Well No. 7 FAQ

The City of Edina’s Well No. 7, a seasonal well located in Sherwood Park near the new Grandview Square development, has been found to contain vinyl chloride, a colorless organic gas with a sweet odor. Seasonal wells operate during the summer months to accommodate irrigation and increased water demand. The well was shut down in early October 2003 pending an investigation by the City, its consultants and the Minnesota Department of Health.

What is vinyl chloride?
Vinyl chloride is an organic colorless gas at normal temperatures and is a liquid at temperatures at or below 56 degrees. It can be smelled at concentrations of 3,000 parts per million (ppm) in air and tasted at approximately 3.4 ppm in water. Vinyl chloride is a man-made substance, or the result of a breakdown of a man-made substance.  

Vinyl chloride is used in the manufacture of numerous products in building and construction, automotive industry, electrical wire insulation and cables, piping, industrial and household equipment and medical supplies and is depended upon heavily by the rubber, paper and glass industries.  

Where does vinyl chloride come from?
The typical source of vinyl chloride, according to the Environmental Protection Agency (EPA), is discharge from plastics factories. Vinyl chloride can also be a byproduct of degradation of other complex chlorinated compounds such as cleaning agents and solvents.

The source of the contaminant in Well No. 7 has not yet been determined. The City’s wellhead protection consultant, SEH Inc., reviewed potentially hazardous sites and ruled out all known contaminated sites in Edina within a one-mile radius of the well. In addition, Well No. 7 was televised to verify the integrity of the steel well casing pipe. No evidence of any damage or structural failure of the pipe was found. The Minnesota Department of Health (MDH) is currently analyzing data collected from wells in other communities. 

What are the health risks of exposure to vinyl chloride?
The effects of drinking high levels of vinyl chloride are unknown. Potential health risks are damage to the nervous system and liver.

No symptoms of sickness or disease have been reported to the City since the problem was discovered.

How do the levels of the contaminant in Well No. 7 compare to the MCL?
The Maximum Contaminant Level (MCL) of vinyl chloride is 2.0 parts per billion (ppb). In 2002, as reported in last year’s Edina Consumer Confidence Report, the average level of vinyl chloride in Well No. 7 was 2.3 ppb. Two more samples exceeded the MCL in 2003.  

What percentage of the City’s water supply comes from Well No. 7?
The City of Edina provides drinking water to residents from a groundwater source. Eighteen wells, ranging in depth from 380 to 1,130 feet, draw water from the Mt. Simon and Prairie du Chien-Jordan aquifers. Seven of the wells run year-round. Eleven are seasonal, running during the peak water-consumption season from April to October.

Well No. 7 provides just 0.2 to over 2.0 percent of the City’s total water supply during the summer irrigation season. The well is shut down the remainder of the year.

If I live close to Well No. 7, do I have a higher risk of exposure to vinyl chloride?
Water from Edina’s wells is, in essence, co-mingled with water in other nearby wells in the distribution system. A person living close to Well No. 7 might have a marginally higher risk of exposure to vinyl chloride. However, the water coming from the tap will be a mixture of water from several other wells in the area and so the levels of vinyl chloride will be lower than what is coming from the well.

Does the concentration of vinyl chloride at the tap in my house exceed EPA standards?
No. First, it is believed that the co-mingling effect noted above likely reduces the level below the MCL. Second, aeration that typically occurs at the tap reduces concentrations.

Do levels of vinyl chloride above 2.0 ppb pose an immediate health risk?
The EPA standard of 2.0 ppb was established based on studies of exposure and risk, public health implications and the technical and economic feasibility of removing the substance from water, among other things. There is no direct evidence that concentrations at this level are harmful. However, the City is committed to reducing the level to the EPA standard. 

Why didn’t the City abandon Well No. 7 in 2002 after the first test exceeded the MCL?
MDH tests water from municipal wells. Under the MDH protocols, wells are tested periodically in order to develop an average of potential contaminant levels. The MCL for vinyl chloride has been established as the average of four consecutive quarterly samples. If the MCL is exceeded for four consecutive sampling events, the City will be issued a compliance violation by MDH, at which point it will have to follow a public notification process. 

Have any of the City’s other wells been contaminated?
Maximum contaminant levels of vinyl chloride have not been found in any of the City’s other wells. Trace amounts of the contaminant have been found in two other wells. 

How is the City planning to deal with the vinyl chloride contamination?
Progressive Consulting Engineers has completed a feasibility study for treating Well No. 7 to reduce the levels of vinyl chloride. Because vinyl chloride is a highly volatile organic compound, it is easily removed by aeration. One alternative under consideration is a packed tower aeration in combination with filtration. Cost of the project is approximately $900,000 and would take at least 18 months to complete. Other options include abandoning the well and drilling a new one or piping Well No. 7 with another well and building a treatment plant. Either of those projects would cost $1.5-$2.5 million. 

Until the well can be treated, will the City have an adequate water supply to serve its residents?
The City’s regular odd-even sprinkling ordinance goes into effect May 1 to conserve water. Until Sept. 1, homes with even-numbered addresses may water their lawns on even-numbered dates. Homes with odd-numbered addresses may water on odd-numbered dates. Because Well No. 7 will not be in operation this summer, though, it is possible that other watering restrictions will be put into place. 

What about private wells?
Wells in Edina are typically influenced by groundwater coming from a northwesterly to southeasterly flow. There are a number of residences in northwest Edina with private wells. The MDH has urged the City to test some of those wells to determine the extent of the contamination. A consultant has been retained to determine which private wells the City should test.