Superseded Bench Mark Sheet for 8455189, Westerly Pawcatuck RI

Present Epoch

Printable version

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

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 8455189                                SUPERCEDED DATE:   04/21/2003
Name:       WESTERLY, PAWCATUCK RIVER                         
            RHODE ISLAND
NOAA Chart: 12314                                  Latitude:         41° 22.9' N
USGS Quad:  WATCH HILL                             Longitude:        71° 49.9' W


To reach the tidal bench marks from the intersection of Main and Broad Streets
in Westerly, proceed south on Main Street for 0.6 mile (1.0 km) to the
intersection of Main, Margin, and Beach Streets.  The bench marks are located in
the stone retaining wall along the river and in a flagstone walk.  The tide gage
and staff were located on a dock on the east side of the river in the vicinity
of the steps from Margin Street. NOTE:  Descriptions are based on bench mark
recovery in 1961.


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


                 PRIMARY BENCH MARK STAMPING:  NO 2 1917 4.203 FT

MONUMENTATION:           Survey Disk                               VM#:     2216
AGENCY:                                                            PID#:  LW0748
SETTING CLASSIFICATION:  Stone Retaining Wall


The bench mark is set in a stone retaining wall, 641 feet (195 m) SW of the
intersection of Main, Margin, and Beach Streets, 385 feet (117 m) south of Bench
Mark NO 1 1917 4.656 FT, 14.5 feet (4.4 m) NW of the NW curb of Margin Street,
6.5 feet (2.0 m) SE of a turn in the retaining wall, and about 3 feet (1 m)
below the level of Margin Street.



                         BENCH MARK STAMPING:  NO 1 1917 4.656 FT

MONUMENTATION:           Survey Disk                               VM#:     2215
AGENCY:                                                            PID#:  LW0747
SETTING CLASSIFICATION:  Flagstone Walk


The bench mark is set in a flagstone walk at the foot of the granite steps
leading down from a sidewalk across from the house at 4 Margin Street, about 256
feet (78 m) SW of the intersection of Main, Margin, and Beach Streets, 13.5 feet
(4.1 m) SE of the SE side of the sea wall, 12 feet (4 m) NW of the NW curb of
Margin Street, 1.1 feet (0.3 m) west of the north corner of the bottom step, and
about 5 feet (2 m) below the level of Margin Street.

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

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 8455189                                SUPERCEDED DATE:   04/21/2003
Name:       WESTERLY, PAWCATUCK RIVER                         
            RHODE ISLAND
NOAA Chart: 12314                                  Latitude:         41° 22.9' N
USGS Quad:  WATCH HILL                             Longitude:        71° 49.9' W


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


                         BENCH MARK STAMPING:  BM B1 1961

MONUMENTATION:           Survey Disk                               VM#:     2217
AGENCY:                                                            PID#:  LW0746
SETTING CLASSIFICATION:  Stone Retaining Wall


The bench mark is set in the top of a stone retaining wall, on the east bank of
the Pawcatuck River, 176 feet (54 m) NE of Bench Mark NO 1 1917 4.656 FT, 80
feet (24 m) west of the intersection of Main, Margin and Beach Streets, 46.5
feet (14.2 m) SW of the NE end of a turn in the retaining wall, 27 feet (8 m) NW
of the NW curb of Margin Street, and about 5 feet (2 m) below the level of
Margin Street.

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

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 8455189                                SUPERCEDED DATE:   04/21/2003
Name:       WESTERLY, PAWCATUCK RIVER                         
            RHODE ISLAND
NOAA Chart: 12314                                  Latitude:         41° 22.9' N
USGS Quad:  WATCH HILL                             Longitude:        71° 49.9' W


                            T I D A L   D A T U M S 


Tidal datums at WESTERLY, PAWCATUCK RIVER based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           SEPTEMBER 1961
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8461490 NEW LONDON, CT


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

     HIGHEST OBSERVED WATER LEVEL (09/21/1938)         =  12.00
     MEAN HIGHER HIGH WATER                     MHHW   =   3.14
     MEAN HIGH WATER                            MHW    =   2.84
     MEAN TIDE LEVEL                            MTL    =   1.52
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   1.00
     MEAN LOW WATER                             MLW    =   0.20
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (09/26/1961)         =  -0.24

   * NGVD reference based on elevations published in Quad 410713, 1970, and NOS
     leveling of 1961. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 2 1917 4.203 FT                          5.26      2.42
     NO 1 1917 4.656 FT                          5.62      2.78
     BM B1 1961                                  4.97      2.13


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

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 8455189                                SUPERCEDED DATE:   04/21/2003
Name:       WESTERLY, PAWCATUCK RIVER                         
            RHODE ISLAND
NOAA Chart: 12314                                  Latitude:         41° 22.9' N
USGS Quad:  WATCH HILL                             Longitude:        71° 49.9' 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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