U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 1 of 4
Station ID: 9414551 PUBLICATION DATE: 09/15/2004
Name: GOLD STREET BRIDGE, ALVISO SLOUGH
CALIFORNIA
NOAA Chart: 18652 Latitude: 37° 25.4' N
USGS Quad: MILPITAS Longitude: 121° 58.5' W
To reach the tidal bench marks proceed south of Alviso along Gold Street then
east of railroad tracks to the Gold Street Bridge over Alviso Slough. The bench
marks are between Gold Street and the railroad tracks parallel and west of Gold
Street, and the tide gage and staff were located on the west side of the bridge,
near the midpoint of the bridge.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: TIDAL BM 8 1974
DESIGNATION: 941 4551 TIDAL BM 8
MONUMENTATION: Tidal Station disk VM#: 8346
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete flood gate
The bench mark is a disk set flush in top of a concrete level flood gate, 39.62
m (130.0 ft) west of power transmission tower NEWARK-SCOTT 7146 CIR 2, 30.48 m
(100.0 ft) east of the railroad bridge across Alviso Slough south of Alviso,
7.62 m (25.0 ft) south of the centerline of the road atop the south levee west
of Gold Street bridge, 0.15 m (0.5 ft) north of the south face of the concrete
structure, 0.09 m (0.3 ft) east of the west face, and 2.44 m (8.0 ft) above the
top of the west wingwall of the floodgate.
BENCH MARK STAMPING: TIDAL BM 7 1974
DESIGNATION: 941 4551 TIDAL BM 7
MONUMENTATION: Tidal Station disk VM#: 8345
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete foundation
The primary bench mark is a disk set flush in top of the westernmost one of four
concrete foundations of the Pacific Gas and Electric company's power
transmission tower designated NEWARK-SCOTT 7146 CIR 2, 32 m (105 ft) west of the
centerline of Gold Street, 27.43 m (90.0 ft) south of the centerline of road
atop the south levee, west of Gold Street bridge, 0.61 m (2.0 ft) above the
ground, and 0.3 m (1 ft) below the lowest set of horizonial angle iron tower
braces.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 9414551 PUBLICATION DATE: 09/15/2004
Name: GOLD STREET BRIDGE, ALVISO SLOUGH
CALIFORNIA
NOAA Chart: 18652 Latitude: 37° 25.4' N
USGS Quad: MILPITAS Longitude: 121° 58.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: TIDAL BM 9 1974
DESIGNATION: 941 4551 TIDAL BM 9
MONUMENTATION: Tidal Station disk VM#: 8347
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Wing wall
The bench mark is a disk set flush in the east wingwall at the south end of the
southern Pacific railroad bridge over Alviso Slough south of Alviso, 2.50 m (8.2
ft) east of the east rail, 1.40 m (4.6 ft) ESE of the SW corner of the south end
of the southeasternmost concrete bridge girder, and 1.22 m (4.0 ft) above ground
level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 9414551 PUBLICATION DATE: 09/15/2004
Name: GOLD STREET BRIDGE, ALVISO SLOUGH
CALIFORNIA
NOAA Chart: 18652 Latitude: 37° 25.4' N
USGS Quad: MILPITAS Longitude: 121° 58.5' W
T I D A L D A T U M S
Tidal datums at GOLD STREET BRIDGE, ALVISO SLOUGH based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: January 1976 - March 1976
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9414750 ALAMEDA, SAN FRANCISCO BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER (MHHW) = 2.829
MEAN HIGH WATER (MHW) = 2.655
MEAN SEA LEVEL (MSL) = 1.517
MEAN TIDE LEVEL (MTL) = 1.493
MEAN LOW WATER (MLW) = 0.332
MEAN LOWER LOW WATER (MLLW) = 0.000
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
TIDAL BM 8 1974 5.165 2.510
TIDAL BM 7 1974 4.664 2.009
TIDAL BM 9 1974 6.859 4.204
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 9414551 PUBLICATION DATE: 09/15/2004
Name: GOLD STREET BRIDGE, ALVISO SLOUGH
CALIFORNIA
NOAA Chart: 18652 Latitude: 37° 25.4' N
USGS Quad: MILPITAS Longitude: 121° 58.5' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.