U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
To reach the tidal bench marks from the intersection of Washington Street (State
Route 136) and Water Street in South Norwalk, at the west end of the Route 136
bridge over the Norwalk River, proceed south on South Water Street for 0.3 km
(0.2 mi) to SONO Seaport on the left. The bench marks are located along North
and South Water Street, North Main Street, Elizabeth Street, and Monroe Street.
The tide gauge was located on the bulkhead at the SONO Seaport Restaurant.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 8448 A 2002
DESIGNATION: 846 8448 A
MONUMENTATION: Tidal Station disk VM#: 16739
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Access ramp OPUS PID:
LATITUDE: 41° 5.8' N ( 41.09670) LONGITUDE: 73° 24.9' W ( -73.41500)
The primary bench mark is a disk set in the concrete access ramp at Exposures
Catalog Outlet, 87 South Water Street, 7.50 m (24.6 ft) west of the centerline
of South Water Street, 4.17 m (13.7 ft) NW of the entrance to the shop, 0.30 m
(1.0 ft) SW of the corner of the ramp, and 0.63 m (2.1 ft) above the sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8448 B 2002
DESIGNATION: 846 8848 B
MONUMENTATION: Tidal Station disk VM#: 16740
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Loading ramp OPUS PID:
LATITUDE: 41° 6.0' N ( 41.10000) LONGITUDE: 73° 25.0' W ( -73.41670)
The bench mark is a disk set in the SE corner of the loading dock at the
Maritime Aquarium, directly under the south side of the overhead bridge for the
Amtrak Railroad, 16.82 m (55.2 ft) south of the NE inside corner of the loading
dock, 15.46 m (50.7 ft) east of the centerline of North Water Street, 1.81 m
(5.9 ft) west of the north corner of a loading bay door, and 0.45 m (1.5 ft)
above the pavement.
BENCH MARK STAMPING: 8448 C 2002
DESIGNATION: 846 8448 C
MONUMENTATION: Tidal Station disk VM#: 16741
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Retaining wall OPUS PID:
LATITUDE: 41° 5.8' N ( 41.09670) LONGITUDE: 73° 25.1' W ( -73.41830)
The bench mark is a disk set in the north end of the easternmost of two
retaining walls at the loading dock of Clark Company, 64 South Main Street, 20 m
(66 ft) south of the centerline of Elizabeth Street, 6.10 m (20.0 ft) NNW of the
back NE corner of the loading bay, 0.13 m (0.4 ft) south of the north end of the
retaining wall, and 0.84 m (2.8 ft) above the pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: W 1 ELEV 22.057 FT 1922
DESIGNATION: W 1
MONUMENTATION: Bench Mark disk VM#: 16742
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0787
SETTING CLASSIFICATION: Building OPUS PID:
LATITUDE: 41° 6.0' N ( 41.10000) LONGITUDE: 73° 25.1' W ( -73.41830)
The bench mark is a disk set vertically in the west face of the Norwalk Museum,
27 m (89 ft) south of the south curb of Marshall Street, 11.43 m (37.5 ft) east
of the east curb of North Main Street, 0.12 m (0.4 ft) north of the SW corner of
the building, and 0.21 m (0.7 ft) above the level of the sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: C 15 1935
DESIGNATION: C 15
MONUMENTATION: Bench Mark disk VM#: 16743
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0788
SETTING CLASSIFICATION: Bridge OPUS PID:
LATITUDE: 41° 5.8' N ( 41.09670) LONGITUDE: 73° 25.2' W ( -73.42000)
The bench mark is a disk set in the SE wing wall on the SW end of the Amtrak
Railroad bridge over Monroe Street, 61 m (200 ft) NE of the South Norwalk Train
Station, 32 m (105 ft) NE of power line tower No. 521, 5.58 m (18.3 ft) SW of
the NE end of the retaining wall, 2.13 m (7.0 ft) SE of the SE rail of a spur
track leading SW to the station, 0.70 m (2.3 ft) west of a metal I-beam post
supporting overhead railroad electric lines, and 0.18 m (0.6 ft) below the
tracks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
T I D A L D A T U M S
Tidal datums at SOUTH NORWALK, NORWALK RIVER based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: July 2002 - September 2002
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8467150 BRIDGEPORT, BRIDGEPORT HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.337
MEAN HIGH WATER MHW = 2.233
North American Vertical Datum NAVD88 = 1.213
MEAN SEA LEVEL MSL = 1.163
MEAN TIDE LEVEL MTL = 1.156
MEAN LOW WATER MLW = 0.079
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
8448 A 2002 3.758 1.525
8448 B 2002 3.141 0.908
8448 C 2002 7.423 5.190
W 1 ELEV 22.057 FT 1922 7.602 5.369
C 15 1935 11.795 9.562
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8468448 PUBLICATION DATE: 05/15/2003
Name: SOUTH NORWALK, NORWALK RIVER
CT
NOAA Chart: 12368 Latitude: 41° 5.8' N ( 41.09670)
USGS Quad: SOUTH NORWALK Longitude: 73° 24.9' W ( -73.41500)
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.