Summary statistics of water quality parameters in samples collected from private drinking water systems
| Target water quality constituent . | Standard . | Number of observations . | Mean . | Median . | 90th percentile . | Percent exceeding . | |
|---|---|---|---|---|---|---|---|
| aArsenic, in mg/L | MCL | 0.010 mg/L | 2,146 | BDL | BDL | BDL | 0.1% |
| bCadmium, in mg/L | 0.005 mg/L | 2,144 | BDL | BDL | BDL | 0.6% | |
| aChromium, in mg/L | 0.1 mg/L | 2,144 | BDL | BDL | 0.001 | 0.0% | |
| aFluoride, in mg/L | 4.0 mg/L | 2,146 | BDL | BDL | BDL | 0.4% | |
| aNitrate, mg/L | 10 mg/L | 2,146 | 1.5 | BDL | 4.2 | 1.3% | |
| aTotal coliforms, in cfu | ABSENT | 2,143 | – | – | – | 46% | |
| aE. coli, in cfu | ABSENT | 2,143 | – | – | – | 10% | |
| bCopper, in mg/L | Action | 1.3 mg/L | 2,144 | 0.677 | 0.153 | 1.727 | 12% |
| bLead, in mg/L | Level | 0.015 mg/L | 2,144 | 0.022 | 0.004 | 0.027 | 19% |
| bAluminum, in mg/L | SMCL | 0.05–0.2 mg/L | 2,144 | 0.047 | 0.003 | 0.061 | 3.8% (12%*) |
| aChloride, in mg/L | 250 mg/L | 1,378 | 14.3 | 5.4 | 31.4 | 0.2% | |
| aCopper, in mg/L | 1.0 mg/L | 2,144 | 0.677 | 0.153 | 1.727 | 15% | |
| aFluoride, in mg/L | 2.0 mg/L | 2,146 | BDL | BDL | BDL | 2.7% | |
| aIron, in mg/L | 0.3 mg/L | 2,146 | 0.142 | 0.008 | 0.234 | 8% | |
| aManganese, in mg/L | 0.05 mg/L | 2,146 | 0.032 | 0.002 | 0.049 | 10% | |
| apH, in standard units | 6.5–8.5 | 2,146 | 7.1 | 7.2 | 8.0 (6.0c) | 26% (23%**) | |
| bSilver, in mg/L | 0.1 mg/L | 2,144 | BDL | BDL | BDL | 0.0% | |
| aSulfate, in mg/L | 250 mg/L | 2,146 | 45.1 | 8.0 | 52.3 | 2.4% | |
| aTDS, in mg/L | 500 mg/L | 2,146 | 237.1 | 179.6 | 501.1 | 10% | |
| bZinc, in mg/L | 5 mg/L | 2,144 | 0.868 | 0.231 | 2.247 | 3.1% | |
| Target water quality constituent . | Standard . | Number of observations . | Mean . | Median . | 90th percentile . | Percent exceeding . | |
|---|---|---|---|---|---|---|---|
| aArsenic, in mg/L | MCL | 0.010 mg/L | 2,146 | BDL | BDL | BDL | 0.1% |
| bCadmium, in mg/L | 0.005 mg/L | 2,144 | BDL | BDL | BDL | 0.6% | |
| aChromium, in mg/L | 0.1 mg/L | 2,144 | BDL | BDL | 0.001 | 0.0% | |
| aFluoride, in mg/L | 4.0 mg/L | 2,146 | BDL | BDL | BDL | 0.4% | |
| aNitrate, mg/L | 10 mg/L | 2,146 | 1.5 | BDL | 4.2 | 1.3% | |
| aTotal coliforms, in cfu | ABSENT | 2,143 | – | – | – | 46% | |
| aE. coli, in cfu | ABSENT | 2,143 | – | – | – | 10% | |
| bCopper, in mg/L | Action | 1.3 mg/L | 2,144 | 0.677 | 0.153 | 1.727 | 12% |
| bLead, in mg/L | Level | 0.015 mg/L | 2,144 | 0.022 | 0.004 | 0.027 | 19% |
| bAluminum, in mg/L | SMCL | 0.05–0.2 mg/L | 2,144 | 0.047 | 0.003 | 0.061 | 3.8% (12%*) |
| aChloride, in mg/L | 250 mg/L | 1,378 | 14.3 | 5.4 | 31.4 | 0.2% | |
| aCopper, in mg/L | 1.0 mg/L | 2,144 | 0.677 | 0.153 | 1.727 | 15% | |
| aFluoride, in mg/L | 2.0 mg/L | 2,146 | BDL | BDL | BDL | 2.7% | |
| aIron, in mg/L | 0.3 mg/L | 2,146 | 0.142 | 0.008 | 0.234 | 8% | |
| aManganese, in mg/L | 0.05 mg/L | 2,146 | 0.032 | 0.002 | 0.049 | 10% | |
| apH, in standard units | 6.5–8.5 | 2,146 | 7.1 | 7.2 | 8.0 (6.0c) | 26% (23%**) | |
| bSilver, in mg/L | 0.1 mg/L | 2,144 | BDL | BDL | BDL | 0.0% | |
| aSulfate, in mg/L | 250 mg/L | 2,146 | 45.1 | 8.0 | 52.3 | 2.4% | |
| aTDS, in mg/L | 500 mg/L | 2,146 | 237.1 | 179.6 | 501.1 | 10% | |
| bZinc, in mg/L | 5 mg/L | 2,144 | 0.868 | 0.231 | 2.247 | 3.1% | |
MCL: Maximum Contaminant Level – associated with risk to human health; SMCL: Secondary Maximum Contaminant Level – associated with aesthetic considerations; BDL: below detection limit; cfu: colony forming units.
aTotal concentration measured in the flushed sample.
bTotal concentration measured in the first draw.
c10th percentile.
*Percent above 0.05 mg/L.
**Percent below pH of 6.5.