E. coli Contamination in the Headwaters of Plaster Creek
Andre Otte, Calvin College
Introduction
Plaster creek is one of the most polluted
creeks in Michigan. Much of the pollution is
due to storm water runoff from agricultural
land in the headwaters. One of the pollutants
that rainwater carries off the fields and into
the creek is E. coli bacteria, which is found in
the gut of mammals. Most strains of E. coli
are not harmful to humans, but they are a
good indicator of fecal contamination in
water. High levels of E. coli in Plaster Creek
are a human health concern.
Conclusions
Petri dish with a three-sample mean 5,147 cfu/100mL.
This particular sample was taken from a location were
cows frequently cross Plaster Creek. This is the reason for
the large variation.
Objectives
•  Take water samples from the headwaters
of Plaster Creek and its tributaries over
the course of the summer to get a picture
of the scale of contamination.
•  Explore possible sources of
contamination.
Methods
Samples were taken from Plaster Creek using
10mL pipettes. Three samples were taken from
each location, and data points were reported as
a mean of the three replicates. Clean pipettes
were used for each location. Samples were put
on ice within 1.5 hours and incubated at 37°C
within 4 hours. The medium used was Coliscan
Easygel. Bacterial colonies were counted 22-25
hours after incubation.
While walking through the creek, I saw many
interesting things that could be leading to the E.
coli contamination of the creek:
•  Many of the farms that line Plaster Creek
have direct drain hookups to the creek. If the
fields are fertilized with manure, or if
bacteria are colonizing in drain tiles, E. coli
will be washed into Plaster Creek during
storms.
•  On more than one occasion I saw cows in
Plaster Creek. I recorded a three-sample
mean of 14,578 cfu/100mL twenty-five
meters downstream of nearly twenty cows on
one of these occasions. At least one other
location, which was very near to Shadyside
Park, showed signs of cows entering the
creek. One sample from this location
contained 3,680 cfu/100mL.
•  I suspect a leaking septic tank draining into
one of Plaster Creek’s southernmost
tributaries. My highest three-sample mean
(16000 cfu/100mL) came from water falling
directly from a drainage pipe, which seemed
to come from a backyard.
Even though the large majority of Plaster
Creek’s headwaters are unsafe for full body
contact, I sampled several areas that seemed to
be very healthy. One tributary crossing near
East Paris and 60th St. had nearly no E. coli. I
saw blue gill and crayfish and even found an
endangered species of mollusk in the creek. It is
areas such as this that offer a glimpse of the
diversity that Plaster Creek can sustain.
In order for E. coli contamination in the
headwaters of Plaster Creek to be diminished,
the creek must be considered a home to
diversity and a potential resource instead of as a
drain. Compromise about appropriate uses of
Plaster Creek will need to occur between the
farmers living in this area and those working
towards restoration.
Example sampling map. Dots represent locations of set of
three samples.
Results
Cows cooling off (and pooping) in the creek.
Of the 78 three sample means, 30 were above
the EPA limit for safe partial body contact
(1000 colonies/100mL water) on the date of
sampling. 19 three-sample means were
considered safe levels for full body contact (300
colonies/100mL) and 29 were within the
appropriate limits for partial body contact on the
date of sampling.
Map of northern sampling area. Dots represent locations that
were unsafe for partial body contact on the sampling date.
References
Drainage tile from field directly into creek.
Michigan DEQ. Total Maximum Daily Load for E. coli for
The Grand River Kent County. 2006.