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COLLECTION AREA
7,N
•00 0o
1996
x XX x
1541=n
M36'
X COa.LECRTON, A.LUIJAL V R.O, SYSTEM
0
0
IN)ECUON, AIVIAL
POINTS OF COMPUANCE
GROUND-WATER HYDROLOGY FOR SUPPORT OF BACKGROUND CONCENTRATION AT THE GRANTS RECLAMATION SITE
4
GROUND-WATER HYDROLOGY FOR SUPPORT OF BACKGROUND CONCENTRATION
AT THE GRANTS RECLAMATION SITE
FOR:
HOMESTAKE MINING COMPANY OF CALIFORNIA
BY:
HYDRO-ENGINEERING, L.L.C. CASPER, WYOMING
DECEMBER, 2001
GEORGE L. AOFFMO, P.E. HYDROLOGIST
TABLE OF CONTENTS Paae Number
1.0 INTRODUCTION ....... ............................................................................. 1-1
2.0 GEOLOGIC SETTING AND AQUIFER CONNECTIONS ........................... 2-1
2.1 ALLUVIAL AQUIFER ......................................................................... 2-2
2.2 UPPER CHINLE AQUIFER ................................................................. 2-4
2.3 MIDDLE CHINLE AQUIFER ............................................................... 2-5
2.4 LOWER CHINLE AQUIFER ................................................................ 2-7
3.0 AQUIFER PROPERTIES ........ ................................................................. 3-1
3.1 SATURATED THICKNESS OF THE ALLUVIUM ..................................... 3-1
3.2 HYDRAULIC CONDUCTIVITY, TRANSMISSIV1TY AND STORAGE ....... 3-1
4.0 GROUND WATER FLOW ...... ................................................................ 4-1
4.1 ALLUVIAL ......................................................................................... 4-1
4.2 UPPER CHINLE ................................................................................ 4-2
4.3 MIDDLE CHINLE .............................................................................. 4-3
4.4 LOW ER CHINLE ........................................................................ 4-5
5.0 BACKGROUND CONCENTRATIONS AND EXISTING STANDARDS .......... 5-1
5.1 SITE ST ANDARDS ........................................................................... 5-1
5.2 BACKGROUND WATER QUALITY ...................................................... 5-2
6.0 WATER QUALITY ....... ........ .. .•.......... .................................... .... 6-1
6.1 WATER TYPE ..................................... 6-1
6.2 RESTORATION AREAS ............................... 6-6
7.0 REFERENCES ........................................ 7-1
i
TABLE OF CONTENTS
FIGURES
Paae Number
2-1 TYPICAL GEOLOGIC CROSS SECTION SHOWING CHINLE CONNECTION WITH THE ALLUVIAL AQUIFER ............................................... 2-9
2-2A ALLUVIAL WELL LOCATIONS AND SATURATED LIMITS (WEST AREA) ....... 2-10
2-2B ALLUVIAL WELL LOCATIONS AND SATURATED LIMITS .............................. 2-11
2-3A ELEVATION OF THE BASE OF THE ALLUVIUM (WEST AREA), FT-MSL .......... 2-12
2-3B ELEVATION OF THE BASE OF THE ALLUVIUM, FT-MSL ............................... 2-13
2-4 LIMITS OF UPPER CHINLE AQUIFER AND WELL LOCATIONS ...................... 2-14
2-5 ELEVATION OF THE TOP OF THE UPPER CHINLE AQUIFER, FT-MSL ........... 2-15
2-6 LIMITS OF MIDDLE CHINLE AQUIFER AND WELL LOCATIONS .................... 2-16
2-7 ELEVATION OF THE TOP OF THE MIDDLE CHINLE AQUIFER, FT-MSL ....... 2-17
2-8A LIMITS OF LOWER CHINLE AQUIFER AND WELL LOCATIONS (W EST AREA) .......................................................................................... 2-18
2-8B LIMITS OF LOWER CHINLE AQUIFER AND WELL LOCATIONS ..................... 2-19
2-9A ELEVATION OF THE TOP OF THE LOWER CHINLE AQUIFER (W EST AREA), FT-MSL ............................................................................. 2-20
2-9B ELEVATION OF THE TOP OF THE LOWER CHINLE AQUIFER, FT-MSL .......... 2-21
3-1A SATURATED THICKNESS OF THE ALLUVIAL AQUIFER (W EST AREA), 2000, FEET ......................................................................... 3-4
3-1B SATURATED THICKNESS OF THE ALLUVIAL AQUIFER, 2000, FEET ............... 3-5
3-2A HYDRAULIC CONDUCTIVITY (PERMEABILITY) FOR THE ALLUVIAL AQUIFER (W EST AREA), FT/DAY ............................................................... 3-6
3-2B HYDRAULIC CONDUCTIVITY (PERMEABILITY) FOR THE ALLUVIAL AQ UIFER, FT/DAY ...................................................................................... 3-7
3-3 TRANSMISSIVITY FOR THE UPPER CHINLE AQUIFER, GAL/DAY/FT .............................................................................................. 3-8
3-4 TRANSMISSIVITY FOR THE MIDDLE CHINLE AQUIFER, GAL/DAY/FT ........... 3-9
4-1A WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, (W EST AREA) 2000, FT-MSL ...................................................................... 4-7
ii
4-1B WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, 2000, FT-M SL .................................................................................................... 4-8
4-1C WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, (WEST AREA) 2000, FT-MSL, OVERLAY ...................................................... 4-9
4-1D WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, 2000
FT-MSL, OVERLAY .................................................................................. 4-10
4-2 WATER-LEVEL ELEVATIONS FOR THE UPPER CHINLE AQUIFER, 2000, FT-MSL ......................................................................... 4-11
4-3 WATER-LEVEL ELEVATIONS FOR THE MIDDLE CHINLE AQUIFER, 2000, FT-MSL ......................................................................... 4-12
4-4A WATER-LEVEL ELEVATIONS FOR THE LOWER CHINLE AQUIFER (WEST AREA), 2000, FT/MSL .................................................... 4-13
4-4B WATER-LEVEL ELEVATIONS FOR THE LOWER CHINLE
AQUIFER, 2000, FT/MSL ......................................................................... 4-14
5-1 2000 BACKGROUND GROUND-WATER QUALITY ......................................... 5-6
6-1 STIFF DIAGRAM COMPARISON FOR UPGDRADIENT ALLUVIAL W ATER QUALITY .................................................................................... 6-10
6-2 STIFF DIAGRAM COMPARISON FOR UPPER CHINLE W ATER QUALITY .................................................................................... 6-11
6-3 Ca, Na, HCO3 AND Cl CONCENTRATION COMPARISON FOR
THE ALLUVIAL W ELLS ............................................................................. 6-12
6-4 Ca, Na, HCO3 AND Cl CONCENTRATION COMPARISONS FOR
THE UPPER CHINLE AQUIFER, IN mg/l, .................................................... 6-13
6-5 STIFF DIAGRAM COMPARISON FOR MIDDLE CHINLE WATER QUALITY EAST OF WEST FAULT .................................................. 6-14
6-6 Ca, Na, HCO3 AND Cl CONCENTRATION COMPARISONS FOR THE
MIDDLE CHINLE AQUIFER, IN mg/l ......................................................... 6-15
6-7 STIFF DIAGRAM COMPARISON FOR MIDDLE CHINLE WATER QUALITY W EST OF WEST FAULT ............................................................. 6-16
6-8 STIFF DIAGRAM COMPARISON FOR LOWER CHINLE WATER
Q UALITY ................................................................................................ 6-17
6-9A Ca, Na, HCO3 AND CI CONCENTRATION COMPARISONS FOR THE
LOWER CHINLE AQUIFER, (WEST AREA), IN mg/l .................................... 6-18
6-9B Ca, Na, HCO3 AND Cl CONCENTRATION COMPARISONS FOR THE
LOW ER CHINLE AQUIFER, IN mg/l .......................................................... 6-19
iii
6-10A U AND Se RESTORATION AREAS FOR THE UPPER CHINLE, OVERLAY ........ 6-20
6-10B TDS, S04, U AND Se CONCENTRATION COMPARISONS FOR THE UPPER CHINLE AQUIFER, IN mg/I ..................................................... 6-21
6-11A Mo RESTORATION AREA FOR UPPER CHINLE, OVERLAY ........................... 6-22
6-11B Mo, N03, Ra226 AND Ra228 CONCENTRATION COMPARISONS FOR THE UPPER CHINLE AQUIFER, IN mg/I, except for radium in pCi/I .............. 6-23
6-12A U AND Se RESTORATION AREAS FOR THE MIDDLE CHINLE, OVERLAY ...... 6-24
6-12B TDS, S04, U AND Se CONCENTRATION COMPARISONS FOR THE MIDDLE CHINLE AQUIFER, IN mg/I ......................................................... 6-25
6-13 Mo, N03, Ra226 AND Ra228 CONCENTRATION COMPARISONS FOR THE MIDDLE CHINLE AQUIFER, IN mg/I, except for radium in pCi/I ............ 6-26
6-14A TDS, S04, U AND Se CONCENTRATION COMPARISONS FOR THE LOWER CHINLE AQUIFER (WEST AREA), IN mg/I ..................................... 6-27
6-14B U RESTORATION AREA FOR LOWER CHINLE, OVERLAY ........................... 6-28
6-14C TDS, S04, U AND Se CONCENTRATION COMPARISONS FOR THE LOW ER CHINLE AQUIFER, IN mg/I .......................................................... 6-29
6-15A Mo, N03, Ra226 AND Ra228 CONCENTRATION COMPARISONS FOR THE LOWER CHINLE AQUIFER (WEST AREA), IN mg/I, except for radium in pCi/I ......................................................................................... 6-30
6-15B Mo, N03, Ra226 AND Ra228 CONCENTRATION COMPARISONS FOR THE LOWER CHINLE AQUIFER, IN mg/I, except for radium in pCi/I .............. 6-31
TABLES
2-1 BASIC WELL DATA FOR GRANTS SITE BACKGROUND ALLUVIAL
W ELLS ...................................................................................................... 2-3
2-2 BASIC WELL DATA FOR GRANTS SITE FAR UPGRADIENT WELLS ................. 2-3
5-1 GRANTS PROJECT WATER-QUALITY STANDARDS AND BACKG RO UN D ........................................................................................... 5-2
5-2 BACKGROUND MONITORING PERIOD AND FREQUENCY .............................. 5-3
iv
1.0 INTRODUCTION
This document is supporting documentation to Homestake Mining Company's (HMC)
application to amend the site standards listed in license number SUA 1471, Condition
35B. The following information presents the ground-water hydrology at the Grants
reclamation site relative to background water quality as revised in October of 2001.
The ground-water hydrology of the San Mateo alluvium at the Grants site was initially
defined in 1976. The results of the ground-water restoration program have been defined
in numerous ground-water monitoring reports for this site. The Corrective Action
Program (CAP), for the Nuclear Regulatory Commission (NRC), presents the definition of
the restoration program.
This information presents supporting data developed with details presented on the
geologic setting and aquifer connection, aquifer properties, ground-water flow and water
quality for the alluvial and Chinle aquifers. Background concentrations that are
representative of this site are discussed relative to the ground-water quality in each
aquifer. The figures presented in this report are numbered by the major section and
located after the text of each section. The tables in this report are presented adjacent to
where they are first referenced.
1-1
2.0 GEOLOGIC SETTING AND AQUIFER CONNECTIONS
Tailings at the Grants site are located on top of the alluvium and therefore the alluvial
aquifer is the most important ground-water system relative to the Grants site. The
surface geology and structure contours are presented on United States Geological Survey
(USGS) quadrangle topographic maps. Geologic maps and other geologic information
were compiled and presented by New Mexico Bureau of Mines and Mineral Resources
(NMBM) and USGS reports on the area. These reports have been used in defining the
geologic setting at this site but are not necessary for the background review.
The uranium ore bearing rocks that have been mined in this area outcrop in the San
Mateo drainage system and contain significant natural concentrations of uranium and
selenium. Therefore, the alluvial material would be expected to contain above normal
concentrations of uranium and selenium that are typically present in uranium deposits.
The Chinle Formation forms the base of the alluvial aquifer at the Grants site. The Chinle
Formation also contains some natural uranium and selenium concentrations. Therefore,
the geologic setting has significantly affected the background water quality at this site.
The hydrologic conditions in this area have been defined by New Mexico State Engineer
(NMSE), USGS and NMBM reports on the area. Ground-water conditions for the Grants
site have been defined in previous documents submitted to the NRC and typically
referenced in the annual reports on the site. These hydrologic reports have been used in
developing the hydrologic conditions presented in this report at the Grants site and are
not necessary for the background review and therefore not included in this submittal. The
Grants project site exists on the San Mateo alluvial system. The San Mateo alluvial
system follows the San Mateo alluvium and drainage system and extends from northeast
of the site to the south and west. Bedrock material exists on the surface to the northeast
and southeast sides of the alluvial material. Figure 2-1 shows a typical cross section at
the Grants site with saturated alluvium shown in red.
2-1
The Chinle Formation, which is a massive shale (approximately 800 feet thick) at the
tailings site, exists below the alluvium. The Chinle shale is a very good aquitard and
greatly restricts movement vertically from the alluvial aquifer. A few sandstones exist
within the Chinle shale, which form bedrock aquifers in this area. The cross section
shows the Upper Chinle sandstone in blue and shows where the Upper Chinle sandstone
subcrops against the alluvial aquifer forming a direct connection between these two
ground-water systems. The second major sandstone in the Chinle Formation has been
named the Middle Chinle sandstone. This sandstone is shown in magenta in the cross
section and also subcrops against the alluvium further south. In this cross section a third
permeable zone within the Chinle shale has been defined and is called the Lower Chinle
aquifer. This zone consists mainly of fractured shale and is therefore highly variable
depending on secondary permeability developed in the shale. The Lower Chinle aquifer is
not used very much in this area due to its depth and naturally poor water quality. A few
wells are completed in the Lower Chinle aquifer due to the lack of existence of the
alluvial, Upper or Middle Chinle aquifers in some areas. The San Andres aquifer exists
below the Chinle Formation as is the regional aquifer in this area. The San Andres is not
discussed in this report because it has not been impacted by Homestake tailings seepage.
2.1 ALLUVIAL AQUIFER
This subsection presents the geologic setting and well completions for the alluvial aquifer.
The basic well data for the background alluvial wells at the Grants site are presented in
Tables 2-1 and Tables 2-2. The annual reports present the basic well data for all other
wells at the site. Annual reports are not presented in this submittal because they were
previously submitted to the NRC and are not required for this analysis. Figures 2-2A and
2-2B show the location of the alluvial wells that have been used to define the ground
water conditions in the alluvial aquifer at the Grants site. Figure 2-2B shows the locations
of the nine alluvial background wells, which are listed in Table 2-1 north of the Large
Tailings. Figure 5-1 also presents the locations of the nine background wells and
locations
2-2
TABLE 2-1. BASIC WELL DATA FOR GRANTS SITE BACKGROUND ALLUVIAL WELLS
WELL NORTH. EAST. NAME COORD. COORD.
WELL DEPTH (FT-MP)
CASING DIAM (iN)
WATER LEVEL DEPTH ELEV.
DATE (FT.MP) (FT.MSL)
MP ABOVE
LSD (FT)
DEPTH TO BASE OF
MP ELEV. ALLUVIUM (FT-MSL) (FT-LSD)
ELEV. TO CASING BASE OF PERFOR
ALLUVIUM ATIONS SATURATED (FT-MSL) (FT-LSD) THICKNESS
DD ND P P1 P2 P3 P4 0 R
1546989 1545927 1546691 1547017 1546555 1546159 1546504 1548693 1550372
488943 494872 491058 491060 490912 490785 491899 482153 494514
78.5 70.0
109.1 105.0 105.0
95.0 92.0 98.3 86.3
4.0
4.0 4.0
6.0 6.0
5.0 5.0 4.0 4.0
04/00/200 08/02/200 11/28/200 11/28/200 12/04/200 03/08/200 03/08)200 03/14/200 05/11/200
57.96 47.67 53.24 55.75 61.41 66.91 85.77 50.11 43.51
6534.63 6545.22
6534.02
6536.72
6528.38
6523.04
6503.75
6543.71
6560.52
1.9 1.1
1.7
0.8
0.9 2.2 3.6 2.3 0.3
6592.59 6592.89
6587.26
6592.47
6589.79
6589.95
6589.52
6593.82
6604.03
83 65
107 105 105 85 84
100 95
6507.7 A40-80 6526.8 A50-70 6478.6 A82-112 6486.7 A60-405 6483.9 A60-105
6502.8 A55-95 6501.9 A52-92 6491.5 A72-102 6508.7 A60-90
Note: A = Alluvial Aquifer M = Middle Chinle Aquifer T = Talrmgs Aquifer * = Well Abandoned
? = Uncertain Identity
TABLE 2-2. BASIC WELL DATA FOR GRANTS SITE FAR UPGRADIENT WELLS
WELL WELL NORTH. EAST. DEPTH NAME COORD. COORD. (FT-MP)
CASING DIAM ON)
WATER LEVEL DEPTH ELEV.
DATE (FT-UP) (FT.MSL)
MP ABOVE
LSD (FT
DEPTH TO BASE OF
MP ELEV. ALLUVIUM (FT-MSL) (FT-LSD)
ELEV. TO CASING BASE OF PERFOR
ALLUVIUM ATIONS (FT-MSL) (FT-LSD)
1555500 500850 1552350 499600 160.0 1555800 496900 1555400 495600 1555200 492500 1560400 498300 81.0 A = Alluvial Aquifer M = Middle Chinle Aquifer T = Tailings Aquifer
= Well Abandoned ? = Uncertain Identity
6.0 05/09/200 4.0
7.0 5.0 6.0 5.0
05/09/200
05/10/200 07/12/200
40.06 6601.94 1.4 - - 0.0
38.60
53.00
25.70
6585.40
6568.70
6631.30
0.7 1.9
1.7 0.5
6642.00 6625.00 6627.60 6624.00 6621.70 6657.00
- *-. A
.. A45-70
- -A- -A- -A-
of the six far upgradient wells which are listed in Table 2-2. Figures 2-2A and 2-2B
present the current operation of injection and collection wells and is subject to change
with this dynamic restoration program. The limits of the alluvial aquifer are shown by
delineating the area where the alluvium is not saturated by the green dotted pattern.
2-3
26.9 18.4
55.5
50.1
44.5
20.3
1.8
52.2
51.8
0914 0916 0920 0921 0922 0950
Note:
SATURATED THICKNESS
Homestake has drilled nearly 500 wells at the Grants site. The logs from these wells and
residential wells not owned by Homestake have defined the base of the alluvium in detail.
Figures 2-3A and 2-3B present the base of the alluvial contours, which show that an
alluvial channel runs through the western portion of the Large Tailings and turns to the
southwest near the southwest corner of the Large Tailings. The base of the alluvium
contains contours of higher elevations in eastern Murray Acres, which extend back to the
northeast toward the Small Tailings pile. This area tends to decrease the amount of
alluvial water flowing in this area. The edge of the alluvial aquifer is defined where the
base of the alluvium is equal to the water-level elevation. The green line and green
dotted pattern shows where the alluvium is not saturated and is the limits of the alluvial
aquifer. The San Mateo alluvium joins the Rio San Jose alluvium in the western portion
of Section 28. The southern channel joins the Rio San Jose in the eastern portion of
Section 4.
2.2 UPPER CHINLE AQUIFER
The Upper Chinle aquifer is important to this site because direct connection between this
aquifer and the alluvium exists in the tailings area. The rate of water from the alluvium
into the Upper Chinle aquifer is important in the subcrop areas. The Upper Chinle aquifer
is not as important as the alluvial aquifer, but the ground-water hydrology conditions for
this aquifer are important with respect to potential discharge from the tailings.
The Upper Chinle aquifer is the uppermost sandstone in the Chinle Formation and is
shown in blue in Figure 2-1 on the typical cross section. The Upper Chinle Sandstone
subcrops against the alluvial aquifer in some areas of the project site. Figure 2-4 shows
the location of the typical cross section A - B (Figure 2-1).
The limits of the Upper Chinle aquifer are also shown on Figure 2-4. The green pattern
shows where the Upper Chinle Sandstone exists between the two faults with Chinle shale
above the Upper Chinle Sandstone. The Upper Chinle does not extend to the west of the
West Fault but subcrops against the alluvial aquifer on its western and southern borders.
2-4
I
The crosshatched blue pattern shows where the Upper Chinle exists east of the East Fault
with the shale above the sandstone. The red pattern shows where the Upper Chinle
aquifer subcrops against the alluvium and a crosshatched red pattern shows where the
alluvium is saturated over the subcropped Upper Chinle Sandstone. Figure 2-4 shows the
locations of the Upper Chinle wells while basic well data for the Chinle wells is presented
in annual reports.
The top of the Upper Chinle aquifer is the most important geologic feature of the Upper
Chinle Sandstone because the elevation of this unit and the base of the alluvial aquifer
define where these two aquifers are in direct connection. Two faults exist in the area of
the Grants site and are significant in definition of the Upper Chinle structure. Numerous
cross sections have been developed to correlate geophysical logs in Upper Chinle drill
holes and wells. These cross sections were used in developing these structure maps.
Figure 2-5 presents the elevation of the top of the Upper Chinle aquifer. This figure
shows that the Upper Chinle Sandstone between the two faults generally dips to the east.
The general dip is also to the east, east of the East Fault. The structure on the south
side of the project area turns and dips to the northeast at a steeper gradient, which
causes the sandstone to subcrop in the area of southern Felice Acres with the alluvial
aquifer.
2.3 MIDDLE CHINLE AQUIFER
The Middle Chinle aquifer is important to this site because direct connection between this
aquifer and the alluvium exists in the south side of Felice Acres. The Middle Chinle
aquifer is not as important as the alluvial aquifer, but the ground-water hydrology
conditions for this aquifer are important with respect to restoration of low concentrations
in the Felice Acres area in the Middle Chinle aquifer. The rate of ground-water flow from
the alluvium into the Middle Chinle is also important in the subcrop areas.
The Middle Chinle aquifer is generally the thickest of the sandstones in the Chinle
Formation. Figure 2-1 shows a typical cross section of the bedrock aquifers in this area.
2-5
This figure shows Chinle shale existing between the Upper Chinle and the Middle Chinle
Sandstones. The Middle Chinle Sandstone subcrops against the alluvial aquifer in some
areas of the project site.
The limits of the Middle Chinle aquifer are shown on Figure 2-6. The light blue pattern
shows where the Middle Chinle Sandstone exists between the two faults with Chinle shale
above the Middle Chinle Sandstone. The Middle Chinle extends to the west of the West
Fault in a limited area. This area is shown in dark blue. The red pattern shows where
the Middle Chinle exists east of the East Fault with the shale above the sandstone. The
brown pattern shows where the Middle Chinle aquifer subcrops against the alluvium and
a crosshatched brown pattern shows where the alluvium is saturated over the
subcropped Middle Chinle Sandstone. Figure 2-6 shows the locations of the Middle Chinle
wells.
Figure 2-7 presents the structure on top of the Middle Chinle sandstone. This structure
map shows the elevation of the top of the Middle Chinle sandstone on each side of the
two faults in the area of the Grants tailings and the displacement of these sandstones.
This structure map was developed in the same manner as the Upper Chinle sandstone
structure map. The Middle Chinle sandstone also dips at a steeper rate in southern Felice
Acres, which causes the Middle Chinle sandstone to subcrop against the alluvium on the
south side of Felice Acres. This allows a direct connection between the Middle Chinle and
alluvial aquifers. Multi-well pump tests in the Middle Chinle aquifer have shown that all
three of the Middle Chinle aquifer zones in this area act as separate aquifers except for
the Middle Chinle aquifer near the southern end of the East Fault where the displacement
of this sandstone ceases.
The Upper and Middle Chinle limits and elevation maps show where the Upper and Middle
Chinle sandstones are in direct connection with the alluvial aquifer. Additional
connections have been formed by residential wells that were not properly sealed. These
connections allow the alluvial aquifer and the associated Chinle aquifer to act as one
2-6
ground-water system near the areas of the subcrops. The alluvial aquifer has changed
the water quality in the Chinle sandstone aquifers near the subcrop areas due to this
direct connection.
2.4 LOWER CHINLE AQUIFER
The Lower Chinle aquifer is important to this site because direct connection between this
aquifer and the alluvium exists to the southwest of the site in its subcrop area. The
Lower Chinle aquifer is not as important as the Middle Chinle aquifer, due to less use and
generally a natural poorer quality of water.
The Lower Chinle aquifer is the permeable zone in the lower portion of the Chinle
Formation. Secondary permeability in this portion of the Chinle shale is adequate in
some locations to allow this zone to be an aquifer. Figure 2-1 shows a typical cross
section of the bedrock aquifers in this area. This figure shows the Lower Chinle aquifer
not being continuous due to the lack of permeability in some areas. The Lower Chinle
aquifer subcrops against the alluvial aquifer in some areas to the southwest of the project
site.
The limits of the Lower Chinle aquifer are shown on Figures 2-8A and 2-8B. The red
pattern shows where the Lower Chinle aquifer exists east of the West Fault with Chinle
shale above the Lower Chinle zone. The Lower Chinle aquifer is connected on both sides
of the East Fault south of the area where this fault ceases. Therefore, in the main area
of interest in the Lower Chinle, the aquifer is one unit on both sides of the East Fault.
The Lower Chinle does extend to the west of the West Fault and is shown with the blue
crosshatched pattern. The Lower Chinle subcrops against the alluvial aquifer in the
orange pattern. The crosshatched pattern shows where the Lower Chinle aquifer
subcrops against saturated alluvium. Figures 2-8A and 2-8B show the locations of the
Lower Chinle wells. Homestake drilled more than half of the Lower Chinle wells (all of
the CW wells and well 853), for definition of this aquifer and only a few of the 12
remaining wells are routinely used as a water supply.
2-7
The top of the Lower Chinle aquifer is the most important geologic feature of the Lower
Chinle because the elevation of this unit and the base of the alluvial aquifer defines
where these two aquifers are in direct connection. Two faults exist in the area of the
Grants site and are significant in definition of the Lower Chinle structure. Numerous
cross sections have been developed to correlate geophysical logs in Lower Chinle drill
holes and wells. These cross sections were used in developing these structure maps.
Figures 2-9A and 2-9B present the elevation of the top of the Lower Chinle aquifer.
These figures show that the Lower Chinle between the two faults generally dips to the
east near the tailings. The general dip is also to the east, west of the West Fault near
the tailings. The structure on the south side of the project area turns and dips to the
north-northeast at a steeper gradient, which causes the unit to subcrop in an area in
Sections 3, 4, 28 and 33 with the alluvial aquifer.
2-8
A4
UPPER CHINLE SUBCROP
CHINLE SHALE
CHINLE SHALE
CHINLE SHALE
B
6580
6540
6500
6460
6420
6380
6340
6300
6260
6220
6180
6140
6100
6060
6020
D:\R13\HMC\XSECI3 Ih 12/10/01
FIGURE 2-1. TYPICAL GEOLOGIC CROSS SECTION SHOWING CHINLE CONNECTION WITH THE ALLUVIAL AQUIFER
2-9
-1545500
1535500
-- LEGEND--
le296'
ALLUVIAL WELL
;A'? 4. , "e
Stq
OFFSET WELL
eo IRRIGATION SUPPLY WELL
RLUVM MU~L M~LI2045' 27! S•". . . - . -...-.. ".q 2550..:.' - oo,
47 -400 25048;4004.
SCALE: 1 "= 1600' HOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-I1&12-N-RANGE-10-V DATE: 08/16/01
FIGURE 2-2A, ALLUVIAL WELL LOCATIONS AND SATURATED LIMITS I0OoowQL LJU
(WEST AREA). aae 2-i.
Ifoet S
Vh
tS
SO.
b4.1- b".
* 4'1
a
29326 38"-133
Sto
0C
eo
.4e
.o
top
21,
28
11500' 3175'
1545500
2-2 COUNTY ROAD 63 J 22.23 23.24
27 27'26 2\y. ,25
.~ t ~LARGE-TAILINGS-PILE 4P ,•-v ••(RECLAMATION IN PROGRESS)
*~~e . 10 -s
PLESN A Y*• • % IEVAP OND
.. *< • ..•i
2+ LE
ACRE ---- +•
PLEI4IATO SUPPLYAL WELLPU4E
ESTFE 0 ABNDNE WELL
Crj*~~~VA PONSONCOPIAC
S• i . ! iNO.ii1
Ii~8.e 4541400
N IRIATOpSPLYWL
SCLE e",10' HtETK-ILAD-DAETPOETE GAT- -ONSI-12 -N-RANG-1NW DATE: 08/7/0Lb
FIUE2-B LUVA-EL OAIOSADSAUAE LCIMITS COLLECTON WELL
lbg 26 2 -1
:1 U, R,+ LA, .... IM. 34,,-- 35 35'L36
PROEC7S 001-0
FIGUE 2-2B ALUVIA WEL LCATONS N]]SATRAT]] IMAITNSUPL pW~ELL-
34: w
2 3
6-6N 0 6470
3 0
0 0
610
6' \ \
P-96 ' OFFSET WELL
- ALLUVIAL AQUIFER AQSENT0
v 045' 3
SCALE: 1 "1600' 1HOMESTAKE-MILL-ANDl-AflJACENT-PROPERTIES GRANT S- NM--TOWNSHIP-l1&l2-N-RANOE-lO--%
FIGURE 2-3A, ELEVATION OF THE BASE OF THE ALLUVIUM (WEST AREA), IN FT-MSL
LOBO ALLUVIUM
-6510 CONTOUR AND LABEL
DEPTH OF ALLUVIUM FT-MSL
r 0 8400487400 ALLUVIAL AQUIFER ABSENT
SCALE: 1"=1 600' HOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TO]WNSHIP-l1&12-N-RANGE-10-V I DATE: OB/17/01
FIGURE 2-3B. ELEVATION OF BASE OF THE ALLUVIUM, pdoJs\2000gO01
IN FT-MSL -. P-,•
WEST " FALLT/
/
/
//
/
//
/
/
/ BROADVIE ACRES
WESTERN LIMIT OF UPPER CHINLE
[4
UPPER CHINLE WEST OF EAST FAULT WITH SHALE ABOVE SANDSTONE
\, . \ , -K> ..
K;; \\
UPPER CHINLE EAST OF EAST FAULT WITH SH-ALE ABOVE SANDSTONE
-- LEGEND--
SUBCROP OF UPPER CHINLE ALLUVIUM OVERLIES SANDSTONE
UNSATURATED ALLUVIUM
SATURATED ALLUVIUM
485400 487400 / / 4809400
A-B LOCATION OF TYPICAL GEOLOGIC CROSS SECTION
" CWI8
"S CW13 C~ VE
UPPER CHINLE
UPPER CHINLE
UPPER CHINLE
OFFSET WELL
WELL
INJECTION
COLLECTION
SCALE: 1-=1600' HOMESTAKE MILL-AND-ADJACENT-PROPERTIES GRANTS-NM TOWNSHIP l1&12 N-RANGE-10-VI DATE: 12/07,
FIGURE 2-4, LIMITS OF UPPER CHINLE AQUIFER AND WELL LOCATIONS
fl\RI3\flO\UPI 800
*page 2-14
C6a?
WEST FAULT/
/
/
/
//
//
/
/
ACRES
WESTERN LIMIT OF UPPER • CHINLE
SUBCROP OF UPPER CHINLE ALLUVIUM OVERLIES SANDSTONE
UNSATURATED ALLUVIUM
SATURATED ALLUVIUM
4a5400 48740t
-- LEGEND--
// 4e8,40
6381 -6440
eCW1 4
X
* CV13s * CW13
1995 DATA
CONTOUR AND LABEL
NON-UPPER CHINLE WELL
TEST HOLE
UPPER CHINLE WELL
UPPER CHINLE INJECTION
UPPER CHINLE COLLECTION
OFFSET WELL
DATE: 12/07/01SCALE: 1`"1600' 1 HflESTAKE-MILL-AND-ADJACENT PROPERTIES GRANTS-NM TOWNSHIP-1T&h2-N-RANGE-1D-V I
FIGURE 2-5L ELEVATION OF THE TOP OF THE UPPER CHINLE, AQUIFER, IN FT MSL
fl\RI3\HMC\UAl 600
caT- 2-15
co3
4
MIDDLE CHINLE WEST OF WEST FAULT WITH SHALE ABOVE SANDSTONE
COUNTY ROAD S3
/
/
MIDDLE CHINLE BETWEEN FAULTS WITH SHALE EAST
AflOVE SANDSTONE
Ap Ml
SMIflfLE CHINLE EAST
ElF LAST FAULT WITH ,SHALE ALVE SANDSTONE.
• iiiiiiiiiil~iii~iiPiIL
S![!~ii~~ii~~i)i!/7' EG N
SUBCROP OF MIDDLE CHINLE ft Q. MIDDLE CHINLE WELL ALLUVIUM OVERLIES SANDSTONE
EE1Z] mZZ T-.S MIDDLE CHINLE INJECTION UNSATURATED SATURATED ,
ALLUVIUM ALLUVIUM I27'
4B5400 487400 49400 DFFSEI WELL
SCALE1 I 600' 1UNMESTAKE MILL-AND-ADJACENT-PROPERTIES SANTS-NM-TOVNSHIP-II&t2-N-RANGE-I0-I DATE. 12/08/01
FIGURE 2-6, LIMITS OF MIDDLE CHINLE AQUIFER D\R,•kH1c I•ro AND WVELL LOCATIONS , 2-16
Lo/
ZERO SATURATION OF MIDDLE CHINLE
I
01 CT
K
-- LEGEND--
6257 849 x
6231 -6500
OCW18
1995 DATA CONTOUR AND LABEL
NON-MIDDLE CHINLE WELL
MIDDLE CHINLE WELL
UNAURTD AURTD, MIDDLE CHINLE INJECTION UNSATURATED SATURATED
ALLUVIUM ALLUVIUM x X TEST HOLE
485400 487400 489,400 270 'OFFSET WELL
SCALE: 1'=-1600' I HOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-1&12-N-RANGE-10-W I DATE: 12/09/01
FIGURE 2-7, ELEVATION OF THE TOP OF THE MIDDLE CHINLE D\R13"HMC\MIM600 th
AO ITFFP. FT-M5II page 2-17
4
0
29 28 32-33
±
-- LEGEND--
LOWER CHINLE WELLS
OFFSET WELL
LOWER CHINLE S.----. EAST OF WEST FAULT- '
WITH SHALE AOVE ...
..ER.EA..LE..ZONE
UNSATURATED ALLUVIUM
SATURATED ALLUVIUM
.1541500
C')
296'
NOTEs ALL Mo DATA <0.03 , 7140, 481400 SCALE: 1"=1600' HOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TDIWNSHIP-11&12-N-RANGE-10-W( DATE: 12/09/01
FIGURE 2-8A, LIMITS OF LOWER CHINLE AQUIFER AND WELL ,D\Rm3\HMc\Lv1600
LOCATIONS (WEST AREA) page 2-i8
E. ....... .........................
WITH SHALE ABOVE T :...... ....::. ... .. ...... . ......... •v v v~ • •v ..v V v~ : .V v V~~~v v v~ •...............•..........=.......... ...................... :..•: .> > =i•`` . :.. .. .,, ..... ....,- .,-......, ..-.-.-.-........ , -.-... ....... .. ..... . .-, .. ..-.- , , -. , ., , . , ....:...:.--- -:..
LARGE TAILNGSPIL
-.-' ... --- ' " .. ...... ... " " " *- ' -... ... .. ......... ... .......' .• .. . ... ... . . .. . . . .. . . . .. .. . .. . .... .. . .. . . . . . . . . . .. .
WESTAAT1 OF WEST FAULT
:!i::il~iii•>>>>--> '7 ..........................-...v............... ~:)i~::)i~~~ii:'>7K<>>>>>>>>>>
~. . . . . . . . . . . ............ . . . . . . .. . . . . ...........''. .' .". . . . .
~~~~~~~~~~~~~~~~~. . ,' .' '". . . . . .. ." '° . ,' ' , , ,,lI I . . . . . . . . . . ... . . . . . . . .. . . . ., . . . S. ................ *.. ...................... ...... S......... . ...... .,. .. , , .. , ,.,,...,,.....,.... ..$ .... $...L .. .. . . . . . . . . . . . . . . . .
=. " ' '. : ', j . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . . . . ., , . . , ' ', '. , . . ' .' .' .' ,L . '..... . . . . . . .. . . . . . . . . . . . .. . . . . .
.'.'.'.'.'.'%','.'.'.',.'.'.'.'.',''........,. .. .. . .. .. . .. .. . .. . ,'.....'....
i iii 1 :iiii: iii> i> > : . . .............. v.v.....:.v... v.v.v.. v ~ ~~..> ..... . ........ . ... . . > ::i:=: = iiiiii:i:i :iiiiii =i•==
~~~~~~~~~~.. ............ ...::::::::::::::::::::::::::::::::::::: :: :: : :: : : : : ,. .. .. .. .. . .. .................... ...........ii i)i~i i i i i i i S. . .. . $ . .. . . . . . , . . ., . . . .$ . .. . . . . . .. .. . . . . . . . . . .
•~~~. . . . . . .. .. .. .. ... . . . . . . . .. . . . . . . . . .. ... ..°'. , -:. .::-: :- -.- :. ... .......... ...... ..........:.:. ....:. ........
>>>>.....,v ...-. v.v.........v.v. v...v..v.v... * ...... ........ S... .... .. .',' .''.'. .'%'.''.'..'$ '.', ,' $.''.''.'.o'.''.''..,......'... <->>>>>7 ....................... .... ...... -A It-".I N>)., .v ,vývv Lv...v.v.v ..v ...v~ ..v.v .v..v . v. - • ......... v.
....... :......-:....-:-.-:-:-: LOV ER CHINLE..v.v.v.-.-,
.....-.- :-.:-:-.:.::,:.:..:-::... ..S .... .......v..v ~ ..
v:.v .' .................... v-.~vvv~:.,v . .v.v.v .. v.v.v..'....... .............. .VE LIE .SAN ... TONE ..
. .. . .. . .. ... .. . .. . .. . .. .. . .. . .. . .. . ... ........ ....... .. . .. . ........" A L L U V.U ... ....VIU M. .. S. .. .. v v..~v v~~v ..v -.,-v..v .v:v~~v v:v ...-'. . . ..' .. ........-.........v.• .. .... ..>> -:. ... ....v. .. .v. ... ..-. . • I •:... .........v .......... ........ .......... .....v ....... ....v v..... ........ ... ....v... .............. ....... v.... . :• = ] • ] ] •] ] • •] • •] • •:• =] ] .] ] ] • .= : : : : :. ...............:: : : : : : : : .3 . . . .. . .* . . . . .. -. .. ..*i .........*== .. .....i i i i .v~.• v~~v~~v v..v v~v v..v v~~v~~vv~~vv~v v~ vv. .v.. ....:.•.:.:.:..:...... .. :........... .. ........ ..... ....... .... ... • ,v,• v~v~ ~v~v~v~v.7,:,,,.......:.,...:,:.....,,......... .. ...... I .. ... . ..v... ...........=================
• ,~ o~ v .v v.> >> >.>.v: :v~ ::.:v~~v .. .. .. .. . .............. ..... ..: .v.v. . v .. ....... ........ ...... ..... ....
S.... "" "v':::-'v'-vV......... v'>>>>>>>>>>>>>>>> . .v.,v .v.v.v.v .v: ".v. vv....:v~~:.,'.: , v .. ,. .v.v .-.v.v.v.=.. ...v. ... .. ... v ..v.vv.-.-..,.v.v v...v....-.-..v.v.
S -,, .-.- . .....- ..• ....- -.- . .. .. . . .. pp
.. .. ...• .• .. ,.......... ....... . -, ..... ....... . .,........ ... . ................ .... ...... ... .......
1,R ''IC W154100
FIGURE .. ... ......., LIMIT. ......................... . Le..............
..............................E ... .... .CE ~.. .... .. ... ... . .........
LOWE CHILE...........
+ EAST.OFWEST.FAUL......... L~~. .............ITH.SHAE.ABOV .... L............... ................... PERM EA........L.. ZONE.............. ...
................................... C. ...... O F. L O. ....... .....E R. .... ...C.N L ..... LLU IU O.ERLIE .SANDST......NE .
. +.... ... .. ....T RATE SATURATED..............
ALLU..U A......LU....1-..... U.M ... .. ........ ............... ... -...
.. .. . .. . . . .. . .... . .. .... .. .. ... .... .... .. . . .
.. LOWE.....NLE.WEL
...... ...... ...... O FFSET W ELL.. ..
400.+ +... ...................... ........ ..... .. L ..... ......... ...........
SC L .......... 160 ..ESA. M....LL.. AND... A..JACENT.. PROPERT.......ES. .RNT NM T.S.P...-R NG -0 AE 1 /90 .. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ \1\N \0 10 ............... L.. ......... ............... FIGURE.. 2. ...B.. LIMITS........... OFL.E...L.AUFE.ND .LLLCAIN
.......... ..... 2 -1.
32II
\11ý
19.20 20 21 COUNTY / A-- 63 21 2
30 29 29,28 2 27
+ +
1500
6339 > c
30.29 COUNTY ROAD 25 0+ 3"L1'32--329' 28 "34 27
7500 C)
15500 .
-- LEGEND-- .•
6313 DATA 32.33 X 3
m3 •5 +4 . 635o co
Dr LOWER CHINLE 'WELLS
296' OFFSET WELL -- -6400-.
S•"SUBCRBP OF LOWER CHINLE S• • ALLUVIUM OVERLIES SAND)STONE • _ • / /
/ UNSATURATED SATURATE S ALLUVIUM ALLUVIUM 296"
NOTE, ALL Mo DATA <0.03 77,400 4814003
SCALE: 1 "= 1600' 1 HOMESTAKE-MILL-AN D-ADJACENT-PROPERTIES GRANTS-NM-TO WNSHIP-11&12-N-RANGE10dI DATE: 12/09/01
FIGURE 2-9A, ELEVATION OF THE TOP OF THE LOWER CHINLE ~i.3\HMNC\Ll,60oo th
AQUIFER (WEST AREA), IN FT-MSL page 2-20
WEST FAULT/
/
/
,22 COUNTY ROAD
/
63010 i/
/
/
//
26+25 35 36
600o
-- LEGEND--
6285 -6300 a CW15 x CW21
SUBCROP OF LOWER CHINLE ALLUVIUM OVERLIES SANDSTONE
UNSATURATED SATURATED ALLUVIUM ALLUVIUM
DATA CONTOUR AND LABEL
NON-LOWER WELL
TEST HOLE
LOWER CHINLE WELL
18O0" OFFSET WELL
A+o 6 04501 .,aa-, I "M.AU K. A ,., o,
SCALE: 1"=1600' HDMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-11&12-N-RANGE-1O-W DATE: 12/09/01
FIGURE 2-9B. ELEVATION OF THE TOP OF THE LOWER CHINLE D\Rm3\H\L0w1600
AQUIFER, FT-MSL page 2-21
3.0 AQUIFER PROPERTIES
The important aquifer properties for the alluvial aquifer are the hydraulic conductivity
(permeability), saturated thickness and specific yield. Hydraulic conductivity is a
representation of the unit transmitting ability of the alluvial sands. Saturated thickness
times hydraulic conductivity equal the transmissivity. Transmissivity is the total
transmitting ability of the aquifer and thejmportant transmitting property for the confined
Chinle aquifers. The specific yield is the ,primary storage property for the unconfined
alluvial aquifer. Storage coefficient is the important storage parameter for the confined
aquifers.
3.1 SATURATED THICKNESS OF THE ALLUVIUM
The alluvial aquifer saturated thickness is•.defined by the difference between the water
level elevation and the base of the alluvium. The saturated thickness is presented in the
basic well data tables in the annual reports. The saturated thickness contours are
presented on Figures 3-1A and 3-1B.and were developed by taking the difference
between the water-level elevation and -base of alluvium contours. This shows that the
saturated thickness in the southwest corner of the Large Tailings is 60 feet in the alluvial
aquifer and decreases to zero at he -,boundary of the alluvial aquifer. Saturated
thicknesses have been increased significantly in the area of the fresh-water injection.
3.2 HYDRAULIC CONDUCI TRANSMISSIVITY AND STORAGE
Figures 3-2A and 3-2B present the hydraulic conductivities measured for the alluvial
aquifer at this site. The data presentsthe hydraulic conductivities determined from pump
tests for the alluvial aquifer. These values have been contoured and are presented in
Figures 3-2A and 3-2B. These figures show that hydraulic conductivities near the Large
Tailings are greatest on the southwest side and generally decrease to the east. A ridge
of lower hydraulic conductivities exists from the western edge of the Small Tailings to the
southwest into Murray Acres. Hydraulic conductivities substantially increase to levels
greater than 200 ft/day in the northern poqtion of Pleasant Valley and extend to the west.
Hydraulic conductivities also increase in the Broadview Acres area and extend through
Section 3. A zone of hydraulic conductivities in Section 28 of the San Mateo alluvium and in the Rio San Jose alluvium, exceed 200 ft/day (see Figure 3-2A).
Specific yields in the alluvial aquifer for the site have varied from 0.038 to 0.28, based on pump tests. A specific yield of 0.2 is thought to best represent the alluvial aquifer at the Grants site and was selected from calibration of numerical modeling of the site. This value is considered conservative relative to the restoration of the site. The lower hydraulic conductivity area will probably have a slightly smaller specific yield, which should reduce the volume required for restoration. The two factors may offset each
other, resulting in similar restoration times for varying aquifer properties.
Aquifer properties in the Upper Chinle aquifer vary significantly over the area due to the effects of secondary permeability on the sandstone. Transmissivity (hydraulic conductivity times aquifer thickness) is the important aquifer property for a confined aquifer. The transmissivity adjacent to the east side of the East Fault are approximately 2000 gal/day/ft (see Figure 3-3) and decrease to below 100 gal/day/ft to the east of this area. This affects the ground-water flow in the high transmissive zone adjacent to the East Fault. High transmissivity values also exist in the area west of the East Fault on the south side of the Small Tailings. The Upper Chinle aquifer is a confined aquifer but will, in general, have a storage coefficient of 5E-05. The specific yield of this confined aquifer
is expected to be significantly less than the alluvial aquifer and is estimated at 0.1.
Aquifer properties in the Middle Chinle aquifer vary significantly over the area due to the
effects of secondary permeability on the sandstone. The transmissivity adjacent to the east side of the East Fault are approximately 500 gal/day/ft (see Figure 3-4) and
decrease to below 100 gal/day/ft to the east of this area. This affects the ground-water flow in the high permeability zone adjacent to the East Fault. High transmissivity values also exist in the area west of the East Fault on the south side of the Small Tailings. The Middle Chinle aquifer is a confined aquifer with a storage coefficient of 3E-5. The specific
3-2
yield of this confined aquifer is expected to be significantly less than the alluvial aquifer
and is estimated at 0.1.
3-3
20
A LUVIUM
9 4
96 COUNTY ROAD 25 29 .
70
UI flATA IN ABSENT AREA.
296' OFFSET WELL
ALLUVIAL AQUIFER ABSENT
/ / 2~47? 005 50 0
SCALE: 1 "=1600' HOMESTAKE-MILL--AND-AD JACENT-PROPERTIES GRANTS-NM-TOWNSHIP-11L12-N-RANGE-1O-W I DATE: 08/16/01
FIGURE 3-1A, SATURATED THICKNESS OF THE ALLUVIAL PROJECTS\2001
AQUIFER (W/EST AREA), 2000, FEET page 3-4
6o 1125 A RS 35 35 36
CD
BROlAIVI' -
30 1537
4840AALUIAEAUSE-A-EN
AQIFR 200 FET0g
. .... .... . . " ' / ,W
S: "////" :35.36
10/ -- LEGEND-
,/" -- 30 CONTOUR AND LABEL
140 48,0 ALLUVIAL AQUIFER ABSENT
1600' 1 HI]MESTAKE-MILL-AN]D-AD)JACENT-PROPERTIES GRAN TS-NM-TO WNSHI P- 11&12-N -RANGE-10 -W I DATE: 08/17/01
FIGURE 3-1B., SATURATED QIFRTHICKNESS200 OFFETHE ALLUVIAL clwas\20°mpeo o- 1
N\\
it.,
a
0-1541500
0.8
k
-- LEGEND--
6.2
t0 0
0.3 LOCATION AND VALUE
I - PERMEABILITY, FT/DAY
DATA IN ABSENT AREA,
OFFSET WELL
ALLUVIAL AQUIFER ABSENT
PSfl' I
.50m
296'
12;
11--"&-47?40 1 8;40
SCALE: 1"=1600' 1 HOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-11&12-N-RANGE-1-W IDATE: 08/16/01
FIGURE 3-2A, HYDRAULIC CONDUCTIVITY (PERMEABILITY) FOR THE 2000WQAL 0-Ui
ALLUVIAL AQUIFER (WEST AREA), FT/DAY. p-age 3-6
.26
S. k.../ ... 43.3 26 25 7 -- 17.2
S~~BROADVIEJ •2
755
S0 Ct)
i0 49.77 4• • 31: : 6 .47 353
48.1 8 +9.6
2002
53. 296 *62-LGN
7549.7
• 142 / II•840\ . .8|€0i ::::::••-- ALLUVIAL AQUIFER ABSENT
SSCALE: 1 "=1600' HOM4ESTAKE-MILL-AND--ADJACENT-PROPERTIES GRANTS-NM-TO\VNSHIP-1IL12-N-RANGE-1O-W, DATE: 08/1 7/( FIGURE 3-2B. HYDRAULIC CONDUCTIVITY (PERMEABILITY) pojTs\2
FOR THE ALLUVIAL AQUIFER, FT/DAY Ae 3-7
VEST " FAULT/
/
/
//
//
I
/
/WESTERN LIMIT OF UPPER CHINLE
-- LEGEND--
ABANDONED WELL
SUBCROP OF UPPER CHINLE ALLUVIUM OVERLIES SANDSTONE
380
250-DATA
J • S OVYIB1 UPPER CI-INLE WELL•
UNSATURATED SATURATED T CW13 UPPER CHINLE INJECTI ALLUVIUM ALLUVIUM
"'2 C" UPPER CHINLE COLLEC
485400 487400 4B9400 20W, OFFSET WELL
SCALE: 1"=1600' I HOMESTAKE-MILL-AND-AfJACENT-PROPERTIES SRANTS-NM-TflNSHIP-1tI2 N-RANGE-10 DATE, 12/07O
ON
TIEN
FIGURE 3 3, TRANSMISSIVITY FOR THE UPPER CHINLE AQUIFER, GAL/DAY/FT
D\R1AW\Ui0
pace 3-8
1c5
4
ZERO SATURATION
C
15375ý0
2780
-- 100
DATA
CONTOUR AND LABEL
SUflCRDP OF MIDDJLE CH-INLE (I // "k` MIDDLE CHINI ALLUVIUM OVERLIES SANDSTONE
!ZZ2 " MIDDLE CH-IN UNSATURATED SATURATED
ALLUVIUM ALLUVIUM
4854o0 487400 49400 2 OFFSET WELt
SCALE: 1"1600' HOMESTAKE-MILL-AND-ADJACENT PROPERTIES GRANTS NM-TOVNSHIP-11&12-N-RANGE-I0-W' DAT
FIGURE 3-4, TRANSMISSIVITY FOR THE MIDDLE CHINLE
AQUIFER, GAL/DAY/FT
LE WELL
LE INJECTION
FE: 12/09/01
D -I.7CM~I0 'H pe339
4.0 GROUND-WATER FLOW
This section presents the water-level information for the Grants site aquifers. The
direction of ground-water flow is defined by the water-level elevation maps and is helpful
in defining connections between the aquifers.
4.1 ALLUVIAL
The depths of the water level for the alluvial wells are presented in the basic well data
tables and the water-level appendix in the annual reports. Figures 4-1A, 4-lB, 4-1C and
4-1D present the water-level elevations lfr the alluvial aquifer for 2000. Figures 4-1A
and 4-lB present the water-level contours for use in this subsection while Figures 4-1C
and 4-1D are overlays of Figures 4-lA and 4-1B for use with the Chinle ground-water
flow subsections. Water-level elevation data, along with the water-level contours, for the
Grants site are presented on Figures 4-iA and 41-B. Figure 4-1B shows that the ground
water is flowing into the tailings area from the north and converges to the collection
wells. Red arrows are shown to indicateý the direction of ground-water flow. The fresh
water injection downgradient of the site. -used in conjunction with the collection wells,
forces ground water to converge from all directions to the collection points. Water-level
elevations vary from 6,540 ft above mean sea level (ft-msl) on the east side of the
tailings to a low of 6,500 ft-msl on the western edge of Pleasant Valley.
Figure 4.1-iA shows the direction of alluvial ground-water flow in the area immediately
west of the Grants Project area with recdflow arrows. Flow in the San Mateo alluvium is
forced to flow through the western -portion of Section 28 due to the zero saturation limits
to the north and south of this area. The San Mateo alluvial water then mixes with the Rio
San Jose alluvial water, which continues to flow to the south. Alluvial ground water that
flows through the northern portion of Section 3 (see Figure 4.1-1B) joins the Rio San Jose
ground-water system in the eastern portion of Section 4.
-.4-1
4.2 UPPER CHINLE The depth to water levels and elevations are presented in the basic well data table and :) water level appendix in the annual reports. The water-level elevations were used to
show flow direction for the Upper Chinle aquifer.
The water-level depths vary over the area but, in general, are less than 100 feet to the water level in Upper Chinle wells. Water-level elevations are presented in Figure 4-2 for 2000 for the Upper Chinle in blue contours. The blue arrows show the direction of ground-water flow in the Upper Chinle aquifer. This figure shows that ground water in the Upper Chinle between the two faults is flowing into the Large Tailings area from the north. The fresh-water injection into Upper Chinle well CW5 forces flow back toward the collection well, south of the collection ponds from the Broadview Acres area. Flow in the Upper Chinle in Broadview and Felice Acres is to the south and discharges to the alluvial aquifer in the subcrop area. Flow east of the East Fault is parallel to the fault to the northeast of injection well CW13, close to the fault due to the high permeability zone adjacent to the fault. South of injection well CW13 the flow is parallel to the fault back *•>
toward the subcrop area. The flow in the majority of the area east of the East Fault is to the east-southeast into the lower permeability material away from the fault.
The water-level elevations for the alluvial aquifers are presented in Figure 4-i1D on an overlay to be placed on top of Figure 4-2 to show where the heads in the two aquifers are close. The alluvial contours are in black while the alluvial flow directions are presented by green arrows. Similarities in water-level elevations in the two aquifers indicate some connection in the area. The head in the alluvial aquifer upgradient of the site is higher than the head in the Upper Chinle. Therefore, ground water in this area is likely to be flowing from the alluvial aquifer into the Upper Chinle in the subcrop area. The heads in the two aquifers are very similar on the west side of the Large Tailings in the subcrop area and to the south in the collection pond area. The amount of transmitting ability the Upper Chinle aquifer has in the subcrop area also controls the rate of alluvial water moving into the Upper Chinle aquifer. This transmitting ability is low
4-2
enough in some areas to greatly restrictý movement into the Upper Chinle due to the
sandstone transitioning into a shale.
Ground water likely flows between these two aquifers depending on the head conditions
at different times. Water-level elevation[Jn, the Broadview acres are very similar in these
two aquifers Indicating potential conneion in this area. Several wells in Broadview
Acres are completed in both the Upper Chinle and alluvial aquifers, which results in
connection in this area. The Upper Chiritewater discharges in southern Felice Acres to
the alluvium where the head is significantly -larger in the Upper Chinle than in the alluvial
aquifer. The Upper Chinle water is also discharging to the alluvium from the east side of
the East Fault due to the much higher head in the Upper Chinle in this area than in the
alluvial aquifer.
The travel time for seepage into the Upper Chinle aquifer near the Large Tailings to the
Broadview Acres area was approximately 20 years. This indicates that an average
ground-water velocity of approximately.1 ft/day existed for the ground water moving in
the Upper Chinle from the Large Tailings to the Broadview Acres area. Alluvial water
naturally moved through the Upper Chinle in this portion of the aquifer prior to the
tailings due to the subcrop conditions. Therefore, this portion of the Upper Chinle aquifer
contained alluvial type water prior to the tailings. The travel time to the subcrop area
east of the East Fault in the Upper Chinleis estimated to be approximately 30 years due
to alluvial ground water having to flow to -this area. Recharge from alluvial to the Upper
Chinle east of the East Fault then moved back to the northeast. A ground-water velocity
estimate of approximately 1 ft/day is.a#ppropriate for this portion of the Upper Chinle
aquifer.
4.3 MIDDLE CHINLE
Water levels in Homestake's Upper,, Middle and Lower Chinle wells are presented in the
annual reports. Fall of 2000 water-level elevations for the Middle Chinle aquifer are
presented on Figure 4-3. The gradient-in the Middle Chinle aquifer is steeper in its
-.. •4"3
subcrop area in the southern portion of Felice Acres near wells CW44, CW45 and CW46.
This increase in gradient is due to an influx of water in this area to the Middle Chinle ,.
aquifer from the alluvial aquifer. The blue arrows show the direction of ground-water
flow in the Middle Chinle aquifer. Flow on the east side of the East Fault is mainly to the north near the East Fault, but due to a decrease in the transmissivity in the aquifer to the
east, flow moves easterly away from the East Fault.
Ground-water flow west of the West Fault is to the southwest, discharging into the alluvial aquifer. This prevents the alluvial aquifer water from entering the Middle Chinle aquifer in the subcrop area on the west side of the West Fault. This Middle Chinle water flows from upgradient of the site into the area west of the Large Tailings. The remainder
of the Middle Chinle aquifer is recharged by the alluvial aquifer south of Felice Acres.
A mound of water around well CW14 has been created by the injection of fresh water
into this well. This causes the ground-water flow to be to the north and south of well CW14. Flow between the two faults in the Middle Chinle aquifer, north of CW14,
continues downgradient of the tailings area. The head in the Middle Chinle aquifer on each side of the two faults is significantly different than the head between the two faults, which shows that the ground water is not readily connected on each side of these faults.
The alluvial water-level elevations on the overlay in Figure 4-1D should also be used over Figure 4-3 for comparison with the Middle Chinle piezometric surface. Green arrows are
used to show the direction of flow in the alluvial aquifer. The water-level elevation in the
Middle Chinle between the two faults is significantly lower than the alluvial aquifer in the
tailings area indicating no high conductance connection zone in this area. The head in the Middle Chinle aquifer west of the West Fault to the west of the Large Tailings is similar to the water-level elevation in the alluvial aquifer indicating that some potential
connection could exist in this area. Water-level elevations east of the East Fault in the Middle Chinle are also significantly below the water-level elevations in the alluvial aquifer.
The water-level elevations in the Middle Chinle on the south side of Felice Acres are
4-4
slightly less than the alluvial water-level elevations and the existence of the subcrop in
this area allows ground water to flow from the alluvial aquifer to the Middle Chinle.
Water quality changes also indicate connection in this area.
The time for contaminated alluvial flow to reach the subcrop area in the Middle Chinle on
the south side of Felice Acres was rough•y 30 years. Alluvial ground water has moved
back to the north from the subcrop area in the Middle Chinle aquifer into the Felice and
Broadview Acres area. The ground-water velocity rate is slightly less than 1 ft/day for
this movement in the Middle Chinle aquifer. The natural direction of ground-water flow in
the Middle Chinle aquifer between the two faults is to the north. Therefore, this area of
the Middle Chinle aquifer contained alluvial type water prior to seepage concentrations
flowing into this area. Alluvial water also moves from the Middle Chinle subcrop area into
the Middle Chinle on the east side of the East Fault. Movement velocity in this area
based on water-quality changes has to be significantly less than 1 ft/day.
4.4 LOWER CHINLE
Water-level elevations for the Lower Chinle wells are presented with the remainder of the
Chinle wells in the annual reports. Figures 4-4A and 4-4B present the 2000 water-level
elevations for the Lower Chinle aquifer. The West and East Faults are shown on these
figures. Flow west of the West Fault in the Lower Chinle is mainly to the northeast. Flow
between the two faults is to the northwest, indicating that the Lower Chinle water moves
across the West Fault. The approximate subcrop areas for the Lower Chinle aquifer are
also shown on these two figures.
The overlays in Figures 4-1C and 4-1D present the water-level elevations for the alluvial
aquifer in black and should be used over Figures 4-4A and 4-4B respectively to compare
the heads in the two aquifers. The comparison between the alluvial and the Lower Chinle
aquifers shows that generally water-level elevations in the alluvial aquifer are significantly
greater than the water-level elevations in the Lower Chinle. Water-level elevations
between these two aquifers is very similar in the west-central portion of Section 3 where
4-5
the Lower Chinle subcrops against the alluvial aquifer and direct connection occurs. Water-level elevations would be expected to be very similar in the two aquifers in the
subcrop area. Water-level elevation west of the West Fault in the alluvial aquifer is significantly greater than the water-level elevations in the Lower Chinle except for the
area near the Lower Chinle subcrop. These two water-level elevation figures indicate the only connection between the alluvial and Lower Chinle aquifers is in the subcrop areas.
The travel time from the tailings to the Lower Chinle subcrops in Section 3 is roughly 30
years. Water movement in the weathered Lower Chinle would be less than 1 ft/day. These movement rates would greatly decrease where adequate secondary permeability in
the Chinle shale has not developed.
4-6
T Go 16476.75 a 6492.5 6496.1 6474) 6 476.9
o 64 6. 0a 0• a *6476.7642a50
-"06473.8 6483.0 6428 490 6495.3 c
ý64.82767496.5 jp. C CT:,
o6471,6 '0"
641. 647149.0 30.29) COUN( ROA 25 - 6471.4 67. .
6468.3 322+ Crj
64682 646•
6464ý
'6461.0
6445.7
6449, 2
0\
6 449.0. 6461. S*,I
-- LEGEND-
6470A. DATA
ýd - -' FLOW DIRECTION ý.1
-651 5 CONTOUR AND LABEL 1 * DATA IN ABSENT AREA,
296' $OFFSET WELL * /' - ALLUVIAL AQUIFER ABSENT7'
2045' 27! 477400 2 6471.8 ,550'148ý400
1 "=1600' HONESTAKE-MILLAND-ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-1&12-N-RANGEIO-W I DATE: 08/16/01 1I PRIECTS\2001 -1 FIGURE 4-1A, WATER-LEVEL ELEVATION FOR THE ALLUVIAL AQUIFER, 12000WQAL LU
(WEST AREA), 2000, FT-MSL, Ipage 4-7
X2 CONYRA 3C 3
27
PL A TV L EY EIA E
C' n UR
• g~
C p
7>
40a.
75'
�47�4 Sal
6476S
r
i85400
LARGE TE INGS- IE!N ION IN PRDG ESS) " 4
4- " . 1541500
'D I.. 6-/ 6' 54
_2 2 t -- •.+ LCTINAN L
RE.. 34 35oI 35UVA 36IE SN
IF SCALE: 1"=1600' I HOMESTAKE-MILL -AND-ADJACENT-PROPERTIES GRANTS NM-TOVNSHIP-11&12-N-RANGE '0-WI DATE: 08/17/01 bj
L3-
6465,
16.1.2N?
FIGURE 4-1B. WATER-LEVEL ELEVATION FOR THE ALLUVIAL projes\RooI-o6
AQUIFER, 2000, FT MSL 4-S
I-
6500
. . .490...
... ... ... 64O
•i~ ~~~~ ~~~~ .iii!ll .~iiiili!ii .. . i .... iil l iii ii~i+!ii}. !+ ... .... .. ..?i~ ~i !' + I~i~ i~ i~ii+! ••i~•!i~ i...........ii!! I jii~ ~iii~ ~iii iiiii~ g~ iiiii gliii...........i~i ! ! ii iiii iii~ iii~ iii i~ iii~..... iiiii.... ...... .......i i i ii i~li ii ii~ li !•o
.............. i•!!i~ ~~ii~ ~~iii i~i~ i i,•+i:++:•ii i+? :.+ .................iii~ i•- • _ _ ° .•
................ i -6f~f!"- -
lo ..1 \ .. ... ... ..
z-----+---•~~ ..........i!i!!i•i
Siiii!i~ii~ i~iiiiiiiii....... ~iii!!iii ....... . ... • ~ ~ ~ . . . .. . . . . .=. ..== = = = = == = = = = = = = = == = = = = = = = = == === = = = =.. ..... .::
(.
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LL:n
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"ýz
J
........... ....... I ....... I ý ....... ........ --- ý I ....... ...... ... ..... ........ ..... .......... ... ... .... ........... ............. ... .......... ...... .. ...... .. .. ..... .......... ........ .. .... .
: ............. .............. ............................................... - - - ý ....... ................................ ...................... ............. ............
.................... ........................................................... ..................... .............. ................................ ........... .............................................. ............................ ... ............................................. : ............................
....................... ........ .................................. . .
.............. - ................................. .......... .......... .......... . ... ...........
........................... ...................... .................
.............. ........ .00, ............. ................................. ol ........................................
....................................................... ................................. ...... ........................
....... ............
.................................................. ................................................. .................. ......... I ................ . ..................................... .......................... ................. ...... 11 .............. .................. ..........
N
)
.' .. .......... .. .../. .. .. . . . . . . . . .
.. . . . . .. . .. .. .. . . .
646e
)
FIGURE 4-1D, WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL .
AQUIFER, 2000, FT-MSL, OVERLAY .. 4-10
............
..............
.................
....................... L .......................... ....... .................................... .................................... ..... . . . . ......... ..... .
..........
...........
.... . .........................
(rAULL
,5- FLOW DIRECTION
-6515 CONTOUR AND LABEL
SUBCROP OF UPPER CHINLE ALLUVIUM OVERLIES SANDSTONE
A n T"Sr
485400 4B7A00
- 6528
"S CW18
"® CW13
Up ER CHINLE •w
C#TOUR AND LABE
yPER CHINLE CELL
,/UPPER CHINLE INJECT ON
UPPER CHINLE COLLECTION
OFFSET WELL
SCALE: "=1600' HOMESTAKE-MLL-AND-4ADJACENT-PRO]PERTIES GRANTS-NG-TDWNSHIP-f1&I2-N-RANGE-1O-W M 1
FIGURE 4 IC0 WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, (WEST AREA), 2000, FT-MSL, OVERLAY
coC8- 9
4
UPPER CHINLE FLOW
CONTOUR AND LABEL
"* CWIS
"* CW13
0F.ffj
UPPER CHINLE WELL
UPPER CHINLE INJECTION
UPPER CHINLE COLLECTION
OFFSET WELL
TOWNSHIP-IMI12-N-RANGE-O-W I DATE: 1-
WATER-LEVEL ELEVATIONS FOR THE ALLUVIAL AQUIFER, 2000, FT-MSL, OVERLAY p'*4-WD
CC3-B6
I-PR[
WEST FAULT/
/
/
//
/ /
//
ACRES
WESTERN LIMIT OF UPPER
CHINLE
3.
-- LEGEND--
6565.8
- 6528
"@ CW12
"® CW13
Ž00-'--
DATA
UPPER CHINLE FLEW
CONTOUR AND LABEL
UPPER CHINLE WELL
UPPER CHINLE INJECTIDN
UPPER CHINLE COLLECTION
OFFSET WELL
SCALE: 1"=1600' OHMESTAKE MILL AND ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP-ItI2-N-RANGE-IO-V I DATE: 12/07/01
FIGURE 4 2, WATER-LEVEL ELEVATIONS FOR THE UPPER CHINLE AQUIFER, 2000, FT MSL
D\R13\HMC\UPI SO
p-nge 4-11
0 04
/
./
4
SATURATED ALLUVIUM
487400 1/ 44
6531.61 !!
6495,10,649508
LARGE-TAILINGS-PILE (RECLAMATION IN PROGRESS)
4 Os 650022
I
/
6495.45
SUBCROP OF MIDDLE CHINLE ALLUVIUM OVERLIES SANDSTONE
UNSATURATE. ALLUVIUM
SATURATCD ALLUVIUM
495400 //'
649
LINED 0VAPPN LINED
Ef VAP SONO
SMALL TAILINGS
7.24 PILE L /pPN
4i
650099
-6500
DATA
MIDDLE CHINLE FLOW CONTOUR AND LABEL
MIDDLE CHINLE INJECTION
270' S OFFSET WELL
SCALE: "=1600' IHOMESTAKE-MILL-AND-AnJACENT-PROPERTIES GRANTS-NM-TOUNSHIP-HI&12-N-RANGE-O-W I DATE: 12/09/01
FIGURE 4-3, WATER-LEVEL ELEVATIONS FOR THE MIDDLE CHINLE AQUIFER, 2000, FT-MSL
D�Ri3\H�4WJ�T0I6OD Lii
page 4-12
Co
I
! I
FAULT,
/
isa7�oa -
-LEGEND--
4
48ý400 1
COUNTY ROAD 63 21
-- LEGEND-DATA LOVER CHINLE FLOW CONTOUR AND LABEL
LOWER CHINLE WELLS
OFFSET WELL f.4
SUBCROP OF LOWER CHINLE ALLUVIUM OVERLIES SANflSTON
UNSATURATED SATURATED ALLUVIUM ALLUVIUM
a
29 28 32,33
6484.0
6475to
0u 296'
S
NOTE' ALL Ho DATA <0.03 1\77400 481400 a'%
SCALE: I"=1600' IHOMESTAKE-MILL-AND-ADJACENT-PROPERTIES GRANTS-NH-TOWNSHIP-1i•L2-N-RANGE-AOW-I DATE: 12/09/01
FIGURE 4-4A, WATER-LEVEL ELEVATIONS FOR THE LOWER CHINLE Ib\l3\MC\L0W16® AQUIFER (WEST AREA), 2000, FT/MSL page 4-13
t'4
6465 -/
/., I
LINED EYAP POND LINED
NO, 2 EVAP POND NO. 1
SMALL PILE
TAILINGS)
/
!
2626 65 35 36
/1537500
-- LEGEND--
SUBCROP OF LOWER CHINLE ALLUVIUM OVERLIES SANDSTONE
UNSATURATED SATURATED ALLUVIUM ALLUVIUM
6477.3 DATA
- LOWER CHINLE FLOW -- 6475 CONTOUR AND LABEL
�Oe m
wool
LOWER CHINLE WELL
OFFSET WELL
6471.5XAty ~ //14900________ Zý,' j.5!L4ooo !1Z 48?47
SCALE! "=10 IHOMESTAKE-MILL-AND ADJACENT-PROPERTIES GRANTS-NM-TOWNSHIP II12-N RANGE-tO-V DATE: 12/09/01
FIGURE 4-4B. WATER-LEVEL ELEVATIONS FOR THE LOWER I,,t'LOv6O
CHINLE AQUIFER, 2000, FT-MSL4-
C /C
FAULT/ /
/'4 '4
is
/
I
M
646S.7
EAST / FAULT/ /
I'
!/
/
/
4
'u