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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


To reach the tidal bench marks from north bound lane of U.S. Interstate Highway
93 and the Atlantic and Northern Avenues exits in Boston, proceed to the U.S.
Coast Guard Building at the intersection of Atlantic and Northern Avenues.  The
bench marks are in the vicinity of the U.S. Coast Guard Building, U.S. Custom
House, U.S. Post Office and at the intersection of Purchase and High Streets. 
The tide station is located on the right side of the U.S. Coast Guard Building
adjacent to Northern Avenue Bridge.


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


                 PRIMARY BENCH MARK STAMPING:  K 12 MASS G.S. 1936 14.292
                         DESIGNATION:          K 12

MONUMENTATION:           Tidal Station disk                        VM#:      185
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  MY0555
SETTING CLASSIFICATION:  Granite step


The primary bench mark is a disk set in the top of the east end of the first
step at the NW (main) entrance of the U.S. Coast Guard Building at the
intersection of Atlantic and Northern Avenues, 5.79 m (19.0 ft) north of a fire
hydrant, 1.62 M (5.3 ft) NE of the center of the doorway, 2.90 m (9.5 ft) SE of
the rounded curb at the intersection, and 0.21 m (0.7 ft) SW of the SW corner of
the Coast Guard Building, and 0.3 m (1 ft) above ground.



                         BENCH MARK STAMPING:  J 12 MASS. G.S. 1936 13.321
                         DESIGNATION:          844 3970 J 12

MONUMENTATION:           Bench Mark disk                           VM#:      184
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  MY0562
SETTING CLASSIFICATION:  Step


The bench mark is a disk set in the NE end of the third step of the westernmost
set of steps at the north entrance of the A. P. New England Office Building,
located at the intersection of Congress Street and Atlantic Avenue, 7.16 m (23.5
ft) SW of the SW curb of Atlantic Avenue, 6.64 m (21.8 ft) SW of the door to the
building, 3.99 m (13.1 ft) SE of the SE curb of Congress Street, 2.07 m (6.8 ft)
west of the center of the entrance, and 0.6 m (2 ft) above the sidewalk.

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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


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


                         BENCH MARK STAMPING:  NO 15 1950
                         DESIGNATION:          844 3970 TIDAL 15

MONUMENTATION:           Tidal Station disk                        VM#:      186
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  MY0556
SETTING CLASSIFICATION:  Granite foundation


The bench mark is a disk set in the top of the granite ledge around the base of
the U.S. Custom House at the intersection of India and Central Streets, 6.40 m
(21.0 ft) east of the center of the entrance to the building, 5.03 m (16.5 ft)
west of the SE corner of the building, 0.3 m (1 ft) south of the south face of
the building, and 0.3 m (1 ft) above the sidewalk.



                         BENCH MARK STAMPING:  NO 16 1973
                         DESIGNATION:          844 3970 TIDAL 16

MONUMENTATION:           Tidal Station disk                        VM#:      187
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID:         
SETTING CLASSIFICATION:  Granite bulkhead cap


The bench mark is a disk set in the top of the granite bulkhead cap located near
Northern Avenue and the U.S. Coast Guard building,  12.89 m (42.3 ft) south of
the northernmost bollard on the seawall, 9.60 m (31.5 ft) SE of the NE corner of
the building, and 0.43 m (1.4 ft) west of the west edge of the cap.

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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


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


                         BENCH MARK STAMPING:  FED 2 ELEV 20.186
                         DESIGNATION:          844 3970 TIDAL 1

MONUMENTATION:           Tidal Station disk                        VM#:      190
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  MY0557
SETTING CLASSIFICATION:  Stone step


The bench mark is a disk set in the south end of the bottom step of the
Devonshire Street entrance of the U.S. Post Office which is in the business
district bounded by Devonshire, Water, Congress and Milk Streets, 7.62 m (25.0
ft) east of the centerline of Devonshire Street, and 2.19 m (7.2 ft) south of
the centerline of the steps leading to the post office.



                         BENCH MARK STAMPING:  3970 A 1990
                         DESIGNATION:          844 3970 A

MONUMENTATION:           Tidal Station disk                        VM#:      194
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Interstate overpass foundation


The bench mark is a disk set in the NE corner of the concrete foundation
supporting an overpass exit of the I-93 Expressway at the intersection of
Purchase and High Streets, 29.26 m (96.0 ft) SE of the southernmost corner of
the building at 200 High Street, 5.18 m (17.0 ft) west of the centerline of
Purchase Street, 3.66 m (12.0 ft) east of the centerline of Surface Street, and
0.21 m (0.7 ft) above the sidewalk.

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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


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


                         BENCH MARK STAMPING:  3970 B 1990
                         DESIGNATION:          844 3970 B

MONUMENTATION:           Tidal Station disk                        VM#:      195
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Interstate overpass foundation


The bench mark is a disk set in the SE corner of the concrete foundation
supporting the southbound lanes of the I-93 Expressway at the intersection of
Surface and India Streets, 17.83 m (58.5 ft) east of the eastern corner of the
Custom House Building, 12.19 m (40.0 ft) west of the centerline of Surface
Street, 6.40 m (21.0 ft) south of the centerline of India Street, and 0.21 m
(0.7 ft) above the sidewalk.



                         BENCH MARK STAMPING:  3970 C 1991
                         DESIGNATION:          844 3970 C

MONUMENTATION:           Tidal Station disk                        VM#:    13804
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Granite bridge abutment


The bench mark is a disk set in the granite bridge abutment on the western side
of the Northern Avenue Swing Bridge located at the east face of the Hook Lobster
Company building, 24.63 m (80.8 ft) south of the SE corner of the U.S. Coast
Guard building, 13.81 m (45.3 ft) ESE of the NW corner of the lobster company
building, and 0.34 m (1.1 ft) WNW of the south edge of the granite bridge
abutment.

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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


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


                         BENCH MARK STAMPING:  3970 D 2000
                         DESIGNATION:          844 3970 D

MONUMENTATION:           Tidal Station disk                        VM#:    16235
AGENCY:                  National Geodetic Survey (NGS)            PID#:  AJ4030
SETTING CLASSIFICATION:  Granite sea wall cap


The bench mark is a disk set in the granite bulkhead cap between two metal
bollards of the seawall at the Christopher Columbus Park located at the
intersection of Atlantic Avenue and Richmond Streets, 31.28 m (102.6 ft) ENE of
the east face of the Christopher Columbus Statue,  and 7.50 m (24.6 ft) ENE of
the granite foundation of the third lamp post north of the south end of the
granite steps at the park entrance.

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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' W


                            T I D A L   D A T U M S 


Tidal datums at BOSTON, BOSTON HARBOR based on:

     LENGTH OF SERIES:      19 Years
     TIME PERIOD:           January 1983 - December 2001
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:   


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

     HIGHEST OBSERVED WATER LEVEL (02/07/1978)         =  4.601
     MEAN HIGHER HIGH WATER                     MHHW   =  3.131
     MEAN HIGH WATER                            MHW    =  2.996
     North American Vertical Datum              NAVD88 =  1.678
     MEAN SEA LEVEL                             MSL    =  1.585
     MEAN TIDE LEVEL                            MTL    =  1.550
     MEAN LOW WATER                             MLW    =  0.103
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (03/24/1940)         = -1.135

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     K 12 MASS G.S. 1936 14.292                  5.784    2.787
     J 12 MASS. G.S. 1936 13.321                 5.472    2.476
     NO 15 1950                                  5.059    2.063
     NO 16 1973                                  4.946    1.950
     FED 2 ELEV 20.186                           7.573    4.576
     3970 A 1990                                 6.420    3.423
     3970 B 1990                                 4.719    1.722
     3970 C 1991                                 6.268    3.272
     3970 D 2000                                 4.248    1.252


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

                                                                                
Station ID: 8443970                                PUBLICATION DATE:  04/21/2003
Name:       BOSTON, BOSTON HARBOR                             
            MASSACHUSETTS
NOAA Chart: 13272                                  Latitude:         42° 21.3' N
USGS Quad:  BOSTON SOUTH                           Longitude:        71°  3.1' 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.