U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) To reach the tidal bench marks from Arcata, exit onto Samoa Boulevard (Highway 255) and proceed west on Samoa Boulevard for 5 km (3 mi) to the bridge over the entrance to Mad River Slough. The bench marks in the vicinity of the RH Emerson and Son Lumberyard, along the railroad tracks. The tide gage was located on a free standing structure 12 m (40 ft) SE of the SW corner of the concrete bridge over the Slough and the staff was on a nearby piling. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: J 735 RESET 1970 DESIGNATION: J 735 RESET MONUMENTATION: Bench Mark disk VM#: 8747 AGENCY: National Ocean Survey (NOS) IDB PID#: LV0346 SETTING CLASSIFICATION: Concrete pier OPUS PID: LATITUDE: 40° 51.9' N ( 40.86500) LONGITUDE: 124° 9.0' W (-124.15000) The primary bench mark is a disk set flush in the top of the SW concrete pier on the west end of the Samoa Boulevard Bridge.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8865 B 1977 DESIGNATION: 941 8865 B MONUMENTATION: Tidal Station disk VM#: 8744 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 40° 51.9' N ( 40.86500) LONGITUDE: 124° 8.9' W (-124.14800) The bench mark is a disk located 37 m (120 ft) ENE of the east gate post of the western gate at R.H. Emerson and Son Lumberyard, 17 m (56 ft) NW of the centerline of Samoa Boulevard, 17 m (55 ft) from the support pole for the fourth telephone pole west of the Samoa Road Bridge over Mad River on the NW side of railroad track, and 8.66 m (28.4 ft) SE of fire hydrant on lumberyard property. The bench mark is crimped to the top of a copper-coated rod driven an unspecified depth to refusal. BENCH MARK STAMPING: 8865 C 1977 DESIGNATION: 941 8865 C MONUMENTATION: Tidal Station disk VM#: 8745 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 40° 51.9' N ( 40.86500) LONGITUDE: 124° 8.9' W (-124.14800) The bench mark is a disk located 0.40 km (0.25 mi) west of the west curb of the Samoa Boulevard Bridge over the slough, 60 m (197 ft) SW of bench mark W 1091 1967, 17 m (55 ft) north from the centerline of Samoa Boulevard, 15 m (49 ft) NW of the crossing signal control box at railroad crossing No. 5G296.7, 8 m (26 ft) south of SW corner of concrete truck scale, 6 m (19 ft) NNE of center of roalroad siding switch and 1 m (4 ft) south of a picket fence. The bench mark is crimped to the top of a copper-coated rod driven an unspecified depth to refusal.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8865 E 1977 DESIGNATION: 941 8865 E MONUMENTATION: Tidal Station disk VM#: 8746 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 40° 51.9' N ( 40.86500) LONGITUDE: 124° 8.9' W (-124.14800) The bench mark is a disk located 100.43 m (329.5 ft) SW of bench mark J 734 RESET 1970, 26 m (85 ft) west of the second telephone pole south of the Samoa Boulevard Bridge over the slough on the NW side of railroad tracks, and 17 (55 ft) NW of the centerline of Samoa Boulevard. The bench mark is crimped to the top of a copper-coated rod driven 19.5 m (64 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: W 1091 1967 DESIGNATION: W 1091 MONUMENTATION: Bench Mark disk VM#: 8748 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: LV0344 SETTING CLASSIFICATION: Highline tower foundation OPUS PID: LATITUDE: 40° 51.9' N ( 40.86420) LONGITUDE: 124° 9.2' W (-124.15300) The bench mark is a disk set in top of the concrete base for the SW steel leg of the first transmission line tower SW of the bridge over the slough, 26 m (84 ft) NW of centerline of road, 12 m (39 ft) NW of the NW rail of the main track for the Northwestern Pacific Railroad, 7 m (24 ft) NE of centerline of gravel road, and 1 m (3 ft) above the road.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) T I D A L D A T U M S Tidal datums at MAD RIVER SLOUGH, ARCATA BAY based on: LENGTH OF SERIES: 4 MONTHS TIME PERIOD: December 1978 - March 1979 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 = 2.326 MEAN HIGH WATER MHW = 2.105 MEAN SEA LEVEL MSL = 1.295 MEAN TIDE LEVEL MTL = 1.258 MEAN LOW WATER MLW = 0.410 North American Vertical Datum NAVD88 = 0.305 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW J 735 RESET 1970 4.845 2.740 8865 B 1977 3.189 1.084 8865 C 1977 3.435 1.330 8865 E 1977 3.398 1.293 W 1091 1967 4.669 2.564
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 6 of 6 Station ID: 9418865 PUBLICATION DATE: 07/02/2003 Name: MAD RIVER SLOUGH, ARCATA BAY CA NOAA Chart: 18622 Latitude: 40° 51.9' N ( 40.86500) USGS Quad: EUREKA Longitude: 124° 8.9' W (-124.14800) 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.