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

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


From the Adak airport parking lot, turn right and proceed 0.27 km (0.17 mi) east
to the intersection with Main Road, continue past Main Road and then take an
immediate right turn onto Mechanic Road, continue 0.60 km (0.37 mi) south on
Mechanic Road past the High School building to the intersection with Ptarmigan
Street, proceed straight across the intersection and continue south alongside
the Adak Fisheries building 0.28 km (0.17 mi) to Seawall Drive, turn left and
proceed east on Seawall Road 0.25 km (0.15 mi) to Pier 3 (or  proceed east on
Seawall Road 30 m (100 ft) to Pier    5, turn right and proceed 213 m (700 ft)
to the southern end of a red transformer building and the redundant tide house).
The tidal bench marks are located in the general vicinity of the pier. The white
tide house is located 0.08 km (0.05 mi) south from the entrance to Pier 3,
adjacent to two sheds.


                         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)                              IDB PID#:  UW7919
SETTING CLASSIFICATION:  Concrete pad                          OPUS PID:        
LATITUDE:   51° 51.7' N (  51.86142)          LONGITUDE: 176° 38.5' W (-176.64114)


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:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


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


                         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)                              IDB PID:         
SETTING CLASSIFICATION:  Concrete driveway                     OPUS PID:        
LATITUDE:   51° 51.8' N (  51.86272)          LONGITUDE: 176° 38.1' W (-176.63467)


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.



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

MONUMENTATION:           Tidal Station disk                    VM#:         1795
AGENCY:                  National Ocean Survey (NOS)           IDB PID:         
SETTING CLASSIFICATION:  Concrete wall                         OPUS PID:        
LATITUDE:   51° 51.7' N (  51.86250)          LONGITUDE: 176° 38.3' W (-176.63783)


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.

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

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


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


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

MONUMENTATION:           Tidal Station disk                    VM#:         1796
AGENCY:                  National Ocean Survey (NOS)           IDB PID:         
SETTING CLASSIFICATION:  Concrete driveway                     OPUS PID:        
LATITUDE:   51° 51.6' N (  51.86075)          LONGITUDE: 176° 38.8' W (-176.64669)


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:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


                         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)          IDB PID:         
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   51° 51.7' N (  51.86117)          LONGITUDE: 176° 38.6' W (-176.64311)


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.

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

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


                         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)                         IDB PID:         
SETTING CLASSIFICATION:  Road                                  OPUS PID:        
LATITUDE:   51° 51.7' N (  51.86239)          LONGITUDE: 176° 38.5' W (-176.64103)


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:  1380 H 2007
                         DESIGNATION:          946 1380 H

MONUMENTATION:           Tidal Station disk                    VM#:        18469
AGENCY:                  National Ocean Service (NOS)          IDB PID:         
SETTING CLASSIFICATION:  Concrete step                         OPUS PID:        
LATITUDE:   51° 51.8' N (  51.86300)          LONGITUDE: 176° 37.8' W (-176.63053)


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  6 of  8

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


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


                         BENCH MARK STAMPING:  1380 J 2012
                         DESIGNATION:          946 1380 J

MONUMENTATION:           Tidal Station disk                    VM#:        20574
AGENCY:                  National Ocean Service (NOS)          IDB PID:         
SETTING CLASSIFICATION:  Concrete Pier                         OPUS PID:        
LATITUDE:   51° 51.6' N (  51.86061)          LONGITUDE: 176° 38.3' W (-176.63758)


The bench mark is a disk set flush in the concrete pier near the southern end of
Pier 5, 22.08 m (72.4 ft) NW of the center of the southernmost bollard at the SE
corner of the pier, 10.67 m (35.0 ft) west of the inside vertical stanchion of
the southernmost handrail on a ladder, 1.44 m (4.7 ft) east of the NE corner of
the tidehouse, and 0.485 m (1.59 ft) south of the southeastern corner of the red
transformer building.

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

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


                            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
     North American Vertical Datum              NAVD88 =  0.278
     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
     BM 24 1968                                  5.782    4.728
     1380 C 1981                                 6.057    5.002
     1380 D 1982                                 2.779    1.724
     1380 F 1983                                 4.910    3.856
     946 1380 B                                  5.943    4.888
     1380 H 2007                                 6.085    5.031
     1380 J 2012                                 5.770    4.716


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

                                                                                
Station ID: 9461380                         PUBLICATION DATE:  10/04/2017
Name:       ADAK ISLAND, SWEEPER COVE                         
            AK
NOAA Chart: 16476                           Latitude:   51° 51.8' N (  51.86331)
USGS Quad:  ADAK                            Longitude: 176° 37.9' W (-176.63200)


                             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.