U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 1 of 5
Station ID: 9462620 PUBLICATION DATE: 04/21/2003
Name: UNALASKA, DUTCH HARBOR
ALASKA
NOAA Chart: 16529 Latitude: 53ø 52.8' N
USGS Quad: UNALASKA Longitude: 166ø 32.2' W
To reach the tidal bench marks from the Airport at Dutch Harbor there is only
one road leading from the Airport to the bridge that crosses over the inlet to
Unalaska. Once over the bridge, stay on main road till you come to a "T"
intersection (Generator Plant and school should be directly ahead). Make a left
turn and go to the end of road to Alyeska Seafoods, Inc. Tide gauge is located
on pier of fisheries property. The bench marks are located in the general
vicinity.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 7 1956
DESIGNATION: 946 2620 TIDAL 7
MONUMENTATION: Tidal Station disk VM#: 11814
AGENCY: US Coast and Geodetic Survey (USC&GS) PID:
SETTING CLASSIFICATION: Concrete foundation
The primary bench mark is a disk set in concrete footing of an old wooden
antenna, 50 m (164 ft) WNW of Carl's General Store, 11.27 m (37.0 ft) west of a
chain link fence on the east side of AT&T Alaska Communication System Building,
4.72 m (15.5 ft) SW of the the bulding, 0.15 m (0.5 ft) north of a white metal
witness sign attached to a wood stump, and 0.09 m (0.3 ft) below grade with a 4
in. PVC pipe around it.
BENCH MARK STAMPING: NO 16 1958
DESIGNATION: 946 2620 TIDAL 16
MONUMENTATION: Tidal Station disk VM#: 11815
AGENCY: US Coast and Geodetic Survey (USC&GS) PID:
SETTING CLASSIFICATION: Concrete gun-box
The bench mark is a disk set in the NW corner of an old concrete gun-box on the
south side of Bayview Avenue between Fourth and Fifth Street, 45.72 m (150.0 ft)
NW of the Unalaska School House in the middle of a fence along the NE side of
the school yard, and 4.57 m (15.0 ft) SW of the centerline of Bayview Avenue,
and 0.30 m (1.0 ft) SE of the NW corner of the bunker.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9462620 PUBLICATION DATE: 04/21/2003
Name: UNALASKA, DUTCH HARBOR
ALASKA
NOAA Chart: 16529 Latitude: 53ø 52.8' N
USGS Quad: UNALASKA Longitude: 166ø 32.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 19 1973
DESIGNATION: 946 2620 TIDAL 19
MONUMENTATION: Tidal Station disk VM#: 11816
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete gun-box
The bench mark is a disk set in the top center of an hexagonal World War II
concrete gun-box in front of an apartment building on south side of Bayview
Avenue between Third and Fourth Streets, 117 m (383 ft) NW of bench mark NO 16
1958, 6.71 m (22.0 ft) SSE of the centerline of Bayview Avenue, and 0.76 m (2.5
ft) above the ground level.
BENCH MARK STAMPING: NO 20 1974
DESIGNATION: 946 2620 TIDAL 20
MONUMENTATION: Tidal Station disk VM#: 11817
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete foundation
The bench mark is a disk set vertically in the eastern corner of the Alyeska
Bunk House, 46.02 m (151.0 ft) SW of bench mark 7 1956, 0.09 m (0.3 ft) west of
NE corner of bunkhouse, and 0.61 m (2.0 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9462620 PUBLICATION DATE: 04/21/2003
Name: UNALASKA, DUTCH HARBOR
ALASKA
NOAA Chart: 16529 Latitude: 53ø 52.8' N
USGS Quad: UNALASKA Longitude: 166ø 32.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: TIDAL BM 21 1975
DESIGNATION: 946 2620 TIDAL BM 21
MONUMENTATION: Tidal Station disk VM#: 11818
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete slab
The bench mark is a disk set in the north corner of a 1.37 m x 1.37 m (4.5 ft x
4.5 ft) concrete base, 14.33 m (47.0 ft) north of the west corner of the AT&T
Alaska Communication System Building, 3.96 m (13.0 ft) south of the southern
support leg of a large satellite dish, directly under a cable raceway, and 0.30
m (1.0 ft) above ground level.
BENCH MARK STAMPING: 2620 M 1982
DESIGNATION: 946 2620 M
MONUMENTATION: Tidal Station disk VM#: 11821
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Stainless steel rod
The bench mark is a disk located near the north corner of the green picket fence
surrounding the Russian Orthodox Church of the Holy Ascension, from the
northwestern-most corner of this picket fence and heading east the mark is
between 7th and 8th 4 x 4 vertical fence support, 5.49 m (18.0 ft) SW of the
centerline of the road that fronts the harbor, and 0.82 m (2.7 ft) SE of the
north corner of a wood picket fence which has a witness post attached outside
the church property and facing the water. The bench mark is crimped to the top
of a stainless steel rod driven 7.3 m (24 ft) to refusal, and protected by a
4-inch diameter black ABS pipe with cover projecting 7 cm (0.2 ft) above natural
grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9462620 PUBLICATION DATE: 04/21/2003
Name: UNALASKA, DUTCH HARBOR
ALASKA
NOAA Chart: 16529 Latitude: 53ø 52.8' N
USGS Quad: UNALASKA Longitude: 166ø 32.2' W
T I D A L D A T U M S
Tidal datums at UNALASKA, DUTCH HARBOR based on:
LENGTH OF SERIES: 5 Years
TIME PERIOD: January 1997 - 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 (01/27/1960) = 2.043
MEAN HIGHER HIGH WATER (MHHW) = 1.098
MEAN HIGH WATER (MHW) = 1.011
MEAN TIDE LEVEL (MTL) = 0.647
MEAN SEA LEVEL (MSL) = 0.635
MEAN LOW WATER (MLW) = 0.283
MEAN LOWER LOW WATER (MLLW) = 0.000
LOWEST OBSERVED WATER LEVEL (01/29/1999) = -0.754
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 7 1956 2.805 1.794
NO 16 1958 5.598 4.587
NO 19 1973 5.006 3.995
NO 20 1974 4.723 3.712
TIDAL BM 21 1975 3.242 2.231
2620 M 1982 3.344 2.333
Foot Notes:
The Dutch Harbor, Aleutian Islands region of Alaska has anomalous relative sea
level trends compared to most other geographic regions in the United States.
This is due to a general uplift of the land in the area, which has been
occurring at a rapid rate. Because of the magnitude of the sea level trends in
these areas, NOAA has adopted a procedure for computing accepted tidal datums
for the National Water Observation Network (NWLON) using the last several years
of sea level data rather than the 19 - year tidal epoch. The tide ranges are
still based on the 1983 - 2001 National Tidal Datum Epoch (NTDE) and are
applied to the five year (1997 - 2001) Mean Tide Level (MTL) to compute other
tidal datums. The adoption of this procedure was necessary to ensure that these
tidal datums accurately represent the existing stand of sea level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9462620 PUBLICATION DATE: 04/21/2003
Name: UNALASKA, DUTCH HARBOR
ALASKA
NOAA Chart: 16529 Latitude: 53ø 52.8' N
USGS Quad: UNALASKA Longitude: 166ø 32.2' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.