U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


To reach the water level station from either direction of U.S. Interstate 93,
take exit 23 and follow the signs to the Financial District.  Proceed south on
Surface Road until it becomes Purchase Road at the intersection with High
Street.  Continue south on Purchase Road for about three blocks.  At the
intersection with Congress Street, turn SSE (left) and then NE (left) onto
Atlantic Avenue.  Proceed on Atlantic Avenue for one block to the intersection
with Seaport Blvd, proceed straight and after the James Hook & Company building
turn SE (right) to Northern Avenue and the U.S. Coast Guard Building.  The water
level station is SE of the U.S. Coast Guard Building at the NW end of the
Northern Avenue bridge.  The bench marks are in the vicinity of the U.S. Coast
Guard Building, Marriott's Custom House, and the U.S. Post Office.


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


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

MONUMENTATION:           Tidal Station disk                    VM#:        13804
AGENCY:                  National Ocean Service (NOS)          IDB PID:         
SETTING CLASSIFICATION:  Granite bridge abutment               OPUS PID:        
LATITUDE:   42° 21.3' N (  42.35481)          LONGITUDE:  71°  3.0' W ( -71.05047)


The primary bench mark is a disc set in the top of the granite bulkhead cap
adjacent to the SW corner of the Northern Avenue Bridge at its NW end and the
burnt remains of the James Hook and Company Building.  The bench mark is located
12.89 m (42.29 ft) south of the northernmost bollard on the seawall, and 0.42 m
(1.38 ft) west of the west edge of the cap.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


                         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)                              IDB PID#:  MY0556
SETTING CLASSIFICATION:  Granite foundation                    OPUS PID:        
LATITUDE:   42° 21.5' N (  42.35886)          LONGITUDE:  71°  3.2' W ( -71.05342)


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:  FED 2 ELEV 20.186
                         DESIGNATION:          844 3970 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:          190
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  MY0557
SETTING CLASSIFICATION:  Stone step                            OPUS PID:        
LATITUDE:   42° 21.4' N (  42.35711)          LONGITUDE:  71°  3.4' W ( -71.05722)


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.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


                         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)        IDB PID#:  AJ4030
SETTING CLASSIFICATION:  Granite sea wall cap                  OPUS PID#: AJ4030
LATITUDE:   42° 21.7' N (  42.36122)          LONGITUDE:  71°  2.0' W ( -71.03414)


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  4 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


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


                         BENCH MARK STAMPING:  E 44 1978
                         DESIGNATION:          E 44

MONUMENTATION:           Bench Mark disk                       VM#:        18189
AGENCY:                  National Geodetic Survey              IDB PID#:  MY2079
SETTING CLASSIFICATION:  Door Sill                             OPUS PID:        
LATITUDE:   42° 21.5' N (  42.35872)          LONGITUDE:  71°  3.5' W ( -71.05908)


The bench mark is a disk set in a 0.46 m (1.5 ft) wide door sill at a fire exit
door located in the west face of the school committee building at 26 Court
Street, 32.00 m (105.0 ft) south of the south curb return of Court Street, 22.86
m (75.0 ft) north of the south curb return of Court Street, 22.89 m (75.1 ft)
south of the extension of the north face of the building, 9.45 m (31.0 ft) north
of the center of the main west side entrance to the building, and 2.44 m (8.0
ft) east of the east curb return of Court Square.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


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


                         BENCH MARK STAMPING:  H 44 1978
                         DESIGNATION:          H 44

MONUMENTATION:           Bench Mark disk                       VM#:        18190
AGENCY:                  National Geodetic Survey              IDB PID#:  MY2080
SETTING CLASSIFICATION:  Window Ledge                          OPUS PID:        
LATITUDE:   42° 21.3' N (  42.35561)          LONGITUDE:  71°  3.5' W ( -71.05781)


The bench mark is a disk set horizontally in a 0.79 m (2.6 ft) wide ledge for a
large window located in the west face of the 100 Franklin Building, 20.8 m (68.2
ft) south of the center of the west entrance of the building, 9.08 m (29.8 ft)
north of the SW corner of the building, and 2.47 m (8.1 ft) east of the east
curb return of Arch Street.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


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


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

MONUMENTATION:           Bench Mark disk                       VM#:        20267
AGENCY:                  USC&GS                                IDB PID:         
SETTING CLASSIFICATION:  Steps                                 OPUS PID:        
LATITUDE:   42° 21.2' N (  42.35361)          LONGITUDE:  71°  3.2' W ( -71.05333)


The bench mark is a brass disc set flush in the third step at the southernmost
set of steps, at the corner entrance to the Atlantic Wharf building located
11.05 m (36.3 ft) from the face of the curb at the center of the crosswalk on
the SE side of Atlantic avenue, 8.23 m (27.0 ft) NE of a fire hydrant on the
east side of Congress street, and 3.83 m (12.6 ft) SW from the door sill at the
center of both doors at the entrance to the Atlantic Wharf building.



                         BENCH MARK STAMPING:  L 12 1936
                         DESIGNATION:          844 3970 L 12

MONUMENTATION:           Bench Mark disk                       VM#:        22878
AGENCY:                  US Coast and Geodetic Survey          IDB PID:         
SETTING CLASSIFICATION:  Granite step                          OPUS PID:        
LATITUDE:   42° 21.5' N (  42.35872)          LONGITUDE:  71°  3.4' W ( -71.05694)


The bench mark is a disk set atop the bottom step on the east side of the
entrance to the old state house located at the corner of Congress Street and
State Street, 15.85m (52.0 ft) north of the SE corner of the old state house,
2.74m (9.0 ft) west of the east side of the sidewalk running along the street,
and 0.44m (1.4 ft) east of the west side brick wall of the old state house.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  7 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


                            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 (01/04/2018)         =  4.622
     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

     3970 C 1991                                 6.272    3.275
     NO 15 1950                                  5.072    2.076
     FED 2 ELEV 20.186                           7.589    4.593
     3970 D 2000                                 4.250    1.254
     E 44 1978                                  12.576    9.579
     H 44 1978                                   8.426    5.430
     J 12 RESET MASS. G.S. 1936 13.321           5.471    2.474
     L 12 1936                                   9.462    6.466


Foot Notes:

Bench mark L 12 1936 is based on one differential leveling connection and does
not meet the quality control standards of the NOS. Therefore, caution should be
used when deriving elevations for this mark.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  8 of  8

                                                                                
Station ID: 8443970                         PUBLICATION DATE:  12/12/2018
Name:       BOSTON, BOSTON HARBOR                             
            MA
NOAA Chart: 13272                           Latitude:   42° 21.2' N (  42.35392)
USGS Quad:  BOSTON SOUTH                    Longitude:  71°  3.0' W ( -71.05033)


                             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.