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Water Quality Results

The results of monitoring in 2012 are shown in the tables below. These results are for parameters regulated by the federal and state agencies. We tested for some 211 contaminants and didn’t find any traces of 201 of those. For other water quality information, please see Water Quality or call (206) 615-0827. To make all the information fit, we used many acronyms that are defined below. In Seattle, if you live south of Green Lake, your water probably comes from the Cedar River. Areas north of Green Lake usually receive Tolt water. Each source can provide water to other areas in Seattle, if needed.

Monitoring Results

  EPA’s Allowable Limits Levels in Cedar Water
Detected Compounds Units MCLG MCL Average Range Typical Sources
Raw Water
Total Organic Carbon ppm NA TT 0.7 0.4 to 1.1 Naturally present in the environment
Cryptosporidium* #/100L NA NA ND ND Naturally present in the environment
Finished Water (after treatment)
Turbidity (cloudiness) NTU NA TT 0.3 0.2 to 2.3 Soil runoff
Barium ppb 2000 2000 1.8 one sample Erosion of natural deposits
Cadmium ppb 5 5 ND one sample Erosion of natural deposits
Fluoride ppm 4 4 0.8 0.7 to 0.9 Water additive, which promotes strong teeth

Nitrate

ppm 10 10 0.02 one sample Erosion of natural deposits
Total Trihalomethanes ppb NA 80 38 16 to 56 By-products of drinking water chlorination
Haloacetic Acids(5 ppb NA 60 44 12 to 72
Chlorine ppm MRDLG=4 MRDL=4 Average = 0.89  
Range = 0 to 1.7
Water additive used to control microbes
Coliform, Total % 0 5% Highest Month = 0.9% Naturally present in the environment
*Cryptosporidium was not detected in any samples from the Cedar or Tolt (3 samples each supply).

 

  EPA’s Allowable Limits Levels in Tolt Water
Detected Compounds Units MCLG MCL Average Range Typical Sources
Raw Water
Total Organic Carbon ppm NA TT 1.2 1.1 to 1.4 Naturally present in the environment
Cryptosporidium* #/100L NA NA ND ND Naturally present in the environment
Finished Water (after treatment)
Turbidity (cloudiness) NTU NA TT 0.06 0.04 to 0.38 Soil runoff
Barium ppb 2000 2000 1.9 one sample Erosion of natural deposits
Cadmium ppb 5 5 0.35 one sample Erosion of natural deposits
Fluoride ppm 4 4 0.8 0.7 to 0.9 Water additive, which promotes strong teeth
Nitrate ppm 10 10 0.13 one sample Erosion of natural deposits
Total Trihalomethanes ppb NA 80 40 19 to 57 By-products of drinking water chlorination
Haloacetic Acids(5) ppb NA 60 38 22 to 55
Chlorine ppm MRDLG=4 MRDL=4 Average = 0.89  
Range = 0 to 1.7

 

Water additive used to control microbes
*Cryptosporidium was not detected in any samples from the Cedar or Tolt (3 samples each supply).

Lead and Copper Monitoring Results

Parameter and Units MCLG Action Level+ 2010
Results++
Homes Exceeding Action Level Source
Lead, ppb 0 15 5 0 of 50 Corrosion of household plumbing systems
Copper, ppm 1.3 1.3 0.14 0 of 50
+ The concentration of a contaminant which, if exceeded, triggers treatment or other requirements which a water system must follow.
++ 90th Percentile: i.e., 90 percent of the samples were less than the values shown.

Although there is no detectable lead in our source water, tests show there are sometimes elevated levels of lead and copper, primarily because of corrosion of household plumbing systems. These results show that it is very important that homeowners, business owners and others be aware of their type of plumbing, and how the plumbing affects their drinking water quality.

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. Seattle Public Utilities is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. Where you live, when your plumbing was installed and what type of plumbing you have, all play a part in determining your potential exposure level. SPU treats the water to minimize the tendency for lead to enter the water, and results show that we have been very successful at this. 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 the EPA website.

Definitions

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.

MRDL: Maximum Residual Disinfectant Level—The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

MRDLG: Maximum Residual Disinfectant Level Goal—The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

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

NTU: Nephelometric Turbidity Unit—Turbidity is a measure of how clear the water looks. The turbidity MCL that applied to the Cedar supply in 2011 was 5 NTU, and for the Tolt it was 0.3 NTU for at least 95 percent of the samples in a month. 100 percent of the samples from the Tolt in 2011 were below 0.3 NTU.

NA: Not Applicable

ND: Not Detected

ppm: 1 part per million = 1 mg/L = 1 milligram per liter

ppb: 1 part per billion = 1 ug/L = 1 microgram per liter

1 ppm =1000 ppb