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

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o6471,6 '0"

641. 647149.0 30.29) COUN( ROA 25 - 6471.4 67. .

6468.3 322+ Crj

64682 646•

6464ý

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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

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6476S

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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

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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

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