U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                                                
Station ID: 8571773                         PUBLICATION DATE:  06/30/2010
Name:       VIENNA, NANICOKE RIVER                            
            MD
NOAA Chart: 12261                           Latitude:   38° 29.0' N (  38.48333)
USGS Quad:  MARDELA SPRINGS                 Longitude:  75° 49.1' W ( -75.81833)


To reach the tidal bench marks from Cambridge, MD. travel East on Route 50
approximately 13 miles (20.9 KM) the Route 331exit. Head south for approximately
0.1 miles (.16 KM) and turn east onto Chapel of Ease Road.  Follow road for
approximately 0.2 miles (0.3 KM) to entrance of NRG Vienna power plant. Continue
through gate approximately 0.2 miles (0.3 KM) to power plant facility.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  X5 RESET 1964
                         DESIGNATION:          857 1773 X5 RESET

MONUMENTATION:           Tidal Station disk                    VM#:        17826
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  HU0640
SETTING CLASSIFICATION:  Concrete foundation                   OPUS PID:        
LATITUDE:   38° 29.1' N (  38.48530)          LONGITUDE:  75° 49.3' W ( -75.82130)


The benchmark is set in the south corner of the concrete foundation of the south
western metal leg of the more easterly of two towers whose power lines cross the
Nanticoke River, 17.10 m (56.1 ft) SE from drainage valve 007, 1.25 m (4.10 ft)
south of the south leg of the tower, 0.49 m (1.6 ft) north of the south corner
of the foundation, and 0.61 m (2.0 ft) above ground level.  

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 8571773                         PUBLICATION DATE:  06/30/2010
Name:       VIENNA, NANICOKE RIVER                            
            MD
NOAA Chart: 12261                           Latitude:   38° 29.0' N (  38.48333)
USGS Quad:  MARDELA SPRINGS                 Longitude:  75° 49.1' W ( -75.81833)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  1773 A 2005
                         DESIGNATION:          857 1773 A

MONUMENTATION:           Tidal Station disk                    VM#:        17827
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete footing                      OPUS PID:        
LATITUDE:   38° 29.1' N (  38.48540)          LONGITUDE:  75° 49.3' W ( -75.82150)


The bench mark is set into the concrete footing of a light pole, located at the
southern end of the property, along the Nanticoke River, north of a small wooden
pier, 28.59 m (93.8 ft) east of the SE corner of a metal tower with 2 cameras on
top, 19.11 m (62.7 ft) NE of a single yellow bollard, 11.00 m (36.1 ft) SW of 
the south westerly of the 2 yellow bollards, 0.39 m (1.28 ft) west of center
light pole, and 0.24 m (0.79 ft) above the ground.  



                         BENCH MARK STAMPING:  1773 B 2005
                         DESIGNATION:          857 1773 B

MONUMENTATION:           Tidal Station disk                    VM#:        17828
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete bulkhead                     OPUS PID:        
LATITUDE:   38° 29.1' N (  38.48580)          LONGITUDE:  75° 49.3' W ( -75.82090)


The bench mark a disk set into the concrete bulkhead running the length of the
Nanticoke River, 40.94 m (134.13 ft) south of a single 62 cm diameter yellow
bollard, 11.97 m (39.27 ft) east of the north corner of a blue 2-story concrete
block building., and 0.80 m (2.62 ft) west from riverside face of concrete
bulkhead.  

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 8571773                         PUBLICATION DATE:  06/30/2010
Name:       VIENNA, NANICOKE RIVER                            
            MD
NOAA Chart: 12261                           Latitude:   38° 29.0' N (  38.48333)
USGS Quad:  MARDELA SPRINGS                 Longitude:  75° 49.1' W ( -75.81833)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  1773 C 2005
                         DESIGNATION:          857 1773 C

MONUMENTATION:           Tidal Station disk                    VM#:        17829
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete bulkhead                     OPUS PID:        
LATITUDE:   38° 29.2' N (  38.48620)          LONGITUDE:  75° 49.2' W ( -75.82040)


The benchmark is set into the concrete bulkhead along the Nanticoke River, 13.83
m (45.37 ft) east of the centerline from a single yellow bollard, 5.91 m (19.4
ft) south from the north corner of the support leg of a steel shelter, and 0.75
m (2.46 ft) north west of riverside face of concrete bulkhead.



                         BENCH MARK STAMPING:  1773 D 2005
                         DESIGNATION:          857 1773 D

MONUMENTATION:           Tidal Station disk                    VM#:        17830
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete foundation                   OPUS PID:        
LATITUDE:   38° 29.2' N (  38.48690)          LONGITUDE:  75° 49.2' W ( -75.82020)


The bench mark is set into the concrete foundation used to mount a holding tank
for a caustic solution, 18.52 m (60.76 ft) WNW of riverside face of concrete
bulkhead, 16.09 m (52.8 ft) SW from the NE corner of the Clearwell Building, 
and 15.60 m (51.18 ft) N from the NE corner of the Office Building .3m (.98 ft)
above ground.  

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 8571773                         PUBLICATION DATE:  06/30/2010
Name:       VIENNA, NANICOKE RIVER                            
            MD
NOAA Chart: 12261                           Latitude:   38° 29.0' N (  38.48333)
USGS Quad:  MARDELA SPRINGS                 Longitude:  75° 49.1' W ( -75.81833)


                            T I D A L   D A T U M S 


Tidal datums at VIENNA, NANICOKE RIVER based on:

     LENGTH OF SERIES:      4 YEARS
     TIME PERIOD:           September 2005 - August 2009
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8571892 CAMBRIDGE, CHOPTANK RIVER


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     HIGHEST OBSERVED WATER LEVEL (05/12/2008)         =  1.312
     MEAN HIGHER HIGH WATER                     MHHW   =  0.750
     MEAN HIGH WATER                            MHW    =  0.702
     MEAN SEA LEVEL                             MSL    =  0.406
     MEAN TIDE LEVEL                            MTL    =  0.379
     MEAN LOW WATER                             MLW    =  0.055
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (01/03/2008)         = -0.617

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     X5 RESET 1964                               3.473    2.771
     1773 A 2005                                 2.905    2.203
     1773 B 2005                                 2.259    1.557
     1773 C 2005                                 2.252    1.550
     1773 D 2005                                 2.785    2.083


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                                                
Station ID: 8571773                         PUBLICATION DATE:  06/30/2010
Name:       VIENNA, NANICOKE RIVER                            
            MD
NOAA Chart: 12261                           Latitude:   38° 29.0' N (  38.48333)
USGS Quad:  MARDELA SPRINGS                 Longitude:  75° 49.1' W ( -75.81833)


                             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.