An Environmental Assessment Before Buying Land is one of the most critical steps in protecting your investment — especially if the property has current or historical underground storage tanks (USTs). Buying land may look simple on the surface. The plat shows a clean boundary, the lot may appear wooded or open, and it is easy to imagine a future home, shop, or commercial building. But if that property has, or once had, petroleum tanks or industrial chemical storage, there can be decades of environmental history sitting just below grade.

An Environmental Assessment Before Buying Land is one of the most important due diligence steps you can take before you commit to a purchase contract, especially in regions like South Carolina where historic fuel stations, repair shops, and agricultural fueling sites are common. Proper environmental due diligence helps you understand contamination risk, groundwater limitations, remediation requirements, and how all of that will affect your site development budget and schedule.

This article walks through the phases of environmental assessment, how to recognize signs of contamination, the main remediation strategies, and how these issues tie directly into pre-site development planning.

Why Underground Storage Tanks Are a Hidden but Common Risk

Underground storage tanks are used to store gasoline, diesel, heating oil, waste oil, and various industrial chemicals. The U.S. Environmental Protection Agency (EPA) estimates that hundreds of thousands of active USTs are in use nationwide, with a long history of leaks and releases that can impact both soil and groundwater.

Common places where USTs are found include:

  • Former and existing gas stations and convenience stores
  • Auto repair and fleet maintenance facilities
  • Agricultural bulk fuel locations
  • Industrial and manufacturing properties
  • Older commercial parcels along busy roads or intersections
  • Properties with historic heating oil or kerosene tanks

In South Carolina, USTs are overseen by the state’s underground storage tank program within the Department of Environmental Services (DES), which regulates planning, installation, compliance, and cleanup of UST systems. Many release sites and active remediation projects are listed in public databases, which makes them searchable during environmental due diligence.

You can learn more about the federal UST framework and state programs here:

Environmental Assessment Before Buying Land: The Role of Due Diligence

An Environmental Assessment Before Buying Land is not just a formal report for a lender. It is structured environmental due diligence that helps you answer three core questions:

  1. Is the property contaminated, or likely to be contaminated?
  2. How will contamination affect wells, site development, and permitting?
  3. What will it cost, in time and money, to manage or clean up the problem?

Environmental due diligence for UST sites is typically organized into phases: Phase I (records and reconnaissance), Phase II (subsurface sampling), and Phase III (remediation and corrective action). Each phase builds on the last and feeds directly into your development strategy.

Phase I Environmental Site Assessment: Identifying Recognized Environmental Conditions

A Phase I Environmental Site Assessment (ESA) is usually the first formal step in an Environmental Assessment Before Buying Land. It is a paper- and field-based evaluation that looks for “Recognized Environmental Conditions” (RECs) that might indicate potential contamination.

A typical Phase I ESA includes:

  • Review of aerial photos, fire insurance maps, and historical land use records
  • Search of federal and state environmental databases, including UST and release lists
  • Site reconnaissance (walking the property, noting stains, vents, fill ports, monitoring wells)
  • Interviews with owners, operators, and local officials when available

Phase I does not include drilling or sampling. Its purpose is to determine whether environmental risk exists and whether further investigation (Phase II) is warranted. Many lenders and investors treat a Phase I ESA as a standard requirement before financing land or commercial real estate.

ASTM has a widely accepted Phase I ESA standard that defines the scope of work and “all appropriate inquiry” for buyers:
ASTM E1527 Phase I ESA Standard

Phase II Environmental Testing: Confirming and Characterizing Contamination

If the Phase I ESA identifies RECs such as documented USTs, historical gas stations, or signs of chemical use, the next step is Phase II Environmental Testing. This phase moves from paper review to subsurface data collection.

A Phase II assessment may include:

  • Soil borings and collection of soil samples at various depths
  • Installation of groundwater monitoring wells
  • Sampling and analysis of groundwater
  • Soil vapor sampling if vapor intrusion is a concern

Laboratory analysis looks for:

  • Petroleum hydrocarbons (gasoline, diesel, heating oil, and their breakdown products)
  • LNAPL (light non-aqueous phase liquid) that floats on groundwater, such as gasoline and diesel
  • DNAPL (dense non-aqueous phase liquid) that sinks through groundwater, often associated with chlorinated solvents
  • Chlorinated solvents and degreasers historically used at dry cleaners or industrial sites

The Phase II ESA answers key questions for your project: is there contamination, how much is there, where is it located, and how does it compare to state cleanup standards?

Phase III (Corrective Action): Environmental Remediation Strategies

When contamination is confirmed, the next phase is corrective action or remediation — essentially the “Phase III” in the environmental due diligence process. The goal is to manage or remove contaminants to a level that satisfies state risk standards and allows the property to be used safely.

Common remediation strategies on UST-impacted sites include:

Excavation and Off-Site Disposal

Excavation is often the most straightforward approach, especially when the contamination is relatively shallow and localized. Impacted soil is dug up, loaded into trucks, and transported to a properly permitted disposal or treatment facility.

If your site development plan already includes significant excavation for foundations, basements, utilities, or stormwater systems, it may be possible to coordinate the remediation excavation with your planned earthwork. This can provide efficiencies, but it must be done under an approved remediation plan, with proper sampling, manifesting, and documentation.

Aggressive Fluid and Vapor Recovery (AFR / AFVR)

Aggressive Fluid and Vapor Recovery (often called AFR or AFVR) is a dual-phase extraction technique that uses vacuum systems to pull out free product (LNAPL), contaminated groundwater, and petroleum vapors from wells. A vacuum truck or skid-mounted system connects to monitoring or recovery wells and removes multiple phases of contamination at once.

AFR is particularly useful where free product is present and excavation is impractical or would be too disruptive to existing structures or utilities. It can also be deployed repeatedly over time as part of a long-term remediation strategy.

You can find a general overview of aggressive fluid and vapor recovery here:
Aggressive Fluid Vapor Recovery (AFVR) Overview

Monitored Natural Attenuation (MNA)

Monitored Natural Attenuation (MNA) relies on natural physical, chemical, and biological processes in the subsurface — such as biodegradation, dispersion, and dilution — to gradually reduce contaminant concentrations over time. It is often used where:

  • Contaminant levels are low to moderate
  • Plumes are stable or shrinking
  • Exposure pathways can be controlled

MNA typically involves:

  • Removal or control of the original source (e.g., tank removal)
  • Installation of monitoring wells
  • Long-term sampling to document natural cleanup progress

From a developer’s perspective, MNA is usually the slowest option because the site may require years of monitoring before being fully closed out. However, it can be cost-effective where excavation or aggressive treatment is not necessary.

Technical background on MNA is available through EPA and remediation technology resources such as:
Monitored Natural Attenuation Technology Overview

Chemical Injection and In-Situ Chemical Oxidation (ISCO)

Another remediation strategy is in-situ chemical oxidation (ISCO), where oxidizing agents are injected into the subsurface to break down contaminants in place. Commonly used oxidants include:

  • Sodium or potassium permanganate
  • Sodium or potassium persulfate
  • Hydrogen peroxide or percarbonate-based systems
  • Ozone in certain designs

Injection wells or direct-push points are installed so the oxidants can contact contaminated zones. In some designs, these chemical reactions help break down or partially stabilize contaminants, making it easier to recover them using AFR or similar extraction systems.

For more information on in-situ chemical oxidation for petroleum hydrocarbons, see:
In Situ Chemical Oxidation – Technology Overview

How Risk-Based Corrective Action (RBCA) Affects Cleanup Levels

Many states, including South Carolina, apply some form of risk-based corrective action (RBCA) to petroleum UST sites. Instead of requiring every site to be cleaned up to the same numeric standard, RBCA looks at:

  • Type and concentration of contaminants
  • Exposure pathways (drinking water wells, vapor intrusion, surface water)
  • Land use (residential vs. commercial/industrial)
  • Proximity to sensitive receptors (schools, wells, wetlands)

Under RBCA, some sites may be cleaned up to very stringent standards, while others may be managed with engineering controls, institutional controls, or long-term monitoring. EPA’s guidance on risk-based decision-making for USTs provides a helpful overview:
EPA Risk-Based Decision Making for USTs

Who Is Responsible for Cleanup? The Role of the “Responsible Party”

A common concern for buyers is whether purchasing a contaminated property automatically makes them responsible for cleanup. In most UST programs, the state designates a Responsible Party (RP) — usually the tank owner, operator, or a previous owner tied to the release.

As a buyer, you may not automatically inherit the legal responsibility for a historic release. However, if you plan to develop the site or change its use, you will likely need to coordinate with DES and the RP to:

  • Understand the status of the existing corrective action plan
  • Determine whether your construction plans conflict with ongoing remediation
  • Explore options to accelerate cleanup or integrate remediation with site development

In some cases, a buyer and DES can work together to modify the corrective action approach — for example, shifting from long-term MNA to more active excavation and AFR if the buyer wants to develop the property sooner. The key is to understand the status of the site before you close.

Clues That a Property May Be Contaminated: Monitoring Wells and Historic Use

When you walk a property, there are several visual clues that should immediately trigger the thought of an Environmental Assessment Before Buying Land:

  • Monitoring wells: Small PVC pipes with lockable caps, often at or near grade, arrayed in lines or grids.
  • Vent pipes or fill ports: Especially near driveways or old pump islands.
  • Stained soil or pavement: Dark spots or areas of stressed vegetation.
  • Location along busy roads: Sites at major intersections, former service stations, or historically commercial corners.

The presence of monitoring wells is a strong sign that the property is already in a state database as a release site. That does not mean you cannot buy or develop it, but it does mean you should review the case file and understand the current risk status before moving forward.

Wells and Groundwater: Why You Cannot Simply Drill a Well on a Contaminated Property

Groundwater is often the most sensitive exposure pathway at UST sites. When contamination affects groundwater, several restrictions usually follow:

  • New potable wells are typically prohibited until cleanup meets state standards.
  • Deed restrictions or environmental covenants may forbid groundwater use.
  • After remediation, additional testing is required before any well is approved.

This is especially important in rural parts of South Carolina, where many properties rely on private wells instead of municipal water. You cannot assume a future well will be allowed on a parcel that shows historic contamination or an active corrective action case.

An Environmental Assessment Before Buying Land will identify these limitations early, so you do not design a home or commercial project around groundwater that cannot legally be used.

It Is Not Uncommon to Discover Tanks During Excavation

Even with good due diligence, it is still possible to discover undocumented tanks during site work. This is particularly common on:

  • Lots fronting busy highways or historic commercial corridors
  • Older residential properties that used heating oil or farm fuel
  • Sites that have changed use multiple times over decades

Discovering a tank mid-excavation is disruptive. Work must stop, appropriate notifications must be made, and DES will likely require an assessment of whether the tank leaked. Soil samples may need to be collected right away, and your excavation plan may change, especially if contamination is present.

This is yet another reason to complete an Environmental Assessment Before Buying Land, particularly when you are dealing with a site along a busy road or with a history of commercial use. While you cannot prevent every surprise, you can reduce the odds significantly.

DES Involvement and How It Affects Site Development

Once a release is reported, DES typically:

  • Opens a case file
  • Identifies the Responsible Party
  • Requires a site characterization and corrective action plan
  • Reviews monitoring data and progress reports over time

From a developer’s standpoint, this means you are coordinating with another governing agency in addition to building departments and zoning officials. The process can be slow. Plans must be submitted, reviewed, and revised. Field work must be documented. Monitoring can continue for years, even as the site is in use.

None of this prevents development outright, but it does influence design and scheduling. For example:

  • Foundations may need to avoid areas of remaining contamination.
  • Utility trenching must consider contaminated soils and disposal requirements.
  • Vapor barriers or sub-slab ventilation systems may be requested for buildings over affected areas.

Good coordination between your environmental consultant, DES, and your site contractor can allow remediation and development to move forward together, rather than in conflict.

Integrating Remediation with Site Work

One advantage of tackling Environmental Assessment Before Buying Land is that you can design your site development plan with remediation in mind. If you already know that:

  • Portions of the site will require excavation for footings or basements
  • Retaining walls or cuts will expose contaminated soils
  • Stormwater systems will intersect former tank areas

then you can work with your environmental team to:

  • Excavate contaminated soil while you are already mobilized
  • Stage and dispose of material properly with minimal re-handling
  • Sequence AFR or injection events around your construction schedule

This integrated approach can reduce both cost and downtime compared to treating remediation and construction as two completely separate projects.

Why Many Sites Have Been Contaminated for Decades

In the South Carolina region and across the Southeast, it is common to find UST sites that have been in some stage of assessment or remediation for 30 or 40 years. Reasons include:

  • Older steel tanks that leaked before modern monitoring requirements
  • Limited early detection, allowing plumes to grow
  • Focus on higher-risk sites first, leaving low-risk sites on long-term monitoring
  • Budget and funding challenges for more aggressive cleanup

While technology for AFR, injection, and thermal remediation has improved, the fact remains that complex plumes in heterogeneous soils and fractured rock can be slow and difficult to fully remediate. For buyers, the key is to understand the current status of a site, the trend of contaminant concentrations, and the likely remaining timeline before regulatory closure.

How an Environmental Assessment Before Buying Land Protects You

When you are evaluating a lot that may have underground storage tanks, an Environmental Assessment Before Buying Land gives you:

  • A clear picture of historic and current land uses
  • Knowledge of any existing DES release cases or monitoring networks
  • Data on soil and groundwater quality from Phase II testing
  • An understanding of which remediation strategies are in play or could be used
  • Insight into groundwater restrictions and well feasibility
  • Leverage in negotiations and contract contingencies

Without that information, you risk discovering tanks mid-excavation, being surprised by monitoring wells, or learning too late that a potable well cannot be permitted due to existing contamination.

Putting It All Together: Environmental Due Diligence and Site Development

For any parcel with current or historic underground storage tanks, environmental and site planning should be treated as a single, integrated process. Environmental conditions directly impact excavation strategy, grading plans, drainage layout, and foundation design.

If remediation is required, it must be coordinated with professional site services including clearing, grading, excavation, and utility installation. Treating environmental assessment and construction as separate steps often leads to delays, change orders, and regulatory conflicts.

  1. Start with an Environmental Assessment Before Buying Land (Phase I ESA).
  2. Follow with Phase II sampling if RECs are identified.
  3. Understand any existing corrective action plans or DES requirements.
  4. Work with your environmental consultant to select appropriate remediation methods (excavation, AFR, MNA, injections, or a combination).
  5. Coordinate remediation with grading, foundation, utility, and drainage plans.
  6. Confirm groundwater restrictions and the feasibility of wells before designing around them.

If you are still in the planning phase, reviewing our pre-construction planning process can help you understand how due diligence fits into budgeting and contract preparation.

Call to Action: Turning Assessment into a Buildable Site

If you are evaluating property with potential underground storage tanks, do not skip an Environmental Assessment Before Buying Land. Environmental due diligence protects your development timeline, financing, and long-term property value.

Our team specializes in site development services in Columbia, South Carolina, including excavation, grading, drainage systems, and coordination with environmental consultants when remediation is required.

If you are considering purchasing land and want clarity on how environmental conditions could impact your build, contact us here to discuss your project before closing.