U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 11/08/1985
Station ID: 8667351 SUPERCEDED DATE: 04/21/2003
Name: HUTCHINSON ISLAND, ASHEPOO RIVER
SOUTH CAROLINA
NOAA Chart: 11517 Latitude: 32° 33.1' N
USGS Quad: BENNETTS POINT Longitude: 80° 28.9' W
To reach the tidal bench marks from U.S. Highway 17 at Jacksonboro, proceed 8
miles (13 km) south on U.S. Highway 17 across the Ashepoo River to a rest area
and intersection of State Road S-15-26, proceed 15.6 miles (25.1 km) south on
State Road S-15-26 to its end, then right 0.2 mile (0.3 km) on a dirt road to a
boat landing on the left. By boat, proceed south along Mosquito Creek to the
junction of the Ashepoo River at Bennetts Point, then west on the Ashepoo River
for 1.5 miles (2.4 km) to the dock on Hutchinson Island. The bench marks are
located near the Hilton residence. The tide gage and staff were located on
pilings at the west end of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 7351 A 1976
MONUMENTATION: Survey Disk VM#: 6756
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is near the end of the dock, 112.4 feet (34.3 m) NW of Bench Mark
7351 B 1976, 108.0 feet (32.9 m) NE of Bench Mark 7351 G 1981, 87.0 feet (26.5
m) NNE of the center of the kitchen door of the main house, 38.0 feet (11.6 m)
SW of the SE corner of the dock, and 15.0 feet (4.6 m) ESE of a 4.0-foot (1.2 m)
diameter oak tree. The bench mark is at ground level, crimped to a copper-clad
steel rod driven 32 feet (10 m) to refusal, and encased in a PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 7351 B 1976
MONUMENTATION: Survey Disk VM#: 6757
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is near a stand of four palmetto trees, 201.4 feet (61.4 m) ENE
of Bench Mark 7351 C 1976, 112.4 feet (34.3 m) SE of Bench Mark 7351 A 1976,
56.6 feet (17.3 m) SW of a water oak tree on the river bank, and 10.8 feet (3.3
m) NNE of the four trees. The bench mark is at ground level, crimped to a
copper-clad steel rod driven 40 feet (12 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: 11/08/1985
Station ID: 8667351 SUPERCEDED DATE: 04/21/2003
Name: HUTCHINSON ISLAND, ASHEPOO RIVER
SOUTH CAROLINA
NOAA Chart: 11517 Latitude: 32° 33.1' N
USGS Quad: BENNETTS POINT Longitude: 80° 28.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7351 C 1976
MONUMENTATION: Survey Disk VM#: 6758
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 201.4 feet (61.4 m) WSW of Bench Mark 7351 B 1976, 54.4 feet
(16.6 m) SSE of the SE corner of the screened porch of the house, 31.7 feet (9.7
m) south of the SE corner of the shed attached to the house, 7.7 feet (2.3 m) NE
of a dingle berry tree, and 1.7 feet (0.5 m) NNE of a witness post and sign.
The bench mark is at ground level, crimped to a copper-clad steel rod driven 36
feet (11 m) to refusal, and encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 7351 F 1981
MONUMENTATION: Survey Disk VM#: 6759
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is between the silo and the house, 148.5 feet (45.3 m) WNW of
Bench Mark 7351 C 1976, 119.5 feet (36.4 m) SW of Bench Mark 7351 G 1981, 53.7
feet (16.4 m) west of a 2-foot (0.6 m) diameter pecan tree, and 1.8 feet (0.5 m)
SSW of a witness post and sign. The bench mark is set in a concrete monument,
0.4 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 11/08/1985
Station ID: 8667351 SUPERCEDED DATE: 04/21/2003
Name: HUTCHINSON ISLAND, ASHEPOO RIVER
SOUTH CAROLINA
NOAA Chart: 11517 Latitude: 32° 33.1' N
USGS Quad: BENNETTS POINT Longitude: 80° 28.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7351 G 1981
MONUMENTATION: Survey Disk VM#: 6760
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is west of the house and near the river, 119.5 feet (36.4 m) NE
of Bench Mark 7351 F 1981, 49.8 feet (15.2 m) WSW of an electric meter box on a
wooden post, 41.3 feet (12.6 m) NNE of a 1.5-foot (0.5 m) diameter palmetto
tree, 25.5 feet (7.8 m) NNW of the NW corner of the house, and 3.0 feet (0.9 m)
NNW of the north face of a bell pole. The bench mark is set in a concrete
monument, 0.2 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 11/08/1985
Station ID: 8667351 SUPERCEDED DATE: 04/21/2003
Name: HUTCHINSON ISLAND, ASHEPOO RIVER
SOUTH CAROLINA
NOAA Chart: 11517 Latitude: 32° 33.1' N
USGS Quad: BENNETTS POINT Longitude: 80° 28.9' W
T I D A L D A T U M S
Tidal datums at HUTCHINSON ISLAND, ASHEPOO RIVER based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: MARCH 1977-FEBRUARY 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) = 8.27
MEAN HIGHER HIGH WATER MHHW = 6.51
MEAN HIGH WATER MHW = 6.21
MEAN TIDE LEVEL MTL = 3.20
MEAN LOW WATER MLW = 0.20
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/21/1976) = -2.71
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
7351 A 1976 9.64 3.43
7351 B 1976 8.09 1.88
7351 C 1976 10.64 4.43
7351 F 1981 13.57 7.36
7351 G 1981 11.86 5.65
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 11/08/1985
Station ID: 8667351 SUPERCEDED DATE: 04/21/2003
Name: HUTCHINSON ISLAND, ASHEPOO RIVER
SOUTH CAROLINA
NOAA Chart: 11517 Latitude: 32° 33.1' N
USGS Quad: BENNETTS POINT Longitude: 80° 28.9' 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.