U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 09/07/1983
Station ID: 9414519 SUPERCEDED DATE: 04/21/2003
Name: MOWRY SLOUGH, SAN FRANCISCO BAY
CALIFORNIA
NOAA Chart: 18651 Latitude: 37° 29.6' N
USGS Quad: MOUNTAINVIEW Longitude: 122° 2.5' W
To reach the tidal bench marks from State Highway 17 exit at Thornton Avenue
West, go SW for two blocks to Cedar Boulevard, left turn and go two blocks on
Cedar Boulevard and then turn right onto Central, continue on Central with left
turn into the main gate of Leslie Salt Co., straight ahead 0.11 mile (0.18 km)
and turn right just after the chainlink fence, continue 0.40 mile (0.64 km) to a
T-junction and turn left, 0.11 mile (0.18 km) and turn right at a Y-junction,
0.40 mile (0.64 km) and turn right at a T-junction, 0.65 mile (1.05 km) and turn
right at a Y-junction after a wooden building, 30 feet (9.1 m) left at a
Y-junction and then 1.05 miles (1.69 km) to a T-junction. The tide gage and
staff were located on a freestanding piling in the slough, and the bench marks
are along the Salt Levee Road.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 4519 A 1976
MONUMENTATION: Survey Disk VM#: 8314
AGENCY: PID#: HT2392
SETTING CLASSIFICATION: Rod Mark
The bench mark is 440 feet (134 m) WSW of Bench Mark 4519 B 1976, 350 feet
(106.7 m) north of the north bank of the slough, 13 feet (4 m) SSE of the
centerline of Leslie Salt Company levee road parallel to the slough and 2.5 feet
(3.8 m) east of a witness post. The bench mark is on a rod driven to 48.0 feet
(14.6 m), protected by a PVC pipe that extends 0.5 foot (0.1 m) above the grade.
BENCH MARK STAMPING: 4519 B 1976
MONUMENTATION: Survey Disk VM#: 8315
AGENCY: PID#: HT2394
SETTING CLASSIFICATION: Rod Mark
The bench mark is 500 feet (152 m) north of north bank of the slough, 445 feet
(155 m) west of Bench Mark 4519 C 1976, 440 feet (134 m) ENE of Bench Mark 4519
A 1976, 68 feet (20.7 m) SSE of Bench Mark STA 16 1975 L8 3936, 22 feet (6.7 m)
south of the centerline of the levee road, 2.5 feet (0.8 m) ESE of a witness
post, and on south side of Leslie Salt Company levee road parallel to the
slough. The bench mark is on a rod driven to 56 feet (17.1 m), protected by a
PVC pipe that extends 0.6 foot (0.2 m) above grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 09/07/1983
Station ID: 9414519 SUPERCEDED DATE: 04/21/2003
Name: MOWRY SLOUGH, SAN FRANCISCO BAY
CALIFORNIA
NOAA Chart: 18651 Latitude: 37° 29.6' N
USGS Quad: MOUNTAINVIEW Longitude: 122° 2.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4519 C 1976
MONUMENTATION: Survey Disk VM#: 8316
AGENCY: PID#: HT2395
SETTING CLASSIFICATION: Rod Mark
The bench mark is 500 feet (152 m) north of north bank of the slough, 500 feet
(152 m) NNW of beached house boat on the north bank of the slough, 450 feet (137
m) WNW of Bench Mark 4519 D 1976, 16 feet (4.9 m) south of the centerline of
Leslie Salt Company levee road parallel to the slough, 2 feet (0.6 m) WNW of a
witness post, and 3 feet (1 m) below road level. The rod was driven to 64 feet
(19.5 m) protected by a PVC pipe that extends 0.4 foot (0.1 m) above the grade.
BENCH MARK STAMPING: 4519 D 1976
MONUMENTATION: Survey Disk VM#: 8317
AGENCY: PID#: HT2396
SETTING CLASSIFICATION: Rod Mark
The bench mark is 459 feet (140 m) westof Bench Mark 4519 E 1976, 450 feet (137
m) ESE of Bench Mark 4519 C 1976, 450 feet (137 m) north of north bank of the
slough, 17 feet (5.2 m) south of the centerline of Leslie Salt Company levee
road parallel to the slough, 3 feet (0.9 m) NW of a witness post, and 3 feet
(0.9 m) below the road level. The rod is driven to 65 feet (19.8 m) protected
by a PVC pipe that extends 0.5 foot (0.2 m) above the grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 09/07/1983
Station ID: 9414519 SUPERCEDED DATE: 04/21/2003
Name: MOWRY SLOUGH, SAN FRANCISCO BAY
CALIFORNIA
NOAA Chart: 18651 Latitude: 37° 29.6' N
USGS Quad: MOUNTAINVIEW Longitude: 122° 2.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4519 E 1976
MONUMENTATION: Survey Disk VM#: 8318
AGENCY: PID#: HT2397
SETTING CLASSIFICATION: Rod Mark
The bench mark is 0.68 miles (1.09 km) west of the junction of the road leading
to the duck club, 550 feet (167.6 m) north of the north bank of the slough, 459
feet (140 m) east of Bench Mark 4519 D 1976, 8 feet (2.4 m) SSE of the
centerline of Leslie Salt Company levee and parallel to the slough, and 5.0 feet
(1.5 m) north of a witness post. The bench mark on a rod driven to 50 feet
(15.2 m) and protected by a PVC pipe.
BENCH MARK STAMPING: STA 16 1975 L8 3936
MONUMENTATION: Survey Disk VM#: 8319
AGENCY: PID:
SETTING CLASSIFICATION: Unspecified
The bench mark is located on the north side of the Leslie Salt Company levee
road parallel to the slough, 568 feet (173 m) north of the north bank of the
slough, 68 feet (20.7 m) NNW of Bench Mark 4519 B 1976, and 46 feet (14.0 m)
north of the centerline of the levee road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 09/07/1983
Station ID: 9414519 SUPERCEDED DATE: 04/21/2003
Name: MOWRY SLOUGH, SAN FRANCISCO BAY
CALIFORNIA
NOAA Chart: 18651 Latitude: 37° 29.6' N
USGS Quad: MOUNTAINVIEW Longitude: 122° 2.5' W
T I D A L D A T U M S
Tidal datums at MOWRY SLOUGH, SAN FRANCISCO BAY based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: DECEMBER 1976-JUNE 1977
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9414509 DUMBARTON BRIDGE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (06/30/1977) = 10.23
MEAN HIGHER HIGH WATER MHHW = 8.53
MEAN HIGH WATER MHW = 7.94
MEAN TIDE LEVEL MTL = 4.55
MEAN LOW WATER MLW = 1.15
MEAN LOWER LOW WATER MLLW = 0.00
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
4519 A 1976 10.71 2.76
4519 B 1976 10.78 2.83
4519 C 1976 10.46 2.52
4519 D 1976 11.08 3.13
4519 E 1976 11.69 3.74
STA 16 1975 L8 3936 12.75 4.80
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 09/07/1983
Station ID: 9414519 SUPERCEDED DATE: 04/21/2003
Name: MOWRY SLOUGH, SAN FRANCISCO BAY
CALIFORNIA
NOAA Chart: 18651 Latitude: 37° 29.6' N
USGS Quad: MOUNTAINVIEW Longitude: 122° 2.5' 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 (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.