Monday, August 27, 2018

Where does the Lead in Wells Come From

In 2012, the Macon County Health Department in North Carolina discovered county-wide water lead contamination in private wells due, they reported, to corrosion of galvanized well components. In North Carolina current well construction code requires the installation of a tap on the well; thus, they were able to differentiate lead contamination originating from household plumbing and lead contamination originating from the well.

They found "first draw samples" collected at the wellhead between 2008 and 2012 documented that 55 of 398 (14%) of newly constructed wells exceeded the U.S. Environmental Protection Agency Lead and Copper Rule action level for lead of 15 μg/L. However, there is no safe level of lead exposure, as even low water lead levels-those less than 5 μg/L- can increase a child's blood lead level. In the Macon County Health Department samples they found water with lead concentrations as high as 191 μg/L.

North Carolina like most of the eastern seaboard states has areas at high risk for corrosive water. During periods of stagnation, in water that is corrosive (with a pH less than 6) a chemical redox reaction occurs that dissolves and leaches lead into the water. Lead present in well and plumbing components is leached into the water. This lead comes from brass fittings and galvanized pipe (which has a lead- zinc coating), and plumbing components produced before 2014 when "lead-free" fixtures could have up to 8% lead. In Virginia, the Blue Ridge, Piedmont and shallow wells in the Coastal Plain have a high risk for corrosive water and lead contamination in their water.

Civil and Environment Engineering Department at Virginia Tech and the Environmental Health Services Branch of the Macon County Public Health Department and lead by Kelsey J. Pieper PhD USDA-NIFA Postdoctoral Fellow at Virginia Tech investigated lead in well water concentrations at the homes of 15 private wells in Macon County found to have elevated levels of lead in their wellhead samples. There was another part of the research but we will not discuss that here.

 Low pH water can corrode metal plumbing fixtures causing lead and copper to leach into the water and causing pitting and leaks in the plumbing system. The presence of lead in pipes and fixtures becomes a bigger problem with water with a pH less than 6. In the past lead was used to solder copper pipes together before 1988 when the 1986 ban on lead in paint and solder went into effect. Also, until 2014 when the 2011 Reduction of Lead in Drinking Water Act went into effect, almost all drinking water fixtures were made from brass containing up to 8% lead, even if they carried a plated veneer of chrome, nickel or brushed aluminum and were sold as "lead free." So even home built with PVC piping in the 2000's may have some lead in most of the faucets.

The pattern of lead release and remediation for lead contamination originating from plumbing have been extensively studied. The goal for the Virginia Tech and the Macon County Public Health Department study was to identify patterns of lead leaching/ release within the well itself. Plumbing components used within a private well are not subject to the 1986 Lead Ban or the 2011 Reduction of Lead in Drinking water Act requirements. Galvanized iron is still commonly used for well casings and fittings and drop pipes in well deeper than 600 feet. Before 2014 Prime Western grade “lead free” galvanized steel zinc coating was required to contain between 0.5%-1.4% lead. After 2014, “lead free” galvanized steel have less than 0.25% lead in the surface coatings. Nonetheless, under corrosive conditions, any lead used in coatings can be easily released to the water and pumped to the household tap or accumulate in scale layers on the pipe surface or well bottom where scale can accumulate and be released or picked up and pumped with the water.

Water lead concentration patterns and sources of contamination within the wells differed among the 15 private wells as can be seen in the diagrams below which come from Environmental Science and Technology article cited below. The scientists found that elevated lead was associated with three sources of lead release: (1) dissolution of lead from well plumbing during periods of stagnation; (2) scouring of leaded scales and sediments along the well plumbing infrastructure during initial water use; and (3) mobilization of leaded scales during continued water use.

From Pieper et al.

As you can see, water lead levels measured during well testing show that in (A) nine wells had no water lead during continued water use however, (B) six wells showed sporadic spikes in particulate lead during continued water use. The detection limit of lead in the analysis was 1 μg/L. Lead contamination in a well can come from three potential sources; galvanized iron well casings, galvanized iron and brass well components, and leaded scales and sediment which have formed over time.

Corrosive water is the primary risk for lead in well water. However, over time water with a neutral pH could dissolve the coating on galvanized iron and in brass well components. The well completion reports do not document materials used for well components in Virginia or anywhere else to my knowledge. Once installed a well casing cannot be removed. It is possible to line the casing with a plastic pipe a technique used to seal a well where the grouting has failed. All the other components of the well can be replaced, though excavation would be required to replace the exterior portions of the pitless adaptor. However, scale that has accumulated on the bottom of the well might remain a source of lead if it is not mechanically removed. Further research needs to be done to further characterize the lead in well and effective remediation techniques.

To read the complete article:

Elevated Lead in Water of Private Wells Poses Health Risks: Case Study in Macon County, North Carolina

Kelsey J. Pieper, Victoria E. Nystrom, Jeffrey Parks, Kyle Jennings, Harold Faircloth, Jane B. Morgan, Jim Bruckner, and Marc A. Edwards Environmental Science & Technology 2018 52 (7), 4350-4357 DOI: 10.1021/acs.est.7b05812 

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