NOAA Web Site Link Tides and Currents Home Page Transparent placeholder image

Bench Mark Sheet for 8761678, MICHOUD SUBSTATION, ICWW LA

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


To reach the tidal bench marks from the intersection of U.S. Highway 90 and
Gentilly Road in Orleans Parish, proceed east on Gentilly Road for 4.7 km (2.9
mi) to Paris Road (old State Highway 47), turn right onto Paris Road and go
south for 0.6 km (0.4 mi) to its end at the levee, then turn left and go to the
entrance gate to the Michoud Substation, New Orleans Public Service, Inc.  The
bench marks are located along the perimeter of the substation and under the
State Highway 47 bridge.  The tide gage and staff were located on the SW corner
of the skimmer gate.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  1678 B 1982
                         DESIGNATION:          876 1678 B

MONUMENTATION:           Tidal Station disk                    VM#:         6522
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   30°  0.4' N (  30.00670)          LONGITUDE:  89° 56.2' W ( -89.93670)


The primary bench mark is a disk located along the levee on the south side of
the substation, 77 m (253 ft) SW of bench mark 1678 A 1982, 38 m (125 ft) east
of the SW corner of the chain link fence around the substation, 26 m (84 ft)
south of the south shore of the holding pond at the SW corner of the substation
property, 24 m (80 ft) SE of the SE corner of a concrete pad for pumps, and 1 m
(3 ft) north of the west end of the concrete wall south of the substation.  The
bench mark is set 9 cm (0.3 ft) below ground level, crimped to a stainless steel
rod driven 21.9 m (72 ft) to substantial resistance, and encased in a 4-inch PVC
pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  D 276 1969
                         DESIGNATION:          D 276

MONUMENTATION:           Bench Mark disk                       VM#:         6518
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  BH1083
SETTING CLASSIFICATION:  Concrete bridge pier base             OPUS PID:        
LATITUDE:   30°  0.7' N (  30.01170)          LONGITUDE:  89° 56.4' W ( -89.94000)


The bench mark is a disk set on the top and near the center of the concrete base
for the second State Highway 47 bridge pier south of Gentilly Road at the
intersection of Paris Road (old State Highway 47) and Gentilly Road, 30 m (99
ft) south of the centerline of the eastbound lane of Gentilly Road, and 0.30 m
(1 ft) above road level.



                         BENCH MARK STAMPING:  WES 17 1978
                         DESIGNATION:          876 1678 WES 17

MONUMENTATION:           Survey disk                           VM#:         6519
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   30°  0.4' N (  30.00670)          LONGITUDE:  89° 56.2' W ( -89.93670)


The bench mark is a disk located near the fence corner at the NW corner of the
substation property, 7 m (24 ft) SSW of utility pole #23400 with night light,
and 1 m (2 ft) west of a witness post with sign. The bench mark is set 6 cm (0.2
ft) below ground level, crimped to a copper-clad steel rod driven 24.4 m (80
ft), and encased in a 6-inch plastic pipe.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  WES 19 1978
                         DESIGNATION:          WES 19

MONUMENTATION:           Survey disk                           VM#:         6520
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:  BH3007
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   30°  0.4' N (  30.00670)          LONGITUDE:  89° 56.3' W ( -89.93830)


The bench mark is a disk located on the west side of the substation property,
53.40 m (175.2 ft) NNW of the corner of a hurricane fence on the top of the
levee, 30.60 m (100.4 ft) SSE of the center post of an automatic electric gate,
and 1 m (2 ft) west of a witness post with sign.  The bench mark is set 6 cm
(0.2 ft) below ground level, crimped to a copper-clad steel rod driven 27.4 m
(90 ft), and encased in a 6-inch plastic pipe.



                         BENCH MARK STAMPING:  1678 A 1982
                         DESIGNATION:          876 1678 A

MONUMENTATION:           Tidal Station disk                    VM#:         6521
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete pad                          OPUS PID:        
LATITUDE:   30°  0.4' N (  30.00670)          LONGITUDE:  89° 56.2' W ( -89.93670)


The bench mark is a disk set flush in a concrete gateway pad, on top of the
levee near the skimmer gate, 52 m (172 ft) south of the SW water tower pad, 33 m
(107 ft) NE of the SW corner of a chain link fence around a cooling vent, 20 m
(64 ft) NNW of the chain link fence on the south side around the substation, 14
m (46 ft) NW of the NW corner of the cooler vent scaffolding, and 1 m (4 ft) SSE
of a concrete wall on the levee south of the substation.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  235 R
                         DESIGNATION:          235 R LAGS

MONUMENTATION:           Survey disk                           VM#:         6523
AGENCY:                  Louisiana Geodetic Survey (LAGS)      IDB PID#:  BH1081
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   30°  0.7' N (  30.01170)          LONGITUDE:  89° 56.4' W ( -89.94000)


The bench mark is a disk set in the top of a concrete monument at the
intersection of Paris Road (old State Highway 47) and Gentilly Road, 34 m (113
ft) west of and across Paris Road from bench mark D 276 1969, 30.63 m (100.5 ft)
south of the centerline of the eastbound lane of Gentilly Road, 23 m (76 ft) SE
of a fire hydrant, 19 m (62 ft) west of the centerline of Paris Road, 0.18 m
(0.6 ft) west of a metal witness post, and 0.46 m (1.5 ft) below ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


                            T I D A L   D A T U M S 


Tidal datums at MICHOUD SUBSTATION, ICWW based on:

     LENGTH OF SERIES:      1 YEAR
     TIME PERIOD:           January 1983 - December 1983
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8747437 BAY WAVELAND YC, BAY ST. LOUIS


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     HIGHEST OBSERVED WATER LEVEL (01/20/1983)         =  2.177
     MEAN HIGHER HIGH WATER                     MHHW   =  0.422
     MEAN HIGH WATER                            MHW    =  0.400
     MEAN TIDE LEVEL                            MTL    =  0.212
     MEAN SEA LEVEL                             MSL    =  0.212
     MEAN LOW WATER                             MLW    =  0.024
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (04/02/1983)         = -0.547

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     1678 B 1982                                 3.924    3.524
     D 276 1969                                  1.044    0.644
     WES 17 1978                                -0.114   -0.514
     WES 19 1978                                 0.206   -0.194
     1678 A 1982                                 3.426    3.026
     235 R                                       0.060   -0.340


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8761678                         PUBLICATION DATE:  05/23/2003
Name:       MICHOUD SUBSTATION, ICWW                          
            LA
NOAA Chart: 11369                           Latitude:   30°  0.4' N (  30.00670)
USGS Quad:  LITTLE WOODS                    Longitude:  89° 56.2' W ( -89.93670)


                             D E F I N I T I O N S


Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal
Datum Epoch.  It pertains to local mean sea level and should not be confused
with the fixed datums of North American Vertical Datum of 1988 (NAVD88).

NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum
constraint adjustment of Canadian/Mexican/United States leveling observations.
Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as
the single initial constraint.  NAVD88 replaces NGVD29 as the national
standard geodetic reference for heights.  Bench mark elevations relative to
NAVD88 are available from NGS through the World Wide Web at 
National Geodetic Survey.

NGVD29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded.  NGVD29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads.  NGVD29 was originally derived from a general
adjustment of the first-order leveling networks of the U.S. and Canada after
holding mean sea level observed at 26 long term tide stations as fixed.
Numerous local and wide-spread adjustments have been made since establishment in
1929.  Bench mark elevations relative to NGVD29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at 
National Geodetic Survey.

NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to
local MSL and other tidal datums may not be consistent from one location to
another.

The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique
identifiers for bench marks in the tidal and geodetic databases, respectively.
Each bench mark in either database has a single, unique VM# and/or PID# assigned.
Where both VM# and PID# are indicated, both tidal and geodetic elevations are
available for the bench mark listed. The NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.

The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD88 elevations.
The NAVD88 elevation relationship shown in the table is derived from an average
of several bench mark elevations relative to tide station datum.  As a result of
this averaging, NAVD88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD88 elevations listed for
each bench mark in the NGS database.

Return to Top
Products available at 8761678 MICHOUD SUBSTATION, ICWW, LA

Revised: 08/08/2018
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services