U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  06/04/1991
Station ID: 8440273                                SUPERCEDED DATE:   04/21/2003
Name:       SALISBURY POINT, MERRIMACK RIVER                  
            MASSACHUSETTS
NOAA Chart: 13282                                  Latitude:         42° 50.3' N
USGS Quad:  NEWBURYPORT WEST                       Longitude:        70° 54.5' W


To reach the bench marks from the Amesbury exit (#55) of Inter-state Highway
495, proceed east on State Road 110 for 1.1 miles    (1.8 km) to Merrill Street,
then SW on Merrill Street for 0.8 mile (1.3 km) to the swing bridge over
Merrimack River.  The bench marks are near the bridge and Interstate Highway
495.  The tide gage and staff were on the east bridge fender.


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


                 PRIMARY BENCH MARK STAMPING:  0273 A 1989

MONUMENTATION:           Survey Disk                               VM#:     1443
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Bedrock


The primary bench mark is set flush in an outcropping of bedrock, 106 feet (32
m) NE of power pole #83/1 on the north side of Old Merrill Street, 29.6 feet
(9.0 m) west of power pole #2, and 26 feet (8 m) NNW of the centerline of Old
Merrill Street.



                         BENCH MARK STAMPING:  4869

MONUMENTATION:           Survey Disk                               VM#:     1444
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Sidewalk


The bench mark is set flush in the concrete sidewalk at the NE end of the
Interstate Highway 95 bridge (Whittier Memorial Bridge) over Merrimack River,
2.8 feet (0.9 m) east of the center of a manhole cover in the sidewalk, 2.2 feet
(0.7 m) SW of the north end of the sidewalk, and 1.4 feet (0.4 m) NW of the face
of the granite retaining wall.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  06/04/1991
Station ID: 8440273                                SUPERCEDED DATE:   04/21/2003
Name:       SALISBURY POINT, MERRIMACK RIVER                  
            MASSACHUSETTS
NOAA Chart: 13282                                  Latitude:         42° 50.3' N
USGS Quad:  NEWBURYPORT WEST                       Longitude:        70° 54.5' W


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


                         BENCH MARK STAMPING:  NO STAMPING 1

MONUMENTATION:           Survey Disk                               VM#:     1445
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Abutment


The bench mark is set flush in the NE concrete abutment of the Main Street
bridge over Merrimack River, 119 feet (36 m) south of the centerline of Old
Merrill Street, 16.4 feet (5.0 m) east of the centerline of Main Street, and
13.0 feet (4.0 m) north of a steel power pole with electric meter on the east
side of the bridge.



                         BENCH MARK STAMPING:  NO STAMPING 2

MONUMENTATION:           Survey Disk                               VM#:     1446
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Abutment


The bench mark is set flush in the SW concrete abutment of the Main Street
bridge over the Merrimack River, 15.1 feet (4.6 m) WSW of the centerline of Main
Street, 13.4 feet (4.1 m) NNE of the north corner of the bridge tender's house,
and 0.7 foot    (0.2 m) NW of the SE edge of the abutment.



                         BENCH MARK STAMPING:  NO STAMPING 3

MONUMENTATION:           Rivet                                     VM#:     1447
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Wingwall


The bench mark is set flush in the SE concrete wingwall of the Essex-Merrimack
suspension bridge on the south side of Deer Island, 177.1 feet (54.0 m) north of
the NW corner of the residence at #3 Spofford Street, and 23.2 feet (7.1 m) east
of the centerline of Spofford Street.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  06/04/1991
Station ID: 8440273                                SUPERCEDED DATE:   04/21/2003
Name:       SALISBURY POINT, MERRIMACK RIVER                  
            MASSACHUSETTS
NOAA Chart: 13282                                  Latitude:         42° 50.3' N
USGS Quad:  NEWBURYPORT WEST                       Longitude:        70° 54.5' W


                            T I D A L   D A T U M S 


Tidal datums at SALISBURY POINT, MERRIMACK RIVER based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           JULY-SEPTEMBER 1989
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8440466 NEWBURYPORT


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

     HIGHEST OBSERVED WATER LEVEL (10/18/1989)         =   9.68
     MEAN HIGHER HIGH WATER                     MHHW   =   8.28
     MEAN HIGH WATER                            MHW    =   7.82
     MEAN TIDE LEVEL                            MTL    =   4.01
     MEAN LOW WATER                             MLW    =   0.20
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (10/13/1989)         =  -0.91



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     0273 A 1989                                24.66     16.84
     4869                                       67.58     59.76
     NO STAMPING 1                              27.90     20.08
     NO STAMPING 2                              27.47     19.65
     NO STAMPING 3                              34.46     26.64


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

                                                   PUBLICATION DATE:  06/04/1991
Station ID: 8440273                                SUPERCEDED DATE:   04/21/2003
Name:       SALISBURY POINT, MERRIMACK RIVER                  
            MASSACHUSETTS
NOAA Chart: 13282                                  Latitude:         42° 50.3' N
USGS Quad:  NEWBURYPORT WEST                       Longitude:        70° 54.5' 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.