Superseded Bench Mark Sheet for 8760595, BRETON ISLAND LA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  01/30/1990
Station ID: 8760595                                SUPERCEDED DATE:   04/21/2003
Name:       BRETON ISLAND, BRETON SOUND                       
            LOUISIANA
NOAA Chart: 11363                                  Latitude:         29° 29.6' N
USGS Quad:  BRETON ISLANDS                         Longitude:        89° 10.4' W


To reach the tidal bench marks from Venice, proceed by boat across the
Mississippi River, then NE on Baptiste Collette Bayou for 8 miles (13 km) to the
end of the channel markers, then NE across Breton Sound for 11 miles (18 km) to
the Kerr-McGee oil facility on Breton Island.  The bench marks are on the
grounds of the oil facility and in the marsh to the north.  The tide gage and
staff were on the west side and NW corner, respectively, of the T-shaped wooden
dock.


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


                 PRIMARY BENCH MARK STAMPING:  0595 A 1980

MONUMENTATION:           Survey Disk                               VM#:     7089
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is in the marsh NE of the circular bulkhead around the oil
facility, 200 feet (61 m) NNE of Corps of Engineers (COE) Bench Mark NO STAMPING
1, 182 feet (55 m) NNE of the bulkhead around the oil facility, 98 feet (30 m)
north of the NE anchor pile of the radio tower guy wire system, and 80 feet (24
m) west of the west shoreline of the bay inside the east side of the island. 
The bench mark is 0.3 foot (0.1 m) below ground level, crimped to a stainless
steel rod driven 50 feet (15 m) to refusal, and encased in a 4-inch PVC pipe.



                         BENCH MARK STAMPING:  0595 B 1980

MONUMENTATION:           Survey Disk                               VM#:     7090
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is in the marsh, 385 feet (117 m) NNE of the west radio tower guy
wire anchor, 369 feet (112 m) north of COE Bench Mark NO STAMPING 2, 360 feet
(110 m) north of the circular bulkhead around the oil facility, 311 feet (95 m)
NNW of the NE radio tower guy wire anchor, 219 feet (67 m) NNW of Bench Mark
0595 A 1980, and 58 feet (18 m) south of the shoreline of the small bay which is
north of the oil facility.  The bench mark is 0.2 foot (0.1 m) below ground
level, crimped to a stainless steel rod driven 55 feet (17 m) to refusal, and
encased in a 4-inch PVC pipe.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                   PUBLICATION DATE:  01/30/1990
Station ID: 8760595                                SUPERCEDED DATE:   04/21/2003
Name:       BRETON ISLAND, BRETON SOUND                       
            LOUISIANA
NOAA Chart: 11363                                  Latitude:         29° 29.6' N
USGS Quad:  BRETON ISLANDS                         Longitude:        89° 10.4' W


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


                         BENCH MARK STAMPING:  0595 C 1980

MONUMENTATION:           Survey Disk                               VM#:     7091
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is in the marsh, 350 feet (107 m) WNW of the NW radio tower guy
wire anchor, 306 feet (93 m) NW of COE Bench Mark NO STAMPING 2, 281 feet (86 m)
NNW of the circular bulkhead around the oil facility, 251 feet (77 m) SW of
Bench Mark 0595 B 1980, 140 feet (43 m) north of the west anchor pile of the
radio tower, and 59 feet (18 m) north of the NW end of the facility.  The bench
mark is 0.3 foot (0.1 m) below ground level, crimped to a stainless steel rod
driven 60 feet (18 m) to refusal, and encased in a 4-inch PVC pipe.



                         BENCH MARK STAMPING:  BRETON RM NO 2

MONUMENTATION:           Survey Disk                               VM#:     7092
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is on the west side of the oil facility near the NW radio tower
guy wire anchor, 17 feet (5 m) NW of the NW corner of a generator house, and 2
feet (1 m) east of the bulkhead.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                   PUBLICATION DATE:  01/30/1990
Station ID: 8760595                                SUPERCEDED DATE:   04/21/2003
Name:       BRETON ISLAND, BRETON SOUND                       
            LOUISIANA
NOAA Chart: 11363                                  Latitude:         29° 29.6' N
USGS Quad:  BRETON ISLANDS                         Longitude:        89° 10.4' W


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


                         BENCH MARK STAMPING:  NO STAMPING 1

MONUMENTATION:           Survey Disk                               VM#:     7093
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in a concrete monument at the foot of the dock on the east
side of the oil facility, 66.5 feet (20.3 m) NE of the centerline of a concrete
ramp leading SSE from the island, 21.8 feet (6.6 m) south of the centerline of
the wood ramp leading east to the wooden dock, 18.5 feet (5.6 m) ESE of the NE
corner of the metal generator building, 5.0 feet (1.5 m) west of the outside
face of the circular bulkhead around the oil facility, and 0.5 foot (0.2 m)
above ground level.



                         BENCH MARK STAMPING:  NO STAMPING 2

MONUMENTATION:           Survey Disk                               VM#:     7094
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is on the north side of the oil facility, 131.5 feet (40.1 m) SW
of the NE guy wire post for the antenna tower on the west side of the island,
93.8 feet (28.6 m) NE of the center of the concrete base of the antenna tower,
13.6 feet (4.1 m) NE of the NW corner of the metal walkway along the north side
of the crew quarters, 7.6 feet (2.3 m) south of the outside face of the circular
bulkhead around the oil facility, and 0.7 foot (0.2 m) above ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                   PUBLICATION DATE:  01/30/1990
Station ID: 8760595                                SUPERCEDED DATE:   04/21/2003
Name:       BRETON ISLAND, BRETON SOUND                       
            LOUISIANA
NOAA Chart: 11363                                  Latitude:         29° 29.6' N
USGS Quad:  BRETON ISLANDS                         Longitude:        89° 10.4' W


                            T I D A L   D A T U M S 


Tidal datums at BRETON ISLAND, BRETON SOUND based on:

     LENGTH OF SERIES:      9 MONTHS
     TIME PERIOD:           MARCH - DECEMBER 1981
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8747437 BAY WAVELAND, MS


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

     HIGHEST OBSERVED WATER LEVEL (05/05/1981)         =   2.70
     MEAN HIGHER HIGH WATER                     MHHW   =   1.32
     MEAN HIGH WATER                            MHW    =   1.30
     MEAN TIDE LEVEL                            MTL    =   0.66
     MEAN LOW WATER                             MLW    =   0.01
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (02/04/1981)         =  -1.30



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     0595 A 1980                                 1.75      0.45
     0595 B 1980                                 1.60      0.30
     0595 C 1980                                 2.93      1.63
     BRETON RM NO 2                              6.31      5.01
     NO STAMPING 1                               7.42      6.12
     NO STAMPING 2                               7.23      5.93


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

                                                   PUBLICATION DATE:  01/30/1990
Station ID: 8760595                                SUPERCEDED DATE:   04/21/2003
Name:       BRETON ISLAND, BRETON SOUND                       
            LOUISIANA
NOAA Chart: 11363                                  Latitude:         29° 29.6' N
USGS Quad:  BRETON ISLANDS                         Longitude:        89° 10.4' W


                             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 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.

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