Hackensack Wells Site

This web page provides general information about the public health issues associated with a hazardous waste site for people living near the site and others who are interested. It does not provide a comprehensive discussion of all available technical information about the site, or of all health issues possibly related to the site. More detailed information can be found in a 1997 health assessment of the site available from the Minnesota Department of Health (MDH).

Site description and history

The Hackensack Wells Site in Cass County was formerly occupied by a service station, known as "Bill's Amoco." The site is in the city of Hackensack, which has a population of 250 people. It is located one block from the town's main business street. (see map showing the location of Bill's Amoco)

The Amoco station building is still in use, and is one of a small group of retail stores. The portion of the site where underground gasoline storage tanks once were buried is covered by black-top. The paved area lies between the Amoco station building and an adjoining business that was built on the site after the station closed.

The site lies 900 feet from the two Hackensack municipal wells. The Boy River (south of the site) and Birch Lake (east of the site) are designated "protected surface waters" by the Minnesota Department of Natural Resources. Therefore, extra care is required in the performance of activities near these surface waters.

The Amoco station was in operation from the 1940's until 1989. In 1990, soil and groundwater contamination were identified during the removal of eight underground storage tanks. At that time, about 1100 cubic yards of contaminated soil were removed from the site, and a system to pump out and treat the contaminated water was installed. Operation of this system was stopped in May 1995 because it had become less efficient due to changes in the water table.

In December 1995, contaminated groundwater was detected in the municipal wells by investigators from the Minnesota Pollution Control Agency (MPCA). The MPCA found contaminants similar to those typically released from old gas stations. A system previously installed by the city to control iron levels in the water has also helped to reduce groundwater contamination. The current contaminant levels in the city water are within MDH standards for drinking water.

MDH is working with the MPCA and other local agencies to clean up the groundwater contamination. Staff at these agencies are working to evaluate the scope of the problem, and to assess the potential for future public health problems.

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What contamination has been found and where is it?

Petroleum products, such as benzene, ethyl benzene, toluene, and xylene have been found at the site. The chemical 1,2 dichloroethane (DCA) has also been detected. DCA has historically been used in degreasing products, and as an additive used to remove lead from leaded gasoline.

At this time, MDH has determined that the contamination at this site is not affecting the air quality. There is some contamination of the surface soil and the surface water, but these levels are very low because most of the contamination occurred underground. The soil contamination has been reduced because much of the contaminated soil was removed several years ago.

The remaining soil contamination lies well below the surface — in areas that would be very hard to excavate. The small amount of soil contamination that still exists could possibly affect the quality of the groundwater. However, people are unlikely to be exposed to levels that would be of health concern.

Contamination of the groundwater is a bigger concern. Contaminants have flowed from the site into the two municipal wells. The chemical DCA was found in the city water at varying levels in 1996. The amounts of DCA, and possibly the amount of benzene, in this water may increase in the future unless steps are taken to correct the situation.

There has been a steady increase of DCA found in recent water samples taken from beneath the site. That increase will be followed by increased levels of DCA in the well water, as contaminated groundwater flows away from the site into the wells. Recent increases in the amount of contamination are thought to be caused by the rising level of underground water in the area. As the water table rises, water may reach higher pockets of contaminants in the clay and soil beneath the site.

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Are there any health hazards resulting from the contamination?

People who are exposed to the air and surface water are not at risk, because the contaminant levels are very low. However, some of the treatment methods being considered for the site could vent underground contaminants into the air. Therefore, air monitoring must continue. It is unlikely that people will be exposed to the contaminated soil that lies far under the surface and is covered by black top.

The only significant risk to people is from the groundwater, due to the contamination in the municipal water system. The concentrations of the hazardous chemicals in city water are now below health-based standards. Therefore, the contamination levels do not currently pose a health concern.

However, it is not known whether the water treatment systems now being used will be able to handle higher levels of contamination that may occur in the future. If water treatment becomes less effective, or if contamination levels increase significantly, groundwater problems could then pose a health hazard.

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What is currently being done at the site?

The MPCA is considering several clean-up alternatives for addressing the remaining contamination at the site. These include: installing new treatment systems for municipal wells, relocating the wells, and changing the flow of the groundwater.

It is uncertain at this time whether these or other steps will be taken. Technical staff from both MPCA and MDH are coordinating efforts to evaluate the problem, provide suggestions, and ensure that contamination is adequately controlled.

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What protective action does MDH recommend?

MDH has made several recommendations for preventing or minimizing exposure to contaminants. They include:

  • Regular, continued monitoring of private and municipal wells near the site. Continued sampling and analysis of groundwater from the network of monitoring wells. Continued evaluation of venting and other treatment systems. If testing shows that contaminant levels have increased, or that the effectiveness of treatment has decreased, a plan for additional measures should be put in place.
  • Development of a detailed groundwater model, accompanied by a pumping test, to provide a better picture of groundwater conditions at the site. This effort may require additional monitoring wells to gather needed information.
  • Development of a well-head protection plan for the city of Hackensack.

Finally, MDH recommends that area residents be kept informed of the results from any testing or monitoring, and that they be told about these and other recommendations. As additional information becomes available, MDH will continue to review health issues and concerns, and provide this information to concerned parties.

An MDH report (April 1997) on the Hackensack, Minnesota Amoco Station Site is available upon request. To request copies, or for additional information about the site, call 612-201-4897, or 1-800-657-3908 and press "4" to leave a message 24 hours a day, or send an e-mail to health.hazard@state.mn.us.

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Updated Friday, September 16, 2011 at 01:24PM