U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9439201 PUBLICATION DATE: 04/02/2024
Name: ST. HELENS, COLUMBIA RIVER
OR
NOAA Chart: 18524 Latitude: 45° 51.9' N ( 45.86500)
USGS Quad: ST. HELENS Longitude: 122° 47.8' W (-122.79700)
To reach the tidal bench marks from Seattle, head south on I-5, and take
Kelso-Longview Highway 30 exit (Exit 36), turn left onto Oregon Way (Highway 30
East), Highway 30 becomes B Street through the town of Rainier. Proceed through
Rainier approximately 17 mi (27 km) to the town of St. Helens, turn east onto
Columbia Boulevard (the main street in the town of St. Helens) and continue east
on Columbia Boulevard to 1st Street. Turn south on 1st Street; turn east on St.
Helens Street (down toward the river). St. Helens Street terminates in what is
referred to as "The Strand", a parking lot behind the Old Courthouse/Museum.
Turn south into the parking lot and proceed to the SE corner to shelter.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9201 A 2002
DESIGNATION: 943 9201 A
MONUMENTATION: Tidal Station disk VM#: 16644
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock outcrop OPUS PID#: BBGN92
LATITUDE: 45° 51.9' N ( 45.86550) LONGITUDE: 122° 48.0' W (-122.79917)
The primary bench mark is a disk set flush in the top of a bedrock outcropping
along a rock wall that separates South 1st Street in Saint Helens west of the
front door of 110 1st Street, 30.40 m (99.7 ft) north of 2nd northern most
antiquated light pole on South 1st Street, 10.48 m (34.4 ft) south of northern
most antiquated light pole on South 1st Street, 4.90 m (16.1 ft) west of the
centerline of lower South 1st Street, and 0.45 m (1.5 ft) above the street
level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9439201 PUBLICATION DATE: 04/02/2024
Name: ST. HELENS, COLUMBIA RIVER
OR
NOAA Chart: 18524 Latitude: 45° 51.9' N ( 45.86500)
USGS Quad: ST. HELENS Longitude: 122° 47.8' W (-122.79700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1940
DESIGNATION: TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 16661
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete curb OPUS PID:
LATITUDE: 45° 51.8' N ( 45.86311) LONGITUDE: 122° 47.9' W (-122.79756)
The bench mark is a disk set in a circular concrete foundation of the flagpole
in the center of the plaza west of the Columbia County Courthouse in Saint
Helens, 9.30 m (30.5 ft) north of the south curb, 9.20 m (30.2 ft) south of the
north curb, 1.68 m (5.5 ft) east of the centerline of the flagpole, and 0.46 m
(1.5 ft) above the sidewalk.
BENCH MARK STAMPING: NO 4 1940
DESIGNATION: 943 9201 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 16662
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete sidewalk OPUS PID:
LATITUDE: 45° 51.8' N ( 45.86383) LONGITUDE: 122° 47.9' W (-122.79825)
The bench mark is a disk set in the concrete sidewalk at the SE corner of Saint
Helens and First Streets, 4.42 m (14.5 ft) east of the curb on First Street,
4.42 m (14.5 ft) south of the curb of Saint Helens Street, about 0.3 m (1 ft) NW
of the NW corner of the former U.S. Bank building, and set flush with grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9439201 PUBLICATION DATE: 04/02/2024
Name: ST. HELENS, COLUMBIA RIVER
OR
NOAA Chart: 18524 Latitude: 45° 51.9' N ( 45.86500)
USGS Quad: ST. HELENS Longitude: 122° 47.8' W (-122.79700)
T I D A L D A T U M S
Tidal datums at ST. HELENS, COLUMBIA RIVER based on:
LENGTH OF SERIES: 20 YEARS
TIME PERIOD: 08/2002 - 10/2021 Low Water Months Only
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9439040 ASTORIA, TONGUE POINT, COLUMBIA RIVER
Elevations of tidal datums referred to Columbia River Datum (CRD), in METERS:
HIGHEST OBSERVED WATER LEVEL (03/30/2017) = 4.670
MEAN HIGHER HIGH WATER MHHW = 1.521
MEAN HIGH WATER MHW = 1.374
MEAN TIDE LEVEL MTL = 0.993
MEAN SEA LEVEL MSL = 0.992
MEAN LOW WATER MLW = 0.612
MEAN LOWER LOW WATER MLLW = 0.542
COLUMBIA RIVER DATUM CRD = 0.000
North American Vertical Datum NAVD88 = -1.303
LOWEST OBSERVED WATER LEVEL (09/21/2003) = -0.097
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MHW CRD
9201 A 2002 19.154 20.528
NO 3 1940 11.180 12.554
NO 4 1940 13.415 14.789
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9439201 PUBLICATION DATE: 04/02/2024
Name: ST. HELENS, COLUMBIA RIVER
OR
NOAA Chart: 18524 Latitude: 45° 51.9' N ( 45.86500)
USGS Quad: ST. HELENS Longitude: 122° 47.8' W (-122.79700)
Foot Notes:
Columbia River Datum (CRD) is the adopted fixed low water reference plane for
this area. CRD is a U.S. Army Corps of Engineers non-tidal datum defined at
distinct river miles relative to NAVD88, and is used as chart datum above river
mile 23 on the Columbia River. Datums are computed using observations from the
low river stages of the year, generally August through October due to the
masking of the tidal signal from strong seasonal river runoff during other
portions of the year. Depending on river flow, water levels can be significantly
higher than Columbia River Datum. As of 2014, the U.S. Army Corps of Engineers
provided updated offsets for CRD that have been applied to this station. Station
Datum (STND) is no longer set equal to CRD.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9439201 PUBLICATION DATE: 04/02/2024
Name: ST. HELENS, COLUMBIA RIVER
OR
NOAA Chart: 18524 Latitude: 45° 51.9' N ( 45.86500)
USGS Quad: ST. HELENS Longitude: 122° 47.8' W (-122.79700)
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.