U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
To reach the tidal bench marks from the intersection of State Highway 360 and
County Road 624 south of Calao, proceed 6.1 miles (9.8 km) north on County Road
624 to the Lewisetta Marina and Triggs Store. The bench marks are located in
the vicinity of the marina and store. The tide gage and staff are located on
the fuel pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: R 462 1971
MONUMENTATION: Survey Disk VM#: 493
AGENCY: PID#: GV0156
SETTING CLASSIFICATION: Metal Rod with Base Plate
The bench mark is located SE of Triggs Store, 225 feet (69 m) south of Bench
Mark Q 462 1971, 176 feet (54 m) SE of the east corner of Triggs Store, 86.4
feet (26.3 m) SW of the SW corner of the main portion of JW Triggs house, 8.0
feet (2.4 m) WNW of the most southwesterly cottonwood tree, and 0.7 foot (0.2 m)
SE of a metal witness post. The bench mark is 0.3 foot (0.1 m) below ground,
encased in a 4-inch orangeburg pipe at ground level.
BENCH MARK STAMPING: NO 2 1959
MONUMENTATION: Survey Disk VM#: 494
AGENCY: PID#: GV0157
SETTING CLASSIFICATION: Concrete Monument
The bench mark is located on the SW side of the aluminum boat and storage shed
at the Lewisetta Marina, 32.9 feet (10.0 m) SE of the south corner of a cinder
block pump house, 32.0 feet (9.8 m) west of the south corner of the storage
shed, and 29.6 feet (9.0 m) ENE of wood utility pole #T454-160L-IR. The bench
mark is set in the top of a concrete monument level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: Q 462 1971
MONUMENTATION: Survey Disk VM#: 495
AGENCY: PID#: GV0155
SETTING CLASSIFICATION: Concrete Post
The bench mark is located in the grassy area north of Triggs Store, 119 feet (36
m) NW of the centerline of County Road 624, 86.8 feet (26.5 m) NE of the north
corner of Triggs Store, 76.0 feet (23.2 m) ESE of underground cable marker #491,
and 13.0 feet (4.0 m) east of power pole #T454-159L, which is braced by three
guy wires. The bench mark is set in the top of a concrete post 0.1 foot (0.03
m) below ground level.
BENCH MARK STAMPING: NO 5 1973
MONUMENTATION: Survey Disk VM#: 496
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Step
The bench mark is located in the vicinity of the bath house and fuel pier at the
Lewisetta Marina, 67.6 feet (20.6 m) SW of the SW face of Triggs Store, 43.9
feet (13.4 m) west of the steel sign post for the gas pumps, 19.4 feet (5.9 m)
north of the shore end of the wooden pier, and 6.9 feet (2.1 m) NE of the NE
corner of the bottom concrete step of the bath house. The bench mark is set
flush in the east corner of the bottom concrete step of the bath house and 0.1
foot (0.03 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 6 1973
MONUMENTATION: Survey Disk VM#: 497
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is located on the SW side of the gas pumps at Triggs Store, 42.8
feet (13.0 m) east of the NE corner of the shore end of the wooden pier, 39.2
feet (11.9 m) WSW of the SE corner of the Post Office building, and 5.0 feet
(1.5 m) NW of the steel sign post for gas pumps. The bench mark is set flush in
the lower portion of the concrete foundation of the gas pumps and 0.4 foot (0.1
m) above ground level.
BENCH MARK STAMPING: 5750 G 1978
MONUMENTATION: Survey Disk VM#: 498
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is located in a group of four trees in the grassy area east of
Triggs Store, 130 feet (40 m) east of power pole #T454 159L, 27.9 feet (8.5 m)
north of a 20-inch locust tree, 20.0 feet (6.1 m) NE of the north corner of
Triggs Store, 19.0 feet (5.8 m) NW of the centerline of State Road 6211, and 2.0
feet (0.6 m) NW of a birch tree. The bench mark is crimped to the top of a
stainless steel rod driven 48 feet (15 m) to refusal, encased in a PVC pipe and
concrete kickblock and 0.1 foot (0.03 m) below ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5750 H 1978
MONUMENTATION: Survey Disk VM#: 499
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is located in the vicinity of the aluminum boat and storage shed
at the Lewisetta Marina, 99.0 feet (30.2 m) south of the east corner of a wooden
boat shed on the water, 86.5 feet (26.4 m) NW of the NW corner of Triggs Store,
and 1.2 feet (0.4 m) NE of the east corner of the storage shed. The bench mark
is crimped to the top of stainless steel rod driven 48 feet (15 m) to refusal,
encased in a PVC pipe and concrete kickblock and level with the ground.
BENCH MARK STAMPING: 5750 J 1979
MONUMENTATION: Survey Disk VM#: 500
AGENCY: PID#: AJ4589
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is located on the east side of County Road 624 at the Lewisetta
Chapel, 52.7 feet (16.1 m) NW of the north corner of the Chapel, 17.0 feet (5.2
m) east of the centerline of County Road 624, and 1.8 feet (0.5 m) west of a
utility pole. The bench mark is crimped to the top of a stainless steel rod
driven 36 feet (11 m) to refusal, encased in a PVC pipe and concrete kickblock
and level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5750 K 1980
MONUMENTATION: Survey Disk VM#: 501
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located in the Y junction of the dirt road near the boat ramp
at the Lewisetta Marina, 83.7 feet (25.5 m) ENE of the NE end of the concrete
boat ramp, 24.1 feet (7.3 m) NW of the centerline of County Road 624, 13.9 feet
(4.2 m) NNE of the centerline of the south part of the dirt driveway, 13.5 feet
(4.1 m) south of the centerline of the north part of the dirt driveway, and 5.4
feet (1.6 m) NW of a 3-foot diameter dead tree. The bench mark is crimped to
the top of a galvanized steel rod driven 48 feet (15 m) to refusal, encased in a
PVC pipe and concrete kickblock and level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' W
T I D A L D A T U M S
Tidal datums at LEWISETTA, POTOMAC RIVER based on:
LENGTH OF SERIES: 11 YEARS
TIME PERIOD: 1974-1984
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8594900 WASHINGTON, DC
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (03/19/1983) = 3.62
MEAN HIGHER HIGH WATER MHHW = 1.53
MEAN HIGH WATER MHW = 1.38
MEAN TIDE LEVEL MTL = 0.75
* NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 0.28
MEAN LOW WATER MLW = 0.11
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/05/1975) = -2.59
* NGVD reference based on adjustment of 1972 and NOS levels of 1984.
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
R 462 1971 4.92 3.54
NO 2 1959 4.52 3.14
Q 462 1971 4.25 2.87
NO 5 1973 5.11 3.73
NO 6 1973 4.90 3.52
5750 G 1978 3.67 2.29
5750 H 1978 4.17 2.79
5750 J 1979 4.65 3.27
5750 K 1980 5.39 4.01
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
PUBLICATION DATE: 08/19/1985
Station ID: 8635750 SUPERCEDED DATE: 04/21/2003
Name: LEWISETTA, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12285 Latitude: 37° 59.8' N
USGS Quad: HEATHSVILLE Longitude: 76° 27.8' 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.