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Bench Mark Sheet for 9415438, SKAGGS ISLAND, HUDEMAN SLOUGH CA

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


To reach the tidal bench marks from the intersection of Imola Avenue with State
Highway 121/12 in Napa, proceed south on State Highway 121/12 for 6.4 km (4.0
mi) to Duhig Road, then south on Duhig Road for 4.3 km (2.7 mi) to Ramal Road,
then west on Ramal Road for 1.8 km (1.1 mi) to Skaggs Island Road, then south on
Skaggs Island Road for 2.3 km (1.4 mi) to the Skaggs Island Road bridge over
Hudeman Slough.  The bench marks are located along the NW side of Skaggs Island
Road on the north side of the slough.  The tide gauge and staff were on the west
side of the wooden bridge spanning Hudeman Slough.


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


                 PRIMARY BENCH MARK STAMPING:  BM A
                         DESIGNATION:          941 5438 A

MONUMENTATION:           Bolt                                  VM#:        11807
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete jacket                       OPUS PID:        
LATITUDE:   38° 12.3' N (  38.20500)          LONGITUDE: 122° 22.4' W (-122.37300)


The primary bench mark is a bolt set on the outer edge of the concrete jacket
enclosing one of the wooden support piles on the NW side of the Skaggs Island
Road bridge, 35.81 m (117.5 ft) south of the north end of the bridge, and about
2 m (5 ft) below road level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


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


                         BENCH MARK STAMPING:  5438 C 1986
                         DESIGNATION:          941 5438 C

MONUMENTATION:           Tidal Station disk                    VM#:        11804
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID#: BBCY02
LATITUDE:   38° 12.3' N (  38.20500)          LONGITUDE: 122° 22.4' W (-122.37300)


The bench mark is a disk set on the NW side of Skaggs Island Road, 1.4 km (0.9
mi) south of the railroad tracks across Skaggs Island Road, 0.2 km (0.1 mi)
north of the north end of the Skaggs Island bridge, 9 m (30 ft) NW of a 10 MPH
traffic sign, 8 m (27 ft) east of a barbed wire fence, 6 m (21 ft) east of a gas
pipeline, and near a pink fiberglass witness post.  The bench mark is crimped to
the top of a stainless steel rod driven 11.9 m (39 ft) to refusal, and encased
in a 4-inch PVC pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


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


                         BENCH MARK STAMPING:  5438 D 1986
                         DESIGNATION:          941 5438 D

MONUMENTATION:           Tidal Station disk                    VM#:        11805
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID#: BBCN76
LATITUDE:   38° 12.3' N (  38.20500)          LONGITUDE: 122° 22.4' W (-122.37300)


The bench mark is a disk set on the NW side of Skaggs Island Road, 1.37 km (0.85
mi) south of the railrod tracks across Skaggs Island Road, 0.26 km (0.16 mi)
north of the north end of the Skaggs Island bridge, 10 m (32 ft) NE of a bend in
a gas pipeline, 8 m (27 ft) west of the centerline of Skaggs Island Road, 8.1 m
(26.5 ft) east of a barbed wire fence, 7 m (22 ft) NE of the straight section of
the pipeline, 4 m (12 ft) west of a short guard rail in front of a bend in the
pipeline, and near a pink fiberglass witness post.  The bench mark is crimped to
the top of a stainless steel rod driven 10.4 m (34 ft) to refusal, and encased
in a 4-inch PVC pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


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


                         BENCH MARK STAMPING:  5438 E 1986
                         DESIGNATION:          941 5438 E

MONUMENTATION:           Tidal Station disk                    VM#:        11806
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   38° 12.3' N (  38.20500)          LONGITUDE: 122° 22.4' W (-122.37300)


The bench mark is a disk set on the NW side of Skaggs Island Road, 1.3 km (0.8
mi) south of the railroad tracks across Skaggs Island Road, 0.3 km (0.2 mi)
north of the north end of the Skaggs Island bridge, 8 m (26 ft) west of the
centerline of Skaggs Island Road, 8 m (26 ft) east of a barbed wire fence, 7 m
(23 ft) east of a gas pipeline, and near a pink fiberglass witness post.  The
bench mark is crimped to the top of a stainless steel rod driven 13.1 m (43 ft)
to refusal, and encased in a 4-inch PVC pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


                            T I D A L   D A T U M S 


Tidal datums at SKAGGS ISLAND, HUDEMAN SLOUGH based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           January 1986 - February 1986
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9414290 SAN FRANCISCO, SAN FRANCISCO BAY


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

     MEAN HIGHER HIGH WATER                     MHHW   =  1.835
     MEAN HIGH WATER                            MHW    =  1.669
     MEAN SEA LEVEL                             MSL    =  0.965
     MEAN TIDE LEVEL                            MTL    =  0.958
     MEAN LOW WATER                             MLW    =  0.247
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     BM A                                        2.788    1.119
     5438 C 1986                                -0.008   -1.677
     5438 D 1986                                 0.170   -1.499
     5438 E 1986                                -0.118   -1.787


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 9415438                         PUBLICATION DATE:  01/07/2005
Name:       SKAGGS ISLAND, HUDEMAN SLOUGH                     
            CA
NOAA Chart: 18654                           Latitude:   38° 12.3' N (  38.20500)
USGS Quad:  CUTTINGS WHARF                  Longitude: 122° 22.4' W (-122.37300)


                             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.

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Products available at 9415438 SKAGGS ISLAND, HUDEMAN SLOUGH, CA

Revised: 10/15/2013
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services