Water Quality Data
Detected Unregulated Parameters Requiring Monitoring
The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years EPA issue a new list of no more than 30 unregulated contaminants to be monitored by public water systems. This monitoring provides a basis for future regulatory actions to protect public health. The Unregulated Contaminant Monitoring Rule (UCMR) program was developed in coordination with the Contaminant Candidate List (CCL). The CCL is a list of contaminants that are not regulated by the National Primary Drinking Water Regulations, are known or anticipated to occur at public water systems and may warrant regulation under the Safe Drinking Water Act.
Under the current cycle of the Unregulated Contaminant Monitoring Rule (UCMR 3) chemicals are being studied at levels that are often significantly below those in prior UCMR cycles. Importantly, UCMR 3 minimum reporting levels (MRLs) were established based on the capacity of the analytical method, not based on a level established as "significant" or "harmful". In fact, the UCMR 3 MRLs are often below current "health reference levels" (to the extent that HRLs have been established).
Results of UCMR3 measurements should be interpreted accordingly. The detection of a UCMR 3 analyte above the MRL does not represent cause for concern, in and of itself. Rather, the implications of the detection should be judged considering health effects information (which is often still under development or being refined for unregulated contaminants).
San Diego's treated drinking water was tested by an EPA-approved contract laboratory in the last two quarters of 2013 for 28 unregulated contaminants. Of these 28 parameters, the six listed in the "UCMR3 PARAMETERS" section of this table were detected. It's important to note that the UCMR monitoring occurs to compile a database used to help guide future regulations. The MRLs set for the UCMR studies are based on the capacity of the analytical method, not on any level established as significant or harmful. For example, Chromium-6 was detected at levels in the range from <0.03 ppb to 0.17 ppb. CDPH recently proposed an MCL for Chromium-6 of 10 ppb. The levels detected in San Diego's water are roughly 100 times less than this proposed MCL.
| UNITS | NOTIFICATION LEVEL | CDPH DLR | CITY OF SAN DIEGO TREATMENT PLANTS |
MWD SKINNER TREATMENT PLANT |
MAJOR SOURCES IN DRINKING WATER |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ALVARADO | MIRAMAR | OTAY | ||||||||||
| AVERAGE | RANGE | AVERAGE | RANGE | AVERAGE | RANGE | AVERAGE | RANGE | |||||
| Boron | ppm | 1 | 0.1 | ND | ND - 0.12 | 0.11 | 0.11 - 0.12 | 0.12 | 0.12 - 0.13 | 0.12 | 0.12 |
Runoff/leaching from natural deposits; industrial wastes |
| UCMR3 PARAMETERS | UNITS | UCMR3 MRL | CITY OF SAN DIEGO TREATMENT PLANTS |
CITY OF SAN DIEGO DISTRIBUTION SYSTEM |
MAJOR SOURCES IN DRINKING WATER | |||||||
| ALVARADO | MIRAMAR | OTAY | ||||||||||
| AVERAGE | RANGE | AVERAGE | RANGE | AVERAGE | RANGE | AVERAGE | RANGE | |||||
| Bromochloromethane | ppb | ---- | 0.06 | ND | ND - ND | ND | ND - ND | ND | ND - 0.07 | NA | NA | Fire extinguishers; pesticide solvent |
| Chlorate | ppb | 800 | 20 | ND | ND - ND | ND | ND - 25 | 170 | 140 - 200 | 92 | 39 - 160 |
By-product of drinking water disinfection |
| Chromium-6 | ppb | ---- | 0.03 | 0.10 | 0.09 - 0.11 | 0.10 | 0.03 - 0.17 | 0.045 | ND - 0.09 | 0.062 | ND - 0.11 |
Naturally occurring metal;steel; chrome plating |
| Molybdenum | ppb | ---- | 1 | 3.3 | 3.2 - 3.4 | 3.7 | 3.4 - 3.9 | 3.1 | 2.8 - 3.3 | 3.5 | 2.7 - 3.7 |
Naturally occurring element; in ores and plants |
| Strontium | ppb | ---- | 0.3 | 555 | 550 - 560 | 770 | 750 - 790 | 585 | 510 - 660 | 718 | 490 - 800 | Naturally occurring element |
| Vanadium | ppb | 50 | 0.2 | ND | ND - 0.25 | 0.21 | 0.21 - 0.21 | ND | ND - ND | 0.34 | ND - 0.84 |
Naturally occurring metal; used as a catalyst |