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7.113. - Page 10 of 15 <br />City of Redwood City <br />2019 Public Health Goal Report <br />main, brass/bronze water meters, brass/bronze curb valves, and brass/bronze corporation <br />valves can all contribute to lead leaching <br />Although the City of Redwood City's water sources are free of lead, several of the homes <br />that participated in Redwood City's 2018 Lead and Copper Sampling had lead levels that <br />exceeded the PHG of 0.2 ppb. Results from the lead and copper sampling represent the <br />worst case conditions for lead levels in the distribution system. These samples are collected <br />under a first -draw condition; which means that water must sit in the customer's piping for 6 <br />hours before it is collected. Furthermore, the samples were taken from homes that are <br />considered to be the highest risk locations. <br />Many of the samples collected during the lead and copper sampling tested below the PHG <br />for lead, and lead levels at the sampled locations may be higher than others because of the <br />plumbing material used when these homes were built. The probable reason for the <br />difference in lead concentration at the individual residences can be attributed to the <br />plumbing components at these residences. It may be that some plumbing components at <br />locations with lower levels of lead detected have been replaced with new "low -lead" <br />fixtures. Additionally, beginning January 2010 in California all plumbing fixtures sold and <br />installed for use in a plumbing system intended to convey drinking water are required to be <br />lead free (as required by CA Health & Safety Code 116875). <br />Values referred to as MCLS for lead are not actually MCLs; instead, they are called "Action <br />Levels" as prescribed in Chapter 17.5 of Title 22, California Health and Safety Code. An MCL <br />for lead is considered to be exceeded when 10% of the samples collected are above the <br />action level. During Redwood City's 2018 Lead and Copper Sampling all of the samples <br />collected were below the Action Level of 15 ppb. However, 16 of the 33 samples collected <br />tested above the PHG for lead as shown in the figure below. <br />2018 Lead Sampling <br />16 <br />14 AL 15 ppb <br />12 <br />10 <br />8 <br />6 <br />4 <br />2 PHG 0.2 ppb <br />0 <br />1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 23 24 25 26 27 28 29 30 3132 33 <br />� Pb Results PHG AL <br />0 <br />323 <br />