Scour-Critical Bridges in Montana

Montana has 154 bridges rated scour-critical by the Federal Highway Administration. These bridges have foundations that are unstable or at risk of undermining during flood events. Scour-critical doesn't mean a bridge is about to collapse — it means extra monitoring and countermeasures are in place — but these structures are priorities for repair or replacement.

How this ranking works

This state list filters to NBI scour ratings 0 through 3, then sorts by average daily traffic. It is intended to show flood-vulnerability exposure, not to label any bridge as currently unsafe.

Bridge	County	Scour Rating	Daily Traffic	Condition
I 90 over Gallatin River	Gallatin	3 — Serious	9,726	Fair
I 90 over Gallatin River	Gallatin	3 — Serious	9,726	Fair
Whitefish Stage RD over Stillwater River	Flathead	3 — Serious	7,156	Fair
US 93 over Bitterroot River	Ravalli	3 — Serious	6,979	Fair
I 90 over Yellowstone River	Park	3 — Serious	6,397	Fair
I 90 over Yellowstone River	Park	3 — Serious	6,397	Fair
York RD over Prickly Pear Creek	Lewis and Clark	3 — Serious	6,170	Fair
Woodside Cutoff RD over Bitterroot River	Ravalli	3 — Serious	5,076	Fair
S 78 over Yellowstone River	Stillwater	3 — Serious	5,017	Poor
Airport RD over Hyalite Creek	Gallatin	3 — Serious	4,997	Good
Second ST S-us 89 over Yellowstone River	Park	3 — Serious	4,964	Fair
Old HWY 312 over Yellowstone River 170	Yellowstone	3 — Serious	4,005	Poor
North AVE W over Bitterroot River 010	Missoula	3 — Serious	3,627	Fair
US 191 Fh 45 over Cougar Creek	Gallatin	3 — Serious	3,139	Fair
Mt 41 over Beaverhead River	Madison	3 — Serious	2,865	Fair
Bell Crossing over Bitterroot River	Ravalli	3 — Serious	2,814	Fair
S 23 over Yellowstone River	Richland	3 — Serious	2,438	Poor
Going-to-the-sun R over Divide Creek	Glacier	3 — Serious	2,300	Fair
North Entrance Roa over Gardner River	Park	3 — Serious	2,294	Fair
Amsterdam RD over Gallatin River	Gallatin	3 — Serious	1,889	Fair
Skalkaho HWY over Skalkaho Creek 053	Ravalli	3 — Serious	1,713	Poor
S 7 over Beaver Creek	Wibaux	3 — Serious	1,671	Fair
S 2 over Jefferson River	Gallatin	3 — Serious	1,515	Fair
Murphys LN over Yellowstone River 004	Park	3 — Serious	1,471	Fair
S 359 over Bricker Sparrow Ditch	Madison	3 — Serious	1,429	Fair
Inner Belt Loop over Alkali Creek 208	Yellowstone	3 — Serious	1,178	Good
S 540 - E River RD over Yellowstone River	Park	3 — Serious	1,160	Fair
IRR over Tongue River	Rosebud	3 — Serious	877	Fair
W Dry Creek RD over East Gallatin River	Gallatin	3 — Serious	825	Fair
IRR - S 66 over White Bear Creek	Blaine	3 — Serious	763	Fair
Old Clyde Park RD over Ferry Creek 037	Park	3 — Serious	677	Fair
Rock CR RD over Clark Fk-rr-hwy 106	Missoula	3 — Serious	603	Fair
Camas Road over Mcdonald Creek	Flathead	3 — Serious	560	Fair
Quast LN over Surprise Ditch 060	Ravalli	3 — Serious	537	Poor
Sarpy Creek RD over Little Bighorn River	Big Horn	3 — Serious	514	Fair
US HWY 91 N over Dry Fork Marias 080	Pondera	3 — Serious	511	Fair
W Grove ST over Rosebud Creek	Stillwater	3 — Serious	507	Good
Many Glacier Road over Apikuni Creek	Glacier	3 — Serious	452	Fair
Many Glacier Road over Windy Creek	Granite	3 — Serious	452	Fair
Granite Creek RD over Big Cherry Creek 119	Lincoln	3 — Serious	334	Fair
Sycamore Street over Warm Springs Creek 009	Deer Lodge	3 — Serious	283	Fair
Kountz RD over Jefferson River 017	Madison	3 — Serious	269	Fair
Dry Creek RD over Dry Creek 119	Gallatin	3 — Serious	265	Fair
S 21 over Elk Creek 119	Lewis and Clark	3 — Serious	260	Fair
Dry Creek Road over Dry Creek	Dawson	3 — Serious	246	Fair
4-h RD over Musselshell River 008	Musselshell	3 — Serious	208	Fair
Two Medicine Road over Two Medicine River	Glacier	3 — Serious	183	Fair
Two Medicine Road over Appistoki Creek	Glacier	3 — Serious	183	Fair
HWY 287 Bypass over Missouri River 019	Broadwater	3 — Serious	178	Poor
S 300 over Musselshell River	Golden Valley	3 — Serious	172	Fair
Stafford Ferry RD over Taffy Creek	Fergus	3 — Serious	168	Good
W M RD over Arrow Creek 099	Yellowstone	3 — Serious	164	Fair
Marshall Creek RD over Rock Creek	Granite	3 — Serious	161	Poor
Main Boulder Road over Boulder River	Park	0 — Bridge closed	157	Poor
S 24 over Timber Creek	McCone	3 — Serious	153	Fair
W Reserve HWY over Big Muddy Creek Overflow	Sheridan	3 — Serious	151	Fair
Silver Spring RD over Ruby River 023	Madison	3 — Serious	133	Poor
Cleveland RD over Bean Creek	Blaine	3 — Serious	121	Fair
Shippe Canyon RD over Big Muddy Creek 032	Sheridan	3 — Serious	117	Fair
Old Stage Road over Yellowstone River 077	Park	3 — Serious	104	Fair
IRR - S 251 over Smoke Creek	Daniels	3 — Serious	101	Poor
Corinne Trail over Horse Prairie Creek 043	Beaverhead	3 — Serious	100	Poor
Rock Creek RD over Big Lake Creek 081	Beaverhead	2 — Critical	100	Poor
Browns Bridge RD over Big Hole River 123	Beaverhead	2 — Critical	100	Poor
Irrc0unty Road 223 over Soap Creek 020	Big Horn	3 — Serious	100	Fair
Willow Creek RD over Willow Creek 061	Carbon	3 — Serious	100	Poor
Larson Loop RD over Box Elder Creek	Carter	3 — Serious	100	Good
Lander Crossing over Highwood Creek 060	Chouteau	3 — Serious	100	Fair
Coal Creek RD over Coal Creek 027	Daniels	3 — Serious	100	Poor
County Road 226 over Coal Creek 038	Daniels	3 — Serious	100	Poor
Road 217 over Bad Route Creek 028	Dawson	3 — Serious	100	Fair
County Road 524 over N Fk Thirten Mile CR 091	Dawson	3 — Serious	100	Poor
Mt Evans Way over Warm Springs Creek 016	Deer Lodge	3 — Serious	100	Poor
County Road 144 over Dog Creek	Fergus	3 — Serious	100	Good
Bain Street over Wolf Creek	Fergus	3 — Serious	100	Good
Armells Road over Armells Creek	Fergus	3 — Serious	100	Fair
Matovich RD over Mcdonald Creek	Fergus	3 — Serious	100	Good
72 Bench RD over Warm Springs Creek 078	Fergus	3 — Serious	100	Fair
Salt Creek RD over Salt Creek 053	Fergus	3 — Serious	100	Fair
County Road 116 over Armells Creek 115	Fergus	3 — Serious	100	Fair
Scott Crossing over Big Spring Creek 033	Fergus	3 — Serious	100	Good
Beatty RD over South Dry Creek	Gallatin	3 — Serious	100	Good
Old Town RD over Jefferson River 063	Gallatin	3 — Serious	100	Poor
Sullivan Bridge RD over Marias River 030	Glacier	3 — Serious	100	Fair
Sleepy Hollow LN over Prickly Pear Creek	Jefferson	3 — Serious	100	Poor
Indian Butte RD over Louse Creek 037	Judith Basin	3 — Serious	100	Good
Moiese Valley RD over Crow Creek 066	Lake	3 — Serious	100	Good
Fish Hatchery RD over Post Creek 075	Lake	3 — Serious	100	Fair
Augusta-clemons RD over Elk Creek 029	Lewis and Clark	3 — Serious	100	Fair
County Road 811 over Ten Mile Creek 131	Lewis and Clark	3 — Serious	100	Fair
Broadhurst RD over Pondera Coulee 013	Liberty	3 — Serious	100	Fair
Lake Creek RD over Keeler Creek 087	Lincoln	3 — Serious	100	Fair
Seyler LN over Ruby River 019	Madison	3 — Serious	100	Poor
Ledford Creek RD over Ruby River 058	Madison	3 — Serious	100	Fair
Weldon RD over Shade Creek 019	McCone	3 — Serious	100	Fair
Sixteenmile RD over Sixteenmile Creek 044	Meagher	3 — Serious	100	Fair
County Road 128 over Musselshell River 022	Meagher	3 — Serious	100	Poor
Packer Creek RD over Packer Creek 008	Mineral	3 — Serious	100	Fair
Schwartz Creek RD over Clark Fork 093	Missoula	3 — Serious	100	Fair
Boy Scout RD over Clearwater River 083	Missoula	3 — Serious	100	Good
Cold Creek RD over Swan River 045	Missoula	3 — Serious	100	Fair
Elk Creek RD over Shields River 018	Park	3 — Serious	100	Poor
Horse CR RD over Flathead Creek 020	Park	3 — Serious	100	Fair
Hammond Creek RD over Rock Creek 025	Park	3 — Serious	100	Poor
Lower Cottonwood R over Cottonwood Creek 028	Park	3 — Serious	100	Fair
Coal Camp RD over Shields River 015	Park	3 — Serious	100	Fair
Enyart LN over Cottonwood Creek 026	Park	3 — Serious	100	Fair
Old Cat Creek RD over Box Elder Creek 008	Petroleum	2 — Critical	100	Poor
Youth Ranch RD over Whitewater Creek 110	Phillips	3 — Serious	100	Poor
Stoltz RD over Birch Creek 001	Pondera	3 — Serious	100	Fair
Dupuyer Creek RD over Dupuyer Creek 067	Pondera	3 — Serious	100	Fair
Moorhead RD over Powder River 006	Powder River	3 — Serious	100	Good
Meridian RD over Bear Creek 015	Ravalli	3 — Serious	100	Poor
S Shoshone Loop over Skalkaho Creek 043	Ravalli	3 — Serious	100	Fair
Thorning Loop over Rye Creek 064	Ravalli	2 — Critical	100	Fair
County Road 001 over Hardscrabble Creek 041	Richland	3 — Serious	100	Poor
County Road 213 over Four Mile Creek 062	Richland	3 — Serious	100	Fair
County Road 249 over Sheep Creek 061	Roosevelt	3 — Serious	100	Good
Whitepine CR RD over Beaver Creek 022	Sanders	3 — Serious	100	Fair
Emerson RD over Little Bitterroot Rv 092	Sanders	2 — Critical	100	Fair
Lake Creek RD over Lake Creek 078	Sheridan	3 — Serious	100	Good
Swamp Creek RD over Big Timber Creek	Sweet Grass	3 — Serious	100	Good
Bridger Creek Road over Bridger Creek	Sweet Grass	3 — Serious	100	Good
Rock CR Dam RD over Rock Creek 098	Valley	3 — Serious	100	Fair
N Bench RD over West Fork Poplar R 026	Valley	3 — Serious	100	Fair
Logan ST SE over Antelope Creek 019	Wheatland	3 — Serious	100	Fair
Duck Creek RD over Yellowstone River 020	Yellowstone	3 — Serious	100	Fair
Canyon Creek RD over Canyon Creek 042	Yellowstone	3 — Serious	100	Fair
Williams Br RD over Jefferson River 046	Gallatin	3 — Serious	87	Fair
Barney Olsen RD over People`s Creek 105	Blaine	3 — Serious	86	Good
Tusler RD over Yellowstone River 094	Custer	3 — Serious	78	Fair
S 528 over Prairie Elk Creek 021	McCone	3 — Serious	76	Fair
Steel Bridge LN over Red Rock River 084	Beaverhead	3 — Serious	75	Good
Road 223 over Clear Creek 036	Dawson	3 — Serious	74	Fair
21 Mile RD over N Fk Crooked Creek 079	Yellowstone	3 — Serious	68	Fair
Nfsr #487 over S Fk Judith River	Judith Basin	3 — Serious	65	Poor
No Data Entered over Swamp Gul	Granite	2 — Critical	50	Poor
RD 472 over Yaak River	Lincoln	3 — Serious	50	Fair
Fdr 211 over Four Mile Creek	Meagher	3 — Serious	50	Poor
RD 320 over Cedar CR	Mineral	2 — Critical	50	Poor
S 467 over Upper Seven Mile Creek	Dawson	3 — Serious	48	Fair
Nfsr 839 over Belt Creek	Cascade	3 — Serious	46	Poor
County Road 516 over S Fk Burns Creek 063	Dawson	3 — Serious	40	Fair
Pishkun Road over Sun River	Lewis and Clark	2 — Critical	40	Poor
S 243 over Whitewater Creek	Phillips	2 — Critical	39	Poor
Milwaukee RD over Yellowstone River 030	Prairie	3 — Serious	37	Fair
Road 100 S over Big Sandy Creek 019	Hill	3 — Serious	29	Fair
S 332 over Drainage	Rosebud	3 — Serious	29	Fair
River RD over Irrigation Ditch 005	Treasure	2 — Critical	17	Poor
384 Spar Lake Rd. over Spar CR	Lincoln	2 — Critical	10	Poor
No Data Entered over Wise River	Beaverhead	2 — Critical	6	Poor
Fdr 7391 over No Data Entered	Beaverhead	2 — Critical	5	Fair
Road 317 over Drag Creek	Petroleum	3 — Serious	2	Poor
Road 101 over Duval Coulee	Phillips	3 — Serious	0	Poor