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3. What are the maximum allowed levels for constituents in drinking water? Health agencies have maximum contaminant levels (MCL) for constituents so that drinking water is safe and looks, tastes and smells good. A few constituents have the letters "TT" (Treatment Technique) in the MCL column because they do not have a numerical MCL. Instead, they have certain treatment requirements that have to be met. One of the constituents, total chlorine residual, has an MRDL (maximum residual disinfection level) instead of an MCL. The MRDL is the maximum level of disinfectant added for water treatment that is allowed in water. While disinfectants are necessary to kill harmful microbes, drinking water regulations protect against too much disinfectant being added. Another constituent, turbidity, has a requirement that 95 percent of the measurements taken must be below a certain number. Turbidity is a measure of the cloudiness of the water. We monitor it because it is a good indicator of the efficiency of the filtration system. 4. Why are some of the constituents listed in the section labeled "Primary Standards" and others in the "Secondary Standards "? Constituents that are grouped in the primary standards section may be unhealthy at certain levels. Constituents that are grouped under the secondary standards section can affect the appearance, taste and smell of water, but do not affect the safety of the water unless they also have a primary standard. Some constituents (e.g., aluminum) have two different MCLs, one for health - related impacts, and another for non - health - related impacts. 5. How do 1 know how much of a constituent is in We use water testing equipment so sensitive it can detect levels as low as 1 part per trillion 7 i z � t � o d > k f pa IIi F t Q q4l rr, That's equivelent to I drop of soap In enough dishwaterto fill4 {,—.' SantadAna V , my water and If it is at a safe level? ; water Tanks With a few exceptions, if the average amount of a constituent found in tap water over the course of a year is no greater than the MCL, then the regulatory requirements are considered to be satisfied. The highest and lowest levels measured over a year are shown in the range. Requirements for safety, appearance, taste and smell are based on the average levels recorded and not the range. 6. How do constituents get into our water? Drinking water (tap water and bottled water) comes from 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 human activity. The most likely source for each constituent is listed in the last column of the table. 7. Are there any potential sources of contamination in our system? An assessment of the drinking water wells for the City of Santa Ana was completed in December 2014, Santa Ana's wells are considered most vulnerable to the following activities associated with contaminants detected in the water supply: historic agricultural activities, golf courses, and application of fertilizers. Our wells are considered most vulnerable to the following activities not associated with detected contaminates: chemical/ petroleum pipelines, chemical /petroleum processing /stores, dry cleaners, gas stations, junk /scrap /salvage yards, metal plating /finishing /fabrication, plastics /synthetics producers, and sewer collection systems. I SANTA ANA WATER QUALITY REPORT EXHIBIT 5 75C -46