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

                                                                                
Station ID: 8725271                                PUBLICATION DATE:  02/05/2004
Name:       IMPERIAL RIVER, HEADWATERS                        
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 20.6' N
USGS Quad:  BONITA SPRINGS                         Longitude:        81° 46.8' W


To reach the tidal bench marks from the Post Office in Bonita Springs, proceed
north on Old US Highway 41 Road for 0.24 km (0.15 mi) to the north side of the
bridge over the Imperial River.  The bench marks are along Old US Highway 41
Road, north of the bridge.  The tide station was 12.19 m (40.0 ft) NE of the NE
corner of the bridge.


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


                 PRIMARY BENCH MARK STAMPING:  5271 A 1978
                         DESIGNATION:          872 5271 A TIDAL

MONUMENTATION:           Tidal Station disk                        VM#:     7865
AGENCY:                  National Ocean Survey (NOS)               PID#:  AD6335
SETTING CLASSIFICATION:  Concrete sea wall


The primay bench mark is a disk set flush into the concrete sea wall near the SW
corner of the Bamboo Mobile Home Village, 9 m (30 ft) NE of the NE corner of the
bridge.



                         BENCH MARK STAMPING:  5271 B 1978
                         DESIGNATION:          872 5271 B TIDAL

MONUMENTATION:           Tidal Station disk                        VM#:     7866
AGENCY:                  National Ocean Survey (NOS)               PID#:  AD6334
SETTING CLASSIFICATION:  Concrete step


The bench mark is a disk set flush into the first concrete step at the entrance
to the Everglades Wonder Gardens, 83.82 m (275.0 ft) SW of bench mark 5271 C
1978, 64 m (210 ft) north of the north end of the bridge over the Imperial
River, 20.42 m (67.0 ft) west of the centerline of Old U.S. Highway 41 Road, 12
m (41 ft)  and 4 m (13 ft) SE of the entrance door of Everglades Wonder Gardens.

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

                                                                                
Station ID: 8725271                                PUBLICATION DATE:  02/05/2004
Name:       IMPERIAL RIVER, HEADWATERS                        
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 20.6' N
USGS Quad:  BONITA SPRINGS                         Longitude:        81° 46.8' W


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


                         BENCH MARK STAMPING:  5271 C 1978
                         DESIGNATION:          872 5271 C TIDAL

MONUMENTATION:           Tidal Station disk                        VM#:     7867
AGENCY:                  National Ocean Survey (NOS)               PID#:  AD6332
SETTING CLASSIFICATION:  Concrete post


The bench mark is a disk set into the top of a concrete post on the property of
the Pittman Funeral Home located north of the bridge over the Imperial River,
140 m (460 ft) north of the north end of the old US Highway 41, 10.67 m (35.0
ft) east of the centerline of Old U.S. Highway 41 Road, 9.45 m (31.0 ft) WNW of
the NW corner of the Pittman Funeral Home building, and 1.07 m (3.5 ft) NE of a
utility pole.  



                         BENCH MARK STAMPING:  5271 D 1978
                         DESIGNATION:          872 5271 D TIDAL

MONUMENTATION:           Tidal Station disk                        VM#:     7868
AGENCY:                  National Ocean Survey (NOS)               PID#:  AD6333
SETTING CLASSIFICATION:  Concrete step


The bench mark is a disk set flush into the first concrete step of the Bonita
Springs Shoe Store located north of the bridge over the Imperial River, 232 m
(760 m ) north of the north end of the old US Highway 41 bridge over the river,
96 m (315 ft) NW of bench mark 5271 C 1978 and 18.29 m (60.0 ft) west of the
centerline of Old U.S. Highway 41 Road.

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

                                                                                
Station ID: 8725271                                PUBLICATION DATE:  02/05/2004
Name:       IMPERIAL RIVER, HEADWATERS                        
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 20.6' N
USGS Quad:  BONITA SPRINGS                         Longitude:        81° 46.8' W


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


                         BENCH MARK STAMPING:  M 244 1965
                         DESIGNATION:          M 244

MONUMENTATION:           Bench Mark disk                           VM#:     7869
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  AD1314
SETTING CLASSIFICATION:  Concrete bridge abutment


The bench mark is a disk set in the west end of the south abutment of the
Atlantic Coastline Railroad bridge over the Imperial River, 114.30 m (375.0 ft)
west of the centerline of Old U.S. Highway 41 Road, 3.20 m (10.5 ft) west of the
rail, 0.09 m (0.3 ft) east of the west face of the abutment, and 1.22 m (4.0 ft)
below the track surface.

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

                                                                                
Station ID: 8725271                                PUBLICATION DATE:  02/05/2004
Name:       IMPERIAL RIVER, HEADWATERS                        
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 20.6' N
USGS Quad:  BONITA SPRINGS                         Longitude:        81° 46.8' W


                            T I D A L   D A T U M S 


Tidal datums at IMPERIAL RIVER, HEADWATERS based on:

     LENGTH OF SERIES:      5 MONTHS
     TIME PERIOD:           March 1978 - July 1978
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8725110 NAPLES, GULF OF MEXICO


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.289
     MEAN HIGH WATER                            MHW    =  0.232
     North American Vertical Datum              NAVD88 =  0.210
     MEAN TIDE LEVEL                            MTL    =  0.132
     MEAN SEA LEVEL                             MSL    =  0.128
     MEAN LOW WATER                             MLW    =  0.033
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     5271 A 1978                                 1.164    0.932
     5271 B 1978                                 2.362    2.130
     5271 C 1978                                 2.265    2.033
     5271 D 1978                                 2.585    2.353
     M 244 1965                                  2.500    2.268


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

                                                                                
Station ID: 8725271                                PUBLICATION DATE:  02/05/2004
Name:       IMPERIAL RIVER, HEADWATERS                        
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 20.6' N
USGS Quad:  BONITA SPRINGS                         Longitude:        81° 46.8' 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.