CITY OF AURORA

2010 Drinking Water Report

PWSID:  1690002

The City of Aurora is issuing the results of monitoring done on its drinking water for the period from January 1 to December 31, 2010.  The purpose of this report is to advance consumers’ understanding of drinking water and heighten awareness of the need to protect precious water resources.

Source of Water

The City of Aurora provides drinking water to the consumer from a surface water source: surface water drawn from the St. James Pit also known as Lake St. James.  Lake St. James is a retired red ore mine that has filled with water from groundwater seepage and precipitation.  The City has obtained a buffer zone around the pit to control any activity which should ensure a stable water source for many years to come.

The water provided to customers may meet drinking water standards, but the Minnesota Department of Health has also made a determination as to how vulnerable the source of water may be to future contamination incidents.  If you wish to obtain the entire source water assessment regarding your drinking water, please call 651-201-4700 or 1-800-818-9318 (and press 5) during normal business hours. 

Also, you can view it on line at www.health.state.mn.us/divs/eh/water/swp/swa.

Call Wayne Thuringer at (218) 229-2624 if you have questions about the City of Aurora drinking water or would like information about opportunities for public participation in decisions that may affect the quality of the water.

Raw Water Quality

The raw water characteristics are of extreme clarity, low Iron and Manganese, and Hardness of 21 grains per gallon.  The Hardness level (caused primarily by the salts of Calcium and Magnesium) is of no health hazard, and only poses a problem in spotting of dishes and some scale build-up on plumbing fixtures.

Treatment

Raw water is pumped from a lift station on the bank of Lake St. James to the treatment facility located on East 4^th Avenue North.  Treatment consists of coagulation, chlorination, fluoridation and filtration.  For coagulation, a cat-ionic polymer is added to the raw water to aid in settling of suspended solids prior to filtration.  Chlorination is a process used to kill all bacteria that occur naturally from animal and human waste.  Gaseous Cl2 is added to the water at a level of 0.2 – 0.6 ppm.  The residual Cl2 level is checked daily at the Water Treatment Facility and also at the Wastewater Treatment Facility (maximum time water is in the system) to ensure proper levels for safe drinking water.  Fluoride, although occurring in low levels from the soil, is added to the water as a hydro acid solution.  Fluoride is maintained at levels of 1.0 – 1.2 ppm for development of strong teeth.  This level is also monitored daily.  After chemical addition the water is filtered through Anthracite coal, sand, gravel filters to remove suspended solids.  The Turbidity is reduced to a level of 0.02 NTU’s (Nephelometric Turbidity Units).  After filtration the water is distributed to the consumer via a network of storage tanks and pipelines.

Distribution

The treatment facility is equipped with a state-of-the-art programmable controller that maintains water levels in the ground storage reservoir and the elevated tank.  Proper water level in the elevated tank is important to provide good water pressure at the tap.  The City of Aurora has been aggressive in upgrading it’s water lines and other components to provide uninterrupted service to it’s consumers.  The residents and businesses of Aurora are very fortunate to have a safe clean water delivered for the low rate that is charged.

Results of Monitoring

No contaminants were detected at levels that violated the federal drinking water standards.  However, some contaminants were detected in trace amounts that were below legal limits.  The table that follows shows the contaminants that were detected in trace amounts last year.  (Some contaminants are sampled less frequently than once a year; as a result, not all contaminants were sampled for in 2010.  If any of these contaminants were detected the last time they were sampled for, they are included in the table along with the date that the detection occurred.)

Key to abbreviations:

MCLG – Maximum Contaminant Level Goal:  The level of a contaminant in drinking water below which there is no known or expected risk to health.  MCLGs allow for a margin of safety.

MCL – Maximum Contaminant Level:  The highest level of a contaminant that is allowed in drinking water.  MCLs are set as close to the MCLGs as feasible using the best available treatment technology.

TT – Treatment Technique:  A required process intended to reduce the level of a contaminant in drinking water.

NTU – Nephelometric Turbidity Unit, used to measure clarity in drinking water.

MRDL – Maximum Residual Disinfectant Level.

MRDLG – Maximum Residual Disinfectant Level Goal.

AL – Action Level:  The concentration of a contaminant which, if exceeded, triggers treatment or other requirement which a water system must follow.

90^th Percentile Level—This is the value obtained after disregarding 10 percent of the samples taken that had the highest levels.  (For example, in a situation in which 10 samples were taken, the 90^th percentile level is determined by disregarding the highest result, which represents 10 percent of the samples.)  Note:  In situations in which only 5 samples are taken, the average of the two with the highest levels is taken to determine the 90^th percentile level. 

ppm – Parts per million, which can also be expressed as milligrams per liter (mg/l).

ppb – Parts per billion, which can also be expressed as micrograms per liter (µg/l).

N/A – Not Applicable (does not apply).

*This is the value used to determine compliance with federal standards.  It sometimes is the highest value

detected and sometimes is an average of all the detected values.  If it is an average, it may contain sampling results from the previous year.

**    Lowest Monthly Percentage of Samples Meeting the Turbidity Limits.

***  Highest Single Measurement.

Turbidity is a measure of the clarity of the water.  We monitor it because it is a good indicator of the effectiveness of our filtration system.  The percentage of Total Organic Carbon (TOC) removal was measured each month and the system met all TOC removal requirements set by the U.S. Environmental Protection Agency (EPA).

**** Highest and Lowest Monthly Average.

***** Highest Quarterly Average.

If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children.  Lead in drinking water is primarily from materials and components associated with service lines and home plumbing.  City of Aurora is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components.  When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking.  If you are concerned about lead in your water, you may wish to have your water tested.  Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline or at http://www.epa.gov/safewater/lead.

Some contaminants do not have Maximum Contaminant Levels established for them.  These unregulated contaminants are assessed using state standards known as health risk limits to determine if they pose a threat to human health.  If unacceptable levels of an unregulated contaminant are found, the response is the same as if an MCL has been exceeded; the water system must inform its customers and take other corrective actions.  In the table that follows are the unregulated contaminants that were detected:

Compliance with National Primary Drinking Water Regulations

The sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs, and wells.  As water travels over the surface of the land or through the ground, it dissolves naturally-occurring minerals and, in some cases, radioactive material, and can pick up substances resulting from the presence of animals or from human activity.

Contaminants that may be present in source water include:

            Microbial contaminants, such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.

            Inorganic contaminants, such as salts and metals, which can be naturally-occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.

            Pesticides and herbicides, which may come from a variety of sources such as agriculture, urban stormwater runoff, and residential uses.

            Organic chemical contaminants, including synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, and septic systems.

            Radioactive contaminants, which can be naturally-occurring or be the result of oil and gas production and mining activities.

In order to ensure that tap water is safe to drink, the U.S. Environmental Protection Agency (EPA) prescribes regulations which limit the amount of certain contaminants in water provided by public water systems.  Food and Drug Administration regulations establish limits for contaminants in bottled water which must provide the same protection for public health.

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants.  The presence of contaminants does not necessarily indicate that water poses a health risk.  More information about contaminants and potential health effects can be obtained by calling the Environmental Protection Agency’s Safe Drinking Water Hotline at 1-800-426-4791.

Some people may be more vulnerable to contaminants in drinking water than the general population.  Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections.  These people should seek advice about drinking water from their health care providers.  EPA/CDC guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the Safe Drinking Water Hotline at 1-800-426-4791.