DC WRRC REPORT NO. 156
DEVELOPMENT OF A GROUNDWATER CONTOUR MAP
FOR THE WATER TABLE AQUIFER IN THE ATLANTIC
COASTAL PLAIN DEPOSITS OF WASHINGTON, DC
May 1995
D.C. WATER RESOURCES RESEARCH CENTE
University of the District of Columbia 4200
Connecticut Ave, NW Building 50, MB 8004
Washington, DC 20008
TABLE OF CONTENTS
INTRODUCTION ………................................................... 1
MATERIALS and METHODS .......................................….19
RESULTS
........................................................ 35
DISCUSSIONS
…...................................................... 43
REFERENCES
APPENDICES
LIST OF TABLES
Table 1 - Local Stratigraphy ..........................................……… 10
Table 2 - Summary of Model Parameters ................................... 35
LIST OF FIGURES
Figure 1 - Fall Line between Coastal Plain and Piedmont Provinces ........………...... 3
Figure 2 - Limits of Research Area
.................................………………………...... 5
Figure 3 - General Geology Map of Washington, DC ....................……………........ 12
Figure 4 - Geologic Cross-Section through Washington, DC ............…………......... 13
Figure 5 - Surface Water Datapoint Locations and Database Designations ..……….. 21
Figure 6 - Groundwater Monitoring Well Locations and Database Designations …... 24
Figure 6A - Groundwater Monitoring Well Locations and Database Designations .... 25
Figure 7 - Seasonal Fluctuation in Groundwater Levels .......………………............... 26
Figure 8 - Soil Test Boring Locations and Database Designations ............………….. 28
Figure 8A - Soil Test Boring Locations and Database Designation .....……………… 29
Figure 9 - Kriging Standard Deviation Contour Map ......................………………….. 30
Figure 10 - Typical Semi-Variogram ..........................…………………………........... 32
Figure 11 - Model 1 Semi-Variogram ..…………………………................................. 36
Figure 12 - Model 2 Semi-Variogram ...................…………………………................ 37
Figure 13 - Model 3 Semi-Variogram ..................…………………………................. 38
Figure 14 - Model 4 Semi-Variogram ........................…………………………........... 39
Figure 15 - Perched Water Table Contour Map of Downtown Washington, DC ..….... 41
Sheet 1 - Groundwater Table Contour Map of the Atlantic Coastal Plain Aquifer (map
pocket)
INTRODUCTION
The Anacostia River Basin in Washington, DC has been identified as one of the
most polluted waterways in the Washington metropolitan area (Schneider et al., 1993d).
The river water quality is generally viewed as poor and various methods to improve the
river water quality are being investigated. The interaction between the quality of the
river's tributary streams and storm drains has been recognized as a major contributor to
the river water quality. The ability to evaluate the quantitative impacts of these discharge
sources requires an understanding of the groundwater flow system in the area. Although
significant research has been published on the general groundwater flow characteristics
on the major aquifers in the region, prior to 1993 no significant research had been
completed on the characteristics of the uppermost water table aquifer in this area.
In 1993, research on the characteristics of groundwater flow in the water table
aquifer that feeds the Anacostia River Basin in Washington, DC was undertaken by
Matheson, et al. (1994). The research was sponsored by the DC Water Resources
Research Center (WRRC) under a grant from the United States Geologic Survey
(USGS). The objective of Matheson et al.'s research was to develop a groundwater
contour map that could be used as the basis for evaluating the general groundwater flow
direction and interaction with surface waters.
The District of Columbia is an urbanized region that has many human-made or
influenced features that have significantly impacted both the surface and subsurface
hydrology. Among these are the construction of a storm drain system in the early 20th
century to capture and divert the flow from some of the major surface streams. In
addition, many of the stream channels were filled, with or without provision for drainage.
The construction of buildings with basement sump pumps and paved surface
areas has also significantly impacted the surface hydrology, groundwater recharge and
general subdrainage basin hydrology throughout the area. Finally, the geology of the
area is variable and further complicates the evaluation. A general geology map and
cross section through the Washington DC area are presented in Figure 1. Greater detail
on the geology and geohydrology of the research area will be presented in later
sections of this report. A glossary of geologic terms is presented in Appendix A.
A groundwater contour map of a portion of the Anacostia River basin within
the Coastal Plain was generated during Matheson et al.'s (1994) research. This map
generally indicated that four recharge areas are located in the study area. Groundwater
flow patterns in the surficial aquifer inferred from the contour map suggested that
local flow systems corresponded to the surface water drainage basins of the Potomac
River, the Anacostia River with its tributaries, and Oxon Run. Some differences were
encountered in the downtown area, where the sewering of Tiber Creek has resulted in
a rerouting of surface water runoff from the Potomac River to the Anacostia River.
Groundwater, however, still appeared to follow the natural topographic gradient and
discharges directly to the Potomac River. Matheson et al.'s research also suggested the
possible presence of a perched water table in the Lincoln Park area in downtown
Washington DC.
Piedmont crystalline
rocks with saprolite
cover
Fall Line
Figure 1 - Fall Line between Coastal Plain & Piedmont Provinces
This research presents the results of research undertaken to expand on the
earlier research of Matheson et al. (1994). The research area is shown on Figure 2.
Groundwater data was collected from groundwater monitoring wells and soil test
borings as well as perennial surface water bodies in the research area. The data was
evaluated using a computerized geostatistical analysis program. The geostatistical
program generated semivariograms which were used in the development of a map of
the predicted groundwater levels. A semi-variogram is a plot of the variance of paired
sample measurements as a function of the distance between samples and provides a
means of quantifying the commonly observed relationship that samples close together
will tend to have more similar values than samples far apart. The groundwater contour
map of downtown Washington DC, developed during the course of this research was
combined with the contour map constructed during the previous study. Modifications
to the previous map based on additional data collected during this investigation were
completed. The groundwater data collected during the course of this research was
evaluated using a geostatistical computer program This composite map represents a
contour map of the water table aquifer of the Atlantic Coastal Plain Deposits of
Washington, DC. The contribution of this research is the development of the
composite contour map that can be used for assessing urbanization impacts on the
groundwater flow and provide insights into the interaction between surface water
contamination and groundwater contamination.
Figure 2 - Limits of Research Area
Research Objectives
The first objective of the research was to develop a groundwater contour map that
could be used as the basis for evaluating general groundwater flow directions. The contour
map developed during the course of the study was to be combined with a groundwater
contour map of the Anacostia River Basin developed by Matheson et al. (1994). The contour
map will also be used to evaluate the effects of urbanization on groundwater flow paths by
examining the historical Tiber Creek flow paths and the current flow paths. The approximate
location of Tiber Creek is shown on Figure 2. The second objective of the research was to
estimate the location and extent of the perched table aquifer in the downtown region of
Washington, DC. The final objective of the research was to use geostatistical evaluation
techniques to assess the reliability of the predicted groundwater contours. This portion of the
research would assess the distribution and density of the data used to generate the
groundwater contour map and identify areas requiring additional data to measure the
reliability of the estimated groundwater contours.
In order to accomplish the research objectives, the following scope of work was
completed:
- Review available data on regional geology, geohydrology, and hydrology of the study area
and surrounding region,
- Determine sources of available data for documentation of groundwater and groundwater
related surface water levels. This included existing as well as abandoned groundwater
monitoring wells for environmental investigations and construction of the Washington Metro
system. In areas of limited well data, soil test boring data were located to estimate approximate
groundwater elevations,
- Collate groundwater and surface water data in combination with geologic and historical
stream channel information,
- Plot groundwater elevations at the location of the measurement point on a base map,
- Contour groundwater elevation data on 20-foot intervals,
- Perform geostatistical evaluations using semi-variograms and kriging to develop an
assessment of reliability of the contour data,
- Outline limitations of the research and recommend areas of future research needs.
This report has been prepared using data collected by the author as well as data
collected by others. Although the data collected by others was examined and used only
when deemed reasonable, the author makes no warranty as to the accuracy of the data
collected by others. It should be understood that the groundwater levels presented are
based on widely spaced monitoring points that were measured at different times. These
conditions can change due to seasonal and human-induced effects and should be taken
only as an indication of the general groundwater levels and flow directions in this
region.
Geologic and Hydrologic Setting
Physiographic and Climatic Conditions
The District of Columbia straddles the boundary between the Atlantic Coastal
Plain physiographic province and the Piedmont physiographic province. This boundary
is called the Fall Line, which runs in a north-south direction through Washington, DC
along Rock Creek Park. The general location of these provinces are shown on Figure 1.
The topography of the Washington DC area displays moderate relief (Johnston, 1978).
The topographic high
point in the region is located in the Piedmont province near Tysons Corners; the lowest
point is at sea level and the surface of the Potomac River near Haynes Point. There is no
discernible change in the topography at the boundary between the Piedmont and Coastal
Plain provinces.
The Washington, DC area has a humid, continental climate marked by seasonal
temperature changes (USDA, 1976). In general, the summers are warm and humid while
the winters are mild to cold. The coldest weather typically occurs in January and
February with average low temperatures in the upper twenties and average high
temperatures in the middle forties. The warmest weather generally occurs in July when
the average daily high temperatures are in the upper eighties.
Precipitation is well distributed throughout the year and averages about 41
inches per year. Of the total annual precipitation, about 21 inches, or approximately 54
percent usually falls during the period of April through September. The average annual
snowfall is about 20 inches, however, the amount of snowfall varies greatly from storm
to storm. Snow accumulation from a typical severe storm is around 10 inches, which
will typically melt in two or three days (Johnston, 1978).
Geologic Setting
The research area is located in the Atlantic Coastal Plain physiographic
province. This province is characterized by alternating layers of unconsolidated
sedimentary sands, silts, and clays. These materials were derived from erosion of
mountains once present to the west of the research area in the Piedmont physiographic
province. The study was restricted to only
those areas underlain by Coastal Plain or deep alluvial/fluvial sediments. This
eliminated the areas underlain by residual soils and in-place bedrock.
The Coastal Plain deposits present in the region slope gradually to the southeast and
change from near zero thickness at the Fall Line to about 4,000 feet in thickness along
the eastern shore of Maryland and Virginia (Papadopulos et al., 1974). At the
southeastern border of the District, the deposits reach a thickness of approximately 800
feet. The Coastal Plain deposits are underlain by the metamorphic and igneous rocks.
The general geology of the research area has been defined by Johnston (1978). Figure 3
presents a generalized geologic map developed by Johnston that encompasses the
research area. Based on this map and recent deep wells drilled in the area of the
National Arboretum (Schnabel Engineering Associates, 1992) and at Fort Dupont
(Schneider et al., 1993a), the study area geology consists predominately of Pleistocene
Potomac Group deposits from near the ground surface to the bedrock contact. In and
around existing and buried stream channels, alluvial deposits of the Quaternary age are
present. Man-placed fill is present in many areas as a result of urbanization activities.
Some isolated outcrops of other Pleistocene deposits are also present.
Table 1 presents the major geologic units of the District's Coastal Plain, which are (from
youngest to oldest) alluvium and artificial fill (Qal), river terrace deposits (Qt), upland
gravel and sand (Tug), and the Potomac Group. Figure 4 present a generalized cross
section through the area.
Table 1 Local Stratigraphy
Holocene to Pliocene Epoch
Miocene Epoch
Paleocene Epoch
Lower Cretaceasous Period
Fill
Aquifer Alluvium
River Terrace
Deposits Upland
Gravel and Sand
Calvert Formation
(Chesapeake Group)
Aquia Formation
Aquifer (Pamunkey Group)
Monmouth Formation
Aquifer
Potomac Group
Patapsco/Arundel
Patuxent
Precambria Era
Kensington Gneiss
Lower Paleozoic Era
Georgetown Mafrc
Surficial Coastal Plain
I Perched
I Perched
Large areas of artificial fill occur primarily along stream channels and adjacent to Potomac and
Anacostia Rivers. These often overlay alluvial deposits that consist of gravel, sand, silt, and clay of the
lowest stream terraces and stream beds. The fill and alluvium deposits vary in thickness from less than 1foot to 25 feet or more. A series of flat-topped terraces at several characteristic elevations have been
identified in the Washington area. These Pleistocene river terraces consist of a mixture of silty and sandy
clays with sands and gravelly sands, interlayered and lensed in a complex pattern (Johnston, 1978).
Isolated outcrops of the Pleistocene Calvert Formation (Tc), the Aquia Formation (Ta) and the
Monmouth Formation (Km) are present in the District of Columbia. The Calvert Formation consists of
very fine sand mixed with clay and is typically between 20 to 80 feet
in thickness. The Monmouth Formation rarely exceeds 50 feet and consists of dark micaceous
sand.
The Potomac Group consists of two facies. These are a clay and silt facies (Kpe) and the
sand and gravel facies (Kps). The sand and gravel facies is part of the Patuxent aquifer
that provides drinking water to parts of Maryland and Virginia. This unit overlies
crystalline rock and consists of gravel and sand with occasional sandy clay lenses. The
clay and silt facies is made up of silty clay with interbedded irregular sand and gravel
lenses. In some literature these units are called the Anne Arundel Clay and Patapsco
Formation. The recharge area for the Patuxent aquifer crops out throughout much of the
study area.
Hydrogeologic Setting
General Coastal Plain Hydrogeology
In general, the Coastal Plain groundwater regime consists of complex sequences of
unconsolidated interbedded (alternating and interfingering) sand, silt, and clay which were
deposited in variety of sedimentary environments related to periods of sediment input and
sea level changes. The sorting and grain size of sediments, as well as the thickness and
distribution of sand and clay bodies, were determined by the environment of deposition
and have a profound influence on aquifer characteristics. Decreasing grain size or degree
of sorting results in decreasing hydraulic conductivity values. A thick aquifer with low
hydraulic conductivity may have a lower transmissivity than a thin aquifer with high
hydraulic conductivity. Hydraulic conductivity is the rate of flow of water through a cross
section of one square foot, under a unit hydraulic gradient. Transmissivity is the rate of
flow through a vertical section one foot wide and extending the full saturated height of the
aquifer, under
a hydraulic gradient of one. Wells that yield moderate to large quantities of water can be
constructed almost anywhere within the region (Johnston, 1964).
The alternating sequence of sands, silts, and clays creates a complex hydrogeologic
system. Many sands are confined between layers of silts and clays creating an extensive
series of artesian aquifers. The general direction of groundwater flow in these aquifers is
down gradient to the east. The sands that form the aquifers are exposed at the surface prior
to being confined by an overlying aquitard. The surface exposures of these sands represent
the recharge areas for the aquifers. Leakage into and out of the aquifers through the
confining units is also an important source of water for these units, especially in the areas
where pumping wells have significantly drawn down the potentiometric surface. The
potentiometric surface of the aquifers is a function of the elevation of the recharge area, the
hydraulic conductivity of the aquifer, the local pumping of the aquifer, and the leakage into
and out of the aquifer. The potentiometric surface represents the static head and is defined
by the levels to which water will rise in tightly cased wells. Where the head varies
appreciable with depth in an aquifer, a potentiometric surface is meaningful only if it
describes the static head along a particular specified surface or stratum in that aquifer.
The Potomac Group Aquifer
The primary economic water-producing aquifer in this area is the Patuxent aquifer
which is part of the Potomac group. The transmissivity of the aquifer is typically between
6,000 to 10,000 gallons per day per foot (Mueser el al., 1967, Schnabel Engineering
Associates, 1992, Schneider et al., 1993x). The Patuxent aquifer is overlain by the
15
undifferentiated Potomac Group and Arundel Formation which is an alternating sequence of clay
and sand. This combined unit represents a confining unit for the Patuxent aquifer. The sands in the
confining unit are typically thin and do not produce sufficient water to be locally considered an
aquifer. Both the Patuxent aquifer and the Potomac/Arundel confining unit are exposed in the
research area. As can be seen from Figures 3 and 4, the Potomac Group aquifer recharge area is
present in the area immediately east of the Fall Line.
As one progresses east from the Fall Line, the Potomac Group confining unit is exposed at the
ground surface where the Patuxent aquifer dips beneath this aquitard. This creates a potentiometric
surface in the Patuxent aquifer that exceeds the ground surface elevation in some areas. For
example, a flowing artesian well is present at the National Arboretum, where the potentiometric
surface is up to 10 feet above the ground surface. Based on the groundwater levels measured at the
National Arboretum and at Fort Dupont, across the Anacostia River, it is estimated that the
potentiometric surface of the Patuxent aquifer is between 20 to 30 feet above the Anacostia River
elevation.
Surfieial Aquifer
The unconfined aquifer system in the region is developed in the surficially exposed materials. It
represents a continuous water table that crosses the geologic boundaries between the various
aquifers, confining and alluvial units within the area. Although the groundwater flow velocity
will be controlled by the lithology of each of these units, the groundwater flow direction and
gradient will be controlled by the location of current or past
surface drainages, the frequency and magnitude of local precipitation events, the infiltration rate
and capacity of the soils.
The hydraulic conductivity of the sands and gravelly sands in the investigation area
average in the 5 to 10 ft/day range (Mueser et al., 1967). Cohesionless single-size sands in the
alluvium and terraces can have a higher conductance, with values reported in the 150 ft/day to
700 ft/day range. During the Ground Water Resource Assessment Study conducted by the DC
WRRC for the District of Columbia (Schneider et al., 1993a,b), wells were installed at four
locations within the surficial aquifer. Transmissivities ranged from 195 to 3,000 gpd/ft,
indicating locally productive layers. The clays and silts in the study area have hydraulic
conductivities from 0.1 to 0.001 ft/day.
Perched Aquifer
A perched aquifer is defined as an aquifer that occurs as a layer of saturated soil above
the region's main water table. According to DC WRRC's Groundwater Resource Assessment
Study Final Report (1993), perched tables have tentatively been identified in the downtown area
as well as along the southeastern border of the District. The exact location and extent of these
perched aquifers is not known. Previous research by others (O'Conner and Kirkland, 1991)
suggests that groundwater lenses associated with the Quaternary terraces may be classified as
perched water tables, even though these perched water tables do not match the textbook
definition of a perched water table as the underlying aquifers are mostly confined instead of
unconfined. O'Conner and Kirkland (1991) suggest that urbanization dewatering may have
created these perched water tables where a contiguous water table aquifer may previously have
exsited. Matheson et al.’s 1994 study suggested that a perched aquifer may be present in the
Lincoln Park area of Washington DC.
17
METHODS AND MATERIALS
Groundwater data was collected from several sources and combined with the
data collected during the previous WRRC study (Matheson, et al., 1994). The data was
analyzed using a geostatistical computer program and elevation contours developed
using a kriging contouring procedure. The data was used to develop a groundwater
contour map of the Atlantic Coastal Plain deposits in Washington, DC.
Data Sources
To estimate the groundwater contours of the Atlantic Coastal Plain deposit aquifers,
several types of data were used. These included: 1) surface water bodies, 2) groundwater
monitoring wells, and 3) soil test borings.
Surface Water Bodies
An inherent assumption in this research is that perennial surface water bodies, such
as streams, lakes, ponds, or the Anacostia River, are discharge or recharge points for
unconfined groundwater flow. Thus, these locations represent approximate points on the
water table surface.
The location of the surface water bodies were identified on United States Geological
Survey (USGS, 1965) 7.5 minute topographic maps of the Washington East, Washington
West, Anacostia, and Alexandria Quadrangles. These maps were produced between 1965
and 1986. Sheet 1 presents the composite topographic map used in this investigation that
was developed by combining portions of the four USGS Quadrangle sheets cited above. The
19
map shows the location of the major perennial, intermittent, and ephemeral stream
channels in the research area.
The elevation of lakes, ponds, and reservoirs in the research area was also noted
on the USGS maps. The elevation of water in these features was documented by
contacting the organization that controls the water body. Where the controlling
organization did not know the water elevation, 1-inch equals 200 feet topographic maps
from the District of Columbia Department of Public Works (DC DPW, 1988), were
reviewed and the elevation estimated. These maps were also reviewed to better estimate
the elevations of the various perennial streams within the research area.
The location of each surface water location was identified on the base map by
assigning it a control number and by using a digitizer to assign it a coordinate
representing its location. The coordinate system used is based on the Universal
Transverse Mercator (NAD 83, Zone 18) coordinate system. The locations where
perennial stream channels crossed the 10-foot contour interval on the USGS maps were
digitized to represent the location and elevation of water within the stream. These
coordinates were transferred into a Geographic Information System for later use in the
groundwater contouring. Using this procedure, a total of 244 surface water points were
identified and used in this research. The locations of the surface water sites used in this
research are presented on Figure 5. Each surface water location and the groundwater
elevation is presented in Appendix B.
Figure 5 - Surface Water Data Point Locations and Database Designations
21
Groundwater Monitoring Wells
Groundwater monitoring wells have been installed in the District of Columbia and
vicinity for a variety of purposes. The majority of these wells are environmental
monitoring wells associated with site characterization for underground petroleum tank
wells were installed during the construction of the Washington Metropolitan Area Transit
Authority (WMATA) subway system and by the District of Columbia Department of
Environmental Services as part of an investigation of groundwater inflows into the city's storm
sewer system (DC DES, 1983). Schnabel Engineering Associates (SEA) has also installed
numerous temporary groundwater monitoring wells during geotechnical investigations in the
District of Columbia. Due to liability concerns, the majority of the wells installed by DCERA,,
WMATA, and SEA were abandoned and grouted upon completion of the work. As a result, this
project had to rely on the results of past monitoring to provide approximate groundwater levels.
The location of monitoring well sites within the District of Columbia were identified by
searching the files of the DCERA, WMATA, DCDPW, and SEA. At many of the sites,
particularly the DCERA environmental well sites, more than one monitoring well was present
within a relatively close proximity. This, for example, often occurred at gasoline station sites
where three to six wells were located within several tens of feet. At many of these sites, the
change in groundwater level across the site was on the order of tenths of a foot. Given the scale of
this research, changes in the groundwater level of less than one-foot were not considered
significant and the average groundwater level at the site was taken to represent the groundwater
level in that area. For multiple well sites where the groundwater levels
varied by more than one-foot, both the highest and lowest levels were recorded. Multiple
well sites where groundwater levels varied by more than several feet suggested the presence
of a perched water table.
For the research area located just outside the District boundary, data were collected
from SEA'S files as well as the Maryland Department of the Environment, which furnished
records of their groundwater monitoring wells within the study area.
The results of the data search revealed 120 monitoring wells or well sites that were
considered reliable for this research. The location of the well sites are shown on Figures 6
and 6A. A list of the well sites and groundwater elevation and location coordinates area
presented in Appendix B. Each well site was located on the USGS topographic base map and
their coordinates determined by digitizing.
Since many of the wells could not be directly monitored and the groundwater
elevations were monitored over a period of several months, the potential for significant
groundwater elevation changes due to seasonal and annual fluctuations was a concern. In
order to evaluate the potential impact of these fluctuation, the groundwater levels in the
several monitoring wells were reviewed over time. Two single wells (MW-4 located on
Massachusetts Avenue and Constitution Avenue NE; and MW-5 located on First and N
Streets, SW) and one well cluster consisting of three wells (MW-B location on Nannie Helen
Burroughs Avenue and 48th Street, NE) installed during the GWRAS had been monitored
over several months and provided an indication on the approximate seasonal fluctuations in
groundwater levels. These measurements are illustrated on Figure 7 (Schneider et al.,
1993c).
Figure 6,A - Groundwater Monitoring Well Locations &
Database Designations
25
Based on this graph, the typical fluctuation in the water table groundwater levels appears
to be within a three-foot range.
Soil Test Boring Data
Several areas in the research area did not have groundwater wells or data for use. In
these areas the data base of Schnabel Engineering Associates was searched to determine
if test borings with approximate groundwater levels were present. Although this data
was considered to provide only an indication of the groundwater elevation, they were
considered sufficiently accurate for the anticipated contour interval for this research.
N 9G
The test boring locations were reviewed to assess if they were consistent with what
would be expected in the region based on surrounding data. A total of 82 sites with test
borings were used for groundwater elevation data. The location and groundwater
elevation in the selected test borings are shown on Figures 8 and 8A; and are listed in
Appendix B.
Groundwater Analysis
Groundwater Contour Map Development
The surface water, groundwater monitoring well, and test boring data were used to
develop a groundwater contour map of the research area. The coordinates and elevation
of each of the data points were input into GEO-EAS, a geostatistical environmental
assessment computer program. GEO-EAS was used to produce 2-dimensional grids and
contour maps (Figures 9 and 15; Sheet 1) of kriged estimates from sample data.
28
Figure 9 - Kriging Standard Deviation (KSD) Contour Map
30
The grids and maps are based on semi-variograms generated by the computer
program. A semi-variogram analysis creates a model which interprets the spatial
correlation structure of the sample data set. All contouring techniques are based on the
assumption that some type of spatial correlation is present; that is, they assume that a
measurement at any point represents nearby locations better than locations farther away.
Semi-variogram analysis attempts to quantify this relationship by plotting the average
difference (variance) of pairs of measurements against the distances separating the pairs
(David, 1984).
A semi-variogram model is developed by examining all possible sample pairs
and grouping the pairs into classes of approximately equal distance. These classes are
commonly referred to as lags. For this research project, the unit of measurement for the
lags is meters. A best-fit curve is created for the plot of variance against distance. The
three components of a semi-variogram model are the nugget, sill, and range. The nugget
value corresponds to the y-intercept. The sill is the upper limit of the model, where the
model tends to level off at large distances. The range is the distance at which the model
reaches the maximum value. The curve shown on Figure 10 represents a typical semivariogram developed for a sample set of data unrelated to this research using a spherical
model. In a linear model, the ratio of "sill to range" is used to define the slope.
The curve developed during the semi-variogram modeling may not always pass
through the origin. The failure of a semi-variogram to tend to zero may occur for a
number of reasons, such as poor analytical precision, poor sample preparation, or erratic
fluctuations in the parameter of interest at a low scale. It was this latter cause in the
development of semivariograms for the mining industry that gave rise to the term
"nugget effect". Statisticians
31
generally refer to the nugget effect as the Chaotic Component (David, 1984).
The Chaotic Component or nugget effect is the variance of a totally random component
superimposed on the regionalized variable and is proportional to the number of samples
included in the analysis.
The typical semi-variogram model presented in Figure 10 shows a nugget of
approximately 5.0. The variance increases with distance until a maximum variance of 16
(the sill) is reached at a distance of 100 feet (the range). Based on the typical semivariogram model presented in Figure 10, one can deduce that a good model would be
one that has a low nugget (less built in, random error) and a low sill/range ( more
confidence in the estimates with greater distance).
After a suitable semi-variogram model is developed, a contour map of
groundwater elevations was developed using kriging contour procedures. Kriging is a
weighted movingaverage interpolation method where the set of weights assigned to the
samples minimizes the estimation variance (David, 1984). GEO-EAS's Krige routine
produces a regular grid of interpolated point or block estimates by using either
"ordinary" or "simple" kriging. Ordinary kriging estimates a value by using a weighted
average of the sample values within a local search neighborhood centered on a point or
block. Ordinary kriging assumes that local means for the sample data within the
neighborhood are not necessarily closely related to the population mean and, therefore,
only the samples in the local neighborhood are used for the estimate. Simple kriging
assumes that local means are relatively constant and equal to the population means.
Simple kriging assigns a weight to the population mean, making the assumption that the
value is constant over the site. Using kriging to generate a grid of block estimates rather
than a grid of point estimates is recommended for environmental applications
33
(Englund and Sparks, 1988). While point kriging usually produces estimates
very similar to those from block kriging, if the point being estimated coincides with a
sampled location, the estimate is set equal to the sample value. This is not appropriate
for contour mapping, which implicitly requires a spatial estimator. In block kriging, the
computer program requires that one input the size of the block to be kriged and the
number of blocks to be produced in both the x and y directions. Larger blocks will give
somewhat better approximations at the expense of increased computing time (Englund
and Sparks, 1988).
Kriging standard deviation (KSD) is the standard error of estimation computed
for a kriged estimate. The relationship of the kriging standard deviation to the actual
error of estimation is dependent on the semi-variogram model. Contour maps of the
kriging standard deviation were developed and used to evaluate areas that may require
additional research. On a kriging standard deviation contour map, those areas showing
the highest kriging errors or highest KSDs are assumed to represent the areas with the
lowest density of sample data (David, 1984).
RESULTS
For this research, semi-variograms were used to characterize the similarity of a
particular parameter, groundwater elevation, within a homogeneous area where the
characteristics were considered to be the same. Four different semi-variogram models were
developed. The first two models were based on a linear model with no transformation of
sample data. The second two models were based on a gaussian model with a log
transformation of the sample data. Table 2 presents a summary of the parameters used to
develop the various semi-variogram models.
Table 2 Summary of Model Parameters
1
linear
0
3500
350
0
1000
1750
2
linear
0
3000
300
50
1350
2700
3
gaussian
0
2000
200
0.170
0.625
1250
4
gaussian
0
2500
250
0.160
0.680
1400
Figures 11 through 14 present plots of the four semi-variogram models developed for the
sample data. The models based on logarithmic transformation of the data (Models 3 and 4)
were rejected because they produced the smallest ranges and had high nuggets in relation
to their sill values. Both linear models produced similar semi-variograms. However, Model
2 was selected as the most suitable model for this data. While Model 1 showed no nugget
effect, indicating no internal random error, Model 2 had a higher sill and range than Model
1. This indicated a greater confidence in the estimates at a greater distance.
35
Model 1 Semi Variogram for Elevation
P a r a m e t e r s
Q
C
t0
Distance ( meters )
Model 3 Semi Variogram for LN (Elevation)
Direct.: .000 Tol.
90.000 MaxBand: n/a
c
Minimum:
Maximum:
Mean
Var.
.000
5.649
3.353
1.5010
After evaluating the data by means of the semi-variogram analysis, elevation
estimates were developed using ordinary block kriging techniques. Elevation contours
were developed using a 50 by 50 meter grid in the kriging contouring program in
GEO-EAS. Given the accuracy of the groundwater elevation data, a 20-foot contour
interval was selected for the groundwater elevation data. Once the elevation contours
were developed, a contour map was plotted at a 1-inch to 2000-foot scale, equivalent
to the USGS topographic base map. The groundwater contours are presented on Sheet
1. The groundwater contour map indicates the presence of four primary hydraulic
divides and one secondary hydraulic divide. The groundwater contours also tend to
mirror the topographic contours suggesting that groundwater attempts to follow the
natural topographic gradient.
Data reflecting the perched water table in downtown Washington, DC was also
analyzed. However, insufficient data was collected to allow for semi-variogram
modeling. Contours of the perched water table were generated by inputting the
coordinates and elevation of each of the data points into SURFER, a contouring and 3D surface mapping computer program. The contour map generated by SURFER was
plotted over a geology map using a 20-foot contour interval. The perched water table
contours are presented on Figure 15. The perched water table identified in the
downtown region appears to be associated with the Wicomico Formation in the
Quaternary system.
A contour map of the kriging standard deviations (KSD) was also developed
using GEO-EAS (Figure 9). The KSD values ranged from 8.5 to 39.6, with 63 percent
of the values being less than 15 KSD. Thirty two percent of the values ranged between
15 and 20 KSD, and five percent were greater than 20 KSD. The KSD contour map
was developed
40
using a 5 KSD contour interval. High kriging errors of estimation were defined as
contours greater than or equal to 15 KSD. According to Englund and Sparks (1988),
areas on a kriging standard deviation contour map exhibiting the highest kriging errors
(highest KSD) represent the areas with the lowest density of sample data. Five areas o£
high KSD were noted on the contour map developed for this research. These areas
correspond the four recharge areas noted on the groundwater contour map and the
former Tiber Creek stream channel.
DISCUSSION
The water from the shallow water-table wells in the Coastal Plain originates as
precipitation in or near the local watershed or basin. Consequently, recharge to the
groundwater system occurs in the interstream areas, where sand layers outcrop, and by
percolation downward across the interbedded clay and silt layers. Recharge through
upward seepage from the underlying layers is also possible. The groundwater table
contour map presented as Sheet 1 indicates four hydraulic divides which represent
recharge areas. A hydraulic divide is a tract of high ground from which groundwater
moves away in both directions. The recharge areas indicated from Sheet 1 are similar to
those previously identified in Matheson et al.'s (1994) study. These are the US Soldier's
Home in northwest Washington DC, Fort Lincoln New Town in northeast Washington,
Garfield Heights and the Fort Davis Park/Fort Dupont Park area in southeast
Washington. A secondary hydraulic divide also occurs around the Lincoln Park area in
downtown Washington. Matheson et al. (1994) suggested that the secondary hydraulic
divide coincided with a perched water table. However, based on the limited data
gathered during this study, the perched water table appears to be located in the Logan
Circle area, northwest of the Lincoln Park area. A contour map of the perched water
table is presented in Figure 15 and shows the area to be roughly bounded by Logan
Circle, Georgia Avenue, 16th Street, and Euclid Street. According to the geologic map,
the perched water table appears to be associated with the Wicomico Formation in the
Quaternary system. This supports O'Connor and Kirkland's (1991) findings. The urban
character of Washington, DC may play a role in the presence of the perched water table.
Recharge can be diminished due to impervious surface areas and
43
seepage into combined sewer and stormdrain lines. Recharge may also be augmented by
seepage from water-bearing pipelines. The artificial recharge and discharge areas
created by an underground utility system of sewers, water pipes, and sump pumps can
significantly alter the water table contours. The perched water table identified in the
Logan Circle area could reflect the results of urbanization on the main water table in the
Coastal Plain deposits. Additional research in the downtown area is recommended to
delineate the exact location and extent of the perched water tables. The additional
research should include the collection of additional groundwater level measurements
from monitoring wells and an evaluation of the impacts that dewatering activities
associated with construction of downtown structures has on the water table.
Discharge from the system has historically occurred by seepage to springs, swamps,
marshes, and streams. However, many of these features have been filled, piped to
sewers or dried up because of increasing imperviousness of the land surface. Thus
rainfall is routed to the storm sewers instead of allowing infiltration into the ground
(Williams, 1974). Of the original natural stream drainage systems in the downtown area
of the Coastal Plain surficial aquifer, only the Anacostia River and its tributaries, Watts
Branch and Hickey Run, remain. Tiber Creek and many other small tributaries have
been filled or converted into sewer line (Matheson, et al., 1994). Matheson et al.'s
research suggested that despite sewering of old stream channels, such as Tiber Creek,
these channels still serve as the preferred flow paths for groundwater. The groundwater
contour map developed during this research indicates that groundwater flow contours
are following the natural topographic contours. Thus while sewering of Tiber Creek has
resulted in a rerouting of surface water runoff, groundwater still
44
REFERENCES
David, M., 1984. Geostatistical Ore Reserve Estimation, Elsevier, Amsterdam.
District of Columbia, Department of Environmental Services, 1983. Sewer system
evaluation survey, Vol. 3, Drainage area Tiber Creek, Washington, DC: District of
Columbia.
District of Columbia, Department of Public Works, 1989. Topographic mapping of
Washington, DC on scale of 1-inch equals 200 feet: District of Columbia.
Englund, E. and Sparks, A., 1988. GEO-EAS (Geostatistical Environmental
Assessment Software) User's Guide, EPA600/4-88/033.
Johnston, P.M., 1978. Geology and ground-water resources of Washington, DC and
vicinity. U.S. Geological Survey Water Supply Paper 1776, Reston, VA.
Matheson, G.M., Ridge, E., and Schneider, J., 1993. Impact of buried stream channels
on contaminant hydrogeology in Washington, DC: Proc. AEG/ASCE Symp.
Geohydrologic site Assessments - An Overview, Baltimore, MD.
Matheson, G.M., Schneider, J., and Zmijewski, D., 1994. Definition of Groundwater
Flow in the Water Table Aquifer of the Southern Anacostia River Basin. DC WRRC
Report No. 147, Washington, DC.
Mueser, Rutledge, Wentworth and Johnson, 1967. Final report for subsurface
investigation for the national capital transit system: WMATA.
O'Conner, J.V. and Kirkland, J., 1991. Correlation between Groundwater Levels and
Pleistocene Terraces in Mid-Downtown, DC: GSA Abs Vol 23 #1.
Papadopulos, S.S., Bennet, R.R., Mack F.K., and Prescott, P.C., 1974. Water from the
coastal plain aquifers in the Washington, DC metropolitan area: U.S. Geological
Survey Circular 697, Reston, VA.
Redd, J.C., and Obermeirer, S.F., 1982. The geology beneath Washington, DC - The
foundations of a nation's capital. Reviews in Engineering Geology, Vol. V.
Schnabel Engineering Associates, 1993. Phase II hydrogeoogc study, irrigation water
supply well development, U.S. National Arboretum, Washington, DC: Project
921085.
Schneider, J., Atobrah, K., O'Conner, J.V., and Watt, H.M., 1993a. Ground water
resource assessment study for the District of Columbia: well drilling and field
operations report - group A wells: DC WRRC Report No. 126, Washington, DC.
Schneider, J., Atobrah, K., O'Conner, J..V., and Watt, H.M., 1993b. Ground water
resource assessment study for the District of Columbia: well drilling and field
operations report - group B wells: DC WRRC Report No. 127, Washington, DC.
Schneider, J., Montaser, A., and Watt, H.M., 1993c. Ground water resource assessment
study for the District of Columbia: sampling and analysis report - group B wells,
Phase il: DC WRRC Report No. 138, Washington, DC.
Schneider, J., O'Conner, J.V., Chang, F., Wade, C.W., and Watt, H.M., 1993d. Ground
water resource assessment study for the District of Columbia: final report: DC
WRRC Report No. 145, Washington, DC.
USDA, 1976, Soil survey of the District of Columbia: U.S. Department of Agriculture,
Washington, DC.
USGS, 1965. Alexandria 7.5 min Quadrangle Map, with revisions: U.S. Geological
Survey, Reston, VA.
USGS, 1965. Anacostia 7.5 min Quadrangle Map, with revisions: U.S. Geological
Survey, Reston, VA.
USGS, 1965. Washington East 7.5 min Quadrangle Map, with revisions: U.S.
Geological Survey, Reston, VA.
USGS, 1965. Washington West 7.5 min Quadrangle Map, with revisions: U.S.
Geological Survey, Reston, VA.
Williams, G.P., 1977. Washington, DC's vanishing springs and waterways: U.S.
Geological Survey Circular 752, Reston, VA.
APPENDIX A
Glossary
Alluvial/fluvial sediments
Aquifer
Aquitard
deposits of silt, clay, sand and gravel made by streams or
rivers on stream/river beds and flood plains
a body of rock that is sufficiently permeable to conduct ground water
and to yield economically significant quantities of water to wells and
springs
a confining bed that retards but does not prevent the flow of water to or
from an adjacent aquifer
Hydraulic Conductivity
Lithology
rate of flow of water in gallons per day (gpd) through a
cross section of one square foot at one atmosphere of
pressure
the description of rocks based on characteristics such as color,
mineralogic composition, and grain size
Perched Water Table unconfined groundwater separated from the underlying main
body of groundwater by unsaturated rock
Potentiometric Surface
Surficial Aquifer
Transmissivity
Water Table
an imaginary surface representing the
total head of
groundwater and defined by the level to which water will
rise in a well
an unconfined aquifer whose rock members are exposed at the
surface of the earth
the rate at which water is transmitted through a unit width of
an aquifer under a unit hydraulic gradient
the surface of a body of unconfined groundwater at which the pressure
is equal to that of the atmosphere
APPENDIX B
Locations, Coordinates and Groundwater Contour
Elevations Used in Map Development
ID
Contract
East (m)
North (m)
Elevation (ft msl)
B 001
87016
325546
4307170
-13.0
B 002
86389
326246
4307140
28.0
B 003
82266
326065
4307980
31.0
B 004
82268
327175
4307990
27.0
B 005
861104
325969
4307600
13.0
B 006
85786
325897
4308370
45.0
B W7
861358
326264
4307590
17.0
B 008
87307
327201
4307570
19.0
B 009
911081
331609
4308420
16.0
B 010
91045
325633
4304320
-4.0
B 011
92032
327368
4307900
21.0
B 012
93060
326250
4305400
38.0
B 013
932019
327614
4312800
85.0
B 014
80003
324600
4310950
170.0
B 015
80278
324850
4316300
283.9
B 016
890517
325000
4313000
133.0
B 017
890579
324681
4309477
78.0
B 018
890808
323750
4308750
21.0
B 019
891119
323750
4307600
25.0
B 020
891438
324000
4308750
71.0
B 021
891533
325000
4308000
51.0
B 022
891617
324000
4308500
70.0
B 023
891624
324000
4307800
37.0
B 024
891741
324550
4306950
-20.0
B 025
891758
324000
4312000
147.0
B 026
900341
324600
4307100
24.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
B 027
80332
324050
4307270
-9.0
B 028
900804
32480
4307000
-3.0
B 029
900818
323266
4307776
23.0
B 030
901469
324700
4306400
-6.0
B 031
901229
324250
4304360
8.0
B 032
910250
323653
4312394
12.0
B 033
80421
323200
4307780
21.4
B 034
80429
323700
4308000
50.7
B 035
80581
323200
4307500
46.0
B 036
80036
323600
4307250
16.0
B 037
80618
323700
4307150
1.0
B 038
81418
323450
4308100
39.4
B 039
80062
324230
4306830
-1.0
B 040
81481
323150
4308100
51.0
B 041
81592
323350
4307800
40.0
B 042
82012
324550
4306730
0.0
B 043
82055
324020
4307000
0.0
B 044
82084
323530
4308500
68.0
B 045
80118
324790
4307370
20.0
B 046
82170
323950
4305650
-2.0
B 047
82202
323300
4308250
54.0
B 048
82296
323500
4317000
202.0
B 049
82415
323120
4308950
71.0
B 050
82447
323950
4307900
51.0
B 051
83333
323200
4307600
21.0
B 052
80138
323300
4308380
65.0
B 053
83513
323800
4312750
164.0
B 054
84164
323850
4307380
34.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
B 055
84205
323150
4308600
68.0
B 056
84892
323740
4307509
34.0
B 057
84936
323150
4307500
29.0
B 058
85054
323970
4308403
63.0
B 059
80183
323320
4308020
41.5
B 060
85192
323397
4307927
40.0
B 061
85274
324050
4307500
25.0
B 062
86126
324281
4308231
52.5
B 063
86205
324694
4304979
20.0
B 064
80211
324700
4306740
10.2
B 065
86370
324912
4309716
79.0
B 066
86371
324900
4309300
79.0
B 067
86762
324100
4307900
54.0
B 068
86947
323966
4307749
32.0
B 069
86954
324491
4309914
100.0
B 070
87031
323324
4310484
10.0
B 071
870496
324616
4306938
-6.6
B 072
870952
323189
4308315
50.0
B 073
870954
324612
4307158
12.0
B 074
880603
324400
4307180
-12.0
B 075
80238
323320
4308650
68.6
B 076
880884
324149
4307688
9.0
B 077
881428
324200
4307750
47.0
B 078
890006
323800
4307500
27.0
B 079
890024
324526
4307159
-25.0
B 080
890025
322974
4308016
42.0
B 080
890029
324150
4307800
49.0
B 082
890213
323800
4309600
116.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
L 001
141
324850
4310640
150.0
L 001
140
324970
4310660
150.0
L 001
138
325180
4310530
150.0
L 001
137
325061
4310270
150.0
L 001
136
325260
4310250
150.0
L 001
135
325420
4310120
150.0
L 001
134
325380
4310050
150.0
L 001
132
325050
4310190
150.0
L 001
131
324950
4310420
150.0
L 001
139
325090
4310510
150.0
L 002
130
324900
4310900
175.0
L 003
129
324862
4311150
184.0
L 004
124
329717
4308590
8.0
L 005
125
329418
4308840
14.0
L 006
126
329640
4309130
50.0
M 001
87012
325670
4304020
2.0
M 002
87015
326069
4307860
27.0
M 003
88017
325743
4305210
17.0
M 004
89012
326147
4308180
36.0
M 005
89051
329808
4311400
0.0
M 006
90022
324991
4305720
-3.0
M 007
91006
328440
4309430
69.0
M 008
91009
326198
4308550
57.0
M 009
91055
325612
4306910
-3.0
M 010
92007
324972
4304480
5.0
M O1l
92035
330104
4309870
59.0
M 012
92079
327542
4309910
129.0
M 013
92084
329948
4304070
151.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
M 014
93014
329586
4310260
88.0
M 015
93031
326405
4306100
65.0
M 016
93054
327316
4311620
123.0
M 017
93062
329167
4309450
32.0
M 018
93069
327265
4311400
129.0
M 019
93077
329430
4303100
272.0
M 020
93086
328857
4304700
13.0
M 021
90010
326084
4308510
40.0
M 022
90083
330128
4310780
79.0
M 023
92012
328298
4308060
79.0
M 024
92052
327380
4312960
79.0
M 025
88015
326643
4313820
118.0
M 026
89002
326259
4313700
131.0
M 027
89035
328954
4309390
35.0
M 028
87017
325664
4300200
136.0
M 029
93061
326270
4307040
25.0
M 030
8131
325507
4307860
28.0
M 031
8081
324548
4306890
4.0
M 032
8101
323824
4308280
52.0
M 033
8051
323995
4307410
6.0
M 034
8041
327795
4306150
42.0
M 035
8011
326835
4305140
21.0
M 036
900849
332401
4305240
110.0
M 037
8232
325249
4304470
3.0
M 038
8231
325199
4305740
-5.0
M 039
8171
326247
4306440
33.0
M 040
8161
325494
4307290
-8.0
M 041
8141
326599
4307440
22.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
M 042
921170
326646
4309570
76.0
M 043
89999
326664
4309720
83.0
M 044
10010
325354
4307510
27.0
M 045
82011
325560
4307150
-11.0
M 046
92089
327389
4309690
107.0
M 047
90084
331613
4307720
13.0
M 048
91072
326404
4307600
18.0
M 049
90050
327436
4310380
152.0
M 050
87009
328600
4305750
49.0
M 051
89014
330787
4306660
28.0
M 052
90047
326788
4313090
142.0
M 053
91059
327165
4304950
37.0
M 054
90071
325723
4305160
-9.0
M 055
91054
328652
4302080
251.0
M 056
92031
326548
4308350
41.0
M 057
92075
332321
4307330
35.0
M 058
90052
327036
4303270
28.0
M 059
90078
327453
4305530
49.0
M 060
90075
326224
4304960
-3.0
M 061
90035
331308
4304180
276.0
M 062
90060
331988
4306220
79.0
M 063
90014
326994
4305760
56.0
M 064
890289
323997
4307579
-6.0
M 065
890503
324800
4309850
93.0
M 066
890844
323800
4307900
31.0
M 067
890851
323850
4305600
-2.0
M 068
891113
324500
4307500
3.0
M 069
891354
324100
4307050
-17.0
Elevation (ft
Contract
East (m)
North (m)
M 070
891410
323570
4308260
34.0
M 071
891547
323500
4308150
47.0
M 072
891752
323500
4307750
23.5
M 073
80290
323780
4307820
24.2
M 074
90406
324971
4305728
-8.0
M 075
900782
323398
4308033
21.0
M 076
901404
323534
4307912
20.0
M 077
80357
323980
4307580
30.2
M 078
80428
323300
4307880
31.5
M 079
80496
324080
4309450
81.6
M 080
80612
323750
4307580
35.7
M 081
81086
323700
4307670
49.5
M 082
81142
323970
4307560
26.8
M 083
81241
324700
4306800
-11.5
M 084
81313
324010
4307810
44.2
M 085
81359
325050
4314900
230.0
M 086
81406
324750
4307200
-18.0
M 087
81426
324250
4306900
34.7
M 088
81429
323970
4307700
45.0
M 089
81440
323950
4307750
32.0
81464
324150
4306850
-14.5
81536
323200
4308100
44.0
81604
323500
4307850
33.0
82124
323480
4307400
25.0
82133
323950
4307780
43.0
82213
324100
4307000
12.0
82515
323600
4307150
-2.4
83081
323100
4308300
57.0
M 090
M 091
M 092
M 093
M 094
M 095
M 096
M 097
ID
Contract
East (m)
North (m)
Elevation (ft msl)
M 098
84216
324240
4307350
-9.3
M 099
84475
323650
4307700
20.0
M 1(x)
84696
323950
4307850
37.0
M 101
84964
324800
4305510
-6.7
M 102
85083
323753
4308019
39.0
M 103
85094
323700
4307200
-15.5
M 104
85143
324250
4307000
-18.0
M 105
85190
324300
4305750
-22.0
M 106
85533
324750
4306800
-16.0
M 107
85561
324500
4306750
-12.0
M 108
86318
324083
4307303
16.5
M 109
86357
323070
4307450
3.5
M 110
86419
323900
4307750
43.0
M 111
86807
323967
4307405
-4.0
M 112
86867
323000
4308000
32.0
M 113
80224
323700
4307670
31.4
M 114
870496
324607
4306913
10.0
M 115
870771
324150
4307250
-5.0
M 116
880270
324000
4308121
48.0
M 117
880700
324139
4309611
62.0
M 118
881270
323700
4306800
-13.0
M 119
881418
324000
4307700
31.0
M 120
881482
323969
4307894
19.0
S 001
1
326310
4315230
120.0
S 002
2
326634
4315250
110.0
S 003
3
326871
4315140
100.0
S 004
4
327113
4315210
90.0
S 005
5
327257
4315360
80.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 006
6
327432
4315410
70.0
S 007
7
327752
4315560
60.0
S 008
8
327851
4315500
60.0
S 009
9
328140
4315210
50.0
S 010
10
328388
4314170
40.0
S 011
11
328663
4313820
30.0
S 012
12
328559
4313640
30.0
S 013
13
328215
4313670
40.0
S 014
14
328027
4313560
50.0
S 015
15
327747
4313640
60.0
S 016
16
327640
4313640
70.0
S 017
17
327502
4313640
80.0
S 018
18
327213
4313730
90.0
S 019
19
327911
4313410
50.0
S 020
20
327855
4313300
60.0
S 021
21
327719
4313140
70.0
S 022
22
329393
4313230
30.0
S 023
23
329600
4312750
20.0
S 024
24
329448
4312680
30.0
S 025
25
329227
4312460
30.0
S 026
26
328928
4312390
40.0
S 027
27
330207
4312850
10.0
S 028
28
330226
4310320
150.0
S 029
29
330250
4310300
140.0
S 030
30
330275
4310280
120.0
S 031
31
330328
4310240
100.0
S 032
32
330504
4310240
50.0
S 033
33
330644
4310340
50.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 034
34
335020
4307870
55.0
S 035
35
334922
4308200
50.0
S 036
36
334868
4308270
50.0
S 037
37
334767
4308410
40.0
S 038
38
334421
4308930
30.0
S 039
39
333863
4309060
20.0
S 040
40
333607
4308820
20.0
S 041
41
333795
4308750
30.0
S 042
42
333991
4308330
40.0
S 043
43
333989
4308040
50.0
S 044
44
333981
4307940
60.0
S 045
45
334012
4307810
70.0
S 046
46
334052
4307670
80.0
S 047
47
333208
4308000
60.0
S 048
48
333021
4308190
50.0
S 049
49
332876
4308290
40.0
S 050
50
332619
4308280
30.0
S 051
51
331864
4308440
20.0
S 052
52
331583
4308530
10.0
S 053
53
333224
4308960
15.0
S 054
54
334200
4309950
50.0
S 055
55
334269
4309820
40.0
S 056
56
334193
4309640
30.0
S 057
57
334041
4309520
30.0
S 058
58
334724
4309630
30.0
S 059
59
331123
4307720
10.0
S 060
60
331194
4307610
20.0
S 061
61
331546
4307380
30.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 062
62
332051
4307160
30.0
S 063
63
332328
4307230
40.0
S 064
64
332881
4306960
50.0
S 065
65
333253
4306810
60.0
S 066
66
333533
4306640
70.0
S 067
67
333720
4306480
80.0
S 068
68
333906
4306460
90.0
S 069
69
333789
4305760
100.0
S 070
70
332933
4304900
160.0
S 071
71
332801
4304980
150.0
S 072
72
332755
4305080
140.0
S 073
73
332673
4305130
130.0
S 074
74
332345
4305320
120.0
S 075
75
332025
4305590
100.0
S 076
76
331785
4306220
80.0
S 077
77
331309
4304380
200.0
S 078
78
331173
4304550
150.0
S 079
79
330995
4304910
100.0
S 080
80
330878
4305030
100.0
S 081
81
330785
4305100
100.0
S 082
82
330463
4305210
50.0
S 083
83
330286
4305270
40.0
S 084
84
329969
4305380
30.0
S 085
85
329898
4305370
20.0
S 086
86
330243
4304410
100.0
S 087
87
329954
4304530
80.0
S 088
88
329753
4304710
70.0
S 089
89
329707
4304730
60.0
ID
Contract
East (tn)
North (tn)
Elevation (ft msl)
S 090
90
329530
4304880
50.0
S 091
91
329462
4304890
40.0
S 092
92
329363
4304880
30.0
S 093
93
327237
4301690
135.0
S 094
94
327525
4301610
175.0
S 095
95
327518
4301740
180.0
S 096
96
332183
4303270
200.0
S 097
97
331795
4303330
180.0
S 098
98
331207
4303100
170.0
S 099
99
330796
4302860
160.0
S 100
100
330502
4302490
150.0
S 101
101
330063
4302170
140.0
S 102
102
329809
4301880
130.0
S 103
103
329618
4301600
120.0
S 104
104
329381
4301410
110.0
S 105
105
328839
4301130
100.0
S 106
106
328390
4301000
90.0
S 107
107
327978
4300880
80.0
S 108
108
327378
4300610
75.0
S 109
109
327467
4300410
100.0
S 110
110
326787
4300440
60.0
S 111
111
326359
4300080
50.0
S 112
112
326142
4299870
40.0
S 113
113
327191
4316460
100.0
S 114
114
327322
4316310
90.0
S 115
115
327440
4316040
80.0
S 116
116
327656
4315870
70.0
S 117
117
326123
4311100
160.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 1113
118
326109
4311290
180.0
S 119
119
326204
4311290
175.0
S 120
120
329150
4309180
35.0
S 121
121
329267
4309040
20.0
S 122
122
329555
4308960
20.0
S 123
123
329363
4308840
10.0
S 124
127
325392
4311570
275.0
S 125
128
325353
4311050
210.0
S 126
142
328654
4310390
100.0
S 127
143
331335
4308870
6.0
S 128
144
331415
4308880
6.0
S 129
145
331475
4308870
6.0
S 130
146
331453
4308800
6.0
S 131
147
331424
4308760
6.0
S 132
148
331396
4308750
6.0
S 133
149
331351
4308760
6.0
S 134
150
331310
4308790
6.0
S 135
151
331290
4308780
6.0
S 136
152
331261
4308780
6.0
S 137
153
331228
4308800
6.0
S 138
154
331210
4308840
6.0
S 139
155
328837
4308130
47.0
S 140
156
332952
4311540
50.0
S 141
157
332775
4311520
40.0
S 142
158
332470
4311440
30.0
S 143
159
332182
4311300
20.0
S 144
160
324797
4302210
4.0
S 145
161
324955
4302610
4.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 146
162
325368
4303030
4.0
S 147
163
325639
4303200
5.0
S 148
164
325952
4303690
5.0
S 149
165
326034
4303890
5.0
S 150
166
326134
4304050
5.0
S 151
167
326410
4304060
5.0
S 152
168
326696
4303980
5.0
S 153
169
326928
4303930
5.0
S 154
170
327147
4304080
5.0
S 155
171
327334
4304220
5.0
S 156
172
327692
4304530
5.0
S 157
173
327940
4304640
5.0
S 158
174
328268
4304860
5.0
S 159
175
328591
4304900
5.0
S 160
176
328845
4305140
5.0
S 161
177
329058
4305640
5.0
S 162
178
329510
4305970
5.0
S 163
179
329206
4306070
5.0
S 164
180
329375
4305760
5.0
S 165
181
329607
4306280
5.0
S 166
182
329347
4306280
5.0
S 167
183
329757
4307090
5.0
S 168
184
329386
4307100
5.0
S 169
185
329738
4306670
5.0
S 170
186
329427
4306730
5.0
S 171
187
329330
4307240
5.0
S 172
188
329329
4307300
5.0
S 173
189
329319
4307420
5.0
ID
Contract
East (m)
North (m)
Elevation (ft msl)
S 174
190
329332
4307540
5.0
S 175
191
329360
4307640
5.0
S 176
192
329397
4307760
5.0
S 177
193
329455
4307830
5.0
S 178
194
329525
4307870
5.0
S 179
195
329551
4307950
5.0
S 180
196
329588
4308030
5.0
S 181
197
329636
4308120
5.0
S 182
198
329708
4308200
5.0
S 183
199
329789
4308270
5.0
S 184
2(X)
329889
4308280
5.0
S 185
201
329967
4308280
5.0
S 186
202
330030
4308240
5.0
S 187
203
329970
4308200
5.0
S 188
204
329927
4308160
5.0
S 189
205
329911
4308120
5.0
S 190
206
329878
4308070
5.0
S 191
207
329851
4308020
5.0
S 192
208
329818
4307950
5.0
S 193
209
329745
4307880
5.0
S 194
210
329690
4307750
5.0
S 195
211
329620
4307620
5.0
S 196
212
329518
4307430
5.0
S 197
213
329473
4307350
5.0
S 198
214
329438
4307260
5.0
S 199
215
329423
4307180
5.0
S 200
216
329864
4307640
5.0
S 201
217
330079
4308120
5.0
Contract
East (rn)
North
S 202
218
330089
4308090
S 203
219
330150
4308280
S 204
220
330300
4308410
S 205
221
330357
4308600
S 206
222
330472
4309000
S 207
223
330705
4308820
S 208
224
331051
4308510
S 209
225
330850
4309050
S 210
226
331166
4309150
S 211
227
331435
4309420
S 212
228
331654
4309660
S 213
229
331734
4310160
S 214
230
331687
4310760
S 215
231
331659
4311320
S 216
232
331372
4311720
S 217
233
331239
4311990
S 218
234
331527
4312430
S 219
235
331365
4312300
S 220
236
325980
4304240
S 221
237
325820
4304000
S 222
238
325717
4303820
S 223
239
325450
4303380
S 224
240
325189
4303230
S 225
241
324710
4302940
S 226
242
324545
4302560
S 227
243
324250
4302000
S 228
244
332035
4310660
S 229
245
331400
4309110
ID