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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


To reach the tidal bench marks from Adak Airport, proceed  0.16 km (0.10 mi) to
Airport Access Road, turn right onto Airport Access Road and drive 0.24 km (0.15
mi) to the intersection with MAIN ROAD, continue straight for 0.64 km (0.40 mi)
passing new school building on the left to a stop sign.  Continue straight
through the intersection, for 0.24 km (0.15 mi) and turn left at the stop sign
onto Seawall Road.  Follow Seawall Road for 0.16 km (0.10 mi) to Pier #3 and
turn right onto pier.  The tidal bench marks are located in the general vicinity
of the pier. Tide gauge is located about 70 m (230 ft) from foot of pier at the
southern-most of two utility sheds which is painted white.


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


                 PRIMARY BENCH MARK STAMPING:  NO 18 1957
                         DESIGNATION:          946 1380 TIDAL 18

MONUMENTATION:           Tidal Station disk                        VM#:     1791
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID#:  UW7919
SETTING CLASSIFICATION:  Concrete pad


The primary bench mark is set in the SW corner of a 3.00 m (9.8 ft) x 2.30 m
(7.5 ft) concrete pad, 125.00 m (410.1 ft) south of the administration building
flag pole, 25.00 m (82.0 ft) NW of the rip rap edge, 17.40 m (57.1 ft) east of
the centerline of Seawall Road, 14.49 m (47.5 ft) east of the northern most
wooden guard rail post, and 2.42 m (7.9 ft) south of the center of a sewer hole
cover.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


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


                         BENCH MARK STAMPING:  NO 20 1957
                         DESIGNATION:          946 1380 TIDAL 20

MONUMENTATION:           Tidal Station disk                        VM#:     1792
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is set in a niche at the base on the SE side of a 4.60 m (15.1
ft) high rock outcropping on Hillside Road covered with many of coats of
graffiti paint, 27.00 m (88.6 ft) NW of the NW corner of a concrete highway
bridge over Sweeper Creek, 20.74 m (68.0 ft) WNW of the western most above
ground seam of a 0.33 m (1.1 ft) diameter steel pipe on a 0.55 m (1.8 ft) wide
wooden pipe platform which crosses Sweeper Creek, 19.00 m (62.3 ft) north of the
centerline of the paved road, 13.76 m (45.1 ft) NW of utility pole A2, 0.10 m
(0.3 ft) south of the south face of the rock outcrop, and 0.34 m (1.1 ft) below
ground.



                         BENCH MARK STAMPING:  BM 24 1968
                         DESIGNATION:          946 1380 BM 24

MONUMENTATION:           Tidal Station disk                        VM#:     1794
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID:         
SETTING CLASSIFICATION:  Concrete driveway


The bench mark is set in concrete pavement north of Pier 3 and near the roll up
door on the south side of Warehouse No. 2, 23.60 m (77.4 ft) west of the SE
corner of Warehouse No. 2, 14.30 m (46.9 ft) north of the center of Seawall
Road, 14.03 m (46.0 ft) east of the east edge of main door No. 6, and 0.76 m
(2.5 ft) south of Warehouse No. 2.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


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


                         BENCH MARK STAMPING:  1380 C 1981
                         DESIGNATION:          946 1380 C

MONUMENTATION:           Tidal Station disk                        VM#:     1795
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Concrete wall


The bench mark is set in a 0.60 m (2.0 ft) wide concrete bull rail at the NW
inshore end of Pier 5, 19.86 m (65.2 ft) west of the Pier Office Building, 5.70
m (18.7 ft) west of the centerline of the pier, 0.31 m (1.0 ft) east of the west
edge of bull rail, and 0.18 m (0.6 ft) south of the north end of bull rail.



                         BENCH MARK STAMPING:  1380 D 1982
                         DESIGNATION:          946 1380 D

MONUMENTATION:           Tidal Station disk                        VM#:     1796
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Concrete driveway


The bench mark is set in a concrete driveway for an overhead door on the east
side of the yellowing white metal building with red roof on the south side of
Seawall Road, 30.00 m (98.4 ft) south of the centerline of Seawall Road, 29.65 m
(97.3 ft) SW of a yellow fire hydrant, 27.72 m (90.9 ft) west of the NW corner
of a tan metal shed, 1.30 m (4.3 ft) SW of a 1.00 m (3.3 ft) high yellow
bollard, 0.84 m (2.8 ft) south of the north edge of the door opening, 0.52 m
(1.7 ft) east of the overhead door, and buried beneath 0.02 m (0.1 ft) of
gravel.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


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


                         BENCH MARK STAMPING:  1380 F 1983
                         DESIGNATION:          946 1380 F

MONUMENTATION:           Tidal Station disk                        VM#:     1797
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Stainless steel rod


The bench mark is a disk set on the north side of Seawall Road SE of the U.S.
Fish and Wildlife Service building, 119.0 m (390.4 ft) SE of the main entrance
to the building, 15.84 m (52.0 ft) north of the guard rail on the south side of
Seawall Road, 10.50 m (34.4 ft) north of the centerline of Seawall Road, 9.42m
(30.9 ft) east of 0.22 m (0.7 ft) diameter vertical steel pipe that is 0.86 m
(2.8 ft) tall and surrounded by three steel posts, and 0.90 m (3.0 ft) north of
an orange fiberglass NOS witness post.  The bench mark is set 8 cm (0.3 ft)
below grade, crimped to a stainless steel rod driven 14.6 m (48 ft) to refusal,
and encased in a 4-inch PVC pipe with a screw cap.



                         BENCH MARK STAMPING:  1380 G 1983
                         DESIGNATION:          946 1380 G

MONUMENTATION:           Tidal Station disk                        VM#:     1798
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Stainless steel rod


The bench mark is a disk set north of Seawall Road, 22.00 m (72.2 ft) north of
the centerline of Seawall Road, 5.20 m (17.1 ft) east of the centerline of the
road which runs perpendicular to Sewall Road, 0.90 m (3.0 ft) north of an orange
fiberglass NOS witness post, and 0.48 m (1.6 ft) south of power pole No. 412.
The bench mark is set 30 cm (1.0 ft) below the road grade, crimped to a
stainless steel rod driven 13.4 m (44 ft) to refusal, and encased in a 4-inch
black PVC pipe with a screw cap.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


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


                         BENCH MARK STAMPING:   
                         DESIGNATION:          946 1380 B
                         ALIAS:                B 1980,  Navy-S11, NO STAMPING 1

MONUMENTATION:           Survey disk                               VM#:     1799
AGENCY:                  US Navy (USN)                             PID:         
SETTING CLASSIFICATION:  Road


The bench mark is set in the centerline of Seawall Road near the Administration
Building, 87.00 m (285.4 ft) NW of fire plug #014, 25.84 m (84.8 ft) WSW of the
center of the anchor at the south end of the Administration Building, 15.03 m
(49.3 ft) south of the flag pole in front of the Administration Building, 13.01
(42.7 ft) SSE of a stop sign post, and 0.15 m (0.5 ft) below grade.



                         BENCH MARK STAMPING:  NO 14 1951
                         DESIGNATION:          946 1380 TIDAL 14

MONUMENTATION:           Tidal Station disk                        VM#:    12639
AGENCY:                  US Coast and Geodetic Survey (USC&GS)     PID:         
SETTING CLASSIFICATION:  Concrete monument


The bench mark is set in the NE corner of a concrete electrical manhole
foundation at the east end of concrete conduit that crosses Sweeper Creek, 54.90
m (180.1 ft) north of a bridge with tide gates across same creek, 18.00 m (59.1
ft) south of the centerline of Hillside Road, 10.71 m (35.1 ft) south of the
south side of a bridge abutment on the east side of the creek, 6.56 m (21.5 ft)
west of a guard rail that runs north/south on the west side of the road leading
to the fuel dock, and 6.31 m (20.7 ft) NW of a 1.20 m (3.9 ft) tall green
phoneline junction box.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


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


                         BENCH MARK STAMPING:  1380 H 2007
                         DESIGNATION:          946 1380 H

MONUMENTATION:           Tidal Station disk                        VM#:    18469
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Concrete step


The bench mark is a disk set in concrete on the north end of the second step
leading up to the loading dock on the west side of the eastern most warehouse
which is yellow, 41.70 m (136.8 ft) NE of the intersection of the centerlines of
two streets, 10.29 m (33.8 ft) north of the SW corner of the warehouse, and 0.67
m (2.2 ft) east of the west edge of the yellow warehouse loading area.

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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' W


                            T I D A L   D A T U M S 


Tidal datums at ADAK ISLAND, SWEEPER COVE based on:

     LENGTH OF SERIES:      19 YEARS
     TIME PERIOD:           January 1983 - December 2001
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:   


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

     HIGHEST OBSERVED WATER LEVEL (12/28/1966)         =  2.084
     MEAN HIGHER HIGH WATER                     MHHW   =  1.131
     MEAN HIGH WATER                            MHW    =  1.055
     MEAN SEA LEVEL                             MSL    =  0.649
     MEAN TIDE LEVEL                            MTL    =  0.613
     MEAN LOW WATER                             MLW    =  0.172
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (11/26/2003)         = -0.930

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     NO 18 1957                                  5.797    4.742
     NO 20 1957                                  3.967    2.913
     BM 24 1968                                  5.784    4.729
     1380 C 1981                                 6.057    5.002
     1380 D 1982                                 2.779    1.724
     1380 F 1983                                 4.910    3.856
     1380 G 1983                                 5.540    4.486
     946 1380 B                                  5.944    4.890
     NO 14 1951                                  4.191    3.136
     1380 H 2007                                 6.086    5.031


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

                                                                                
Station ID: 9461380                                PUBLICATION DATE:  10/12/2011
Name:       ADAK ISLAND, SWEEPER COVE                         
            ALASKA
NOAA Chart: 16476                                  Latitude:         51° 51.8' N
USGS Quad:  ADAK                                   Longitude:       176° 37.9' 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.