U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8673381 PUBLICATION DATE: 03/09/2004 Name: HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA NOAA Chart: 11511 Latitude: 31° 41.7' N ( 31.69500) USGS Quad: SEABROOK Longitude: 81° 16.3' W ( -81.27170) To reach the tidal bench marks from the intersection of Interstate Highway 95 and State Road 38, proceed east on State Road 38 for 13.2 km (8.2 mi) to the road leading to Colonels Island Marina, then turn right and proceed south on the road leading to Colonels Island Marina for 2.6 km (1.6 mi) to the marina. The bench marks are located on the marina grounds. The tide gage and staff were located on a pier on the NW corner of the marina. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 3381 A 1977 DESIGNATION: 867 3381 A TIDAL MONUMENTATION: Tidal Station disk VM#: 4760 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Unspecified deep rod OPUS PID: LATITUDE: 31° 41.7' N ( 31.69500) LONGITUDE: 81° 16.3' W ( -81.27170) The primary bench mark is a disk located near the NW corner of the southernmost boat house, 16.70 m (54.8 ft) NE of a group of four oak trees east of Timmons River, and 10.15 m (33.3 ft) north of the NE corner of a small wooden building. The bench mark is crimped to the top of an unspecified rod driven 19.5 m (64 ft) to refusal and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8673381 PUBLICATION DATE: 03/09/2004 Name: HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA NOAA Chart: 11511 Latitude: 31° 41.7' N ( 31.69500) USGS Quad: SEABROOK Longitude: 81° 16.3' W ( -81.27170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3381 B 1977 DESIGNATION: 867 3381 B TIDAL MONUMENTATION: Tidal Station disk VM#: 4761 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Unspecified deep rod OPUS PID: LATITUDE: 31° 41.7' N ( 31.69500) LONGITUDE: 81° 16.3' W ( -81.27170) The bench mark is a disk located near the SE corner of the northernmost boat house, 86 m (283 ft) east of bench mark 3381 A 1977, and 8.99 m (29.5 ft) west of the centerline of the road leading to the marina. The bench mark is crimped to the top of an unspecified rod driven 1.8 m (6 ft) to refusal and encased in a PVC pipe and concrete kickblock. BENCH MARK STAMPING: 3381 C 1977 DESIGNATION: 867 3381 C TIDAL MONUMENTATION: Tidal Station disk VM#: 4762 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Unspecified deep rod OPUS PID: LATITUDE: 31° 41.7' N ( 31.69500) LONGITUDE: 81° 16.3' W ( -81.27170) The bench mark is a disk located NE of a cinder block cottage, 52.82 m (173.3 ft) south of bench mark 3381 B 1977, 17.77 m (58.3 ft) NE of the NE corner of the cinder block cottage, and 9.69 m (31.8 ft) west of the centerline of the road leading to the marina. The bench mark is set 6 cm (0.2 ft) above ground level, crimped to the top of an unspecified rod driven 4.9 m (16 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8673381 PUBLICATION DATE: 03/09/2004 Name: HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA NOAA Chart: 11511 Latitude: 31° 41.7' N ( 31.69500) USGS Quad: SEABROOK Longitude: 81° 16.3' W ( -81.27170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3381 D 1977 DESIGNATION: 867 3381 D TIDAL MONUMENTATION: Tidal Station disk VM#: 4763 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Unspecified deep rod OPUS PID: LATITUDE: 31° 41.7' N ( 31.69500) LONGITUDE: 81° 16.3' W ( -81.27170) The bench mark is a disk located south of a cinder block cottage, 30.69 m (100.7 ft) SSW of bench mark 3381 C 1977, 16.92 m (55.5 ft) west of the centerline of the road leading to the marina, and 5.91 m (19.4 ft) ESE of the SE corner of the cinder block cottage. The bench mark is set 6 cm (0.2 ft) above ground level, crimped to the top of an unspecified rod driven 4.9 m (16 ft) to refusal, and encased in a PVC pipe and a concrete kickblock. BENCH MARK STAMPING: 3381 E 1977 DESIGNATION: 867 3381 E TIDAL MONUMENTATION: Tidal Station disk VM#: 4764 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Unspecified deep rod OPUS PID: LATITUDE: 31° 41.7' N ( 31.69500) LONGITUDE: 81° 16.3' W ( -81.27170) The bench mark is a disk located ESE of the marina store, 48 m (158 ft) west of bench mark 3381 D 1977, and 16.34 m (53.6 ft) ESE of the SE corner of the marina store. The bench mark is crimped to the top of an unspecified rod driven 2.4 m (8 ft) to refusal, and encased in a PVC pipe and a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8673381 PUBLICATION DATE: 03/09/2004 Name: HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA NOAA Chart: 11511 Latitude: 31° 41.7' N ( 31.69500) USGS Quad: SEABROOK Longitude: 81° 16.3' W ( -81.27170) T I D A L D A T U M S Tidal datums at HALFMOON, COLONELS ISLAND, TIMMONS RIVER based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: May 1977 - May 1977 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8720030 FERNANDINA BEACH, AMELIA RIVER Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 2.422 MEAN HIGH WATER MHW = 2.311 MEAN SEA LEVEL MSL = 1.338 MEAN TIDE LEVEL MTL = 1.190 MEAN LOW WATER MLW = 0.069 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 3381 A 1977 4.815 2.504 3381 B 1977 5.615 3.304 3381 C 1977 5.856 3.545 3381 D 1977 5.806 3.495 3381 E 1977 5.556 3.245
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8673381 PUBLICATION DATE: 03/09/2004 Name: HALFMOON, COLONELS ISLAND, TIMMONS RIVER GA NOAA Chart: 11511 Latitude: 31° 41.7' N ( 31.69500) USGS Quad: SEABROOK Longitude: 81° 16.3' W ( -81.27170) 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.