From Jean Shekterx '
To! Kpmll77@a0l..com; Kristen Philip; Pat Cook; Richard Benzie

Date: 10/6/2004 10:13:00 AM
Subject: Re: Maximum residence time
Summaxy

The EPA does not give specific guidance on standing times, but mentions it
in the preamble of the 1991 rule and in their 1991 guidancs manual. The PREAMBLE
discusses a proposed 8-18 hour standing time and the controversy surrounding the
8 hours. The EPA settled on 6 hours, but did not discuss the upper limit further,.

The GUIDANCE MANUAL states that water use during the previous day should be typical
of daily use when occupied. It also mentions 12 hours as excessively long in
a parenthetical statement. Details below,

Datails '
Preamble: The preamble of the original lead and copper rule {56 FR 26460
dated June 7, 1991) states, “The 1988 proposal would have required systems to
collect ...sample at a consumer’s tap that has been standing in the interior plumbing
for 8 to 18 hours and was collected without prior flushing” (page 26518, column
3, under 2. Sample Collection). However, “numerous commenters were critical of
the 8 to 18 hour standing time regquirement” (page 26520, column 1 under ii. Standing
Time). The EPA responded with reducing the minimmm standing time to 6 hours,
but no longer addressed the maximom standing time. Later in the preamble, under
the public notification and system reporting and recoxdkeeping requirements
section, the EPA notes that the final rule settled on requiring systems to cexrtify
that the first draw sample stood motionless for least 6 hours with no further
mention of the 18 hours {(page 26531, column 1, undex a, Tap Monitoring.)

Guidance Manual: The EPA mentions excessive standing times in thelr guidance
manual., “First Draw Tap Samples: Samples can be collected any time as long as
the water has stood undisturbed in the pipes for at least 6 hours. Water use
during the day before sample collection should have been typical of its daily
use when occupied. PWSs should redquest home owners to indicate when water had
last been used in the house prior.to sampling and the time that the sample was
collected. Estimating the stagnation period may assist PWSs in data
interpretation, especially when excessively long stagnation periods are
encountered (more than 12 hours).” There is no further mention of excessively
long stagnation periocd (page 4-14 of the Lead and Coppexr Rule Guidance Manual,
Volume I: Monitoring, dated September 1991, Drinking Water Technology Branch,
Drinking. Water Standards Division, Office of Ground Water and Drinking Water.)

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