U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 05/15/1989
Station ID: 8637444 SUPERCEDED DATE: 04/21/2003
Name: BROWNS BAY
VIRGINIA
NOAA Chart: 12238 Latitude: 37° 18.0' N
USGS Quad: ACHILLES Longitude: 76° 24.2' W
To reach the tidal bench marks from the intersection of Colonial Parkway and
U.S. Highway 17, proceed north on U.S. Highway 17 (across George P. Coleman
Memorial Bridge over the York River) for 3.5 miles (5.6 km) to State Highway
216, then east on State Highway 216 for 3.9 miles (6.3 km) to where it turns
into State Highway 653, then NE on State Highway 653 for 1.8 miles (2.9 km) to
State Highway 652, then turn left onto State Highway 652 and go 0.2 mile (0.3
km) to State Highway 651, then turn right onto State Highway 651 and go 1.1
miles (1.8 km) to its end. The bench marks are along State Highway 651. The
tide gage and staff were on the Shackelford-Thomas Seafood Company Pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: BROWNS BAY NO 1 1947
MONUMENTATION: Survey Disk VM#: 3420
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Filled Pipe
The bench mark is about 330 feet (101 m) west of the shore end of the pier, 200
feet (61 m) NW of Bench Mark 7444 B 1982 on the same 3.0-foot (0.9 m) high ridge
as Bench Mark 7444 B 1982, 95.5 feet (29.1 m) south of the centerline of State
Highway 651, and 1.0 foot (0.3 m) from a witness post. NOTE: The bench mark is
loose in the top of a 3/4-inch pipe.
BENCH MARK STAMPING: BROWNS BAY NO 2 1947
MONUMENTATION: Survey Disk VM#: 3421
AGENCY: PID:
SETTING CLASSIFICATION: Tile Pipe
The bench mark is set in the top of a concrete filled tile pipe, 525 feet
(160 m) WSW of the shore end of the pier, 225.0 feet (68.6 m) west of Bench Mark
BROWNS BAY NO 1 1947, 20.0 feet (6.1 m) north of the centerline of State Highway
651, 1.0 foot (0.3 m) from a witness post, and 0.25 foot (0.08 m) above ground
level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 05/15/1989
Station ID: 8637444 SUPERCEDED DATE: 04/21/2003
Name: BROWNS BAY
VIRGINIA
NOAA Chart: 12238 Latitude: 37° 18.0' N
USGS Quad: ACHILLES Longitude: 76° 24.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7444 A 1982
MONUMENTATION: Survey Disk VM#: 3422
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in the concrete loading dock at Shackelford-Thomas
Seafood Company, 45.5 feet (13.9 m) south of the SW corner of the pier, 19.8
feet (6.0 m) south of the north edge of the loading dock, and 0.9 foot (0.3 m)
west of the east edge of the building.
BENCH MARK STAMPING: 7444 B 1982
MONUMENTATION: Survey Disk VM#: 3423
AGENCY: PID:
SETTING CLASSIFICATION: Unspecified Rod
The bench mark is on a 3.0-foot (0.9 m) high ridge south of the Shackelford-
Thomas Seafood Company parking lot, 262 feet (80 m) SSW of Bench Mark 7444 A
1982, 214 feet (65 m) SSW of the most northwestern corner of the seafood
factory, 207 feet (63 m) south of the centerline of State Highway 651, 150 feet
(46 m) SW of the SW corner of a cinder block outhouse, and 0.3 foot (0.1 m) west
of a witness post. The bench mark is 0.4 foot (0.1 m) below ground level,
crimped to an unspecified steel rod driven 35 feet (11 m) to refusal, and
encased in PVC pipe 0.3 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 05/15/1989
Station ID: 8637444 SUPERCEDED DATE: 04/21/2003
Name: BROWNS BAY
VIRGINIA
NOAA Chart: 12238 Latitude: 37° 18.0' N
USGS Quad: ACHILLES Longitude: 76° 24.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7444 C 1982
MONUMENTATION: Survey Disk VM#: 3424
AGENCY: PID:
SETTING CLASSIFICATION: Unspecified Steel Rod
The bench mark is on a 2.0-foot (0.6 m) ridge on the south side of State Highway
651, in line with seven fence posts runing east/west, about 1050 feet (320 m)
from the shore end of the pier, 460 feet (140 m) SSW of Bench Mark BROWNS BAY NO
2 1947, 54.0 feet (16.5 m) SE of the centerline of State Highway 651, 31.6 feet
(9.6 m) south of utility pole #FF91, and 0.2 foot (0.1 m) north of a witness
post. The bench mark is 0.4 foot (0.1 m) below ground level, crimped to an
unspecified steel rod driven an unspecified depth, and encased in a PVC pipe 0.3
foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 05/15/1989
Station ID: 8637444 SUPERCEDED DATE: 04/21/2003
Name: BROWNS BAY
VIRGINIA
NOAA Chart: 12238 Latitude: 37° 18.0' N
USGS Quad: ACHILLES Longitude: 76° 24.2' W
T I D A L D A T U M S
Tidal datums at BROWNS BAY based on:
LENGTH OF SERIES: 80 HWS & 81 LWS
TIME PERIOD: JUNE 8 - JULY 19, 1982
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8637624 GLOUCESTER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (06/19/1982) = 3.90
MEAN HIGHER HIGH WATER (MHHW) = 2.65
MEAN HIGH WATER (MHW) = 2.51
MEAN TIDE LEVEL (MTL) = 1.35
MEAN LOW WATER (MLW) = 0.19
MEAN LOWER LOW WATER (MLLW) = 0.00
LOWEST OBSERVED WATER LEVEL (07/19/1982) = -0.29
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
BROWNS BAY NO 1 1947 5.32 2.81
BROWNS BAY NO 2 1947 5.15 2.64
7444 A 1982 5.63 3.12
7444 B 1982 4.77 2.26
7444 C 1982 4.17 1.66
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 05/15/1989
Station ID: 8637444 SUPERCEDED DATE: 04/21/2003
Name: BROWNS BAY
VIRGINIA
NOAA Chart: 12238 Latitude: 37° 18.0' N
USGS Quad: ACHILLES Longitude: 76° 24.2' 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.