Superseded Bench Mark Sheet for 8779770, Port Isabel TX

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' W


To reach the tidal bench marks from the old lighthouse at Port Isabel, proceed
west on State Highway 100 for 0.9 mile (1.4 km) to a road leading to Port Isabel
Turning Basin, turn left onto the road and continue south for 0.7 mile (1.1 km)
to the Port Isabel Navigation District warehouse.  The bench marks are in the
vicinity of the warehouse, Port Road, and the Port Isabel High School complex.
The tide gage and staff are approximately 80 feet (24 m) north of the NE corner
of the warehouse.


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


                 PRIMARY BENCH MARK STAMPING:  NO 10 1973

MONUMENTATION:           Survey Disk                               VM#:      901
AGENCY:                                                            PID#:  AB1227
SETTING CLASSIFICATION:  Concrete Headwall


The bench mark is set flush in the top of a headwall on the east side of the
road leading to the warehouse, 73.0 feet (22.3 m) SSE of two oil pipe line
valves, 38.4 feet (11.7 m) south of a power pole, and 29.0 feet (8.8 m) east of
the centerline of Port Road.



                         BENCH MARK STAMPING:  2 1944

MONUMENTATION:           Survey Disk                               VM#:      894
AGENCY:                                                            PID#:  AB0249
SETTING CLASSIFICATION:  Concrete Deck


The bench mark is set in the concrete wharf deck at the NE corner of the
warehouse, 40 feet (12 m) SW of the NE concrete edge of the wharf, 23.5 feet
(7.2 m) SE of the NW edge of the concrete deck, and 1.5 feet (0.5 m) SW of the
NE corner of the warehouse.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' W


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


                         BENCH MARK STAMPING:  400 RL 1950 22+100

MONUMENTATION:           Survey Disk                               VM#:      896
AGENCY:                                                            PID#:  AB0247
SETTING CLASSIFICATION:  Concrete Driveway


The bench mark is located at the warehouse, 82.3 feet (25.1 m) SW of a
transformer pole, 52 feet (16 m) west of the centerline of the paved roadway,
24.5 feet (7.5 m) NW of the NW corner of the warehouse, and level with the
driveway which runs around the warehouse.



                         BENCH MARK STAMPING:  NO 7 1953

MONUMENTATION:           Survey Disk                               VM#:      897
AGENCY:                                                            PID#:  AB1229
SETTING CLASSIFICATION:  Concrete Footing


The bench mark is set in the concrete footing for an anchor bitt near the
warehouse, 96.5 feet (29.4 m) east of the centerline of Port Road, 55 feet     
(17 m) north of the NE corner of the warehouse, 30.4 feet (9.3 m) SE of the east
corner of the tide station instrument shelter, and 30.5 feet (9.3 m) SW of the
east face of the bulkhead.



                         BENCH MARK STAMPING:  NO 11 1972

MONUMENTATION:           Survey Disk                               VM#:      898
AGENCY:                                                            PID#:  AB1223
SETTING CLASSIFICATION:  Concrete Flagpole Base


The bench mark is set in the SW corner of a concrete flagpole base in the Port
Isabel High School complex, 40.7 feet (12.4 m) north of the NW corner of the
main building, 39.7 feet (12.1 m) east of the NE corner of the cinder block
building housing restrooms, and 1.3 feet (0.4 m) east of the east edge of the
sidewalk.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' W


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


                         BENCH MARK STAMPING:  NO 12 1972

MONUMENTATION:           Survey Disk                               VM#:      899
AGENCY:                                                            PID#:  AB1224
SETTING CLASSIFICATION:  Concrete Footing


The bench mark is set in the SW corner of the concrete footing of the SSE leg of
the Port Isabel water tower located in the vicinity of the Port Isabel High
School complex, 44.7 feet (13.6 m) east of the east wall of the office building,
and 8.5 feet (2.6 m) north of the south side of a rectangular chain link fence
around the water tower.



                         BENCH MARK STAMPING:  NO 13 1972

MONUMENTATION:           Survey Disk                               VM#:      900
AGENCY:                                                            PID#:  AB1226
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set flush in the top of the sea wall in the SE section of the
Port of Port Isabel, approximately 300 feet (91 m) north and across the
east-west road between the Port and the Turning Basin, 76.5 feet (23.3 m) north
of the centerline of the east-west road, 24 feet (7 m) east of the east edge of
the pier, and 1.9 feet (0.6 m) south of the north headwall of the sea wall.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' W


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


                         BENCH MARK STAMPING:  X 1406 1982

MONUMENTATION:           Metal Rod                                 VM#:      902
AGENCY:                                                            PID#:  AB1225
SETTING CLASSIFICATION:  Stainless Steel Rod in Sleeve


The bench mark is located in the vicinity of the abandoned Port Isabel oil dock,
120 feet (37 m) south of Bench Mark NO 13 1972, 43.6 feet (13.3 m) south of the
centerline of the paved road, 42.5 feet (13.0 m) west of a power pole with a
meter box, and 4 feet (1 m) SSW of power pole #234. The bench mark is the
highest point of a stainless steel rod in sleeve surrounded by a pipe with a
stamped access cover.



                         BENCH MARK STAMPING:  9

MONUMENTATION:           Survey Disk                               VM#:      903
AGENCY:                                                            PID#:  AB0245
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in the top of a concrete monument at the Port Isabel
Turning Basin, approximately halfway between the water tower and the abandoned
oil dock, 275 feet (84 m) east of the centerline of Port Road, 150.0 feet (45.7
m) SW of a power pole with a light and a transformer, 149 feet (45 m) south of
the centerline of the east-west road, and 0.2 foot (0.1 m) below the ground
level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' W


                            T I D A L   D A T U M S 


Tidal datums at PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD based on:

     LENGTH OF SERIES:      19 YEARS
     TIME PERIOD:           1960-1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:   


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

     HIGHEST OBSERVED WATER LEVEL (08/09/1980)         =   7.33
     MEAN HIGHER HIGH WATER                     MHHW   =   1.40
     MEAN HIGH WATER                            MHW    =   1.33
     MEAN TIDE LEVEL                            MTL    =   0.76
     MEAN LOW WATER                             MLW    =   0.19
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (06/14/1978)         =  -2.96

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 10 1973                                 10.44      9.11
     2 1944                                     11.71     10.38
     400 RL 1950 22+100                         11.74     10.41
     NO 7 1953                                  11.30      9.97
     NO 11 1972                                 19.16     17.83
     NO 12 1972                                 18.71     17.38
     NO 13 1972                                  4.75      3.42
     X 1406 1982                                 5.55      4.22
     9                                           3.17      1.84


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

                                                   PUBLICATION DATE:  04/10/1990
Station ID: 8779770                                SUPERCEDED DATE:   04/21/2003
Name:       PORT ISABEL, PORT ISABEL TURNING BASIN, LAGUNA MAD
            TEXAS
NOAA Chart: 11301                                  Latitude:         26°  3.6' N
USGS Quad:  PORT ISABEL                            Longitude:        97° 12.9' 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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