AuthorTimGrabielNaturalResourcesDefenseCouncilProjectDirectorDavidBeckmanNaturalResourcesDefenseCouncilNRDCTHEEARTH’SBESTDEFENSETable of Contents Executive Summary

3 The Navajo Aquifer Shows Signs of Material Damage and Continuing Decline

5 Flawed Modeling Obscures Evidence

of Material Damage to the Navajo Aquifer

10 Controversy Comes
to a Head with Peabody’s New Request for Increased Navajo Aquifer Access

14 Recommendations

for Preserving
the Navajo Aquifer

16 Appendices

19 Technical Report: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the NAqi.tifer, Black Mesa, Arizona

19 Selected References

32 Technical Review of “A Three-Dimensional
Flow Model of the D and N Aquifers” Prepared
by HIS Geotrans and Waterstone, for the Peabody Western Coal Company, September 1999

33 Endnotes

39 Natural Resources Defense Council

2Executive Summary F or more than 40 years, billions
of gallons
of groundwater have been pumped out of the Four Corners region of Arizona
by Peabody Western Coal Company before being mixed with pulverized coal to create

a thick, black substance called slurry and piped more than 270 miles to a coal-fired power plant
in Laughlin, Nevada. Mining
of this potable, pristine groundwater— which serves
as the primary source
of drinking water for the area’s Hopi and Navajo residents—has been connected

to a variety
of groundwater-related problems. Peabody’s operations have had

a range of environmental, cultural, and religious impacts
on the region’s tribal communities that make their home

in the Black Mesa plateau, and now Peabody

is seeking

to further erode protections
for this vital water source. The Navajo aquifer, known

as the N-aquifer,

is an underground water-bearing formation that provides the sole source of potable drinking water to many Hopi and Navajo on Black Mesa. Insulated
by
a barrier of mudstone and sandstone,

it naturally satisfies Environmental Protection Agency (EPA) standards
for drinking water—unlike

the region’s other aquifers, whose contents are brackish

or otherwise contaminated.
The springs it feeds along its southern front are sacred
to the Hopi people and essential

to their religious practice. In 2000, the Natural Resources Defense Council (NRDC) released

a technical report entitled Drawdown: Groundwater Mining
on Black Mesa (“Drawdown”), which assessed the conflict between the coal company using the Navajo aquifer for coal slurry operations and the people of the Black Mesa who rely on the aquifer for clean water. The 2000 report evaluated the data on groundwater depletion and made recommendations about what role the federal government should play in resolving the controversy.

Six years later, Drawdown: An Update uses new data to update the hydrogeological evaluation

of the impacts
of Peabody’s massive water withdrawals

on the health of the Navajo aquifer. This 2006 update finds that not only are there signs of material damage

to the aquifer, but that some of the government’s failure
to adequately monitor the damage can be attributed

to a flawed modeling systemNaturalResourcesDefenseCouncilthat obscures on-site evidence
of physical damage. Table

1 lists the criteria used to assess material damage. The changes that have occurred

in the aquifer since 2000 paint the picture of a system still in decline. Table

1: Material damage

to tile N-aquifer since 2000 Criteria used to Standard

Are Indications

of material damage still present? assess material damage Criterion

1: “Maintain potentiometric
Yes. Groundwater level,

a key measure

of structural Structural
head of 100 feet above stability, remains within 100 feet of the top of the aquifer

in stability

top of N-aquifer

at any two monitored wells and has periodically dropped below the point to preserve confined
top elevation

of the Navajo aquifer itself, indicating material state of aquifer.” damage. Criterion

2:

“A value of leakage from Yes. Leakage

is not adequately assessed. Although the Water quality D-aquifer not to exceed
10 data needed for direct measurements

are lacking, analysis percent from mine-related

of related data reveals increasing trends

in chemical withdrawals.” concentrations

in some areas of the Navajo aquifer, threatening water quality and potentially causing material damage. Criterion

3:

“A discharge reduction
Yes. Decline

in discharge

of 10 percent
or more was Discharge

to

of 10 percent

or more indicated

in three of four recently monitored springs and, springs caused
by mine-related

if the model were updated and forced
to calibrate, the withdrawals based on conclusion that no material damage has occurred would not results
of N-aquifer

be supported. simulation.” Criterion

4:

“A discharge reduction
Yes. Material damage

is indicated

by a decline

in discharge Discharge

to

of 10 percent
or more

of 10 percent
or more. Three of four continuously monitored washes caused
by mining.”
wash gauging stations show decline
of at least 50%, clearly indicating material damage; however, simulated modeling results do not calibrate with monitoring data. The new data show that Peabody’s mining practice
of drawing down the aquifer—sapping

the water pressure that has taken many centuries

to build—has already caused the aquifer material harm according

to some of the U.S. government’s own criteria. Now,

a permit request from Peabody seeks to potentially increase water withdrawals from the Navajo aquifer and loosen protections
for this water source—despite
signs of damage and continuing decline indicated
by the physical monitoring data. NRDC recommends

a number
of steps that must be taken to protect this critical water source: • Peabody should permanently cease groundwater pumping from the N-aquifer, and the Office of Surface Mining Redamation
and Enforcement must deny Peabody’s request for increased access
to these waters. • The Department

of the Interior should improve
its monitoring

of the N-aquifer and should ensure that the Hopi tribe and Navajo Nation have

a viable, long-term source of water. • With tribal consent, the Environmental Protection Agency should designate the N-aquifer

a “sole source aquifer” that
is granted government protection. • Tribal sovereignty must be respected, and federal and tribal governments should work cooperatively

to manage aquifer resources. Full text of the original 2000 technical report can be accessed online
at www.nrdc.org.NaturalResourcesDefenseCouncilThe Navajo Aquifer Shows Signs of Material Damage and Continuing Decline A quifers are like sponges, holding their groundwater

in sediment

or in tiny pores, fissures, and fractures

of rock such as sandstone and limestone. Water trickles through these spaces, pulled from high pressure areas to areas of lower pressure, but compared with surface water its flow
is imperceptible:

it moves just

a few inches
or feet in the course
of a year. Beneath Black Mesa, water first flows south from the exposed Shonto plateau, then divides. Over the last few decades, however, Black Mesa and its springs have turned increasingly
dry. The physical impacts

to the Navajo aquifer have become even more pronounced since the release
of the original Drawdown report. In 2000, NRDC examined the Office of Surface Mining Reclamation
and Enforcement’s (OSMRE) own standards
for assessing material damage

to the N-aquifer’s structural stability;

its water quality, and its discharge

to both springs and washes. Drawdown: Groundwater Mining
on Black Mesa concluded that under the government’s adopted criteria, material damage had clearly occurred

to the N-Aquifer

in at least one respect. Drawdown further concluded that physical monitoring data belied many of the Department of Interior’s conclusions

of no material damage, determinations which were often
at odds with physical monitoring results.
In fact, the government’s results stemmed almost exclusively from the results of incomplete and inappropriately
used models of the N-aquifer. For Drawdown:
An Update, NRDC undertook

a thorough review of the most recent monitoring data and, additionally, commissioned LFR Levine-Fricke (LFR)
to update
its technical review of the Cumulative Hydrologic Impact Assessment (CHIA) criteria
in light of the latest monitoring data (appended

to this publication). This section revisits OSMRE’s material damage criteria with the most current physical monitoring data and expert review available. The results are discouraging:NaturalResourcesDefense CouncH

j5• Material damage

to the N-aquifer’s structural stability

is further indicated
by new data, and the confined state of the N-aquifer has been potentially compromised; • Material damage

to the N-aquifer’s water quality

is indicated
by physical monitoring data, which shows localized increases

in concentrations

of sulfate, chloride, and total dissolved solids; • Simulated modeling results do not calibrate with physical monitoring data for spring discharge, with the latter indicating that material damage has already occurred for the three springs on the southwest side of the mesa; • Simulated modeling results do not calibrate with the physical monitoring data for wash discharge, with the latter once again indicating that material damage has already occurred. Cumulative Hydrologic Impact Assessment Criteria Results Indicate Further Damage In 1989, the Department

of the Interior established Cumulative Hydrologic Impact Assessment criteria

to assess the material damage

to the N-aquifer caused by Peabody pumping. Material damage was described

as “any long-term

or permanent change
in the available quantity

or quality of a water source that will preclude its use or reduce its utility
to an existing water user.” 1 In 2000, after reviewing the data from the U.S. Geological Survey

(a sister agency of OSMRE’s within the Department

of the Interior) and Peabody’s own reports, NRDC concluded that based on the government’s own criteria, material damage had occurred. Six years later, the most recent data shows that the N-aquifer shows signs of continuing decline. 23 Water withdrawals

on Black Mesa clearly violated

at least one criterion for establishing material damage, with other criteria strongly indicating material damage was occurring. These findings are particularly important due to the possibility

of renewed water withdrawals

at increased levels over the next 20 years,
as discussed

in the following section. CHIA Criterion One: Structural Stability Criterion: Maintain potentiometric head (the height
to which confined liquid will rise when tapped by
a well) of 100 feet above the top of N-aquifer

at any point to preserve confined state of aquifer. 2000 Findings: OSMRE established material damage criterion

to protect the structural stability
of the N-aquifer. Peabody was to “{mjaintain potentiometric head 100 feet above top of N-aquifer

to any point to preserve confined aquifer state.” 4
In 2000, NRDC reported that six of the fifteen wells (Rough Rock, 1OT-258, bR-i 11, Sweetwater Mesa, BM3, and Kayenta West) dipped below the 100-foot potentiometric threshold. Even if the first four sites are discounted
for their proximity

to the aquifer’s unconfined portion, that still leaves two (Kayenta West and BM3) whose head fall within the signal 100 feet. As such, according

to CHIA Criterion One, material damage continues

to be indicated. 2006 Findings: Since 2000, water levels
at most of the monitoring wells have continued

to decline, supporting
the findings
of material damage made in Drawdown. 5

In addition, the latest monitoring data indicates that water levels in Kayenta West and BM3 have dipped below the top of the N-aquifer, potentially compromising

the confined state of the aquifer.
If, as OSMRE indicated, maintaining

a potentiometric head 100 feet above the top of the N-aquifer

is intended

to provide

a protective barrier
in order to preserve the confined state of aquifer, then these continuing declines raise two serious concerns: 6 • First, water levels
at Kayenta West and BM3 have dipped far below the 100-foot criterion, which constitutes

a violation
of the CHIA requirements
and an indication

of material damage under OSMRE’s adopted safety standards. • Second, because water levels
at Kayenta West and BM3 have dipped below the top of the N-aquifer itself and, therefore, have potentially compromised

the confined state of the aquifer
in those areas, the violation
of CHIA Criterion One
is especially serious. Natural Resources Defense Council

6The monitoring data introduce

a suite of concerns regarding material damage

to the N-aquifer, including a reduction

in permeability
and loss of storage capacity

in the area where the overdraft occurred, and raise serious concerns about the impact of any future mine-related aquifer withdrawals. CHIA Criterion Two: Water Quality Criterion:

A value of leakage from the Dakota Sandstone aquifer (known

as the D-aquifer) not to exceed
10 percent from mine-related withdrawals. 2000 Findings: Drawdown reported that since data necessary for direct measurements

is lacking, monitors have sought
to indirectly gauge the magnitude

of leakage from the D-aquifer

by the amount
of inorganic compounds,

or total dissolved solids (TDS),
in N-aquifer water. The USGS identified increased chloride and sulfate concentrations

as important indicators

of increased D-aquifer leakage. 7 Drawdown conduded that data from the previous

10 years had resulted

in dramatic localized increases

at certain wells that were discounted

by OSMRE for sampling error, mislabeling, failure of individual well seals, or changes

in pumping methods. 2006 Findings: The latest physical monitoring data indicates that the trend of increased chemical concentrations

has continued. The last 15 years have seen some dramatic localized increases, such as a spike in sulfate concentrations

in a Chilchinbito well and

a climb
in TDS in a well at Forest Lake. Data collected

at various monitoring springs that discharge from the N-aquifer also show

a marked increase

in chloride. 9 Recent monitoring data provide evidence
of increasing trends
in inorganic constituents

in the N-aquifer, including chloride and total dissolved solids, particularly

in the southeast portion
of near Rough Rock, Pinon, and Keams Canyon.’ 0 Despite these trends and localized increases, OSMRE continues

to conclude that material damage has not occurredJ’ The sources of induced leakage have not been inadequately assessed. Leakage can occur for
a number of reasons:

a shift in the vertical gradients between the D- and N-aquifers from pre-development

to post- development times,

a shift in the horizontal gradient

in the N-aquifer,

or a combination

of both.’ 2 With respect to the vertical gradient, OSMRE makes no attempt

to estimate induced leakage through water-level monitoring of the D- and N-aquifers and changes

in their vertical gradients.’ 3 With respect
to the horizontal gradient, historic horizontal gradient

in the N-aquifer was toward the south. However,

it appears that horizontal gradient has reversed

as a result of Peabody’s pumping regime—leakage
now appears

to be providing

a source of storage (or recharge)

to offset those pumping stresses.’ 4 OSMRE has failed
to adequately assess this shift in horizontal gradient.’ 5

In short, OSMRE has failed to provide quantitative estimates
of either the vertical gradient between the D-aquifer and the N-aquifer from pre-stress

to post-stress periods
or the horizontal flux or vertical induced leakage based on observed changes

in the horizontal gradient

in the N-aquifer. The CHIA criteria do not address the potential for man-made conduits that may effect water quality in the N-aquifer.

In particular, wells in the Peabody well field are perforated

or screened across multiple aquifers and, as such, when the wells are not pumping,

a direct vertical conduit exists between the aquifers.’ 6 Because water quality
in overlaying aquifers

is worse than in the lower-lying N-aquifer, contamination conveyed through inactive wells

is a possibility.’ 7

If the wells are not pumped for
a significant period of time, water that
is “injected” into the N-aquifer from overlying aquifers under non-pumping conditions could significantly impact water quality
in the N-aquifer.’ 8 Peabody’s massive water withdrawals coupled with its use of perforated well casings have created

a situation

in which damage

to water quality may be occurring whether Peabody

is pumping

or not. CHIA Criterion Three: Discharge

to Springs Criterion:

A discharge

to springs reduction

of 10 percent
or more caused by mine-related withdrawals based on results of N-aquifer simulation. 2000 Findings: OSMRE designed

its third criterion

to assess damage

to the springs, finding that damage was indicated

if discharge fell by 10 percent
or more
as a result of Peabody’s withdrawals. Unfortunately,

asNaturalResourcesDefenseCouncil7reported

in 2000, OSMRE linked this criterion

to a U.S. Geological Survey (USGS) computer model of groundwater flow that
is both outdated (the last computer simulation was in 1994) and inappropriate

for the purpose
of evaluation. Moreover, this model hardly reflects the on-site data reported
by the USGS.’ 9
At the time of the original Drawdown report, not only had most springs experienced

a discharge reduction

in excess of 30 percent, but the majority
of those appeared

to have decreased
by more than 50 percent (Rock Ledge, Moenkopi School, Many Farms, Whiskey and Pasture Canyon). 2 ° Hence, regardless

of the monitoring data deficiencies, OSMRE’s conclusion that no material damage has occurred

as a result of Peabody’s pumping was strongly challenged

by the data.
It was unclear why the modeling simulations had not been adjusted (calibrated)

to better represent observed decreases

in spring discharges. 2006 Findings:

It remains unclear how

a conclusion
can be made that no material damage

is evident based on simulated modeling results under both the USGS model (1994) and Peabody model (1999) while physical monitoring data suggest otherwise. 2 ’ The USGS’S most recent published monitoring data from four springs that discharge from the N-aquifer (Pasture Canyon, Moenkopi School, Burro, and an unnamed spring near Dennehotso) clearly shows an overall reduction

in spring discharge
for the three springs on the southwest side of the mesa (Pasture Canyon, Moenkopi School, and Burro). Discharge from the unnamed spring near Dennehotso
has fluctuated over time, implying that some unknown change(s) may have occurred (e.g., new monitoring location, nearby construction),

but the two lowest measured discharges over the last decade occurred within the last three years. 22 Looking

at the annual data from Pasture Canyon, Moenkopi School, and Burro springs, physical monitoring data shows reductions that far exceed the 10 percent threshold:

24 percent percent

at Moenkopi,

19 percent

at Pasture Canyon, and 50 percent

at Burro. 23 Moreover,

if other historic spring discharge data were considered, observed discharge reductions would be much greater (70 percent

at Moenkopi and 85 percent

at Pasture Canyon). 24
All considered,

if models used to support claims of no material damage were updated and forced
to calibrate

to the physical data that has been collected, material damage would likely be indicated. OSMRE’s analysis
of this criterion

is severely limited by its reliance
on computer modeling, but if physical monitoring data were given precedence over modeling, material damage would be evident. OSMRE continues

to disregard actual monitoring data and historical accounts from Hopi elders that the outflow from springs sacred
to the tribe has been drying up. 25 Instead, OSMRE has created

a “virtual” world that differs starkly from the reports on the ground

in Black Mesa.

It is not entirely clear how OSMRE could conclude that no material damage

is evident based on simulated modeling results while physical monitoring data suggests otherwise. This finding
of no material damage

is particularly dubious since the groundwater Using water levels to better assess water quality A measure that should be used to supplement TDS sampling—one
that was proposed

by the Office of Surface Mining

in 1988, but was bumped from the CHIA’s final version—is water level. Under the proposed criterion, the aquifer’s potentiometric head would be monitored
for decline against

a baseline altitude, which represents how high its water would have climbed before Peabody’s operations began. Should
its head drop below 100 feet of this baseline—suggesting

a sharp fall in water pressure and the formation

of a pressure gradient strong enough

to pull lower-quality water from above—material damage would be indicated.
(By contrast, under CHIA Criterion One, potentiometric head

is monitored
for its proximity

to the aquifer’s surface, not to a predetermined baseline, and material damage

is indicated where the head drops within 100 feet of the aquifer itself.)

If this proposed criterion were
in use in 2000, there could be little question that water quality was threatened.

In the intervening years, water quality has worsened

to the point where three of the 11 monitored wells
in the N-aquifer’s confined portion (Pinon, Keams Canyon, and BM6) have dropped below the 100-foot mark and three additional wells (BM2, BM3, and BM5) are on the verge of crossing over. Moreover,

in the areas where the N-aquifer has dipped below the top of the N-aquifer, the introduction

of air can alter aquifer chemistry and result
in damaging reactions such as the formation

of iron and manganese oxide precipitates. Such impacts would be irreparable. Natural Resources Defense Councilmodel used to make that determination

is admittedly incapable
of resolving significant changes

in spring discharges

at the level required
by the CHIA criteria. 26 Physical monitoring data continue

to show that material damage,

as defined by the CHIA criteria,

is occurring. CHIA Criterion Four: Discharge

to Washes Criterion:

A decline
in discharge

to the N-aquifer washes by 10 percent
or more, caused by mining. 2000 Findings: OSMRE designed

its fourth criterion

to assess damage

to washes, finding that damage was indicated when discharge

to the N-aquifer’s washes declined
by 10 percent

as a result of mine-related groundwater pumping.
As noted
in 2000, evaluation

of this fourth criterion, like evaluation

of the third, relies on a “virtual” world of modeling that does not conform

to physical monitoring data. Unfortunately, OSMRE based its analysis
of this criterion
on the latest USGS N-aquifer model, which had last been updated
by USGS in 1994. OSMRE continues

to condude that based upon that 1994 N-aquifer simulation, material damage has not occurred. 2006 Findings: Historical data do exist for flow in some area washes; however, the data are limited. According to the USGS, continuous discharge data have been collected

at four streamfiow gauging stations since the mid 1970s. 27 The average annual discharge

at the four gauging stations varies during the period of record. Nonetheless, according

to USGS monitoring data, since 1995 the median winter flows for Moenkopi Wash, Dinnebito Wash, and Polacca Wash have generally decreased. For the four continuously monitored washes, the median winter flows in 2003 were 0.75 ft 3 /s for Laguna Creek, 0.25 ft 3 /s for Dinnebito Wash, 0.10 ft 3 /s for Polacca Wash, and 3.45 ft 3 /s for Moenkopi Wash. By comparison,

the earliest measured median winter flows for Laguna Creek (1997), Dinnebito Wash (1994), and Polacca Wash (1995) were 1.8 ft 3 /s, 0.5 ft 3 /s, and 0.35 ft 3 /s, respectively.

As such, flow reductions

of 50 percent
or more are evident since monitoring began
in those three washes, which easily surmounts
the 10 percent threshold identified

in the CHIA criteria (see Table 2). For Moenkopi Wash, the period of record

is much longer and shows

a general decline since the highest measured value in 1988, except during the last two years where flow has increased. 28 Laguna Creek

1.8 ft 3 /s (1997)
0.75 ft 3 /s- 58% Dinnebito Wash

0.5 ft 3 /s (1994)
0.25 ft 3 /s- 50% Polacca Wash

1.8 ft 3 /s (1995)
0.10 ft 3 /s- 94% Moenkopi Wash

3.2 ft 3 /s (1977)
3.45 ft 3 /s+ 8% The physical monitoring data clearly indicates that base flow in a majority
of the monitored washes have decreased
by more than 10 percent since monitoring began. Material damage

to the N-aquifer

is evident; however, simulated modeling results do not calibrate with the physical monitoring data. Once again, OSMRE’s analysis
of this criterion

is severely limited by its reliance
on computer modeling, but if physical monitoring data were given precedence over modeling, material damage would be evident. As with spring discharge,

to assess impacts
of changes

in base flow to washes this criterion depends
on simulated groundwater modeling results rather than physical monitoring data. The physical monitoring data suggests that base flow in the majority
of monitored washes have decreased
by more than 10 percent since monitoring began. As such, in accordance with the CHIA criteria, material damage

to the N-aquifer is evident; however, OSMRE continues

to rely on simulated modeling results that do not calibrate with the physical monitoring data. Wash/Creek Table
2: Discharge

to N-aquifer washes Earliest Median Winter 2003 MedIan Winter Flows

Flows Change

in Median Flow (percentage)NaturalResourcesDefenseCouncil

j9Flawed Modeling Obscures Evidence

of Material Damage

to the Navajo Aquifer S ince mining began on Black Mesa three decades ago, more than 44 billion gallons
of pristine groundwater have been pumped from the N- aquifer
to feed the Peabody pipeline.
As shown

in the original Drawdown report and again
in this follow-up paper, data collected

by the government often contravene
the government’s
own conclusion that material damage has not occurred. And yet, aided by flaws
in the Interior Department’s criteria, holes in its monitoring program, and basic deficiencies

in its hydrogeologic model, Peabody has been able to allege that the present use of water for slurry will not adversely affect the aquifer and those who depend
on it. Drawdown noted that perhaps the principal deficiency

in the government’s program

is its overreliance

on modeling projections, which tend to obscure on-site evidence
of material damage

as described

in Drawdown and this follow-up publication.
For example, the third of OSMRE’s four material damage criteria, which assesses the aquifer’s discharge

to springs, depends entirely upon modeling, regardless

of what actual data may show. Simulations have also been used in application

of criteria two and four, partly
to distinguish Peabody’s impacts
on water quality and washes from those of the tribes, although results there, too, fail to correspond with on-site trends
or explain their divergence. 30 Relying
on the U.S. Geological Survey model, OSMRE has found that material damage

to Black Mesa’s springs has not occurred, noting how simulated flows “decreased [due to Peabody’s withdrawals]

by less than

1 percent under all pumpage scenarios,” even though seven of nine monitored sites have already exhibited flow reductions well in excess of the government’s

10 percent ceiling. 3 ’ Flaws
in the U.S. Geological Survey’s Two-Dimensional Model Drawdown outlined

a number
of flaws in the U.S. Geological Survey model (“USGS Model”). Besides being misapplied,
the official model was based on assumptions about recharge and other hydrogeological features that have since been called into question. Recharge

is the process by which aquifers are replenished with water,NaturalResourcesDefenseCouncil10as rainfall infiltrates the ground and percolates downward. The physical characteristics

of the soil, the extent of plant cover, the moistness

of surface materials, the intensity
of rainftll, the slope of the landscape, and the presence and depth of confining layers and storage basins can all influence the recharge rate of an aquifer, making calculation difficult. Back in the early

1 980s, the U.S. Geological Survey fixed the recharge rate of the N-aquifer

at about 13,000 acre-feet per year; several later studies, including the crucial Cumulative Hydrologic Impact Assessment completed

in 1989, relied on this estimate

in formulating their conclusions. 32
But there were problems:
the original researchers failed to provide full discussion

or documentation

of the aquifer’s hydrodynamics, begging basic questions about the integrity
of the USGS model, and they overestimated

the region’s annual precipitation, which colored the results. 33 In response

to an internal critique
of the USGS model, Drawdown reported that the U.S. Geological Survey took steps to revise its original estimate: recharge

to the exposed Shonto region
at the northern end of Black Mesa, the region believed

to account for much of the N-aquifer’s recharge, has been downgraded on the basis of detailed geochemical
and isotopic measurements

to between 2,500 and 3,500 acre-feet per year, suggesting that actual recharge

to the aquifer

is but

a fraction
of the government’s original estimate. 34

If this revised figure

is correct, then Peabody’s current withdrawals from the N-aquifer most likely surpass what hydrogeologists would call the aquifer’s “safe yield,”—the difference between

its annual rates of recharge and discharge. 35 Safe yield
is like

a surplus
in an accounting book;

it is the amount left after all the year’s credits (recharge) and debits (discharge) have been logged. ‘What happens

to an aquifer when its safe yield
is exceeded?
As the hydrologist C.V. Theis wrote in 1940,
“a new state of dynamic equilibrium

is reached only by an increase

in recharge,

a decrease

in discharge,

or a combination

of the two.” 36
If an increase

in recharge

is not forthcoming, a decrease

in discharge

to the washes and springs

is to be expected. Other criticisms
of the USGS model have been made. The overarching issue concerning
the USGS model

is the fact that
it is over

a decade old and has not been run by USGS since 1994. LFR Levine-Fricke reports that if forced
to update, the conclusion that no material damage has occurred would very likely not be supported.

In addition, since

a complete water budget (or allocation scheme) for the N-aquifer could not be calculated from available field data, researchers relied upon estimates

in their original study; though revisions were made in subsequent years, fundamentals

of this water budget were not reconsidered
and related assumptions went unexplained. 37

As has also been noted, conclusions regarding the levels of potential leakage from the overlying D-aquifer
are likewise based on insubstantial evidence. 38 Peabody’s 1999 Three-DImensional
Flow Model
Is Fundamentally Flawed In 1999, HIS Geotrans and Waterstone prepared for Peabody

A Three-Dimensional
Flow Model of the D and NAquifers (“1999 Flow Model”)

to develop estimates
of N-aquifer water withdrawals.

In 2002,
at the behest of NRDC, LFR Levine-Fricke provided

a technical review of the 1999 Flow Model and accompanying documentation

and its application

to predicting impacts
on the D- and N-aquifers (appended

to this publication). This review focused
on whether the new model improved the ability
to assess material damage and other disturbances

to the hydrologic balance relative
to CHIA criteria and whether

it accurately simulated responses

to Peabody pumping
on such issues
as groundwater elevations, aquifer discharge, induced leakage, and storage loss in the D- and N-aquifers. The technical review concluded that the 1999 Flow Model

is fundamentally flawed and fails to meet the regulatory requirements. Major flaws include the following: 1. The 1999 Flow Model

is inadequate

to address
all relevant consequences

of mining on the hydrologic balance (and associated, existing CHIA criteria). 2. the model

is otherwise flawed
in important ways that destroy
its utility and credibility, including

its theoretic postulation

of a nearly unlimited supply of water to replace water pumped
by Peabody and mask the effects of Peabody pumping. Natural Resources Defense CouncilEach of these points

is discussed

in turn. First, Peabody relies heavily on the model
to support
its claims that impacts

to the N-aquifer
are minimal. However, Peabody admits that the model has insufficient resolution

to address

a critical issue: diminishment

of flow at sacred and other springs
in the area. 3 ’ The impact of Peabody’s activities
on spring flow is, and has always been,

a central hydrogeologic issue. For example, one of the four CHIA criteria established

by OSMRE establishes

a material damage threshold

of 10 percent reduction

in spring flow. 4 ’ Yet, the 1999 Flow Model simply does not address this issue, thereby precluding OSMRE from assessing impacts

to individual springs, many of which are religiously and culturally integral

to the Hopi in addition

to serving

as sources of potable water. 4 ’ Second, the 1999 Flow Model

is otherwise fatally flawed
in important ways that destroy
its utility and credibility

As documented

in the attached report from expert hydrogeologists

and modelers with LFR, the 1999 Flow Model has numerous inconsistencies

and significant problems. Chief among them, the 1999 Flow Model artificially creates

a nearly limitless supply of water residing

in the D-aquifer that “replaces” water pumped from the underlying N-aquifer

by the coal company for use in its operations. This element of the model fitndamentally obscures impacts and minimizes Peabody’s proportional
role in those that are identified.

In short,
as more filly discussed

in the attached LFR report, the 1999 Flow Model

is inadequate

to support the conclusions contained

in Peabody’s permit application,
nor is it capable of supporting

a finding by OSMRE that material damage
or other disturbances

to the hydrologic balance will not occur
as a result of Peabody operations. 42 It is instructive that an earlier 2002 permit application relying on the 1999 Flow Model contained significant caveats about the utility of the model. For example, Peabody acknowledged
that the agreement between the model and observed water levels (alleged
by Peabody) “does not necessarily mean that the predictions will be accurate.” 43 Peabody also noted that “[e] arlier models produced reasonably good agreement with water-level change information available

at the time of their calibration, but the agreement

of measured and simulated water-level changes degraded with increasing time.” 44 The Significant Shortcomings

of Peabody’s 2005 Supplement In 2005, Peabody released

a supplement

to its Three-Dimensional
Flow Model of the D and NAqufi’rs (“the 2005 Supplement”).
The purpose
of the 2005 Supplement
was to simulate and evaluate five additional pumping scenarios, provide results of additional sensitivity testing, and evaluate whether the models originally presented

in 1999 are able to accurately simulate water level changes from 1997 through 2003 in the Black Mesa monitoring wells. At the behest of NRDC, LFR reviewed the 2005 Supplement

to determine

its ability to address CHIA criteria and resolve outstanding shortcomings outlined

in the 1999 Flow Model (appended to this publication). Peabody’s 2005 Supplement
has three major flaws: 1. Previous concerns regarding the model and its ability
to resolve specific CHIA criteria requirements remain unresolved, including

a failure
to resolve changes

in spring discharge

at the level necessary

to evaluate CHIA criteria. 2. Essential statistics

to support the supplement’s conclusions and facilitate peer review are not made available; rather, only declaratory statements
are provided. 3. The model fails to include D-aquifer water-level data necessary

to quantify leakage from the D-aquifer to the N-aquifer. Each of these issues

is addressed

in turn. First, the previous concerns regarding the model and its ability to resolve specific CHIA criteria requirements remain unresolved.

As noted above, the 1999 Flow Model has insufficient resolution

to address

a critical issue: diminishment

of flow at sacred and other springs
in the area. 45 As noted earlier, this critical concern

is a central hydrogeologic issue, one which the 2005 Supplement fails to address (as pointed out years ago by LFR). The supplement therefore fails to provide the necessary information

for OSMRE

to assess impacts

to individual springs. For example, LFR noted that to assess discharge reductions

at Pasture Canyon spring,

a 10 percent reduction

in spring discharge would require Natural Resources Defense Council

12that the model accurately resolve changes

in spring discharge
of less than

5 gallons per minute
or
8 acre-feet per year at a minimum. The 1999 Flow Model and 2005 Supplement
fail to achieve this critical indicator. Furthermore, LFR notes, if the model were accurately calibrated,

it would show

a reduction

in spring flow of over 19 percent

at Pasture Canyon spring since

1995•46 Second, the 2005 Supplement fails to make available necessary information

to support
its conclusions and facilitate peer review. LFR notes that calibration statistics typically provided

in model validation reports are not made available

to the public, rather qualitative statements
are provided with no statistical showing. 47
For example, the 2005 Supplement simply states that “[tihe four models match the observed water-level changes at the six BM monitoring wells quite well” without making available the information necessary

to verify this statement. The 2005 Supplement acknowledges
this shortcoming when, comparing additional pumping data and simulated model results
to the updated pumping data, the report states: “[tjhis evaluation, which

is not presented here, indicated that there were only small differences between measured and simulated drawdown for the period 1997 through 2000” (emphasis added). The 2005 Supplement fails to conform

to applicable industry standards
for demonstrating model performance. Third, neither the 1999 Flow Model nor the 2005 Supplement include water levels for the confined portion
of the D-aquifer.

In fact, Peabody does not even monitor water levels in the confined portion
of the D-aquifer

as part of its monitoring efforts. This information

is necessary

to directly evaluate the change
in leakage from the D-aquifer

to N-aquifer under the 1999 Flow Model for CHIA Criterion Three. Moreover, it would seem necessary

to calibrate

a model that incorporates
the D-aquifer and is intended,

in part, to quantify leakage from the D-aquifer

to the N-aquifer. Peabody’s 1999 Flow Model continues

to suffer from the same fatal flaws that were left unaddressed in the 2005 Supplement.

In fact, the 2005 Supplement raises

a series of additional concerns that seriously undermine
the utility and predictive accuracy
of the 1999 Flow Model and 2005 Supplement

for determining material damage

to the N-aquifer.NaturalResourcesDefenseCouncil13Controversy Comes
to a Head with Peabody’s New Request for Increased Navajo Aquifer Access T he conflict

is heating
up between the coal company seeking

to exploit the Navajo aquifer and the tribal communities who rely on the aquifer
as a potable water source. Peabody has filed

a request

to extend
its mining operations

in Black Mesa and, despite the evidence

to the contrary, claims that this invasive mining and accompanying water withdrawals
will not damage the aquifer. But physical monitoring data as well as firsthand accounts tell
a story of groundwater depletion that can be traced
to Peabody’s operations

in Black Mesa. Mohave Generating Station Closure Since the 1960s, the Black Mesa mine has produced coal and the N-aquifer has provided water
so that the dirtiest remaining power plant in the Intermountain West, located 273 miles away in southern Nevada, could operate. 48 During this period, tens of billions
of gallons of pristine water have been removed from the N-aquifer, causing material damage

to the aquifer itself and threatening Hopi livelthood and the cultural practices that rely on it. 49 In 1997, environmental groups sued the co-owners

of the Mohave Generating Station (MGS)

to stop its repeated Clean Air Act violations. 5 ° According

to available information,
the 1,580- megawatt MGS plant was releasing
an average of 19,000 tons of nitrogen oxide, 40,000 tons of sulfur dioxide, and 2,000 tons of fine particles

a year into the air above Laughlin. 51 That plume of smog and soot pollution was contributing

to the haze that diminished visibility

at the Grand Canyon. 52

In 1999, MGS co-owners agreed
to retrofit the plant, which supplied customers

in California and in other states, with state-of-the-art pollution controls
by January

1, 2006. But when the MGS co-owners failed to retrofit the power plant and were forced
to shut the plant down, most of Peabody’s water withdrawals from the N-aquifer ceased indefinitely.

To many tribal members, the shutdown

of MGS and the cessation
of mining activities

at Black Mesa mine were necessary steps to preserve the N-aquifer and its springs. 54 But the threat
to the tribes and to the balance of the N-aquifer remains. Natural Resources Defense CouncilPeabody’s Current Request for Increased Access
to the N-Aquifer Peabody

is moving forward

to restart its N-aquifer withdrawals.

In early 2004, Peabody submitted

a permit application

to OSMRE.

In that application, Peabody sought regulatory authorization

to extend mining operations

on Black Mesa for an additional

20 years, while discounting
any negative effects previous mining operations have had on the N-aquifer. 55

In its permit application, Peabody asserts that incontrovertible evidence supports the conclusion that potential hydrologic consequences

of Peabody’s “past, present, and potential future usage of the Navajo aquifer are negligible,” despite the fact that this statement does not correlate with physical monitoring data. 56 The conclusory statements

in Peabody’s latest permit application conflict with empirical data indicating that several of the criteria for material damage

to the N-aquifer have already likely been exceeded.
As noted
in the Drawdown report and this publication, major impacts

to the N-aquifer include: • water levels in that have dipped below the 100-foot protective barrier and, in some locations, below the top of the N-aquifer; • dramatic localized increases

in total dissolved solids,
as well as sulfate and chloride concentrations

at a number
of locations; • diminishment

of flow by more than 30 percent from seven of nine monitored N-aquifer springs, with spring flow reduction

of 50 percent
or more from three of four annually monitored N-aquifer springs; and • substantial reductions

in wash discharge

of more than 50 percent
in three of four monitored washes,

as indicated
by physical monitoring data, in excess of material damage criteria thresholds. 57 In apparent response

to the concerns
of the harm to the N-aquifer that the permit application would raise, Peabody included

a provisional plan to use an alternative water source: the Coconino Aquifer (or “C aquifer”). Critically, Peabody fails to show that C-aquifer water can be withdrawn consistent with OSMRE regulations

or that it is likely to be available

to the mine. 58 Under Peabody’s latest permit application, until C-aquifer water

is available,

if ever, Peabody requests increased access
to the N-aquifer
for all of its operations, including production and resultant transportation

of coal and its new coal washing water requirements. 59 Essentially, under Peabody’s latest permit application,

if the C-aquifer never becomes available,

is substantially delayed,

or if Peabody decides

it is not worthwhile

to pursue, business

as usual would continue
on Black Mesa. As noted earlier, Peabody’s latest permit application suffers from at least two overarching shortcomings when

it comes
to issues related
to the N-aquifer. First, Peabody’s permit application discounts physical monitoring data, concluding that material damage

is not occurring despite monitoring data indicating otherwise. Second,

in addition

to discounting physical monitoring data, Peabody crafted the permit application

to continue

its right to withdraw

as much N-aquifer water
as required for mining and transport operations through the life of the permit, while only making unsubstantiated assurances that
it is committed to seeking an alternative water source, much less that it will be available. 60 These unsubstantiated assurances come
in the face of a requested increase

in the amount
of water that Peabody would be allowed

to withdraw— in excess of 6,000 acre-feet

a year. In short, Peabody’s permit application,

as drafted, would allow Peabody

to increase water withdrawals from the N-aquifer
for the next twenty years despite the serious concerns raised by physical monitoring data already evident

at much lower levels of annual N-aquifer pumping. Peabody’s latest permit application

to OSMRE

is still being examined and will have to undergo environmental review under the National Environmental Policy Act of 1969—a process that will continue throughout 2006.NaturalResourcesDefenseCouncil15Recommendations

for Preserving the Navajo Aquifer T he U.S. government
has an obligation

to protect the Black Mesa water system from groundwater mining,

a practice that virtually
no one defends as an appropriate—let alone the best—use

of a precious resource.

To preserve the Navajo aquifer and the sacred springs and washes

it feeds, NRDC concludes the following steps must be taken to protect the health of this vital water source. • Peabody shouldpermanently
cease groundwater pumping from the N-aquifer.

As reported

in 2000, there

is ample evidence

to suggest that Peabody’s annual withdrawal

of more than

a billion gallons of potable N-Aquifer water (which no one defends

in principle)

is endangering
the ability of the Hopi and the Navajo to draw on groundwater

for subsistence and other needs. Given the evidence—the substantial
fall of water levels in the aquifer; mounting evidence that its recharge rates are substantially lower than originally forecast; evidence
of water-quality degradation

in at least some parts of the aquifer; declines

in outflow from its springs; Peabody’s status
as principal user; potential
for severe, adverse consequences should pumping continue; and the protective principles that underlie the government’s trust relationship with the tribes—it should be the policy of the Department

of the Interior that Peabody cease mining the N-aquifer and refuse Peabody rights to any continued access of the N-aquifer

as posited

in Peabody’s most recent permit application. • OSMRE must deny Peabody’s life-of-mine permit application. OSMRE cannot legally authorize

a life- of-mine permit for the Kayenta and Black Mesa mines based on vague assumptions
and future assurances that an alternative water source may one day be available. • The Interior Department should renew its investigation

of alternatives

to the current pipeline system. The Department

of the Interior should update Phases

1 and
2 and conduct Phase

3 of the three-part study on coal transport alternatives that it began
in the early

1 990s. The Environmental Protection Agency identified a few of these alternatives

in reviewing Peabody’s permit application

10 years ago: replacing water-based coal slurry with

a methanol-based slurry; substituting low-grade water for the pristine drinking water of the N- aquifer; using reclamation technologies

to reduce the total amount
of water needed, regardless

of the source; Natural Resources Defense Council

16and developing

an alternative vehicle for coal transport. 6 ’

It remains for the Interior Department

to update and complete

its comparative analysis and determine which of the available options, singly or in combination is the most environmentally

and economically sound. This analysis can be performed within the context of the Environmental Impact Statement under the National Environmental Policy Act required for Peabody’s latest permit application. 62 The Department

of the Interior should consider,

in addition,

at least one alternative that has not yet been named: the use of reclaimed water from existing treatment facilities

as a replacement

for all or part of the pristine N-aquifer groundwater used in Peabody’s slurry Recycling wastewater

is generally considered sound environmental policy supported

by
a wide range of interests

in the southwestern United States, and NRDC’s investigation

has determined that recycling

in this case may be technically feasible, once the needs of local farmers are met. 63 • The Department

of the Interior should adopt safe yield as its management goal. Under the standard known

as safe yield, users of an aquifer cannot take more than the aquifer’s natural surplus; i.e., the difference between what the aquifer annually acquires through recharge and what
it loses through discharge

to springs and washes and other natural processes. Meeting this standard means developing policies and parameters that will ensure the availability

of groundwater long into the future. Other standards—such

as sustained yield, which sets
a 100-year parameter
for an aquifer’s sustainability—provide neither

a long-term solution

to groundwater overdraft nor an appropriate way to ensure the viability
of peoples that have inhabited the same land for many hundreds
of years. With tribal consent, the Department

of the Interior should adopt safe yield as its management goal for the N-aquifer. I The Department

of the Interior should improve
its monitoring

of the N-aquifer.

To ensure that safe yield standards
are met and that washes, springs, community wells, and other features are protected

in the long run,
it is essential that the current monitoring regime be overhauled. The Interior Department should improve

its metering
of Moenkopi and other washes, take potentiometric measurements

of the D- and Naquifers for
a more accurate assessment

of contamination
risk, and make whatever additional adjustments are necessary

to address the potential impacts that OSMRE has identified.

At the same time,
it should open OSMRE’s material damage criteria, which help define the parameters

of its monitoring program,

to a public process of reexamination
and revision. • The Department

of the Interior should recalibrate

its hydrogeologic model of the N-aquifer. Data compiled
by OSMRE and

a reassessment

of the aquifer’s recharge rate undertaken

by the U.S. Geological Survey suggest that the department’s existing model does not reflect actual conditions. The department should revise its model accordingly.
Of course, making these revisions

to its modeling and monitoring programs should not delay the department

in taking the precautionary steps we have recommended. • With tribal consent, the Environmental Protection Agency should designate the N-aquifer

a “sole source aquifer” pursuant

to the Federal Sole Source Aquifer Protection Program. The federal Safe Drinking Water Act recognizes that sole sources of regional drinking water, whose contamination “would create

a significant hazard
to public health,” require special protection

to ensure their long-term viability. 64 Once an aquifer has officially been designated

a sole source under the program,

no federal funding can be committed

to any project that may result in its contamination. With the tribes’ consent, the N-aquifer should receive this designation from the Environmental Protection Agency. • Tribal sovereignty must be respected, and federal and tribal governments should work cooperatively to manage aquifer resources. The federal government
and the Hopi and Navajo tribes must work together to develop

a viable policy of groundwater management applicable

to reservation lands and modeled
on the safe yield standard
of zero net withdrawals. Fundamental

to the plan should be self-governance

for the tribes with respect
to groundwater management, enforceable limits on withdrawals from the N-aquifer

to ensure Natural Resources Defense Council

17that progress associated with diminished industrial pumping

is not offset or lost by increased pumping
for other nonessential purposes, and regulations that recognize the environmental
and cultural significance

of the N-aquifer and the sacred springs

it feeds. As the tribes make improvements

to infrastructure

in the coming decades, efforts should be made to incorporate acceptable usage levels into their water systems. Natural Resources Defense Council

18Technical Report: Update
of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-aquifer, Black Mesa, ArizonaThisreporthasbeenpreparedbyLFRLevine•Fricke(LFR)attherequestoftheNaturalResourcesDefenseCouncil(NRDC)forthepurposeofupdatingourreviewofpotentialhydrologicimpactstotheN-aquifercausedbygroundwaterwithdrawalsassociatedwithPeabodyWesternCoalCompany(PWCC)miningoperationsintheBlackMesaareaofNortheastern,Arizona.InSeptember2000,LFRprovidedanassessmentofpotentialimpactstotheN-aquiferbasedoncriteriaestablishedbytheU.S.DepartmentoftheInteriorOfficeofSurfaceMiningReclamationandEnforcement(OSMRE),(LFR2000).ThisreportisintendedtoupdateLFR’sfindingsbasedonmorerecentlyobtainedmonitoringdata,including,butnotlimitedto,theUnitedStatesGeologicSurvey(USGS)annualreportsonGroundwater,SurfaceWaterandWaterChemistryfortheBlackMesaArea,NortheasternArizona(TruiniandThomas,2004;TruiniandPorter2005),andtheUSGSreportontheHydrogeologyoftheD-aquiferandMovementandAgesofGroundwaterDeterminedfromGeochemicalandIsotopicAnalysis,BlackMesaArea,NortheasternArizona(TruiniandLongsworth2003).ExecutiveSummaryTheobjectivesofthisreportaretodeterminewhethermaterialdamagecanbeidentified,baseduponCHIAcriteriaestablishedbyOSMRE.Toaccomplishtheobjectives,LFRcomparedmonitoringdatacontainedintheannualUSGSmonitoringreportsandotherpertinentdocumentswiththecriteriaasexplainedintheCHIA.Additionalresourcematerialwasalsoreviewedtoestablishhistoricconditionsandevaluatecurrenttrends.ToevaluatetheimpactofgroundwaterwithdrawalsontheN-aquifer,CHIAcriteriawereestablishedtoallowforcomparisonoffuturegroundwaterlevelsandsurfacewaterflowstobaselinewaterlevelsandflowsestablishedintheCHIA.ThehydrologicconcernsaddressedintheCHIAareprimarilyrelatedtothediminutionoftheN-aquiferwaterresourcerelatedtopotentialadverseimpactsonwaterquantityandqualityTherequirementofthefirstCHIAcriterionistomaintainapotentiometrichead100feetabovethetopoftheN-aquiferatanypointtopreservetheconfinedstateoftheaquifer.SincetheSeptember2000report,waterleveldeclineshavecontinuedtobeobservedinmostN-aquifermonitorwells.WithrespecttoboththeKayentaWestandBM3wells,monitoringdatashowthatthewaterlevelsinthosewellshaveperiodicallydroppedbelownotonlytheCHIAcriterialevelestablishedtoprotecttheaquifer,buttheelevationofthetopoftheN-aquiferitself.ThisaddsadditionalconcernsregardingpotentialmaterialdamagetotheN-aquifer.ThefailureofthesewellstomeetthecriterionisdismissedbyOSMREasbeingtheresultofmunicipalpumpingintheKayentacommunityeventhoughthetotalmunicipalpumpingatKayentarepresentslessthan12percentoftheindustrialpumpingbyPWCCashortdistancesouthofKayenta.NotwithstandingNaturalResourcesDefenseCouncil19OSMRE’s exception
for the BM3 well,
it appears that material damage

to the hydrologic balance of the N- aquifer has occurred based upon CHIA Criterion

1. The second CHIA criterion was established

to prevent degradation

of N-aquifer water quality due to induced leakage of poor quality groundwater from the overlying D-aquifer.
To date, the CHIA criteria evaluation
has relied on trends
in inorganic water quality
to assess whether material damage

is occurring; however, such an analysis cannot provide

a quantitative result to demonstrate that induced leakage from PWCC pumping

is less than 10 percent of pre-stress leakage levels
as required
by the CHIA. Documentation

for
a new groundwater model prepared
on behalf of PWCC (GeoTrans 1999) included

a water balance for each model layer under steady state conditions.
For the steady state simulation, approximately 4,100 acre-feet per year of recharge

to the upper N-aquifer layer
is derived from vertical leakage from the overlying layer (Carmel Formation); however,
no discussion was provided regarding the areal distribution

of observed leakage
or whether changes

in vertical leakage are observed between pre-stress and post-stress model simulations. Recent model simulations
for various future pumping scenarios indicate that the N-Aquifer southeast
of Pinon represents

a source of recharge (or storage) for pumping stresses

to the north. This
is the same area where vertical leakage has been documented

by changes

in inorganic water quality; While the CHIA criterion can not be quantitatively evaluated based on available data, indirect evidence
of material damage associated with induced leakage exists. The remaining two CHIA criteria were established

to assess whether PWCC withdrawals would result in N-aquifer discharge reductions

of 10 percent
or more to springs
or base flow in washes. OSMRE relies on groundwater modeling rather than physical monitoring

to assess whether material damage

is occurring, and has determined that material damage has not occurred.

It remains unclear how

a conclusion
can be made that no material damage

is evident based on simulated modeling results while physical monitoring data suggests otherwise. Both the USGS and PWCC groundwater models used to make that judgment
are admittedly incapable

of resolving significant changes

in spring discharges

at the level required
by the CHIA criteria. The physical monitoring data suggests that base flow in many of the monitored springs and washes have decreased

by more than 10 percent since monitoring began.
If the model were updated and forced
to calibrate to the physical data that has been collected, the conclusion that no material damage has occurred would not be supported.

As such, in accordance with the CHIA criteria, material damage

to the N-aquifer

is evident; however, simulated modeling results do not calibrate with the physical monitoring data. Introduction The Cumulative Hydrologic Impact Assessment (CHIA) criteria used were established

by OSMR.E

in April 1989 to determine whether mine-related groundwater withdrawals resulted

in material damage

to the N- aquifer. On March

8, 1991,
as part of a legal settlement, OSMRE agreed
to review Black Mesa N-aquifer monitoring data against the CHIA criteria and thereafter report their findings

to the Navajo Nation, Hopi Tribe, and PWCC

in annual reports. For the September 2000 report, LFR compared Black Mesa area monitoring data against the material damage criteria established

in the 1989 CHIA. Based on our evaluation, LFR reported these findings: • Based upon groundwater modeling performed
for the CHIA, OSMRE concluded that none of the projected impacts associated with proposed mine operations exceeded the material damage criteria; therefore, OSMRE. anticipated

no material damage

to the hydrologic balance within the study area. • Flaws in the CHIA criteria and dependence

of the criteria on an underlying groundwater flow model hindered evaluation. These flaws raise questions regarding OSMRE’s conclusions. • Three of the four material damage criteria may not necessarily

be protective

of N-aquifer water resources because they are either directly
or indirectly dependent upon modeling results from

a model not specifically designed

to evaluate those criteria. OSMRE bases its analysis
of CHIA Criteria

3 and
4 on the latest USGS N-Aquifer model or makes no evaluative attempt. Since the final CHIA was released

in 1989, USGS has performed modeling simulations twice. The most recent modelingNaturalResourcesDefenseCouncil20results are contained

in the1992-1993 USGS progress report released

in 1995. Therefore,

all OSMRE material damage analyses are based upon pre-1995 modeling results. Analysis
of N-aquifer criteria

as proposed

in the 1990 CHIA has not occurred since 1994 data was evaluated. Modelers concede that the underlying model was not designed

to evaluate impacts

at individual springs or wells. As such, the model can not adequately simulate spring discharge with the level of precision necessary

to evaluate CHIA criteria. • Issues with the CHIA evaluation methods aside, groundwater elevation monitoring data show that material damage can be concluded based upon CHIA Criterion

1. • If actual monitoring data were given precedence over predictions based on model output,

a review of other CHIA criteria would likely support the conclusion that material damage has occurred. The Black Mesa monitoring data indicate that excessive pumping

of the N aquifer has caused groundwater level declines and spring discharge reductions exceeding guidelines established

in the CHIA. Data trends further indicate that additional material damage

is imminent. Objective The objectives

of this report are to determine whether material damage can be identified, based upon Black Mesa CHIA criteria. To accomplish
the objectives, LFR compared monitoring data contained

in the annual USGS monitoring reports and other pertinent documents with the criteria

as explained

in the CHJA. Additional resource material was also reviewed

to establish historic conditions and evaluate current trends. The scope of this evaluation

is limited

to impacts
of pumping
on the N-aquifer groundwater resource and does not address other pertinent criteria such as surface water quality. Hydrogeology

of the Black Mesa Area The Black Mesa region of northeastern Arizona

is located

in the Plateau Uplands Hydrogeologic Province and
is characterized

by high, isolated mesas and steep-walled canyons. The Black Mesa, with an area of approximately 5,400 square miles,

is underlain
by thick sequences

of relatively flat-lying, well-lithified sedimentary rocks. The mesa land surface rises steeply on the East Side to more than 3,000 feet above the surrounding lowland, whileit slopes gradually toward the lowland

to the west. A thin veneer of recent unconsolidated sediments covers the surface of the mesa with floodplain alluvial deposits generally occurring

in narrow bands along major drainage channels. The underlying sedimentary rock sequence, Permian

to Late Tertiary

in age,
is highly variable and consists
of up to 10,000 feet of interbedded sandstone, mudstone, siltstone, limestone, coal, and gypsum deposits (Lopes and Hoffman 1996). Several water-bearing zones (aquifers) underlie the Black Mesa area. The primary aquifer
in the Black Mesa area
is the Jurassic-age N-Aquifer, which includes the highly productive Navajo Sandstone and the underlying Wingate Sandstone (Cooley

et al. 1969). The N-aquifer

is more than 1,200 feet thick in the northwestern portion
of the mesa and thins toward the southeast corner of the mesa. The N-aquifer

is unconfined around the margins
of the mesa whereit is exposed and overlying sediments have been removed by erosion. Beneath approximately 3,500 square miles of Black Mesa, however, the N-aquifer

is fully saturated and confined
by sediments

of the overlying D-aquifer and Carmel Formation (Lopes and Hoffman 1996). Recharge

to the N aquifer occurs primarily

in the area near Shonto, north and northwest

of the mesa, where the N-aquifer

is exposed

at the surface (Lopes and Hoffman 1996). The D-aquifer generally consists
of isolated thin sandstone layers of the Morrison Formation and the Cow Springs Member
of the Entrada Sandstone, separated
by thick sequences

of lower permeability mudstone and siltstone (Cooley

et al. 1969). The thickness
of the D-aquifer varies from less than 100 feet in the area northwest

of the mesa to 1,300 feet in the central portions
of the mesa (Lopes and Hoffman 1996). Groundwater occurs under both unconfined and confined conditions within the D-aquifer. Hydraulic heads
in the D-aquifer
are as much
as 600 feet higher than those of the underlying N-aquifer, resulting

in a significant potential downward gradient toward the N-aquifer. Recharge

to the D-aquifer primarily occurs along the eastern slope of the mesa where the unit
is exposed

at higher elevations (Lopes and Hoffman 1996).NaturalResourcesDefenseCouncil21The D- and N-aquifers
are separated
by
a lower-permeability confining unit, or aquitard, consisting

of the lower Entrada Sandstone and the Carmel Formation. This confining unit consists
of generally less than 300 feet of mudstone and silty sandstone, which restricts the downward flow of poor quality water from the overlying D-aquifer into the underlying N-aquifer; however, recent studies have shown that leakage of poor quality water from the D-aquifer

to the underlying N-aquifer

is evident and has occurred

in the southeast portion of the mesa (Truini and Longsworth 2003). Groundwater flow in the N-aquifer

is generally from the recharge area north of the mesa, from surface elevations greater than 6,300 feet above sea level, toward the south-southeast beneath Black Mesa (Lopes and Hoffman 1996). Because the thickness
of the N-aquifer decreases significantly

in the southern portion of the mesa, the direction
of regional groundwater flow beneath the central portion
of the mesa generally diverges toward the northeast and southwest (Lopes and Hoffman 1996). Groundwater from the N-aquifer discharges

to Laguna Creek and Moenkopi Wash,

as well as to springs along the margins
of the mesa where the N-aquifer outcrops. Water withdrawn from the N aquifer takes many years to be replenished through the recharge area; therefore, long-term impacts
on springs may result from groundwater pumping. Precipitation

in the Black Mesa area ranges from

7 inches per year to 18 inches per year near Shonto and in the higher elevations

of the mesa (Lopes and Hoffman 1996). Precipitation recharging
the shallow unconsolidated sediments and the upper D-aquifer results
in shallow flow outward toward the margins
of the mesa and the occurrence

of springs along surface drainage-ways. Basis of Evaluation Pursuant

to the Surface Mining Control and Reclamation
Act of 1977, OSMRE performed

a CHIA of PWCC’s Black Mesa/Kayenta Mine in the Black Mesa Area of Northeastern Arizona.

In January 1988, OSMRE issued

a copy of their CHIA for the Black Mesa area. In April 1989,

a revised CHIA for the Black Mesa was issued. Differences between the Draft and Final CHIA were discussed

in Section 5.2 of LFR’s September, 2000 report evaluating cumulative hydrologic impacts
on the N Aquifer (LFR, 2000). The purpose
of the Black Mesa CHIA was to determine whether Peabody’s proposed extraction

of approximately 4,000 acre-feet
of water per year from the N-aquifer would cause material damage

to the aquifer. To evaluate the impact of groundwater withdrawals

on the N-aquifer, CHIA criteria were established

to allow for comparison

of future groundwater levels and surface water flows to baseline water levels and flows established

in the CHIA. Within the CHIA, pertinent baseline years are listed
as January

1, 1980 through December
31, 1984 for surface water quantity evaluations, and 1985 for groundwater level evaluations. The hydrologic concerns addressed

in the CHIA are primarily related
to the diminution

of the N-aquifer water resource related
to potential adverse impacts
on water quantity and quality. Discussion Table

1 lists the Black Mesa CHIA criteria standards that are specifically pertinent

to N-aquifer groundwater resources. The status of each of those criteria

as reported

in LFR’s September 2000 report and this report are included for reference. Below

is a summary
of Black Mesa CHIA criteria along with associated observations from our evaluation. Criterion

1.: MaIntain potentlometric head 1.00 feet above top of N-aquifer

at any point to preserve confined state of aquifer. This criterion was established

to protect the structural stability of the N-aquifer due to a reduction

of potentiometric head and water stored within the aquifer. Confined aquifers are typically dependent upon water pressure contained within the matrix pore space to retain structural integrity; without the additional support
of pore space water pressure some aquifers can compact, causing

a permanent loss of storage capacity and, in some cases, surface land subsidence. Because the N-aquifer

in the Black Mesa Area
is comprised primarily
of cemented sandstone,
the likelihood

of aquifer compaction occurring

is lessened. This likelihood

of N-aquifer compaction

is recognized

on pages

5 6 of the CHIA; however,
“as an added insurance”
the criterion

is retained.NaturalResourcesDefenseCouncil22Standard
Status
In 2000 Criterion

1: “Maintain potentiometric Groundwater level
is Groundwater level
is within 100 feet of Structural head of 100 feet above within 100 feet of top the top of N-aquifer

in two monitored stability

top of N-aquifer

at any

of N-aquifer

in two wells and has periodically dropped point to preserve confined monitored wells. below the top elevation

of the Nstate of aquifer.”

aquifer itself. Criterion

2: “A value of leakage from Leakage

is not directly Leakage

is not adequately assessed; Water

the D-aquifer not to exceed measured; analysis

of analysis
of related data reveals quality

10 percent from mine- related data suggests increasing trends

in inorganic related withdrawals.”

that water quality

is constituents

in the N-aquifer

in some threatened

in some areas. areas. Criterion

3: “A discharge reduction Seven of nine monitored Three of four monitored springs Discharge

of 10 percent

or more springs show

a decline continue

to show

a decline

in excess to springs caused
by mine-related

in excess
of 10 percent,

of 10 percent;

if the model were withdrawals based on according

to available updated and forced
to calibrate, the results
of N-aquifer

field data. conclusion that no material damage simulation.”

has occurred would not be supported. Criterion

4: “A discharge reduction Moenkopi Wash shows

a Three of four continuously monitored Discharge

of 10 percent

or more decline
of approximately wash gauging stations show decline to washes caused
by mining.”

25 percent; status of
of at least 50%; material damage other washes

is difficult

is evident however simulated to ascertain, modeling results do not calibrate with monitoring data. Status
In 2006 Results of the September 2000 Assessment In the September 2000 report, LFR located measuring point elevations
for the N-aquifer wells listed in the USGS progress reports and evaluated measured water levels based upon this criterion. Of the 15 wells listed
as existing within the confined portion
of the N-aquifer

in the USGS progress reports, six had

a potentiometric head within 100 feet of the top of the N-aquifer. Three of those six wells (1OT-258, bR-i 11, and Sweetwater Mesa) are located near the aquifer boundary between confined and unconfined portions
of the N-aquifer and behave more like wells existing

in the unconfined portion
of the aquifer.

A fourth well, the Rough Rock well, is located

in the unconfined portion
of the N-aquifer. Of the 11 wells monitored that were known
to be installed

in the confined portion
of the aquifer, two (Kayenta West and BM3) were found to have

a potentiometric head less than 100 feet above the top of the N-aquifer. The groundwater elevation

in the Kayenta West well was reported

in 1996 to be more than 11 feet below the approximated

top of the N-aquifer and in 1998 to be approximately

0.2 feet above the top of the N-aquifer. The groundwater elevation

at BM3 was reported

in 1996 to be within approximately

1 foot of the top of the N-aquifer and in 1998 to be approximately

1.6 feet above the top of the N-aquifer. OSMRE acknowledged
this criterion failure
at BM3 in their material damage reviews. However, since the static water level in this well was 99 feet above the top of the N aquifer when

it was first installed (1959) OSMRE concludes that “material damage

to the hydrologic balance
of the N-aquifer, caused by mining, with respect
to maintaining
the potentiometric head above the top of the N-aquifer,
has not occurred.” Monitoring data indicate

a water level decline

in the BM3 well more than 93 feet since the pre-stress
(or pre-mining) period. Appendix Table

1: The CHIA criteria 1 “The criteria listed here were established

by OSMRE

in its Cumulative Hydrologic Impact Assessment

of the Peabody Coal Company Black Mesa/ Kayenta Mine (1989), pp. 6-20 to 6-45 and 7-3 to 7-5. Assessments made
in the column marked “status” are based on the analysis presented below. Natural Resources Defense Council

23OSMRE did not include

a discussion

of the Kayenta West well inits material damage reviews nor do they include any explanation
for the exclusion
of Kayenta West data from their reviews. Monitoring data collected from the Kayenta West well were included

in the USGS progress reports; however, these data were omitted from the OSMRE reviews. The USGS monitoring data indicated

a water level decline
in the Kayenta West well of more than 69 feet since the pre-stress period. CHIA Criterion

1 Update Since the September 2000 report, water level declines have continued

to be observed

in most N-aquifer monitor wells. Still, only monitor well BM3

is identified
by OSMRE

as not meeting the CHIA Criterion

1 objective
of having

a groundwater elevation
of at least 100 feet above the top of the N-aquifer

in the confined portion of the aquifer. The failure of this well to meet the criterion

is dismissed
by OSMRE

as being the result of municipal pumping

in the Kayenta community OSMRE states in their 2004 Annual Hydrologic Data Report that 516 acre-feet were withdrawn from the N-aquifer

at Kayenta, accounting
for 38% of all nonindustrial pumping from the confined portion
of the aquifer. They don’t mention that the total municipal pumping

at Kayenta represents less than 12% of the industrial pumping
by PWCC

a short distance south of Kayenta. Furthermore, OSMRE does not include

a discussion

of the Kayenta West well in its material damage reviews because the USGS reported that the well had recently been pumped and water level measurements were not considered representative. Nevertheless, historical monitoring data collected from the Kayenta West well show that this well would not meet the CHIA Criterion

1 objective, andit appears that material damage to the hydrologic balance of the N-aquifer has occurred based upon CHIA Criterion

1. For the BM3 well, water levels have fluctuated (both up and down) by approximately

10 feet from the levels reported

in the September 2000 report. The most recent monitoring data indicate that for the year 2004, groundwater elevations
are approximately

2.3 feet above the top of the N-aquifer.

As such, this monitor well continues

to fail CHIA Criterion

1. Notwithstanding OSMRE’s exception
for the BM3 well,it appears that material damage

to the hydrologic balance
of the N-aquifer has occurred based upon CHIA Criterion

1. With respect
to both the Kayenta West and BM3 wells, monitoring data show that the water levels in those wells have periodically dropped below not only the CHIA criteria level established

to protect the aquifer, but the elevation
of the top of the N-aquifer itself. This adds additional concerns regarding potential material damage

to the N-aquifer. The 100 foot threshold
for CHIA Criterion

1 was intended

as a buffer
to protect the confined state of the aquifer. As the water levels drop below the confining layer, the aquifer begins
to dewater and air enters the previously saturated pore spaces. Even if water levels rebound,
air can become entrained in the pore spaces and can reduce the permeability
and storage capacity
of the aquifer
in the area where the overdraft occurred.

In addition, the introduction

of air can alter aquifer chemistry and result in damaging reactions such as the formation

of iron and manganese oxide precipitates. Such impacts may be irreparable.Criterion2: AvalueofleakagefromtheD-aquifernottoexceed10percentfrommine-relatedwithdrawals. Continued stresses on the N-aquifer and associated water level declines,

as observed, will increase vertical gradients and potentially induce vertical leakage of poor quality water from the overlying D—aquifer. This criterion was established

to prevent degradation

of N-aquifer water quality due to induced leakage
of poor quality groundwater from the overlying D-aquifer. In order to quantify leakage from the D-aquifer

to the N-aquifer, water level elevations
for both aquifers and the vertical hydraulic conductivity

of the confining unit separating
the aquifers are needed. However, since D-aquifer water level data
is not regularly monitored, other approaches must be used. Other methods of evaluating D-aquifer leakage

to the N-aquifer include inorganic water quality monitoring from the D- and N-aquifers and groundwater flow and transport modeling. To establish and evaluate this criterion for the CHIA, OSMRE used the USGS N-aquifer model. Specifically,
the CHIA evaluated the model’s simulation

of predicted changes

in the annual volume of leakage from the D-aquifer

to the N-aquifer attributable

to mine-related withdrawals. The CHIA predicted
no significant change
in volume
of D-aquifer leakage

to the N-aquifer
for the simulated period.NaturalResourcesDefenseCouncil24Results of the September 2000 Assessment In its annual material damage reviews, OSMRE used inorganic water quality monitoring

to analyze for induced leakage. This approach was dependent upon historical inorganic water quality data for the area of study. In the Black Mesa area, the N aquifer generally has lower inorganic constituent content, including major ions and cations such as chloride and sulfate, than the D-aquifer. One measure
of the presence
of inorganic constituents

is the amount
of Total Dissolved Solids (TDS) expressed

in milligrams
per liter. In OSMRE’s analysis, where induced leakage from the D-aquifer

is occurring,

an increase

in TDS would be anticipated

in the N-aquifer. Yet, where increases

in TDS have been observed for N-aquifer wells, some justification
was made to minimize the increasing values. While increasing TDS trends were observed for multiple monitoring locations, the trends were noted
to be “small”
or “statistically insignificant.” OSMRE concluded that “material damage

to the hydrologic balance of the N-aquifer, caused by mining, with respect to leakage from the D-aquifer

to the N-aquifer,
has not occurred.” OSMRE based its conclusion upon inorganic water quality analysis only; other methods
of analysis were not attempted.
No attempt was made
to correlate the trends of increasing TDS with the material damage criterion. If leakage

to the N-aquifer were estimated

as proposed

in the draft CHIA by evaluating
the magnitude of N-aquifer water level declines and associated changes

in the vertical gradient between the D-aquifer and the N-aquifer,

a conclusion

of material damage

to the N-aquifer water quality would be more likely. The N-aquifer potentiometric head was more than 100 feet below the baseline altitude

in at least two of the monitored wells (Pinon and Keams Canyon). Additionally, data trends for at least four additional wells (BM2, BM3, BM5, and BM6) indicate that groundwater levels would soon be more than 100 feet lower than the baseline altitude

in those wells. Ultimately,

six or more of the eleven monitored wells would likely exhibit groundwater level declines more than 100 feet before mining operations cease. CHIA Criterion

2 Update The CHIA criteria set a 10 percent increase

in induced leakage attributed

to mine-related withdrawals

as the basis for determining material damage

to the N-aquifer. While physically quantifying
the amount
of induced leakage associated with mine-related withdrawals may not be possible, estimates could be based on the fact that the amount
of leakage induced
by groundwater withdrawals would increase proportionally to the increased vertical gradient resulting from those withdrawals [i.e., from Darcy’s Law: Q (flux)= K (hydraulic conductivity)

x I (gradient)

x A (area)].
In other words, everything else being equal, an increase

in the vertical gradient
by 10 percent would increase the vertical flux of leakage by 10 percent. However, rather than attempting

to estimate induced leakage through water-level monitoring and changes

in vertical gradients or using water balance results from groundwater modeling, OSMRE looks
at inorganic water quality

as an indirect indicator
of induced leakage

to make the conclusion that material damage has not occurred. Recent monitoring data provide evidence
of increasing trends
in inorganic constituents

in the Naquifer, including chloride and total dissolved solids, particularly

in the southeast portion
of Black Mesa near Rough Rock, Pinon, and Keams Canyon. Induced leakage resulting from groundwater withdrawals does not necessarily occur in the immediate vicinity
of the pumping stresses, ratherit can occur
at some distance away where resistance

to vertical flow
is reduced and leakage can provide

a source of recharge

to offset those pumping stresses. As such, evidence
of induced leakage from the D-aquifer

to the N-aquifer

in the southern portion
of Black Mesa may potentially

be related
to groundwater withdrawals

by PWCC further
to the north. In 2003, the USGS issued

a report on the Hydrogeology

of the D-aquifer and Movement and Ages of Groundwater Determined from Geochemical
and Isotopic Analysis, Black Mesa Area, Northeastern Arizona (Truini and Longsworth 2003). That report included

a discussion

on groundwater leakage from the D-aquifer to the N-aquifer based on geochemical
and isotopic data analysis and concluded that leakage has occurred from the D-aquifer

to the N-aquifer
for thousands

of years, and most likely occurs
in the southern part of Black Mesa. Unfortunately,

the report avoids any quantitative discussion

of the change
in vertical gradients between the D- and N-aquifers from pre-development

to post development times.
A separate USGS report (Thomas 2002) states that groundwater monitoring

of the N-aquifer has shown that vertical drawdowns have increased the differences between the potentiometric surfaces
of the D- and N-aquifers

by greater than oneNaturalResourcesDefenseCouncil25thirdintheareaofmostapparentleakage.The2003USGSreportsuggeststhatamorequantitativeanswertoobservedchangeswillrequireadditionalinformationontheCarmelFormation(theaquitardseparatingtheD-aquiferandthen-Aquifer)andsimulationmodeling.Historically,theCHIAevaluationreliedontheoriginalUSGSN-aquifergroundwatermodelandconcludedthatnosignificantchangeinleakagewasevidentforthesimulationperiod.Sincethen,PWCChasdevelopedanewmodelthatincorporatesboththeD-aquiferandtheNaquifer.Documentationforthenewmodelincludedawaterbalanceforeachmodellayerundersteadystateconditions.Forthesteadystatesimulation,approximately4,100acre-feetperyearofrechargetotheupperN-aquiferlayerisderivedfromverticalleakagefromtheoverlyinglayer(CarmelFormation);however,nodiscussionwasprovidedregardingthearealdistributionofobservedleakageorwhetherchangesinverticalleakageisobservedbetweenpre-stressandpost-stressmodelsimulations.ThiswouldseemlikealogicalandnecessaryevaluationtoincludeconsideringthespecificrequirementsoftheCHIAcriteria.Regardlessofthemodelingandwater-qualitymonitoringeffortsthathavebeendonetodate,therehavebeennoattemptstoprovidequantitativeestimatesofeitherhorizontalfluxorverticalinducedleakagebasedonobservedchangesinthehorizontalgradientintheN-aquiferortheverticalgradientbetweentheD-aquiferandtheN-aquiferfrompre-stresstopost-stressperiods.HorizontalgroundwatergradientsintheN-aquiferhavechangedsignificantlyinthesouthernportionofBlackMesasincetheintroductionofPWCCwithdrawals.ThemostrecentmodelsimulationsindicatethatgroundwaterflowintheN-aquifersoutheastofPinonistothenorthandrepresentsasourceofstorage(orrecharge)forpumpingstressestothenorth.Thisareaisalsowhereverticalleakagehasbeendocumentedbychangesininorganicwaterquality.WhiletheCHIAcriteriacannotbequantitativelyevaluatedbasedonavailabledata,indirectevidenceofmaterialdamageassociatedwithinducedleakageexists.Inshort,basedupontheinformationprovided,theimpactofincreasedverticalgradientsonthepotentialforincreasedinducedleakagefromtheD-aquiferasaresultofPWCCwithdrawalsfromtheN-aquiferhasnotbeenadequatelyassessed.Inadditiontoconcernsaboutinducedleakage,availablereportsdonotaddressthepotentialformanmadeconduitsthatlocallymayimpactwaterqualityintheN-aquifer.Inparticular,wellsinthePWCCwellfieldarescreenedacrossmultipleaquifersand,assuch,whenthewellsarenotpumpingadirectverticalconduitexistsbetweentheunits.Ifthewellsarenotpumpedforasignificantperiodoftime,waterthatis“injected”intotheN-aquiferfromoverlyingaquifersundernon-pumpingconditionscouldsignificantlyimpactwaterqualityintheN-aquifer.CriterIon3:Adischarge(fromN-aquifersprings)reductionof10percentormore,causedbymine-relatedwithdrawalsbasedonresultsofN-aquifersimulation..ThiscriterionwasestablishedtoprotectthenaturalspringsintheBlackMesaarea.Wellcapturegenerallyresultsinreduceddischargefromtheaquifer,inducedleakagetotheaquifer,orsomecombinationofthosetwo.OSMREusedtheN-aquifergroundwatermodeltoestablishandevaluatethiscriterionfortheCHIA.TheybasethecriteriononpresentandfutureN-aquifersimulations.Apparently,whenmodelupdatesareunavailablethiscriterionisbaseduponthemostrecentmodelresultsornomaterialdamageevaluationisattempted.WithintheCHIA,onlyonespringarea(PastureCanyon)appearstohavebeenevaluated.TheCHIApredicted“outflowtothespringsinPastureCanyonwouldnotbeaffectedbythedurationofpumpingatthemine.”However,laterinthesameparagraph(page6-39)OSMREstatesthatthesimulatedoutflownumbersforPastureCanyon“shouldbeusedwithcautionbecausethemodeldoesnotadequatelyrepresentimportantdetailsofthelocalgeologyinthisarea.”Theyalsostate“reliableestimationofchangesinflowofthePastureCanyonspringswouldrequiredetailedstudyandmodelingofthatlocalarea.”ResultsoftheSeptember2000AssessmentInitsannualmaterialdamagereviews,OSMREbaseditsanalysisofthiscriteriononthelatestUSGSNaquifermodelormadenoevaluativeattempt.SincethefinalCHIAwasreleasedin1989,theUSGShadperformedmodelingsimulationstwice.Themostrecentmodelingresultswerepresentedinthe1992-1993USGSprogressreportreleasedin1995.Therefore,allOSMREmaterialdamageanalyseswerebaseduponNaturalResourcesDefenseCouncil26pre-1995 modeling results. OSMRE concluded either that based upon “the most recent
N aquifer computer model simulation, material damage

to the hydrologic balance of the N-aquifer, caused by mining, with respect to N-aquifer discharge has not occurred”

or thatit “could not determine whether

or not material damage

to the hydrologic balance of the N-aquifer has occurred” due to a lack of modeling results. Either way, analysis
of this criterion

as proposed

in the 1990 CHIA had not occurred since 1994 data was evaluated. Discharges
for multiple springs located
in the Black Mesa area have been monitored and the USGS progress reports contain some of this data. LFR searched the progress reports and other USGS water use reports

to obtain spring discharge data for analysis. Of the nine springs for which discharge data were available, seven showed

a decline of 30 percent
or more. Flows had apparently increased

in two springs (Dennehotso, Hard Rocks); however, original flows at Hard Rocks were only estimated, and the magnitude of change
in flow from the spring near Dennehotso tended
to imply that some unknown change(s) may have occurred (e.g., new monitoring location, nearby construction). Some of the monitoring data were questionable
due to variable monitoring locations and the lack of any attempt
by the USGS
to correlate them. Not only had most springs experienced

a discharge reduction

in excess of 30 percent, but the majority
of those appeared

to have decreased
by more than 50 percent (Rock Ledge, Moenkopi School, Many Farms, Whiskey, and Pasture Canyon). Hence, regardless

of the monitoring data deficiencies, material damage appeared obvious based upon actual conditions.

It was unclear why the modeling simulations had not been adjusted (calibrated)

to better represent observed decreases

in spring discharges. CHIA Criterion

3 Update The USGS report “Ground-Water, Surface-Water,
and Water Chemistry Data, Black Mesa Area, Northeastern Arizona—2003-2004” (Truini and Porter2005) contains recent data for four springs that discharge from the N-aquifer.
Of the four springs, three are located on the southwestern
side of Black Mesa (Pasture Canyon, Moenkopi School, and Burro) and the other

is on the northeastern
side of Black Mesa (unnamed spring near Dennehotso). Annual discharge data dating back to at least the early

1 990s are provided. Some historic discharge data (pre-development)

are also provided.

A graph showing trends
in discharge
for all four springs is presented, although the data
is plotted on a logarithmic scale making interpretation difficult.

A closer look at the data clearly shows an overall reduction

in spring discharge
for the three springs on the southwest side of the mesa. Discharge from the unnamed spring near Dennehotso
has fluctuated over time making

a definitive analysis
of the overall trend more difficult; however, the two lowest measured discharges observed since annual measurements commenced

in 1992 occurred within the last three years. Using only the annual data collected at the same location for each spring, estimates
of discharge reduction since monitoring began are 24 percent at Moenkopi,

19 percent

at Pasture Canyon, and 50 percent

at Burro. Considering that industrial pumping at PWCC represents the single largest stress on the N-aquifer (roughly
75 percent
of withdrawals from the confined portion
of the N-aquifer

in 2003), monitoring data shows that material damage has occurred based on the CHIA criteria

(a reduction

of discharge

of 10 percent
or more).
If other historic spring discharge data were considered, observed discharge reductions would be much greater (70 percent

at Moenkopi and 85 percent

at Pasture Canyon). It remains unclear how

a conclusion
can be made that no material damage

is evident based on simulated modeling results under both the USGS model and PWCC model while physical monitoring data suggests otherwise. The groundwater model used to make that judgment

is admittedly incapable
of resolving significant changes

in spring discharges

at the level required
by the CHIA criteria. Physical monitoring data continue

to show that material damage,

as defined by the CHIA criteria,

is occurring.

If the model were updated and forced
to calibrate

to the physical data that has been collected, the conclusion that no material damage has occurred would not be supported. Criterion

4: A discharge (from N-aquifer

to washes) reduction

of 10 percent
or more, caused
by mining. This criterion was established

to prevent excessive reduction

of flow in the Black Mesa area washes due to reduction

of N-aquifer discharge

to the washes. When

a stream

is in communication
with an aquifer and theNaturalResourcesDefenseCouncil27hydraulicheadoftheaquiferisgreaterthantherelativeelevationofthestream,waterwilldischargefromtheaquiferintothestream(gainingstream).Asheadpotentialswithintheaquiferdecrease,thedischargetothegainingstreamwilldiminish.Iftheheadpotentialwithintheaquiferdecreasesbelowtherelativeelevationofthestreamchannel,thestreamwillbegintolosewatertotheaquifer(losingstream).WithintheCHIA,theN-aquifermodelwasagainusedtoevaluatethepotentialformaterialdamageduetoreducedbaseflowdischargefromtheN-aquifertoareawashes.PredictedbaseflowdischargesalongMoenkopiwashandLagunaCreekarediscussed.Byusingvariouspumpingscenariosinmultiplemodelsimulations,theUSGSwasabletoattributeapproximatebaseflowdischargereductionstoindustrialand/ormunicipalwithdrawals.TheCHIAconcludedthatmine-relatedwithdrawalswouldhaveaminorimpactonbaseflowdischargesinsomeinstancesbaseduponmodelresults,butnevertoexceedthematerialdamagecriterion.ResultsoftheSeptember2000AssessmentAswithCriterion3,OSMREbasedtheiranalysisofthiscriteriononthelatestUSGSNaquifermodel,whichhadlastbeenupdatedin1994.OSMREagainconcludedthatbasedupon“themostrecentN-aquifercomputermodelsimulation,materialdamagetothehydrologicbalanceoftheN-aquifer,causedbymining,withrespecttoN-aquiferdischargehasnotoccurred”orthatit“couldnotdeterminewhetherornotmaterialdamagetothehydrologicbalanceoftheN-Aquiferhasoccurred”duetoalackofmodelingresults.Historicaldatadoexistforflowinsomeareawashes;however,thedataarelimited.Forthebaselineyears(1980-1984),datawereonlycollectedfortheMoenkopiandLagunaCreekwashes.TheDinnebitowashhadamonitoringstationestablishedinJune1993.Priortoestablishingthe10percentreductioncriteria,theCHIAnotedthattheMoenkopigaugehadbeenratedashavingpooraccuracy;Assuch,themarginoferrorinmeasurementofmorethan15percentexceedsthecriterionrangeof10percent.TheUSGSmonitoringreportsuselow-flowdataforcomparingwashflows.Low-flowdataarebasedupondailystreamdischargesforthemonthsofNovemberthroughFebruaryofawateryear.Dischargedatacollectedduringthesemonthsareconsideredrepresentativeoflowflowbecausetheeffectofstreamlossduetoevapotranspiration(lossesduetoevaporationandtranspiration,orthetransferofwatertotheatmospherebyvegetation)andgainfromsnowmeltandrainfall(whichgenerallyoccursduringtemperatemonths)isminimized.TheDinnebitowashhadameandailydischarge(aslow-flow)ofapproximately0.50cubicfeetpersecond(ft3/s),basedupon1994-1997continuous-recorddata.TheDinnebitowashgaugingstationbecameoperationalinJune1993.In1998,thelow-flowdischargemeasurementsfortheDinnebitowashrangedfrom0.32ft3/sto0.44ft3/s,areductionofatleast12percent.Theaveragemeandailydischarge(aslow-flow)forthebaselineyearsonMoenkopiwashwasreportedtobeabout3.2ft3/s.From1992through1998,theaveragemeandailydischarge(aslow-flow)onMoenkopiwashwasreportedtobeabout2.4ft3/s.Therefore,therehadbeenadischargereductionofapproximately25percentintheMoenkopiwashaccordingtotheUSGSprogressreports.TheLagunaCreekmonitoringstationhadbeenmovedtoanewlocationsincereadingsweretakenforthebaselineyearsmakingevaluationofthatdatadifficult.CHIACriterion4UpdateAccordingtotheUSGSreport“Ground-Water,Surface-Water,andWaterChemistryData,BlackMesaArea,NortheasternArizona—2003-2004”(TruiniandPorter2005),continuousdischargedatahavebeencollectedatfourstreamfiowgaugingstationssincethemid-i970s.Theaverageannualdischargeatthefourgaugingstationsvaryconsiderablyduringtheperiodofrecordandnolong-termtrendsareapparent.Groundwaterdischargetothewashesisassumedtobeconstantthroughouttheyear,andthemedianwinterflowisassumedtorepresenttheconstantannualgroundwaterdischarge.Accordingtothereport,since1995themedianwinterflowsforMoenkopiWash,DinnebitoWash,andPolaccaWashhavegenerallydecreasedandthereisnoconsistenttrendinflowsforLagunaCreek.Forthefourcontinuouslymonitoredwashes,themedianwinterflowsin2003were3.45ft3/sforMoenkopiWash,0.75ft3/sforLagunaCreek,0.25ft3/sforDinnebitoWash,and0.10ft3/sforPolaccaWash.Bycomparison,theearliestmeasuredmedianwinterflowsforLagunaCreek(1997),DinnebitoWash(1994),NaturalResourcesDefenseCouncil28andPolaccaWash(1995)were1.8ft3ls,0.5ft3/s,and0.35ft3/s,respectively.Assuch,flowreductionsof50percentormoreareevidentsincemonitoringbeganinthosethreewashes:58percentreductionatLagunaCreek;50percentreductionatDinnebitoWash;and71percentreductionatPolaccaWash.ForMoenkopiWash,theperiodofrecordismuchlongerandshowsageneraldeclinesincethehighestmeasuredvaluein1988,exceptduringthelasttwoyearswhereflowhasincreased.Aswithspringdischarge,theCHIAcriteriadependsonsimulatedgroundwatermodelingresultsratherthanphysicalmonitoringdatatoassessimpactsofchangesinbaseflowtowashesandcreeks.Thephysicalmonitoringdatasuggestthatbaseflowinthemonitoredwasheshavedecreasedbymorethan10percentsincemonitoringbegan.Assuch,inaccordancewiththeCHIAcriteria,materialdamagetotheN-aquiferisevident;however,simulatedmodelingresultsdonotcalibratewiththephysicalmonitoringdata.SummaryOfthefourN-aquifergroundwaterresourcecriteriaidentifiedintheBlackMesaCHIA,onlyone(Criterion1)iswrittensuchthatmaterialdamagecanbereadilydeterminedthroughphysicalmonitoringdata.Theotherthreecriteriaarewrittensuchthatmaterialdamagecanonlybedeterminedifattributedtominerelatedgroundwaterwithdrawalsthroughhypotheticalmodelingefforts.Whilemunicipalwithdrawalshavegrownovertime,mine-relatedwithdrawalsstillrepresentthesinglelargestconsumptiveuseofgroundwateratBlackMesa,accountingforabout62percentofthetotalgroundwaterwithdrawalsandabout77percentofthegroundwaterwithdrawalsfromtheconfinedportionoftheN-aquifer(TruiniandPorter2005).Compoundingtheissue,mostmine-relatedwithdrawalsareusedtotransportcoalasslurrytoNevada.Assuch,extractedgroundwaterisexportedfromtheregion,precludinganypotentialforconservationmeasuresthatmightbeemployed,suchastreatmentandre-use,ifthewaterwereusedlocally.EvaluationofCriterion3isbasedsolelyoncomputergroundwatermodelingsimulationsandCriteria2and4aredirectlydependentuponthemodelingresults.Sincethemodelingsimulationsarenotperformedregularly,OSMRE.doesnotannuallyreviewthecriteriabaseduponthesimulationresults,makingitimpossibleforthemtoascertainwhethermaterialdamagehasoccurred.ConcludingmaterialdamageisthereforeproblematicbaseduponthefinalCHIAcriteriairrespectiveofdataevaluation.However,inlightofavailablemonitoringdata,itisnotpossibletosupportOSMRE’sconclusionthatmaterialdamagehasnotoccurred,madeinitsannualanalysesofPeabodyandUSGShydrologicaldatamonitoringreports.WithrespecttophysicalmonitoringdatafortheN-aquifer,anevaluationofthemorerecentlycollecteddatashowsthattheconcerningtrendspreviouslyobservedandreportedbyLFRinSeptember2000continuetopersist.ThemedianaverageannualdeclineingroundwaterelevationsintheconfinedportionoftheNAquiferwasreportedtobeapproximately2feetperyearsince1983.Themedianoveralldeclineinwaterlevelsintheconfinedportionoftheaquiferfrompre-stressperiod(1965)to2004is72feetwithamaximumdeclineofmorethan205feetatonelocation.Springmonitoringdatashowreductionsindischargeofbetween19percentand50percentinthreeofthefourmonitoredspringssincearound1990,andbymorethan70percentifhistorical(pre-development)dataareconsidered.Similarly,theUSGSconcludedthatmedianwinterflowsinwashes,usedtoapproximatebaseflowattributedtogroundwaterdischarge,havebeenobservedtobedecreasinginexcessoftheCHIAcriterionthresholdformaterialdamageinatleastthreeoffourwashesthathavebeenmonitoredsince1995.SinceamajorityofgroundwaterwithdrawalsfromtheN-aquiferareindustrialandassociatedwiththemine(particularlyintheconfinedportionoftheaquifer)theobservedimpactsmustbeattributedinlargeparttothosemine-relatedwithdrawalsand,therefore,physicalmonitoringdataconfirmsthatmaterialdamageisstilloccurringasaresultofPeabodywithdrawals.TechnicalReviewof“AThree-dimensionalFlowModeloftheD-andN-aquifers”and“AThree-dimensionalFlowModeloftheD-andNaquifersSupplement1”LFRprovidedareviewofthemodeldevelopedbyPWCCforthecombinedD-aquiferandN-aquiferanddeterminedthat:NaturalResourcesDefenseCouncil29The model, because
of its nature, resolution, and data density;

is not well suited
to the task of assessing potential material damage
or other disturbance

to the hydrologic balance

as it was intended

to do. • A surface boundary condition putting,

in effect, an infinite amount
of water on top of the aquifer system

is inappropriate

in an arid to semi-arid climate setting. • The model indudes both the D- and N-aquifers. The CHIA has been developed
for the N-aquifer oniy. By including groundwater storage of the D-aquifer

to the model, more than 43 percent
of stored water

is added
to the system. By adding storage

to a system where “most of the groundwater pumped

is released from storage,” the effects of withdrawals

are effectively diluted. Overall, the new model provided for recharge levels that greatly exceed the latest estimates provided
by the USGS.
In the PWCC model, approximately 11,000 acre-feet per year of recharge

is applied

in the unconfined portion
of the N-aquifer.

In addition,

an estimated 5,400 acre-feet per year of recharge

is derived from the river recharge boundary condition applied
to the upper surface of the model
as an initial condition (pre-pumping). The upper boundary condition represents

an infinite supply of water, thus aquifer withdrawals
will yield additional recharge from the river recharge boundary condition due to increased vertical gradients.

It is estimated that more than 15,000 acre-feet per year of recharge could be derived from the theorized river recharge boundary condition

if pumping stresses lowered groundwater elevations

to the top of the N-aquifer. The impact of the river recharge boundary condition was not assessed

in the sensitivity analysis. The PWCC model did not address the resolution problems that have precluded modeling

as an accurate method to assess material damages

in the form of reduced discharge from the N-aquifer. The PWCC model

is unable
to resolve changes
in spring discharge from the N-aquifer

or reduced flow in washes

at the 10 percent level specified by the CHIA criteria. Actual monitoring data regarding spring discharges continue

to contradict predictions based on modeling. In July 2005, Supplement

1 of the Three-Dimensional
Flow Model of the D- and N-aquifers was released. The purpose
of the supplement
was to simulate and evaluate five additional pumping scenarios, provide results of additional sensitivity testing, and evaluate whether the models originally presented

in 1999 are able to accurately simulate water level changes from 1997 through 2003 in the Black Mesa monitoring wells. Based on our review of the supplemental report, LFR concludes

as follows: • Previous concerns regarding the model and its ability
to resolve specific CHIA criteria requirements remain unresolved. • Calibration statistics typically provided

in model validation reports (e.g., American Society for Testing and Materials [ASTM] guidance for documenting
and calibrating groundwater flow model applications)

are not made available, but rather qualitative statements
are provided. For example, the supplement simply offers us this evaluation: “The four models match the observed water-level changes at the six BM monitoring wells quite well.” The report further states that the model was updated

to include additional pumping data and simulated model results were compared

to the updated pumping data. The report states, “This evaluation, which

is not presented here, indicated that there were only small differences between measured and simulated drawdown
for the period 1997 through 2000.” Subjective and unsupported narrative does not constitute technical support for the conclusion reached. It would be more appropriate

to provide quantitative analyses
of model validation that demonstrate model performance within applicable industry standards. • For the additional pumping scenarios, the report states that “predicted impact on discharge

to streams was almost negligible, and would not be measureable.”
The question that more appropriately should be addressed

is whether the model would be able to resolve changes

in spring discharge

at the level necessary

to evaluate the CHIA criteria. For example,

to assess discharge reductions

at Pasture Canyon Spring,

a 10 percent reduction

in spring discharge (CHIA Criterion

3) would require that the model accurately resolve changes

in spring discharge
of less than

5 gallons per minute
or
8 acre-feet per year at a minimum. Furthermore,

if the model were accurately calibrated,

it would show

a reduction

in spring flow of more than 19 percent

at Pasture Canyon Spring since 1995 (Truini, Macy; and Porter 2005). Natural Resources Defense Council

30• It is reported that neither the USGS nor PWCC monitors water levels in the confined portion
of the D-aquifer

as part of its monitoring effort. D-aquifer water level information would be needed

to directly evaluate the change

in leakage from the D-aquifer

to the N-aquifer under CHIA Criterion

2 (OSM 2005). D-aquifer water level data would also be necessary

to calibrate

a model that incorporates the D-aquifer and is intended,

in part, to quantif,r leakage from the D-aquifer

to the N-aquifer. Conclusions To determine whether Peabody’s extraction

of more than 4,000 acre-feet
of water per year from the N-Aquifer would cause material damage

to the aquifer, OSRME prepared

a CHIA report dated April 1989 (4,000 acrefeet is typically used for estimation

of mine-related groundwater withdrawals). Actual annual withdrawals have ranged from 2,520 acre-feet

to 4,740 acre-feet since mine-related withdrawals began in earnest
in the early

1 970s. The average mine-related withdrawal over that same period has been approximately 3,950 acrefeet. In the CHIA, OSMRE established specific criteria used to determine whether material damage would occur. Based upon groundwater modeling performed
for the CHIA, OSRME concluded that none of the projected impacts associated with proposed mine operations exceeded the material damage criteria; therefore, it anticipated

no material damage

to the hydrologic balance within the study area. In September 2000, LFR evaluated groundwater, surface water, and water quality data from the Black Mesa monitoring program contained

in USGS Progress Reports

to determine

if material damage

to the N aquifer could be detected

or appeared imminent. Flaws in the CHIA criteria and dependence

of some criteria on an underlying model that was not specifically designed

to evaluate those criteria made the evaluation difficult.

It was determined that while the model may reasonably predict regional N-aquifer groundwater conditions

in the Black Mesa vicinity; the model does not adequately represent geologic detail to enable conclusions regarding vertical leakage, spring discharge, and base flow in washes

at the scale required
by the final CHIA criteria. LFR concluded that, issues with the final CHIA aside, material damage was evident based upon CHIA Criterion

1. Additionally,

if monitoring data were given precedence over modeling predictions, it could be determined that excessive pumping

of the N aquifer has caused groundwater discharge reductions to springs and washes that exceed the guidelines established

in CHIA Criterion

3 and CHIA Criterion

4. The most recent physical monitoring data indicates that the 2000 LFR Report conclusions

are still valid. Since LFR’s September 2000 report, physical monitoring data show excessive drawdown

in many Black Mesa area groundwater monitoring wells and continued declines

in discharge

to springs and washes. Based on the latest physical monitoring data, LFR concludes that additional negative impacts resulting

in material damage have occurred and further material damage

to the N-aquifer

is imminent. Material damage

is still indicated under CHIA Criterion

1 and, if physical monitoring data
is given precedence over hypothetical modeling results, material damage

is also clearly indicated
for CHIA Criteria

3 and 4. With respect

to CHIA Criterion

2, leakage

is not adequately assessed but indirect evidence
of material damage associated with induced leakage exists. LFR continues

to believe that the Black Mesa CHIA criteria are not necessarily protective

of the N-aquifer water resources due to their dependence upon simulated computer modeling results and disregard
of actual monitoring data. Damage

to the hydrologic balance
of the N-aquifer may be compounding
over time due to the lack of protection provided based upon the CHIA criteria and the disregard
of actual monitoring data. Nevertheless, groundwater modeling results, rather than actual monitoring data, remain the primary tool for assessing material damage

to the N-aquifer.

As such,

a detailed and quantitative analysis
of model performance, based on standard industry practices for model calibration and documentation,

and considering
the rigorous requirements

of the CHIA criteria,

is needed.NaturalResourcesDefenseCouncil31SELECTED REFERENCES GeoTrans, Inc. 1999. A Three-Dimensional
Flow Model of the D and NAqufers, Black Mesa, Arizona. September. GeoTrans, Inc. 2005.
A Three-Dimensional
Flow Model of the D and NAqufrs, Block Mesa, Arizona, Supplement

1. July. LFR Levine•Fricke. 1997. Evaluation

of Impacts of Groundwater Pumping from the NAqufèr, Black Mesa Area, Arizona. August. LFR Levine•Fricke. 2000. Evaluation

of Cumulative Hydrologic Impacts
on N-Aqufr, Block Mesa, Arizona. September. LFR Levine•Fricke, 2002. Technical Review
of “A Three-Dimensional
Flow Model of the D and N Aquifers” Prepared
by HIS Geotrans and Waterstone

for the Peabody Western Coal Company, September 1999. April. The Office of Surface Mining Reclamation
and Enforcements. 2004. Report on its Review and Analysis
of Peabody Western Coal Company’s 2003 ‘nnual Hydrological Data Report” and the U.S. Geological Survey’s “Ground-Water, Surface-Water, And Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2002- 03.” September. The Office of Surface Mining Reclamation
and Enforcements. 2005. Report on its Review and Analysis
of Peabody Western Coal Company’s 2004 ‘Annual Hydrological Data Report” and the U.S. Geological Survey’s “Ground-Water, Surface-Water, And Water-Chemistry
Data, Black Mesa Area, Northeastern Arizona—2003- 04.” August. Thomas, B.E. 2002. “Ground-Water, Surface-Water,
and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona-2000-2001,

and Performance
and Sensitivity

of the 1988 USGS Numerical Model of the N Aquifer.” U.S. Geologic Survey Water Resources Investigations Report 02-4211. Truini, M. and S.A. Longsworth. 2003. “Hydrogeology

of the D Aquifer and Movement and Ages of Ground Water Determined from Geochemical
and Isotopic Analysis, Black Mesa Area, Northeastern Arizona.” Water Resources Investigations Report 03-4

1 89_Version
1.1. Truini, M. and T.J. Porter. 2005. “Ground-Water, Surface-Water,
and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona-2003-2004.”

U.S. Geologic Survey Open File Report 2005-1080.NaturalResourcesDefenseCouncil

J32Technical Review
of “A ThreeDimensional Flow Model of the D and
N Aquifers” Prepared

by HIS Geotrans and Waterstone,

for the Peabody Western Coal Company, September 1999 April 24, 2002 (LFR 014-10002-00) Introduction Three-dimensional

flow models of the N Aquifer

in the Black Mesa Basin of Arizona have been developed and used to evaluate effects from Peabody Western Coal Company (PWCC), and Navajo Nation and Hopi Tribe community pumping centers on the N Aquifer. Those modeling efforts have been applied
to assess potential impacts

to the N Aquifer. The Department

of Interior has previously established Cumulative Hydraulic Impact Assessment (CHIA) criteria
to assess the presence
of material damage

to the N Aquifer caused by PWCC pumping. The four main CHIA criteria included: 1. Maintain potentiometric head of 100 feet above the top of N Aquifer

at any point to preserve confined state of aquifer. 2. A value of leakage from the D Aquifer not to exceed 10% from mine related withdrawals. 3. A discharge

to springs reduction

of 10% or more caused by mine-related withdrawals based on results of N Aquifer simulation. 4. A decline
in discharge

to the N Aquifer washes by 10% or more caused by mining. Evaluation

of the four CHIA criteria relies heavily
or almost entirely on model simulation results.
In fact, the very terms of some of the criteria directly refer to a modeling analysis. Unfortunately, available models generally lack the necessary resolution and/or were not developed
for the specific purpose
of evaluating CHIA criteria. Thus there has been

a large degree of uncertainty

in conclusions derived from model predictions. In September 1999, PWCC issued

a report summarizing

the development

of a new three-dimensional flow model that simulated aquifer conditions and groundwater flow in both the D and N aquifers. One stated objective
of this modeling effort was to help assess probable hydrologic consequences

of the life- of-mine mining plan upon the quality and quantity
of surface and groundwater

for the proposed permit and adjacent areas. More specifically,
the model was used to estimate future impacts
of PWCC and tribal pumping
on the D and N aquifers.NaturalResourcesDefenseCouncil33LFR was asked to provide

a technical review of the model and accompanying documentation,

and its application

to predicting impacts
on the D and N aquifers. This review focused on whether the new model improved the ability
to assess material damage and other disturbances

to the hydrologic balance relative to CHIA criteria and whether

it accurately simulated responses

to PWCC pumping
on such things
as groundwater elevations, aquifer discharge, induced leakage, and storage loss in the D and N aquifers. Model Review The results of our review of the most recent model developed

by PWCC are summarized

in the following comments. Major technical issues and other inconsistencies

are discussed with reference

to the model documentation, where available. Overall, LFR’s comments can be condensed into the following three statements:

i. The model, because
of its nature, resolution, and data density,

is not well suited
to the task of assessing potential material damage
or other disturbance

to the hydrologic balance

as it was intended

to do. ii. A surface boundary condition putting

in effect an infinite amount
of water on top of the aquifer system

is inappropriate

in an arid to semi-arid climate setting. iii. The model includes both the D and N aquifers. The CHIA have been developed
for the N Aquifer only. By including groundwater storage of the D Aquifer

to the model, over 43% of stored water is added
to the system. By adding storage
to a system where “most of the groundwater pumped

is released from storage,” the effects of withdrawals

are effectively diluted. Major Issues A. Surface boundary condition The model consists
of seven layers, the top three representing various members
of the D Aquifer. Layer four represents
the thin Carmel Aquitard, and layers five through seven represent members
of the N Aquifer. Peabody states that water budgets provided

in the model documentation

are based on the combined inflows and outflows
of both the D Aquifer and N Aquifer.

In the Black Mesa Area, the Mancos shale and other unconsolidated deposits overlie the D Aquifer. Those units are not explicitly defined

in the model because they are thin and usually unsaturated (page 5-1). On page 5-12,

it is stated that “Water primarily moves into the Dakota aquifer from leakage of water through the Mancos shale overlying the Dakota sandstone.” This leakage

is simulated

in the model by a river boundary condition which,
in effect, places an infinite amount
of water on top of the model.

A “riverbed” conductance

of 0.00026 ft/d and

a thickness
of 600 feet is used for the Mancos shale, and

a “river stage”

is assumed

to be 100 feet above the top of the Mancos,

or 700 ft above the top of the D Aquifer
(p. 513). This vertical conductance, albeit small,

is theorized

to yield

a significant amount
of inflow when considered over the area of the aquifer system modeled. ‘When combined with data on the aerial extent of the D Aquifer (Surface statistics, Table 4.3-1) and evaporation (section 5.4.2, page 5-16), this simulated “river recharge” yields an estimated 5,400 acre-feet/year or more to the combined aquifer systems,

or nearly the equivalent

of the documented withdrawals (Peabody mine and Indian Communities

are estimated

to withdraw 4,000 and 2,800 ac-ft/yr, respectively). Note that this boundary condition influx

is an initial (pre-pumping) source of recharge

in addition

to the precipitation recharge
of 11,000 ac-ft/year

in the unconfined areas, discussed

in the recharge boundary condition, section 4.6.9, and used extensively

as a variable

in calibration runs (ES-3 and page 4-36). The river boundary condition

on top of the model domain

in itself contributes

an inflow of equal magnitude

as the groundwater withdrawals. With increasing drawdown

in the underlying aquifers, the surface boundary condition,

as theorized

in the model, will yield more water due to increased vertical gradients. As such, the impact of the surface boundary condition

is that sufficient water

is always available

as vertical leakage

to the D and N aquifers

to offset pumping stresses applied
in the simulations. Impacts

to spring discharge and baseflow

in washes are minimized,
the boundary between the confined and unconfined portion of the N-Aquifer

is unaffected, and the confined portion
of the N-Aquifer remains fully saturated. Yet, the Natural Resources Defense Council

34modelers conclude that “Because
of the limited flow through the Mancos and the further isolation from the N Aquifer provided
by the D Aquifer and Carmel Formation, more extensive characterization

was not believed to be worthwhile

for the objectives

of the model. Further, these parameters [river conductance
and river stage] were not adjusted during the calibration.” B. Horizontal and vertical resolution The horizontal cell dimensions

of the finite difference grid range from 500 to 4,200 meters (1,640
to 13,780 feet). This spatial resolution

is not adequate

to evaluate impacts

at individual washes and springs (CHIA

3 and 4). This
is because MODFLOW treats streams

(a line feature) and wells and springs (point features)

as three-dimensional

cells or cell blocks. For example, the lateral dimensions

of one drain cell at Moenkopi School

is 3,000 by 2,100 meters (9,840 by 6,890 feet) while in the actual scenario

is a spring area approximately

50 feet wide discharging anywhere between

12 to 40 gpm only. Such discrepancy

in representation

of a drain feature will effect the calibration that can either be aimed
at water levels or discharge, but not both. This
is an inherent and well-known problem
of MODFLOW
and finite different models
in general. The alternative would be the use of a finite element model. In the vertical dimension,
the report states that the contact elevations

of the seven hydrostratigraphic
units (HSUs)

is generally accurate within 100 feet in moderately sloping terrains and up to 300 feet in steeper areas (Appendix

F, page F-2 and F-6). This too, precludes

an accurate representation

of springs and intersects

of HSUs by streams which are critical
to the natural drainage
of the aquifer system. These shortcomings related to grid resolution have been recognized

by the authors on page 1-5: “The model grid, although optimized

to address flow issues [stream discharge, recharge, leakance], was not designed

to evaluate impacts

at individual springs
or wells.” Yet, the impact on springs

is acknowledged

to be
a significant issue of concern, and
is exactly the goal of CHIA criterion #3. C. Confined and unconfined storage The model combines the water budget (Table 5.8-4) for the D and N aquifers, thereby obscuring
the CHIA that have been developed
for the N Aquifer only. The combined volume of the two aquifers increases the predicted amount
of groundwater

in storage by 43% (Table 4.3-1). Because most of the groundwater pumped

is released from storage (page ES-6), the effects of withdrawals

on the N Aquifer are diluted. When unconfined storage

is depleted,
air enters the pore space to replace the extracted groundwater. When the groundwater

is confined, storage depletion results
in pressure drops that extend over very large distances
(in the order of miles)
to draw replacement water from the surrounding aquifer over long periods of time (decades). Under unconfined conditions
the amount
of storage

is determined

by the storage coefficient which equals the specific yield (Sy), or drainable porosity

at the water table. For confined conditions
the storage coefficient is expressed

as specific storativity (Ss) and is described

as the volume
of water released per unit volume
of aquifer per unit change
in head. Both these coefficients,
and the respective condition that the groundwater

in a HSU

is exposed
to, have

a significant effect on the amounts
of water recharged, stored and pumped. However, from the nine calibration steps, only one (step
6, page 5-36) adjusted the specific storage while the remaining steps controlled
the hydraulic conductivity
and flow rates, specifically recharge. This does not agree with the conclusion that the hydrologic system

is “only mildly” sensitive

to recharge (page 8-4). In the transient model run,

a large contrast exists between the values of Sy (0.1) and Ss (3.05.10-7 ft-I). These values are assumed constant throughout
the vertical layering and the lateral extent (page 5-39, and Table 5.6-1). This is puzzling, since over 50 pumping tests have been performed over the area and storage coefficient

is an output from such analyses. Furthermore,

a change from confined

to unconfined condition results
in the release of large amounts
of water, albeit irreversible. Once air enters

a previously confined aquifer,
its recovery will not be complete because
of air entrapment and possible settling. The scenario shown
in Figure 5.6-3 with the new 3-D model showing

a larger confined area than the 2-D model and virtually
no effect on the confinedl unconfined boundary
by the year 2033 cannot be justified with the storage data used. Natural Resources Defense Council

35Other inconsistencies: • Page 1-1: reads that the projected recovery
of the water levels, 20 years after pumping ceases,

is 94%. The same recovery appears
in the conclusions, page 8-4, to be 70%. • Page ES-3: “Model calibration was intended

to be used to improve basin-wide recharge”. Section 5.4 (page 5-12), on the other hand, reads: “The plan to estimate the recharge rate using the model was not successful because
of uncertainty

in the discharge rates”. Model calibration,

as defined by ASTM, should focus on the match between model simulation and observed data. • Page ES-4: The values of “full” and “half” recharge stated here differ more than by round-off errors from those listed in Table 5.8-4.
It is unclear which values were input and which were “calibrated

to improve estimates
of recharge”.

It does not appear that

a recharge rate representative

of Lopes and Hoffman’s work was used. • Page ES-4:
It is unclear why four models had to be calibrated

in order to estimate the effects of PWCC and community pumping
on the D and N aquifers.

If the difference between these four models

is only in recharge and discharge rates, one calibrated model and three “what-if” scenarios would seem more appropriate. • Page 5-33: The standard guide to model verification (ASTM, 1994),

is referenced but does not appear in Section

9, References and Bibliography.

It is also unclear from the mass balance, Table 5.8-4, how this verification relates
to stream discharges which,
in Tables 6.3-7 to 6.3-9, show no effect to pumping whatsoever. • Page 5-38: The units used in the model are meters and days, while the report

is written
in, and the figures of contours show, units of feet. Reason for this inconsistency

is undear andit makes comparisons

of calculations

to reported graphs difficult. • Figures 5.6-4 and 5.5-5: An anomalous geological feature with

a contrasting hydraulic conductivity connecting wells BM-

1, BM-2 and BM-3

is shown
in the three lowermost formations,
but its origin

is not explained. • Figure 6.1-1: First part of the curve, historical pumpage,

is different

in the presented scenarios.

If based on existing data, the six curves from 1960 to 1998 should be identical. • Figures 6.3-14, 6.3-21, 6.3-28, and 6.3-41. Problem

in the legend of the drawdown contour: the subtraction

is not that of scenario

A— E, shown
in Figure 6.3-7. Summary

of the Model’s Applicability

to N Aquifer Issues LFR has reviewed previous reports and modeling applications used to assess potential impacts

to the N Aquifer from mine-related groundwater withdrawals. The most significant issues previously identified
by LFR that are relevant

to the current model review include: • Most recharge

to the N Aquifer occurs
in the Shonto area north of the mesa where the N Aquifer

is unconfined. • The quantity
of recharge

to the N Aquifer has been overestimated

in previous modeling exercises. Many early models included

as much
as 13,000 ac-ft/yr of N-aquifer recharge. More recent studies conducted

by the U.S. Geological Service (USGS; Lopes and Hoffman, 1996) incorporating detailed geochemical
and isotope measurements suggest that the average rate of recharge

to the N Aquifer during the past several thousand years may be as low as 3,100 ac-ft/yr
in the primary recharge area along the northern margin of the mesa. • USGS studies by Brown and Eychaner (1988) estimate that only 3% of the N Aquifer water budget

is attributed

to leakage from the overlying

D Aquifer. • CHIA criteria were developed

by the Department

of Interior, Office of Surface Mining Reclamation and Enforcement

to establish

if material damage

to the N Aquifer has or may occur
as a result of mine-related withdrawals. Those criteria may not be protective because many depend either directly or indirectly
on simulations using ground water models that were not specifically designed

to evaluate those criteria.NaturalResourcesDefenseCouncl36• Monitoring data indicate that excessive pumping
of the N Aquifer has caused groundwater level declines and spring discharge reductions exceeding guidelines established

in the CHIA. The latest model developed

by PWCC does little, if anything,

to resolve the previously identified issues associated with the N Aquifer, and incorporates
the D Aquifer, which

is generally
of poor quality and not

a drinking water source. Overall, the new model provides for recharge levels that greatly exceed the latest estimates provided
by the USGS.
In the PWCC model, approximately 11,000 acft/yr of recharge

is applied
in the unconfined portion of the N-aquifer.

In addition,

an estimated 5,400 ac-ft/yr of recharge

is derived from the river recharge boundary condition applied

to the upper surface of the model

as an initial condition (pre-pumping).
The upper boundary condition represents

an infinite supply of water, thus aquifer withdrawals
will yield additional recharge from the river recharge boundary condition due to increased vertical gradients.

It is estimated that more than 15,000 ac-ft/yr of recharge could be derived from the theorized river recharge boundary condition if pumping stresses lowered groundwater elevations

to the top of the N Aquifer. The impact of the river recharge boundary condition was not assessed

in the sensitivity analysis. The PWCC model does not address the resolution problems that have precluded modeling

as an accurate method

to assess material damages

in the form of reduced discharge from the N Aquifer. The PWCC model

is unable
to resolve changes

in spring discharge from the N Aquifer
or reduced flow in washes

at the 10% level specified
by the CHJA criteria. Actual monitoring data regarding spring discharges continue

to contradict predictions based on modeling. It does not appear that changes incorporated

in the PWCC model improve the ability
to assess the CHIA criteria
or to assess any similar criteria that may be developed. The N Aquifer was the primary subject of the CHIA because, among other things,

it represents

a sole-source drinking water supply for the Hopi Tribe and many members
of the Navajo Nation. Water quality

in the D Aquifer

is generally too poor for human consumption. Applicability

of the Model to Other Groundwater Issues PWCC used their model
to assess

a broader range of impacts

as defined by their report on Probable Hydrologic Consequences, Chapter

18 of Peabody’s Revised Mining Application. Previous reports
in defense of PWCC groundwater withdrawals include community withdrawals when discussing potential damages

to the N Aquifer. However, the community wells are not used for calibration

in the PWCC model due to “a lack of detailed information

on pumping

in community wells”. Considerable information
has been collected
by the USGS on annual pumping and/or water use, and on water levels in wells used by the various communities and it is not apparent why simulation results were not calibrated

to available community pumping center data. The reports provided
by PWCC suggest that past (45÷ years)
as well as future groundwater extraction
(an additional 20+ years)
at the mine will only capture water from aquifer storage (rather than recharge). Water is captured from aquifer storage under transient conditions when wells are initially pumped. Equilibrium conditions
are reached when the cone of influence extends

to (and captures) some source of recharge. This will result in reduced discharge from the aquifer (as springs
or baseflow

in washes) and/or
an inducement

of additional recharge

as leakage from overlying units to offset the withdrawals.

If withdrawals exceed available recharge, then transient conditions persist and groundwater again

is removed from aquifer storage. Under that scenario, groundwater elevations will continue

to decline and dewatering

of the aquifer can occur. PWCC suggests that the process of reaching equilibrium with groundwater withdrawals never occurs over the 65+ years of continuous pumping from the aquifer. In contrast

to previous studies that suggest only 3% of the N Aquifer water budget

is attributed

to leakage from the overlying

D Aquifer, the inclusion
of the D Aquifer and use of a river recharge boundary

in the model provides far greater aquifer storage and recharge

to offset mine-related withdrawals.

It is not surprising that impacts

to N Aquifer discharges
are minimized

in the model.NaturalResourcesDefenseCouncil37Conclusions Based on our review of the PWCC model documentation

the following conclusions

are provided: • The new PWCC model attempts

to characterize

a broader range of impacts
of groundwater withdrawals

by incorporating

the D Aquifer

in addition

to the N Aquifer. However, the PWCC model does not resolve problems identified with previous models used to evaluate potential impacts

to the N Aquifer. • Previously established CHIA criteria focus on impacts

to the N Aquifer primarily because

it is a solesource drinking water supply and spiritual resource for the Hopi Tribe. The D Aquifer

is generally not suitable for human consumption. • Incorporation

of the D Aquifer and river recharge boundary condition, along with N Aquifer recharge in the unconfined areas, results
in recharge assumptions that are substantially higher than any other known estimate and are inconsistent with recharge evaluations

in both unconfined and confined portions
of the N Aquifer provided
by the USGS and others. • The inclusion
of the D Aquifer and use of a river recharge boundary

in the PWCC model inappropriately provides
far greater aquifer storage and recharge

to offset mine-related withdrawals.

As such, conclusions regarding impacts

to N Aquifer cannot be substantiated. • The model, because
of its nature, resolution, and data density;

is not well suited
to the task of assessing potential material damage
or other disturbance

to the hydrologic balance

as it was intended

to do. ABOUT THE AUTHORS LFR Levine Fricke (LFR)

is an environmental consulting and engineering firm headquartered

in the San Francisco Bay Area with approximately
400 employees

in 20 offices nationwide. LFR provides assessment, visualization,
and practical solutions

to engineering and environmental problems associated with resource management, infrastructure development
and improvement,
and hazardous waste management. Dr. Vit Kuhnel, Ph.D., has over 15 years of experience

in environmental engineering
and water resource management

on projects throughout
the United States, Europe, and the Middle East. His expertise

in hydrogeology
and geochemistry includes groundwater exploration and modeling, contaminant
fate and transport modeling, remedial systems analysis, and design and implementation

of corrective actions. Dr. Kuhnel’s primary focus

is on the acquisition, interpretation, trend analysis, and presentation

of hydrologic data using groundwater flow and transport models ranging from simple analytical codes to sophisticated, three-dimensional, multi-phase
and transient models. Dr. Kuhnel works within LFR’s Water Resources and Quantitative Services Group which provides state-of-the-art modeling and three-dimensional visualization

of surface, unsaturated sub-surface,
and groundwater flow and transport phenomenon. Bradley Cross, R.G.,

is a Principal Hydrogeologist

and the Manager
of Operations
for the Southwest Region

at LFR. Mr. Cross has 15 years of experience

in groundwater resource evaluation and resource damage assessment, hazardous waste investigation,

soil and groundwater characterization

and remediation, environmental assessment, and regulatory compliance.
Mr. Cross

is experienced

in local to basin-wide characterization

of groundwater flow systems, field investigative methods, data analysis, remediation, litigation support, project management,
and report preparation. Specific areas of expertise include hydrogeology, stratigraphy, sedimentology;

and geochemistry including organic and inorganic transport and fate analysis.NaturalResourcesDefenseCouncil38ENDNOTES The 0111cr of Surface Mining Recla mation and Enforcement, Managing Hydrologic Jnfrrmurion.

A Resource for Development

of the Probable Hydrologic Consequences (PHC) and Cumul.arive Hydrologic Impact Assessments (CHIA), Jan. 31, 1997,
p. 40. Data taken from USGS annual reports published between 1998-2004, reflecting the latest available monitor ing data; Peabody’s Annual 1-lydrological Data Reports from 2000-2004, reflecting Peabody’s monitoring data during the calendar year and including summary data from previous years; and OSMRE’s annual reviews of both USGS and Peabody’s annual reports, which determine

if available Peabody and USGS data indicate material dam age has occurred

as a result of Peabody’s N-aquifer water use. ‘The following discussion

of material damage criteria

is largely based on LFR Levine-Fricke-Revon, “Evaluation

of Cumulative Hydrologic Impacts
on the N-Aquifer, Black Mesa Area, Arizona,” September 2000 (prepared
for NRI)C and appended

to the Drawdown report); and LFR Levine-Fricke, “Report: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdraw als from the N-Aquifer, Black Mesa, Arizona,” March 2006 (prepared
for NRDC and appended

to this report). Office of Surface Mining “Reclama tion and Enforcement, Cumulative Hydrologic Impact Assessment

of the Peabody Coal Company Black Mesa/ Kayenta Mine,” Jan. 1988,
p. 5-11. See the U.S. Geological Survey’s “Ground-water, Surface-water,
and Water-chemistry Data, Black Mesa Area, Northeastern Arizona—2003- 04,” Sept. 2004; and the Office of Surface Mining Reclamation
and Enforcement, Report on Its Review and Analysis
of Peabody Western Coal Company’s 2004 “Annual Hydrological Data Report” and The U.S. Geological Survey’s “Ground-water, Surface-water, and Water-chemistry Data, Black Mesa Area, Northeastern Arizona—2003- 04,” Aug. 2005. Office of Surface Mining Reclama tion and Enforcement, “Cumulative Hydrologic Impact Assessment

of the Peabody Coal Company Black Mesa? Kayenra Mine,” Jan. 1988,
p. 5-i I. ‘The Office of Surface Mining Reclamation
and Enforcement, Report on Its Review and Analysis
of Peabody Western Coal Company’s 2004 “Annual Hydrological Data Report” and the U.S. Geological Survey’s “Ground-Water, Surface-water,
and Water-chemistry Data, Black Mesa Area, Northeastern Arizona—2003- 04,” August 2005, p. 7 . For accounts
of these events, see the following sections
of OSMRE’s progress reports: Report on Its Review and Analysis (2000), pp. 7—9; Report on Its Review and Analysis
of Peabody Western Coal Company’s “1996 Annual Hydrological Report—Black Mesa and Kayenta Mines” and the U.S. Geological Survey’s “Ground-Water, Surface-Water,
and Water-Chemistry Data. Black Mesa Area, Northeastern Arizona—I 996,” “Ground-Water, Surface-Water,
and Water-Chemistry Data, Black Mesa Area. Northeastern Arizona—1995,” “Results
of Ground water, Surface-Water,
and Water” Chemistry Monitoring, Black Mesa Area, Northeastern Ariwna—1994,” “Results
of Ground-Water, SurfaceWater, and Water-Quality Monitor ing, Black Mesa Area. Northeastern Arizona—1992—93”
(June 1998), pp. 7—9; Report on Its Review of Analysis of Peabody Western Coal Company’s 1992 “Hydrological Data Report” and the U.S. Geological Survey’s “Results of Ground-Water, Surface-Water
and Water-Quality Monitoring, Black Mesa Area. Northeastern Arizona—1991— 92” (March 1994), pp. 6—8; Report on Its Review and Analysis
of Peabody Coal Company’s 1991 “Hydrological Data Report” and the U.S. Geological Survey’s “Results
of Ground-Water, Surface-Water,
and Water-Qual ity Monitoring, Black Mesa Area, Northeastern Arizona—I 990—91” (June 1993), pp. 6—8; Review and Analysis
of Peabody Coal Company’s 1990 “Hydrological Data Report” and the U.S. Geological Survey’s “Results of Ground-Water, Surface-Water,
and Water-Quality Monitoring, Black Mesa Area, Northeastern Arizona—I989- 90” (December 1992), pp. 5—6. ‘The U.S. Geological Survey’s “Ground Water, Surface-Water,
and Water-Chem isuy Data, Black Mesa Area, North eastern Arizona—2003-04,” September 2004
p. 35-36 (Table 15).15 LFR Levine-Fricke, “Report: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,” 2006,

p. 10. See the Office of Surface Mining Reclamation
and Enforcement, Report on its Review and Analysis
of Peabody Western Coal Company’s 2004 “Annual Hydrological Data Report” and the U.S. Geological Survey’s “Ground-Water, Surface-Water,
and Water-Chemistry
Data. Black Mesa Area, Northeastern Arizona—2003- 04,” Aug. 2005,
p. 7-8.° LFR Levine-Fricke, “Report: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer. Black Mesa, Arizona,” 2006.
p. 10-11. “LFR Levine-Fricke, “Reporc: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,” 2006,
p. Ii.t4 LFR Levine-Fricke, “Report: Update of the CHIA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,” 2006 p. 11 .IS LFR Levine-Fricke. “Report: Update of the Cl-hA Criteria Evaluation
for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,” 2006,
p. 11. u Memorandum from Masud Ui Za man, Director
of Water Management Department,

to Mike Nelson, Staff Assistant
of Office of the Chairman! Vice-Chairman, Evaluation and Analy sis of Peabody Coal’s Groundwater Withdrawals
and Recommendations Pertinent

to Full Exercise
of the Navajo Water Code (Ocr.
4, 1984).7 Memorandum from Masud Uz Za man, Director
of Water Management Department,

to Mike Nelson, Staff Assistant
of Office of the Chairman! Vice-Chairman, Evaluation and Analy sis of Peabody Coal’s Groundwater Withdrawals
and Recommendations Pertinent

to Full Exercise
of the Navajo Water Code (Oct. 4, 1984).lB Memorandum from Masud Uz Za man, Director
of Water Management Department,

to Mike Nelson, Staff Assistant
of Office of the Chairman? Vice-Chairman, Evaluation and Analy sis of Peabody Coal’s Groundwater Withdrawals
and Recommendations Pertinent

to Full Exercise
of the Navajo Water Code (Oct. 4, 1984). “Office
of Surface Mining Reclama tion and Enforcement, Cumulative Hydrologic Impact Statement,
pp. 5-6, 5-lI. ‘°Al monitored springs

at Den nehotso and Hard Rocks are reported to have increased

in flow, data in both cases are questionable.
The baseline discharge
of Hard Rocks Spring has
only been estimated; discharge

at Dennehotso

has increased

so dramati cally that some extrinsic cause such as nearby construction

is implied. For fisher treatment

of these issues, see “Evaluation

of Cumulative Hydrologic Impacts
on the N-aquifer,” appended to this report.° The Office of Surfacr Mining Reclamation
and Enforcements, 2005, Report on its Review And Analysis of Peabody Western Coal Company’s 2004 “Annual Hydrological Data Report” and the U.S. Geological Survey’s “Ground-Water, Surface.Warer,
And Water-Chemistry Data. Black Mesa Area, Northeastern Arizona-—-2003- 04” (August),

p. 9. See LFR Levine-Fricke, “Report: Up date of the CHIA Criteria Evaluation for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,”
pp. 11-13. The Office of Surface Mining Reclamation
and Enforcements, 2005 Report On Its Review And Analysis of Peabody Western Coal Company’s 2004 “Annual Hydrological Data Re port” and the U.S. Geological Survey’s “Ground-Water, Surface-Water,
And Water-Chemistry
Data, Black Mess Area, Northeastern Arizona—2003- 04,” August, Appendix

G. t4 See LFR Levine-Fricke, “Report: Up date of the CHIA Criteria Evaluation for Peabody Western Coal Company Groundwater Withdrawals from the N-Aquifer, Black Mesa, Arizona,”
pp. 11-13. See the discussion

of Black Mesa hydrogeology

in “Evaluation

of Cumulative Hydrologic Impacts
on the N-Aquifer,” appended

to this report (citing Survey records); Foster Associates, Inc., Study ofAlternari

vet to Transport CoaL
p. E-9 (reporting 1993 study).Th See CHIA Criteria Section 6.2.2.4. t7 Truini,
M. andT.J. Porter, 2005, “Ground-Water, Surface-Water,

and Water-Chemistry
Data, Black Mesa Area, Northeastern Arizona—2003- 2004.” ‘ 5 Truini,
M. andT.J. Porter, 2005, “Ground-Water, Surface-Water,

and Water-Chemistry
Data, Black Mesa Area, Northeastern Arizona——2003- 2004”: U.S. Geologic Survey Open File Report 2005-1080.° The Office of Surface Mining Reclamation
and Enforcement, Report on its Review and Analysis
of Peabody Western Coal Company’s 2003 “Annual Natural Resources Defense Council

39HydrologicalDataReport”andtheU.S.GeologicalSurveys“Ground-Water,Surface-water,andWater-chemistryData,BlackMesaArea,NortheasternArizona—2002-03,”Sept.2004;and“Ground-Water,Surface-Water,andWater-ChemistryData,BlackMesaArea,NortheasternArizona—2003-2004”(TruiniandPorter2005).Again,seeourearlierdiscussionofOSMRE’smaterialdamagecriteriain“SignsofDecline,”whichappearsinChapter1oftheDrawdownreport,andLFRLevine-Fricke“Report:UpdateoftlseCHIACriteriaEvaluationforPeabodyWesternCoalCompanyGroundwaterWithdrawalsfromtheN-Aquifer,BlackMesa,Arizona.”CompareOfficeofSurfaceMiningReclamationandEnforcementWesternRegionalCoordinatingCenter,ReportonitsReviewandAnalysis(2000),pp.9—10withTable3intheDrawdownreport;theOfficeofSurfaceMiningReclamationandEnforcements,2005,ReportonitsReviewandAnalysisofPeabodyWesternCoalCompany’s2004“AnnualHydrologicalDataReport”;andtheU.S.GeologicalSurvey’s“Ground-Water,Surface-Water,andWater-ChemistryData,BlackMesaArea,NortheasternArizona—2003-04”(2005),p.9.OfficeofSurfaceMiningReclamationandEnforcement,CumulativeHydrologicImpactAssessmentp.3-36(citingtheUSGSmodelaspresentedinJ.H.Eyclianer,“SimulationofFiveGround-WaterWithdrawalProjectionsfortheBlackMesaArea,NavajoandHopiIndianReservations,Arizona,”1983(USGSWaterResourcesInvestigationsReport83-4000)).TheFinalEnvironmentalImpactStatementpreparedforPeabody’slife-of-theminepermitsetsanevenestimateofrecharge:between13,000and16,000acre-factperyear.SeetheOfficeofSurfaceMiningReclamationandEnforcement,ProposedPermitApplicationFEIS,vol.1,p.111-4.uSeeletterfromWilliamD.NicholstoChiefofsheOfficeofGroundwater(Oct.28,1993),pp.3—4.NicholsnotesthatBrownandEychaner,whoconductedtheinitialstudiesoftheNaquifer,reliedonestimatesofprecipitationlevelsof18inchesintheShontoareaandlessthan12inchesinmostoutcropareas.Theythenestimatedrechargetobe3percentofthe18inchesnearShonto,and1percentofthe12incheselsewhere.AsNicholspointsout,however,amapmeanannualprecipitationfar1931—1960publishedbytheStateofArizonashowsthatthemaximummeanannualprecipitationrateintheShontoareaisonly12—14inches,andamoreappropriateaveragefortheoutcropareaswouldbe10inches.NicholsalsoobservedthattheoriginalmodeldidnorjustiIrthepercentageofprecipitationitallocatedtorecharge.Ibid.,p.4.FollowingscritiquebyWilliam0.Nichols,oftheUSGSWaterResourcesDepartment,researchersThomas

J.LopcsandJohnP.Hoffmanrecalibratedtherechargeratefortheall-importantShontoregion.SeeletterfromWilliamD.NicholstoChiefoftheOfficeofGroundwater(Oct.28,1993),pp.2—4;LopesandHoffman,“GeochemicalAnalyses,”p.30.SeeLopesandHoffman,“GeochemicalAnalyses.”p.7;LevineFricke-Recon.“EvaluationofImpactsofGroundwaterPumping,”p.7.3C.V.‘Iheis,“TheSourceofWaterDerivedfromWells:EssentialFactorsControllingtheResponseofanAquifertoDevelopment,’CivilEngineering,10(1940),p.277.LetterfromWilliam0.NicholstoChiefoftheOfficeofGroundwater(Oct.28,1993),p.3.LetterfromWilliamD.NicholstoChiefoftheOfficeofGroundwater(Oct.28,1993),P.4.‘2002MiningApplication,Chapter18p.39(“themodelsarenotofsufficientresolutiontosimulateflowatindividualsprings...“CumulativeHydrogeologicImpactAssessmentofPeabodyCoalCompanyBlackMesaMine/KayentaMine,”1989.41Drawdownp.24.“SeeKuhnelandCross,“ATechnicalReviewof’AThree-DimensionalFlowModelofthe0andNAquifers’”preparedbyHISGeotransandWaterstone,forthePeabodyWesternCoalCompany,Sept.1999(LFR2002).2002MiningApplication,Chapter18.p.46.“2002MiningApplication,Chapter18,p.46.“2002MiningApplication,Chapter18,p,39(“themodelsarenotofsufficientresolutiontosimulateflowatindividualsprings...“).46Truinj,M.andT.JPorter,2005,“Ground-Water,Surface-Water,andWater-ChemistryData,BlackMesaArea,NortheasternArizona—2003-2004,”U.S.GeologicSurveyOpenFileReport2005-1080.“Forcalibrationstatisticstypicallyprovidedinmodelcalibrationreports,see,e.g.,ASTMguidancefardocumentingandcalibratinggroundwaterflowmodelapplications.“EnvironmentalIntegrityProject,“DirtyKilowatts:America’smostPollutingPowerPlants,”May2005.“U.S.GeologicalSurvey’s“GroundWater,Surface-Water,andWaterChemistryData,BlackMesaArea.NortheasternArizona—2003-04,”Sept.2004,p.3.GrandCanyonTrust,Inc.ccal.v.SouthernCaliforniaEdisonCo.etal.,UnitedStatesDistrictCourt,DistrictofNevadaJudicialDistrict,CaseNo.CV-S-98-00305-LDG(RJJ).MiguelBustillo,EdisontoShutDownPollutingCoalPlant,LosAngelesTimes.Dec.30,2005.GrandCanyonTrust,Inc.etal.v,SouthernCaliforniaEdisonCo.etal.,UnitedStatesDistrictCourt,DistrictofNevadaJudicialDistrict,CaseNo.CV-S-98-00305-LDG(RJJ).GrandCanyonTrust,Inc.etalv.SouthernCaliforniaEdisonCo.etal..UnitedStatesDistrictCourt,DistrictofNevadaJudicialDistrict,CaseNo.CV-S-98-00305-LDG(RJJ).‘DanielKraker,TheEndofanEraontheColoradoPlateau,HighCountryNews.Vol.38,No,1,Jan.23,2006.SSBlackMesaMinePermanentProgramPermitandKayentaMinePermanentProgramPermitAZ-000ID(Feb.12,2004)(submittedtoMr.JerryGavette,OSMRE)PeabodyFebruary12,2004letterp.3.uNRDCcommentlettertoOSMREonApril26,2002,citingUSGSregionalmonitoringreportsandrelyingondatapublishedtherein.ThereissimplynotenoughevidenceintherecordtosupportPeabody’sassumptionthatanalternativewatersourceisavailable.Infact,whatevidencedoesexistpointstothesignificantpotentialforC-aquiferwithdrawalstoupsetthelocalhydrologicalbalance.OSMREhaspreviouslyfoundtheC-aquifernottobeaviableoption.SeeDrawdownChapter1,footnote11.ThisfindingisfurthersupportedbythedependenceoftheburgeoningpopulationsoftheCoconinoPlateauontheC-aquifer—fromFlagstafftoTusayan—whichincreasinglyrelyontheC-aquifertofulfilltheirwaterneeds.Peabodyacknowledgesthat“[tjheexistingNavajoaquiferwelifieldwouldcontinuetobeuseduntilthenewsourcebecomesavailable.”Peabodyfurtherclaimsthat“[sifterthenewsourceisavailable,theNavajoaquiferweUfieldwouldcontinuetobemaintainedinafullyoperationalstatusforemergencyuseif,foranyreason,thenewsourcebecomesunavailable.”AsidefromfailingtoshowthatC-aquiferwaterwouldbeavailable,Peabodydoesnotdefine“emergencyuse.”SeePeabodyFeb.12,2004letter,p.4.BlackMesaandKayentaLife-ofMinePlanExtension(hereinafter“2004PlanExtension”),p.5.SIPhasesIandIIofthegovernment’sstudyappearunderthetides:FosterAssociates,Inc.,ErrolMontgomery&Associates,andRyley,Carlock&Applewhite,“PhaseIFinalReport:StudyofAlternativestoTransportCoalfromtheBlackMesaMinetotheMohavePowerGeneratingStation,”Dec.22,1992(literaturereviewproducedbyconsultantstotheInteriorDepartment):“PhaseIIFinalReport:StudyofAlternativestoTransportCoalfromtheBlackMesaMinetotheMohavePowerGeneratingStation,”Nov.17,1993(firsthalfofalternativesanalysisproducedbyconsultantstotheInteriorDepartment);andEnvironmentalProtectionAgencyRegionIX,“EPAComments:DEISonProposedPermitApplication,BlackMesa-KayentaMine,NavajoandHopiIndianReservations,Arizona,”Sept.1989,pp.2—3(attachedtoletterfromDeannaM.Wiesnan,DirectorofExternalAlfairsforEPARegionIX,toPeterA.Rutledge,ChiefofOSMRE’sFederalProgramsDivision,Sept.14,1989).SeealsoBureauofIndianAffurs,MemorandumfromBIAActingDeputytotheAssistantSecretaryofIndianAffairssotheOfficeofSurfaceMiningReclamationandEnforcement’sWesternFieldOperations,Sept.18,1989,p.1(onthe“DraftEnvironmentalImpactStatement(DEIS)fortheProposedPermitApplication,BlackMesa-KayenraMine,NavajoandHopiReservations,Arizona”).u42U.S.C.4321etseq.“Drawdownp.31.“SeeUnitedStatesCode42(1998):S1424.NaturalResourcesDefenseCouncil40