Environmental Engineering Reference
In-Depth Information
practical and when analyzed jointly can produce in most cases better results than any
single sampling protocol can. The EU report shows that the 30MS protocol under-
estimates COMP by 20 percent; RDT overestimates by 27 percent, and FF under-
estimates COMP by 43 percent. It should also be noted that the COMP sample is not a
reliable measure of lead as it is the average intake of lead per week but not the
maximum possible intake. If the criterion is to avoid the highest social cost of lead,
then the COMP sample is also inadequate. From the health point of view, what
matters most is the maximum exposure and not the average exposure.
Finally, it should be noted that Danish legislation requires the use of 12 h
stagnation. Germany uses 4 h stagnation because that time protects 95 percent of
their consumers. Four hours stagnation covers about 80 percent of the maximum
saturation concentration of the stagnation curve, while a 30MS covers only
30
40 percent. RDT and the 30MS underestimate the real exposure to lead by 44
and 56 percent, respectively (Hoekstra et al. 2004 ). This later research, which is
also a EU research publication, clearly shows that the 30MS sampling method is
completely inappropriate and simply wrong.
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10.5 The EPA Sampling Protocol
The guidelines for monitoring requirements for lead in the USA can be found under
the US Code of Federal Regulations, Title 40
Protection of the Environment,
Chapter 1 Sub chapter D (Water programs) sub part I. Under this EPA guideline, for
a residential property, a 1 L sample should be collected at the plumbing system in
either the kitchen or sink tap after a stagnation time of at least 6 h (nonresidential
buildings are required to obtain samples from a tap that is normally used for water
consumption). Lead service line samples are collected either (1) at the tap after
flushing the volume of water between the tap and lead service line, (2) by accessing
the lead service line directly, or (3) by collecting a sample after allowing water to
run until a signi
cant change in temperature is felt. The calculation for the volume
of water in (1) is based on the interior diameter and length of pipe.
The number of monitoring sites is the same as that which is presented in
Table 10.2 for the Canadian Federal guidelines (Canadian Federal guidelines have
adopted many of the EPA measures). The EPA also distinguishes between the sizes
of water distribution systems. A medium system serves between 3,300 and 50,000
(inclusive) people while small and large systems can be described as those that
serve fewer than 3,300 and more than 50,000 people respectively. Table 10.4 shows
the frequency with which each system should be monitored. Each sized system is
required to monitor fully for two consecutive 6-month periods unless (1) no more
than 10 percent of samples are above 15
g/L for 2 consecutive periods after which
they may reduce their monitoring load (e.g. reducing number of samples) or (2)
they meet their MCL criteria after initially failing to meet the MCL level, imple-
menting new corrosion control methods as described in the Federal guidelines and
retesting problem properties.
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