U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


To reach the tidal bench marks from the intersection of Laurel Street and U.S.
Highway 41 in Laurel, proceed north on U.S.  Highway 41 for 5.3 km (3.3 miles)
to the intersection of State Road 789, then 1.1 km (0.7 mi) west on State Road
789 to Blackburn Point bridge over the Intracoastal Waterway.  The bench marks
are along State Road 7689 and the vicinity of the bridge.  The tide gage and
staff were located at the bridge.


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


                 PRIMARY BENCH MARK STAMPING:  1 1973
                         DESIGNATION:          872 5943 1

MONUMENTATION:           Tidal Station disk                    VM#:        10604
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AG7167
SETTING CLASSIFICATION:  Bridge abutment                       OPUS PID:        
LATITUDE:   27° 10.8' N (  27.18000)          LONGITUDE:  82° 29.7' W ( -82.49500)


The primary bench mark is a disk set flush in the top of a 1.52 m (5.0 ft)
square NW abutment, 0.20 m (0.66 ft) from the north side of the abutment, 0.41 m
(1.33 ft) from the west side of abutment, 0.91 m (3.0 ft) east of the wood
piling retaining wall, 0.61 m (2.0 ft) north of the north side of the bridge,
and 0.91 m (3.0 ft) below bridge deck.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


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


                         BENCH MARK STAMPING:  5943 H 1983
                         DESIGNATION:          872 5943 H

MONUMENTATION:           Tidal Station disk                    VM#:        17181
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AG7745
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   27° 10.8' N (  27.18000)          LONGITUDE:  82° 29.9' W ( -82.49830)


The bench mark is set in the top of a concrete monument, 0.3 km (0.2 mi) west of
the bridge over the Intracoastal Waterway located at the junction of Blackburn
Point Road and Casey Key Road,  19.51 m (64.0 ft) NW of the junction of a
private drive and Blackburn Point Road, 15.09 m (49.5 ft) north of and across
the road from powerline pole #200-21, 12.62 m (41.4 ft) east of the centerline
of Casey Key Road, 5.64 m (18.5 ft) north of the centerline of Blackburn Point
Road, 15.09 m (49.5 ft) north of and across the road from powerline pole
#200-21, 0.61 m (2.0 ft) south of a witness post, and 0.09 m (0.3 ft) below
ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


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


                         BENCH MARK STAMPING:  F 634 2005
                         DESIGNATION:          F 634

MONUMENTATION:           Flange-encased Rod                    VM#:        19935
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  DJ3106
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   27° 10.8' N (  27.17997)          LONGITUDE:  82° 28.9' W ( -82.48225)


The bench mark is a stainless steel rod located 33.83 m (111.0 ft) north of the
approximate centerline of Blackburn Point Road, 10.39 m (34.1 ft) east-NE of the
approximate centerline of U.S.  Highway 41 southbound, 9.60 m (31.5 ft) west-SW
of the approximate centerline of U.S.  Highway 41 northbound, 2.50 m (8.2 ft)
north of the south curb face of the north median, and 0.33 m (1.1 ft) north of a
carsonite witness post.  The bench mark is a stainless steel rod driven to
refusal at a depth of 9.75 m (32.0 ft) with an NGS logo cap flush with the
ground and about 0.15 m (0.5 ft) above the level of U.S.  Highway 41, the datum
point being recessed 0.13 m (0.42 ft) below the level of the NGS logo cap.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


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


                         BENCH MARK STAMPING:  Z 699 2007
                         DESIGNATION:          Z 699

MONUMENTATION:           Survey disk                           VM#:        19936
AGENCY:                  Florida Dept. of Environmental
                         Protection (FLDEP)                    IDB PID#:  DL2737
SETTING CLASSIFICATION:  Round concrete monument               OPUS PID:        
LATITUDE:   27° 10.0' N (  27.16725)          LONGITUDE:  82° 29.5' W ( -82.49106)


The bench mark is a disk set in the top of a round concrete monument flush with
the ground and level with Casey Key Road (State Road 789), 12.3 m (40.5 ft)
north of the approximate extended centerline of the southernmost driveway at
3311 Casey Key Road (State Road 789), 10.2 m (33.4 ft) south of the approximate
extended centerline of the northernmost driveway at 3311 Casey Key Road (State
Road 789), 5.3 m (17.4 ft) east-NE of the approximate centerline of Casey Key
Road (State Road 789), and 0.4 m (1.4 ft) west of a carsonite witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


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


                         BENCH MARK STAMPING:   
                         DESIGNATION:          CREEK BRIDGE
                         ALIAS:                NO STAMPING

MONUMENTATION:           Survey disk                           VM#:        19937
AGENCY:                  Florida Department of Transportation
                         (FLDT)                                IDB PID#:        
SETTING CLASSIFICATION:  Bridge abutment curb                  OPUS PID:        
LATITUDE:   27° 10.1' N (  27.16831)          LONGITUDE:  82° 28.6' W ( -82.47703)


The bench mark is a disk set flush in the top of the SE bridge abutment curb
about 0.15 m (0.5 ft) above the level of U.S.  highway 41, 28.65 m (94.0 ft) NW
of a power pole, 7.35 m (24.1 ft) east-NE of the approximate centerline of U.S. 
Highway 41 northbound, and 0.18 m (0.6 ft) south of the SE end of a concrete
guardrail.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


                            T I D A L   D A T U M S 


Tidal datums at BLACKBURN POINT based on:

     LENGTH OF SERIES:      4 MONTHS
     TIME PERIOD:           July 1977 - October 1977
     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   =  0.516
     North American Vertical Datum              NAVD88 =  0.482
     MEAN HIGH WATER                            MHW    =  0.426
     MEAN TIDE LEVEL                            MTL    =  0.271
     MEAN SEA LEVEL                             MSL    =  0.265
     MEAN LOW WATER                             MLW    =  0.116
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     1 1973                                      2.859    2.433
     5943 H 1983                                 2.662    2.236
     F 634 2005                                  5.778    5.352
     Z 699 2007                                  3.044    2.618
     CREEK BRIDGE                                3.347    2.921


Foot Notes:

Geodetic heights of the bench marks meet all NOAA/NOS/NGS quality control
standards for Second Order, Class 1 leveling.  It is advised that a confirmation
set of levels be established for bench marks CREEK BRIDGE, F 634 2005, and Z 699
2007 to verify height differences before using tidal bench mark elevation
information.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  7 of  7

                                                                                
Station ID: 8725943                         PUBLICATION DATE:  06/03/2011
Name:       BLACKBURN POINT                                   
            FL
NOAA Chart: 11424                           Latitude:   27° 10.7' N (  27.17830)
USGS Quad:  LAUREL                          Longitude:  82° 29.7' W ( -82.49500)


                             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.