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Details for Benchmark: AU2257

N 29° 53.871 W 090° 02.617 (NAD 83)

Altitude: 3.78

Coordinates may not be exact. Altitude is READJUSTED and location is ADJUSTED. (more info)

Location:
In JEFFERSON county, LA View Original Datasheet
Designation:
JPW 70 B
Marker Type:
bench mark disk
Setting:
abutments and piers of large bridges
Stability:
Probably hold position/elevation well.

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Spotted this one on my way to get lunch at Taco Bell today; the bright, neon circle drawn around it drew my attention to it! BM in good condition right there on the bridge; will post pic as soon as I'm able.

[Photos:]
photoBM on bridge...

Documented History (by the NGS)

01/01/1986 by LADTD (MONUMENTED)
DESCRIBED BY LA TRANSP AND DEV 1986 (UNK) THE STATION IS LOCATED AT THE EAST BOUNDRY OF GRETNA, AT THE JUNCTION OF STATE HIGHWAY 23 AND VERRET CANAL IN THE BRIDGE ABUTMENT ONER THE CANAL. OWNERSHIP--LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT. TO REACH THE STATION FROM THE JUNCTION OF U.S. HIGHWAY 90 BUSINESS AND STATE HIGHWAY 23 IN GRETNA, GO SOUTHEAST FOR 1.79 KM (1.1 MI) ON HIGHWAY 23 TO THE SOUTHEAST END OF THE BRIDGE OVER THE VERRET CANAL AND THE STATION ON THE RIGHT IN THE BRIDGE ABUTMENT. THE STATION IS A STANDARD JEFFERSON PARISH DISK STAMPED---JPW 70 B--- SET IN A DRILL HOLE IN THE BRIDGE ABUTMENT. 2.0 METERS (0.7 FT) NORTHWEST FROM THE SOUTHEAST END OF THE BANNISTER OF THE BRIDGE.
01/01/1986 by LA-051 (GOOD)
RECOVERY NOTE BY JEFFERSON PARISH LOUISIANA 1986 IN GRETNA. THE STATION IS LOCATED ABOUT 3.2 KM (2.0 MI) NORTHWEST OF THE CITY HALL IN GRETNA, OWNERSHIP--THE BRIDGE ACROSS VERRET CANAL, TO REACH THE STATION FROM THE JUNCTION OF THE FRONTAGE ROAD OF THE WEST BANK EXPRESSWAY AND BELLE CHASSE HWY (LA HWY 23), GO SOUTHEAST FOR 1.52 KM (0.95 MI) ON THE SAID HWY TO THE MARK SET ON TOP OF THE SOUTHWEST BRIDGE ABUTTMENT OF THE BRIDGE ACROSS VERRET CANAL. THE STATION IS A STANDARD JPDPU DISK STAMPED JPW-70-B, SET INTO THE BRIDGE ABUTTMENT, 0.5 METERS (1.64 FT) EAST FROM THE BRIDGE FENCE. THE STATION WAS USED TO OBSERVE GRAVITY BY THE UNIVERSITY OF NEW ORLEANS IN SPRING OF 1986.
06/25/1987 by (GOOD)
RECOVERED 1987 RECOVERED IN GOOD CONDITION.
06/30/1987 by (GOOD)
RECOVERED 1987 RECOVERED IN GOOD CONDITION.
11/28/1994 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1994 (GAS) IN TERRYTOWN, AT THE INTERSECTION OF BELLE CHASE HIGHWAY AND WHITNEY AVENUE, IN TOP OF AND 0.5 M (1.6 FT) NORTH OF THE SOUTH END OF THE SOUTHEAST CONCRETE ABUTMENT OF THE HIGHWAY BRIDGE SPANNING VERRET CANAL, 7.2 M (23.6 FT) WEST OF THE EXTENDED CENTERLINE OF THE AVENUE, 4.5 M (14.8 FT) SOUTHWEST OF THE CENTERLINE OF THE SOUTHEAST BOUND LANES OF THE HIGHWAY, AND 0.3 M (1.0 FT) ABOVE THE LEVEL OF THE HIGHWAY.

Control Text

  • The horizontal coordinates were established by GPS observations and adjusted by the National Geodetic Survey in January 1993.
  • The orthometric height was determined by differential leveling and adjusted by the National Geodetic Survey in February 1994. * This is a READJUSTED BENCH MARK height. Code A indicates a distribution rate of 0.0 thru 1.0 mm/km. The height was derived from older observations constrained to new heights in a crustal motion area. The height is approximate in relation to other heights in its vicinity.
  • The X, Y, and Z were computed from the position and the ellipsoidal ht.
  • The Laplace correction was computed from DEFLEC99 derived deflections.
  • The ellipsoidal height was determined by GPS observations and is referenced to NAD 83.
  • The geoid height was determined by GEOID99.
  • The dynamic height is computed by dividing the NAVD 88 geopotential number by the normal gravity value computed on the Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 degrees latitude (G = 980.6199 gals.).
  • The modeled gravity was interpolated from observed gravity values.

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