Study Results:

"There has been a great deal of focus on septic tank communities (OSTDS) as the ones likely to be polluting the most. The Source to Slime Study did not find this to be case."

"all three residential communities (septic, sewer, and sewer with reclaimed irrigation) were polluting about the same amount of Total Nitrogen to the aquifer."

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#1. Copy of Study


#2. Evaluation of water Quality Around the Town of Suwannee

 Page EX-5. "The winter 2009 study provided a unique opportunity to examine the water quality in the canals and the river around the town of Suwannee 13 years after closure of 850 OSTDS in the area.Analysis of the data indicated there was a significant reduction of fecal coliform in the canals, but there was not a significant reduction of nitrogen or total coliforms, which might have been anticipated."

Page EX-5. "It is unlikely that additional studies of these parameters would identify further improvements attributable to septic tank removal, since additional improvements were not apparent after 13 years."

Page 6-2. "A comparison of differences between canal and river stations in 1996 and 2009 indicated a reduction in fecal and total coliform evaluations in canals, but there was not a significant reduction of nitrogen, total coliforms, or occurrences of Salmonella, which might have been anticipated. "


#3. FDOH 2013 Nitrogen Reduction Septic System Study

TITLE - Florida Department of Health Assessment of Water Quality Protection by Advanced Onsite Sewage Treatment and Disposal Systems: Performance, Management, Monitoring

Page 2 “The field assessment included evaluations to determine if the power was on, if there was a sanitary nuisance, if aeration was occurring, and if the alarms were working. Approximately 30% of all the visited sites were not operating properly based on at least one of these measures”

Page 3 “A comparison of median influent and effluent concentrations from systems found 95 percent removal for carbonaceous biochemical oxygen demand (cBOD5), 75 percent removal for total suspended solids (TSS), 33 percent removal for total nitrogen (TN), and nearly no removal for total phosphorus (TP).

Page 16 “There has been no systematic assessment of effluent quality of advanced systems in Florida”

Page 68 “The permit file reviewers for this project marked a check box when evaluating the final inspection form to note when changes to previously entered information were made. Out of the 629 system files analyzed under this task, almost 41% required some sort of change due to information being absent or entered incorrectly.”

Page 69 “Paperwork issues appear to be the majority of the issues relating to enforcement, with 86% of all enforcement issues being either that the maintenance agreement and/or the operating permit are expired.”

Page 121 “Table 47 summarizes the exceedance results. About three quarters of the performance-based treatment systems do not meet their respective treatment standards for TN and fecal coliforms and a third do not meet the standards for TP. For all of these parameters, the tendency was for the random sample to show somewhat better performance or fewer exceedances than the additional samples. This indicates that a performance-based treatment system is unlikely to meet its average performance expectation for total nitrogen and fecal coliform at the point of discharge.”


#4. February 2006: No benefit over a conventional System

TITLE - A Review of Nitrogen Loading and Treatment Performance Recommendations for Onsite Wastewater Treatment Systems (OWTS) in the Wekiva Study Area

Pages 11/12 “Experience in the Florida Keys and elsewhere suggest that systems of this type at individual homes do not perform as well as expected, especially for nitrogen removal (2006 A Review of Nitrogen Loading and Treatment Performance Recommendations for Onsite Wastewater Treatment Systems (OWTS) in the Wekiva Study Area,” by Damann L. Anderson, P.E., of Hazen and Sawyer, P.C., ).”

Pages 12 “The majority of the systems tested would not have produced a benefit over a conventional OWTS installed in suitable soil. In fact, results of denitrification studies by Degen et. al. (1991) suggest that septic tank effluent (STE) discharged to the unsaturated soil zone result in significantly greater denitrification than nitrified aerobic treatment unit effluent.”

Page 12 “Several systems produced results comparable to septic tank effluent form a conventional OWTS which was monitored as a baseline”

Page 13 2006 - Life-Cycle Cost:

Page 13 “There are other ways to improve OWTS performance without as much cost. Literally tens of thousands of existing OWTS in Florida installed prior to “modern” code requirements may not have proper separation from groundwater. Establishment of operating permits for all OWTS, with requirements for septic tank maintenance and upgrade of non-compliant systems to current standards would therefore certainly increase the performance of the existing OWTS base. Requiring timed dosing of all systems and shallow drainfield placement would contribute to increased performance as well.”

Page 20-#4 “Thus, experience in the field suggests that the performance-based treatment systems proposed by the FDOH may not significantly reduce nitrogen loadings from OWTS relative to conventional systems that are properly installed, operated and maintained.”

Page 20-#5 “The cost of these advanced treatment systems are significantly higher than conventional OWTS. It was estimated that the total life cycle cost of such a system would be on the order of $186 per month if capital costs were amortized over a 20-year period and combined with the O&M costs. This cost compares to estimated costs for similar studies in Sarasota and Monroe Counties.”

Page 21-#5 “In regards to OWTS, there are other strategies recommended to improve performance with less cost., some of which could be implemented without study.”


#5. October 2009: Septic System is not the “smoking gun”

TITLE - The Importance of OSTDS Contaminant Loading to the IRL

Page 53 Summary

Page 54 "Plume migration distances, based on NOx-N and SRP, were not great for the

older OSTDS investigated in this NEP study, and were estimated to be 107, 32, and 30 ft.

respectively for the Huy, Grimes and Lounibos sites.


Page 56 “In the two combined SFWMD studies, NOX-N traveled > 55 ft. at three sites (1.6 – 3.0 ft/yr), NH4-N traveled > 55 ft. at two sites (1.1 – 3.0 ft/yr), while SRP migrated > 45 ft. at five of the eight sites (0.95 – 2.7 ft/yr). The NEP site migration rates were generally slower than SFWMD study rates, due to the slow plume migration rates found at the low gradient Ft. Pierce sites (0.3 and 0.4 ft/yr for the Grimes and Lounibos sites, respectively).”

Page 57  “To date, data from this NEP study and from the two completed SFWMD Issues Team studies indicate that OSTDS is not the “smoking gun”, especially in terms of bacterial loading, that many have predicted.”

Copy of Study


#6. January 2018: Wekiva-Area Septic Tank Study

TITLE - Wekiva-Area Septic Tank Study Division of Environmental Assessment and Restoration Florida Department of Environmental Protection

Page 103 “However, the majority (55 %) of the septic systems had a N attenuation of 52 %, which closely matches the 50 % overall N attenuation rate used in previous NSILT calculations.


#7. 2011: Nutrient Loading Lower St. Johns River basin

TITLE -  Preliminary Evaluation of Septic Tank Influences on Nutrient Loading to the Lower St. Johns River Basin and Its Tributaries - FDEP Contract WM952

Page 81 Summary and Conclusions

Page 82 “Data from this study, coupled with collective data from other studies on the Indian River Lagoon (Belanger, Heck and Andrews, 1997; Belanger and Price, 2006; Belanger and Price, 2007; Belanger, 2009; Zarillo et al., 2010), indicate that while OSTDS can contribute nutrients to water bodies such as the LSJR and its tributaries under certain site condition scenarios, properly functioning (not failing) OSTDS may not be as significant a source of nutrients and bacteria as many have thought.

Page 82 “We found in this and previous studies that high nutrient and bacteria concentrations are

usually rapidly reduced down-gradient of non-failing septic tank drainfields in most soil systems, and the data indicate that OSTDS at the majority of these study sites do not appear to have significant groundwater plumes containing nutrients or bacteria.

Page 82 “Although OSTDS impact was found at several locations (above), continuous plumes indicating nutrient and bacterial loading from OSTDS to adjacent down-gradient surface water were not indicated by the monitoring from any of the individual sites in this study.”



Page ii  Based on the survey data reported, 23% of the sewage systems installed today are failing, and 13% are projected to fail within the next 5 years. The southwest region of the state reported the largest number of existing systems (33%) and the southeast region reported the least number of systems (15%).   


# 9 Septic Upgrade Incentive Program Application

Page 3.  “the Department does not endorse or guarantee the functionality of any nitrogen-reducing feature purchased or installed under this program”.