(2) Samples collected will be prorated on a weekly basis at the selected
sampling points. As an example, at a small installation, eight sampling points will be
selected and a sample taken at each two points per week. Thus, in the course of four
weeks, the eight sampling points will be progressively covered. Only samples of water
distributed for drinking and culinary purposes should be used in the evaluation of
potabiIity. Daily samples collected following an unsatisfactory sample should be
considered special samples and should not be included in totaling the number of
samples examined monthly.
b. New Coliform Rule (For Garrison and Field Testing).
(1) Based upon 40 CFR Parts 141 and 142 dated 99 June 1989, the--- and
effective 31 December 1990, the maximum contamination level goal for coliform
colonies is zero. Compliance for the maximum contamination level (MCL) of potable
water is based on the presence/absence of total coliforms in the sample, rather than on
an estimation of the coliform density.
The division surgeon in the field and the preventive medicine officer in
garrison may want you to also perform colony testing of water.
(2) When a sample test is positive for total coliforms, then within 24 hours,
collect at least one repeat sample from the same tap where the original sample was
taken; and, automatically test for fecal coliform or E. coli. If fecal coliform is present, the
installation's official public relations representative must notify the public of this problem.
Repeat testing is to continue until negative result sampling is maintained.
c. Old Coliform Rule.
(1) Prior to 31 December 1990, the multiple-filter technique (MFT) standard
for the monthly average density of all samples examined was not to exceed one per
100 ml. The number of coliform colonies in an individual sample may exceed this
average but must not exceed:
(a) One coliform colony per 100 ml average of all monthly samples, or
(b) Four coliform colonies per 100 ml in more than one sample if less
than 20 samples are collected per month, or
(c) Four coliform colonies per 100 ml for than 5 percent of the samples
if more than 20 samples are collected per month.
(2) When a single standard sample shows more than four coliform colonies
per 100 ml, daily samples from the same sampling point must be collected and
examined until the results obtained from at least two consecutive samples show less
than one coliform per 100 ml. As an example of the application of these standards, an