Hundreds of SLO County residents warned to not drink tap water due to pollution
Hundreds of residents in southern San Luis Obispo County have been told to not drink their tap water due to potentially unhealthy levels of nitrates that have contaminated the groundwater, according to a notice sent to residents.
Woodland Park Mutual Water Co., which serves roughly 160 hookups that supply water to about 540 people on the Nipomo Mesa, sent the notice on April 21.
The business is different from Woodlands Mutual Water Co., which also serves residents on the Nipomo Mesa. That company’s water has not been found to be contaminated with nitrates.
Woodland Park Mutual Water Co. warned residents that levels of nitrates above the maximum contaminant level were found in the groundwater that feeds into their tap water.
Nitrates are a naturally occurring nitrogen compound that is needed by plants and animals to live and grow.
They can be found in fertilizers for crops to boost productivity, and can also be used as a food preservative, in some pharmaceutical drugs and in the production of munitions and explosives, according to the U.S. Agency for Toxic Substances and Disease Registry.
Too many nitrates, or a detection above the maximum contaminant level, can be harmful to humans if consumed. This is especially true for infants under 6 months of age, the federal agency said.
What amount of nitrates was found in the water?
On April 14, Woodland Park Mutual Water Co. detected 12 milligrams per liter of nitrates in its groundwater. The company then retested the groundwater on April 19 and found 10 milligrams per liter of nitrates.
The maximum contaminant level of nitrates in drinking water is 10 milligrams per liter. Anything below that level is considered safe to consume.
The San Luis Obispo County Public Health Department, following standard procedures, averaged the two samples to come out at 11 milligrams per liter of nitrates.
Because that was 1 milligram per liter over the maximum contaminant level, residents had to be warned that excessive levels of nitrates had been found in their drinking water.
Can I drink my tap water?
The Public Health Department and Woodland Park Mutual Water Co. have advised more than 150 households to not drink the water.
“We would advise residents who do not have water treatment at their home to use bottled water for drinking and cooking until they are notified that the nitrate level has returned to a safe range,” Public Health spokesperson Tara Kennon told The Tribune via email. “We have recommended the system provide bottled water to residents who need it; however this is not a requirement in code.”
It is safe for residents to shower, wash dishes, water plants and wash clothes in the water, Kennon noted. Nitrates can only be absorbed into the human body through drinking or eating.
Residents are advised to not boil the water, as this does not help reduce the level of nitrates.
Adverse affects of high levels of nitrates in drinking water have been found to occur in infants, who experienced methemoglobinemia, or the decreased ability of the blood to carry oxygen to tissues, according to the Agency for Toxic Substances and Disease Registry.
That’s why it is important that babies and pregnant women not drink the water.
When will water be safe again?
Woodland Park Mutual Water Co. is set to retest the water in May, according to Kennon.
Should it find that fewer than 10 milligrams per liter of nitrates in the groundwater, the company should notify customers the water is safe again to drink.
If the nitrate level remains too high, then the San Luis Obispo County Environmental Health Department “will take additional enforcement action, such as issuing a compliance order to require further action on the part of the water system,” Kennon wrote in her email.
Such further action could include drilling a new well or installing treatment, she added.
At this time, the source of the nitrate contamination is unknown, Kennon wrote.
This story was originally published April 27, 2023 at 12:03 PM.
