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Bench Mark Sheet for 9413631, Elkhorn Slough at Elkhorn 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Superseded Epoch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Small blue map location marker Unpublished bench mark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  5

                                                                                
Station ID: 9413631                         PUBLICATION DATE:  07/07/2009
Name:       ELKHORN SLOUGH AT ELKHORN                         
            CA
NOAA Chart: 18680                           Latitude:   36° 49.1' N (  36.81830)
USGS Quad:  PRUNEDALE                       Longitude: 121° 44.8' W (-121.74700)


To reach the tidal bench marks proceed through the Elkhorn Ranch in Elkhorn to
the Old Elkhorn depot and then 0.8 km (0.5 mi) south along the access road to
the bridge over the subsidary slough (off Elkhorn Slough).  The bench marks are
on both sides of the slough.  The tide gage and staff were located on a free
standing single pile structure in the slough. 


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


                 PRIMARY BENCH MARK STAMPING:  3631 A 1976
                         DESIGNATION:          941 3631 A TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8076
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  GU3204
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   36° 48.8' N (  36.81330)          LONGITUDE: 121° 44.7' W (-121.74500)


The bench mark is a disk located in Elkhorn Slough at Yampa Marsh north of All
American and Import Auto Wreckers, 131 m (430 ft) south of bench mark 941 3631
B, 44 m (145 ft) north of the NW corner of bridge, and 4.72 m (15.5 ft) west of
west rail.  The bench mark is crimped to the top of a copper-clad steel rod
driven an unspecified depth and encased in a PVC pipe.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 9413631                         PUBLICATION DATE:  07/07/2009
Name:       ELKHORN SLOUGH AT ELKHORN                         
            CA
NOAA Chart: 18680                           Latitude:   36° 49.1' N (  36.81830)
USGS Quad:  PRUNEDALE                       Longitude: 121° 44.8' W (-121.74700)


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


                         BENCH MARK STAMPING:  3631 B 1976
                         DESIGNATION:          941 3631 B TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8077
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  GU3203
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   36° 48.9' N (  36.81500)          LONGITUDE: 121° 44.7' W (-121.74500)


The bench mark is a disk located in Elkhorn Slough at Yampa Marsh north of All
American and Import Auto Wreckers, 131 m (430 ft) north of bench mark 941 3631
A, 6 m (21 ft) east of the east rail, 1 m (4 ft) NNW of a witness post, 1 m (6
ft) above grade, and level with the ground.  The bench mark is crimped to the
top of a copper-clad steel rod driven 21.3 m (70 ft) to refusal and encased in a
PVC pipe.



                         BENCH MARK STAMPING:  3631 H 2007
                         DESIGNATION:          941 3631 H

MONUMENTATION:           Flange-encased Rod                    VM#:        18336
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID#: BBCR98
LATITUDE:   36° 48.5' N (  36.80830)          LONGITUDE: 121° 44.8' W (-121.74700)


The bench mark is located in Elkhorn Slough at Yampa Marsh north of All American
and Import Auto Wreckers, 90 m (295 ft) west of railroad tracks, 10 m (33.3 ft)
north of barbed wire fence, and 0.1 m (0.33 ft) west of orange witness post. The
datum offset is set  0.1 m (0.33 ft) below ground, being the top of a stainless
steel rod driven to a depth of 12.2 m (40 ft), and encased in 5 inch PVC with
aluminum access cover.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 9413631                         PUBLICATION DATE:  07/07/2009
Name:       ELKHORN SLOUGH AT ELKHORN                         
            CA
NOAA Chart: 18680                           Latitude:   36° 49.1' N (  36.81830)
USGS Quad:  PRUNEDALE                       Longitude: 121° 44.8' W (-121.74700)


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


                         BENCH MARK STAMPING:  3631 J 2007
                         DESIGNATION:          941 3631 J

MONUMENTATION:           Flange-encased Rod                    VM#:        18337
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   36° 48.6' N (  36.81000)          LONGITUDE: 121° 44.9' W (-121.74800)


The bench mark is stainless steel rod located in Elkhorn Slough at Yampa Marsh
north of All American and Import Auto Wreckers, 1.3 m (4.3 ft) south of marsh
pickle grass, and 0.1 m (0.3 ft) north of orange NOS witness post.  The datum
point is set 0.1 m (0.3 ft) below ground, being the top of a stainless steel rod
driven to a depth of 13.4 m (44.0 ft), and encased in 5 inch PVC with aluminum
access cover.



                         BENCH MARK STAMPING:  3631 K 2007
                         DESIGNATION:          941 3631 K

MONUMENTATION:           Flange-encased Rod                    VM#:        18338
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   36° 48.6' N (  36.81000)          LONGITUDE: 121° 45.0' W (-121.75000)


The bench mark is located in Elkhorn Slough at Yampa Marsh north of All American
and Import Auto Wreckers, 28.8 m (94.5 ft) north of marsh pickle grass, and 0.2
m (0.6 ft) south of orange NOS witness post. The datum point is set 0.1 m (0.3
ft) below ground, being the top of a stainless steel rod driven to a depth of
13.4 m (44.0 ft), and encased in 5 inch PVC with aluminum access cover.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 9413631                         PUBLICATION DATE:  07/07/2009
Name:       ELKHORN SLOUGH AT ELKHORN                         
            CA
NOAA Chart: 18680                           Latitude:   36° 49.1' N (  36.81830)
USGS Quad:  PRUNEDALE                       Longitude: 121° 44.8' W (-121.74700)


                            T I D A L   D A T U M S 


Tidal datums at ELKHORN SLOUGH AT ELKHORN based on:

     LENGTH OF SERIES:      4 MONTHS
     TIME PERIOD:           June 2007 - September 2007
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9413450 MONTEREY, MONTEREY HARBOR


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

     MEAN HIGHER HIGH WATER                     MHHW   =  1.636
     MEAN HIGH WATER                            MHW    =  1.420
     MEAN TIDE LEVEL                            MTL    =  0.867
     MEAN SEA LEVEL                             MSL    =  0.865
     MEAN LOW WATER                             MLW    =  0.313
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     3631 A 1976                                 1.744    0.324
     3631 B 1976                                 1.774    0.354
     3631 H 2007                                 1.399   -0.021
     3631 J 2007                                 2.231    0.811
     3631 K 2007                                 1.292   -0.128


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

                                                                                
Station ID: 9413631                         PUBLICATION DATE:  07/07/2009
Name:       ELKHORN SLOUGH AT ELKHORN                         
            CA
NOAA Chart: 18680                           Latitude:   36° 49.1' N (  36.81830)
USGS Quad:  PRUNEDALE                       Longitude: 121° 44.8' W (-121.74700)


                             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 9413631 Elkhorn Slough at Elkhorn, CA

Revised: 08/08/2018
NOAA / National Ocean Service
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