runs $1,000 to $2,500. Acreage, location, site history and neighboring uses all move the number. Ask for a fixed quote that states the scope, the standard (E1527-21 or E2247-23), and who will be allowed to rely on the report.
When a Phase I leads to a Phase II
A Phase II is the sampling step. The brokerage guide says it is called for once contamination is discovered or there is evidence of possible contamination. Licensed engineers or geologists collect soil or water samples and test for hazardous substances or petroleum products. The same guide gives Phase II costs from $5,000 to over $200,000 and says the work can take a few weeks to several months. A Phase II is a decision point: price the cleanup, renegotiate, or walk away.
Arizona specifics
Two Arizona programs are worth checking alongside the Phase I database search.
- The WQARF Registry. Under A.R.S. 49-287.01, the Arizona Department of Environmental Quality keeps a registry of scored sites with a short description, a score and a status of investigation and cleanup. A listing does not by itself mean the site poses a threat to health or the environment. Sites that no longer need action come off the registry and go on a separate public list.
- Deed restrictions after cleanup. Under A.R.S. 49-152, if an owner cleans a site using engineering or institutional controls or leaves contamination above the residential standard, a declaration of environmental use restriction must be recorded in each county where the property sits. The department keeps a public list of remediated sites. The declaration runs with the land, so a buyer takes it along.
A reliable Phase I will search these. If a parcel next door appears on a registry or a restriction is recorded, ask the consultant how it affects your site.
Questions to ask before you order
- Which standard will the report follow, and does the consultant state that it meets EPA's AAI rule?
- Who is the named environmental professional, and what are the qualifications on the report?
- Which parties may rely on the report, and for how long?
- What is in the fixed price, and what is billed extra?
- Which dates start the 180-day clock, and how do they line up with the closing date?
Reading the results
A clean report supports the purchase. A report with recognized environmental conditions is not a verdict. It tells you what to price, test or avoid. Pair it with a title review and a survey. Our raw land due diligence checklist for Arizona shows where the Phase I fits, and the land entitlement process shows why environmental findings affect approvals and timing.
This is general information, not legal advice. Environmental liability rules are technical, and an Arizona attorney and a qualified environmental professional have the final word.
Selling land that needs this work
If you own land with an uncertain history, buyers will ask for a Phase I and sometimes a Phase II. Red Dirt Property buys land as-is across all 15 Arizona counties, underwrites parcels against its own statewide parcel data, and handles entitlement after closing. There is no agent commission on our purchases. To discuss a parcel, start here.