Samples of water were collected from Lake Herrick and Parvo Pond and brought to the lab for E. coli analysis. The membrane filtration method was used to filter the samples and incubate the filters to count purple E. coli colonies. On average, E. coli levels were below the EPA limit, but spikes occurred during rainy events when runoff introduced more contaminants. Levels tended to be higher closer to sources of input like Parvo Pond and storm drains. The sources of contamination include wildlife, pets, stormwater runoff, and surrounding urban areas.

1. Samples collected and brought back to lab for analysis.
Prepared mTec plates are labeled with date and site
Membrane filtration system is set up
• Sterile filter is placed over suction funnel.
• Starting with the lowest volume samples are filtered through the
membrane to collect the bacteria
Filter is placed on mTec plate and allowed to incubate for 2 hours at
35ᵒC then 44.5ᵒC for 24 hours.
• After 24 hours the number of purple colonies are counted, averaged,
and each dilution multiplied to get CFU/100mL
Introduction
Method
Escherichia coli levels at Lake Herrick and Parvo Pond
AJ Shockley and Keri Lydon
UGAqua Team: Mary Baxter, Chris Gowen, Aaron Moon
UGAqua, Environmental Health Science University of Georgia, Athens Georgia, 30602
Future Research
Figure 2. Levels of E. coli at Lake Herrick on dry and rainy days. Average CFU/100mL of water +/- S.D. from 3 samples at 3 sampling sites per day on the days listed.
Average E. coli levels at both the beach and bridge sites of Lake Herrick are below the EPA limit. The highest levels of E. coli were observed on 10/15/14 during a rain event. At the beach site E. coli
levels reach 1620.0 CFU/100mL nearly quadrupling the EPA limit of 410 CFU/100mL. Had samples been taken at the bridge site a spike in E. coli would have been observed. This is because during and
after rain events water flows over impervious and pervious surfaces picking up pollutants and sediments which are deposited into the waterway.
Figure 3. Levels of E. coli at Parvo Pond on dry days. Average CFU/100mL of water +/- S.D. from 3 samples from 1 sampling site per day on the days listed.
Average E. coli levels are higher at Parvo Pond than those of Lake Herrick. A spike in E. coli levels is observed at the 2nd sampling site at Parvo Pond because this area has little cover from brush
and shrubs while the 1st and 3rd are insulated by plant life reducing the amount of loose sediment and access by animals. The 1st site is the only site with levels below the EPA limit. This can be
attributed to the presence of plant cover as well as a layer of thick mud along the shoreline which traps sediments and reduces access by animals.
1. Morphis, C., McCalum, C., Keys, L., Ammons, J., Respress, J., and Tilghman, L. (2014). Restoring Lake Herrick:
Information for Improved Water Quality and Enhanced Recreational Value. Georgia: Univeristy of Georgia.
http://www.rivercenter.uga.edu/publications/pdf/lake_herrick_report_final.pdf
2. Ishii, S. and Sadowsky, M. (2008). Escherichia coli in the Environment: Implication for Water Quality and Human
Health. Minnesota: University of Minnesota. https://www.jstage.jst.go.jp/article/jsme2/23/2/23_2_101/_pdf
3. Fisher, D., Dillard, A., Usery, E., Steiner, J. and Neely, C. (2001). Water Quality in the Headwaters of the Upper
Oconee Watershed. Georgia: University of Georgia.
https://smartech.gatech.edu/bitstream/handle/1853/43796/FisherD-01.pdf
4. Little, E., Eggert, S., Wenner, D., Rasmussen, T., Conners, D., and Fisher, D. (2007). Results from Six Years of
Community-Based Volunteer Water Quality Monitoring By the Upper Oconee Watershed Network. Georgia:
University of Georgia. http://www.gwri.gatech.edu/sites/default/files/files/docs/2007/6.2.4.pdf
Works Cited
Discussion
Results
•The UGA Office of Sustainability seeks to reopen Lake Herrick for recreational use. Before this is
possible diagnostic analysis must be conducted to determine what other contaminants are present in
the lake. In the past the Upper Oconee Watershed Network has conducted tests for turbidity,
conductivity, and nutrient levels, similar tests are needed for Lake Herrick and Parvo Pond in order to
fully understand the extent of impairment in these water bodies.4
•Determine the sources on contamination in Parvo Pond and identify to what extent contaminants
present in Parvo are affecting Lake Herrick.
•Raise awareness to local community about preserving water quality by fostering a sense of
stewardship toward the Lake Herrick and Parvo Pond. Encourage picking up litter and pet droppings
along with responsible water usage.
On average Lake Herrick and Parvo Pond have relatively low E. coli levels but spike beyond
the EPA limit during rain events. Levels at the bridge site tend to by higher than those at the
beach because the bridge is closer to areas of input (Parvo Pond, nearby roadways, and
storm drains). Also the beach is nearest to an area of output which feeds into the Oconee.
Another source of contamination is wild animal and pet feces especially at Parvo Pond.
Efforts to promote water quality within the watershed include: Repairing and building of new
infrastructure and pipes as well as research and public outreach.
A special thanks to Keri Lydon organizing UGAqua and for applying for the Office of Sustainability grant which provided
funding for this project. The UGAqua members who worked on this project include: Mary Baxter, Chris Gowen and Aaron
Moon.
Acknowledgements
Lake Herrick and Parvo Pond
Lake Herrick is a 15 acre engineered recreational lake that feeds into the North Oconee River and is
located on the southern part of campus adjacent to the intramural fields. Parvo Pond is a small pond
surrounded by a dog park which feeds into Lake Herrick. Though located within a forest area both sites
are deeply influenced by surrounding urbanized areas (nearby parking lots and roadways).1
Recreational Risk and Fecal
Indicators
In the interest of preserving water
quality the EPA has established a list
of criteria known as the Recreational
Water Quality Criteria (RWQC) to
access and reduce recreational risk.
Recreational risk is the number of
people out of 1000 exposed
individuals who will become ill due
to that exposure. The RWQC lists the
allowable amounts of fecal
indicators, enterococci and E.coli, in
order to reduce recreational risk.2
These bacteria are used because
their presence in recreational waters
is indicative of fecal contamination,
a hazard to human health.
Status of Lake Herrick and Parvo Pond
Lake Herrick was originally established for recreation and research but in 2001 swimming and
boating was banned to the public and the beach area closed.1 Though levels of E.coli are below the
RWQC maximum allowable level of 410 CFU (Coliform Forming Units) per 100 mL the water is seen
as unsafe for recreational use. Parvo Pond faces similar issues but is far more impaired by algae,
organic material and other contaminants.3
Image 5. Parvo Pond during a dry day at ~9:00AM Image 6. Drainage pipe at Parvo Pond that feeds into Lake
Herrick.
Figure1. Map of the Oconee Forest Park with highlighted locations of Lake
Herrick and Parvo Pond.
Photo credit: http://warnell.forestry.uga.edu/ofp/maps.html