Preliminary Florida Results

Preliminary results from well water testing after Hurricane Irma

Since October 5, 2017, Virginia Tech and University of Florida Institute of Food and Agricultural Sciences (IFAS) Extension have been coordinating citizen science sampling efforts in flood-impacted counties in Florida. Our team has distributed 376 sampling kits in Florida, which contained one sterile bottle, sampling instructions, and a well owner survey. We hosted 6 free, confidential well water testing opportunities that were promoted through the UF/IFAS Extension network. To date, our team has analyzed 179 well water samples from 10 counties in Florida.

The preliminary county-level data provided below describe all the well water samples our team has analyzed from Florida to date. It is important to emphasize that these samples are from flooded drinking water wells, non-flooded drinking water wells, and non-drinking water wells (e.g., used for livestock) collected over a 3-week period. Using the well owner survey, we will identify and evaluate all flooded drinking/domestic water wells in the coming weeks as we are currently entering survey data. This effort is being led by Gregory House, an undergraduate researcher studying Civil Engineering at Virginia Tech. Therefore, when reviewing our preliminary data, please keep in mind that rates of bacteria associated with the flooding may be higher or lower than reported here.

38% of wells tested positive for total coliform bacteria, with incidence ranging from 26-50% for counties with 10+ samples collected. Total coliform bacteria is a group of bacteria that commonly live in soil and surface water (e.g., floodwater). The presence of total coliform bacteria sometimes indicates that the well water is contaminated, but not all total coliform bacteria cause disease. While the Florida Department of Health (FDOH) and UF/IFAS Extension recommend that well users disinfect wells that test positive for total coliform as a precaution, it is recognized that total coliform positive results are sometimes due to the presence of these bacteria on the tap sampled and not necessarily in the water, or due to improper handling of samples (i.e., accidentally contaminating samples).

2% of wells tested positive for Escherichia coli (E. coli) bacteria, with incidence ranging from 3-6% for counties with 10+ samples collected. E. coli is a specific type of total coliform bacteria that is a more accurate indicator of bacterial water contamination and potential to cause disease. The presence of E. coli in water indicates contamination with human or animal waste. UF/IFAS Extension and FDOH recommend that well users not drink well water that tests positive for E. coli bacteria until the system has been disinfected and a re-test of the well water no longer indicates the presence of E. coli. 

County Number of Samples % positive for Total Coliform % positive for E. Coli
Citrus 1 0% 0%
Clay 13 38% 0%
Hernando 2 50% 0%
Hillsborough 1 100% 0%
Lee* (15)* 60% 13%
Marion 19 (2) 26% 5%
Monroe 1 0% 0%
Pasco 40 (4) 48% 3%
Putnam 61 31% 0%
Sarasota 16 (1) 50% 6%
Not specified 3 33% 0%
Overall 157 (22) 34% 2%

*In Lee county, samples were collected a day early, which may have underestimated detection of Total Coliform and E. coli. Residents were therefore advised to resample.

The numbers in parentheses indicate the number of invalid samples collected.  Only the samples that were collected according to standard lab procedures were counted in the calculation of percent positivity for Total Coliform and E. coli, with the exception of Lee county.