U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) To reach the tidal bench marks from the intersection of Fourth Street (US Highway 101 South) and X Street, proceed north on X Street for 0.3 km (0.2 mi), then turn right onto First Street and proceed east to a fork in the road, then take the left fork and cross over the Northwest Pacific railroad tracks. The bench marks are located between and along First and Fourth Streets. The tide station was located on the south side of the Northwest Pacific railroad bridge over the slough. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 8802 B 1978 DESIGNATION: 941 8802 B TIDAL MONUMENTATION: Tidal Station disk VM#: 8739 AGENCY: National Ocean Survey (NOS) IDB PID#: LV0639 SETTING CLASSIFICATION: Galvanized steel rod OPUS PID: LATITUDE: 40° 48.4' N ( 40.80670) LONGITUDE: 124° 8.6' W (-124.14300) The primary bench mark is a disk located on the south fork at the east end of First Street, 26 m (85 ft) SW of SW corner of Northwest Pacific railroad bridge over the slough, 15.51 m (50.9 ft) SSW of the south rail, 5 m (16 ft) SSW of the Northwest Pacific railroad access road centerline, and 2.99 m (9.8 ft) NNW of a utility pole. The mark is crimped to the top of a galvanized steel rod, driven 11.6 m (38 ft) to refusal, and encased in a 4-inch PVC pipe with concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8802 A 1978 DESIGNATION: 941 8802 A TIDAL MONUMENTATION: Tidal Station disk VM#: 8738 AGENCY: National Ocean Survey (NOS) IDB PID#: LV0640 SETTING CLASSIFICATION: Concrete pier OPUS PID: LATITUDE: 40° 48.4' N ( 40.80670) LONGITUDE: 124° 8.6' W (-124.14300) The bench mark is a disk in set in the top of a concrete pier at the west end of the Northwest Pacific railroad lift span over the slough, 35.51 m (116.5 ft) east of the west end of the bridge, 1.4 m (4.6 ft) south of the near rail, and 2.1 m (6.9 ft) below the rails. BENCH MARK STAMPING: 8802 C 1978 DESIGNATION: 941 8802 C MONUMENTATION: Tidal Station disk VM#: 8740 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Galvanized steel rod OPUS PID: LATITUDE: 40° 48.4' N ( 40.80670) LONGITUDE: 124° 8.5' W (-124.14200) The bench mark is a disk located 31 m (101.7 ft) NW of the NW corner of the Pepsi bottling plant at the NW corner of Second and Y Streets, 11 m (36 ft) SSW of the south rail, 2.5 m (8.2 ft) SSW of centerline of Northwest Pacific railroad access road, and 1 m (3.3 ft) east of a witness post. The mark is crimped to the top of a galvanized steel rod, driven 12.5 m (41 ft) to refusal, and encased in a 4-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8802 D 1978 DESIGNATION: 941 8802 D MONUMENTATION: Tidal Station disk VM#: 8741 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Galvanized steel rod OPUS PID: LATITUDE: 40° 48.4' N ( 40.80670) LONGITUDE: 124° 8.5' W (-124.14200) The bench mark is a disk located 23 m (75 ft) ESE of center of intersection of X and First Streets, and 0.49 m (1.6 ft) south of a steel gate post. The mark is crimped to the top of a galvanized steel rod driven 14 m (46 ft) to refusal, and encased in PVC pipe and concrete.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) T I D A L B E N C H M A R K S BENCH MARK STAMPING: J 75 1931 RESET 1942 DESIGNATION: J 75 RESET MONUMENTATION: Bench Mark disk VM#: 8742 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: LV0287 SETTING CLASSIFICATION: Concrete curb on bridge OPUS PID: LATITUDE: 40° 48.3' N ( 40.80500) LONGITUDE: 124° 8.5' W (-124.14200) The bench mark is a disk set in top of the SE end of the concrete curb of bridge 4-22 over the slough, 1.8 km (1.1 mi) east along U.S. Highway 101 from the post office at Highway Marker 79.78, 4.27 m (14.0 ft) SE of centerline of SE lanes of highway, 1.52 m (5.0 ft) NE of SW end of curb, and 0.15 m (0.5 ft) above the highway. BENCH MARK STAMPING: W 1087 1967 RESET 1969 DESIGNATION: W 1087 RESET MONUMENTATION: Bench Mark disk VM#: 8743 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: LV0289 SETTING CLASSIFICATION: Culvert head wall OPUS PID: LATITUDE: 40° 48.3' N ( 40.80500) LONGITUDE: 124° 7.6' W (-124.12700) The bench mark is a disk set in top of a culvert headwall, 1.1 km (0.7 mi) north of highway bridge over the slough at milepost 80.57, and 13 m (43 ft) east of the white strip for the northbound lanes.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) T I D A L D A T U M S Tidal datums at EUREKA SLOUGH, HUMBOLDT BAY based on: LENGTH OF SERIES: 6 MONTHS TIME PERIOD: April 1978 - September 1978 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9419750 CRESCENT CITY, PACIFIC OCEAN Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 2.253 MEAN HIGH WATER MHW = 2.029 MEAN SEA LEVEL MSL = 1.211 MEAN TIDE LEVEL MTL = 1.210 MEAN LOW WATER MLW = 0.391 North American Vertical Datum NAVD88 = 0.235 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 8802 B 1978 4.077 2.048 8802 A 1978 3.085 1.056 8802 C 1978 3.253 1.224 8802 D 1978 3.456 1.427 J 75 1931 RESET 1942 7.933 5.904 W 1087 1967 RESET 1969 2.045 0.016
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 6 of 6 Station ID: 9418802 PUBLICATION DATE: 05/07/2003 Name: EUREKA SLOUGH, HUMBOLDT BAY CA NOAA Chart: 18622 Latitude: 40° 48.4' N ( 40.80670) USGS Quad: EUREKA Longitude: 124° 8.5' W (-124.14200) 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.