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Site Type: Deleted NPL
Updated January 2014
The five-year review has been completed!
The fourth five-year review report was signed on September 30, 2013 and is available in the Site Documents section below.
The results of the five-year review determined that the remedy at the Arsenic Trioxide site currently protects human health and the environment because the SEWUD-East water treatment plant has been upgraded and expanded to provide rural users, formerly on privately owned, impacted wells, with potable water that meets the arsenic Maximum Contaminant Level (MCL) drinking water standard. However, in order for the remedy to be protective in the long term, treated groundwater should be monitored on a more frequent basis, a summary of institutional control activities and results should be submitted by the North Dakota Department of Health to EPA on a regular basis, and the site fact sheet should be updated to discuss watering of livestock and poultry.
The Arsenic Trioxide site is located in southeastern North Dakota. It covers approximately 26 townships (about 568 square miles) encompassing portions of Richland and Sargent counties. The site area is sparsely populated farmland with a few small towns, including Lidgerwood, Wyndmere, Milnor and Hankinson. The site topography is primarily low rolling hills and flat plains. Groundwater aquifer systems include shallow glacial drift aquifers approximately three to 150 feet deep and the Dakota Sandstone aquifer approximately 200 to 1,000 feet deep. Groundwater with elevated arsenic levels appears to be limited to the shallow aquifers and does not extend into the deeper aquifers. The shallow aquifer is commonly used as a source of drinking water in the region.
The occurrence of arsenic in groundwater is attributed to both the historical use of arsenic-based grasshopper bait and naturally occurring sources.
During the 1930s and early 1940s, arsenic-laced bait was used extensively throughout North Dakota to combat grasshopper infestations. The bait, which included arsenic trioxide, sodium arsenate, Paris Green and other arsenic compounds, was commonly applied on farm fields.
The area's residents are subject to increased health risk due to exposure to arsenic above the Maximum Contaminant Level (MCL) in untreated drinking water supplies. The Safe Drinking Water Act (SDWA) MCL for arsenic is 0.01 mg/L.
|Media Affected||Contaminant||Source of Contamination|
|drinking water||arsenic||historical use of arsenic-based grasshopper bait and naturally occurring (background) levels of arsenic|
EPA conducted a Remedial Investigation (RI) in 1985 to determine the nature and extent of arsenic contamination in the groundwater in southeastern North Dakota. The RI identified several groundwater wells that exceeded the SDWA MCL for arsenic, which, at the time, was 0.05 milligrams per liter (mg/L).
Once the RI was completed, EPA conducted a Feasibility Study (FS) to evaluate options to protect human health and the environment in the areas identified in the RI where the arsenic contamination was not only naturally occurring but could be attributed, at least in part, to the bait application or storage.
The remedy selected for the site provided for the expansion of three water treatment plants, installation of approximately 300 miles of water distribution pipeline, construction of additional water storage reservoirs and tanks, and installation of additional water supply wells. The remedy was completed in June 1993, and the site was removed from the National Priorities List (NPL) in July 1996.
In 2001, the MCL for arsenic was lowered to 0.01 mg/L, with this new standard becoming enforceable in January 2006. This prompted a five-year review in June 2003. The review determined that the remedy was no longer protective of human health. As a result of this review, the communities of Wyndmere and Hankinson were connected to the Southeast Water Users District (SEWUD) rural water supply system. These construction activities also included the expansion of the SEWUD water treatment plant. Construction activities were conducted between 2005 and 2007. In addition to these activities, sampling was conducted to determine if the wells of rural water users exceeded the new arsenic standard. If well water exceeded the arsenic standard, users were provided bottled water as a temporary measure.
During the summer of 2008, approximately 60 additional users were connected to a rural water supply system because of elevated arsenic concentrations in their drinking water wells. This work was done under Segment 3.
In September 2008, the bottled water program transitioned from EPA's Removal Program to the State of North Dakota Department of Health (NDDH). The bottled water program was an interim remedial action and provided clean drinking water to users who were waiting for connections to the rural water supply system. EPA also completed the third five-year review in September 2008. This review indicated that human health will be protected in the long-term upon completion of the planned remedial actions and the implementation of institutional controls.
EPA is working with the NDDH to ensure that the residents within the Arsenic Trioxide site boundary have safe drinking water. EPA and NDDH signed an additional decision document that describes: 1) the rationale for connecting additional users to the rural water system, 2) the expansion of the water treatment plant and storage capacities, and 3) institutional controls necessary to protect future well-water users from unknowingly drinking arsenic-contaminated water. The decision document was signed on February 20, 2009 and can be found in the Site Documents section.
The Arsenic Trioxide Superfund Site received $1.8 million in remedial design and $12 million in remedial action funding through the American Recovery and Reinvestment Act (ARRA) of 2009. These additional funds from the ARRA were used to provide 162 households and small businesses in Richland and Sargent counties with safe drinking water. EPA and the State of North Dakota have been connecting water users to a rural water supply because many drinking water wells in the area are contaminated with elevated levels of arsenic. The ARRA funding also paid for the expansion of water treatment and distribution facilities to handle the increased demand from the additional number of users. The funding from the ARRA has allowed the site work to be completed one year sooner than originally planned.
The ARRA provided 100 percent of the design funds and 90 percent of the construction funds for Segment 5 of the project, which is the final phase of the project. Segment 5 was divided into three separate designs and related construction contracts for the pipeline installation, facilities construction and well field expansion. Construction on Segment 5 began in April 2010 and was substantially completed in September 2011.
The construction included:
- Expanding the well field to ensure availability of an adequate quantity of raw water.
- Upgrading the water treatment facility with an additional filter vessel.
- Constructing a new reservoir and pump station to maintain adequate flows to an area previously unserved by rural water.
- Upgrading four pump stations so that adequate service would be provided to new users and so that existing users maintained the level of service they were experiencing prior to the expansion.
- Constructing two new storage reservoirs to provide system capacity.
- Installing an emergency generator to diminish the impact of service interruptions due to loss of power.
- Installing a geothermal system to lessen the system’s dependency on non-renewable energy sources.
Construction activities associated with providing water service to the 162 rural households included installing approximately 95 miles of 2-inch water line, 49 miles of 3-inch water line, 5 miles of 4-inch water line, 4 miles of 6-inch water line, and associated valves, hydrants, curb stop assemblies, and residential meter setter units, along with the project features previously mentioned.
Construction on Segments 4 and 4A was also completed in 2011. This work was not funded by the ARRA. It consisted of expanding rural water service to 119 rural residences in the eastern portion of Richland County and to the communities of Cayuga and Geneseo. Construction activities associated with providing water service to the rural households included installation of approximately 57 miles of 2-inch water line; 11 miles of 3-inch water line; 7 miles of 4-inch water line; 22 miles of 6-inch water line; 7 miles of 8-inch water line; 3 miles of 10-inch water line; and associated valves, hydrants, curb stop assemblies, and residential meter setter units. Additionally, Segment 4A construction was necessitated by the activities completed during Segments 1 and 3 of the Arsenic Trioxide project. Bulk water service to the city of Wyndmere (Segment 1 construction), combined with the additional demand added to the system with the additional users in the Wyndmere area (Segment 3 construction), resulted in the need to upgrade the process piping and electrical controls in the Reservoir B pump station. The additional users which were added in southern Brightwood Township, including those in the vicinity of Lake Elsie, required similar upgrades to the Reservoir G pump station.
Community involvement plays an important role in the Superfund process. EPA uses a number of different tools and resources to promote effective, on-going, meaningful community involvement. The goals of the Superfund community involvement program are to:
- Keep communities affected by sites informed throughout the cleanup process
- Provide opportunities for communities to comment and offer their input about site cleanup plans
- Facilitate the resolution of community issues tied to a site
Community meetings were held in during the summers of 2008 and 2009 to provide a site status update to residents and to describe how to sign up to be connected to the rural water distribution system. An informational fact sheet describes the institutional controls at the site.
EPA places a high priority on land redevelopment as part of its Superfund response program mission. EPA tries to select cleanup options that encourage and support future use of a site. EPA uses two fundamental methods to facilitate redevelopment of Superfund sites:
- Exploring future uses before the cleanup remedy is implemented, an approach that gives the Agency the best chance of designing cleanup remedies to support likely future use of a site; and
- Working with communities to remove barriers not considered necessary for the protection of human health or the environment at those sites where remedies are already in place.
One option for redevelopment is the siting of clean and renewable energy projects on contaminated (or formerly contaminated) lands. As part of this effort, EPA is evaluating the potential for energy projects on these properties and working with communities to identify barriers to such projects. In cooperation with EPA, towns and villages around the country are recovering idle properties and returning them to productive use.
Since the Arsenic Trioxide site is an area-wide groundwater site, many types of uses continue to occur throughout the twenty-six township area covered by the site. The primary land use in the area is agricultural.
The Segment 5 work involves installation of a geothermal heating and cooling system at the SEWUD office building in Mantador. The office serves as the control center for the SEWUD system. Geothermal systems use heat pumps to transfer the natural heat of the ground to the building’s heating and cooling system. Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly. Geothermal wells do release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if used in place of fossil fuels. Another significant benefit of a geothermal system is its relatively low electrical operating costs. This will help keep future operational costs low.
Land Use Controls and Other Institutional Controls
Land use controls are the most common type of institutional control (IC). ICs are administrative or legal controls that help reduce the likelihood for human exposure to contamination. ICs can also help protect the integrity of the remedy. Examples of ICs are:
- Zoning ordinances
- Environmental covenants
- Deed notices
- Well-drilling restrictions
- Building permits
- Informational advisories
ICs play an important role in site remedies because they reduce exposure to the contamination remaining on site by limiting land or resource use and guiding human behavior at a site. Zoning ordinances are often used at sites to restrict land use consistent with the level of cleanup. The National Contingency Plan (NCP) emphasizes that ICs are meant to supplement engineering controls and that ICs will rarely be the sole remedy at a site.
The main need for institutional controls at the Arsenic Trioxide site is to inform new residents to the area to have the water from their private drinking water wells sampled and tested to determine if arsenic is present at levels greater than 0.01 mg/L. If arsenic is present at or above that level, residents should consider connecting to the rural water system or installing a point-of-use treatment system in their home that is capable of removing arsenic. A fact sheet has been developed to provide a summary of the ICs for the site.
EPA or the lead agency conducts five-year reviews following the start of a Superfund cleanup when contamination is left on the site. These reviews are repeated every five years. We use these reviews to determine:
- How the remedy is working
- If the remedy remains protective of human health and the environment
The recent five-year review was completed in September 2013 and can be found in the Site Documents section. The results of the five-year review determined that the remedy at the Arsenic Trioxide site currently protects human health and the environment because the SEWUD-East water treatment plant has been upgraded and expanded to provide rural users, formerly on privately owned, impacted wells, with potable water that meets the arsenic Maximum Contaminant Level (MCL) drinking water standard. However, in order for the remedy to be protective in the long term, treated groundwater should be monitored on a more frequent basis, a summary of institutional control activities and results should be submitted by the North Dakota Department of Health to EPA on a regular basis, and the site fact sheet should be updated to discuss watering of livestock and poultry.
The next five-year review is scheduled for 2018.
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Institutional Controls Fact Sheet, January 2014
Fourth Five-Year Review Report, September 2013
OU1 Explanation of Significant Differences (PDF), February 20, 2009 (12 pp, 3.1 MB)
OU1 Explanation of Significant Differences (PDF), February 25, 2008 (10 pp, 2.7 MB)
OU1 Explanation of Significant Differences (PDF), September 27, 2007 (9 pp, 2.5 MB)
OU2 Explanation of Significant Differences (PDF), September 25, 1992 (7 pp, 46 K)
OU2 Record of Decision (PDF), February 25, 1988 (6 pp, 1.3 MB)
OU1 Record of Decision (PDF), September 26, 1986 21 pp, 42 K)
EPA Project Manager
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (EPR-SR)
Denver, CO 80202-1129
800-227-8917 ext. 312- 6571 (toll free Region 8 only)
Site Information Repositories:
Southeast Water Users District
206 Main Street
Mantador, ND 58058
Lidgerwood Public Library
15 Wiley Avenue
Lidgerwood, ND 58053
EPA Superfund Records Center
1595 Wynkoop Street
Denver, CO 80202-1129
To request copies of administrative record documents call:
800-227-8917 ext. 312-7273 (toll free Region 8 only)
Ground Water Protection Program
North Dakota Department of Health
918 East Divide Avenue, 4th Floor
Bismarck, ND 58501
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