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Quality Data Stanford University's Annual Water Quality Data for 2005 (1)

DETECTED CONTAMINANTS CONSTITUENTS WITH PRIMARY Unit MCL PHG or Range or Average or Typical Sources in Drinking STANDARDS (MCLG) Result (Maximum) Water (2) Unfiltered Hetch Hetchy Water, max 5 NTU - TT NS 0.25 - 1.00 (3) (1.74) (4) Soil run-off Filtered Water - Sunol Valley WTP, max 1 NTU - TT NS NA (0.27) Soil run-off 95 percentage of time < 0.3 NTU - TT NS 100% (5) NA Soil run-off ORGANIC CHEMICALS (6) DISINFECTION BY-PRODUCTS Total (TTHMs) ppb 80 NS 11 - 71 (38) (7) By-product of chlorination Total Haloacetic Acids (HAAs) ppb 60 NS 6 - 47 (24) (7) By-product of drinking water chlorination Total Organic Carbon (TOC) (8) ppm NS NS 0.9 - 3.0 2.3 Various natural and man-made sources DISINFECTION BY-PRODUCTS (Stanford Samples) Total Trihalomethanes (TTHMs) ppb 80 NS 23.3 - 50.3 (35.8) (7) By-product of drinking water chlorination Total Haloacetic Acids (HAAs) ppb 60 NS 14.0 - 33.0 (22.4) (7) By-product of drinking water chlorination MICROBIOLOGICAL (Stanford Samples) Total Coliform % <5 (0) 0 (0) Naturally present in the environment percentage of positives detected in any month INORGANIC CHEMICALS Aluminum ppb 1000 600 6 - 70 38 Erosion of natural deposits Fluoride (9) ppm 2.0 1.0 <0.1 - 1.25 1.0 Erosion of natural deposits Total (Stanford Samples) ppm MRDL=4 MRDLG=4 1.7 - 2.7 (2.2) (7) Water added for treatment

CONSTITUENTS WITH SECONDARY Unit SMCL PHG Range Average Typical Sources in Drinking Water STANDARDS ppm 500 NS <3 - 25 9 Runoff / leaching from natural deposits Color unit 15 NS <5 - 25 (10) 12 Naturally occurring organic materials Specific Conductance µS/cm 1600 NS 25 - 435 155 Substances that form ions when in water Sulfate ppm 500 NS 1 - 42 19 Runoff/leaching from natural deposits ppm 1000 NS 20 - 210 116 Runoff / leaching from natural deposits Turbidity NTU 5 NS 0.09 - 0.49 0.24 Soil runoff

LEAD AND COPPER RULE STUDY Unit AL PHG Range 90th Typical Sources in Drinking Water (10) (Stanford Samples) Percentile Copper (51 samples collected) ppb 1300 170 <10 - 120 40 (11) Corrosion of household plumbing systems Lead (51 samples collected) ppb 15 2 <2.0 - 3.0 <2.0 (12) Corrosion of household plumbing systems

OTHER WATER QUALITY Unit NL Range Average Key: PARAMETERS

(1) All results met State and Federal drinking water regulations. Sampling performed by SFPUC, unless otherwise specified. (2) Turbidity is the water clarity indicator; it also indicates the quality of the water and the treatment system efficiency. (3) Results are based on monthly average measured at Tesla Portal. (4) Turbidity is measured every four hours. This is a maximum single measurement result. (5) This is the minimum percentage of time that the filtered water turbidity is less than 0.3 NTU. (6) DHS has approved SFPUC's request for a waiver of 35 additional synthetic organic chemicals. (7) This is the highest quarterly running annual average value. (8) TOC is a precursor for disinfection by-product formation. Data are obtained from effluent monitoring at Sunol Valley Plant. (9) Data includes both Stanford University and SFPUC data points. Please see information on page 6 regarding fluoridation. (10) The 90th percentile levels of lead and copper must not be greater than the action levels. (11) In 2004, no residences were over the copper Action Level at consumer taps. Customer tap sampling is required again in 2007. (12) In 2004, no residences were over the lead Action Level at consumer taps. Customer tap sampling is required again in 2007.

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