Superseded Bench Mark Sheet for 9418799, FRESHWATER SLOUGH, HUMBOLDT BAY CA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  05/06/1982
Station ID: 9418799                                SUPERCEDED DATE:   04/21/2003
Name:       FRESHWATER SLOUGH, HUMBOLDT BAY                   
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  EUREKA                                 Longitude:       124°  7.1' W


To reach the tidal bench marks proceed east along US Highway 101 from Eureka to
Myrtle Avenue exit, 1.25 miles southeast along Myrtle Avenue, left on Park
Street, east along Part Street until it dead ends.  The tide gage and staff were
on the wooden bridge over the slough.


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


                 PRIMARY BENCH MARK STAMPING:  8799 A 1978

MONUMENTATION:           Survey Disk                               VM#:     8728
AGENCY:                                                            PID#:  LV0643
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is set on a galvanized steel rod driven to 56 feet, encased in
concrete and PVC pipe (extends 0.5 foot above grade), 203 feet southwest of
southwest corner of a wooden bridge, 13 feet north of centerline of Park Street,
and 2 feet southwest of corner of wooden fence.



                         BENCH MARK STAMPING:  8799 B 1978

MONUMENTATION:           Survey Disk                               VM#:     8729
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is set on a galvanized steel rod driven to 45 feet, encased in
concrete and PVC pipe (extends 0.7 foot above grade), 375 feet west of east end
of Park Street, 31 feet south southwest of southwest corner of large garage, 8
feet south of centerline of Park Street, and 3 feet east of a witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  05/06/1982
Station ID: 9418799                                SUPERCEDED DATE:   04/21/2003
Name:       FRESHWATER SLOUGH, HUMBOLDT BAY                   
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  EUREKA                                 Longitude:       124°  7.1' W


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


                         BENCH MARK STAMPING:  8799 C 1978

MONUMENTATION:           Survey Disk                               VM#:     8730
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is set on a galvanized steel rod driven to 31 feet, encased in
concrete and PVC pipe (extends 0.4 foot above grade), 650 feet east along Park
Street from center of intersection of Park and Quakes Streets, 36 feet east of
centerline of dirt driveway, 12.5 feet south southwest of centerline of Park
Street, and 2 feet east southeast of witness post.



                         BENCH MARK STAMPING:  8799 E 1978

MONUMENTATION:           Survey Disk                               VM#:     8731
AGENCY:                                                            PID#:  LV0642
SETTING CLASSIFICATION:  Pavement


The bench mark is set flush in the northeast corner of sidewalk at the southwest
corner of the T intersection of Park and Quaker Streets, 37 feet southwest of
center of intersection, and 11 feet east of the fire hydrant.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  05/06/1982
Station ID: 9418799                                SUPERCEDED DATE:   04/21/2003
Name:       FRESHWATER SLOUGH, HUMBOLDT BAY                   
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  EUREKA                                 Longitude:       124°  7.1' W


                            T I D A L   D A T U M S 


Tidal datums at FRESHWATER SLOUGH, HUMBOLDT BAY based on:

     LENGTH OF SERIES:      8 MONTHS
     TIME PERIOD:           MAY - DECEMBER 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:   


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

     MEAN HIGHER HIGH WATER                     MHHW   =   7.20
     MEAN HIGH WATER                            MHW    =   6.49
     MEAN TIDE LEVEL                            MTL    =   3.78
     MEAN LOW WATER                             MLW    =   1.08
     MEAN LOWER LOW WATER                       MLLW   =   0.00

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     8799 A 1978                                 9.58      3.24
     8799 B 1978                                 7.80      1.31
     8799 C 1978                                17.62     11.13
     8799 E 1978                                67.73     61.24


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

                                                   PUBLICATION DATE:  05/06/1982
Station ID: 9418799                                SUPERCEDED DATE:   04/21/2003
Name:       FRESHWATER SLOUGH, HUMBOLDT BAY                   
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  EUREKA                                 Longitude:       124°  7.1' 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.

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