Superseded Bench Mark Sheet for 8673381, HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA

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:  05/13/1988
Station ID: 8673381                                SUPERCEDED DATE:   04/21/2003
Name:       THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER      
            GEORGIA
NOAA Chart: 11511                                  Latitude:         31° 41.7' N
USGS Quad:  SEABROOK                               Longitude:        81° 16.3' W


To reach the tidal bench marks from the intersection of Interstate Highway 95
and State Road 38, proceed east on State Road 38 for 8.2 miles (13.2 km) to the
road leading to Colonels Island Marina, then south on the road leading to
Colonels Island Marina for 1.6 miles (2.6 km) to the marina.  The bench marks
are located on the marina grounds.  The tide gage and staff were located on a
pier on the NW corner of the marina.


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


                 PRIMARY BENCH MARK STAMPING:  3381 A 1977

MONUMENTATION:           Survey Disk                               VM#:     4760
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified Rod


The bench mark is near the NW corner of the southernmost boat house, 54.8 feet
(16.7 m) NE of a group of four oak trees east of Timmons River, and 33.3 feet
(10.1 m) north of the NE corner of a small wooden building.  The bench mark is
crimped to an unspecified rod driven 64 feet (20 m) to refusal and encased in a
PVC pipe and concrete kickblock.



                         BENCH MARK STAMPING:  3381 B 1977

MONUMENTATION:           Survey Disk                               VM#:     4761
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified Rod


The bench mark is near the SE corner of the northernmost boat house, 283 feet
(86 m) east of Bench Mark 3381 A 1977, and 29.5 feet (9.0 m) west of the
centerline of the road leading to the marina.  The bench mark is crimped to an
unspecified rod driven 6 feet (2 m) to refusal and encased in a PVC pipe and
concrete kickblock.

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

                                                   PUBLICATION DATE:  05/13/1988
Station ID: 8673381                                SUPERCEDED DATE:   04/21/2003
Name:       THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER      
            GEORGIA
NOAA Chart: 11511                                  Latitude:         31° 41.7' N
USGS Quad:  SEABROOK                               Longitude:        81° 16.3' W


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


                         BENCH MARK STAMPING:  3381 C 1977

MONUMENTATION:           Survey Disk                               VM#:     4762
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified Rod


The bench mark is NE of a cinder block cottage, 173.3 feet (52.8 m) south of
Bench Mark 3381 B 1977, 58.3 feet (17.8 m) NE of the NE corner of the cinder
block cottage, and 31.8 feet (9.7 m) west of the centerline of the road leading
to the marina.  The bench mark is 0.2 foot (0.1 m)  above ground level, crimped
to an unspecified rod driven 16 feet (4.9 m) to refusal, and encased in a PVC
pipe and concrete kickblock.



                         BENCH MARK STAMPING:  3381 D 1977

MONUMENTATION:           Survey Disk                               VM#:     4763
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified Rod


The bench mark is south of a cinder block cottage, 100.7 feet (30.7 m) SSW of
Bench Mark 3381 C 1977, 55.5 feet (16.9 m) west of the centerline of the road
leading to the marina, and 19.4 feet (5.9 m) ESE of the SE corner of the cinder
block cottage.  The bench mark is 0.2 foot (0.1 m) above ground level, crimped
to an unspecified rod driven 16 feet (5 m) to refusal, and encased in a PVC pipe
and a concrete kickblock.

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

                                                   PUBLICATION DATE:  05/13/1988
Station ID: 8673381                                SUPERCEDED DATE:   04/21/2003
Name:       THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER      
            GEORGIA
NOAA Chart: 11511                                  Latitude:         31° 41.7' N
USGS Quad:  SEABROOK                               Longitude:        81° 16.3' W


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


                         BENCH MARK STAMPING:  3381 E 1977

MONUMENTATION:           Survey Disk                               VM#:     4764
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified Rod


The bench mark is ESE of the marina store, 158 feet (48 m) west of Bench Mark
3381 D 1977, and 53.6 feet (16.3 m) ESE of the SE corner of the marina store. 
The bench mark is crimped to an unspecified rod driven 8 feet (2 m) to refusal,
and encased in a PVC pipe and a concrete kickblock.

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

                                                   PUBLICATION DATE:  05/13/1988
Station ID: 8673381                                SUPERCEDED DATE:   04/21/2003
Name:       THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER      
            GEORGIA
NOAA Chart: 11511                                  Latitude:         31° 41.7' N
USGS Quad:  SEABROOK                               Longitude:        81° 16.3' W


                            T I D A L   D A T U M S 


Tidal datums at THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           MAY 1977
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8720030 FERNANDINA BEACH, FL


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

     HIGHEST OBSERVED WATER LEVEL (06/01/1977)         =   9.86
     MEAN HIGHER HIGH WATER                     MHHW   =   8.00
     MEAN HIGH WATER                            MHW    =   7.64
     MEAN TIDE LEVEL                            MTL    =   3.94
     MEAN LOW WATER                             MLW    =   0.24
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (05/04/1977)         =  -1.64



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     3381 A 1977                                16.07      8.43
     3381 B 1977                                18.69     11.05
     3381 C 1977                                19.48     11.84
     3381 D 1977                                19.32     11.68
     3381 E 1977                                18.50     10.86


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

                                                   PUBLICATION DATE:  05/13/1988
Station ID: 8673381                                SUPERCEDED DATE:   04/21/2003
Name:       THE HALFMOON, COLONELS ISLAND, TIMMONS RIVER      
            GEORGIA
NOAA Chart: 11511                                  Latitude:         31° 41.7' N
USGS Quad:  SEABROOK                               Longitude:        81° 16.3' 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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