U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 01/30/1986
Station ID: 8517401 SUPERCEDED DATE: 04/21/2003
Name: WARDS ISLAND, HELL GATE
NEW YORK
NOAA Chart: 12339 Latitude: 40° 47.2' N
USGS Quad: CENTRAL PARK Longitude: 73° 55.3' W
To reach the tidal bench marks from the Triboro Bridge, take the Downing Stadium
exit and follow the road beneath the bridge 1 mile (1.6 km) to the stadium
parking, continue over a small bridge and drive 0.2 mile (0.3 km) to a Y, bear
left and continue 0.2 mile (0.3 km) to the second entrance to the Wards Island
Water Pollution Control Plant, enter the plant and keep to the right, following
the road 0.3 mile (0.5 km) to the pier. The bench marks are in the vicinity of
the plant pier. The tide gage and staff were on the south end of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 7401 A 1981
MONUMENTATION: Survey Disk VM#: 2323
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Seawall
The bench mark is flush in top of a concrete seawall, 47 feet (14 m) east of the
roadway leading to the Wards Island Sewage Treatment Plant pier, 5.9 feet (1.8
m) north of the south end of the pier, 0.8 foot (0.2 m) south of the
southernmost bollard on the pier, and 1 foot (0.3 m) above the surface of the
pier parking area.
BENCH MARK STAMPING: 7401 B 1981
MONUMENTATION: Survey Disk VM#: 2324
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Wall
The bench mark is set flush in in top of the easternmost north-south wall of the
chorination tanks, 110 feet (34 m) NNW of Bench Mark 7401 A 1981, 46 feet (14 m)
west of the concrete outer face of the pier, 1.6 feet (0.5 m) north of the north
edge of the southernmost east-west wall of the tanks, and set 4.0 feet (1.2 m)
below the top of the east-west wall, and 3.8 feet (1.2 m) above a sidewalk
running around the tanks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 01/30/1986
Station ID: 8517401 SUPERCEDED DATE: 04/21/2003
Name: WARDS ISLAND, HELL GATE
NEW YORK
NOAA Chart: 12339 Latitude: 40° 47.2' N
USGS Quad: CENTRAL PARK Longitude: 73° 55.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7401 C 1981
MONUMENTATION: Survey Disk VM#: 2325
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Wall
The bench mark is set flush at the SE corner of the concrete wall surrounding
some final settling tanks, 400 feet (122 m) SSE of Bench Mark 7401 D 1983, 191
feet (58 m) east of the SE corner of the south end of a wing on a long
north-south oriented building, 17 feet (5 m) north of the centerline of the road
leading to the pier, 0.9 foot (0.3 m) west of the east face of the east wall,
and 0.7 foot (0.2 m) north of the south face of the south wall, and set 1.2 feet
(0.4 m) above the surface of the road.
BENCH MARK STAMPING: 7401 D 1981
MONUMENTATION: Survey Disk VM#: 2326
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Door Sill
The bench mark is set flush in the door sill of the east door in the
southernmost of two two-story sections of a long north-south oriented building,
280 feet (85 m) west of Bench Mark 7401 A 1981, 140 feet (43 m) west of the
southernmost of two flagpoles, 1.0 foot (0.3 m) north of the south side of the
doorway, 0.7 foot (0.2 m) west of the east face of the buildings foundation, and
set 2.5 feet (0.8 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 01/30/1986
Station ID: 8517401 SUPERCEDED DATE: 04/21/2003
Name: WARDS ISLAND, HELL GATE
NEW YORK
NOAA Chart: 12339 Latitude: 40° 47.2' N
USGS Quad: CENTRAL PARK Longitude: 73° 55.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7401 E 1981
MONUMENTATION: Survey Disk VM#: 2327
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Abutment
The bench mark is set flush in the foundation of the west abutment of the
railroad bridge over the East River about 0.5 mile (0.8 km) north of the Triboro
Bridge over the East River, 500 feet (152 m) SSE of Bench Mark 7401 C 1981, 67
feet (20 m) west of the south end of a rock retaining wall on the west bank of
the East River, 7.5 feet (2.3 m) south of a chain link fence, and set 0.5 foot
(0.2 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 01/30/1986
Station ID: 8517401 SUPERCEDED DATE: 04/21/2003
Name: WARDS ISLAND, HELL GATE
NEW YORK
NOAA Chart: 12339 Latitude: 40° 47.2' N
USGS Quad: CENTRAL PARK Longitude: 73° 55.3' W
T I D A L D A T U M S
Tidal datums at WARDS ISLAND, HELL GATE based on:
LENGTH OF SERIES: 107 HIGH WATERS & LO
TIME PERIOD: MAY 7-JUNE 30, 1981
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8518750 THE BATTERY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (06/02/1981) = 7.92
MEAN HIGHER HIGH WATER MHHW = 6.73
MEAN HIGH WATER MHW = 6.37
MEAN TIDE LEVEL MTL = 3.36
MEAN LOW WATER MLW = 0.35
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (06/02/1981) = -1.04
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
7401 A 1981 13.51 7.14
7401 B 1981 17.47 11.10
7401 C 1981 21.63 15.26
7401 D 1981 24.41 18.04
7401 E 1981 23.48 17.11
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 01/30/1986
Station ID: 8517401 SUPERCEDED DATE: 04/21/2003
Name: WARDS ISLAND, HELL GATE
NEW YORK
NOAA Chart: 12339 Latitude: 40° 47.2' N
USGS Quad: CENTRAL PARK Longitude: 73° 55.3' 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.