U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 11/18/1983
Station ID: 8667482 SUPERCEDED DATE: 04/21/2003
Name: ASHEPOO-COOSAW CUTOFF, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11513 Latitude: 32° 31.5' N
USGS Quad: BENNETTS POINT Longitude: 80° 27.1' W
To reach the tidal bench marks from U.S. Highway 17 in Jacksonboro, proceed
south on 17 for 8.0 miles (12.9 km), left on State Road 5-15-26 for 15.6 miles
(25.1 km) to end of pavement, right on dirt road for 0.2 mile (0.3 km) to Boat
Landing on left, continue by boat down Mosquito Creek to junction of Ashepoo
river at Bennetts Point, down the Ashepoo River, 2.0 miles (3.2 km) to the
Intracoastal Waterway, then south on waterway for 0.5 mile (0.8 km) to day
marker #169. The gage and staff were located on a platform constructed on a
piling of the day marker.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 7482 A 1981
MONUMENTATION: Survey Disk VM#: 6772
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is located ENE of daymarker #169, 244.0 feet (74.4 m) WNW of
Bench Mark 7482 C 1981, 32.7 feet (10.0 m) SSE of Marsh Edge/Shoreline, 32.0
feet (9.8 m) SSE of bank of Ashepoo Coosaw cutoff and 3.2 feet (1.0 m) SW of
witness post with sign. The bench mark is 0.2 foot (0.06 m) above ground level,
crimped to a stainless steel rod driven 45 feet (14 m) and encased in a 5 inch
PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 7482 C 1981
MONUMENTATION: Survey Disk VM#: 6773
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is located on western tip of northernmost Hammock, 184.6 feet
(56.3 m) NE of Bench Mark 7482 F 1981, 17.9 feet (5.5 m) NW of 0.7 foot (0.2 m)
diameter cedar tree, 8.0 feet (2.4 m) NE of 1.5 feet (0.5 m) diameter palmetto
tree, and 4.0 feet (1.2 m) west of witness post with sign. The bench mark is
0.2 foot (0.1 m) above ground level, crimped to a stainless steel rod driven 45
feet (14 m) to refusal and encased in a 5 inch PVC pipe and concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 11/18/1983
Station ID: 8667482 SUPERCEDED DATE: 04/21/2003
Name: ASHEPOO-COOSAW CUTOFF, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11513 Latitude: 32° 31.5' N
USGS Quad: BENNETTS POINT Longitude: 80° 27.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7482 F 1981
MONUMENTATION: Survey Disk VM#: 6774
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is 20.4 feet (6.2 m) NE of NE face of 1.2 feet (0.4 m) diameter
cedar tree, 12.0 Feet (3.7 m) south of north face of 1.2 feet (0.4 m) diameter
cedar tree, and 4.5 feet (1.4 m) SE of witness post with sign. The bench mark
is 0.3 foot (0.1 m) above ground level, set flush in a concrete monument.
BENCH MARK STAMPING: 7482 G 1981
MONUMENTATION: Survey Disk VM#: 6775
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is 211.9 feet (64.6 m) SW of Bench Mark 7482 H 1981, 13.0 feet
(4.0 m) west of 0.5 foot (0.2 m) diameter cedar tree, 11.9 feet (3.6 m) WNW of
0.7 foot (0.2m) diameter cedar tree, 11.8 feet (3.6 m)SW of witness post with
sign, and 5.5 feet (1.7 m) ESE of center of two 1.6 feet (0.5 m) diameter
palmetto trees. The bench mark is 0.2 foot (0.1 m) above the ground, set flush
in a concrete monument.
BENCH MARK STAMPING: 7482 H 1981
MONUMENTATION: Survey Disk VM#: 6776
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is 14.4 feet (4.4 m) SW of 1.2 feet (0.4 m) diameter cedar tree,
12.4 feet (3.8 m) NW of witness post wigh sign, 10.7 feet (3.3 m) north of 0.5
foot (0.2 m) diameter cedar tree, and 5.8 feet (1.8 m) ESE of center of two 1.5
feet (0.5m) diameter palmetto trees. The bench mark is 0.3 foot (0.1 m) above
ground level, set flush in a concrete monument.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 11/18/1983
Station ID: 8667482 SUPERCEDED DATE: 04/21/2003
Name: ASHEPOO-COOSAW CUTOFF, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11513 Latitude: 32° 31.5' N
USGS Quad: BENNETTS POINT Longitude: 80° 27.1' W
T I D A L D A T U M S
Tidal datums at ASHEPOO-COOSAW CUTOFF, INTRACOASTAL WATERWAY based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: JUNE-DECEMBER 1981
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 (12/13/1981) = 8.94
MEAN HIGHER HIGH WATER MHHW = 6.72
MEAN HIGH WATER MHW = 6.40
MEAN TIDE LEVEL MTL = 3.30
MEAN LOW WATER MLW = 0.20
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/09/1981) = -1.18
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
7482 A 1981 7.50 1.10
7482 C 1981 8.63 2.23
7482 F 1981 8.54 2.14
7482 G 1981 8.60 2.20
7482 H 1981 8.75 2.35
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 11/18/1983
Station ID: 8667482 SUPERCEDED DATE: 04/21/2003
Name: ASHEPOO-COOSAW CUTOFF, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11513 Latitude: 32° 31.5' N
USGS Quad: BENNETTS POINT Longitude: 80° 27.1' 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.