Superseded Bench Mark Sheet for 8761305, Shell Beach LA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:  01/21/1988
Station ID: 8761305                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL BEACH, LAKE BORGNE                          
            LOUISIANA
NOAA Chart: 11371                                  Latitude:         29° 52.1' N
USGS Quad:  YSCLOSKEY                              Longitude:        89° 40.4' W


To reach the tidal bench marks from the boat launch facilities near the north
end of State Highway 46 in Shell Beach, proceed by boat north on Bayou Yscloskey
and across the Gulf Outlet Canal for 1.1 miles (1.8 km) to the ruins at Old
Shell Beach.  The bench marks are located on the ruins to the east of Bayou
Yscloskey, and along the old road paralleling Bayou Yscloskey.  The tide gage
and staff were located on a 22 x 14-foot (7x4 m) concrete platform at the mouth
of the bayou.


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


                 PRIMARY BENCH MARK STAMPING:  1305 F 1982

MONUMENTATION:           Survey Disk                               VM#:     7147
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is south of the shore of Lake Borgne along the abandoned paved
road leading to Old Shell Beach, 46 feet (14 m) east of the approximate high
water mark on the east bank of Bayou Yscloskey, 32 feet (10 m) south of the NE
corner of a concrete foundation, and 1 foot (0.3 m) east of the SE corner of the
foundation.  The bench mark is at ground level, crimped to a stainless steel rod
driven 76 feet (23 m) to substantial resistance, and encased in a 4-inch PVC
pipe and concrete kickblock.



                         BENCH MARK STAMPING:  1305 C 1980

MONUMENTATION:           Survey Disk                               VM#:     7144
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is set flush in the west end of a 400-foot (122 m) long concrete
dock, 15 feet (5 m) east of the west end of the dock, 14 feet (4 m) south of the
north edge of the dock, 12 feet (4 m) ESE of the westernmost gun mount on the
dock, and 8 feet (2 m) WSW of the second westernmost gun mount.

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

                                                   PUBLICATION DATE:  01/21/1988
Station ID: 8761305                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL BEACH, LAKE BORGNE                          
            LOUISIANA
NOAA Chart: 11371                                  Latitude:         29° 52.1' N
USGS Quad:  YSCLOSKEY                              Longitude:        89° 40.4' W


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


                         BENCH MARK STAMPING:  1305 D 1980

MONUMENTATION:           Survey Disk                               VM#:     7145
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is set flush in the center of the 400-foot (122 m) long dock, 200
feet (61 m) west of the east end of the dock, 12 feet (4 m) SSW of the north
edge of the dock, 10 feet (3 m) NNE of the south edge of the dock, and   1 foot
(0.3 m) south of a gun mount.



                         BENCH MARK STAMPING:  1305 E 1980

MONUMENTATION:           Survey Disk                               VM#:     7146
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is set flush in the east end of the 400-foot (122 m) long dock,
41.5 feet (12.6 m) west of the east end of the dock, 17 feet (5 m) SSW of the
north edge of the dock, and 7.5 feet (2.3 m) SE of a gun mount.



                         BENCH MARK STAMPING:  1305 G 1982

MONUMENTATION:           Survey Disk                               VM#:     7148
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is 209 feet (64 m) south of Bench Mark 1305 F 1982, 27 feet (8 m)
east of the approximate high water mark on the east bank of Bayou Yscloskey, and
17 feet (5 m) east of the centerline of the old paved road.  The bench mark is
at ground level, crimped to a stainless steel rod driven 76 feet (23 m) 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  3 of  5

                                                   PUBLICATION DATE:  01/21/1988
Station ID: 8761305                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL BEACH, LAKE BORGNE                          
            LOUISIANA
NOAA Chart: 11371                                  Latitude:         29° 52.1' N
USGS Quad:  YSCLOSKEY                              Longitude:        89° 40.4' W


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


                         BENCH MARK STAMPING:  1305 H 1982

MONUMENTATION:           Survey Disk                               VM#:     7149
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is 234 feet (71 m) south of Bench Mark 1305 G 1982, 52 feet (16
m) SW of the concrete ruins, 34 feet (10 m) ESE of the approximate high water
mark on the east bank of Bayou Yscloskey, and 14 feet (4 m) ESE of the
centerline of the abandoned road leading to Old Shell Beach.  The bench mark is
at ground level, crimped to a stainless steel rod driven 76 feet (23 m) 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  4 of  5

                                                   PUBLICATION DATE:  01/21/1988
Station ID: 8761305                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL BEACH, LAKE BORGNE                          
            LOUISIANA
NOAA Chart: 11371                                  Latitude:         29° 52.1' N
USGS Quad:  YSCLOSKEY                              Longitude:        89° 40.4' W


                            T I D A L   D A T U M S 


Tidal datums at SHELL BEACH, LAKE BORGNE based on:

     LENGTH OF SERIES:      12 MONTHS
     TIME PERIOD:           JANUARY-DECEMBER 1983
     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 (01/20/1983)         =   7.28
     MEAN HIGHER HIGH WATER                     MHHW   =   1.45
     MEAN HIGH WATER                            MHW    =   1.38
     MEAN TIDE LEVEL                            MTL    =   0.73
     MEAN LOW WATER                             MLW    =   0.09
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (04/02/1983)         =  -1.26



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     1305 F 1982                                 2.09      0.71
     1305 C 1980                                 4.88      3.50
     1305 D 1980                                 5.53      4.15
     1305 E 1980                                 5.43      4.05
     1305 G 1982                                 2.49      1.11
     1305 H 1982                                 2.19      0.81


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

                                                   PUBLICATION DATE:  01/21/1988
Station ID: 8761305                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL BEACH, LAKE BORGNE                          
            LOUISIANA
NOAA Chart: 11371                                  Latitude:         29° 52.1' N
USGS Quad:  YSCLOSKEY                              Longitude:        89° 40.4' 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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