Project Background

In 2015, EBI Consulting was retained by the owner of a retail strip plaza property to conduct a Phase I Environmental Site Assessment (ESA) to identify any potential Recognized Environmental Conditions (RECs) on the property. Like many retail plazas, various tenants occupied the space, including shops, restaurants, and a dry cleaning facility. Evidence of a dry cleaner on site raises a red flag because of the environmental hazards associated with them. After identifying the presence of the dry cleaner, EBI worked with the client to determine the best course of action to meet their needs.


Dry Cleaning Contaminants

When dry cleaning was first developed in the mid-nineteenth century, solvents were made with kerosene, gasoline, turpentine, and other petroleum-based products. As such, they were highly flammable, and many storefronts sent clothing to remote facilities where the dry cleaning was actually performed. When perchloroethylene (PCE) and trichloethylene (TCE) were introduced to the US market in the 1930s, inexpensive, non-flammable solvents that could be used on-premises were developed, expanding the availability of dry cleaning across the country.

PCE, often referred to as perc, and TCE are chlorinated solvents with carcinogenic properties and ozone-depleting toxins that are harmful even in small concentrations and persist in the environment for a long time. Exposure is typically through contaminated drinking water or inhalation. These chemicals can migrate through concrete floors, and their density allows them to sink and become highly mobile in groundwater. They are also volatile organic compounds (VOCs), meaning they readily vaporize and can be released into the atmosphere, impacting the environment and people who may inhale the compounds.

Because of PCE and TCE’s long life, even decades-old dry cleaning sites can be hazardous. A 2007 study by the city of Santa Clara found that dry cleaning sites as old as 50 years pose a greater threat to groundwater than present day ones because of the high concentration of chlorinated solvents found. The contamination was a result of poor equipment prone to leaking and spills, and worse, 70% of drycleaners reported intentionally dumping or releasing solvents into sewer, septic or soil according to a 1988 survey by IFI.


Regulations & Liability

The introduction of CERCLA in 1980 and the advent of PCE and TCE regulations in the 1990s added new complexities for property owners: there were now legal considerations in purchasing a property with a dry cleaner that may have contributed to contamination. CERCLA laws aimed not only to remediate contaminated sites, but to find liable parties to foot the bill for the cleanup. As a measure to enforce this, CERCLA created a set of standards and conditions for the purchase of contaminated properties, including “all appropriate inquiry” (AAI) which states that a purchaser must conduct a site investigation evaluating a property’s environmental conditions and assessing potential liability for any contamination before the acquisition is complete. If this measure is not properly taken, then the liability of any contamination and the effects of it can fall on the purchaser.

For many property owners, a Phase II Site Investigation can minimize legal liability and allow for remediation of the property, if necessary, which may mitigate concerns a future purchaser could have regarding the dry cleaners presence on a property. Phase II Site Assessments may incorporate a number of different components to accurately assess any potential contamination of a site. This assessment can effectively demonstrate to future purchasers, investors, or private equity firms that remediation work has already been assessed, and possibly completed.

From soil and groundwater sampling, groundwater flow modeling, to risk characterization and contaminant source differentiation, there are a number of different investigations and assessments EBI Consulting provides at the Phase II level. These can be customized to address specific site and contaminant concerns so clients receive the best and most accurate assessment without going needlessly over budget.

In the case study described here, because the dry cleaning facility had occupied the space for over 35 years and used solvents such as PCE, there was a potential for contamination on the site. Given the possible impact of the solvents on the subsurface conditions of the surrounding property, EBI recommended a Phase II Subsurface Investigation and Indoor Air Quality Assessment to determine whether the dry cleaning operations had any impact on the property.


Phase II Investigation & Assessment

The Phase II Subsurface Investigation first involved drilling a series of borings on the exterior of the property with an auger rig. From these borings, soil samples were collected at intervals of 4 foot depths, and groundwater samples collected at depths of 12 feet and 40 feet, following EPA test methods for hazardous waste.

Next, a Vapor Intrusion Assessment was completed to evaluate levels of VOCs coming from sub-slab soil vapors. Focusing on the interior of the property, EBI installed four sub-slab vapor pins in the basement of the building and collected samples from each location. Additionally, four air samples were also taken at the property as part of the Indoor Air Quality Assessments to evaluate levels of VOCs above ground. These were taken from the basement and first floor, and one just outside the building to provide additional data on the normal conditions in the area.

After this more rigorous investigation, sampling and subsequent analysis, EBI concluded there was a low level of PCE contamination present in the groundwater. However, the investigation revealed a concentration of PCE in sub-slab vapor. This posed a vapor intrusion threat to both the dry cleaning facility and surrounding tenants in the plaza. With this information, EBI was able to help the client make a more informed business decision about the property. To mitigate the impacted soil vapor, EBI recommended the installation of a vapor intrusion mitigation system (also known as a sub-slab depressurization system).


Sub-Slab Depressurization System Startup Report

Sub-Slab Depressurization Systems (SSDS) create a negative pressure below a building’s slab to prevent vapors from entering the building. To achieve this, shallow wells are installed into the base immediately below the concrete slab. Then, by creating a vacuum using small-scale blowers or fans, a negative pressure is achieved that prevents vapor from permeating the concrete slab and causing contamination. A SSDS removes contaminated soil vapor at rates that create the vacuum, but low enough that permitting from a local air quality management district (AQMD) is unnecessary.

This process is often used as a cheaper alternative to the more intensive soil vapor extraction (SVE). SVE is a more aggressive approach typically recommended for serious concerns of high-concentration contamination. This approach involves digging deeper, five to fifteen feet wells, the introduction of a treatment compound, as well as a ten horse-power blower and carbon filtration system. SVE is also a far more expensive option—it can be eight times as expensive as SSDS—and it requires permitting by the local AQMD and oversight by the county or state Voluntary Remediation Program (VRP). While SVE directly attacks a plume to reduce concentrations, an SSDS is often a better option for properties where there is no impact on groundwater.

During the Sub-Slab Depressurization System Startup, two SSDS wells and six soil vapor monitoring points were installed, multiple diagnostic tests were performed, effluent soil vapor samples were analyzed, and a pilot test report written. A pilot test is the beginning step for both SSDS and SVE remediation, as it confirms that the systems implemented will effectively remove the contaminants. Based on the results of the pilot test and system startup, EBI developed its conclusions and recommendations for the site.

As with most remediation of this type, these recommendations included routine monitoring and analytical testing to document air emissions over time and ensure emissions did not exceed applicable emission thresholds. Additionally, quarterly re-evaluations of contaminant levels in soil vapor were recommended to determine the progress the SSDS achieved. Once applicable thresholds were reached and confirmed by testing, EBI suggested the system might then be shut down and removed.


Quarterly Monitoring Report of the SSDS

Following EBI’s recommendations, a Quarterly Monitoring Report on the SSDS was conducted to ensure the SSDS was operating effectively. This report compiled the results of the monthly site visits, inspections, and laboratory testing, confirming that vapor removal did not exceed requirements of the local AQMD. On regular inspection, EBI found the SSDS operating effectively and as planned. EBI recommended shutting the system down and conducting rebound testing to determine if the continued operation of the SSDS was required to mitigate vapor intrusion concerns moving forward.


Summary of Benefits

Phase II ESAs inform the nature and extent of contamination to assist clients in making informed business decisions about the property, and where applicable, provides knowledge necessary to satisfy the AAI standards under CERCLA. EBI Consulting works directly with clients to tailor a scope of work that meets their specific needs and risk tolerances to ensure that the investigation is conducted within the timing and financial constraints of the transaction.

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