Superseded Bench Mark Sheet for 8449130, Nantucket Island MA

Present Epoch

Printable version

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


To reach the tidal bench marks from mainland it is necessary to take a ferry
boat either from Woods Hole or Hyannis.  Reservations are required for vehicles
during the summer months.  Nantucket is also serviced by air from the airports
in Hyannis and Boston.  The tide gage and staff are in the town of Nantucket at
the ferry terminal.  The bench marks are within a 1 mile (2 km) radius of the
tide station.


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


                 PRIMARY BENCH MARK STAMPING:  NO 25 1968

MONUMENTATION:           Survey Disk                               VM#:      209
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Curb


The bench mark is at the intersection of Broad Street and Easy Street and is in
line with the extended centerline of Easy Street, 29.2 feet (8.9 m) north of the
centerline of Broad Street, 14.4 feet (4.4 m) NE of the NE face of a 3-foot (0.9
m) fire hydrant, 13.2 feet (4.0 m) east of a 3.5 x 3.5 x 4.3 foot (1.1 x 1.1 x
1.3 m) transformer junction box, set in the top of a concrete curb, and 1.2 feet
(0.4 m) above sidewalk level.



                         BENCH MARK STAMPING:  NO 21 RESET 1966

MONUMENTATION:           Survey Disk                               VM#:      206
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Block


The bench mark is in the vicinity of the intersection of Main Street and New
Whale Street, 129 feet (39 m) south of the centerline of Straight Wharf, 100.7
feet (30.7 m) NE of the NE corner of A&P Store, and 28.5 feet (8.7 m) SW of the
centerline of New Whale Street, and set in the top of a 1 foot x 1 foot concrete
block in the easternmost portion of the A&P, 5&10 parking lot, 0.4 foot (0.1 m)
above the parking lot level.

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


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


                         BENCH MARK STAMPING:  NO 22 1934

MONUMENTATION:           Survey Disk                               VM#:      207
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Block


The primary bench mark is 59.5 feet (18.1 m) north of the NE corner of the
intersection of Main Street and South Water Street, 28.6 feet (8.7 m) NW of the
NW corner of Dartmouth Beaver Bedford Building (Pacific Club Building), 16.5
feet (5.0 m) east of the centerline of South Water Street, level with the
sidewalk, and set in the concrete block in the east sidewalk along South Water
Street.



                         BENCH MARK STAMPING:  NO 23 1934

MONUMENTATION:           Survey Disk                               VM#:      208
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Runway


The bench mark is at the NW corner of the intersection of Chestnut Street and
South Water Street at the SE corner of Central Fire Station (presently occupied
by Nantucket Police Department), 37.0 feet (11.3 m) west of the centerline of
South Water Street, 23.6 feet (7.2 m) north of the centerline of Chestnut
Street, 1.1  feet (0.3 m) east of the west face of the SE cornerstone inscribed
1929,  and is set in a concrete runway at grade.

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


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


                         BENCH MARK STAMPING:  9130 G 1976

MONUMENTATION:           Survey Disk                               VM#:      210
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Retaining Wall


The bench mark is in the NE corner of the intersection of Broad Street and North
Beach Street, 50.6 feet (15.4 m) SE of the SW corner of Nantucket Yacht Club
tennis courts, 46.0 feet (14.0 m) north of the entrance to Nantucket Bike Shop
II, 3 feet (1 m) north of a brick sidewalk and just below a sign inscribed
Steamboat Wharf 1774, 1.0 foot (0.3 m) above sidewalk level and set flush in the
top of a concrete retaining wall.



                         BENCH MARK STAMPING:  9130 H

MONUMENTATION:           Survey Disk                               VM#:      211
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is at the intersection of Walsh Street and Harbor View Way, 100.7
feet (30.7 m) SW of the flagpole on the White Elephant property, 19.4 feet (5.9
m) east of the extended centerline of Walsh Street, and 14.0 feet (4.3 m) north
of the centerline of a boat ramp that is at the outside corner of the
intersection of Harbor View Way and Walsh Street, set in the west corner of a
6.4 x 8.1 foot (2.0 x 2.5 m) concrete storm sewer check trap, and 0.1 foot (0.03
m) above road level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  8

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


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


                         BENCH MARK STAMPING:  9130 K 1981

MONUMENTATION:           Survey Disk                               VM#:      212
AGENCY:                                                            PID#:  AJ4032
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is in the SW corner of the Coast Guard Base at Brant Point, 98.5
feet (30.0 m) south of the SE corner of a garage, 79.0 feet (24.1 m) SW of the
south corner of the main Coast Guard building, and 53.0 feet (16.2 m) north of
the south face of a bulkhead.  The bench mark is crimped to the top of a
galvanized steel rod driven 48 feet (15 m) to refusal, encased in a 6-inch PVC
pipe and kickblock, and 0.1 foot (0.03 m) below ground.



                         BENCH MARK STAMPING:  9130 L 1981

MONUMENTATION:           Survey Disk                               VM#:      213
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is in the NE corner of the Coast Guard Base at Brant Point, 86.0
feet (26.2 m) NE of the NE face of an old lighthouse, 28.3 feet (8.6 m) east of
the east face of the 5 x 5 foot (2 x 2 m) white building beneath range marker,
18.0 feet (5.5 m) south of the centerline of Easton Street, and 3.5 feet (1.1 m)
south of the NE fence corner of the base.  The bench mark is crimped to the top
of a galvanized steel rod driven 56 feet (17 m) to refusal, encased in 6-inch
PVC pipe and kickblock, and 0.2 foot (0.06 m) below ground.

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


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


                         BENCH MARK STAMPING:  NO STAMPING 1

MONUMENTATION:           Chiseled cross-cut                        VM#:      214
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete retaining wall


The bench mark is at 25 Hulbert Street, in the top of the western wing of a
concrete retaining wall of Mr. Stephens house, opposite a fire hydrant which is
the second hydrant from the curve at the intersection of Hulbert and Easton
Streets, 0.25 mile (0.4 km) NW from the old Brant Point Lighthouse, 17.0 feet
(5.2 m) SW of the north face of a concrete beach retaining wall, 16.0 feet (4.9
m) NE of the centerline of Hulbert Street, and 0.8 foot (0.2 m) NE of the NW
corner of the porch, and is a chiseled cross cut in the top of the western wing
of the concrete retaining wall level with the ground.  (Note: Bench mark was
historically referred to as 14 1910.)



                         BENCH MARK STAMPING:  NO STAMPING 2

MONUMENTATION:           Chiseled cross-cut                        VM#:      215
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete flagpole base


The bench mark is at 25 Hulbert Street on the property of Mr. Stephens house, 
opposite a fire hydrant which is the second hydrant from the curve at the
intersection of Hulbert and Easton Streets, 0.25 mile (0.4 km) NW from the old
Brant Point Lighthouse, 19.8 feet (6.0 m) SE of the NW retaining wall around the
lawn, 2.4 feet (0.7 m) south of the face of the concrete retaining wall, 1.0
foot (0.3 m) west of the edge of a concrete walk to beach, and is chisled in
concrete which formerly formed a base for a flagpole, 0.1 foot (0.03 m) below
grade.  (Note: Bench mark was historically referred to as 15 1910.)

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


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


                         BENCH MARK STAMPING:  NO STAMPING 3

MONUMENTATION:           Brick Point                               VM#:      216
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Small Mat Foundation


The bench mark is the upper of two stepped rows of bricks forming the foundat-
ion for the paint locker building, at the NW corner of the paint locker, on
Coast Guard Reservation at Brant Point, 83.1 feet (25.3 m) NE of the SE corner
of the USCG boathouse building, 68.0 feet (20.7 m) east of the NE corner of the
USCG boathouse building, 5.2 feet (1.6 m) west of the center of the entrance way
to the paint locker room in the USCG base, and is level with grade (sand). 
(Note: Bench mark was historically referred to as 17 1910.)



                         BENCH MARK STAMPING:  NO STAMPING 4

MONUMENTATION:           Concrete Post                             VM#:      217
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Post


The bench mark is the center of a 0.5 foot (0.2 m) square granite post
projecting 0.5 foot (0.2 m) above ground at the pedestrian entrance to Brant
Point Observation Tower, with the top of the post inscribed U.S.L.H.E., 10.7
feet (3.3 m) west of the center of the manhole in the south side of the approach
driveway to the beach, 7.5 feet (2.3 m) SSW of the centerline of Easton Street,
2.0 feet (0.6 m) east of telephone pole #52, and is 0.8 foot (0.2 m) above grade
(sand).  (Note: Bench mark was historically referred to as 24 1953.)

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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' W


                            T I D A L   D A T U M S 


Tidal datums at NANTUCKET ISLAND, NANTUCKET SOUND based on:

     LENGTH OF SERIES:      16 YEARS
     TIME PERIOD:           1969-1984
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8452660 NEWPORT, R.I.


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

     HIGHEST OBSERVED WATER LEVEL (02/07/1978)         =   6.37
     MEAN HIGHER HIGH WATER                     MHHW   =   3.60
     MEAN HIGH WATER                            MHW    =   3.26
     MEAN TIDE LEVEL                            MTL    =   1.73
     MEAN LOW WATER                             MLW    =   0.20
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (02/12/1981)         =  -1.90

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 25 1968                                  7.60      4.34
     NO 21 RESET 1966                            6.89      3.63
     NO 22 1934                                  9.33      6.07
     NO 23 1934                                  9.14      5.88
     9130 G 1976                                 7.76      4.50
     9130 H                                      6.00      2.74
     9130 K 1981                                 5.27      2.01
     9130 L 1981                                 6.41      3.15
     NO STAMPING 1                               9.27      6.01
     NO STAMPING 2                               9.17      5.91
     NO STAMPING 3                               4.50      1.24
     NO STAMPING 4                               7.98      4.72


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

                                                   PUBLICATION DATE:  06/05/1992
Station ID: 8449130                                SUPERCEDED DATE:   04/21/2003
Name:       NANTUCKET ISLAND, NANTUCKET SOUND                 
            MASSACHUSETTS
NOAA Chart: 13241                                  Latitude:         41° 17.1' N
USGS Quad:  VINEYARD HAVEN                         Longitude:        70°  5.8' 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.

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