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INVESTIGATING POTENTIAL PETROLEUM IMPACTED SITES

There is an estimated 450,000 Brownfields properties in the country. Approximately half of these properties are anticipated to be impacted by petroleum underground storage tank releases. Twenty-five percent of the annual funding from the Brownfields Law is aimed to reclaim petroleum-impacted properties. These sites are potential liabilities, but they also hold some of the most promising economic opportunities for redevelopment largely because of their highly marketable locations. There are constraints including the petroleum exclusion from Superfund, public funding resources, negotiating regulatory controls, and physical considerations. However, redeveloping these sites can make sense when connecting environmental innovation and economic feasibility.

Diligent inquiry into most property transactions is necessary to identify potential petroleum related and other environmental liabilities. Conducting a Phase I Environmental Site Assessment (ASTM E1527-00) or desk-top records review is a starting point to evaluate for recognized environmental conditions such as the presence of a former petroleum underground storage tank on a property and its formal agency status regarding operation and closure, if applicable. Sources of information include interviews, historic aerial photographs, city directories, fire insurance maps, and state and local records. Depending on the available information, the presence or historical presence of a petroleum storage tank and associated equipment may suggest further investigation is warranted to answer whether a tank is still located on site and whether a release has in fact occurred.

A Phase II Environmental Site Investigation is conducted to collect the additional information required to complete a property transaction evaluation; however, it is not typically conducted for the purpose of formal tank and/or release closure with the managing state agency, which would be potentially completed later if a tank and/or associated release were identified during the investigation. The investigation may follow many of the state’s protocols for investigating releases such as analytical parameter sets, sample locations, etc. so that the investigation data may be incorporated later, if necessary, more easily into a formal submittal to the state. However, data gaps in formal agency reporting are inherent in a due diligence investigation, which are primarily designed to control cost while evaluating whether there are liabilities and the magnitude of the liabilities identified.

At properties where the presence of a tank is suspected but has not been confirmed through available lines of evidence, a geophysical survey may be used to evaluate non-intrusively the potential presence or absence of a tank in accessible areas of the property. The geophysical survey is typically conducted using ground penetrating radar (GPR) and/or electromagnetic (EM) techniques depending on the geology and other potential inferences. An experienced geophysical surveyor will evaluate anomalies based on technique response, size, location, and personal experience with the equipment and geologic setting. Positive results should be confirmed through an intrusive check such as with exploratory trenches using a track-hoe. The positive identification of an abandoned tank may be a stopping point for the transaction evaluation and the start of formal closure investigation, removal and reporting.

Ultimately, the geophysical survey and Phase I ESA will help to identify where an intrusive investigation should be focused on site to confirm the presence or absence of a potential petroleum release. Depending upon the results of the geophysical survey and Phase I ESA, the intrusive investigation may be conducted to assess an identified tank area, or if a tank was not identified, to evaluate the site for widespread impacts.

The key components of this type of intrusive investigation are boring locations, boring advancement, sample collection and analysis, and data evaluation. The selection of boring locations goes back to the geophysical survey and Phase I ESA. Depending on whether evidence of a tank was identified in a specific location, two borings hydraulically downgradient and one boring hydraulically upgradient advanced to uppermost groundwater usually is sufficient if a tank is present. A fourth boring through the center of a confirmed empty tank pit may also be advanced. Additional borings may be advanced around dispenser locations and along pipe runs. Otherwise if no potential tank locations are known, four or more borings may be distributed across the site depending upon its size and accessibility.

Boring advancement in this investigation scenario is most commonly conducted using the direct push method, using equipment such as a Geoprobe ® Model 5400 or 6600 in various mounting configurations such as on tracks, pickup trucks, and hand carts. Other methods used, depending on hydrogeologic setting, include hollow stem auger and sonic drilling. However, these methods are typically more expensive and can take longer than direct push methods if they don’t have to be used. Other advantages of the direct push method include minimal soil cuttings, smaller boring diameter, reduced decontamination effort and potential cross contamination, and ability to access a wide variety of exterior and interior locations. Attention to state drilling requirements such as permitting and driller certification should be incorporated into the investigation planning stage.

Evaluation and documentation of the boring advancement is an important aspect of the investigation. Using the direct push method, soil cores can be collected continuously in up to 5-foot intervals. Soil core screening for potential impacts involves measuring ionizable organic compound headspace response with a photo- or flame-ionization detector usually calibrated for benzene, observing olfactory and/or visual evidence of impacts, and the judgment of the environmental scientist. Soil core lithology is also usually logged with a formally accepted methodology such as the Unified Soil Classification System (USCS). The information is documented on a soil boring log, which is included in the investigation report.

Sample collection includes soil, groundwater, if within a reasonable depth, and depending on geologic setting vapor. Soil samples are biased towards evidence of impacts or if no impacts are identified then a few feet above uppermost groundwater. To maximize budget, soil sample collection may be reduced to the most impacted soil interval per boring or even the most impacted interval of the investigation. The number of soil samples collected during the investigation usually does not significantly increase total cost unless the samples are actually analyzed. Decisions on which soil samples to analyze can be prioritized based on the number collected, sample results, holding times, and planned budget. Its easier and less expensive to collect more samples than actually analyzed than having to remobilize later to the property to collect additional soil samples.

Groundwater sample collection in the direct push scenario is typically through the drilling tools or a temporary well, such as PVC screen and riser set into the open borehole, using a peristaltic pump or bailer. Samples collected in this fashion are referred to as grab samples. Temporary wells are minimally purged to facilitate sample collection, but are usually not developed or protected for long-term installation; therefore, they are not considered reproducible sample points and data from these wells usually cannot be submitted for tank or release closure purposes. Longer-term or permanent small-diameter monitoring wells can be installed using direct push methods if the investigation warrants a developed, reproducible sample point.

Sample analysis for petroleum indicator constituents typically includes benzene, toluene, ethylbenzene, and xylenes (BTEX compounds) for gasoline releases and polynuclear aromatic hydrocarbons (PAHs) for diesel and kerosene releases. Benzene will usually be the cleanup driver in more recent gasoline releases while benzo(a)pyrene will typically be the driver for diesel releases. Many states will also require oxygenates, lead, and petroleum hydrocarbon mixture analysis depending upon age and type of release. Petroleum mixture analysis comes in various forms by state, but in general the objective is to reduce false positives and fractionate the hydrocarbon to appropriate risk evaluation levels. If waste oil is suspected, such as at an older automobile repair facility, then target volatile organic compounds, including halogenated volatiles, metals, and polychlorinated biphenyls analysis may also be necessary to appropriately investigate a potential release. Attention to state guidance on analytical parameter set, analytical methods, detection limits, and laboratory certification is important and should be done in the investigation planning stage.

Data evaluation of the investigation analytical results is initially a comparison to state tank program and perhaps voluntary cleanup program generic levels for soil and groundwater. The levels are usually risk-based and being generic means they are developed using default risk model inputs. Therefore, a consideration of land use, exposure pathway and receptor are typically represented in the generic cleanup values.

Further evaluation using site-specific data and more robust models may be used in the formal closure process. However, these methods usually require additional data gathering and evaluation not intended for the presence or absence designed investigation. Many state’s refer to the generic to specific data evaluation process as a tiered system. One evaluation hazard of the due diligence investigation is to combine available analytical data with site-specific probabilities to extrapolate risk-based scenarios too far.

In general, the data evaluation should answer whether impacts are present and whether they exceed a reasonable and appropriate generic screening or cleanup level (i.e., trigger some type of further action, which may include reporting). Attention to potential reporting requirements, especially when conducting investigations in reporting sensitive states, should be discussed in the investigation planning stage.

The cost to conduct a due diligent assessment and follow up investigation of a potential petroleum release ranges considerably on decision and liability data requirements. The Phase I ESA typically costs between $1,500 and $3,500 depending upon scope, location, and type and size of facility. The Phase I ESA cost can be controlled for smaller loans by using a desk-top records review, which typically costs around $500. A site investigation can range from about $6,000 to $24,000 depending upon whether a geophysical survey is warranted, hydrogeologic setting, location, and scope, which is chiefly related to the number of borings and number of samples analyzed. In today’s market, the cost of an investigation can be broken down as follows: laboratory 25% to 50% of cost, drilling 15% to 25%, geophysical survey up to 25%, consultant’s field labor and expenses up to 15%, and consultant’s office labor and expenses up to about 30%.