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Superseded Bench Mark Sheet for 9418983, UPPER MAD RIVER SLOUGH CA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  09/27/1983
Station ID: 9418983                                SUPERCEDED DATE:   04/21/2003
Name:       UPPER MAD RIVER SLOUGH, HUMBOLDT BAY              
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  ARCATA SOUTH                           Longitude:       124°  7.1' W


To reach the tidal bench marks from U.S. Highway 101 exit at Arcata/Samona
Boulevard west, right on K Street which turns into Alliance Road, continue 1
mile (1.6 km) on Alliance Road until it ends at a T-intersection, left turn and
continue 0.5 mile (0.8 km) to Lanphere Road then left on Lanphere Road for 1.5
miles (2.4 km).  The bench marks are along Lanphere Road east of the ranch
buildings.  The tide gage and staff were located on the south side of and at the
midpoint of the bridge over the slough.


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


                 PRIMARY BENCH MARK STAMPING:  8983 A 1978

MONUMENTATION:           Survey Disk                               VM#:     8749
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 30.0 feet (9.1 m) east of the east end of the Lanphere Road
bridge over the slough, 8.0 feet (2.4 m) south of the centerline of Lanphere
Road, 4.0 feet (1.2 m) east of a witness post/telephone pole and 0.1 foot (0.03
m) below grade.  The bench mark is on a rod driven to 32.0 feet (9.8 m) and
encased in concrete.



                         BENCH MARK STAMPING:  8983 B 1978

MONUMENTATION:           Survey Disk                               VM#:     8750
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 370.0 feet (112.8 m) east of the east end of Lanphere Road
bridge over the slough, 92.0 feet (28.0 m) west of the second telephone pole
east of the east end of the bridge, 11.5 feet (3.5 m) south of the centerline of
Lanphere Road, 2.0 feet (0.6 m) north of a witness post, and 0.4 foot (0.1 m)
below grade.  The bench mark is on a rod driven to 32.0 feet (9.8 m) and encased
in concrete.

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

                                                   PUBLICATION DATE:  09/27/1983
Station ID: 9418983                                SUPERCEDED DATE:   04/21/2003
Name:       UPPER MAD RIVER SLOUGH, HUMBOLDT BAY              
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  ARCATA SOUTH                           Longitude:       124°  7.1' W


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


                         BENCH MARK STAMPING:  8983 C 1978

MONUMENTATION:           Survey Disk                               VM#:     8751
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 528.0 feet (160.9 m) east of the east end of Lanphere Road
bridge over the slough, 175.0 feet (53.3 m) WSW of the intersection of the level
dirt road and Lanphere Road, 25.0 feet (7.6 m) SW of a sign ONE LANE BRIDGE,
10.0 feet (3.0 m) south of the centerline of Lanphere Road, 4.0 feet (1.2 m)
north of a witness post, and 0.1 foot (0.03 m) below grade.



                         BENCH MARK STAMPING:  8983 D 1978

MONUMENTATION:           Survey Disk                               VM#:     8752
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 0.17 mile (0.27 km) east of the east end of the Lanphere Road
bridge over the slough, 51.0 feet (15.5 m) SE of the center of the intersection
of the levee dirt road and Lanphere Road, 19.0 feet (5.8 m) south of the center
of Lanphere Road, 2.5 feet (0.8 m) south of a witness post, and 0.1 foot (0.03
m) below grade.  The bench mark is on a rod driven to 54.0 feet (16.5 m) and
encased in concrete and a PVC pipe.

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

                                                   PUBLICATION DATE:  09/27/1983
Station ID: 9418983                                SUPERCEDED DATE:   04/21/2003
Name:       UPPER MAD RIVER SLOUGH, HUMBOLDT BAY              
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  ARCATA SOUTH                           Longitude:       124°  7.1' W


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


                         BENCH MARK STAMPING:  8983 E 1978

MONUMENTATION:           Survey Disk                               VM#:     8753
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 0.2 mile (0.3 km) east of the east end of the Lanphere Road
bridge over the slough, 60.0 feet (18.3 m) east of the fourth telephone pole
east of the east end of the bridge, 10.5 feet (3.2 m) south of the centerline of
Lanphere Road, 3.0 feet (0.9 m) north of a witness post, and 0.1 foot (0.3 m)
below grade.  The bench mark is driven to 65.0 feet (19.8 m) and encased in
concrete.

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

                                                   PUBLICATION DATE:  09/27/1983
Station ID: 9418983                                SUPERCEDED DATE:   04/21/2003
Name:       UPPER MAD RIVER SLOUGH, HUMBOLDT BAY              
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  ARCATA SOUTH                           Longitude:       124°  7.1' W


                            T I D A L   D A T U M S 


Tidal datums at UPPER MAD RIVER SLOUGH, HUMBOLDT BAY based on:

     LENGTH OF SERIES:      5 MONTHS
     TIME PERIOD:           AUGUST-DECEMBER 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9419750 CRESCENT CITY


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

     HIGHEST OBSERVED WATER LEVEL (12/28/1978)         =   9.46
     MEAN HIGHER HIGH WATER                     MHHW   =   7.93
     MEAN HIGH WATER                            MHW    =   7.22
     MEAN TIDE LEVEL                            MTL    =   4.26
     MEAN LOW WATER                             MLW    =   1.30
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (12/31/1978)         =  -2.22



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     8983 A 1978                                14.28      7.06
     8983 B 1978                                10.89      3.67
     8983 C 1978                                12.25      5.03
     8983 D 1978                                12.88      5.66
     8983 E 1978                                13.46      6.24


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

                                                   PUBLICATION DATE:  09/27/1983
Station ID: 9418983                                SUPERCEDED DATE:   04/21/2003
Name:       UPPER MAD RIVER SLOUGH, HUMBOLDT BAY              
            CALIFORNIA
NOAA Chart: 18622                                  Latitude:         40° 47.8' N
USGS Quad:  ARCATA SOUTH                           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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Revised: 08/08/2018
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