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

                                                                                
Station ID: 9440571                         PUBLICATION DATE:  01/23/2004
Name:       ALTOONA, COLUMBIA RIVER                           
            WA
NOAA Chart: 18523                           Latitude:   46° 15.9' N (  46.26500)
USGS Quad:  ROSBURG                         Longitude: 123° 39.2' W (-123.65300)


To reach the tidal bench marks from the intersection of State Highway 4 and
State Highway 403 at Rosburg, proceed south on State Highway 403 for
approximately 11 km (7 mi) to the town of Altoona.  The bench marks are located
along State Highway 403.  The tide gage and staff were located at the old
cannery building.


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


                 PRIMARY BENCH MARK STAMPING:  4 1940
                         DESIGNATION:          4

MONUMENTATION:           Bench Mark disk                       VM#:         8916
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  SC0534
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   46° 16.0' N (  46.26670)          LONGITUDE: 123° 39.4' W (-123.65700)


The primary bench mark is a disk set flush in bedrock with remains of a pier
foundation located along State Highway 403, 34 m (110 ft) east of the driveway
leading into the cannery, 30 m (100 ft) SE of bench mark 0571 A 1981, 25 m (82
ft) SE of a metal garage, and 10.00 m (32.8 ft) south of the centerline of the
highway.

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

                                                                                
Station ID: 9440571                         PUBLICATION DATE:  01/23/2004
Name:       ALTOONA, COLUMBIA RIVER                           
            WA
NOAA Chart: 18523                           Latitude:   46° 15.9' N (  46.26500)
USGS Quad:  ROSBURG                         Longitude: 123° 39.2' W (-123.65300)


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


                         BENCH MARK STAMPING:  0571 A 1981
                         DESIGNATION:          944 0571 A TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8917
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete door sill                    OPUS PID:        
LATITUDE:   46° 15.9' N (  46.26500)          LONGITUDE: 123° 39.2' W (-123.65300)


The bench mark is a disk set flush in concrete door sill located on the south
side of a large metal garage, 31 m (101 ft) NNW of bench mark 4 1940, 12.34 m
(40.5 ft) north of the centerline of State Highway 403, 9.30 m (30.5 ft) east of
the SW corner of the garage, and 0.15 m (0.5 ft) south of the garage wall.



                         BENCH MARK STAMPING:  0571 B 1981
                         DESIGNATION:          944 0571 B TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8918
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   46° 15.9' N (  46.26500)          LONGITUDE: 123° 39.2' W (-123.65300)


The bench mark is a disk set flush in bedrock located along State Highway 403
near Dan Stephans residence, 15.73 m (51.6 ft) east of the utility/light pole,
15 m (48 ft) west of a utility pole, 5.55 m (18.2 ft) north of the centerline of
the highway, and 0.06 m (0.2 ft) above the highway.

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

                                                                                
Station ID: 9440571                         PUBLICATION DATE:  01/23/2004
Name:       ALTOONA, COLUMBIA RIVER                           
            WA
NOAA Chart: 18523                           Latitude:   46° 15.9' N (  46.26500)
USGS Quad:  ROSBURG                         Longitude: 123° 39.2' W (-123.65300)


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


                         BENCH MARK STAMPING:  0571 C 1981
                         DESIGNATION:          944 0571 C TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8919
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   46° 15.9' N (  46.26500)          LONGITUDE: 123° 39.2' W (-123.65300)


The bench mark is a disk set flush in bedrock, 0.3 km (0.2 mi) west of the old
cannery building, 91 m (300 ft) north of a rock island, which lies west of the
cannery building, and 12 m (39 ft) south of the centerline of State Highway 403.



                         BENCH MARK STAMPING:  0571 D 1981
                         DESIGNATION:          944 0571 D TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         8920
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   46° 15.9' N (  46.26500)          LONGITUDE: 123° 39.2' W (-123.65300)


The bench mark is a disk set flush in bedrock located along State Highway 403,
0.8 km (0.5 mi) west of the old cannery building, 87 m (284 ft) NE of two large
free standing boulders at the bend in the highway, 15 m (50 ft) west of a
utility pole, and 10 m (32 ft) north of the centerline of the highway.

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

                                                                                
Station ID: 9440571                         PUBLICATION DATE:  01/23/2004
Name:       ALTOONA, COLUMBIA RIVER                           
            WA
NOAA Chart: 18523                           Latitude:   46° 15.9' N (  46.26500)
USGS Quad:  ROSBURG                         Longitude: 123° 39.2' W (-123.65300)


                            T I D A L   D A T U M S 


Tidal datums at ALTOONA, COLUMBIA RIVER based on:

     LENGTH OF SERIES:      5 MONTHS
     TIME PERIOD:           July 1981 - November 1981
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9439040 ASTORIA, TONGUE POINT, COLUMBIA RIVER


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

     MEAN HIGHER HIGH WATER                     MHHW   =  2.474
     MEAN HIGH WATER                            MHW    =  2.272
     MEAN TIDE LEVEL                            MTL    =  1.288
     MEAN SEA LEVEL                             MSL    =  1.283
     MEAN LOW WATER                             MLW    =  0.303
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     4 1940                                      3.730    1.458
     0571 A 1981                                 4.471    2.199
     0571 B 1981                                 6.339    4.067
     0571 C 1981                                 5.507    3.235
     0571 D 1981                                 5.710    3.438


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

                                                                                
Station ID: 9440571                         PUBLICATION DATE:  01/23/2004
Name:       ALTOONA, COLUMBIA RIVER                           
            WA
NOAA Chart: 18523                           Latitude:   46° 15.9' N (  46.26500)
USGS Quad:  ROSBURG                         Longitude: 123° 39.2' W (-123.65300)


                             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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.

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.