Well Contamination

Contact: Joan Pelley, Public Information, (360) 738-6247

Mary O'Herron, Toxics Cleanup Specialist, (360) 738-6250

Half of wells tested fail drinking water standards

In nine households, the agricultural pesticides ethylene dibromide (EDB) or dichloropropane (DCP) are present in amounts beyond what is allowed in drinking water. Caution is warranted for an additional 21 homes where one or both pesticides are present, but not in amounts that exceed drinking water limits. The drinking water limit, or "standard," for EDB is 0.05 parts per billion (ppb). The drinking water standard for DCP is 5 ppb.

High nitrate levels-of particular concern for infants and people with weakened immune systems-exceed drinking water limits in samples from 21 homes. The limit of nitrates allowable in drinking water is 10 parts per million (ppm). Nitrates were detected in another 31 homes, but below 10 ppm.

"Our first priority is to provide the initial results to residents," said Richard Grout, manager of Ecology's Bellingham Field Office. Grout said people were notified in July when fecal coliform was found in about two-thirds of the samples. Lab analysis for pesticides and nitrates required more time, so letters describing those results were mailed to residents Tuesday. Additional analytical results will be provided as they become available.

In June Ecology sampled drinking water in the area where historic data indicate well contamination was most prevalent-within a 1.5-mile radius of the intersection of Bob Hall and Birch Bay-Lynden roads. Additional sampling in September will occur at homes located beyond the June sample group, encompassing a 7-square-mile area that was designated a toxic cleanup site in the late 1980s.

Households with EDB or DCP-tainted wells within the 7-square-mile "site" are eligible to receive bottled water for drinking, cooking and teeth-brushing under Ecology's toxic-cleanup program.

However, Grout said, nitrate problems in wells are more often the result of agricultural fertilizers - including manure - and failing septic systems leaching into shallow aquifers underlying agricultural lands.

"The cleanup law doesn't cover that type of pollution because it's considered to be more of a local land-use issue," Grout said. "But households concerned about nitrates can order bottled water on their own, or explore treatment options if nitrates are their only contamination problem."

Grout said that current sampling results, along with historic well data and information about household water use, will help scientists better determine individual health risks and whether:

• overall contamination levels are increasing or decreasing;
• the original contaminant "plume" has moved;
• there is a correlation between contaminants and well depth or between types of contaminants; and
• whether other patterns emerge according to numerous variables.

Grout said that a comparison of water supply alternatives will be completed within a month, evaluating the economic, legal, hydrologic and engineering feasibility of available options.