Ensuring Your Water Meets Drinking Water Standards

 

Tucson Water's Environmental and Regulatory Compliance Section (ERCS) is responsible for ensuring that the water we deliver is safe, clean, and meets all local, state, and federal drinking water health standards. The ERCS employs skilled professionals with backgrounds in biology, chemistry, engineering, geology, hydrology, and management.

Drinking Water Rules Overview

The federal government authorizes the United States Environmental Protection Agency (EPA) to set drinking water standards to protect the drinking water supply. This is done by limiting the levels of certain chemicals or microorganisms that can adversely affect public health and are likely to be present in the water. The Maximum Contaminant Level (MCL) and Action Level (AL) are the health standards established by the EPA that public water systems, such as Tucson Water, must meet to ensure safe drinking water. The MCL or AL is the highest level of a contaminant that is allowed in drinking water.

Once the EPA develops a new standard, the rule is sent to the Arizona Department of Environmental Quality (ADEQ). The EPA has granted ADEQ the right and responsibility to oversee drinking water rules and programs. Under the ADEQ Primacy agreement, federal drinking water rules are incorporated into the Arizona Administrative Code where they then become enforceable by the state.

Local governments and private water suppliers have direct responsibility for the quality of the water that flows to your tap. Tucson Water tests and treats the water provided to customers, maintains the distribution systems that deliver water, and reports on water quality to the state. ADEQ provides technical assistance to water suppliers and can take legal action against systems that fail to provide water that meets these standards.

The ERCS oversees the Drinking Water Regulatory Program. Its core responsibilities include identifying applicable drinking water regulations, communicating those requirements to the Water Quality Laboratory for implementation, and reviewing the results to ensure compliance with drinking water standards.

Which contaminants are required to be monitored?

Tucson Water is required to monitor for at least 89 regulated drinking water contaminants to comply with several drinking water rules. The regulated contaminants and links to EPA Technical Factsheets are listed in Table 1 below.

Table 1. Regulated Drinking Water Contaminants
Regulated Drinking Water Contaminant Total Number of Contaminants Drinking Water Rule
Dimonochloroacetic Acid;
Dichloroacetic Acid;
Trichloroacetic Acid;
Monobromoacetic Acid;
Dibromoacetic Acid
5 Stage 1 Disinfectants and Disinfection Byproducts:
Haloacetic Acids
Antimony;
Arsenic;
Asbestos;
Barium;
Beryllium;
Cadmium;
Chromium;
Cyanide;
Fluoride;
Mercury;
Nickel;
Nitrate;
Nitrite;
Sodium;
Selenium;
Thallium
16 Inorganic Chemicals
Lead;
Copper
2 Lead and Copper
Free Chlorine 1 Stage 1 Disinfectants and Disinfection Byproducts: Disinfectant Residual
Adjusted Gross Alpha;
Radium-226;
Radium-228;
Uranium
4 Radiochemicals
Bromoform;
Chloroform;
Bromodichloromethane;
Chlorodibromomethane
4 Stage 1 Disinfectants and Disinfection Byproducts:
Total Trihalomethanes
2,4-D;
2,4,5-TP (Silvex);
Alachlor;
Aroclor 1016;
Aroclor 1221;
Aroclor 1232;
Aroclor 1242;
Aroclor 1248;
Aroclor 1254;
Atrazine;
Benzo(a)pyrene;
Carbofuran;
Chlordane;
Dalapon;
Di(2-ethylhexyl)adipate;
Di(2-ethylhexyl)phthalate;
Dibromochloropropane;
Dinoseb;
Dioxin;
Diquat;
Endothall;
Endrin;
Ethylene Dibromide;
Glyphosate;
Heptachlor;
Heptachlor Epoxide;
Hexachlorobenzene;
Hexachlorocyclopentadiene;
Lindane;
Methoxychlor;
Oxamyl;
Pentachlorophenol;
Picloram;
Polychlorinated Biphenyls;
Simazine;
Toxaphene
36 Synthetic Organic Chemicals
Total Coliform;
Fecal Coliform
2 Total Coliform
Fecal Coliforms
1,1,1-Trichloroethane;
1,1,2-Trichloroethane;
1,1-Dichloroethylene;
1,2,4-Trichlorobenzene;
1,2-Dichloroethane;
1,2-Dichloropropane;
Benzene;
Carbon Tetrachloride;
Cis-1,2-Dichloroethylene;
Dichloromethane;
Ethylbenzene;
Monochlorobenzene;
o-Dichlorobenzene;
Para-Dichlorobenzene;
Styrene;
Tetrachloroethene;
Toluene;
Trans-1,2-Dichloroethylene;
Trichloroethene;
Vinyl Chloride;
Total Xylenes
21 Volatile Organic Chemicals

What are the Regulated Drinking Water MCLs or Alert Levels?

Haloacetic Acid (5) MCL

Sum of Monochloroacetic Acid, Dichloroacetic Acid, Trichloroacetic Acid, Monobromoacetic Acid, and Dibromoacetic Acid: 0.060 mg/L.

Compliance with the MCL is based on the annual average of the monthly averages for the previous 12 months.

Inorganic Chemical MCLs

Antimony: 0.006 mg/L
Arsenic: 0.010 mg/L (effective 1/23/06)
Asbestos: 7 MFL
Barium: 2 mg/L
Beryllium: 0.004 mg/L
Cadmium: 0.005 mg/L
Chromium: Total: 0.1 mg/L
Cyanide: 0.2 mg/L
Fluoride: 4.0 mg/L (2.0 mg/L SMCL)
Mercury: 0.002 mg/L
Nickel: None
Nitrate: 10 mg/L
Nitrite: 1 mg/L
Selenium: 0.05 mg/L
Thallium: 0.002 mg/L
Sodium: None

Compliance with the MCL is based on the running annual average.

water faucet (or tap)

Lead and Copper Alert Levels

Lead Alert Level: 15 ug/L
Copper Alert Level: 1.3 mg/L

Compliance with the Alert Level is based on the 90th percentile.

Maximum Residual Disinfection Level

Chlorine: 4.0 mg/L

Compliance with the MCL is based on the annual average of the monthly averages for the previous 12 months.

Radiochemical MCLs

Gross Alpha or Adjusted Gross Alpha Particle Activity: 15 pCi/L
Combined Radium (Radium-226 and Radium-228): 5 pCi/L
Uranium 30 ug/L

Compliance with the MCL is based on the running annual average.

Synthetic Organic Chemical MCLs

The MCLs for the 36 SOCs are listed in the SOC MCL Table.

Compliance with the MCL is based on the running annual average.

Total Coliform MCL

Compliance with the MCL is based on the presence or absence of coliforms. For a system which collects at least 40 samples per month, no more than 5% of the samples collected in a month can be total coliform-positive. For a system which collects fewer than 40 samples per month, no more than one sample collected during a month is total coliform-positive.

Fecal Coliform MCL

Any fecal coliform-positive repeat sample or E. coli-positive repeat sample, or any total coliform-positive repeat sample following a fecal coliform-positive or E. Coli-positive routine sample.

Total Trihalomethanes MCL

Sum of Bromoform Chloroform, Bromodichloromethane, and Chlorodibromomethane: 0.080 mg/L.

Compliance with the MCL is based on the annual average of the monthly averages for the previous 12 months.

Volatile Organic Chemical MCLs

The MCLS for the 21 regulated VOCs are listed in the VOC MCL Table.

Compliance with the MCL is based on the running annual average.

What are the sources of contaminants in drinking water?

The Sources of Contaminant in Drinking Water Table lists sources of contaminants in drinking water. It was derived from the EPA's Drinking Water Contaminants web page.

How often are Tucson Water sources tested to comply with the Drinking Water Regulations?

Monitoring requirements, including frequencies and locations, are specified within the drinking water regulations. In general, monitoring is required at the distribution system or at the Entry-Point-to-the-Distribution-System (EPDS).

The monitoring frequencies are dependent on the results of the previous sampling events. More frequent monitoring is implemented when a level approaches the MCL in order to make the necessary adjustments to prevent an exceedance, including shutting the well down. With ADEQ approval, a monitoring reduction is used when a contaminant is not detected over a specified time period. The Drinking Water Compliance Monitoring Table summarizes our monitoring frequencies.

How will I know if a contaminant is found in my water?

Annual Water Quality Report

Every year, Tucson Water publishes an Annual Water Quality Report for its customers. The results contained in the report are based on compliance data collected from the previous year to comply with the Drinking Water Rules.

The ADEQ also requires that Tucson Water give you public notice should our water supply violate drinking water standards. This includes information about what is being done to correct the situation.

For More Information

Contact the Water Quality Division at (520) 791-2544.