What Would the Southwest Connection Cost?
- Fight FM150
- Jul 23
- 6 min read
Updated: Jul 23
A plain-language cost guide for Dripping Springs / Hays County residents ·
~2026 dollars · construction not funded
$300M Mid all-in (8.5 mi) | $164–$505M Planning range | $35M Per mile (mid) | Not funded Construction status |
This is an estimate — and design ≠ construction
The ~$300M mid figure is a public construction yardstick from local comps and TxDOT bridge costs. It will move when engineers lock alignment, spans, and ROW. Construction is still not funded. What is funded so far is design: about $0.75M (2019 Friese study) plus a $2.99M Structurepoint design contract (Dec 2025) — not building the road.
The short answer
Building the full preliminary corridor from US 290 to RM 12 — about 8.5 miles of new four-lane divided road with bike/ped space, multiple Onion Creek crossings, and roundabouts at major local roads — lands near $300M mid (~$35M per mile), with a planning range of about $164–$505M. That is in the same ballpark as Hays County’s Darden Hill Phase 2 (1.7 mi of four-lane divided at $51.8M all-in, or ~$30.5M per mile).
Design already under contract
These are real professional-services contracts. They pay for studies and plans — not
asphalt, bridges, or right-of-way acquisition for construction.
Contract | Amount | When | What it covers |
K Friese + Associates | $750,000 | Dec 2019 | Preliminary engineering + public involvement (RM 12 → US 290 study / ~20% design era) |
American Structurepoint | $2,986,101 | Dec 2025 | Additional planning & design, US 290 → RM 12 (Pct 3 & 4); schematic through PS&E via work authorizations |
Friese: Hays County minutes 2019-12-10 (RM 150 Extension PSA). Structurepoint: Dec 16 2025 agenda packet compensation cap (selected Nov 18 2025). County project page still shows ~$4M design framing; Community Impact has cited ~$1.44M for the 2.4 mi Precinct 4 slice — neither is a construction OPCC.
Corridor map and elevation profile
Crossings and junctions (with planning cost)
ID | Mile | Elev (ft) | Span (ft) | Mid $M | Type | Name |
R1 | 0.00 | 1093 | — | 9.0 | Roundabout | RM 12 / RM 150 |
B1 | 0.29 | 1037 | 520 | 7.0 | Bridge | Onion Creek main floodplain |
B2 | 1.08 | 1086 | 410 | 5.7 | Bridge | Onion Creek trib / east draw |
R2 | 2.41 | 1228 | — | 4.0 | Roundabout | Mt Gainor Rd |
B3 | 2.48 | 1183 | 260 | 4.0 | Bridge | Valley west of Mt Gainor |
B4 | 4.46 | 1205 | 260 | 4.0 | Bridge | Major valley |
B5 | 5.22 | 1194 | 490 | 6.9 | Bridge | Major valley |
R3 | 6.19 | 1212 | — | 4.0 | Roundabout | Pursley Rd |
B6 | 6.24 | 1182 | 260 | 4.0 | Bridge | Major valley |
B7 | 7.61 | 1215 | 200 | 3.0 | Bridge | Draw floodplain ~200 ft |
R4 | 8.25 | 1313 | — | 4.0 | Roundabout | Creek Rd / RM 165 |
Spans from DEM valley width (+15 ft rise mid); cost = structure + approaches at TxDOT FY2025 ~$135/sf × 90 ft deck. B2 mid treats half the broad valley as embankment. R1 (~$9M) is a separate county project — not inside the $300M corridor total. R2–R4 share the corridor intersections line (~$4M each).
Baseline 1 — the road
Cleanest local comparison: Darden Hill / CR 162 Phase 2 (Sawyer Ranch roundabout → RM 1826) — 1.7 mi four-lane divided at $51.793M all-in (const + utilities + ROW + design + CEI), or about $30.5M per mile.
Scaling that rate to 8.55 mi ≈ $260.7M for roadway-class work. Our full-project mid (~$300M, ~$35M/mi) sits a little higher — expected for a greenfield alignment with more bridges, recharge-zone drainage, and new right-of-way. Darden is largely a widening; this corridor is mostly new road across draws and floodplain.
Baseline 2 — bridges
Instead of one guess for every crossing, valley width is measured on the 10 m DEM profile (how far ground stays within ~15 ft of the local low). Cost uses TxDOT FY2025 ~$135/sf (unit-cost PDF), a ~90 ft deck, and a small approach allowance. B2’s broad bowl is half bridge / half fill in the mid case.
Majors B1–B6 mid sum ~$31.4M · B7 in minor structures · Source: DEM profile spans × TxDOT $/sf
Local bridge comp | Setting | Public $ | Why it matters |
Creek Rd (CR 190) Onion Creek | 2-lane off-system replacement, DS | ~$1.5–1.6M | Floor for a modest span — nearer B3/B4/B6 than B1 |
Cole Springs Rd Onion Creek (Buda) | New crossing + developer package | ~$7.6M | Same order as B1 mid (~$7M) |
Baseline 3 — roundabouts
County preference has been roundabouts at major local roads. The east-end gateway — RM 150 at RM 12 — is already a multi-million-dollar project by itself (~$5M county CO + ~$3.8–4.2M CAMPO; published figures vary about $5–9M). Corridor RAs use that scale as a planning check.
ID | Crossing | Mid $M | In corridor total? |
R1 | RM 12 / RM 150 | ~$9.0M | No — separate project |
R2 | Mt Gainor Rd | ~$4.0M | Yes — share of ~$12M RA / tie-in line |
R3 | Pursley Rd | ~$4.0M | Yes — share of ~$12M RA / tie-in line |
R4 | Creek Rd / RM 165 | ~$4.0M | Yes — share of ~$12M RA / tie-in line |
R1 mid ~$9M from published RM12/150 package (not added again into the $300M corridor total). R2–R4 mid ~$4M each (= $12M corridor intersections line ÷ 3); R4 also covers the US 290 tie-in.
Putting the pieces together
Hard construction ~$180.4M plus soft costs / ROW / risk ~$119.1M → ~$300M mid (~$35M per mile). Planning range about $164–$505M.
Bucket | Mid ~$M | Everyday comparison |
Roadway + drainage + paving + earthwork + bike/ped + util + mob. | 131 | Darden Hill × length, adjusted for new alignment |
Bridges & large culverts | 38 | Profile spans; B2 half-fill; B1/B5 long |
Intersections (corridor RAs) | 12 | Below full RM12/150 cemetery-shift package each |
Contingency + design + CEI + ROW + env | 119 | ~195 ac net take + planning contingency |
All-in mid | 300 | ~$35M per mile |
Line-item planning estimate (mid $M)
Road projects usually call this an engineer’s line-item estimate or OPCC — not a manufacturing “BOM.” Each row is a planning allowance; the anchor is a public dollar figure (unit bid, local project, or % of construction) that sets the scale.
Hard construction (~$180.4M)
Category | Mid $M | Anchor |
Earthwork / grading / rock | 20.6 | |
Pavement structure (4 lanes + median + shoulders) | 44.5 | |
Drainage, storm sewer, water-quality BMPs | 32.0 | |
Major bridges (6 crossings, profile spans) | 31.4 | |
Minor bridges / large box culverts | 6.5 | |
Shared-use / bike-ped facilities | 7.8 | |
Signing, striping, signals/lighting | 6.4 | |
Intersections & roundabouts | 12.0 | |
Utilities / prep ROW / fencing | 8.9 | |
Mobilization / traffic control / SWPPP | 10.3 |
Soft costs / ROW / risk (~$119.1M)
Category | Mid $M | Anchor |
Construction contingency | 39.2 | |
Design / env / schematic / PS&E | 23.5 | |
CEI / construction engineering | 18.8 | |
ROW fee take (land) | 17.6 | |
Remainder damages, settlements, legal | 15.0 | |
Env mitigation / permits / karst | 5.0 |
Confidence
Planning accuracy is roughly ±35–50% until Structurepoint schematic design and surveyed ROW exist. Costs follow the 2021 preliminary centerline; a shifted preferred alignment changes bridges and parcels. R1 is separate — do not double-count it into the corridor mid. Combined design fees (~$3.7M Friese + Structurepoint) are not a construction OPCC.
Sources
Hays County minutes — Dec 10 2019 — K Friese PSA $750,000 (RM 150 Extension / SW Connection study)
Hays County agenda packet — Dec 16 2025 — American Structurepoint design compensation cap $2,986,101
Darden Hill Phase 2 — $51.793M; 1.7 mi; const + util + ROW + design + CEI
RM 150 at RM 12 Roundabout — ~$5–9M published / CAMPO share · County SW Connection page (~$4M design framing)
TxDOT FY 2025 Bridge Unit Costs — ~$135.29/sf · Creek Rd CR 190 (~$1.5–1.6M) · Cole Springs, Buda (~$7.6M) · USGS 3DEP 1 m DEM · 2021 centerline
Independent planning-level estimate for public discussion. Not a Hays County engineer’s estimate, OPCC, or bid.
