U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8772440 PUBLICATION DATE: 10/20/2011 Name: FREEPORT, DOW BARGE CANAL TX NOAA Chart: 11321 Latitude: 28° 56.9' N ( 28.94830) USGS Quad: FREEPORT Longitude: 95° 18.5' W ( -95.30830) To reach the tidal bench marks from the intersection of Gulf and Velasco Boulevards in Freeport, proceed east on Gulf Boulevard (becomes County Road 229) for 3.2 km (2.0 mi) to the Dow Chemical Company gate where permission to enter and an escort must be obtained, continue on County Road 229 for 1.0 km (0.6 mi) to the west levee road of the Dow Barge Canal, go SE and south on the levee road for 1.0 km (0.6 mi) to the skimmer gate. The bench marks are located on the west side of the canal between the levee and the shoreline. The tide gage is located on the east side of the skimmer gate. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 2440 A 1980 DESIGNATION: 877 2440 A MONUMENTATION: Tidal Station disk VM#: 864 AGENCY: National Ocean Survey (NOS) IDB PID#: AI1121 SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 28° 57.0' N ( 28.94928) LONGITUDE: 95° 18.6' W ( -95.30950) The primary bench mark is a disk located in the Dow Chemical Company's plant area near the skimmer gate, 32 m (105 ft) SW of the SW corner of the steel walkway to the skimmer gate, 26.52 m (87.0 ft) west of the west shoreline of the barge canal, 26.52 m (87.0 ft) south of the centerline of the overhead pipeline over the skimmer gate, and 17 m (56 ft) east of the centerline of the levee road. The bench mark is 9 cm (0.3 ft) below ground level, crimped to a stainless steel rod driven 13.7 m (45 ft) to refusal, and encased in a 4-inch PVC pipe and a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8772440 PUBLICATION DATE: 10/20/2011 Name: FREEPORT, DOW BARGE CANAL TX NOAA Chart: 11321 Latitude: 28° 56.9' N ( 28.94830) USGS Quad: FREEPORT Longitude: 95° 18.5' W ( -95.30830) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 8 1973 DESIGNATION: 877 2441 TIDAL 8 MONUMENTATION: Tidal Station disk VM#: 869 AGENCY: National Ocean Survey (NOS) IDB PID#: AM0028 SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 28° 57.0' N ( 28.94920) LONGITUDE: 95° 18.5' W ( -95.30800) Mark reported destroyed 1/8/02 by CBI. The bench mark is a disk set in the top of a concrete post located 0.3 km (0.2 mi) south of the junction of the levee road and a road south to the Dow Chemical Company skimmer gate, caretaker house and a tide gage, 43.59 m (143.0 ft) west of the west edge of the canal, 29.84 m (97.9 ft) east of the centerline of the levee road, 11.89 m (39.0 ft) west of a fence line, 6.40 m (21.0 ft) east of the center line of a shell road, 1.10 m (3.6 ft) north of power pole RPL 432/227, and 0.91 m (3.0 ft) west of a witness post. BENCH MARK STAMPING: 2440 B 1980 DESIGNATION: 877 2440 B MONUMENTATION: Tidal Station disk VM#: 871 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 28° 57.0' N ( 28.94920) LONGITUDE: 95° 18.5' W ( -95.30800) The bench mark is a disk located in the Dow Chemical Company's plant area near the skimmer gate, 51.82 m (170.0 ft) east of the NE face of styrene tank No. V-1, 21.80 m (71.5 ft) north of a red valve for tanks, 16.37 m (53.7 ft) WNW of a 4-inch steel concrete post, and 6.07 m (19.9 ft) east of the centerline of the levee road. The bench mark is 0.4 foot (0.1 m) below ground level, crimped to a stainless steel rod driven 13.7 m (45 ft) to refusal, and encased in a 4-inch PVC pipe and a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8772440 PUBLICATION DATE: 10/20/2011 Name: FREEPORT, DOW BARGE CANAL TX NOAA Chart: 11321 Latitude: 28° 56.9' N ( 28.94830) USGS Quad: FREEPORT Longitude: 95° 18.5' W ( -95.30830) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 2440 C 1980 DESIGNATION: 877 2440 C MONUMENTATION: Tidal Station disk VM#: 872 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 28° 56.8' N ( 28.94670) LONGITUDE: 95° 18.5' W ( -95.30800) The bench mark is a disk located in the Dow Chemical Company's plant area west of the skimmer gate, 51.82 m (170.0 ft) east of the NE face of Styrene Tank #V-1, 21.80 m (71.5 ft) north of a red valve for the tanks, 16.37 m (53.7 ft) WNW of a 0.10 m (0.3 ft) steel concrete post, and 6.07 m (19.9 ft) east of the centerline of Levee Road. The bench mark is 9 cm (0.3 ft) below ground level, crimped to a stainless steel rod driven 13.7 m (45 ft) to refusal, and encased in a 4-inch PVC pipe and a concrete kickblock. BENCH MARK STAMPING: 2440 D 1980 DESIGNATION: 877 2440 D 1980 MONUMENTATION: Tidal Station disk VM#: 873 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 28° 57.0' N ( 28.94920) LONGITUDE: 95° 18.5' W ( -95.30800) The bench mark is a disk located in the Dow Chemical Company's plant area and west of the skimmer gate, 23.16 m (76.0 ft) south of the SE corner of a chain link fence compound, 23.16 m (76.0 ft) east of the centerline of the levee road, and 17.37 m (57.0 ft) SW of utility pole No. 230 with telephone booth. The bench mark is 9 cm (0.3 ft) below ground level, crimped to a stainless steel rod driven 13.7 m (45 ft) to refusal, and encased in a 4-inch PVC pipe and a concrete kickblock. BENCH MARK STAMPING: DESIGNATION: 877 2440 SRM ALIAS: MONUMENTATION: Bolt VM#: 14017 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Skimmer gate fender OPUS PID: LATITUDE: 28° 57.0' N ( 28.95000) LONGITUDE: 95° 18.5' W ( -95.30830) The bench mark is the head of a galvanized steel lag bolt in the top of the fender on the east side of the skimmer gate.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8772440 PUBLICATION DATE: 10/20/2011 Name: FREEPORT, DOW BARGE CANAL TX NOAA Chart: 11321 Latitude: 28° 56.9' N ( 28.94830) USGS Quad: FREEPORT Longitude: 95° 18.5' W ( -95.30830) T I D A L D A T U M S Tidal datums at FREEPORT, DOW BARGE CANAL based on: LENGTH OF SERIES: 5 YEARS TIME PERIOD: January 1997 - December 2001 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (07/15/2003) = 2.045 MEAN HIGHER HIGH WATER MHHW = 0.536 MEAN HIGH WATER MHW = 0.494 MEAN SEA LEVEL MSL = 0.291 MEAN TIDE LEVEL MTL = 0.289 MEAN LOW WATER MLW = 0.083 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (02/25/1965) = -1.295 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 2440 A 1980 3.640 3.146 NO 8 1973 2.839 2.345 2440 B 1980 5.087 4.593 2440 C 1980 4.002 3.508 2440 D 1980 3.029 2.535 877 2440 SRM 2.646 2.152
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8772440 PUBLICATION DATE: 10/20/2011 Name: FREEPORT, DOW BARGE CANAL TX NOAA Chart: 11321 Latitude: 28° 56.9' N ( 28.94830) USGS Quad: FREEPORT Longitude: 95° 18.5' W ( -95.30830) 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.