U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) To reach the tidal bench marks from the intersection of U.S. Highway 17 and State Highway 501 in Myrtle Beach, proceed NW along State Highway 501 for 1.0 km (0.6 mi) to the bridge over the Intracoastal Waterway. The bench marks are located along the State Highway 501 bridge, on the old railroad highway combination drawbridge adjacent to the highway bridge, and along the approaches to the bridges. The tide gage and staff were located on a wooden fender on the SE side of the combination bridge. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 0854 A 1976 DESIGNATION: 866 0854 A TIDAL MONUMENTATION: Tidal Station disk VM#: 3731 AGENCY: National Ocean Survey (NOS) IDB PID#: DD0822 SETTING CLASSIFICATION: Curb OPUS PID#: DD0822 LATITUDE: 33° 42.9' N ( 33.71500) LONGITUDE: 78° 55.3' W ( -78.92170) The primary bench mark is a disk set in the NE corner of the combination bridge curb, 16.15 m (53.0 ft) north of the center of the road, 11.06 m (36.3 ft) ENE of power pole #20864 with three guy wires and transformers, 3.44 m (11.3 ft) ENE of the center of the ramp, 0.37 m (1.2 ft) WNW of a witness post, and 0.21 m (0.3 ft) west of the south corner of the NE guardrail.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0854 B 1976 DESIGNATION: 866 0854 B TIDAL MONUMENTATION: Tidal Station disk VM#: 3732 AGENCY: National Ocean Survey (NOS) IDB PID#: DD0823 SETTING CLASSIFICATION: Pile cap OPUS PID: LATITUDE: 33° 42.8' N ( 33.71330) LONGITUDE: 78° 55.3' W ( -78.92170) The bench mark is a disk set in a pile cap near the center pier of the bridge over the intracoastal waterway, 7.01 m (23.0 ft) SSE of the centerline of the paved road under the bridge, 5.49 m (18.0 ft) SW of the west corner of the NE bridge pier, 1.86 m (6.1 ft) ENE of the north corner of the center bridge pier, 0.49 m (1.6 ft) SSE of a witness post at the NW edge of the pile cap, and 0.61 m (2.0 ft) above the road. BENCH MARK STAMPING: 0854 D 1976 DESIGNATION: 866 0854 D TIDAL MONUMENTATION: Tidal Station disk VM#: 3733 AGENCY: National Ocean Survey (NOS) IDB PID#: DD0825 SETTING CLASSIFICATION: Copper clad steel rod OPUS PID: LATITUDE: 33° 42.8' N ( 33.71330) LONGITUDE: 78° 55.2' W ( -78.92000) The bench mark is a disk located on the west side of the approach road to the combination bridge, 0.2 km (0.1 mi) SE of the combination drawbridge, 40.75 m (133.7 ft) SW of a fire hydrant, 33.86 m (111.1 ft) west of a sign post for Bridgeport Subdivision in the median of a paved road right, 20.21 m (66.3 ft) SW of the SW most railroad tracks, 11.09 m (36.4 ft) SW of the centerline of the road, and 1.19 m (3.9 ft) NNW of power pole #29862. The bench mark is set level with the ground, crimped to the top of a copper-clad steel rod driven 4.6 m (15 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 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0854 F 1982 DESIGNATION: 866 0854 F TIDAL MONUMENTATION: Tidal Station disk VM#: 3734 AGENCY: National Ocean Survey (NOS) IDB PID#: DD1578 SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 33° 42.7' N ( 33.71170) LONGITUDE: 78° 55.1' W ( -78.91830) The bench mark is a disk located on the east side of the railroad tracks leading to the combination bridge, 33.28 m (109.2 ft) ENE of the centerline of the road leading to the combination bridge, 30.69 m (100.7 ft) NW of a fire hydrant, 12.98 m (42.6 ft) NE of the NE most rail of the railroad tracks, 11.16 m (36.6 ft) NNW of the center of the gravel road, 6.19 m (20.3 ft) WSW of a witness post, 4.82 m (15.8 ft) NE of power pole #51990, and 0.21 m (0.7 ft) west of a witness post. The bench mark is set level with the ground, crimped to the top of a stainless steel rod driven 14.6 m (48 ft) to refusal, and encased in a 5-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0854 G 1982 DESIGNATION: 866 0854 G TIDAL MONUMENTATION: Tidal Station disk VM#: 3735 AGENCY: National Ocean Survey (NOS) IDB PID#: DD1576 SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 33° 42.7' N ( 33.71170) LONGITUDE: 78° 55.1' W ( -78.91830) The bench mark is a disk located on the west side of U.S. Highway 501 in the vicinity of a large cinder block sign WELCOME TO MYRTLE BEACH, 0.5 km (0.3 mi) SE of the south side of the bridge over the Intracoastal Waterway, 17.98 m (59.0 ft) SW of the center of the road, 16.70 m (54.8 ft) south of the west end of a 0.46 m (1.5 ft) concrete pipe culvert beneath the frontage road, 5.21 m (17.1 ft) WNW of a meter pole, 2.01 m (6.6 ft) SW of the west corner of a concrete block planter bed for the Welcome to Myrtle Beach sign, and 1.31 m (4.3 ft) SE of a witness post. The bench mark is set level with the ground, crimped to a stainless steel rod driven 11.0 m (36 ft), encased in a 5-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) T I D A L D A T U M S Tidal datums at COMBINATION BRIDGE based on: LENGTH OF SERIES: 10 MONTHS TIME PERIOD: March 1977 - December 1977 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8661139 BUCKSPORT, WACCAMAW RIVER Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 0.620 MEAN HIGH WATER MHW = 0.573 MEAN TIDE LEVEL MTL = 0.313 MEAN SEA LEVEL MSL = 0.312 North American Vertical Datum NAVD88 = 0.077 MEAN LOW WATER MLW = 0.052 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 0854 A 1976 6.761 6.188 0854 B 1976 6.883 6.310 0854 D 1976 6.499 5.926 0854 F 1982 6.103 5.530 0854 G 1982 6.437 5.864
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 6 of 6 Station ID: 8660854 PUBLICATION DATE: 05/28/2004 Name: COMBINATION BRIDGE SC NOAA Chart: 11535 Latitude: 33° 42.8' N ( 33.71330) USGS Quad: MYRTLE BEACH Longitude: 78° 55.3' W ( -78.92170) 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.