Press Release

BALTIMORE, MD (July 9, 2004) – Levels of the gasoline additive that has contaminated water wells in the Upper Crossroads section of Harford County appear to be dropping dramatically at a potential source, as a result of cleanup work being done.

The Maryland Department of the Environment (MDE) has been working with Harford County Health Department and ExxonMobil officials to fully investigate groundwater contamination caused by the widely used gasoline additive, methyl tertiary butyl ether, MTBE.

MDE reports that MTBE levels in the tank field of the ExxonMobil station at MD Routes 152 and 162 have fallen significantly. At one time in past months, the tank field recorded MTBE readings of 26,000 parts per billion (ppb). Readings for the well have fallen to 97.3 ppb. Four other monitoring wells near the station have also experienced significant drops in concentrations since the installation of a vapor recovery system on June 17.

“These figures indicate that actions taken at the gas station in recent weeks are proving beneficial,” said MDE Deputy Secretary Jonas A. Jacobson. “We share the public’s concern and are committed to continued oversight of this investigation to ensure the protection of the environment, public health and safety.”

MDE is convinced that the ExxonMobil station is responsible for at least part of the MTBE contamination present in the Upper Crossroads area. However, other sources are being considered and may be proved to have contributed to this issue.

At the request of MDE an enhanced leak detection test called the Tracer Tight -- Enhanced Leak Detection ("Tracer") -- method will be conducted at the station starting next week. Praxair Services, an independent contractor hired by ExxonMobil, will conduct the test. MDE will provide oversight during the testing period that will take 3 to 7 days.

The goal of a Tracer test is to detect and repair all leaks and to ensure a tight operating system upon completion of the test. To obtain an accurate test the service station must be operating during the testing period.

The Tracer test can detect both liquid and vapor releases from the underground storage systems at a level below the threshold for regulatory compliance and below the most commonly required release detection tests. But there are limits to the Tracer test. It can provide a general idea where a system problem may be, but in some cases cannot pin point a problem. Also, unlike other tightness tests, the test does not provide a quantifiable leak rate. It could however provide additional confirmation that the UST system is tight or help identify a previously undiscovered problem with the system.

In recent weeks, 233 residential wells were sampled, with the vast majority testing below the state action level of 20 ppb. This week an additional 70 homes in the Orchard Lakes subdivision are being sampled.

For more details of the investigation go to MDE’s website at: and click on the link in the “In Focus” section.

MTBE replaced lead as an octane enhancer in gasoline and helps the fuel burn more completely, thereby reducing harmful tailpipe emissions from motor vehicles.

MTBE can become introduced into the environment, particularly water, from leaking underground and aboveground petroleum storage tanks. Other sources of MTBE include atmospheric deposition, stormwater runoff, watercraft and residential usage of fuels. EPA reports MTBE has been widely found in ground and surface water across the country.