Superseded Bench Mark Sheet for 8666699, BLUFF POINT, WADMALAW RIVER SC

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  08/20/1991
Station ID: 8666699                                SUPERCEDED DATE:   04/21/2003
Name:       BEARS BLUFF, WADMALAW ISLAND, WADMALAW RIVER      
            SOUTH CAROLINA
NOAA Chart: 11522                                  Latitude:         32° 38.8' N
USGS Quad:  ADAMS RUN                              Longitude:        80° 15.4' W


To reach the tidal bench marks from the Johns Island post office proceed west
along State Highway 700 for 5.8 miles (9.3 km) to County Road S-10-316, continue
NW along County Road S-10-316 for 8.8 miles (14.2 km) to the end of the pavement
at the entrance to U.S. Fish & Wildlife Orangeburg National Fish Hatchery, Bears
Bluff Station.  Continue SW for 0.2 mile (0.3 km) along a sand road that runs
parallel with a chain link fence, and then 0.1 mile (0.2 km) north through a
chain link gate to the office.  The bench marks are along a sand road that
follows the river.  The tide gauge and staff were at the end of the pier on the
Wadmalaw River.


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


                 PRIMARY BENCH MARK STAMPING:  6699 A 1977

MONUMENTATION:           Survey Disk                               VM#:     4339
AGENCY:                                                            PID#:  CK2579
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is at the shore end of the pier, 18 feet (5 m) NNW of the edge of
a small fish pond, 10.0 feet (3.0 m) NNE of the centerline of the sand road, and
3.6 feet (1.1 m) SSW of a 6-foot (2 m) high sea wall.  The bench mark is level
with the ground, crimped to a copper-clad steel rod driven 40 feet (12 m) to
refusal, and encased in a PVC pipe and concrete kickblock.



                         BENCH MARK STAMPING:  6699 B 1977

MONUMENTATION:           Survey Disk                               VM#:     4340
AGENCY:                                                            PID#:  CK2578
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is at the sand road running along the river from the pier to the
southern boundary of the station, 23 feet (7 m) east of the approximate edge of
a 50-foot (15 m) high river bank, 20.5 feet (6.2 m) west of the centerline of
the road, 9.4 feet (2.9 m) NW of the 4-foot (1 m) diameter blazed cedar tree,
and 1 foot (0.3 m) ENE of a witness post.  The bench mark is 2.0 feet (0.6 m)
above road level, crimped to a copper-clad steel rod driven 28 feet (9 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  4

                                                   PUBLICATION DATE:  08/20/1991
Station ID: 8666699                                SUPERCEDED DATE:   04/21/2003
Name:       BEARS BLUFF, WADMALAW ISLAND, WADMALAW RIVER      
            SOUTH CAROLINA
NOAA Chart: 11522                                  Latitude:         32° 38.8' N
USGS Quad:  ADAMS RUN                              Longitude:        80° 15.4' W


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


                         BENCH MARK STAMPING:  6699 C 1977

MONUMENTATION:           Survey Disk                               VM#:     4341
AGENCY:                                                            PID#:  CK2577
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is at the sand road running along the river from the pier to the
southern boundary of the station, 16.8 feet (5.1 m) SSE of a 7.5-foot (2.3 m)
diameter blazed oak tree, 15 feet (5 m) west of the centerline of the sand road,
and 14.6 feet (4.4 m) north of a lone 7.5-foot (2.3 m) diameter cedar tree.  The
bench mark is level with the sand road, crimped to a copper-clad steel rod
driven 30 feet (9 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  3 of  4

                                                   PUBLICATION DATE:  08/20/1991
Station ID: 8666699                                SUPERCEDED DATE:   04/21/2003
Name:       BEARS BLUFF, WADMALAW ISLAND, WADMALAW RIVER      
            SOUTH CAROLINA
NOAA Chart: 11522                                  Latitude:         32° 38.8' N
USGS Quad:  ADAMS RUN                              Longitude:        80° 15.4' W


                            T I D A L   D A T U M S 


Tidal datums at BEARS BLUFF, WADMALAW ISLAND, WADMALAW RIVER based on:

     LENGTH OF SERIES:      11 MONTHS
     TIME PERIOD:           FEBRUARY 1977-JANUARY 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8665530 CHARLESTON


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

     HIGHEST OBSERVED WATER LEVEL (06/01/1977)         =   8.69
     MEAN HIGHER HIGH WATER                     MHHW   =   6.75
     MEAN HIGH WATER                            MHW    =   6.42
     MEAN TIDE LEVEL                            MTL    =   3.32
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   3.08
     MEAN LOW WATER                             MLW    =   0.22
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (01/09/1978)         =  -2.91

   * NGVD reference based on elevations published in Quad L24757, 1985, and NOS
     leveling of 1984. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     6699 A 1977                                11.09      4.67
     6699 B 1977                                17.66     11.24
     6699 C 1977                                21.03     14.61


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

                                                   PUBLICATION DATE:  08/20/1991
Station ID: 8666699                                SUPERCEDED DATE:   04/21/2003
Name:       BEARS BLUFF, WADMALAW ISLAND, WADMALAW RIVER      
            SOUTH CAROLINA
NOAA Chart: 11522                                  Latitude:         32° 38.8' N
USGS Quad:  ADAMS RUN                              Longitude:        80° 15.4' 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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