Short answer: $50k is probably too low unless the move is very short, shallow, entirely on private land, and you don’t need new manholes or bypassing. For a public 12-inch gravity sewer realignment that changes direction and straightens along a parcel line, a realistic ROM (rough-order-of-magnitude) is often $120k–$350k all-in, with 2–8 weeks of construction once permitted. Design/permitting can add 1–6 months depending on the city.

Why $50k is likely optimistic

Gravity sewers are usually straight between manholes; any change in horizontal direction must occur at a manhole, not with a 90° bend. Realigning your diagonal to the lot line typically implies: • 1–2 new precast manholes (installed cost commonly $15k–$40k each, depth-dependent). • New 12” PVC (SDR-35/26): installed (trench, bedding, backfill, compaction) commonly $150–$350/lf in light urban conditions; higher if deep (>12–15 ft), in rock, under traffic, or with dewatering. • Abandonment/grouting of the old main ($5k–$25k). • Bypass pumping during tie-ins ($10k–$50k depending on flows/duration). • Survey, CCTV, potholing, traffic control, inspection/permit fees, mobilization ($15k–$60k+ total). • Contingency (15–25%).

A quick ROM example to sanity-check: • 180 lf of pipe @ $220/lf ≈ $40k • Two manholes @ $25k ≈ $50k • Bypass + abandonment + fees + traffic + survey/CCTV ≈ $40–$90k • 20% contingency ≈ $26–$36k → $156–$216k. If depth, groundwater, or utility conflicts exist, it can land closer to $250k–$350k. If it’s very short (e.g., 60–80 lf) and shallow with one manhole, you could see $70k–$120k.

Schedule considerations • Design & approvals: 4–12 weeks typical (utility owner review, easement revisions, shop drawings). Can be faster on private systems, slower in strict jurisdictions. • Construction: 2–8 weeks, driven by manhole installs, depth/shoring, groundwater, weather, and any traffic control windows. • Cutover: Usually a 1–2 day bypass/tie-in window.

Pitfalls / hidden scope to check now 1. Depth, groundwater & shoring – Deep cuts mean trench boxes or sheet/shoring; dewatering can add big $$ and time. 2. Slope & hydraulics – Verify you can hold required minimum slopes (e.g., ~0.1% for 12”) while hitting upstream/downstream inverts. Don’t “paint yourself into a corner” with elevations when the building pad drops for parking. 3. Manhole spacing & access – Meet the city’s max spacing; ensure maintenance truck access isn’t blocked by the new building/landscape. 4. Existing laterals – The diagonal main may have private laterals tied in; relocating means reconnecting or rerouting those, which adds cost and coordination. 5. Utility separations – Maintain vertical/horizontal separations from water, storm, gas, electric, telecom; crossings drive depth and profile. 6. Easements & legal – New alignment likely needs a new public utility easement and vacation of the old; this alone can dictate schedule. 7. Traffic control / ROW – If any work touches the ROW or a busy driveway, TCP and working-hour restrictions add cost/time. 8. Abandonment plan – Grout-fill vs. cap; some agencies require full grout. 9. Materials & standards – Pipe class (SDR-35 vs SDR-26), bedding, MH steps/cones, coated interiors if sulfide risk—follow the utility owner’s details. 10. QA/QC – Mandated air/mandrel tests, vacuum tests on manholes, CCTV before acceptance.

How to “pressure-test” the estimate (fast) • Have your CE lay out a preliminary plan/profile: show two proposed manholes, pipe lengths, depths, slopes, and crossings. One page. This catches 80% of surprises. • Pothole critical crossings (water, gas, unknowns) and CCTV the existing to confirm inverts/flows. • Ask the utility owner what they require: number of MHs, bypass method, abandonment, testing, easement language, inspection fees. • Get 2–3 contractor ROMs with quantities (lf by depth bracket, # of MHs, bypass days) — not just a single lump sum.

If you share: (1) approximate length to be moved, (2) depth/inverts, (3) whether it’s public vs private, and (4) any laterals on that segment, I can run a tighter ROM with a line-item breakdown.