U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8665099 PUBLICATION DATE: 04/21/2003 Name: I-526 BRIDGE, ASHLEY RIVER SC NOAA Chart: 11524 Latitude: 32° 50.2' N ( 32.83670) USGS Quad: JOHNS ISLAND Longitude: 80° 1.3' W ( -80.02170) To reach the tidal bench marks from the intersection of I-26 and I-526 in Charleston County, proceed south on I-526 for 4.7 km (2.9 mi), then go SE on Leeds Avenue for 0.6 km (0.35 mi), then south on a road leading to Duncan's Marina for 0.5 km (0.3 mi). The bench marks are in the vicinity of the marina. The tide gage was located on the south end of the dock closest to the I-526 bridge. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 5099 A 1999 DESIGNATION: 866 5099 A MONUMENTATION: Tidal Station disk VM#: 15999 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Sidewalk OPUS PID: LATITUDE: 32° 50.4' N ( 32.84000) LONGITUDE: 80° 1.5' W ( -80.02500) The primary bench mark is a disk set in a sidewalk running north and south along the concrete boat loading dock leading to finger piers at Duncan's Marina, 8.25 m (27.1 ft) SE of the light pole on the north side of the concrete boat loading dock, 2.56 m (8.4 ft) west of the NW corner of the gas station at the end of the boat loading dock, 1.91 m (6.3 ft) north of the south corner of the boat loading dock, and 0.41 m (1.3 ft) SE of the NW side of the sidewalk.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8665099 PUBLICATION DATE: 04/21/2003 Name: I-526 BRIDGE, ASHLEY RIVER SC NOAA Chart: 11524 Latitude: 32° 50.2' N ( 32.83670) USGS Quad: JOHNS ISLAND Longitude: 80° 1.3' W ( -80.02170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 5099 B 1999 DESIGNATION: 866 5099 B MONUMENTATION: Tidal Station disk VM#: 16000 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Sidewalk OPUS PID: LATITUDE: 32° 50.4' N ( 32.84000) LONGITUDE: 80° 1.5' W ( -80.02500) The bench mark is a disk set in a sidewalk 23.26 m (76.3 ft) SW of the SW side of Duncan's Marina Building SE door opening to the storage exit to the pier, 1.17 m (3.8 ft) SE of a bend in the chain link fence that runs north and south along the sidewalk, 0.56 m (1.8 ft) NW of the SE side of the sidewalk, and 0.52 m (1.7 ft) north of the hand rail. BENCH MARK STAMPING: 5099 C 1999 DESIGNATION: 866 5099 C MONUMENTATION: Tidal Station disk VM#: 16001 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete slab OPUS PID: LATITUDE: 32° 50.4' N ( 32.84000) LONGITUDE: 80° 1.5' W ( -80.02500) The bench mark is a disk located 14.94 m (49.0 ft) SE of the NW corner of a concrete slab in front of Duncan's Marina, 9.50 m (31.1 ft) west of the SW corner of Duncan's Marina, 0.70 m (2.3 ft) NE of the SW corner of a concrete slab in front of Duncan's Marina, and 0.40 m (1.3 ft) NW of the SE corner of a concrete slab in front of Duncan's Marina.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8665099 PUBLICATION DATE: 04/21/2003 Name: I-526 BRIDGE, ASHLEY RIVER SC NOAA Chart: 11524 Latitude: 32° 50.2' N ( 32.83670) USGS Quad: JOHNS ISLAND Longitude: 80° 1.3' W ( -80.02170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 5099 D 1999 DESIGNATION: 866 5099 D MONUMENTATION: Tidal Station disk VM#: 16002 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete slab OPUS PID: LATITUDE: 32° 50.4' N ( 32.84000) LONGITUDE: 80° 1.5' W ( -80.02500) The bench mark is a disk located 18.10 m (59.4 ft) south of the SW corner of Duncan's Marina Building, 16.60 m (54.6 ft) south of the SW corner of an over-hang for a boat display, being the most SE support for the over-hang, 1.70 m (5.7 ft) north of light pole No. 436019, and 0.30 m (1.0 ft) south of the NE corner of the concrete slab supporting Bellsouth phone booth. BENCH MARK STAMPING: 5099 E 1999 DESIGNATION: 866 5099 E MONUMENTATION: Tidal Station disk VM#: 16003 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete slab OPUS PID: LATITUDE: 32° 50.4' N ( 32.84000) LONGITUDE: 80° 1.5' W ( -80.02500) The bench mark is a disk located 15.80 m (51.8 ft) south of the SE corner of the workshop at Duncan's Marina Building, 9.10 m (29.9 ft) NW of the NE corner of Duncan's Marina Building, 4.90 m (16.0 ft) SW of the centerline of the driveway in front of Duncan's Marina, 2.20 m (7.2 ft) east of the center of the double doors leading to the boat show room at Duncan's Marina, 0.32 m (1.05 ft) SW of the sidewalk that runs north and south in front of Duncan's Marina.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8665099 PUBLICATION DATE: 04/21/2003 Name: I-526 BRIDGE, ASHLEY RIVER SC NOAA Chart: 11524 Latitude: 32° 50.2' N ( 32.83670) USGS Quad: JOHNS ISLAND Longitude: 80° 1.3' W ( -80.02170) T I D A L D A T U M S Tidal datums at I-526 BRIDGE, ASHLEY RIVER based on: LENGTH OF SERIES: 6 Months TIME PERIOD: November 1999 - April 2000 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8665530 CHARLESTON, COOPER RIVER ENTRANCE Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 1.899 MEAN HIGH WATER MHW = 1.796 MEAN SEA LEVEL MSL = 1.003 MEAN TIDE LEVEL MTL = 0.930 MEAN LOW WATER MLW = 0.064 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 5099 A 1999 2.443 0.647 5099 B 1999 2.972 1.176 5099 C 1999 3.075 1.279 5099 D 1999 3.217 1.421 5099 E 1999 3.078 1.282
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8665099 PUBLICATION DATE: 04/21/2003 Name: I-526 BRIDGE, ASHLEY RIVER SC NOAA Chart: 11524 Latitude: 32° 50.2' N ( 32.83670) USGS Quad: JOHNS ISLAND Longitude: 80° 1.3' W ( -80.02170) 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.