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Superseded Bench Mark Sheet for 9415020, Point Reyes CA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


       To reach the tidal bench marks from Inverness Post Office, proceed 14.6
miles (23.5 km) NW along Sir Francis Drake Highway (taking the right fork to
Point Reyes Beach south), turn left onto Chimney Rock Road (an unmarked road
immediately after passing a dairy farm), turn left at the parking lot 'Y'
intersection, and follow the road down to a private pier.  The bench marks are
along the road leading to the pier, and to the SE.  The tide gauge is 11 feet (3
m) east of the south corner of the private pier building.


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


                 PRIMARY BENCH MARK STAMPING:  BM B243 1949

MONUMENTATION:           Survey Disk                               VM#:     1732
AGENCY:                                                            PID#:  HT1839
SETTING CLASSIFICATION:  Bedrock


The primary bench mark is set in the NE slope of an outcrop at the first rocky
point SE of a private pier, about 0.2 mile (0.3 km) NW along the beach from the
former U.S. Coast Guard pier, 45 feet (14 m) SE of the centerline of the private
pier, and about 4 feet (1 m) above ground.



                         BENCH MARK STAMPING:  1929

MONUMENTATION:           Survey Disk                               VM#:     1730
AGENCY:                                                            PID#:  HT1837
SETTING CLASSIFICATION:  Bedrock


The bench mark is set in the top of the first rocky point along the beach west
of the Coast Guard station building, 240 feet (73 m) west of the west side of
the Coast Guard station building, 159 feet (48 m) west of a wooden retaining
wall, and 0.8 foot (0.2 m) NE of the NE face of the rock cliff.  (Note: 
Stamping illegible except for 1929.   Historically BM FIVE 1929.)

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


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


                         BENCH MARK STAMPING:  BM A243 1949

MONUMENTATION:           Survey Disk                               VM#:     1731
AGENCY:                                                            PID#:  HT1838
SETTING CLASSIFICATION:  Concrete Momument


The bench mark is set near the first rocky point NW of a private pier, 163 feet
(50 m) east of the center of a 2-foot (1 m) square concrete monument located on
the rocky point, 122 feet (37 m) NW of Bench Mark BM B243 1949, 30.2 feet (9.2
m) east of the center of the most southeasternly of three 0.5-foot (0.2 m) high
circular concrete pilings, 20.2 feet (6 m) NNW of a utility pole, 3 feet (1 m)
south of an orange witness post, and 0.3 foot (0.1 m) below grade.



                         BENCH MARK STAMPING:  NO 10 1973

MONUMENTATION:           Survey Disk                               VM#:     1735
AGENCY:                                                            PID#:  HT3513
SETTING CLASSIFICATION:  Concrete Sidewalk


The bench mark is set in a sidewalk along the south wall of the Coast Guard
station, 5.5 feet (1.7 m) SE of the SE corner of the station, and 1 foot (0.3 m)
NW of the SE corner of the sidewalk.



                         BENCH MARK STAMPING:  TIDAL BM 11 1975

MONUMENTATION:           Survey Disk                               VM#:     1737
AGENCY:                                                            PID#:  HT3511
SETTING CLASSIFICATION:  Bedrock


The bench mark is set along the road leading to the Coast Guard station, 89.0
feet (27.1 m) SE of a brown plastic roadside reflector post on the shoreward
side of the road, 42.5 feet (13.0 m) SW of the second telephone pole NW of the
Coast Guard boat house, 11 feet (3 m) south of the centerline of the road, and 3
feet (1 m) above the surface of the road.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


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


                         BENCH MARK STAMPING:  5020 J 1978

MONUMENTATION:           Survey Disk                               VM#:     1738
AGENCY:                                                            PID#:  HT3510
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is set along the road leading to the Coast Guard station, 325
feet (99 m) NW of Bench Mark TIDAL BM 11 1975, 92 feet (28 m) east of the
centerline intersection of the paved and dirt roads, 55 feet (17 m) west of a
utility pole, 13.5 feet (4.1 m) NNE of the centerline of the paved road, and 3
feet (1 m) NNE of a 4-inch square redwood witness post.  The bench mark is level
with the ground, crimped to a galvanized steel rod driven 16 feet (5 m) to
refusal, and encased in a 4-inch PVC pipe.



                         BENCH MARK STAMPING:  5020 K 1978

MONUMENTATION:           Survey Disk                               VM#:     1739
AGENCY:                                                            PID#:  HT3504
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 650 feet (198 m) west along the paved road from Bench Mark BM
A243 1949, 300 feet (91 m) north of the intersection of the paved road with the
road leading west to Sir Francis Drake Highway, 16 feet (5 m) SE of the
centerline of the road to the pier, and 2 feet (1 m) SE of a 4-inch square
redwood witness post.  The bench mark is 0.2 foot (0.1 m) below ground level,
crimped to a galvanized steel rod driven 20 feet (6 m) to refusal, and encased
in a 4-inch PVC pipe.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


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


                         BENCH MARK STAMPING:  5020 L 1983

MONUMENTATION:           Survey Disk                               VM#:     1740
AGENCY:                                                            PID#:  HT3506
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in a 1.8-foot (0.5 m) diameter cylindrical concrete
monument formerly used as an inshore pier piling on the toe of a bedrock
outcropping, 218 feet (66 m) NW of the inshore end of a private pier, 182.5 feet
(55.6 m) NW of a utility pole, 164.8 feet (50.2 m) NW of Bench Mark BM A243
1949, 45.5 feet (13.9 m) NE of the centerline of the paved road, 5.2 feet (1.6
m) NE of an orange witness post, and 2.0 feet (0.6 m) above ground level.



                         BENCH MARK STAMPING:  5020 M 1985

MONUMENTATION:           Survey Disk                               VM#:     1741
AGENCY:                                                            PID#:  HT3503
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is set 225 feet (69 m) SE of Bench Mark 5020 K 1978, 135 feet (41
m) west of power pole #B2, 69.7 feet (21 m) east of a metal brown and white
roadside sign saying 'Docks are closed to public use,' 27.8 feet (8.5 m) west of
the east end of a wooden guardrail at the fork of Chimney Rock Road, 26.1 feet
(8.0 m) east of the west end of the guard rail, and 4.5 feet (1.4 m) seaward of
a guard rail and a guard rail post with metal witness sign.  The bench mark is
0.5 foot (0.2 m) below ground level, beneath an aluminum access cover, crimped
to a stainless steel rod driven 14 feet (4 m) to refusal, and protected by a
concrete sleeve.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


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


                         BENCH MARK STAMPING:  5020 N 1985

MONUMENTATION:           Survey Disk                               VM#:     1742
AGENCY:                                                            PID#:  HT3507
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 50.1 feet (15.3 m) WNW of the NW corner of the concrete steps
leading to the front of a two-story residence on the road leading to the Coast
Guard boat house, 47.4 feet (14.4 m) NW of a red water pipe protruding
vertically 2.5 feet (0.8 m) above the west lawn of the residence, 41.4 feet
(12.6 m) south of a power pole, 17.8 feet (5.4 m) SSE of a 4.5-foot (1.4 m) high
white wooden post, 6.3 feet (1.9 m) WNW of a tree, and 1.5 feet (0.5 m) south of
a white witness post.  The bench mark is 0.5 foot (0.2 m) below ground level,
beneath an aluminum access cover, crimped to a stainless steel rod driven 15
feet (5 m) to refusal, and protected by a concrete sleeve.



                         BENCH MARK STAMPING:  5020 P 1985

MONUMENTATION:           Survey Disk                               VM#:     1743
AGENCY:                                                            PID#:  HT3508
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is set on a hillside, 450 feet (137 m) SE of Bench Mark 5020 N
1985, 120 feet (37 m) SE of Bench Mark 5020 R 1985, 58 feet (18 m) east of a
barbed wire fence, 32 feet (10 m) SE of the southernmost of two 4-foot (1 m)
high brown fiberglass roadside reflectors marking a drainage pipe crossing
beneath the roadway, 25 feet (8 m) south of the centerline of the road leading
to the Coast Guard boat house, and 2.6 feet (0.8 m) north of an orange NOS
fiberglass witness post.  The bench mark is 3.0 feet (1 m) above road level, 0.5
foot (0.2 m) below ground level, beneath an aluminum access cover, crimped to a
stainless steel rod driven 15 feet (5 m) to refusal, and protected by a concrete
sleeve.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


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


                         BENCH MARK STAMPING:  5020 Q 1985

MONUMENTATION:           Survey Disk                               VM#:     1744
AGENCY:                                                            PID#:  HT3505
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is 191 feet (58 m) north of Bench Mark 5020 M 1985, 151 feet (46
m) east of Bench Mark 5020 K 1978, and 15 feet (5 m) north of the centerline of
the road leading to a private pier.  The bench mark is 0.5 foot (0.2 m) below
the ground, beneath an aluminum access cover, crimped to a stainless steel rod
driven 8 feet (2 m) to refusal, and protected by a concrete sleeve.



                         BENCH MARK STAMPING:  5020 R 1985

MONUMENTATION:           Survey Disk                               VM#:     1745
AGENCY:                                                            PID#:  HT3509
SETTING CLASSIFICATION:  Concrete Retaining Wall


The bench mark is set in a concrete retaining wall which runs along the SW side
of the road leading to a garage, 240 feet (73 m) SE of Bench Mark 5020 N 1985,
1.6 feet (0.5 m) west of a water faucet, 1.6 feet (0.5 m) west of the west
corner of the garage, and 0.3 foot (0.1 m) above the level of the driveway. 
(Note:  Due to a garage overhang, a short rod is required.)

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  7 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' W


                            T I D A L   D A T U M S 


Tidal datums at POINT REYES, DRAKES BAY based on:

     LENGTH OF SERIES:      16 YEARS
     TIME PERIOD:           1975-1990
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9414290 SAN FRANCISCO


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

     HIGHEST OBSERVED WATER LEVEL (12/03/1983)         =   8.67
     MEAN HIGHER HIGH WATER                     MHHW   =   5.77
     MEAN HIGH WATER                            MHW    =   5.11
     MEAN TIDE LEVEL                            MTL    =   3.15
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   2.85
     MEAN LOW WATER                             MLW    =   1.18
   * North American Vertical Datum              NAVD88 =   0.24
     LOWEST  OBSERVED WATER LEVEL (01/19/1988)         =  -2.48

   * NGVD, NAVD based on elevations in Quad 37122444, 1992 and NOS leveling of
     1992.
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     BM B243 1949                               12.58      7.47
     1929                                        7.93      2.82
     BM A243 1949                               11.80      6.69
     NO 10 1973                                 14.60      9.49
     TIDAL BM 11 1975                           55.06     49.95
     5020 J 1978                                83.02     77.91
     5020 K 1978                                80.07     74.96
     5020 L 1983                                19.75     14.64
     5020 M 1985                                106.72    101.61
     5020 N 1985                                91.03     85.92
     5020 P 1985                                65.37     60.26
     5020 Q 1985                                65.24     60.13
     5020 R 1985                                71.06     65.95


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  8 of  8

                                                   PUBLICATION DATE:  04/12/1994
Station ID: 9415020                                SUPERCEDED DATE:   04/21/2003
Name:       POINT REYES, DRAKES BAY                           
            CALIFORNIA
NOAA Chart: 18647                                  Latitude:         37° 59.8' N
USGS Quad:  DRAKES BAY                             Longitude:       122° 58.5' 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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