Public Health and Lead Sampling Protocols for Drinking Water: A Critical Review - Global Drinking Water Management and Conservation - page 224

Table 10.4 USEPA
frequency of monitoring for
lead by population size
(USEPA 2010 )

System size (no. of people
served)

First 6-month monitoring period
begins on

>50,000 January 1, 1992

3,301 50,000 July 1, 1992

-

≤ 3,300 July 1, 1993

culties associated with accurately predicting lead
levels at short time ranges prompted the EPA in 1992 to put into the regulation a
minimum stagnation time of 6 h in sampling protocols for regulatory purposes. The
6 h stagnation time was based on

In the United States, the dif

“… a ' worst case scenario ' for lead and copper

exposure e.g. in the morning after an overnight stand period ” (Lytle and Schock

2000 , p. 1).
As noted above, the Canadian Federal level guideline, which is based on a 6 h
stagnation, is also based on the EPA guidelines. However, Ontario has adopted a
30 min stagnation protocol based on the recommendation of the Ontario Drinking
Water Advisory Committee, which itself relied heavily on the EU Report, although
there was considerable evidence that 6 h stagnation time most accurately re ected

equilibrium lead concentration levels (see Lytle and Schock 2000 , Kuch and
Wagner 1983 , Schock and Gardels 1983 , Lilly and Maas 1990 ). Figure 10.1 shows
the groundbreaking work from Kuch and Wagner ( 1983 ), which shows the stag-
nation pro

le for lead in drinking water. Even at various alkalinities the equilibrium
concentration seems to be around the 6 h mark.
Lilly and Maas ( 1990 ) have shown that lead leaching is highly nonlinear and that
over 60 percent of lead leaching occurs within the

rst hour, and that up to

Fig. 10.1 Lead concentration and stagnation time (Kuch and Wagner 1983 ). Note Upper line pipe
of inch diameter, pH of 6.8 and alkalinity of 10 mg/L in CaCO 3 . Lower line pipe of 3/8 inch

diameter, pH of 7.2, and alkalinity of 213 mg/L in CaCO 3

½