U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 10/07/1987
Station ID: 8665641 SUPERCEDED DATE: 04/21/2003
Name: WELCHS WHARF, STONO RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 45.8' N
USGS Quad: JOHNS ISLAND Longitude: 80° 0.1' W
To reach the tidal bench marks from the intersection of State Highways 700 and
171 on James Island, proceed west on State Highway 700 for 1.5 miles (0.2 km) to
Riverland Drive, proceed north on Riverland Drive for 0.5 mile (0.8 km) to Stono
Drive, then west on Stono Drive for 0.1 mile (0.2 km) to Welchs property at 151
Stono Drive. The bench marks are near the riverbank behind two homes along
Stono Drive. The tide gage and staff were located behind Welchs residence on
the dock.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 2 1933
MONUMENTATION: Survey Disk VM#: 4215
AGENCY: PID#: CK2273
SETTING CLASSIFICATION: Concrete-filled Tile Pipe
The bench mark is set flush in a concrete-filled tile pipe behind the residence
at 151 Stono Drive, below a sloping embankment near a brick seawall, 24.7 feet
(7.5 m) SSW of a stone fence property line, 10.5 feet (3.2 m) ESE of the
seawall, 10.4 feet (3.2 m) ENE of a wooden walkway to the dock, 9.1 feet (2.8 m)
NNE of steps leading down the embankment, and at ground level.
BENCH MARK STAMPING: NO 3 1933
MONUMENTATION: Survey Disk VM#: 4216
AGENCY: PID#: CK2272
SETTING CLASSIFICATION: Concrete-filled Tile Pipe
The bench mark is set flush in a concrete-filled tile pipe behind the residence
at 151 Stono Drive, 41.9 feet (12.8 m) ESE of the brick seawall, 40.1 feet (12.2
m) NW of a large oak tree, 39.5 feet (12.0 m) NE of Bench Mark NO 2 1933, 2.3
feet (0.7 m) SSW of a woven wire fence line, and 0.5 foot (0.2 m) above
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 10/07/1987
Station ID: 8665641 SUPERCEDED DATE: 04/21/2003
Name: WELCHS WHARF, STONO RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 45.8' N
USGS Quad: JOHNS ISLAND Longitude: 80° 0.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1974
MONUMENTATION: Survey Disk VM#: 4217
AGENCY: PID#: CK2270
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument in the NW corner of the
property at 309 Stono Drive (Gibbs residence), 55.7 feet (17.0 m) NNW of the NW
corner of the residence, 30.3 feet (9.2 m) NNE of a nautical lamp post at the
top of steps leading to the dock, 18.8 feet (5.7 m) ESE of a large twin-trunk
oak tree, and at ground level.
BENCH MARK STAMPING: NO 6 1974
MONUMENTATION: Survey Disk VM#: 4218
AGENCY: PID#: CK2269
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument in the SW corner of the
property at 309 Stono Drive (Gibbs residence), 26.3 feet (8.0 m) WSW of the SW
corner of a glass-enclosed porch, 25.4 feet (7.7 m) south of the middle of three
oak trees near the end of the embankment, 7.8 feet (2.4 m) east of a lone oak
tree at the end of the embankment, and at ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 10/07/1987
Station ID: 8665641 SUPERCEDED DATE: 04/21/2003
Name: WELCHS WHARF, STONO RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 45.8' N
USGS Quad: JOHNS ISLAND Longitude: 80° 0.1' W
T I D A L D A T U M S
Tidal datums at WELCHS WHARF, STONO RIVER based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: OCTOBER 1974-SEPTEMBER 1975
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 (07/21/1974) = 7.50
MEAN HIGHER HIGH WATER MHHW = 5.72
MEAN HIGH WATER MHW = 5.42
MEAN TIDE LEVEL MTL = 2.83
MEAN LOW WATER MLW = 0.23
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (02/26/1975) = -1.74
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 2 1933 9.30 3.88
NO 3 1933 16.48 11.06
NO 5 1974 21.53 16.11
NO 6 1974 21.27 15.85
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 10/07/1987
Station ID: 8665641 SUPERCEDED DATE: 04/21/2003
Name: WELCHS WHARF, STONO RIVER
SOUTH CAROLINA
NOAA Chart: 11524 Latitude: 32° 45.8' N
USGS Quad: JOHNS ISLAND Longitude: 80° 0.1' 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.