U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 04/03/1987
Station ID: 8665101 SUPERCEDED DATE: 04/21/2003
Name: COSGROVE BRIDGE, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 50.1' N
USGS Quad: CHARLESTON Longitude: 79° 59.2' W
To reach the tidal bench marks from the intersection of U.S. Highway 26 and
State Highway 7, proceed SW on State Highway 7 (Sam Rittenberg Boulevard) for
0.8 mile (1.3 km) to the SW end of Cosgrove Bridge, just over the Ashley River.
The bench marks are located near the bridge. The tide gage and staff were
located at the end of the dock extending beneath the southern portion of the
bridge.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5101 E 1976
MONUMENTATION: Survey Disk VM#: 4137
AGENCY: PID#: CJ0481
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is located on the west shoulder of State Highway 7 just past the
SW end of the bridge, 333 feet (101 m) SSW of Bench Mark 5101 D 1976, 309.7 feet
(94.4 m) south of the SW corner of the bridge, 23.6 feet (7.2 m) west of the
west edge of the highway pavement, and 5.4 feet (1.6 m) north of SCE&G utility
pole #160729. The bench mark is 0.2 foot (0.1 m) below ground level, crimped to
a copper-clad steel rod driven to refusal, and encased in a PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 5101 B 1976
MONUMENTATION: Survey Disk VM#: 4134
AGENCY: PID#: CJ0478
SETTING CLASSIFICATION: Concrete Abutment
The bench mark is set flush in the SE bridge abutment, 8.6 feet (2.6 m) north of
the north side of the Memorial Bridge monument, and 3.7 feet (1.1 m) SE of the
east edge of State Highway 7 pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 04/03/1987
Station ID: 8665101 SUPERCEDED DATE: 04/21/2003
Name: COSGROVE BRIDGE, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 50.1' N
USGS Quad: CHARLESTON Longitude: 79° 59.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5101 C 1976
MONUMENTATION: Survey Disk VM#: 4135
AGENCY: PID#: CJ0479
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 174 feet (53 m) south of the SE bridge abutment, 25.6 feet
(7.8 m) SE of the east edge of the highway pavement, 7.8 feet (2.4 m) north of
utility pole #160727, and 7.0 feet (2.1 m) north of a witness post. The bench
mark is 0.2 foot (0.1 m) below ground level, crimped to a copper-clad steel rod
driven to refusal, and encased in a 4-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 5101 D 1976
MONUMENTATION: Survey Disk VM#: 4136
AGENCY: PID#: CJ0480
SETTING CLASSIFICATION: Concrete Support
The bench mark is set flush in the NW corner of the southernmost bridge support,
3.2 feet (1.0 m) north of the north side of the south bridge abutment wall, 0.6
foot (0.2 m) south of the north side of the base support, and 0.6 foot (0.2 m)
east of the west side of the base support.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 04/03/1987
Station ID: 8665101 SUPERCEDED DATE: 04/21/2003
Name: COSGROVE BRIDGE, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 50.1' N
USGS Quad: CHARLESTON Longitude: 79° 59.2' W
T I D A L D A T U M S
Tidal datums at COSGROVE BRIDGE, ASHLEY RIVER based on:
LENGTH OF SERIES: 7 MONTHS
TIME PERIOD: APRIL - OCTOBER 1976
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 (05/13/1976) = 7.55
MEAN HIGHER HIGH WATER MHHW = 6.19
MEAN HIGH WATER MHW = 5.85
MEAN TIDE LEVEL MTL = 3.04
MEAN LOW WATER MLW = 0.23
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/15/1976) = -1.61
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
5101 E 1976 15.21 9.36
5101 B 1976 25.60 19.75
5101 C 1976 16.74 10.89
5101 D 1976 16.95 11.10
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 04/03/1987
Station ID: 8665101 SUPERCEDED DATE: 04/21/2003
Name: COSGROVE BRIDGE, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 50.1' N
USGS Quad: CHARLESTON Longitude: 79° 59.2' 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.