**I-255 (Jefferson Barracks Bridge) over Mississippi River**

**near St. Louis, MO**

SITE DESCRIPTION:

The I-255 (Jefferson Barracks Bridge) over the Mississippi River is
located just south of St. Louis, Missouri. The river in this reach
varies from 2,000 to 2,500 ft wide. The thalweg crosses from the left
(Illinois) bank to the right (Missouri) bank upstream from the bridge
and follows the right bank through the bridge and crosses back to the
left bank downstream from the bridge. The channel alignment is a very
gentle bend with a high bluff along the right upstream bank. The left
floodplain is about a mile wide and is predominately farmland. A levee
restricts the extent of the left floodplain. The bridge is 4,003 ft long
and is supported by 14 piers. Piers are numbered from right to left
(Missouri to Illinois). The navigation channel is along the right
(Missouri) bank. Piers 12 and 13 support the navigation span of 910 ft.
Piers 8 through 10 are set on a large sand bar along the left (Illinois)
bank, which is exposed during very low flow. Dikes have been installed
by the U.S. Army Corps of Engineers along the left bank both upstream
and downstream of the bridge to maintain a sufficient depth in the
navigation channel during low flow.

DESCRIPTION OF REFERENCE POINTS:

The water-surface elevations were measured at a staff gage about 1,000
ft downstream from the bridge. The staff gage had a datum of 377.7 ft
MSL. All elevations are presented in ft MSL.

Horizontal positioning of the velocity profiles and bathymetry was
measured using a range-azimuth positioning system. The horizontal
coordinates are in an arbitrary local grid. The bridge was correctly
positioned in the grid by surveying 2 or more piers from each instrument
setup location. All horizontal coordinates are in ft.

CONTACT:

David Mueller

U.S. Geological Survey

9818 Bluegrass Parkway

Louisville, KY 40299

PUBLICATIONS:

Mueller, D.S., Landers, M.N., and Fischer, E.F., 1995, Scour
measurements at bridge sites during 1993 Upper Mississippi River Basin
flood: Transportation Research Record 1483, p. 47-55.

Foster, J.E., 1988, Jefferson Barracks Brige movable-bed model study:
U.S. Army Corpse of Engineers Waterways Experiment Station Miscellaneous
Paper HL-88-7.

BED MATERIAL COMMENTS:

No bed material samples were collected at this site. The boring logs
show sand to be predominant. Bed material samples size distributions
presented in Holmes, R.R., Jr., 1993, Sediment transport in the lower
Missouri and the central Mississippi Rivers, June 26 through September
14: U.S. Geological Survey Circular 1120-I were fairly consistent for
samples at St. Louis, Missouri and at Chester, Illinois. The bed
material sizes reported herein were interpolated from this report.

DESCRIPTION FOR THIS BRIDGE:

All of the piers were surveyed during the flood, but scour holes were
only identified at piers 8 and 9. Scans of the bridge plans have been
included for piers 7 through 12. Pier 12 is part of the navigation span
and has a different design than piers 7 through 11. Piers 7 through 11
are all similar in design, but the elevations of the various components
of the piers are different. Each pier consists of two square caissons
connected by a web wall near elevation 416 ft MSL. The piers are tapered
slightly in the direction of flow. The caissons and web wall rest on a
wider square-nosed pedestal, that rests on a wider square-nosed footing,
that rests on a wider square-nosed seal, that is supported by H-piles.

PIER SCOUR COMMENTS:

An initial check survey of the bridge on July 14, 1993 resulted in the
establishment of this site as a detailed study site. Detailed
bathymetric data were collected on July 17 and 19, 1993; however, only
average approach velocities were measured on these dates because of the
inability of a 1,200 kHz BB-ADCP to measure velocities accurately under
these extreme conditions. Detailed bathymetric and three-dimensional
velocities were measured at this site on August 17 and September 16,
1993. No times are recorded with the measurements as a detailed
measurement takes a half to a full day to complete.

The water-surface elevations initially peaked at an elevation of 420.7
on July 19, but additional rain resulted in a slightly higher peak in
the following weeks. No scour data were collected during this second
peak.

The sediment transport upstream from pier 9 was characterized by 6 to 8
ft dunes; upstream from pier 8 dunes were somewhat smaller.

The depth of scour for each measurement was measured from a reference
surface that was subjectively established based on a visual analysis of
a 3-dimensional representation of the site. The presence of dunes made
identification of the reference surface difficult and uncertainty is the
major contributing factor to the accuracy presented for each
measurement.

The configuration of the piers may have reduced scour due the
stair-stepped design. However, scour reached several feet below the top
of the seals at piers 8 and 9 but did not threaten the stability of the
bridge.

ABUTMENT SCOUR COMMENTS: none

CONTRACTION SCOUR COMMENTS: none

HYDROGRAPH:

The hydrograph from the gage located in downtown St. Louis on the Poplar
Street Bridge is provided in the "Hydrograph" worksheet of JB.xls

OTHER FILES

JB.xls -- contains the following worksheets

Summary -- Summary of bridge and scour characterists

Hydrograph -- Hydrograph from gage at downtown St. Louis

071493 -- Bathymetry for July 14, 1993

071793 -- Bathymetry for July 17, 1993

071993 -- Bathymetry for July 19, 1993

081793 -- Bathymetry for August 17, 1993

081793-3D -- 3-dimensional velocities collected on August 17, 1993

081793-DI -- depth integrated velocities collected on August 17, 1993

091693- Bathymetry for September 16, 1993

091693-3D -- 3-dimensional velocities collected on September 16, 1993

091693-DI -- depth integrated velocities collected on September 16, 1993

Definition of heading for ADCP files

Transect -- transect file number

Ensemble -- ensemble number (averaged every 5 ensembles)

BinElev -- Elevation to center of depth cell in ft MSL

BinDepth -- Depth to center of depth cell in ft

U -- u-velocity component (east) in ft/sec

V -- v-velocity component (north) in ft/sec

W -- vertical velocity component in ft/sec

X-SP -- x location in State Plane coordinates Missouri East NAD-27

Y-SP -- y location in State Plane coordinate Missouri East NAD-27

Mag -- velocity magnitude in ft/sec

Dir -- velocity direction referenced to north

UnitQ -- discharge contain in depth cell

BotElev -- Elevation of streambed in ft MSL

X-Loc -- x location in local coordinate system

Y-Loc -- y location in local coordinate system

U-Loc -- u-velocity component in x direction in local coordinate system

V-Loc -- v-velocity component in y direction in local coordinate system

Dir-Loc -- velocity direction referenced to the local coordinate system

Aerial-1.jpg -- Satellite image of river reach

Aerial-2.jpg -- Satellite image of study area

Topo.jpg -- scan of USGS topographic map

Profile.jpg -- profile view of bridge from bridge plans

Plan.jpg -- plan view of bridge from bridge plans

Pier12W-1.jpg -- Pier details for pier 12

Pier12W-2.jpg -- Pier details for pier 12

Pier12W-3.jpg -- Pier details for pier 12

Pier12W-4.jpg -- Pier details for pier 12

Pier11W-1.jpg -- Pier details for pier 11

Pier11W-2.jpg -- Pier details for pier 11

Pier10W-1.jpg -- Pier details for pier 10

Pier10W-2.jpg -- Pier details for pier 10

Pier9W-1.jpg -- Pier details for pier 9

Pier9W-2.jpg -- Pier details for pier 9

Pier8W-1.jpg -- Pier details for pier 8

Pier8W-2.jpg -- Pier details for pier 8

Pier7W.jpg -- Pier details for pier 7

Photo-1.jpg -- Photograph looking from left descending abutment across
upstream face of bridge.

Photo-2.jpg -- Photograph from left descending abutment looking across
stream between bridges.

Photo-2.jpg -- Photograph of pier 12 during flood

P8-BoringB-10.jpg -- Soils boring at downstream bridge near pier 8

P8-BoringH-11.jpg -- Soils boring at upstream bridge near pier 8

P9-BoringB-11.jpg -- Soils boring at downstream bridge near pier 9

P9-BoringH-10.jpg -- Soils boring at upstream bridge near pier 9

Bridge-Loc.dxf -- DXF file of bridge (piers 7-13) in local coordinates

Pier9.jpg -- 3-dimensional graphic showing streambed and pier

Pier8.jpg -- 3-dimensional graphic showing streambed and pier