Sewer lateral size just killed three weeks of work on a 1940s freight depot in Fentress County

That is a clean kill decision and it reads like you made it the right way: with the civil engineer's actual number in hand, not a gut feeling.

The thing worth naming for anyone watching this thread is what happened mechanically. A 4-inch cast iron lateral serving 14 units hits two separate problems. First, capacity: 14 residential units will almost certainly exceed what a 4-inch line can handle depending on the fixture unit count your plumber calculates. Second, condition: cast iron from the 1940s running 190 feet is likely tuberculated inside, meaning the inside walls have decades of mineral buildup that shrinks the effective diameter further. Even if the municipality had agreed to cost-share the boring, that line probably needed full replacement anyway. Your civil engineer would know, but it is worth asking if you have not already.

The $36,000 gap is real, but the seller's perception of value is also a real constraint, and you named both. Renegotiating someone who believes he underpriced it is a different conversation than renegotiating someone who knows a problem has surfaced. One way to have that second conversation is to hand him the boring quote and the engineer's letter, not as a negotiating tactic, but as documentation. Some sellers shift when the problem has a cover page. Whether he is that seller is something you have a better read on than anyone here.

Nine days is enough time to put a number to him once with the documentation attached. If he passes, you pass, and the depot waits for someone with a different utility situation or a shallower unit count that the 4-inch line might actually serve.

What is the building's footprint configuration? I am curious whether a smaller unit count changes the lateral math at all, or whether the boring is fixed cost regardless.

Fentress County is about as rural as it gets in Tennessee so I am curious whether the municipality even has capacity at the main to serve 14 units once you get the lateral there, or whether that conversation was still ahead of you.

The $58,000 bore quote sounds about right for a state route crossing with any real depth to it, we got a similar number in Overton County two years ago for a much shorter run because TDOT inspection requirements alone add a week of standby time to the contract.

Nine days is not enough to find a different use that pencils without the sewer, but have you priced what a commercial tenant needing minimal plumbing looks like on that footprint, because sometimes the building that will not do residential does fine as cold storage or a maker space with a single bathroom served off the existing lateral.

Nine days is enough time to get a second boring quote.

Did you price a private aerobic system before walking? Depending on lot coverage and county health regs, some of these old freight parcels have enough land to permit one, and a $25,000 to $30,000 package plant beats a $58,000 bore by enough to change the math. One call to the county sanitarian before the nine days run out costs nothing.

What unit count would actually pencil if you dropped to 8 or 9 apartments instead of 14?

The number worth running before you fully close the file is whether a non-residential adaptive use, something like self-storage, a brewery tap room, or a flex creative space, changes the sewer load calculation enough that the 4-inch lateral becomes adequate without upsizing, because municipal flow requirements for those uses are typically a fraction of what 14 residential units demand. Fentress County's tourist economy around the Big South Fork corridor has absorbed some unconventional repositioning, so the demand question is at least askable. The checklist I would run in your remaining nine days: confirm the actual fixture unit count the municipality used to reject the 4-inch line, get the boring contractor to quote horizontal directional drilling separately from open cut in case a second method changes the number, pull the deed to see whether the diagonal state route created any utility easement language you could argue entitles you to cost participation, and check whether the building qualifies for Tennessee's Historic Preservation Tax Credit, because at 8,400 square feet of 1940s brick and timber in a documented freight context it likely does, and that credit can reframe a cost basis that currently looks fatal.

What did the municipality give you as the basis for rejecting the existing lateral, a fixture unit threshold or a linear footage pressure calculation?

Check whether Fentress County has a septic variance track for adaptive reuse before the clock runs.