In January 2026, the Thompson's Station Board of Mayor and Aldermen approved two agreements that let developers pay wastewater impact fees in full up front. That bought them a place in the next expansion of the town's treatment plant. One agreement reserves 31,250 gallons per day for a 359-acre property at 1735 Old Thompson's Station Road, with a fee of $1,404,835. The other, filed under the Briar Hill name, reserves 10,500 gallons per day for $472,024.56. Divide either fee by its gallons and you get the same number, about $44.95 per gallon of daily capacity.
Mayor Stover made a point of saying on the record that the vote approved capacity only. It did not approve any development and gave no vesting rights. So in this town a developer may pay more than a million dollars before a single lot is approved, just to make sure the homes can be connected to a plant. If you're comparing Williamson County towns, that one detail explains a lot about how new construction here gets built.
Why gallons are the bottleneck
Most towns send treated wastewater into a river. Thompson's Station says it can't discharge treated effluent into local rivers. It sprays the water onto fields or runs it through subsurface drip fields instead. That means capacity depends on how much water the plant can treat and also on how much land the town has to put it back into the ground. You can see both limits in the capital plan. It lists $8.5 million for fiscal year 2026 and $2.7 million for fiscal year 2027 under "WWTP MBR + additions," plus $10.5 million for the Ozzad drip fields.
The town's wastewater project page says both municipal systems are at capacity until the Regional plant upgrades are done. The January 2026 reservation agreements go further. They say every capacity reservation at the Regional plant has been used up. The town's own documents don't agree on the plant's size. An undated project page gives 470,000 gallons per day of permitted capacity, rising to 1 million after the upgrade. The 2026 agreements and March minutes describe a plant rated at 1.5 million gallons per day, with a three-phase expansion taking total capacity to 3.3 million. Whichever figure is current, every version tells the same story. The town has been handing out capacity that isn't built yet.
Here is how the 2025 and 2026 records track that capacity.
| Date | What the town recorded |
|---|---|
| June 17, 2025 | Utility Board told the town is "at the cusp" of capacity; 150,000 gpd set aside for economic development |
| January 13, 2026 | About 260,000 gallons estimated to remain in the next expansion phase |
| March 10, 2026 | Fixed 150,000 gpd economic development reserve described as fully exhausted |
| March 10, 2026 | Reserve replaced with 15% of Active Capacity for nonresidential use plus 2.5% for emergencies |
The switch to a percentage matters for housing. Before, business and commercial users drew from a fixed bucket. Now they get a set share of whatever Active Capacity the town has, and that share grows as each phase comes online. The town is telling everyone that residential growth won't get every new gallon.
Holding a place in line takes money
The reservation system has teeth. In June 2025, staff said the town would mail letters to people holding reservations who hadn't paid their 25% deposit. Anyone who missed the deadline would be dropped from the list. The January 2026 agreements went beyond a deposit and required the full impact fee by July 13, 2026, or sooner if a development plan was approved first. The public records we reviewed don't show whether those fees were paid.
In March 2026, the board passed Ordinance 2026-002, which moved routine reservation reviews from the board to town staff for applications submitted after April 1, 2026. It also adopted an updated standard reservation agreement. Because of that, future allocations will happen less often at public meetings, where anyone can follow them.
The pipes are expanding too. In January 2026, the board approved a $4.2 million low bid from Humerick Environmental Construction for the Highway 31 Gravity Sewer Improvements. Staff expected construction to start in spring 2026. We couldn't confirm from public records whether work has started.
The edges of town are where it gets contested
The town would rather tie growth into the Regional plant than see small private plants spread across the map. In 2025 it expanded the Regional coverage area to the east and west, with no coverage in the rural T2-zoned areas on the west side. It also moved to limit on-site systems. In June 2025, the Utility Board voted unanimously to recommend against on-site treatment agreements for a 130-lot subdivision at 1850 Lewisburg Pike and a 30-lot subdivision at 2053 Lewisburg Pike. The board still approved the 2053 agreement in July 2025, according to a later staff report. On August 11, 2026, it rejected a request to change that agreement by removing a one-acre land dedication.
Who pays for service out there is settled. Town Administrator Wood said extending service east of Lewisburg Pike would be developer-driven, and suggested that developers building in the same area form groups to share the cost of ponds, pump stations, and pipelines.
At the same August 11 meeting, the board approved an on-site wastewater system at 2126 Carters Creek Pike, near West Harpeth Road. It will support 164 single-family homes with 93,000 gallons per day of total capacity. The vote was 3 to 2. The minutes record why the vote was close.
"I feel this property is too far out of Town and we will stretch ourselves to thin." — Mayor Stover, August 11, 2026 minutes
Vice Chairman Alexander said the applicant met the standards but called the system a long-term burden for the town. Board members also raised concerns about long-term ownership, who would be responsible for running it, and staffing "with the new plant coming online." The town has used this model before. A separate agreement allows a Bio-Clere decentralized system at 2601 Tom Anderson Road because that property had no town capacity and sat outside the service area at the time. That system can expand up to 100,000 gallons per day.
What this changes in a purchase
The established neighborhoods already sit on town wastewater. The town lists Allenwood, Avenue Downs, Bridgemore Village, Fields of Canterbury, the Heritage Commons commercial district, Tollgate Village, and Whistle Stop as served areas. Developers of Tollgate Village, Bridgemore Village, and Fields of Canterbury built the Regional system. The smaller Heritage system serves the commercial and Town Center area. Even in those neighborhoods, the system still needs upkeep. The FY2026 capital plan lists a $500,000 rebuild of the Tollgate main station and Bridgemore system.
For a resale home in one of those neighborhoods, the sewer question is mostly answered. A new-construction contract or a lot purchase near the edge of town calls for more homework. Before you commit, ask the builder or seller:
- Which system will serve the home: the Regional plant, the Heritage system, or a decentralized or on-site plant?
- Does the developer hold a capacity reservation, and has the deposit or impact fee been paid?
- Does the reservation sit in active capacity or in a future expansion phase that isn't built yet?
- If it's an on-site system, who owns and operates it now, and who will take it over later?
- Has the development plan itself been approved, apart from the capacity agreement?
Question five comes straight from the mayor's January remark that reserving capacity has nothing to do with approval or vesting. Your attorney and the town can confirm what applies to a specific property. This post is general information, not legal advice.
A few quick answers
Is there a sewer moratorium in Thompson's Station?
The 2025 and 2026 town records we reviewed show capacity reservations, deposit requirements, and limits on on-site systems. They don't show a town-wide connection moratorium.
Is the upgraded plant finished?
It isn't confirmed. In June 2025, the contractor was reported about 60 days behind, with work expected to run into January. August 2026 minutes describe the new plant as coming online and include an emergency purchase of a blower for the treatment plant. We found no published final permitted capacity.
Does this affect homes that are already connected?
The reservation process applies to new capacity. Existing service areas stay on the town's maintenance schedule, like the Tollgate and Bridgemore rebuild in the capital plan.
If you're looking at new construction in Thompson's Station and want to know where a specific subdivision stands on the sewer list before you sign, Bobbi Jo Barnes will pull the town records and walk through them with you. Let's find your way HOM, and make sure the plumbing gets there too.
