U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8676808 PUBLICATION DATE: 11/14/2018
Name: CRISPEN ISLAND,TURTLE RIVER
GA
NOAA Chart: US5GA13M Latitude: 31° 12.8' N ( 31.21330)
USGS Quad: BURNSWICK WEST Longitude: 81° 33.0' W ( -81.55000)
To reach the tidal bench marks from Brunswick, Georgia, proceed north on State
Route 341 to its intersection with U.S. Interstate 95, then left onto Crispen
Island Boulevard and proceed to the McManus Power Plant Georgia Power Company.
The bench marks are parallel to the pipeline between the marshy area and the
service road at the power plant. The tide gage and staff were located on the
power plant pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6808 A 1980
DESIGNATION: 867 6808 A 1980
MONUMENTATION: Survey disk VM#: 4914
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete pier OPUS PID:
LATITUDE: 31° 12.8' N ( 31.21330) LONGITUDE: 81° 33.1' W ( -81.55170)
The primary bench mark is a disk located at the McManus Power Plant set flush in
the NW corner of the concrete pier, 0.82 m (2.7 ft) north of the western edge of
the pier, 0.43 m (1.4 ft) south of the north end, bearing west at the opposite
end of the pier of Bench Mark 6808 B 1980, west of the water tank and WNW of the
stack of the power company.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8676808 PUBLICATION DATE: 11/14/2018
Name: CRISPEN ISLAND,TURTLE RIVER
GA
NOAA Chart: US5GA13M Latitude: 31° 12.8' N ( 31.21330)
USGS Quad: BURNSWICK WEST Longitude: 81° 33.0' W ( -81.55000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6808 B 1980
DESIGNATION: 867 6808 B 1980
MONUMENTATION: Survey disk VM#: 4915
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete pier OPUS PID:
LATITUDE: 31° 12.8' N ( 31.21330) LONGITUDE: 81° 33.1' W ( -81.55170)
The bench mark is a disk located at the McManus Power Plant set flush in east
end of the concrete pier, 2.26 m (7.4 ft) from the eastern edge of the pier,
0.52 m (1.7 ft) from the southern end of the concrete, bearing west of the water
tank, WNW of the power plant stack and east at the opposite end of the pier from
Bench Mark 6808 B 1980.
BENCH MARK STAMPING: 6808 C 1980
DESIGNATION: 867 6808 C 1980
MONUMENTATION: Survey disk VM#: 4916
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 12.8' N ( 31.21330) LONGITUDE: 81° 33.1' W ( -81.55170)
The bench mark is a disk located at the McManus Power Plant, south of the pipe
line leading to the pier, 56.69 m (186.0 ft) NE of Bench Mark 6808 B 1980, 0.91
m (3.0 ft) south of the pipeline, bearing west of the water tower and WNW of the
power plant stack. The bench mark is set atop an unspecified deep driven rod
protected by a 4-inch diameter PVC pipe and surrounded by a 0.46 m (1.5 ft) in
diameter concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8676808 PUBLICATION DATE: 11/14/2018
Name: CRISPEN ISLAND,TURTLE RIVER
GA
NOAA Chart: US5GA13M Latitude: 31° 12.8' N ( 31.21330)
USGS Quad: BURNSWICK WEST Longitude: 81° 33.0' W ( -81.55000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6808 D 1980
DESIGNATION: 867 6808 D 1980
MONUMENTATION: Survey disk VM#: 4917
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete block OPUS PID:
LATITUDE: 31° 12.8' N ( 31.21330) LONGITUDE: 81° 33.1' W ( -81.55170)
The bench mark is a disk located at the McManus Power Plant set flush in a 0.43
m (4.5 ft) high concrete block used to hold transformers, 40.23 m (132.0 ft) NE
of Bench Mark 6808 C 1980, 1.22 m (4.0 ft) south of the pipeline, bearing west
of the water tank and WNW of the power plant stock.
BENCH MARK STAMPING: 6808 E 1980
DESIGNATION: 867 6808 E 1980
MONUMENTATION: Survey disk VM#: 4918
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 12.8' N ( 31.21330) LONGITUDE: 81° 33.1' W ( -81.55170)
The bench mark is a disk located at the McManus Power Plant south of the
pipeline 29.57 m (97.0 ft) east of Bench Mark 6808 C 1980, 28.35 m (93.0 ft)
north of Bench Mark 6808 D 1980, west of the water tank and WNW of the power
plant stacks. The bench mark is set atop an unspecified deep driven rod
protected by a 4-inch PVC pipe and surrounded by a 0.46 m (1.5 ft) concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8676808 PUBLICATION DATE: 11/14/2018
Name: CRISPEN ISLAND,TURTLE RIVER
GA
NOAA Chart: US5GA13M Latitude: 31° 12.8' N ( 31.21330)
USGS Quad: BURNSWICK WEST Longitude: 81° 33.0' W ( -81.55000)
T I D A L D A T U M S
Tidal datums at CRISPEN ISLAND,TURTLE RIVER based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: May 25 - June 24, 1980
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8670870 FORT PULASKI, SAVANNAH RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.586
MEAN HIGH WATER MHW = 2.481
MEAN SEA LEVEL MSL = 1.391
MEAN TIDE LEVEL MTL = 1.270
MEAN LOW WATER MLW = 0.059
MEAN LOWER LOW WATER MLLW = 0.000
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6808 A 1980 4.076 1.595
6808 B 1980 4.073 1.592
6808 C 1980 3.525 1.044
6808 D 1980 4.668 2.187
6808 E 1980 3.097 0.616
Foot Notes:
Bench mark 6808 B 1980 is based on one differential leveling connection and do
not meet the quality control standards of the NOS. Therefore, caution should be
used when deriving elevations for these marks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8676808 PUBLICATION DATE: 11/14/2018
Name: CRISPEN ISLAND,TURTLE RIVER
GA
NOAA Chart: US5GA13M Latitude: 31° 12.8' N ( 31.21330)
USGS Quad: BURNSWICK WEST Longitude: 81° 33.0' W ( -81.55000)
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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.
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.