HomeMy WebLinkAboutEffects of Proposed Mine Expansion on Public Water Supply Wells 07-2004
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EFFECTS OF PROPOSED MINE
EXPANSION ON PUBLIC WATER
SUPPL V WELLS
City of Carmel Utilities
Carmel, Indiana
PREPARED By
WHPA, INCORPORATED
WITTMAN HYDRO PLANNING ASSOCIATES
BLOOMINGTON, INDIANA
JULY, 2004
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WHPA
Assessment of the Effects of Proposed Mine Expansion
at the South Mueller Property on Public Water Supply
Wells near Carmel, Indiana
27th July 2004
Prepared by
Wittman Hydro Planning Associates, Inc.
Bloomington, Indiana
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Contents
1 Introduction
1.1 Summary of findings
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2 Hydrogeologic setting
2.1 Geology........................
2.1.1 Outwash along the White River . . . . . . .
2.1.2 Confined sand and gravel intertill aquifers
2.1.3 Bedrock aquifer. . . . . . . . . . . . . . .
2.2 Hydrology......................
2.2.1 Surface water and groundwater interactions
2.2.2 Potentiometric data . . . . . . . . . . . . . . .
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3 Model development
3.1 Model code selection . . . . . .. ......
3.2 Aquifer conceptualization . . .
3.3 Regional boundary conditions .........
3.4 Local boundary conditions . . . . . . . . . .
3.5 Representing mine operations in the model. . .
3.6 Potentiometric head observations. . . . . . . .
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"Post Mining" scenario .
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4 Results
4.1 Model calibration . . . . . . . . .
4.2 Analysis of parameter uncertainty
4.3 Reduced recharge analysis
4.4 Scenarios and results . . . . . . .
4.4.1
4.4.2
4.4.3
"Current" scenario . . . . . .
"South Mueller Active" scenario .
5 Conclusions
36
References
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List of Figures
1 Area of interest in Hamilton County, Indiana. . . . . . 2
2 Pumping in the City of Carmel wells from 1988-2002. 3
3 Site location map. . . . . . . . . . . . . . . . . . . . . 5
4 Plan view of the relationships between conceptual aquifer domains. 14
5 Conceptual model cross section. . . . . . . . . . . . . . . . . . . . 15
6 Layout of wells and line sinks in the regional model. ........ 16
7 Aquifer domains and local boundary conditions for the current conditions
near Carmel Plant 4. ................... 18
8 Results of calibration and best-fit potentiometric surface. 21
9 Summary calibration statistics from GFLOW. . . . . . . 22
10 Determination of a composite capture zone. . . . . . . . 24
11 Former gravel pit ponds that contribute water to the Plant 4 wellfield, with
identifying names.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25
12 Modeled potentiometric surface and composite 5-year capture zone for the
current conditions. .............................. 29
13 Current operations for "reduce-recharge" conditions. ............ 30
14 Modeled potentiometric surface an composite 5-year capture zone for the
current conditions with Well 22. .... . . . . . . . . . . . . . . . . . .. 32
15 Modeled potentiometric surface and composite 5-year capture zone when
the South Mueller property is actively mined. . . . . . . . . . . . . . . .. 33
16 Change in heads between current conditions and those when the South
Mueller property is actively mined. . . . . . . . . . . . . . . . . . . . . ., 34
17 Results for "reduced-recharge" conditions when the South Mueller property
is actively mined. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
List of Tables
1 Annual production well data for the Plant 4 Well Field (All data reported in
million gallons per year). . . . . . . . . . . . . . . . 4
2 Aquifer classification scheme for conceptual model. . . . . . . . . . . . ., 14
3 Parameters for "best-fit" model. .... . . . . . . . . . . . . . . . . . .. 22
4 Water levels in Ponds NW and SW (source: Martin Marietta Materials, Inc.). 27
ii
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1 Introduction
Carmel's municipal drinking water is currently supplied by approximately 20 production
wells, most of which are located within a mile of the White River in south-central Hamilton
County, Indiana (Figure 1). Some of the wells have been in operation since before 1960
but most of the production comes from the most recent additions to the system at Plants 4
and 5. Most of the wells are screened in sand and gravel along the edge of a thick outwash
aquifer that roughly coincides with the flood plain of the White River. The wells vary in
both depth and yield.
In order to satisfy the pace of residential growth in the area the annual production of
the four water plants nearly doubled between 1997 and 2002 (Figure 2). Today, Carmel's
average annual production (2000-2003) is approximately 8 million gallons per day (MGD)
with Plant 4 pumping and average of 0.7 MGD (Table 1). It is expected that water use
will continue to increase rapidly in the future; for example, the proposed annexation of
land outside the current corporate boundary would greatly expand the demand for drinking
water.
Martin Marietta Minerals, Inc. has operated gravel pits and aggregate mines along the
southern border of Hamilton County for decades. In the area South of 106th street there are
several abandoned pits and ponds as well as a large open pit limestone mine. As growth in
the area continues there is increasing demand for gravel and aggregate for roads, bridges,
and buildings. Until recently, these operations have coexisted near the water wells without
any conflict. However, in order to increase production Martin Marietta has proposed an
expansion of its current operations. In their proposal they outline a plan to excavate the
gravel above the bedrock surface and then to mine into the bedrock surface as they have
done in their existing pit. In addition, they are planning to open sand and gravel pits at new
locations over a period of years to satisfy the growing demand for aggregate.
There are separate applications for expansion at two properties: the North Mueller prop-
erty, which includes the area north of 106th street between Hazel Dell Parkway and Gray
Road, and the South Mueller property which is located just south of 106th Street between
Hazel Dell Parkway and Gray Road (Figure 3). The proposed mining at North Mueller
would include some additional removal of sand and gravel as well as new underground
limestone aggregate mining. The proposed mining at the South Mueller property would be
done in stages. The first stage would be the removal of the sand and gravel while water
removal occurs along the edges. The next phase is to expand the boundaries of the existing
open pit to the North to serve the North Indianapolis Plant.
As Carmel's role as a regional drinking-water supplier grows, it is critical that the city
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Area of
Interest
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2 0 2 4 6 8 10 Miles
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Figure 1: Area of interest in Hamilton County, Indiana.
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3000
(j) 2000
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Figure 2: Pumping in the City of Carmel wells from] 988-2002.
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Well 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Number
10 102.94 206.23 226.40 223.85 135.71 181.69 190.12 61.01 24.59 182.31 175.85 273.57 217.26 212.47 124.82
11 88.35 206.23 154.67 63.36 64.65 65.24 95.98 42.32 40.25 26.06 142.73 97.95 11.79 29.97 30.86
12 93.88 104.15 72.32 71.87 83.96 65.05 54.70 31.93 57.49 23.93 69.13 37.51 5.79 59.71 64.02
Annual
Total 285.17 516.61 453.39 359.08 284.32 311.98 340.80 135.26 122.33 232.30 387.71 409.03 234.84 302.15 219.70
Average Annual Production 306.31
Table 1: Annual production well data for the Plant 4 Well Field (All data reported in million gallons per year).
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0.1 0 0.1 0.2 Miles
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LEGEND
Wittman Hydro Planning Associates
\"~.~o..,..~Y\;I""J1rlllC:;m"b-~
N Roads
D Mining Gravel Pits
_ Hydrology
Figure 3: Site location map.
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protects the aquifers from any deterioration in yield. This report was written to answer an
important question raised by the recent growth in the area: Will the proposed new mining
activity affect Carmel's drinking-water supply? How much do these two activities conflict
with one another and how compatible are they?
We have used groundwater models to investigate these issues. The models that include
regional boundary conditions and flow in the unconsolidated aquifers, with local refinement
in the vicinity of the proposed mining works. Our analysis provided information about the
marginal change of the new mines that could alter conditions at the closest drinking-water
treatment plant (Plant 4). This analysis was done with data provided by the City about the
configuration of the gravel deposits in the subsurface, information provided by the Indi-
ana Department of Natural Resources from domestic well logs, and standard groundwater
modeling tools. The effects of mining operations and reduced recharge were considered
together to better understand unknown future conditions.
This study is part of a larger ongoing water-supply planning effort being conducted by
the Utility that includes subsurface data collection and organization, wellhead protection
planning, and water-supply expansion planning.
1.1 Summary of findings
There is no single index of the "effects of mining" that captures all of the changes that could
take place once the proposed excavations are underway. Instead, we considered two types
of impacts: changes in water levels in the aquifer near the Plant 4 well field, and changes in
the source water pumped by the well field. The first of these is an indicator of the reduction
in yield that results from the competition between the drinking-water wells and around the
mine pits. We examined impacts both during and after mining.
. Additional mining could reduce groundwater levels at the Plant 4 well field by about
2 - 3 ft while the mines are active. The amount of water pumped by a well is roughly
proportional to the draw down in the well. Since the original pumping tests showed
about 16ft of drawdown when the wells were pumped at capacity and the modeling
predicts an additional 2 - 3 ft of decline, this translates to roughly 15% reduction in
total wellfield capacity during mining.
. In the 20 years that the proposed mines are active there would be an increase in the
amount of drinking water that comes from abandoned gravel pits and ponds. Cur-
rently we estimate that approximately one-half of the water pumped at the Plant 4
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well field had been in a pit or pond within the last five years. While the mines are
active this will increase to more than 70% of all the water in the well field.
. With conditions of reduced recharge, the effects of the proposed mining will be to
decrease water levels by 3 it compared to reduced recharge under current conditions.
With reduced recharge there are changes in water use and stage along the river that
may alter the actual conditions at the well field. This is a result of reductions in
regional flow from the till aquifers west of Plant 4 and the increasing importance of
the White River.
2 Hydrogeologic setting
According to the Hydrogeologic Atlas of Aquifers in Indiana [Fenelon and Bobay, 1994]
aquifers in the West Fork White River basin are categorized as follows:
1. thick outwash adjacent to major rivers
2. thin outwash aquifers in thick glacial till
3. discontinuous sand and gravel in thin glacial till
4. limestone in bedrock covered by variable layers of till (northwest of Carmel, Indiana)
The well fields developed by Carmel Utilities in Hamilton County are typical of commu-
nity well fields in central Indiana. Carmel's well fields are located in thicker portions of
the sand-and-gravel aquifer west of the West Fork (White River). The wide outwash plains
along the White River have relatively large recharge rates due to the highly-permeable sur-
ficial deposits and the low, flat-lying landscape. Under natural conditions, recharge into the
thick outwash aquifer leaves as "baseflow" in the perennial streams. Part of the water, how-
ever, is intercepted by the Carmel wells and is used for drinking-water supplies. In some
cases, wells may even induce aquifer recharge from the White River or its tributaries. The
interactions between surface water and groundwater is affected by the pumping rates of the
wells, the hydraulic properties of the river bed, the distance between the wells and the river,
and other factors, including past and present mining activities.
2.1 Geology
Hamilton County is in the central part of the glaciated portion of Indiana, near the center of
the White River basin. The thickness of unconsolidated deposits varies from less than 20 it
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to over 500ft [Gray, 1983]. Beneath the unconsolidated section, the bedrock dips towards
the Illinois Basin. The bedrock underlying most of the unconsolidated section in the study
area is Silurian-Devonian aged carbonate rock. The thickness of the bedrock increases to
the west. As described above, the two water resource aquifers tapped by high capacity wells
in Hamilton County are; 1) outwash deposits along the larger streams, and 2) thin outwash
layers in the till.
2.1.1 Outwash along the White River
The White River outwash was deposited by rapidly moving meltwater during the retreat of
continental glaciers at the end of the last Ice Age. In Hamilton County the deposits are in
a 1 - 3 mi wide channel of coarse sand and gravel in an irregularly-shaped valley, roughly
coinciding with the West Fork White River flood plain. Typically, the thick outwash aquifer
is overlain by 5 - 10 ft of clayey material and may extend to depths of 110 ft below grade.
Outwash aquifer deposits range from fine sands to coarse gravel to cobbles but primar-
ily consist of well sorted, coarse-grained sand and gravel [Jones and Henry, 1994]. Thick
outwash aquifer deposits also exist west of the river near Martin Marietta's operations.
The deposits used by the city wells are ideal as a water supply for two reasons: 1) the
gravel and sand have a high transmissivity, allowing high flows towards the wells, and 2)
water-supply wells situated near a perennial stream can "induce" recharge from the stream
into the aquifer, assuring a more reliable water supply during times of drought and reduced
recharge.
The aquifer varies in thickness and extent within the Study Area. Based on Carmel
Utilities test hole and production well data, the thickness of the sand and gravel ranges from
5 - 100 ft. Within the model area of detail, the average thickness is 80 ft. The gravel thins
both east and west of the pre-glacial bedrock valley trough and may be absent, particularly
in areas where subsurface bedrock highs exist. While unconfined conditions prevail in the
thick outwash aquifer, semi-confined to confined conditions do occur where surficial clay
layers and/or significant subsurface clay layers are present.
The hydraulic conductivity (K) of the outwash along the West Fork has been estimated
at over 340ft/d in some areas based on pump test results [Bailey and Imbrigiotta, 1982].
The saturated thickness of the outwash varies between 50 - 120 ft in the region. The trans-
missivity of the aquifer (defined as the product of hydraulic conductivity and saturated
thickness) is highest where the aquifer is thickest west of the river along 106th Ave. in
southern Hamilton County [Cable et al., 1971]. Previous analyses by the USGS have sug-
gested that in Hamilton County this aquifer is capable of producing 30MGD of water with
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limited effect on regional water levels.
Arihood [1982] reports a range of K values for the thick outwash aquifer (based on
aquifer material) to be from 40 - 415ft/d with corresponding values for T ranging from
1,000 - 28,000 I t2 / d. Based on aquifer test pumping results from those Carmel production
wells that are completed in the thick outwash aquifer, estimated K values range from 191 -
8651t/d corresponding to T values from 17, 500-38,000It2 /d [WHPA, 2003]. While the
range for K and T in this aquifer can be highly variable, typical values for K and T range
from 200 - 3001t/d and 16,000- 24,000ft2 /d, respectively.
This aquifer is recharged by precipitation and by inflow from intertill aquifers east and
west along the perimeter. Water budget studies done by the USGS suggest that infiltration
rates into the outwash system along the White River may be up to 12in/yr [Meyer, 1979].
In addition to direct areal recharge into the outwash, the aquifer receives water along the
perimeter from the confined intertill aquifers discharging towards the White River.
2.1.2 Confined sand and gravel intertill aquifers
Further away from the river, wells are often situated in sand and gravel deposits buried
within the glacial till. These intertill aquifers are often discontinuous and, beyond the City
of Carmel geodata archive, they have not been mapped at a useful scale. The hydrogeologic
investigations done by the city, along with a more recent mapping effort conducted by
the Indiana Geological Survey, have provided substantial information about these systems
[Brown et al., 1995]. The thicker unconsolidated deposits almost always include poorly
connected layers of sand and gravel, which together may form a series of partially connected
till aquifers. The distribution of these intertill aquifers were further evaluated by direct
analysis of the well log records from the area. Where present, thin outwash aquifers within
the till are confined and are commonly relatively thin (average thicknesses range from 5-
20 It). In some parts of the study area there is no significant transmissivity above bedrock.
However, the data indicates that in the thicker unconsolidated section the till often includes
fairly continuous sand and gravel layers.
In general, K values reported for glacial till range from 10-7 - 25 ft / d [Driscoll, 1986]
while the transmissivity of the interbedded thin outwash aquifers that occur within the till
are typically much higher. It is important to remember that these more permeable sand and
gravel layers may be regionally continuous and locally variable. Previous work in the area
indicates that there are several "zones," including the average or "regional" value of K for
the intertill aquifer, that account for transmissivity of both glacial till and discontinuous,
interbedded sand and gravel.
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Arihood [1982] reports a range of K values for the confined interbedded thin out-
wash aquifers in Hamilton County to be from 200 - 433 ft j d . Assuming average aquifer
thicknesses ranging from 5 - 20 ft, corresponding values for transmissivity (T) is between
1000 - 8660 ft2 j d. Where multiple interbedded outwash aquifers are present within the till
at any given location, the combined T over the entire section will be larger.
2.1.3 Bedrock aquifer
In comparison to the thick outwash and intertill aquifers, the bedrock aquifer is present
throughout the model area but infrequently used as a groundwater resource because suf-
ficient groundwater supplies are usually encountered within the unconsolidated deposits.
Based on well log data, the bedrock is occasionally in direct contact with overlying out-
wash deposits but may also be separated from the overlying outwash by relatively thin clay
layers (till). In isolated areas, the thickness of the overlying till approaches 50ft.
Within the bedrock, well drillers report some variability of hardness, fracturing, and
solution features but overall, it is relatively impermeable and does not appear to be an im-
portant water resource aquifer [Gillis, 1976]. Martin Marietta's rock quarry near 96thStreet
and Hazel Dell has been excavated approximately 140ft into the limestone and beneath
approximately 30 - 35 ft of overlying outwash sands and gravel. Quarry operators report
little if any seepage of groundwater from the limestone [Gillis, 1976]. For the purpose of
this study, groundwater flow in the bedrock formations is negligible.
2.2 Hydrology
Of the 37 in of precipitation that that fall each year in Hamilton County, about 12injyr
(35%) flow directly into surface waters. The remaining water is returned to the atmosphere
as evaporation and transpiration or infiltrates the ground and becomes groundwater.
The perennial streams near the well field have their highest average flows in the spring,
and seasonal low flow often occurs in the late fall or early winter. USGS stream flow records
indicate that in all of the streams, spring low flow (from March through May) is about two
times the low flows observed between December and February [Fenelon and Bobay, 1994].
Stream flow is composed of groundwater that is discharging from aquifers and more recent
water that is draining off the land surface during and immediately following precipitation
events.
It has been estimated that, over the entire basin, groundwater discharge into the White
River (also referred to as base flow) is about 4inchesjyear or 1 of the total stream flow
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[Wittman and Haitjema, 1995]. In the study region, the recharge rates in the outwash will
be higher than the basin average, while recharge rates in upland tills will be lower.
2.2.1 Surface water and groundwater interactions
The degree of hydraulic connection between surface streams and groundwater can have an
important effect on the source areas for wells and the well yields. There have been several
studies of the hydraulic connection between the thin outwash aquifers and the streams south
of the study area in Marion County [Meyer, 1979, Saul and Robinson, 1989]. The general
conclusion of these investigations is that the connection may vary locally but where the
aquifer is composed of coarse sand and gravel, there is little resistance between the White
River and the alluvial aquifer.
2.2.2 Potentiometric data
The water levels in the aquifers result from the hydraulic properties of each aquifer, the
pumping rates of the wells, recharge rates (or leakage rates) into or out of the system, and
the location of boundary conditions within the system. The water levels in each of the
aquifers also varies with time. During prolonged drought (such as the drought experienced
in early 1960s) annual maximum water levels declined in observation wells throughout
Hamilton County [Meyer et al., 1975]. According to the rating curve for the White River at
Nova, the stage during a major drought is 7 - 9 ft lower than the average stage.
No water-level measurements were made specifically for this report. Instead, the In-
diana Department of Natural Resources water well records and water levels reported by
Martin Marietta were used as the calibration targets for flow modeling.
3 Model development
This section describes the development of the regional and local model, the conceptual
model that was used, the code used, and the calibration data.
3.1 Model code selection
The analytic element model (AEM) GFLOW was used because:
1. It is suitable for modeling large domains
2. It can model base flow in surface water
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3. It can model large transmissivity contrasts accurately, e.g. at gravel pits.
A complete discussion of the theory of the analytic element method can be found in Strack
[1989] and a discussion of the practical aspects of modeling with the AEM technique is
found in Haitjema [1995].
Analytic element models do not discretize the aquifer into a grid or mesh. Instead the
hydrologist discretizes the surface-water features and defines domains of the aquifer with
similar hydraulic properties. The modeling technique forces the hydrologist to use distant
boundary conditions to generate flow in the near-field; this makes the AEM uniquely well
suited to modeling flow at large scales [de Lange, 1991, de Lange, 1996]. Unlike numerical
models the analytic element method allows the user to analytically calculate potentiometric
heads and groundwater fluxes at any point in the domain.
In AEM models, common practice is to embed regions with highly-detailed elements
in a less-detailed regional model. We have followed this approach.
3.2 Aquifer conceptualization
The conceptual model used for the groundwater flow modeling assumes a single aquifer
with an impermeable horizontal base, representing the regional unconsolidated aquifers.
In the conceptual model, the aquifers are specified in 5 categories, as shown in Figures 4
and 5, and described in Table 2. When the model was constructed in GFLOW, the various
domains were given transmissivity values such that the model matches the calibration data.
The classification scheme is described in detail below:
Regional intertill aquifer Variably connected sand and gravel deposits within thicker sur-
ficial clay till formations. Typically, the overall transmissivity and recharge rates are
low.
Thin outwash aquifer Sand and gravel in the floodplain of the White River that is buried
by 10 it or more of clay till. Intermediate values of transmissivity and recharge rate
are expected.
Thick outwash aquifer Localized, thick gravel formations in the floodplain of the White
River; may be coincident with the location of the river. High values of transmissivity
and recharge rate are expected.
Bedrock hills Localized regions within the floodplain of the White River where the bedrock
elevation is much higher than elsewhere in the floodplain. These bedrock hills can cut
12
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off much of the permeable unconsolidated deposits. These are simulated as domains
of very low transmissivity and low recharge.
Mine pit ponds Inactive gravel operations that have filled with water. These have effec-
tively infinite transmissivity and high recharge. For the purpose of the model, a trans-
missivity value that is two orders of magnitude (lOOx) the outwash transmissivity
was used.
In the model, domains of varying transmissivity and recharge were created to simulate the
various aquifer types (Figure 7).
3.3 Regional boundary conditions
The approach used in this investigation was to first model regional flow and then to add
detail near the Martin Marietta facilities. The local model used to evaluate impact was
constructed by adding local detail to the regional flow model. Consequently, the local
model contained the information obtained while modeling the regional system. The regional
model represented boundary conditions such as rivers and streams in a coarse manner, while
the aquifer system was modeled as a single, hydraulically conducting layer with locally
varying transmissivity (Figure 6). The conceptual geologic model used for the regional
analysis was based on our earlier modeling work done in central Indiana and water re-
source investigations conducted by the U.S. Geological Survey. This was all supplemented
by our own analyses of well log information obtained through the Indiana Department
of Natural Resources [Bailey and Imbrigiotta, 1982, Gray and Hartke, 1989, IDNR, 1976,
Meyer et al., 1975, Meyer, 1979, Smith, 1983].
The regional model includes all or parts of four counties in central Indiana: Hamil-
ton, Marion, Hendricks, and Hancock counties. Also included were the significant aquifer
properties, major rivers and streams, and all of the high capacity wells registered in the area
The boundary conditions in an analytic element model are not perimeter conditions
imposed by the modeler around a finite grid domain. Instead, the boundary conditions
are natural hydrologic features, such as streams and lakes, that control flow in the aquifer.
These surface-water features are provided as line-sink elements with specified heads (Figure
6). The far-field features were modeled with few, long line sinks. The line sinks used to
model distant rivers do not include the effects of entry resistance along streams. It is not
appropriate to perform detailed analyses in the far field; these elements are used only to
ensure appropriate flow conditions at the perimeter of the study domain.
13
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14
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Figure 4: Plan view of the relationships between conceptual aquifer domains.
Aquifer type Transmissivity Recharge
Regional intertill Low Low
Thin outwash Medium Medium
Thick outwash High High
Bedrock hills Low Low
Gravel pit ponds 00 High
Table 2: Aquifer classification scheme for conceptual model.
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LEGEND
WiHman Hydro Planning Associates
W.ltIl-.P..W..... P\;)--o"..C;M"F..J;:;T~
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Figure 6: Layout of wells and line sinks in the regional model.
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3.4 Local boundary conditions
The local model was used to assess both existing and future hydraulic conditions associ-
ated with groundwater pumping in the Carmel area. Specifically, the area of detail includes
Carmel Utilities Plant 4 Well Field and Martin Marietta's existing and proposed sand and
gravel and limestone mining operations in Carmel. The local model contains the informa-
tion obtained from modeling the regional system but also provides details that incorporate
calibration head points, pumping, mine operation, variable recharge rates and transmissiv-
ity, and more detailed surface-water features that include streams with variable resistance
and quarry lakes.
Since 1988, the IDNR Division of Water has required all surface water and groundwater
withdrawal facilities within the state that have a pumping capacity of 70 gpm or greater to
record and submit annual production data. This includes municipal, commercial, institu-
tional, industrial, geothermal, and irrigation facilities as well as mining operations. Since
significant pumping of an aquifer may influence both local and regional groundwater flow, a
review of registered high-capacity groundwater withdrawal facilities located within Hamil-
ton County was performed. The hydraulic significance of these pumping facilities, which
includes Carmel Utilities' twenty production wells, were evaluated in the computer model
using well elements. For the pumping rate, an average of Carmel's pumping from 1990-
2002 was calculated.
Martin Marietta reports that it currently pumps approximately 6.4 million gallons per
day (MGD) at the Indianapolis North Plant. This total includes inflow from the adjacent
thin outwash aquifer, surface runoff and any seepage from the bedrock aquifer. Of this
total, approximately 4.8MGD is estimated to be from groundwater inflow. Removal of
water at the mining operations of the aquifer will be simulated in the computer model using
a high conductivity inhomogeneity and a single line-sink with a specified head similar to
the bedrock mine floor elevation. By using this strategy, the line-sink element will tell how
much water is removed at the mine.
In the analysis of uncertainty, hydraulic parameters (recharge and hydraulic conductiv-
ity) were varied to achieve a calibrated model (sensitivity analysis). In all cases, aquifer
porosity was modeled at 20%, and the aquifer thickness was assumed to be 80 feet.
3.5 Representing mine operations in the model
In the local model, it is necessary to represent two hydrologic features that result from
mining operation: (1) active mine pits; and (2) inactive pits that have filled with water.
17
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LEGEND
0.3 0
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Wittman Hydro Planning Associates
.~FtR"SC.Ir:;er'1:.<rnirl!lCcf1s,.'ltJfrn
.
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Linesinks
Hydrology
Roads
Inhomogeneities
_ Mining ponds
D Thick outwash
_ Bedrock high
I!III Thin outwash
D Intertill
Figure 7: Aquifer domains and local boundary conditions for the current conditions near
Carmel Plant 4.
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These were simulated as follows:
Active mining operations It was assumed that the potentiometric surface at the edge of
the mine is held at the top of the bedrock by perimeter drains (as it is at the existing
Martin Marietta quarry pit). In this case, the pit is modeled using line-sink elements
with their head specified at the bedrock elevation. Since the model is based on con-
stant transmissivity in each domain, it is necessary to specify an entry resistance to
account for the thinning of the potentiometric surface where flow is unconfined near
the perimeter drains, or for a seepage face. The resistance was determined as part of
model calibration.
Inactive gravel pits These are modeled as open water, using inhomogeneity domains with
very high transmissivities (see above). In the post-mining model runs, the current
quarry pit and the proposed pit at the South Mueller property were modeled in this
manner.
In addition, the inactive gravel pit that receives water pumped from the Martin Ma-
rietta quarry pit perimeter drain will lose some water to the aquifer and the remain-
der will overflow into Blue Woods Creek. This is modeled by adding a quantity of
recharge to that pit in the model.
3.6 Potentiometric head observations
Static water levels utilized for calibrating the model were selected from existing measure-
ments reported on IDNR well logs and a number of Carmel Utilities' test well logs. Vari-
ations in the reported static water levels at any location can be attributed to one or any
combination of the following: seasonal fluctuations, long term climatic variations, different
aquifers, transient pumping conditions and the reporting of erroneous well locations and/or
static water levels by drillers. To ensure that appropriate data were used for calibration, we
used these rules:
. Only the Indiana Geological Survey (IGS) filtered IDNR database was used for IDNR
well locations. IGS has provided quality control checks on their filtered database to
reduce errors.
. Only wells completed since January 1, 1998.
. Only wells completed with depths in the range of 40 - 100 ft.
. Static water levels from wells completed in the bedrock aquifer were removed.
19
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4 Results
This section describes the approaches used to determine the effects of the proposed mine
expansion. In particular, we discuss the calibration of the model to potentiometric head
data, the scenarios used to evaluate effects, and the examination of uncertainty related to
model parameters.
4.1 Model calibration
In the model, there were several parameters that could be adjusted as part of model calibra-
tion:
. Transmissivity and recharge rates in the regional intertill aquifer, buried sand-and-
gravel aquifer, thick outwash aquifer, and bedrock hills
. Entry resistance in surface waters
. Entry resistance for the perimeter drain at the current Martin Marietta quarry pit
. Amount of water infiltrated into the inactive gravel pit where water pumped from the
Martin Marietta perimeter drain is disposed.
For calibration purposes, the Carmel Plant 4 wells were given pumping rates consistent
with their operation in 1993 (a representative year in the time period of available water-
level data). Because the modeling analysis is intended to show differences arising from the
proposed mine operation, these pumping rates were used throughout the modeling analysis,
As described above, the regional model was calibrated to match well with observed
heads from IDNR water well data that have been filtered for quality by the Indiana Geolog-
ical Survey. In addition, local head observations were derived from the potentiometric map
provided by Martin Marietta that was developed from their own monitoring wells. One flux
calibration value was also available: the estimate that 4.8MGD of groundwater is pumped
from the perimeter drain at the existing quarry pit.
The parameter values that were determined during calibration of the model (matching
both regional and local observations) are shown in Table 3.
The spatial distribution of calibration error is shown in Figure 8. Summary statistics
for the calibration results are shown in Figure 9. The "best-fit" modeled inflow into the
existing perimeter drain was 4.78MGD.
20
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LEGEND
0.3
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Calibration error
(model head-obs. head)
. <-10
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. Carmel wells
N Potentiometric contours
'\/ Roads
1\/ Rivers
D Hamilton County
Wittman Hydro Planning Associates
WaLB- R€-~o.m:.;.;t PkFllil-";; ConslA:ants
Figure 8: Results of calibration and best-fit potentiometric surface.
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Parameter
Value(s)
Intertill aquifer Transmissivity 1600ft2 jd
Intertill aquifer recharge rate 2.5injyr
Buried sand-and-gravel transmissivity 5600ft2 jd
Buried sand-and-gravel recharge rate 7.5injyr
Outwash transmissivity 24000 ft2 j d
Outwash recharge rate 10injyr
Resistance of surface waters Ranged from I - 100d
Infiltration at disposal pit 2.2M CD
Resistance of perimeter drain 2d
Table 3: Parameters for "best-fit" model.
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Figure 9: Summary calibration statistics from GFLOW.
22
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4.2 Analysis of parameter uncertainty
For each scenario in the analysis (see following sections), a sensitivity analysis for critical
parameters was performed. The following parameters were adjusted:
. Transmissivity of the thin and thick outwash aquifers was raised and lowered by 20%
. Resistance of the White River was reduced by 50%
. Resistance of the modified reach of Blue Woods Creek was reduced by a factor of
lOxin the "South Mueller active" scenario only, to examine the possible impact
should the construction of the new creek channel increase communication with the
aquifer.
For each scenario, a range of predicted values is provided for each of the indices of impact
(see below).
In addition, a composite capture zone analysis for the Plant 4 wells was performed
for each scenario. The approach used to determine the 5-year composite capture zone is
shown in Figure 10. Streamlines were traced back in time from each well for 5 years. The
streamlines for all simulations were superimposed using GIS software and the composite
capture zone was digitized manually as the polygon that enclosed all of the streamlines.
Including ponds in capture zone delineations Our model predicts that a large fraction
of the water pumped by the Plant 4 wells comes from the northernmost of three ponds (for
this discussion, we refer to the ponds as "NW", "SE", and "SW" as noted in Figure 11)
just west of the current quarry operation. Since the ponds are hydraulically connected to
varying degrees, this introduces several complex issues for capture zone delineation. We
have taken the conservative approach that if there is a possibility that one of the gravel pits
contributes to the wellfield, it should be included in the wellfield capture zone. Further-
more, we describe the ultimate sources of waters into the three ponds, for consideration in
wellhead protection planning.
Ponds SW and SE Ponds SW and SE are well connected by culverts, and according to the
data collected by Martin Marietta, the water levels in both ponds are essentially the
same. Water pumped from the collection ditches and other facilities at the quarry
operation is pumped into Pond SW. Particulate matter that is entrained in this water
settles into Pond SW, and the water then moves primarily into Pond SE, from which
it then exits via a culvert under Gray Road into Blue Woods Creek. Although most of
23
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24
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. Carmel wells
N Linesinks
N Hydrology
N Roads
D Composite
capture zone
LEGEND
Pathlines
N Calibration
N Low conductivity
N Low transmissivity
N High transmissivity
+
0.1
,
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0.1 Miles
Figure 10: Dete~mination of a composite capture zone.
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LEGEND
. Carmel wells
N Roads
_ Hydrology
Figure 11: Former gravel pit ponds that contribute water to the Plant 4 wellfield, with
identifying names.
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the water moves from Pond SW into Pond SE, some also moves into Pond NW (see
below).
Pond NW Pond NW has two sources of water: (1) inflow from Pond SW through culverts
that connect the ponds; and (2) inflow from Blue Woods Creek. Water-level data
for Pond NW and Pond SW (Table 4) indicate that the water level in Pond NW is
usually higher than the level in Pond SW, although in about 10% of the data, the level
in Pond SW is higher. This indicates that water removed from the mining operation
and runoff water in Blue Woods Creek are potential sources of contamination for the
Plant 4 wells.
From a wellhead protection standpoint, all three ponds (NW, SW, and SE) contribute water
to the Plant 4 wells. All potential sources of contamination into the ponds should be con-
sidered as part of the Plant 4 wellhead protection plan, including runoff of lawn chemicals
and spills into Blue Woods Creek, and also potential contaminants entering the pond from
the mining operation.
4.3 Reduced recharge analysis
Since little is known about the stage-discharge relationships in the surface streams near
the mine, it is not presently possible to simulate all features of the hydraulics of this system
during a major drought. Indices of impact in this report are derived from the change in water
levels or water leaving the inactive gravel pit and entering a Plant 4 well. Therefore, we have
performed one "reduced recharge" run for each scenario. In each case, the potentiometric
surface and streamlines from the Plant 4 wells are shown for the case that the recharge rates
are reduced to 1/3 of the "best-fit" calibration values.
The reduced-recharge scenarios suggest the effects on the capacity of the Plant 4 well-
field that result from reductions in recharge. Two important factors that can reduce recharge
are natural drought events and urbanization. The model does not include the effects of
drought on major surface-water levels (e.g. in the White River), so it under-predicts the ef-
fects oflong-term drought on Plant 4. However, it is likely that short-term (e.g. 1-2 month)
dry periods in summer could reduce recharge (and therefore plant capacity) significantly
for a short time. The issue of urbanization is more long-lasting. As development contin-
ues near the Plant 4 wellfield, the long-term recharge rate may be significantly reduced by
the presence of homes, streets and parking facilities, with surface-water structures handling
runoff and reducing recharge.
26
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r;;;;
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I Date I Pond NW I Pond SW I
5/22/02 NA 737.22
6/12/02 NA 736.92
8/13/02 NA 736.40
12/16/02 735.24 736.46
2/10/03 736.94 736.40
4/8/03 739.13 736.53
6/16/03 737.79 736.88
9/15/03 737.59 737.61
10/15/03 736.99 736.33
11/17/03 736.59 736.53
1/15/04 736.79 736.53
2/17/04 736.79 736.53
3/17/04 736.50 736.50
4/17/04 736.39 736.33
Table 4: Water levels in Ponds NW and SW (source: Martin Marietta Materials, Inc.).
27
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4.4 Scenarios and results
Three scenarios were perfonned, corresponding to the following:
Current The current situation
South Mueller Active The South Mueller gravel pit is fully built-out and the water table
drawn down to bedrock.
After Mining The South Mueller pit and the current quarry have been closed; they have
filled with water and become lakes.
The scenarios are discussed below. For the "South Mueller Active" and "After Mining"
scenarios, three indices of impact are provided,
1. Change (in ft) for water levels in the currently-existing inactive gravel pit ponds,
2. Change in water level at a point located between the Plant 4 wells (this is related to
the capacity of the wells),
3. Fraction of the total water pumped by the Plant 4 wells that travels from the inactive
gravel pit south of the wellfield in less than 5 years.
4.4.1 "Current" scenario
Results for the "Current" scenario are shown in Figure 12. The illustration shows the mod-
eled potentiometric surface based on best-fit model parameters and the composite 5-year
time-of-trave1 capture zone for the Plant 4 wells. Based on the sensitivity analysis, the
Plant 4 wells receive about I-half (51-55%) of their water from the inactive gravel pit south
of the wellfield. Although time-of-travel is not shown on the figure, it should be noted that
the travel time from the gravel pit to well #12 is less than 1 year.
The reduced recharge run for the current scenario is shown in Figure 13. The model
predicts that the Plant 4 wells receive 68% of their water from the inactive gravel pit south
of the wellfield.
Consideration of the new Well #22
All of the analyses presented here are based on the 1993 "representative year" pumping
rates for the Plant 4 wells. During the summer of 2004, the new Well 22 will be corning
on-line at Plant 4. We have perfonned an additional set of model runs based on current
28
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LEGEND
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Potentiometric contours
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_ Hydrology
Figure 12: Modeled potentiometric surface and composite S-year capture zone for the cur-
rent conditions.
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LEGEND
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Figure 13: Current operations for "reduce-recharge" conditions.
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conditions, but adding Well 22. Since no actual pumping data for Well 22 are available,
we assumed that in the "representative" scenario, it would pump the same amount as the
largest well in the previous runs. The composite capture zone and potentiometric head field
is shown in Figure 14.
4.4.2 "South Mueller Active" scenario
Results for the "South Mueller Active" scenario are shown in Figure 15. The illustration
shows the modeled potentiometric surface based on best-fit model parameters and the com-
posite 5-year time-of-travel capture zone for the Plant 4 wells. Based on the sensitivity
analysis, the Plant 4 wells receive about 70% (70-71 %) of their water from the inactive
gravel pit south of the well field. Although time-of-travel is not shown on the figure, it
should be noted that the travel time from the gravel pit to well #12 is less than 1 year.
The total amount of water pumped from the quarry pit and the South Mueller pit is about
7.2MGD. Of this, we reinfiltrated the same fraction as found in the calibrated model at the
gravel pit (3.3MGD), leaving about 3.9MGD (6cfs) in Blue Woods Creek.
The changes between current conditions and those when the South Mueller property is
being actively mined are shown in Figure 16. The most important value is the change in the
water levels in the wellfield: the model predicts a decline of 2.0 - 2.8 ft. This corresponds
to about 10-15% of the capacity reported in the well logs for Plant 4.
When this model is run with a very low resistance in the modified reach of Blue Woods
Creek, the results are quite different. An increased head of 0.3 ft is predicted at the well-
field, and the Plant 4 wells receive 77% of their water from the inactive gravel pit.
The reduced recharge run for the current scenario is shown in Figure 17. The model
predicts that the Plant 4 wells receive 83% of their water from the inactive gravel pit south
of the wellfield.
4.4.3 "Post Mining" scenario
After surface operations at the South Mueller property are complete, a dry reclamation plan
has been proposed. A network of drains will be incised into the bedrock surface to route
water into the ditches near the current quarry operation. The water will then be pumped into
the ponds west of the quarry. From a modeling perspective, the "post-mining" conditions
do not differ from the conditions when the South Mueller operations are active. Thus, the
"South Mueller active" scenarios are representative of the post-mining conditions.
31
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LEGEND
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Figure 14: Modeled potentiometric surface an composite 5-year capture zone for the current
conditions with Well 22.
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LEGEND
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Figure 15: Modeled potentiometric surface and composite 5-year capture zone when the
South Mueller property is actively mined.
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LEGEND
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N Linesinks
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Range of water level
a change from current
conditions (ft)
_ Hydrology
Figure 16: Change in heads between current conditions and those when the South Mueller
property is actively mined.
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LEGEND
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Figure 17: Results for "reduced-recharge" conditions when the South Mueller property is
actively mined.
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5 Conclusions
There is no single index of the "effects of mining" that captures all of the changes that could
take place once the proposed excavations are underway. Instead, we considered two types
of impacts: changes in water levels in the aquifer near the Plant 4 well field, and changes in
the source water pumped by the well field. The first of these is a measure of the reduction
in yield that results from the competition between the drinking-water wells and the mining
operations around the active pits. We examined impacts both during and after mining.
. The wellfield is significantly affected by the reinfiltration of water pumped from the
existing Martin Marietta quarry pit. Currently, about 2.2MGD of the 4.8MGD that
is pumped from the drains at the quarry pit is reinfiltrated after it is disposed at the
inactive gravel pond. The remaining 2.6MGD (4cfs) is lost from the gravel pit to
Blue Woods Creek.
. The addition of Well 22 to the current conditions increases the size of the Plant 4
wellhead protection area, particularly north and east of the wellfield.
. Additional mining could reduce groundwater levels at the well field by about 2-
3 ft while the mines are active. The amount of water pumped by a well is roughly
proportional to the drawdown in the well. Since the original pumping tests showed
about 16ft of drawdown when the wells were pumped at capacity and the modeling
predicts an additional 2 - 3 ft of decline, this translates to roughly 15% reduction in
total wellfield capacity during mining.
. Additional mining at the South Mueller property will increase the amount of water
pumped from the mine by about 50%.
. In the 20 years that the proposed mines are active there would be an increase in the
amount of drinking water that comes from the pits and ponds. Currently we estimate
that approximately one-half of the water pumped at the Plant 4 well field had been in
a pit or pond within the last five years. While the mines are active this will increase
to more than 70% of all the water in the well field.
. With reduced recharge conditions, the effects of the proposed mining will be to de-
crease water levels by 3 ft compared to reduced recharge under current conditions.
With reduced recharge there are changes in water use and stage along the river that
36
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may alter the actual conditions at the well field. The effects that we predicted are a re-
sult of reductions in regional flow from the till aquifers to the West and the increasing
importance of the White River to the East of the wells.
. If the reconstructed section of Blue Woods creek has a very good connection with the
aquifer, it may be able to supply a significant amount of water to the Plant 4 wells,
even increasing the heads in the aquifer near the wellfield.
. After mining ceases, the water levels near the wellfield will decline compared to
current conditions as a result of the loss of additional aquifer recharge at the inactive
gravel pit just south of the wellfield. The amount of water moving from the gravel pit
to the wellfield will be about one-half what it is currently.
. We recommend that a monitoring well program be initiated to evaluate the interaction
between the inactive gravel pits south of the Plant 4 wellfield and the wells. A detailed
monitoring plan is in development and will be submitted in mid-July.
37
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References
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38
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[Haitjema,1995] Haitjema, H. (1995). Analytic Element Modeling of Groundwater Flow.
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39