Attachment 1: 

Tolk/Plant X Well Field Map 
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9

8

5 6 7

7374

X8

X9

X2 X1 X3

78

76

75

36

34 35 32 33 31

30

29

28 27

26 25

24

1

16 17 15

13 14

12

11

10

51

49 50

48

77

X14

X17

X10 X15

X13

X16

Source: Esri, DigitalGlobe, GeoEye, i-cubed, EarthsUser Community, Esri, HERE, DeLorme, TomTom, M
Attachment 2: 

Tolk/Plant X Annual Well Production Table 
Year well count

wells

w/data

% wells

tested

Peak flow

rate (gpm) new wells

new well

peak flow

rate (gpm)

% of prod

from new

wells

prod

change

(gpm)

prod

change of

ext wells

(adj to

rem new

wells)(gp

m)

Annual

Water

Productio

n (AF) Notes

1992 46 31 67% 0 0 0% 0 Data do not include X wells

1995 46 25 54% 0 0 0% ‐4,672 0 Data do not include X wells2004 54 48 89% 15,800 8 2,730 17% 0 18,026 X wells included

2005 54 47 87% 15,282 0 0 0% ‐518 ‐518 17,162 X wells included

2006 54 15,2092007 55 40 73% 11,551 1 445 4% ‐3,731 ‐4,176 14,529 X wells included

2008 60 43 72% 12,588 5 2,643 21% 1,037 ‐1,606 14,496 X wells included

2009 61 42 69% 12,889 1 550 4% 301 ‐249 12,798 X wells included

2010 61 49 80% 13,858 0 0 0% 969 969 14,063 X wells included

2011 65 49 75% 12,903 4 881 7% ‐955 ‐1,836 13,399 X wells included

2012 69 52 75% 13,040 4 478 4% 137 ‐341 14,813 X wells included

2013 73 59 81% 12,858 4 1,582 12% ‐182 ‐1,764 15,710 X wells included

2014 73 47 64% 11,281 0 0 0% ‐1,577 ‐1,577 9,486 X wells included

0

2,0004,0006,0008,000

10,00012,00014,00016,00018,000

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Peak flow rate (g,pm)

Wellfield productivity vs. number of wells well count

Peak flow rate (gpm)
Attachment 3: 

LBG-Guyton Associates Tolk	Station/Plant	X	Water	Rights	Area	Saturated	Thickness	and	

Static	Volume	
LBG-GUYTON ASSOCIATES

PROFESSIONAL GROUNDWATER AND

ENVIRONMENTAL ENGINEERING

1101 CAPITAL OF TEXAS HIGHWAY

SUITE B-220

AUSTIN, TX 78746

512-327-9640

FAX: 512-327-5573

June 17, 2015

Ms. Amy Willhite

Water Resources Analyst

Xcel Energy

10800 Larimer Street, Suite 1300

Denver, CO 80202-1414

Re: Tolk Station/Plant X water rights area saturated thickness and static volume

Dear Ms. Willhite,

We have completed the calculation of saturated thickness and static volume for the

groundwater contained within the Ogalalla Aquifer beneath the Xcel water rights area in

Lamb County, Texas. 

These data were based primarily on measurements collected on April 14-15, 2015, which

are presented in the enclosed table with comparisons to measurements performed in May

2014. The measurements were collected during a shutdown period for Tolk Station, and

should represent static aquifer levels at each location. Some 

Additional data provided by the High Plains Underground Water Conservation District

from 2015 were used to supplement the sparse measurements in the western portion of

the water rights area.

The measurements were used to prepare estimated saturated thickness contours, which

are provided in the enclosed map. As you are aware, the area of highest saturated

thickness is in the eastern portion of the water rights area, with a saturated thickness over

100 feet in the areas immediately adjacent to and east of Hwy 385. This thickness

gradually decreases to 40 feet west of Plant X.

Static volume contained within the water rights was estimated based on this saturated

thickness. We used the same assumptions as in our previous static volume calculations for
Ms. Amy Willhite

June 17, 2015

Page 2

the Xcel properties in Lamb County: a recoverable volume boundary of 40 feet above the

base of the aquifer, and a specific yield of 15%. 

The estimated static volume in storage for the entire property (in terms of acre-feet) is

presented in the table below: 

Section Area

(ac)

Recoverable

Volume

(>40ft @ 15%

Yld) (ac-ft)

Volume Change

From May 2014

Estimate (ac-ft)

Area for potential 

future development 8,011 39,000 +21,000

Area of currently 

un-economic 

groundwater

4,413 4,000 +2,000

Area for potential 

future exploration 5,777 14,000 -17,000

Current Use Water 

Rights Area 25,359 82,000 -17,000

Total Xcel Water

Rights Area 43,560 139,000 -11,000

This represents the estimated static volume directly beneath the Xcel properties, and may 

be considered the lower bound of how much water can be economically recovered from 

those properties with vertical water wells. 

The volume contained within the shaded areas on the enclosed map represents 

groundwater that will not quickly flow to existing wells in the current-use water rights 

area. The blue shaded area has the advantage of being close to the plant, although there 

are no existing wells in this area. The yellow area may potentially be developed, although

an exploration program would be required to verify the production potential of this area. 

The orange area represents an area with saturated thickness that is too low to be 

economic with vertical wells, and would likely only be available for production with 

alternative well completions.

The change in estimated recoverable volume from 2014 for the current-use water rights 

area is a decrease of 17,000 acre-feet. All of the water level measurements were collected

in this area, therefore this estimate is supported by the most data.

The estimated recoverable volumes for the potential future development and potential 

future exploration area changed signifcantly from last year's estimate. These estimates are

dependent on sparse data from wells surrounding the Xcel properties. Small increases and

decreases in water level measurements in these wells affect a large area, and have a 

similarly large impact on volume estimates. This effect is magnified in percentage terms 
Ms. Amy Willhite

June 17, 2015

Page 3

because only volumes above 40 feet of saturated thickness are included in the recoverable

volume estimate.

If you have any questions about this information, please call me at 512-327-9640. 

Sincerely,

LBG-GUYTON ASSOCIATES

Tyler A. Davidson, P.E.

Associate

Enclosure

cc: Mr. Richard Belt, Xcel Energy
Tolk Station/Plant X May 2015 Static Level Measurements

Well ID

5 230.4 (4.4)

7 236.3 (8.9)

10 223.7 2.6 

11 217.1 (1.7)

14 214.5 (2.3)

17 205.9 (3.2)

18 229.8 (5.4)

23 219.9 not measured in 2014

25 186.8 (3.6)

28 201.0 5.5 

37 198.6 (4.4)

40 198.1 (6.0)

43 206.8 not measured in 2014

44 207.5 0.6 

45 209.8 0.4 

47 215.4 (2.0)

53 204.3 (2.0)

54 195.0 (5.8)

61 227.0 (14.4)

X2 144.5 (1.8)

X16 180.2 not measured in 2014

Depth to Water 

April 2015 (ft)

Increase (Decrease) 

From May 2014 (ft)
Tolk Wells

Plant X Wells

GWDB Water Level Data

Saturated Thickness (ft)

Xcel Water Rights Area

Tolk Plant

Plant X

Area for potential future development

Area of currently un-economic groundwater

Area for potential future exploration

Service Layer Credits: Sources: Esri, HERE,

DeLorme, TomTom, Intermap, increment P

Corp., GEBCO, USGS, FAO, NPS, NRCAN,

GeoBase, IGN, Kadaster NL, Ordnance

Survey, Esri Japan, METI, Esri China (Hong

Kong), swisstopo, MapmyIndia, ©

OpenStreetMap contributors, and the GIS

User Community

12

0

110

100

90

80

7

0

60

50

40

30

110

100

90

80

70

60

50

40

30

30

20

10

60

50

100

90

20

100

40

40

30

30

X2

5 7

10

11

14

X16

17

18

23

25

28

37

40 43

44

45

47

53

54

61

1052308

1052601

1052715

1052811

1052813

1053602

1053608

1061107

1061502

2015 Saturated

Thickness Contours

0 1 2 4 6 Xcel Property

Miles

¦