U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 08/18/1988
Station ID: 8660983 SUPERCEDED DATE: 04/21/2003
Name: SOCASTEE BRIDGE, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11535 Latitude: 33° 41.2' N
USGS Quad: BUCKSVILLE Longitude: 79° 0.3' W
To reach the tidal bench marks from the intersection of State Highways 501 and
707 NW of Myrtle Beach, proceed west on State Highway 707 for 7 miles (11 km) to
State Highway 544 and the swing bridge crossing the Intracoastal Waterway. The
bench marks are north of the bridge along State Highway 544. The tide gage and
staff were on the fender at the north side of the bridge.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0983 A 1976
MONUMENTATION: Survey Disk VM#: 3739
AGENCY: PID#: DD1619
SETTING CLASSIFICATION: Bridge Abutment
The bench mark is set in the NE concrete abutment of the State Highway 544
bridge over the Intracoastal Waterway, 15.0 feet (4.6 m) NE of the centerline of
the highway, 4.0 feet (1.2 m) west of the wooden steps leading beneath the
bridge, 2.0 feet (0.6 m) south of a utility pole, and 1.4 feet (0.4 m) east of
the NE corner of the bridge.
BENCH MARK STAMPING: SOCASTEE 1934
MONUMENTATION: Survey Disk VM#: 3736
AGENCY: PID#: DD1617
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument near the first house north of the
bridge on the east side of the highway, 70.2 (21.4 m) east of a 0.5-foot (0.2 m)
high brick wall, 39.1 feet (11.9 m) NE of a 1.5-foot (0.5 m) diameter magnolia
tree, 37.0 feet (11.3 m) WSW of a large camilla bush, and 0.7 foot (0.2 m) below
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 08/18/1988
Station ID: 8660983 SUPERCEDED DATE: 04/21/2003
Name: SOCASTEE BRIDGE, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11535 Latitude: 33° 41.2' N
USGS Quad: BUCKSVILLE Longitude: 79° 0.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SOCASTEE NO 3 1934
MONUMENTATION: Survey Disk VM#: 3737
AGENCY: PID#: DD1620
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument near the first house north of the
bridge on the west side of the highway, 58.8 feet (17.9 m) ESE of the center of
the bottom step leading to the house, 51.7 feet (15.8 m) WSW of the centerline
of State Highway 544, 37.7 feet (11.5 m) west of utility pole #1G21, 32.2 feet
(9.8 m) NW of a 3-foot (1 m) diameter pine tree, and 14.2 (4.3 m) SSW of the
center of a twin magnolia tree.
BENCH MARK STAMPING: SOCASTEE NO 4 1934
MONUMENTATION: Survey Disk VM#: 3738
AGENCY: PID#: DD1618
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument north of the bridge on the east
side of the highway, 99.0 feet (30.2 m) SSW of the SW corner of the screened
porch of a house, 81.0 feet (24.7 m) east of the centerline of State Highway
544, 49.6 feet (15.1 m) south of Bench Mark SOCASTEE 1934, 33.7 feet (10.3 m) SE
of a 1.5-foot (0.5 m) diameter magnolia tree, 21.0 feet (6.4 m) north of a
cluster of four pine trees, and at ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 08/18/1988
Station ID: 8660983 SUPERCEDED DATE: 04/21/2003
Name: SOCASTEE BRIDGE, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11535 Latitude: 33° 41.2' N
USGS Quad: BUCKSVILLE Longitude: 79° 0.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0983 B 1976
MONUMENTATION: Survey Disk VM#: 3740
AGENCY: PID#: DD1616
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is in a lawn about 900 feet (274 m) north of the bridge on the
east side of the highway, 72.3 feet (22.0 m) north of utility pole #3-64, 70.6
feet (21.5 m) NNW of a free-standing water spigot, 23.7 feet (7.2 m) east of the
centerline of State Highway 544, and 4.4 feet (1.3 m) west of utility pole #6a.
The bench mark is 0.1 foot (0.3 m) below ground level, crimped to a copper-clad
steel rod driven 15 feet (5 m) to refusal, and encased in a 4-inch PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 0983 F 1982
MONUMENTATION: Survey Disk VM#: 3741
AGENCY: PID#: DD1622
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 239.1 feet (72.9 m) west of Bench Mark 0983 B 1976, 49.0 feet
(14.9 m) NW of a secondary state road, 44.3 feet (13.5 m) south of the SW corner
of the front porch of a wooden house, 21.8 feet (6.6 m) west of a 1.5- foot (0.5
m) diameter pecan tree, and 14.3 feet (4.4 m) SSE of a utility pole with light.
The bench mark is at ground level, crimped to a stainless steel rod driven 48
feet (15 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 4 of 5
PUBLICATION DATE: 08/18/1988
Station ID: 8660983 SUPERCEDED DATE: 04/21/2003
Name: SOCASTEE BRIDGE, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11535 Latitude: 33° 41.2' N
USGS Quad: BUCKSVILLE Longitude: 79° 0.3' W
T I D A L D A T U M S
Tidal datums at SOCASTEE BRIDGE, INTRACOASTAL WATERWAY based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: OCTOBER, DECEMBER 1976
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8661139 BUCKSPORT
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (12/28/1976) = 2.75
MEAN HIGHER HIGH WATER MHHW = 2.20
MEAN HIGH WATER MHW = 2.08
MEAN TIDE LEVEL MTL = 1.09
MEAN LOW WATER MLW = 0.11
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (11/11/1976) = -1.76
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
0983 A 1976 15.86 13.78
SOCASTEE 1934 13.04 10.96
SOCASTEE NO 3 1934 13.21 11.13
SOCASTEE NO 4 1934 12.89 10.81
0983 B 1976 15.89 13.81
0983 F 1982 19.04 16.96
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 08/18/1988
Station ID: 8660983 SUPERCEDED DATE: 04/21/2003
Name: SOCASTEE BRIDGE, INTRACOASTAL WATERWAY
SOUTH CAROLINA
NOAA Chart: 11535 Latitude: 33° 41.2' N
USGS Quad: BUCKSVILLE Longitude: 79° 0.3' 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.