* Releases may be closed after they are investigated, and if necessary, cleaned up, and the remaining contaminant levels in soil and groundwater are determined not to cause a further threat to human health or the environment.

The first public meeting was held in Winslow on July 21, 2004 to get the project underway. ADEQ has assigned a case manager (David Burchard) who is dedicated to the Winslow Project. ADEQ personnel have met with many of the property owners, and will continue to schedule meetings as needed to help expedite corrective actions. In addition, ADEQ has a liaison for the northeastern area of Arizona (Byron James) who lives in St. Johns, and frequently makes trips to Winslow to meet with local officials and property owners.

Past and Current Activities

LUST Site Information

• If you would like to review the current site status, please refer to the summary table.
• Map of Winslow UST Sites
• More photos of remedial activities in Winslow

Groundwater/Soil and Fuel Related Contaminants in Winslow

All aquifers in Arizona are subject to State and Federal drinking water standards. However, groundwater in the shallow aquifer in Winslow is not typically used as drinking water due in part to high salt content. The municipal drinking water supply in Winslow is produced from a well field 7 miles to the south southwest of the town in Coconino County.

Although the shallow groundwater is not part of the municipal water supply, human exposure to contaminants can occur from contaminated soil and groundwater. Exposure can be the result of dermal (skin) contact or the inhalation of vapors from volatile contaminants in soil or groundwater. There are many routes of exposure including excavation during construction, or vapors migrate upward through shallow soils into buildings. For these reasons, the State has also set cleanup standards for soil.

Gasoline is a complex mixture of chemicals. However, cleanup standards have been set for a few chemicals of concern, including benzene, toluene, ethylbenzene, and xylenes (BTEX) and gasoline additives such as methyl tertiary butyl ether (MTBE) and 1-2 Dicloroethane (1-2 DCA).

Petroleum products, like gasoline and diesel fuel are called LNAPLs (light non-aqueous phase liquids), and, as a pure product, float on top of the groundwater. Not all leaks result in product being released in a manner that promotes a build up of "free product" that floats on the groundwater. When a leak (release) occurs, the product migrates downward through the soil (unsaturated zone). When the released product reaches the water table, the fuel slowly dissolves into the groundwater, and a plume develops. This plume migrates with the groundwater in the direction of groundwater flow. When groundwater samples are collected, they are analyzed for the presence of chemicals of concern that are typically associated with the product that was released. For example, gasoline is a complex mixture of chemicals. However, cleanup standards have been set for a few of the more hazardous chemicals, including benzene, toluene, ethylbenzene, and xylenes (BTEX) and gasoline additives such as methyl tertiary butyl ether (MTBE).

Cleanup Technology

Proposed and ongoing soil and groundwater cleanup activities in Winslow include a variety of methods, such as soil excavation, multi-phase extraction, vapor extraction, air sparging, natural attenuation and free product removal (where present) from the top of the groundwater table.

Groundwater is generally shallow and is encountered at a depth of approximately five to 20 feet below the ground surface (bgs). Bedrock is also encountered near the surface, typically at a depth of approximately 10 to 20 feet bgs. The observed bedrock generally includes interbedded siltstone, mudstone, sandstone and gypsum. The bedrock near the surface at LUST sites in the Winslow area has been primarily identified as the Moenkope formation. Soil above the bedrock is composed primarily of clay and silt.

Due to the presence of finer grained material at many of the sites and in some cases groundwater observed in fractured bedrock, cleanup may require the use of more innovative technologies. One of the more innovative technologies that is being used is multi-phase extraction. In this technology, contaminated groundwater and free product (if present) and vapors are slowly withdrawn, separated, and treated on the surface. A second method that is commonly being used to cleanup soils in the Winslow area is excavation. Excavation is cost effective at sites where there is limited soil contamination and bedrock is near the surface.

More than one cleanup method is often used to remove contaminants. The effectiveness of each method depends on the nature of the site.

The cleanup work must be technically feasible, reasonable, necessary and cost effective to actively remove contaminants. When "active" cleanup technologies don't meet these criteria, a more "passive" approach can be taken by allowing the existing bacteria in the ground reduce contaminant levels. This is called the natural attenuation process, in which the contaminants act as a food source for the existing bacteria. Natural attenuation can be monitored to make sure contaminants are degrading, and can either be used as a stand alone technology or used after "active" cleanup technologies have removed the majority of the contamination.

If you would like more information about the UST program and corrective action technology, please visit the U.S. Environmental Protection Agency's web site .

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