U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
To reach the station from the intersection of Pacific Highway 101 and 40th
Street in Seaview where Highway 101 turns east, proceed on Highway 101 also
called 40th Street for 11.3 km (7.0 mi) east and then north to the bridge over
Greenhead Slough. The water level sensor is on the east side of the bridge over
the channel and the enclosure is on land at the north end of the bridge. The
bench marks are along Highway 101 from the bridge and to the north 1 mile.
T I D A L B E N C H M A R K S
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: F 536 1987
DESIGNATION: F 536
MONUMENTATION: Flange-encased Rod VM#: 21894
AGENCY: NGS IDB PID#: SC1014
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 46° 22.4' N ( 46.37331) LONGITUDE: 123° 57.0' W (-123.94975)
The primary bench mark is a flange encased rod set in the brush along the E side
of highway 101, 12.88 m (42.3 ft) ENE of the centerline of highway, 12.83 m
(42.1 ft) SSE of N end of E guard rail, 10.22 m (33.5 ft) E of the wooden bridge
abutment at the E side of the road, 8.12 m (26.6 ft) ENE of a bridge warning
sign, 6.07 m (19.9 ft) SW of the S of a pair of one foot diameter wood gate
posts, and 0.36 m (1.2 ft) NW of a carsonite witness post. The datum point is
set 4 cm (2 inches) below ground, being the top of a stainless steel rod in a
sleeve and encased in a 5 inch (13 cm) national geodetic survey logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: G 536 1987
DESIGNATION: G 536
MONUMENTATION: Flange-encased Rod VM#: 21895
AGENCY: NGS IDB PID#: SC1015
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 46° 23.0' N ( 46.38317) LONGITUDE: 123° 57.0' W (-123.95061)
The bench mark is a stainless steel rod set at the brush line S of a pullout
along highway 101, 50.40 m (165.4 ft) SW of a 35 mph sign, 30.40 m (99.7 ft) SSW
of the SE end of a culvert under the highway, 25.34 m (83.1 ft) S of the
centerline of highway 101, 18.02 m (59.1 ft) S of the edge of pavement, and
17.71 m (58.1 ft) SSE of the W end of the guardrail along the S side of road.
The datum point is the top of a stainless steel rod set flush with the ground in
a 5 inch (13 cm) national geodetic survey logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0650 A 2016
DESIGNATION: 944 0650 A
MONUMENTATION: Flange-encased Rod VM#: 21896
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 46° 22.5' N ( 46.37533) LONGITUDE: 123° 57.0' W (-123.94992)
The bench mark is a flange encased rod set in a small clearing above the E side
of the large pullout, 38.05 m (124.8 ft) ESE of the intersection of a dirt
driveway and the fog line of highway 101, 32.31 m (106.0 ft) ENE of the
centerline of highway 101, 23.16 m (76.0 ft) SE of the metal gate post on the S
side of the dirt driveway, 2.34 m (7.7 ft) W of a 0.43 m (1.4 ft) diameter birch
tree, and 0.26 m (0.9 ft) W of a carsonite witness post. The datum point is set
10 cm (4 inches) below ground being the top of a stainless steel rod driven 4.9
m (16.1 ft) to refusal, in a sleeve extending to a depth of 0.9 m (3.0 ft) and
encased in a 6 inch (15 cm) NOS logo cap and concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0650 B 2016
DESIGNATION: 944 0650 B
MONUMENTATION: Flange-encased Rod VM#: 21897
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBFD96
LATITUDE: 46° 22.6' N ( 46.37689) LONGITUDE: 123° 57.1' W (-123.95153)
The bench mark is a flange encased rod set in a low grassy area along the W side
of highway 101, 146.3 m (480.0 ft) SE of the S end of a guardrail, 16.60 m (54.5
ft) SW of a traffic sign on E side of highway, 10.53 m (34.5 ft) SW of the
centerline of highway, 4.30 m (14.1 ft) SW of edge of pavement, and 0.20 m (0.7
ft) NE of carsonite witness post. The datum point is set 5 cm (2 inches) below
ground, being the top of a stainless steel rod driven 22.6 m (74.1 ft) to
refusal, in a 3 ft (0.9 m) sleeve, and encased in a 5 inch (13 cm) NOS logo
cover and concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0650 C 2016
DESIGNATION: 944 0650 C
MONUMENTATION: Flange-encased Rod VM#: 21898
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 46° 23.0' N ( 46.38314) LONGITUDE: 123° 57.1' W (-123.95225)
The bench mark is a flange encased rod set in the grass along the highway, 59.62
m (195.6 ft) NNE of the NE end of a guard rail, 16.29 m (53.4 ft) NE of the top
center of the end of a pipe culvert, 14.23 m (46.7 ft) NW of the centerline of
highway 101, 14.19 m (46.6 ft) NNE of a 35 mph sign, 10.17 m (33.4 ft) WSW of a
USFWS area closed sign, and 0.4 m (1.3 ft) S of a carsonite witness post. The
datum point is set 6 cm (2 inches) below ground being the top of a stainless
steel rod driven 10.4 m (34.1 ft) to refusal, in a sleeve extending to a depth
of 0.9 m (3.0 ft) and encased in a 6 inch (15 cm) NOS logo cap and concrete kick
block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
T I D A L D A T U M S
Tidal datums at GREENHEAD SLOUGH, WILLAPA BAY based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: May 2016 - July 2016
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9440910 TOKE POINT, WILLAPA BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.260
MEAN HIGH WATER MHW = 3.030
MEAN SEA LEVEL MSL = 1.794
MEAN TIDE LEVEL MTL = 1.695
MEAN LOW WATER MLW = 0.359
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
F 536 1987 5.297 2.267
G 536 1987 6.961 3.931
0650 A 2016 6.456 3.426
0650 B 2016 4.165 1.135
0650 C 2016 5.836 2.806
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 8
Station ID: 9440650 PUBLICATION DATE: 10/20/2016
Name: GREENHEAD SLOUGH, WILLAPA BAY
WA
NOAA Chart: 18504 Latitude: 46° 22.3' N ( 46.37222)
USGS Quad: LONG ISLAND Longitude: 123° 57.0' W (-123.95028)
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.