2.3 Improve knowledge about the location and status of septic systems and prioritize areas for upgrades or conversions

Key Message: There are conflicting estimates of the number of septic systems in Sarasota County. Clarifying how many septic systems exist, where they are located, and their functional status is fundamental to managing their potential environmental impacts.

Importance

There are conflicting estimates of the number of septic systems in Sarasota County and their functional status. Multiple overlapping utilities and agencies keep records of permits, repairs, and removal and many systems pre-date digital records, so there is no single database. Knowledge of the number, location, and status of septic systems in Sarasota County is fundamental to managing their impacts and prioritizing investments for upgrading to advanced technologies or converting to central sewer.

Overview

The Florida Department of Health (FDOH) maintains a statewide inventory of the location of septic systems through its Florida Water Management Inventory (FDOH 2016), although it is widely recognized as inaccurate. The inventory represents an unverified estimate of septic systems, characterizing parcels as being “known, likely, or somewhat likely” to have septic systems (Figure 2.3.1). Recognizing this knowledge gap, legislators filed bills in 2019 requiring FDOH to identify and map all septic systems in the state by January 1, 2021. The bills died in committee. In 2019, Sarasota County Government conducted an independent analysis of the FDOH inventory of septic systems in its jurisdiction.

The FDOH inventory identified 40,692 parcels with “known, likely, or somewhat likely” septic systems in Sarasota County. Sarasota County’s own inventory identified 48,853 parcels with “known or likely” septic systems. The difference between these inventories — 8,161 systems — is significant. Both estimates are believed to be inaccurate. Knowing how many septic systems exist in Sarasota County, where they are located, and their status is fundamental to managing their potential environmental impacts. Reducing this knowledge gap is an important management activity, especially for areas near priority waters.

Approach

A GIS-based exercise followed by ground-truthing is required to strengthen our knowledge of the number of septic systems, their location, and status in Sarasota County. The Sarasota County property appraiser database showing all parcels should be the base layer. Vacant parcels and parcels currently serviced by central sewer should be identified and excluded. This map should be compared to the FDOH and Sarasota County Government maps and discrepancies identified and updated. This process could involve ground-truthing through queries to utilities, HOAs, neighborhoods, and individual homeowners. The goal should be to develop a place-based inventory of parcels with “known” septic systems or “known” sewer service. 

The next step is adding data associated with “known” septic systems, such as date constructed; date of last repair; soil type; estimated depth between bottom of the drainfield and seasonal high-water table; and likely fate of groundwater flowing beneath the drainfield (see Chapter 2.1). This database should be used, in conjunction with water quality monitoring data and onsite inspections, to identify and prioritize areas of concern. Together, this information will facilitate recommendations for mitigating nitrogen loading from these systems (see Chapter 2.2). Solutions could include the addition of advanced nitrogen treatment technologies to existing septic systems; interception of nutrients with a denitrification barrier installed between the offending septic systems and the water body of concern; or conversion of septic systems to central sewer service.