U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 04/16/1984
Station ID: 8729753 SUPERCEDED DATE: 04/21/2003
Name: BLACKWATER RIVER
FLORIDA
NOAA Chart: 11382 Latitude: 30° 38.2' N
USGS Quad: MILTON NORTH Longitude: 87° 1.7' W
To reach the tidal bench marks from the Milton City Hall, proceed NW on Highway
87A for 0.1 mile (0.2 km), NE on Highway 191 for 1.0 mile (1.6 km) to a private
dirt driveway on the SE side of the highway, right into the driveway and to the
parking area next to the Blackwater River. The bench marks are located in the
vicinity of the parking area and along Highway 191. The tide gage and staff
were located on a small dock near a picnic shelter.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9753 A 1976
MONUMENTATION: Survey Disk VM#: 10225
AGENCY: PID#: BG4552
SETTING CLASSIFICATION: Concrete Pad
The bench mark is set flush in the SW corner of the concrete porch on the SW
side of a private residence near the small dock 244 feet (74 m) east of Bench
Mark 9753 C 1976, 22.8 feet (6.9 m) west of the SW corner of the house, and 7.5
feet (2.3 m) SW of house.
BENCH MARK STAMPING: 9753 C 1976
MONUMENTATION: Survey Disk VM#: 10226
AGENCY: PID#: BG4551
SETTING CLASSIFICATION: Copper-Clad Steel Rod
The bench mark is 244 feet (74 m) west of Bench Mark 9753 A 1976, 230 feet (70
m) SE of Bench Mark 9753 D 1976, 180 feet (55 m) SE of the centerline of Highway
191, and 2.5 feet (0.8 m) east of a power pole with witness sign. The bench
mark is 0.5 foot (0.2 m) below ground level, crimped to a copper-clad steel rod
driven 25 feet (8 m) to refusal, and encased in a 4-inch PVC pipe and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 04/16/1984
Station ID: 8729753 SUPERCEDED DATE: 04/21/2003
Name: BLACKWATER RIVER
FLORIDA
NOAA Chart: 11382 Latitude: 30° 38.2' N
USGS Quad: MILTON NORTH Longitude: 87° 1.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9753 D 1976
MONUMENTATION: Survey Disk VM#: 10227
AGENCY: PID#: BG4550
SETTING CLASSIFICATION: Copper-Clad Steel Rod
The bench mark is near the intersection of Highway 191 and the driveway leading
to the small dock, 230 feet (70 m) NW of Bench Mark 9753 C 1976, 204 feet (62 m)
NE of the centerline of a dirt driveway on the NW side of Highway 191, 43.3 feet
(13.2 m) NW of the centerline of the highway, 3.2 feet (1.0 m) SE of a steel
mesh fence, and 1.2 feet (0.4 m) SE of a power pole with witness sign. The
bench mark is 0.4 foot (0.1 m) below ground level, crimped to a copper-clad
steel rod driven 23 feet (7 m) to refusal, and encased in a 4-inch PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 9753 G 1976
MONUMENTATION: Survey Disk VM#: 10228
AGENCY: PID#: BG4553
SETTING CLASSIFICATION: Concrete Pad
The bench mark is set flush in the SW corner of a 24 x 19 foot (7 x 6 m)
concrete pad of a picnic shelter, 300 feet (91 m) SE of a private residence,
23.8 feet (7.3 m) SW of the SE corner of the shelter, 18.3 feet (5.6 m) SE of
the NW corner of the shelter, and 12 feet (4 m) NW of the shoreline of
Blackwater River.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 04/16/1984
Station ID: 8729753 SUPERCEDED DATE: 04/21/2003
Name: BLACKWATER RIVER
FLORIDA
NOAA Chart: 11382 Latitude: 30° 38.2' N
USGS Quad: MILTON NORTH Longitude: 87° 1.7' W
T I D A L D A T U M S
Tidal datums at BLACKWATER RIVER based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: APRIL & JUNE 1976
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8729747 SHIELD POINT
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (05/14/1976) = 3.49
MEAN HIGHER HIGH WATER MHHW = 1.62
MEAN HIGH WATER MHW = 1.51
MEAN TIDE LEVEL MTL = 0.82
MEAN LOW WATER MLW = 0.14
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (03/22/1976) = -0.87
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
9753 A 1976 8.95 7.44
9753 C 1976 5.11 3.60
9753 D 1976 4.61 3.10
9753 G 1976 4.43 2.92
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 04/16/1984
Station ID: 8729753 SUPERCEDED DATE: 04/21/2003
Name: BLACKWATER RIVER
FLORIDA
NOAA Chart: 11382 Latitude: 30° 38.2' N
USGS Quad: MILTON NORTH Longitude: 87° 1.7' 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.