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9.A. - Page 10 /City 2016 Public Health Goal Report <br /> plumbing systems such as those containing lead-based solder used to join copper pipe, <br /> brass and chrome-plated brass faucets, lead pipe connections from homes to the water <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 2015 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 MCL5; 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 2015 Lead and Copper Sampling all of the samples <br /> collected were below the Action Level of 15 ppb. However, 17 of the 31 samples collected <br /> tested above the PHG for lead as shown in the figure below. <br /> 2015 Lead Tap Sampling <br /> 16.0 <br /> S 14.0 JN <br /> a 12.0 AL 15 ppb <br /> 0 10.0 — <br /> 8.0 <br /> v 6.0 <br /> 0_ <br /> L' 4.0 <br /> ro <br /> 2.0 � .2 ppb <br /> a 1 1 1 1 1 1-n 1 1 1 1 1 I <br /> 0.0 <br /> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 <br /> Results —PHG —AL <br /> 4 <br />