Superseded Bench Mark Sheet for 8728151, ST. MARKS CITY FL

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  08/05/1985
Station ID: 8728151                                SUPERCEDED DATE:   04/21/2003
Name:       ST. MARKS CITY, ST. MARKS RIVER                   
            FLORIDA
NOAA Chart: 11405                                  Latitude:         30°  9.3' N
USGS Quad:  ST. MARKS                              Longitude:        84° 12.2' W


To reach the tidal bench marks from the intersection of U.S. Highway 98 and
State Highway 363, proceed south on State Highway 363 to the Sam O. Purdom Power
Plant in St. Marks, continue south on State Highway 363 0.65 mile (1.05 km) to
the end of the highway, continue east on Riverside Drive 0.1 mile (0.2 km) to
Shields Marina, on the north side of the St. Marks River.  The tide gage and
staff were on a piling on the south side of the main boat house at the marina.
The bench marks are on the Tenneco Corporation property, along State Highway
363, and along Riverside Drive.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  8151 B 1977

MONUMENTATION:           Survey Disk                               VM#:     8287
AGENCY:                                                            PID#:  BE2427
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is at the junction of State Highway 363 and Riverside Drive, 48.0
feet (14.6 m) WSW of the centerline of State Highway 363, 37.5 feet (11.4 m) NNW
of the centerline of Riverside Drive, 18.6 feet (5.7 m) WSW of an iron grating
over a drainage box, 5.8 feet (1.8 m) WSW of the Port Leon Historical Marker
sign, and 0.2 foot (0.1 m) ESE of a metal witness post.  The bench mark is
crimped to a copper-clad steel rod driven 13 feet (4 m) to refusal, and encased
in a PVC pipe and concrete kickblock, and projecting 0.1 foot (0.03 m) above
ground.



                         BENCH MARK STAMPING:  8151 A 1977

MONUMENTATION:           Survey Disk                               VM#:     8286
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is at the junction of Riverside Drive and Tallahassee Road, 34.9
feet (10.6 m) SW of the SW corner of a white frame house, 31.0 feet (9.4 m) NNW
of the centerline of Riverside Drive, 17.5 feet (5.3 m) ENE of the centerline of
Tallahassee Road, 11.8 feet (3.6 m) NW of a fire hydrant, and 0.35 feet (0.11 m)
WSW of a metal witness post.  The bench mark is crimped to a copper-clad steel
rod driven 12 feet (4 m) to refusal, and encased in a PVC pipe and concrete
kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                   PUBLICATION DATE:  08/05/1985
Station ID: 8728151                                SUPERCEDED DATE:   04/21/2003
Name:       ST. MARKS CITY, ST. MARKS RIVER                   
            FLORIDA
NOAA Chart: 11405                                  Latitude:         30°  9.3' N
USGS Quad:  ST. MARKS                              Longitude:        84° 12.2' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  8151 C 1977

MONUMENTATION:           Survey Disk                               VM#:     8288
AGENCY:                                                            PID#:  BE2426
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is on the east side of State Highway 363, 96.0 feet (29.3 m) NE
of the NE corner of Bo Lynn Grocery and Meat Market, 30.5 feet (9.3 m) ENE of
the centerline of State Highway 363, 10.0 feet (3.0 m) SE of the north end of a
concrete pipe in the drainage ditch, and 0.2 foot (0.1 m) WSW of a metal witness
post.  The bench mark is crimped to a copper-clad steel rod driven 14 feet (4 m)
to refusal, and encased in a PVC pipe and concrete kickblock, and projecting 0.2
foot (0.1 m) above ground.



                         BENCH MARK STAMPING:  NO 6 1958

MONUMENTATION:           Survey Disk                               VM#:     8289
AGENCY:                                                            PID#:  BE1143
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is in the foundation of the Tenneco Petroleum Corporation Office
on the east side of State Highway 363, 5.0 feet (1.5 m) SE of the SE corner of
the building, 0.5 foot (0.2 m) north of the south face, 0.5 foot (0.2 m) west of
the east face, and 2 feet (0.6 m) above ground level.  The bench mark is set
flush in the SE corner of the building.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                   PUBLICATION DATE:  08/05/1985
Station ID: 8728151                                SUPERCEDED DATE:   04/21/2003
Name:       ST. MARKS CITY, ST. MARKS RIVER                   
            FLORIDA
NOAA Chart: 11405                                  Latitude:         30°  9.3' N
USGS Quad:  ST. MARKS                              Longitude:        84° 12.2' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  NO 7 1958

MONUMENTATION:           Survey Disk                               VM#:     8290
AGENCY:                                                            PID#:  BE1144
SETTING CLASSIFICATION:  Concrete Loading Platform


The bench mark is set in a loading platform of the Tenneco Petroleum Corporation
Warehouse and Canning Plant on the west side of State Highway 363, 1 foot (0.3
m) north of the south face of the foundation, 0.5 foot (0.2 m) west of the east
face, and 2.5 feet (0.8 m) above ground.  The bench mark is set flush in the top
of the loading platform.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                   PUBLICATION DATE:  08/05/1985
Station ID: 8728151                                SUPERCEDED DATE:   04/21/2003
Name:       ST. MARKS CITY, ST. MARKS RIVER                   
            FLORIDA
NOAA Chart: 11405                                  Latitude:         30°  9.3' N
USGS Quad:  ST. MARKS                              Longitude:        84° 12.2' W


                            T I D A L   D A T U M S 


Tidal datums at ST. MARKS CITY, ST. MARKS RIVER based on:

     LENGTH OF SERIES:      5 MONTHS
     TIME PERIOD:           MARCH-JULY 1977
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8728229 SHELL POINT


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:

     HIGHEST OBSERVED WATER LEVEL (04/05/1977)         =   5.41
     MEAN HIGHER HIGH WATER                     MHHW   =   3.73
     MEAN HIGH WATER                            MHW    =   3.34
     MEAN TIDE LEVEL                            MTL    =   1.94
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   1.26
     MEAN LOW WATER                             MLW    =   0.54
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (04/07/1977)         =  -1.84

   * NGVD reference based on adjustment of 1967 and NOS levels of 1977. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     8151 B 1977                                 5.54      2.20
     8151 A 1977                                 5.90      2.56
     8151 C 1977                                 5.51      2.17
     NO 6 1958                                   7.87      4.53
     NO 7 1958                                   8.76      5.42


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                   PUBLICATION DATE:  08/05/1985
Station ID: 8728151                                SUPERCEDED DATE:   04/21/2003
Name:       ST. MARKS CITY, ST. MARKS RIVER                   
            FLORIDA
NOAA Chart: 11405                                  Latitude:         30°  9.3' N
USGS Quad:  ST. MARKS                              Longitude:        84° 12.2' 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.

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