A Goshen lot with poorly drained soil: when an aerobic treatment unit makes sense

The starting point

Picture a wooded lot of a couple of acres in Goshen Township, bought years ago as the site for a retirement home. It sits on flat ground in unincorporated Clermont County, beyond the reach of any sewer, and the plans call for four bedrooms. Nothing gets built until Clermont County Public Health approves a sewage treatment system, and that approval starts with the soil.

The soil evaluation decides it

Ohio's current rules, in force since January 1, 2015, size a system from the soil itself rather than from a single perc number. Under OAC 3701-29-15, the designer chooses a loading rate from the structure, texture, and consistence of the most limiting soil layer near the bottom of the proposed trench, then divides the home's daily design flow by that rate to get the absorption area required. OAC 3701-29-11 sets design flow at 120 gallons per bedroom per day, so this four-bedroom house is designed around 480 gallons a day.

Southwestern Ohio's flat, loess-covered till plains make that arithmetic hard. The USDA's official description of Clermont silt loam calls it poorly drained, with a water table that can sit anywhere from half a foot below the surface to half a foot above it between November and May. Avonburg silt loam, one of the two example soils the Clermont Soil and Water Conservation District uses to explain the county soil survey, holds a perched water table 6 to 18 inches down in normal years, and Rossmoyne silt loam, the other, has a dense fragipan starting 18 to 30 inches below the surface. On ground like this, the question is rarely whether a standard gravel trench will work; it is which alternative the soil will accept.

The three options on the table

With a standard trench ruled out, the designer and the health district look at systems that treat or disperse effluent differently. National 2026 installed-cost ranges are from HomeAdvisor:

• A mound. EPA describes mounds as an option where soil is shallow, groundwater is high, or bedrock is close. Effluent is pumped in timed doses into a sand mound built above the native soil and treated on its way down. HomeAdvisor lists mounds at $10,000 to $20,000.
• Drip distribution. Drip laterals sit in the top 6 to 12 inches of soil, so no mound is needed, but EPA notes the system needs a large dose tank and electrical power, which adds expense and maintenance. HomeAdvisor lists drip systems at $8,000 to $18,000.
• An aerobic treatment unit. EPA says ATUs suit smaller lots, inadequate soil, high water tables, and homes near sensitive surface water, because the injected oxygen treats wastewater further before it reaches the soil. HomeAdvisor lists aerobic systems at $10,000 to $20,000. On a site like this, an ATU typically feeds a soil dispersal method such as drip.

The last test is legal, not technical. Ohio EPA's general permit for household systems that discharge off the lot covers only situations where sewers and on-site dispersal are not options, and it excludes discharge proposals from newly created lots. If a mound or drip field can work on the lot, a discharging system is off the table.

What the permits cost

Clermont County Public Health's current fee schedule lists $600 for a residential site review and $674 for a new installation permit, which includes the $74 state fee. Fees are reset from time to time, so confirm the figures with the district before you budget. Under OAC 3701-29-09, only a registered installer may build the system, under that permit. On the rare lot that does qualify for Ohio EPA's discharge coverage, the homeowner's share of the application adds a $200 fee.

What ownership looks like afterward

Any system with a pump, a timer, or an aerator lives on a shorter leash than a gravity trench:

• Clermont County's Regulation 415 assesses systems with electrical components every 19 months and requires every time-dosed system to carry a service contract with a registered service provider.
• An owner may submit a registered service provider's assessment, completed within 90 days of the operation permit renewal, in place of the county's own.
• A discharging system under Ohio EPA coverage is assessed and sampled by the county every 12 months, and Ohio EPA requires annual diagnostic sampling for total suspended solids, ammonia, dissolved oxygen, E. coli, and chlorine where chlorine is used.
• Aerators, pumps, and alarms run on electricity, so plan for the power bill and for outages.

What this shows for Goshen-area lots

• Order the soil evaluation before you close on land, not after the house plans are drawn.
• Budget for an alternative system wherever the soil survey shows poorly drained or fragipan soils, and hire a designer who knows Clermont County's site review.
• Expect ongoing service costs with any pumped or aerobic system, and keep the contract current.
• Talk to the health district early. Its site review is where these questions get answered for a specific lot.

For the county's inspection cycle, records search, and fees in one place, see our Clermont County septic guide, and our septic installation page covers what an alternative-system install involves.