U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 09/04/1990
Station ID: 8731952 SUPERCEDED DATE: 04/21/2003
Name: BON SECOUR
ALABAMA
NOAA Chart: 11376 Latitude: 30° 18.2' N
USGS Quad: FOLEY Longitude: 87° 44.1' W
To reach the tidal bench marks from the intersection of U.S. Interstate 10 and
Gulf Shores Parkway east of Mobile Bay, proceed 24 miles (39 km) south on Gulf
Shores Parkway to Baldwin County Road 10, then west on County Road 10 to Bon
Secour Post Office, and continue south on County Road 10 for another 1.2 miles
(1.9 km) to Bon Secour Fisheries. The bench marks are near the Bon Secour
Fisheries facilities. The tide gage and staff were on the west side of the Bon
Secour Fisheries pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1952 A 1980
MONUMENTATION: Survey Disk VM#: 10344
AGENCY: PID:
SETTING CLASSIFICATION: Mat Foundation
The bench mark is set flush in a concrete foundation pad on the north side of
the Bon Secour Fisheries building, 134 feet (41 m) south of a large oak tree, 72
feet (22 m) south of the centerline of the paved road, 16 feet (5 m) SE of the
NW corner of the Bon Secour Fisheries building, 8 feet (2 m) south of the NE
corner of a concrete platform supporting four steps, and 7 feet (2 m) east of
the steps.
BENCH MARK STAMPING: 12 RWH 1976
MONUMENTATION: Survey Disk VM#: 10342
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument 0.2 mile (0.3 km) west of the Bon
Secour Fisheries building, at the end of a paved and dirt road, 107.8 feet (32.9
m) south of the SW corner of a white frame cottage, 79 feet (24 m) NW of the
centerline of an east-west road, 40.4 feet (12.3 m) east of a dirt drive north
along a small canal, 3 feet (1 m) SE of a 0.8-foot (0.2 m) diameter pine tree
with witness sign, and 0.2 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 09/04/1990
Station ID: 8731952 SUPERCEDED DATE: 04/21/2003
Name: BON SECOUR
ALABAMA
NOAA Chart: 11376 Latitude: 30° 18.2' N
USGS Quad: FOLEY Longitude: 87° 44.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 21 JRH 1976
MONUMENTATION: Survey Disk VM#: 10343
AGENCY: PID:
SETTING CLASSIFICATION: Bridge Abutment
The bench mark is set in the wheelguard at the SE corner of a bridge over a
small stream between the Bon Secour church and school, 540 feet (165 m)
northeast of a crossroads.
BENCH MARK STAMPING: 1952 B 1980
MONUMENTATION: Survey Disk VM#: 10345
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is on the north side of the paved road, 382 feet (116 m) west of
Bench Mark 1952 A 1980, 82 feet (25 m) SW of the SW corner of a residence, 30
feet (9 m) north of the centerline of the paved road, and 1.0 foot (0.3 m) north
of utility pole #AWP10R60SP0 with witness sign. The bench mark is 0.3 foot (0.1
m) below ground level, crimped to a stainless steel rod driven 55 feet (16.7 m)
to refusal, and encased in a 4-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: NO 7 1986
MONUMENTATION: Survey Disk VM#: 10346
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Slab
The bench mark is set flush in a 3 x 5-foot (1x2 m) concrete slab in a park area
of Bon Secour Fisheries, 98.5 feet (30.0 m) ESE of the SE cornerof Bon Secour
Fisheries fish house, 73.2 feet (22.3 m) north of a five pile dolphin at the SW
corner of the Bon Secour Fisheries pier, and 68.5 feet (20.9 m) south of a power
pole south of an abandoned building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 09/04/1990
Station ID: 8731952 SUPERCEDED DATE: 04/21/2003
Name: BON SECOUR
ALABAMA
NOAA Chart: 11376 Latitude: 30° 18.2' N
USGS Quad: FOLEY Longitude: 87° 44.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 8 1986
MONUMENTATION: Survey Disk VM#: 10347
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is recessed in an old house foundation on property owned by the
Adams family, across the paved road and just north of Bon Secour Fisheries, 35.1
feet (10.7 m) south of the larger of two oak trees, 32.2 feet (9.8 m) north of a
2.0-foot (0.6 m) diameter tree, 29 feet (9 m) west of power pole #972 on the
west side of County Road 10, and 0.5 foot (0.2 m) below the surface of the
foundation.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 09/04/1990
Station ID: 8731952 SUPERCEDED DATE: 04/21/2003
Name: BON SECOUR
ALABAMA
NOAA Chart: 11376 Latitude: 30° 18.2' N
USGS Quad: FOLEY Longitude: 87° 44.1' W
T I D A L D A T U M S
Tidal datums at BON SECOUR based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: MAY-NOVEMBER 1986
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8729840 PENSACOLA, FL
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (11/26/1980) = 4.00
MEAN HIGHER HIGH WATER (MHHW) = 1.55
MEAN HIGH WATER (MHW) = 1.47
MEAN TIDE LEVEL (MTL) = 0.77
MEAN LOW WATER (MLW) = 0.07
MEAN LOWER LOW WATER (MLLW) = 0.00
LOWEST OBSERVED WATER LEVEL (11/26/1980) = -1.89
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
1952 A 1980 4.32 2.85
12 RWH 1976 4.41 2.94
21 JRH 1976 8.72 7.25
1952 B 1980 2.71 1.24
NO 7 1986 3.96 2.49
NO 8 1986 7.20 5.73
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 09/04/1990
Station ID: 8731952 SUPERCEDED DATE: 04/21/2003
Name: BON SECOUR
ALABAMA
NOAA Chart: 11376 Latitude: 30° 18.2' N
USGS Quad: FOLEY Longitude: 87° 44.1' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.