Superseded Bench Mark Sheet for 9418686, HOOKTON SLOUGH,HUMBOLDT BAY CA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:  05/03/1982
Station ID: 9418686                                SUPERCEDED DATE:   04/21/2003
Name:       HOOKTON SLOUGH, HUMBOLDT BAY                      
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 41.2' N
USGS Quad:  FIELDS LANDING                         Longitude:       124° 13.3' W


To reach the tidal bench marks from US Highway 101 take Loleta-Hookton Exit
(about 10 miles south of Eureka), along Salmon Creek Ranch access road north (on
west side of US Highway 101) until it curves sharply left, continue straight
through two ranch gates, left at third gate, right turn after 150 feet, follow
levee southwest until too narrow to be driven on, and then walk on north side of
small slough until you reach another slough (Hookton Slough).  The gage is
located 100 yards west southwest of the point where you reach Hookton Slough. 
The tide gage and staff were located on a free standing pile in the slough.


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


                 PRIMARY BENCH MARK STAMPING:  K1087 1967

MONUMENTATION:           Survey Disk                               VM#:     8708
AGENCY:                                                            PID#:  LV0255
SETTING CLASSIFICATION:  Concrete Headwall of Culvert


The bench mark is set in top of south end of west concrete headwall of culvert
68.80, 7.15 miles north along US Highway 101 from Fortuna overpass at Fortuna,
0.6 mile north of Hookton Road overpass, 30 feet west of centerline of west
lanes of highway, and 2.5 feet below the highway.



                         BENCH MARK STAMPING:  8686 A 1977

MONUMENTATION:           Survey Disk                               VM#:     8705
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper Coated Rod


The bench mark is inside a PVC pipe 0.25 foot below grade (at base of drainage
canal levee), 500 feet southeast of center of the slough, 40 feet southeast of
junction of southeast levee of slough and north drainage canal, 10 feet
northeast of redwood witness post, and 3.5 feet above grade (at top of north
levee drainage canal).

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

                                                   PUBLICATION DATE:  05/03/1982
Station ID: 9418686                                SUPERCEDED DATE:   04/21/2003
Name:       HOOKTON SLOUGH, HUMBOLDT BAY                      
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 41.2' N
USGS Quad:  FIELDS LANDING                         Longitude:       124° 13.3' W


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


                         BENCH MARK STAMPING:  8686 C 1977

MONUMENTATION:           Survey Disk                               VM#:     8706
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-Clad Rod


The bench mark is inside a PVC pipe 0.25 foot below grade, 0.45 mile northwest
of Bench Mark K 1078 1967, 150 feet west of south bound lanes of US Highway 101,
32 feet northeast of center of McBride Ranch road at turn in road and 3 feet
southwest of telephone pole on west side of highway.



                         BENCH MARK STAMPING:  8686 D 1977

MONUMENTATION:           Survey Disk                               VM#:     8707
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-Clad Rod


The bench mark is inside a PVC pipe 0.5 foot below grade, 0.15 mile west of US
Highway 101 at the McBride Ranch equipment yard, 12 feet south of center of
Ranch road, and 2 feet west of northwest corner of concrete building (dated 1923
above door).



                         BENCH MARK STAMPING:  UNSTAMPED

MONUMENTATION:           Survey Disk                               VM#:     8709
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Unspecified


The bench mark is located at the gate to west stock yard, west of gate at end of
McBride Ranch Road, 0.4 mile west southwest of west side of drainage ditch, 27
feet east of concrete water trough, 15 feet southwest of gate past the west side
of drainage ditch, 0.25 foot north of steel witness post, and 0.5 foot above
grade.

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

                                                   PUBLICATION DATE:  05/03/1982
Station ID: 9418686                                SUPERCEDED DATE:   04/21/2003
Name:       HOOKTON SLOUGH, HUMBOLDT BAY                      
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 41.2' N
USGS Quad:  FIELDS LANDING                         Longitude:       124° 13.3' W


                            T I D A L   D A T U M S 


Tidal datums at HOOKTON SLOUGH, HUMBOLDT BAY based on:

     LENGTH OF SERIES:      12 MONTHS
     TIME PERIOD:           OCTOBER 1977 - SEPTEMBER 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9419750 CRESCENT CITY, CA


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

     MEAN HIGHER HIGH WATER                     MHHW   =   6.94
     MEAN HIGH WATER                            MHW    =   6.24
     MEAN TIDE LEVEL                            MTL    =   3.73
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   3.71
     MEAN LOW WATER                             MLW    =   1.22
     MEAN LOWER LOW WATER                       MLLW   =   0.00

   * NGVD reference based on adjustment of 1968 and NOS leveling of1978 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     K1087 1967                                  6.25      0.01
     8686 A 1977                                 3.34     -2.90
     8686 C 1977                                 6.37      0.13
     8686 D 1977                                 5.52     -0.72
     UNSTAMPED                                   3.90     -2.34


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

                                                   PUBLICATION DATE:  05/03/1982
Station ID: 9418686                                SUPERCEDED DATE:   04/21/2003
Name:       HOOKTON SLOUGH, HUMBOLDT BAY                      
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 41.2' N
USGS Quad:  FIELDS LANDING                         Longitude:       124° 13.3' 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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