Contributed by Jordan Harper, Environmental Specialist, PPM Consultants
If you have ever driven through an older part of town with a long-time resident, you have likely heard some version of: “That used to be…” followed by a story about a former gas station, warehouse, or neighborhood business. These recollections can offer useful context and a sense of local history, but when it comes to commercial property transactions, stories alone are not enough.
Environmental due diligence requires documented, defensible research. As part of a Phase I Environmental Site Assessment (ESA), environmental professionals follow ASTM Standard E1527-21 to evaluate historical uses of a property and identify potential environmental risks. This process supports informed decision-making and helps property owners qualify for landowner liability protections under CERCLA.
One of the most effective tools available to support this work is the fire insurance map.
Fire insurance maps (most commonly produced by the Sanborn Map Company) were originally developed in the late 1800s to help insurers evaluate fire risk in urban areas. This was especially valuable in a time when wooden structures, limited building codes, and delayed fire response could result in widespread destruction.
Today, these maps serve a different but equally important role: providing a detailed historical record of property use and development.
Across more than 12,000 cities and towns, fire insurance maps offer a consistent, property-level view of historical conditions spanning decades. For environmental professionals, they remain one of the most reliable resources for identifying legacy site uses that may still influence environmental conditions.
Fire insurance maps provide a level of detail that allows trained reviewers to reconstruct how a site functioned, not just what occupied it.
Key observations include:
- Building construction and layout: footprint, height, room configuration, and materials
- Specific site uses: residential, commercial, or industrial designations, with labels such as “machine shop”, “auto repair”, “general store”, or “cleaners”
- Industrial features: boiler rooms, oil storage areas, compressors, and process-related spaces
- Transportation features: rail lines, loading docks, and access points
- Changes over time: additions, demolitions, address changes, and evolving site configurations
To the untrained eye, these maps can appear complex. However, several key elements make them easier to interpret:
- Color coding indicates construction materials (e.g., yellow for wood-frame, pink for brick)
- Labels and abbreviations identify occupancy and use
- Symbols denote features such as storage tanks, fuel pumps, and fire protection systems
- Street names and property boundaries allow correlation with current site conditions
For environmental professionals, understanding these details is critical to identifying potential environmental concerns.
Certain features consistently represent elevated environmental risk and deserve close attention during review.
Gas Tanks and Filling Stations
Fuel-related operations are among the most common environmental concerns identified during a Phase I ESA. Fire insurance maps frequently depict:
- Storage tanks: often labeled or shown as circles with abbreviations such as “GT”
- Filling stations: commonly positioned along major roadways with angled layouts or canopy structures
- Automotive service areas: labeled with terms such as “lube” or “repair”
Even when no evidence exists today, the historical presence of these features may indicate the potential for petroleum impacts to soil or groundwater.
Pressing Clubs and Dry Cleaners
Facilities labeled as “pressing clubs,” “cleaners,” “Chinese laundry,” or “dye works” are also significant findings.
These operations historically used chlorinated solvents such as tetrachloroethylene (PCE), which are persistent in the environment and can migrate through soil and groundwater.
Even a nearby dry cleaner shown on a historical map can elevate environmental risk and warrant further evaluation.
Application in the Phase I ESA Process
Under ASTM E1527-21, identifying Recognized Environmental Conditions (RECs) depends heavily on understanding historical site use. Fire insurance maps often reveal higher-risk uses that are not apparent based on current conditions.
Examples include:
- A modern retail building located on the footprint of a former filling station
- An office building that once housed light industrial operations
- A paved lot covering the former location of a petroleum bulk storage plant
- A shopping center that previously included a dry-cleaning tenant
These findings help environmental professionals identify potential sources of contamination and determine whether additional investigation is warranted.
While fire insurance maps are highly valuable, they are most effective when used alongside other historical resources. At PPM, Phase I ESAs incorporate a layered research approach to provide a thorough and defensible evaluation.
Key supporting resources include:
- Aerial photographs: Provide a visual timeline of site development, confirm building presence, and help identify features such as tanks, structures, and site layout during specific time periods
- City directories: Identify historical occupants and business operations at a given address; listings such as “auto repair” or “cleaners” can corroborate map findings
- Topographic maps: Offer insight into land use patterns, drainage features, and natural conditions that influence potential contaminant migration
- Property records: Establish ownership and transaction history, helping to frame site use over time
- Site reconnaissance: Evaluate current conditions, identify remaining infrastructure, and observe potential evidence of releases
- Interviews: Provide additional context, clarify incomplete records, and identify undocumented site uses or historical practices
By integrating these resources, PPM develops a comprehensive and defensible understanding of site history. By identifying past uses such as filling stations, dry cleaners, or industrial operations, fire insurance maps help position properties for successful reuse.
At PPM, our team integrates multiple historical data sources, applies ASTM-compliant methodology, and draws on industry experience to identify potential environmental concerns.
This approach allows us to:
- Deliver clear, defensible Phase I ESA reports
- Identify risks early in the transaction process
- Support Brownfield redevelopment initiatives
- Provide practical, project-specific recommendations
Interpreting historical data requires more than simply locating a map, it requires understanding what to look for and how individual features relate to environmental risk.
Moving Beyond “What Used to Be There”
Local stories can provide a starting point, but environmental liability decisions depend on documented evidence. Fire insurance maps offer a reliable and detailed record of past site uses, often uncovering risks that are not visible today.
By combining these maps with other historical resources and applying a structured approach under ASTM E1527-21, PPM helps clients move from uncertainty to informed decision-making.
Understanding what used to be there is not just about history, it is about protecting investments, managing risk, and supporting responsible development.
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