Groundwater
Bannock County Groundwater

What is safe drinking water?


Clean and safe drinking water is a basic human need.

In the United States, the Safe Drinking Water Act (SDWA) is the main federal law that governs drinking water quality served by regulated public water systems. The Idaho Department of Environmental Quality adopted this law along with the responsibility to oversee public water systems in Idaho and to enforce the national health-based standards and requirements.

The National Primary Drinking Water Regulations or primary standards define the maximum contaminant levels (MCLs), numerical limits for specific contaminants, which are intended to protect public health. These limits are legally enforceable for public water systems, but not for privately-owned domestic wells.

The following tables show some of the MCLs for safe drinking water.


National Primary Drinking Water Standards as of July 1990 (enforceable)

Inorganic chemicals

Contaminant MCL (mg/L)
Arsenic 0.05
Barium 1
Cadmium 0.01
Chromium 0.05
Fluoride 4
Lead 0.05
Mercury 0.002
Nitrate (as N) 10
Selenium 0.01
Silver 0.05

Organic chemicals

Contaminant MCL (mg/L)
Endrin 0.0002
Lindane 0.004
Methoxychlor 0.1
2,4-D 0.1
2,4,5-TP (Silvex) 0.01
Total Trihalomethanes
(Chloroform, Bromoform, Bromodichloromethane, Dibromochloromethane)
0.1

Volatile Organic Chemicals

Contaminant MCL (mg/L)
Benzene 0.005
Carbon Tetrachloride 0.005
Para-dichlorobenzene 0.075
1,2-dichloroethane 0.005
1,1-dichloroethylene 0.007
1,1,1-trichloroethane 0.2
Trichloroethylene 0.005
Vinyl Chloride 0.002

Radionuclides

Contaminant MCL (mg/L)
Radium 226 and 228 5 pCi/L
Gross Beta Particles 4 mrem/yr or 50 pCi/L
Gross Alpha Particles 15 pCi/L

Microbiological Contaminants

Contaminant MCL (mg/L)
Total Coliform 1/100 ml
Giardia Lamblia TT
HPC TT
Legionella TT
Virus TT
Contaminant MCL (mg/L)

Turbidity

1-5 units

National Secondary Drinking Water Standards (not enforceable)

Contaminant MCL (mg/L)
Chloride 250 mg/L
Color 15 color units
Copper 1 mg/L
Corrosivity Noncorrosive
Fluoride 2.0 mg/L
Foaming Agents 0.5 mg/L
Iron 0.3 mg/L
Manganese 0.05 mg/L
Odor 3 TON
pH (acidity) 6.5 – 8.5 on scale
Sulfate 250 mg/L
Total Dissolved Solids (TDS) 500 mg/L
Turbidity 5.0 NTU
Zinc 5 mg/L

General Water Quality Parameters

Test Excellent Quality Satisfactory Quality Objectionable Quality Problem
Iron 0.05 – 0.2 0.2 – 0.5 over 0.5 Staining, rust, taste
Sodium 0 – 20 20 – 250 over 250 Taste. Special diets may require water of low sodium content.
Nitrate as N 0 – 1 1 – 10 over 10 (state and federal drinking water standard) Nitrate above 10.0 considered health risk for infants.
Hardness as CaCO3 25 – 60 60 – 120 over 120 Scaling of water heater and fixtures, soap scum.
Chloride 0 – 20 20 – 250 over 250 Taste, corrosion.
Fluoride 0.8 – 1.7 0 – 0.8 or 1.7 – 2.4 over 2.4 (state and federal drinking water standard) Low levels beneficial in preventing tooth decay. High levels cause mottling of teeth.
pH value 7.0 – 8.0 down to 6.5 up to 8.5 below 6.4 above 9.0 below 6.4, corrosive. above 8.5, taste
Conductivity 0 – 0.4 0.4 – 0.85 over 0.85  
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