U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


To reach the tidal bench marks from the west end of the Hathaway Bridge of St.
Andrews Bay, go west on U.S. Highway 98 for 1.3 km (0.8 mi) to Thomas Drive,
turn left and go south on Thomas Drive for 1.6 km (1.0 mi) to a paved road on
the left which is the west gate entrance to the Naval Coastal System Center
(Crag Road), turn left and go east (passing through the gate for 0.08 km (0.05
mi) to a security station (building No 329), then proceed north 0.08 km (0.05
mi) to a U-turn, turn right and go south for 0.6 km (0.4 mi) on Crag Road to a
T-junction, turn left and go east for 0.3 km (0.2 mi) to the Coast Guard Station
Boat Slip.  The bench marks are located along the pier.  The tide gage and staff
were on the north edge of the pier, just west of where the Coast Guard docks
their smaller boats and east of their boat launching ramp.


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


                 PRIMARY BENCH MARK STAMPING:  9152 B 1991
                         DESIGNATION:          872 9152 B TIDAL

MONUMENTATION:           Flange-encased Rod                    VM#:        12497
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AI3223
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   30° 10.2' N (  30.17000)          LONGITUDE:  85° 45.4' W ( -85.75670)


The primary bench mark is a flange encased rod set 0.2 km (0.1 mile) south of
the T-junction on Crag Road, 14.39 m (47.2 ft) north of the centerline of Crag
Road, 11.13 m (36.5 ft) south of the concrete brick Coast Guard Station, 9.14 m
(30.0 ft) NE of a  power pole, and 0.24 m (0.8 ft) south of a Carsonite witness
post.  The bench mark is the top of a stainless steel rod driven to a depth of
24.4 m (80 ft), and encased in a 5-inch PVC pipe with logo cap and concrete
kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


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


                         BENCH MARK STAMPING:  9152 A 1991
                         DESIGNATION:          872 9152 A TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:        12499
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AI3221
SETTING CLASSIFICATION:  Concrete pier                         OPUS PID:        
LATITUDE:   30° 10.2' N (  30.17000)          LONGITUDE:  85° 45.3' W ( -85.75500)


The bench mark is a disk set flush in the top of a concrete pier, at the SW
corner of the westernmost covered boat slip, 75.44 m (247.5 ft) north of the
centerline of Crag Road, 54.44 m (178.6 ft) NW of the NW corner of a brick
building (U.S. Coast Guard Old Building), 2.41 m (7.9 ft) east of the west edge
of a 15 m (50 ft) long concrete pier at a boat slip, and 2.41 m (7.9 ft) east of
the east edge of the easternmost boat launching ramp.



                         BENCH MARK STAMPING:  9152 C 1991
                         DESIGNATION:          872 9152 C TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:        12500
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AI3224
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID#: AI3224
LATITUDE:   30° 10.2' N (  30.17000)          LONGITUDE:  85° 45.5' W ( -85.75830)


The bench mark is a disk set flush in the top of a concrete monument about 0.5
km (0.3 mile) south on Thomas Drive from the entrance to the Naval Coastal
System Center, 15 m (50 ft) east of the centerline of Thomas Drive, 3 m (10 ft)
NE of power pole #60240-42753, 0.61 m (2.0 ft) SW of a 2 m (6 ft) chain link
fence, and 0.46 m (1.5 ft) SW of a Carsonite witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


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


                         BENCH MARK STAMPING:  9152 D 1991
                         DESIGNATION:          872 9152 D TIDAL

MONUMENTATION:           Flange-encased Rod                    VM#:        12501
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AI3225
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   30° 10.0' N (  30.16670)          LONGITUDE:  85° 45.4' W ( -85.75670)


The bench mark is a flange encased rod set in a grassy area north of the parking
lot of the Jr. Food Store, 2.4 km (1.5 miles) south on Thomas Drive from its
junction with U.S. Highway 98, 22.22 m (72.9 ft) west of the centeline of Thomas
Drive, 11.37 m (37.3 ft) ENE of the NE corner of a brick building (Jr. Food
Store), 0.85 m (2.8 ft) east of a 0.61 m x 0.61 m (2 ft x 2 ft) concrete base
for a light pole, and 0.82 m (2.7 ft) east of a Carsonite witness post.  The
bench mark is the top of a stainless steel rod driven to a depth of 24.4 m (80.0
ft), and encased in a 5-inch PVC pipe with logo cap and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


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


                         BENCH MARK STAMPING:  NCSC NO 3 1989
                         DESIGNATION:          NCSC NO 3

MONUMENTATION:           Survey disk                           VM#:        12502
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:  AI3222
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   30° 10.2' N (  30.17000)          LONGITUDE:  85° 45.4' W ( -85.75670)


The bench mark is a disk set in top of a concrete monument NW of the NW corner
of the U.S. Coast Guard main building, near the edge of Alligator Bayou, 62.18 m
(204.0 ft) north of the centerline of Crag Road, 22.92 m (75.2 ft) NW of a
concrete brick building, 14.94 m (49.0 ft) NW of a 4 m (12 ft) satellite dish,
5.49 m (18.0 ft) south of the approximate shoreline, and 0.76 m (2.5 ft) north
of a carsonite witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


                            T I D A L   D A T U M S 


Tidal datums at ALLIGATOR BAYOU, PANAMA CITY based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           September 1991 - October 1991
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8729108 PANAMA CITY, ST. ANDREW BAY


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.417
     MEAN HIGH WATER                            MHW    =  0.398
     MEAN SEA LEVEL                             MSL    =  0.210
     MEAN TIDE LEVEL                            MTL    =  0.207
     North American Vertical Datum              NAVD88 =  0.159
     MEAN LOW WATER                             MLW    =  0.016
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     9152 B 1991                                 5.340    4.942
     9152 A 1991                                 1.163    0.765
     9152 C 1991                                 3.653    3.255
     9152 D 1991                                 5.013    4.615
     NCSC NO 3 1989                              2.663    2.265


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8729152                         PUBLICATION DATE:  10/30/2003
Name:       ALLIGATOR BAYOU, PANAMA CITY                      
            FL
NOAA Chart: 11391                           Latitude:   30° 10.2' N (  30.17000)
USGS Quad:  PANAMA CITY BEACH               Longitude:  85° 45.3' W ( -85.75500)


                             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.