County HSTS Analysis Press Release- April 19, 2020

The Darke County Health Department has recently updated the Geographic Information Systems (GIS) home sewage treatment systems layer. This project involved updating an existing GIS layer with information from the Health Department Information Systems (HDIS) database for new, replacement, or abandoned septic systems. The existing GIS septic system layer was created during an Ohio Environmental Protection (EPA) 319 Grant which located septic system permits and septic tank locations within the Stillwater River Watershed. The 319 Grant helped to evaluated non-point source pollution and helped to determine which systems were discharging off-lot.

Current Septic System Information from HDIS includes permitted septic systems.  Some information includes septic systems from villages if an inspection was made and a permit was matched or if a system was installed. Small villages were not mapped during the 319 Grant because sewer systems were to be installed in some of them.  The villages of Castine, Ithaca, and Gordon are still without sewer. The Health Department has villages statistics for these communities so we know what types of systems are present but the permit matching to a specific address still needs to occur in some cases.  Wayne Lakes, Palestine, and Hollansburg, along with Glen Karn are currently working on plans to sewer the communities.  County address and parcel information was used to determine if a septic system exist on properties where information was not available in GIS or HDIS.  These locations, as well as village septic systems are included in the “unknown” category.  Also listed as “unknown” are commercial properties that were assumed to be under a permit from the Ohio Environmental Protection Agency but these properties need to be evaluated to assure they are permitted.  It has been found over the years that some commercial properties have neither permits under the local health department or the OEPA. There are approximately 1,170 addresses in the unknown category.  These also include agricultural barns that may have had restrooms installed without a permit.

There are some septic systems that need removed from this analysis that may have went to sewer.  Quality control with the database will need to occur to remove these systems.

April 2020 Statistics

1497 Aeration Systems (off-lot or discharging)

163 Dry wells (off-lot or discharging)

6498 Leachfields (non-discharging)

1545 Tank to Tiles (off-lot or discharging)

33 Mounds (non-discharging)

28 National Pollutant Discharge Elimination Systems (off-lot or discharging, but have additional treatment to meet current EPA standards)

1 Presby (non-discharging)

1 Drip Distribution (non-discharging)

869 Subsurface Sandfilters (off-lot or discharging)

32 Privy

10 Holding Tanks (Systems no longer permitted on residential properties)

TOTAL SYSTEMS:  10,677 and an additional 1,170 unknown systems = 11,847


Past statistics from GIS include information in the Stillwater River Watershed and do not include most homes in villages.

1415 Aeration Systems (off-lot or discharging)

122 Dry wells (off-lot or discharging)

4905 Leachfields  (non-discharging)

1675 Tank to Tiles (off-lot or discharging)

24 Mounds (non-discharging)

5 National Pollutant Discharge Elimination Systems (off-lot or discharging, but have additional treatment to meet current EPA standards)

1 Presby (non-discharging; experimental)

898 Subsurface Sandfilters (off-lot or discharging)

34 Privy (outhouse)

5 Holding Tank


With the county’s Operation and Maintenance (O&M) program, we have been evaluating the permitted septic systems to assure they are working properly. Through this program, with permit data, and through our GIS analysis, we were able to reanalyze our system data to see what types of septic systems are now in the county and which homes still do not have permitted systems.

Homes without septic systems can cause high sewage pollution potential in our waterways. An average 3-bedroom home can produce approximately 360 gallons per day of sewage. If there is not an adequate septic system or if the system discharges directly to a tile, untreated, this causes pollution to go into both our ground and surface waters.  From this analysis, we see that there are 1545 tank to tile systems which are not permitted and discharge untreated sewage to a tile or stream.  If the average home is 3 bedrooms, these tank to tile systems can potentially cause 556,200 gallons of untreated sewage to discharge off- lot.  This number does not include other discharges such as sand filters and older aeration systems that are not working properly and do not meet discharge standards or leachfields that have been bypassed to a tile because of failure.  The O&M program has consistently shown over 50% of the septic systems are either not working properly or need some type of update.  Drywells are also not included in this number and these systems are no longer acceptable in the state and are to be replaced.  Most of our drywall systems are within Wayne Lakes which may soon be going to a sewer system. If we include all discharges that do not meet EPA standards and failing systems, the county could potentially seeover 1.4 million gallons of untreated sewage entering our waterways everyday.

Sewage contains viruses, bacteria, and high amounts of phosphorus and nitrogen which lead to Harmful Algal Blooms (HAB) and lowered dissolved oxygen levels that harm the water environment and impacts fishing and swimming.Although an individual household may make a small impact on its own, all homes without septic system and those that are failing can collectively make a huge impact on our environment. The United States (US) Environmental Protection Agency (EPA) lists septic systems to be the second greatest threat to groundwater. Twenty-five percent of the US population is served by a HSTS (2005).

If an onsite HSTS is working as it was designed, sited, and installed, the septic tank will help to remove the solids and the leachfield will disperse effluent into the soil which will utilize natural microbes to remove harmful viruses and bacteria, keeping groundwater clean. This groundwater may end up as drinking water so removing contaminants is a necessary component.

The EPA reports at least 10 to 20% of septic systems are failing and this number is expected to increase as many systems have surpassed their lifespan (2005). Because of these failures, the amount of sewage that may be entering our waters is excessive.

Local health departments, along with state departments of health, work to educate the public and create policies on septic system maintenance and updates, along with timeframes.  Existing tank-to-tile systems need to be upgraded in the county and homeowners should expect to receive letters with timeframes to replace these systems.  All septic systems need to be on out O&M program and need to have proper permits and installations to do so.  The Darke County Health Department actively applies for grants in order to help homeowners.  USDA grants and county CHIP funding may also help homeowners to install new septic systems.


United States Environmental Protection Agency, Office of Water. (2005). Decentralized wastewater treatment systems: a program strategy. EPA 832-R-05-002. Retrieved from:


More septic system information can be found here and more information on our O&M program can be found here!