San Diego

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Water Quality Reports

Image of Imported Water Sources Map

Why is There Anything in My Water?

The sources of drinking water (both tap water and bottled water)include rivers, lakes, streams, ponds, reservoirs, springs andwells. As water travels over the surface of the land or through theground, it dissolves naturally occurring minerals and, in some cases,radioactive material, and can pick up substances resulting from thepresence of animals or from human activity. Contaminants that maybe present in source water include:

  • Microbial contaminants, such as viruses and bacteriathat may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.
  • Inorganic contaminants, such as salts and metals, that can be naturally occurring or result from urban storm water runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
  • Pesticides and herbicides that may come from a varietyof sources such as agriculture, urban storm water runoff, and residential uses.
  • Organic chemical contaminants, including synthetic andvolatile organic chemicals that are by-products of industrialprocesses and petroleum production, and can also come fromgas stations, urban storm water runoff, agricultural application, and septic systems.
  • Radioactive contaminants that can be naturally occurring or be the result of oil and gas production and mining activities.
Image of Treatmant Plant Service Area Map

Your water comes from three municipal water
treatment plants - Alvarado, Miramar and Otay.
The City maintains nine reservoirs and purchases
imported water from the San Diego County Water Authority.
Water from the Colorado River Aqueduct and the State
Water Project, as well as some local runoff,
constitute the source waters for these plants.

In order to ensure that tap water is safe to drink, the U.S.Environmental Protection Agency (USEPA) and the CaliforniaDepartment of Public Health (CDPH) prescribe regulations thatlimit the amount of certain contaminants in water provided by publicwater systems. Department regulations also establish limits forcontaminants in bottled water that provide the same protectionfor public health. The 2010 Watershed Sanitary Surveycontains information on the City's watersheds.

Our Imported Water Supply and the Impact on Water Quality

The City of San Diego imports an average of 85 percentof its water. This imported water is provided by theSan Diego County Water Authority, which purchaseswater from the Metropolitan Water District of SouthernCalifornia. Ultimately, our imported water is a blend ofColorado River water and State Water Project water(see map). Throughout the year, the blend changes.

Several forces negatively impact the quality of waterfrom the Colorado River and State Water Project.The Colorado River winds through thousands of milesof unprotected watershed containing towns, farms,old mining sites and industrial sites.

Water from the State Water Project is also subject topotential contaminants such as pesticides and herbicides.This water source also has a higher organic carbon andbromide level than the Colorado River water. As organiccarbon and bromide levels increase, the potential forcreating higher levels of disinfection by-products exists.(The disinfectants used to treat water can react withnaturally occurring materials in the water to form unintendedby-products which may pose health risks). The City continuallyalters its treatment process to adjust for changing water supplies.

The City of San Diego regularly monitors the quality of ourwater to ensure all drinking water quality standards are met.

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