SAN LUIS OBISPO -- Morro Bay city officials have said they'd likely pursue legal action against about a dozen Morro Valley property owners -- most of them growers -- if they don't stop excessive use of nitrogen-based fertilizers suspected of tainting a key source of drinking water.
The move comes after the city hired San Luis Obispo-based Cleath and Associates to find what's contaminating drinking-water wells located just outside town.
A report with results of that study shows water in those wells -- a backup water supply for Morro Bay -- reaching nitrate levels about four times the drinking water standard.
Concerns of nitrate contamination surfaced in November 2006, when the city temporarily halted use of state water during annual maintenance and reverted to those wells for drinking water.
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When they found high levels of nitrates, they had to treat the water.
The city also uses that water during peak season, when Morro Bay's supply of state water is inadequate.
City Attorney Rob Schultz said the excess nitrates could pose a health risk not only to Morro Bay residents, but also to property owners in the Morro Valley -- an area southeast of town near Highway 41 -- who use the wells as a source of drinking water.
Nitrates inhibit the blood's ability to carry oxygen and can be harmful, especially for pregnant women, infants and people with blood diseases.
City officials last week sent letters to property owners in the Morro Valley asking that they stop using nitrogen-based fertilizer on row crops. Those fertilizers are blamed for tainting four drinking-water wells.
Schultz said he has not yet imposed a deadline for property owners to contact him.
The state's Regional Water Quality Control Board regulates local water quality standards. Still, the city could take legal action, Schultz said.
"We'll get as big of a hammer as we need," City Council Member Bill Pierce said. "This is our No. 1 fight right now."
In the meantime, Schultz said Morro Bay would work with the regional water board, the county agricultural commissioner and affected property owners to find ways to stem the nitrate pollution.
"Our goal is to stop over-application of these fertilizers," city Senior Civil Engineer Dylan Wade said. "I don't think they need to cease using them."
Chief among city officials' concerns are a trio of parcels in the lower Morro Valley believed to be using the most fertilizer.
So far, property owners that are believed to be using a majority of the fertilizer have been the least responsive to the letter, according to city officials.
However city officials said those fields -- which include nine types of vegetables and avocados -- might have been leased to tenant farmers. Because letters were mailed to property owners, the farmers who may be leasing the land have been contacted by the city.
City officials said they hope the decreased use of nitrogen-based fertilizers would flush the contaminated water out of the ground-water aquifer within the next two decades.
"We're not advocating stopping growing," Schultz said. "But we've got to come up with a plan so we don't poison the water."
One property owner in Morro Valley who received a letter from the city said he was concerned about the results of the study because he drinks water from those wells, and could prove that he doesn't use excessive fertilizer in his operation. He asked that his identity not be published because he has not responded yet to the city's letter.
Hugh Smith, a Santa Barbara farm adviser for the University of California's Division of Agriculture and Natural Resources, said asking farmers not to use nitrogen-based fertilizers is like asking them not to use water.