10-Well_Rehab_Rpt_URS_May_2007.pdf

WELL REHABILITATION

REPORT

LUKE AIR FORCE BASE,

GLENDALE, ARIZONA

Prepared for

AIR FORCE CENTER FOR

ENVIRONMENTAL EXCELLENCE

DEPARTMENT OF THE AIR

FORCE

URS Job No. 23443836 May 25,2007

FA8903-16-R-0009

Attachment 10

TABLE OF CONTENTS

Page . INTRODUCTION .................................................................................. 1 1 . .................................................................................. 1.1 PROJECT BACKGROUND 1 1

1.2 OBJECTIVE AND SCOPE .................................................................................... 1-3

................................................................. HYDROGEOLOGIC SETTING 2. 1

2.1 REGIONAL HYDROGEOLOGY .......................................................................... 2-1 ................................................................................. 2.2 LOCAL HYDROGEOLOGY 2-3

PROJECT CHRONOLOGY ...................................................................... 3-1

3.1 WELLN0.7 ...................................................................................................... 3-1

3.2 WELLNO . 11 ........................................................................................................ 3-2

3.2.1 TemperatureISpinner Flowmeter Logging and Depth-Specific Sampling 3-4

3.2.2 Aquifer Test .............................................................................................. 3-5

3.3 WELL NO . 14 ......................................................................................................... 3-6

3.3.1 BrushandBail ............................................................................................. 3-6

3.3.2 Aquifer Test and Depth-Specific Sampling ................................................ 3-7 EVALUATION OF LOG DATA ................................................................ 4-1

. ......................................................................................................... 4.1 WELLNO 11 4-1

4.2 WELLNO . 14 ......................................................................................................... 4-1

ESTIMATION OF AQUIFER HYDRAULIC PROPERTIES ............................... 5-1

DEPTH-SPECIFIC WATER SAMPLE RESITLTS ........................................... 6-1 SUMMARY AND CONCLUSIONS ............................................................ 7-1

REFERENCES ..................................................................................... 8-1

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LIST OF TABLES

1 Well Construction Details 2 Water Quality Parameters and Methods 3 Depth-Specific Sampling Results for Well No. 11

LIST OF FIGURES

1 Site and Well Location Map 2 Well Schematic of Well No. 7 3 Well Schematic of Well No. 1 1 4 Drawdown in Well No. 1 1 (Pumping Well) 5 Drawdown in Well MW- 108 (Observation Well) 6 Well Schematic of Well No. 14

LIST OF APPENDICES

A. Photograph Log of Well No. 7 B. Photograph Log of Well No. 11 C. Caliper Log for Well No. 11 D. Summary of Spinner Flowmeter Log for Well No. 1 1 E. Photograph Log of Well No. 14 F. Aquifer Parameter Calculations

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LIST OF ACRONYMS

amsl

ADWR

AFB

AFCEE

AMA

bgs

EPA

ft/d

OF

gpd/ft gpm gpm/ft

HASP

hp K

LAU

MAU

MCL

mg/L

S

Sc

STL

T

TDS

~ g / l

UAU

URS

Weber

Work Plan

WSRV

Above Mean Sea Level

Arizona Department of Water Resources

Air Force Base

Air Force Center for Environmental Excellence

Active Management Area

Below Ground Surface

U. S. Environmental Protection Agency

Feet per Day

Degree Fahrenheit

Gallons per Day per Foot

Gallons per Minute

Gallons per Minute per Foot

Health and Safety Plan

Horsepower

Hydraulic Conductivity

Lower Alluvial Unit

Middle Alluvial Unit

Maximum Contaminant Level

Milligrams per Liter

Storage Coefficient

Specific Capacity

Severn Trent Laboratories, Inc.

Transmissivity

Total Dissolved Solids

Micrograms per Liter Upper Alluvial Unit

URS Group, Inc.

Weber Group, L.C.

Field Data Collection Work Plan

West Salt River Valley

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1.0 INTRODUCTION

This Well Rehabilitation Report details the activities and presents the results of the rehabilitation work conducted by URS Group, Inc. (URS) on three production wells currently used at Luke Air

Force Base (AFB) in Glendale, Maricopa County, Arizona. The objective of this investigation was to ensure that the three previously-selected production wells (Nos. 7, 11, and 14) would be fully operational and could reliably meet the current water supply requirements of Luke AFB while complying with the recently revised Final Arsenic Rule maximum contaminant level

(MCL) for arsenic.

Luke AFB (also referred to as the Base) is located approximately 13 miles due west of Phoenix.

The water supply system for the Base is comprised of nine groundwater wells; however, since

1995, only six of those wells (Nos. 7, 10, 1 1, 12, 13, and 14) have been used to meet the water demand. Figure 1 shows the location of the Base and the six production wells.

This work was conducted under contract with the Air Force Center for Environmental

Excellence (AFCEE), Contract No. F41624-03-D-8609, Task Order 108.

1.1 PROJECT BACKGROUND

On January 22, 2001, the U.S. Environmental Protection Agency (EPA) revised the MCL for arsenic in drinking water, requiring public water suppliers to maintain arsenic concentrations at or below 10 micrograms per liter (pgll). The target date for compliance with the revised standard is January 23, 2006. Luke AFB, with a population of more than 9,000 military and civilian personnel, relies entirely on groundwater for their potable and non-potable water supplies.

Historical water quality data indicated that arsenic concentrations in the Luke AFB production wells ranged from less than 5 pg/l to 48 pgll, with most arsenic concentrations ranging from 10 to 20 pgll. The data showed that all nine of the production wells have, at least once, produced water with arsenic concentrations at or above the recently revised MCL of 10 pgll.

In 2003, URS was contracted to conduct a Water Quality Alternatives Evaluation for Luke AFB for the purpose of identifying and evaluating cost-effective approaches that would allow the Base to comply with the recently revised arsenic standard. The Water Quality Alternatives Evaluation consisted of a comprehensive review of available data from Luke AFB and a limited field investigation of both the production wells and the water supply distribution system. Field activities included collecting groundwater samples from Well Nos. 7, 1 1, 12, 13, and 14;

conducting a 24-hour pumping (aquifer) test, spinner flowmeter logging, and depth-specific sampling on Well No. 7; pressure testing 13 fire hydrants to obtain pressure and flow

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capabilities; and field testing 36 point-of-use locations along the water supply distribution system for arsenic concentrations. The results of the Water Quality Alternatives Evaluation were presented in a final report (URS, 2004a) to Luke AFB in September 2004.

The water quality samples obtained from Well Nos. 7, 1 1, 12, 13, and 14 during the Water

Quality Alternatives Evaluation indicated that water produced from Well Nos. 7, 1 1, and 14, all located in the southern portion of the Base, was in compliance with the recently revised arsenic standard (arsenic concentrations in Well Nos. 7, 11, and 14 ranged from 6.2 to 9.2 pgll.) Arsenic concentrations in Well Nos. 12 and 13, however, were above the revised MCL of 10 pg/l. (Well

No. 13 contained 13 to 14 pg/l of arsenic; Well No. 12 contained 1 1 to 13 pgll.)

Well No. 7, the deepest of the nine production wells, was selected for spinner flowmeter logging, depth-specific sampling, and aquifer testing. The spinner flowmeter logging, depth-specific sampling, and aquifer testing on Well No. 7 were conducted in August 2003 by URS. Spinner flowrneter data identified seven distinct flow zones within Well No. 7; five of which were sampled. However, arsenic concentrations showed very little variation between the five high flow zones, ranging from 8.1 to 8.5 pgll. From the 24-hour aquifer test, URS calculated aquifer parameters, including transmissivity (T), storativity, and specific capacity (Sc) values.

URS also developed a model of the Base water supply distribution system using the hydraulic engineering model, H20NET. Two scenarios were modeled: the first scenario looked at using only the southern wells (Nos. 7, 1 1, and 14) to supply the Base's water needs, blending the water in the existing infrastructure; the second scenario evaluated a blending option in which the southern wells (Nos. 7, 11, and 14) would be piped directly to a tank and blended. The results showed the first scenario was attainable: however, to confirm the production capacities and arsenic concentrations of Well Nos. 11 and 14, these two wells should be subjected to field-testing similar to the tests conducted on Well No. 7 (spinner logging, depth-specific sampling, and aquifer testing.) The second scenario was also attainable, and showed greater potential for decreasing arsenic in the Base's water supply.

Based on the information obtained during the Water Quality Alternatives Evaluation, URS recommended that Luke AFB shift the reliance of the current water supply distribution infrastructure from Well No. 1 3 to Well Nos. 7, 1 1, and 14. To confirm the production capacities and arsenic concentrations of Well Nos. 11 and 14, these two wells needed to be subjected to field tests similar to the tests conducted on Well No. 7. In addition, 12 months of water quality samples were to be collected from Well Nos. 7, 11, and 14 to establish a baseline, or average, arsenic concentration for each well. (The water quality analytical results for the baseline sampling are provided under separate cover).

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1.2 OBJECTIVE AND SCOPE

The objective of this Well Rehabilitation Project was to ensure that each of the three wells (Nos.

7, 11, and 14) would be fully operational and could reliably meet the current water supply requirements of Luke AFB while complying with the recently revised Final Arsenic Rule.

The scope of work for this project, as outlined in Task Order 21, included:

Removal of the dedicated pump in Well No. 7, brushing the well casing to remove mineral scale, bailing out sediment accumulation, video logging the well before and after brushhail, and re-installing the pump;

Removal of the dedicated pump in Well No. 11, brushing the well casing to remove mineral scale, bailing out sediment accumulation, video logging the well before and after brushhail, conducting spinner logging, depth-specific sampling, conducting a

24-hour aquifer test, re-installing the pump, and re-connecting the well back to the water distribution system; and

Removal of the dedicated pump in Well No. 14, brushing the well casing to remove mineral scale, bailing out sediment accumulation, video logging the well before and after brushhail, conducting spinner flowrneter logging, depth-specific sampling, conducting a 24-hour aquifer test, re-installing the pump, and re-connecting the well back to the water distribution system.

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2.0 HYDROGEOLOGIC SETTING

2.1 REGIONAL HYDROGEOLOGY

The Base is located along the western margin of the West Salt River Valley (WSRV) basin, one of several broad, sediment-filled basins located in the Basin and Range physiographic province.

The Basin and Range physiographic province, which includes the deserts of southern and western Arizona, is characterized by predominantly northwest-trending mountains separated by elongated alluvial valleys. These basins were formed by high-angle faulting which occurred approximately 15 to 3 million years ago (Brown and Pool, 1989). In the WSRV basin, the valley floor is the down-dropped block bounded by the up-faulted mountain blocks. The WSRV lies within the Phoenix Active Management Area (AMA) and is bounded on the west by the White

Tank Mountains, on the south by the Sierra Estrella Mountains, on the east by the Phoenix and

South Mountains, and on the north by the Hieroglyphic Mountains and Union Hills.

Thickness of the basin fill ranges from less than 2,000 feet in the northeastern part of the WSRV to over 10,000 feet deep in the southwestern portion of the WSRV and in the vicinity of the Base

(Edmonds and Gellenbeck, 2002). The basin fill consists of alluvial sediments, primarily clay, silt, sand, and gravel. Subsequent to the active faulting, gradual subsidence of the center portion of the basin resulted in the finer-grained sediments (sands, silts, and clays) being deposited near the center of the basin and the coarser-grained sands and gravels being deposited near the edges of the basin. As a result of Basin and Range faulting, the WSRV, prior to the Quaternary, was a closed basin (i.e., no surface water outlet) no surface water outlet), in which lakes and playas formed. Significant evaporite deposits, including halite, anhydrite, and gypsum, were deposited in the southwestern portion of the WSRV. The Luke Salt Body, shaped in a triangular dome, is the largest evaporite body in the WSRV; it covers an area of over 60 square miles and lies beneath the Base and portions of the towns of Litchfield Park, Avondale, and El Mirage. The

WRSV basin opened during the Quaternary period and the Salt River and other rivers in the area began to transport sediment through the basin, resulting in the deposition of a thin layer of fluvial sediments.

The hydrogeologic units of the WSRV in the area of the Base consist of, in descending order:

Upper Alluvial Unit (UAU), Middle Alluvial Unit (MAU), Lower Alluvial Unit (LAU), the Luke

Salt Body, and Basement Complex (Corkhill, et al., 1993). The UAU, MAU, and LAU are alluvial basin-fill units of middle-to-late Tertiary and early Quaternary age (Corkhill et al., 1993). The Base wells produce water from both the MAU and the upper portion of the LAU.

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A brief description of the hydrogeologic units, in descending order, is presented below.

Upper Alluvial Unit: The UAU, which has historically been the most important aquifer in the

Valley, consists mainly of silty sands and gravelly sands with clay and silty clay lenses. In the vicinity of the Base, the UAU is approximately 300 feet thick (Corkhill et al., 1993).

Groundwater in the UAU, when present, generally occurs in unconfined conditions. In the vicinity of the Base, most of the UAU has been dewatered.

Middle Alluvial Unit: The MAU consists of silt-size particles and clay, with occasional sand and gravel stringers, and evaporites present in the lower section. These deposits are indicative of a lake and/or playa environment. The MAU ranges from 600 to 800 feet thick in the vicinity of the Base (Corkhill et al., 1993). The MAU is considered an aquiclude and produces confining conditions in groundwater contained in the LAU.

Lower Alluvial Unit: The LAU lies directly on the Basement Complex and consists primarily of coarse-grained sand and gravel bound by calcite cement, grading to finer-grained sediments toward the basin center. Due to the coarse-grained sediments, the LAU is an important aquifer. It attains a maximum thickness of over 10,000 feet in the basin center. In the vicinity of the Base, the LAU is approximately 500 feet thick.

Luke Salt Body: The Luke Salt Body formed from evaporite deposits within the LAU and has deformed the overlying LAU and MAU sediments. The UAU is undeformed. The apex of the salt dome is located approximately 1 mile east of the Base airfield and may occur as shallow as

500 feet below ground surface (bgs) (Rauzi, 2002). The salt dome is between 5,000 to 10,000 feet thick and trends northeast. According to Eaton et a1 (1 972), the top of the salt dome beneath the Luke AFB ranges from approximately 1,000 feet bgs in the northwestern corner of the Base to approximately 1,190 feet bgs along the western edge of the Base. However, lithologic logs from wells drilled on the Base to depths of 1,000 to 1,220 feet do not report encountering the salt body.

Basement Complex: The Basement Complex, which forms the floor and margins of the WSRV basin, is composed of various Precambrian-age crystalline rocks (schist, granite, quartzite). The rocks comprising the basement complex have low permeability and porosity and, although these rocks may contain small quantities of groundwater in fractures and joints, the basement complex is not considered to be part of the regional aquifer.

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2.2 LOCAL HYDROGEOLOGY

The regional hydrogeologic information presented in Section 2.1, used in conjunction with lithologic logs from wells drilled on the Base, can provide a good interpretation of the hydrogeology beneath the Base. Four deep (1,000 feet or more) wells were drilled on the Base in 1985; all four wells have good, detailed lithologic logs. Three of the wells are described as test wells (Test Wells 1, 2, and 3) and are recorded under the Arizona Department of Water Resources (ADWR) well registration nos. 55-507977, -507978, and -507979. The fourth well that has a lithologic log associated with it is designated as "Luke AFB Well No. 1" and has a registration number of 55-5 10325. (This is not the same Well No. 1 as located near Building 283, on the northeast end of the Base; it has an ADWR registration number of 55-609882 and was constructed in 194 1 .) There are no known lithologic logs for Well Nos. 7 or 1 1.

Test Well 1 was located just north of Super Sabre Street but was abandoned due to high chloride concentrations. Test Well 2 became Well No. 13, which is located near the center of the Base.

Test Well 3 became Well No. 14. Luke AFB Well No. 1 is reportedly located north of Well No.

7 and Building 983.

The geologic logs from the four wells indicate, in general, fine- to coarse-grained sediments

(gravels, sands, silts and silty clays) from ground surface to approximately 250 to 290 feet bgs.

From approximately 250 to 290 feet bgs, the lithology becomes finer-grained (predominately clays, silty clays, and clayey sands). This gradation to finer-grained sediments may indicate the contact between the UAU and the MAU. Two of the four wells, Luke AFB Well No. 1 and Well

No. 13 (Test Well No. 2), describe interbedded layers of brown, "sticky" clays, sandy clays, silty clays, and clayey sands from approximately 270 feet to at least 500 feet bgs. Geologic logs from

Test Well No. 1 and Well No. 14 (Test Well No. 3) describe coarser sediments, ranging from clayey sand to gravelly sand, from approximately 350 to 485 feet bgs.

A 30 to 80 foot thick, medium- to coarse-grained sandy layer, described as sand, sandy gravel, and gravelly sand, was encountered and noted in the three test wells between 500 and 580 feet bgs. Well Nos. 7, 1 1, and 14 all have perforated intervals within this zone. A similar sandy zone was encountered in Luke AFB Well No. 1 between 650 and 690 feet bgs.

No evaporites or volcanics were noted in the three test well logs. However, the lithologic log from Luke AFB Well No. 1 describes gypsum fragments mixed with clay from 690 to 800 feet bgs, and basalt from 800 to 855 feet bgs, underlain by more clay to 915 feet bgs. Beneath the clay, from 915 to the bottom of the hole, at 1,000 feet bgs, was sand. The three test wells all encountered predominately clay or clay mixed with sand (clayey sand or sandy clay) from

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600 feet bgs to the bottom of the holes (1,004 to 1,220 feet bgs). These well logs suggest that the

MAU beneath Luke AFB may be at least 800 feet thick.

Static water levels were noted and recorded during video logging of the three production wells.

The depth to groundwater based on the video logs is shown below for each well.

*amsl = above mean sea level

Groundwater Depth to Water

Groundwater elevations are based on land surface elevations taken from the U.S. Geological

Survey 7.5-minute El Mirage Topographic Quadrangle Map (UDGS, 1957).

Well No. 7

Well No. 1 1

Well No. 14

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3 00

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3.0 PROJECT CHRONOLOGY

All field activities associated with this Well Rehabilitation task were conducted using protocols established in the Field Data Collection Work Plan (Work Plan) developed specifically for this project (URS, 2004b). The field activities were conducted following guidelines established in the Health and Safety Plan (HASP), included in Appendix A of the Work Plan. Weber Group, L.C. (Weber) of Chandler, was contracted to conduct the brushing and bailing of the three wells and to perform down hole video logging and caliper logging.

3.1 WELL NO. 7

Well No. 7 is located north of Spad Street at the northwest comer of Building 916. The well is surrounded by a 7-foot-high brick wall; access is through a doublewide gate on the north side of the walled structure. Photographs of Well No. 7 are provided in Appendix A of this report. The

ADWR well registration (no. 55-609884) for Well No. 7 indicates that the well is 1,200 feet deep, with an 18 inch casing diameter, and was constructed in June 1968. A video log of Well

No. 7 provided by the Base, dated March 2001, indicated that the well was blocked at an approximate depth of 1,149 feet with soft sediment fill.

Weber removed the turbine pump from Well No. 7 on November 17, 2004. Five days later, Weber conducted a video log of Well No. 7 to determine the condition of the well casing and the extent of plugging, or encrustation, of the slot openings. The video also provided a current static water level measurement and confirmation of the reported perforated intervals and well depth.

Based on the video, the static water level was at 332 feet bgs (on November 22, 2004.) The water was very murky from 332 to approximately 490 feet bgs, but cleared up somewhat after

490 feet bgs. According to the Well Driller's report for Well No. 7, there were four perforated intervals: 534 to 561 feet bgs, 564 to 572 feet bgs, 906 to 924 feet bgs, and 966 to 975 feet bgs.

Due to the murky water and significant mineral scale on the well casing, however, only three intervals could be determined: (1) 532 to 575 feet bgs, (2) 904 to 925 feet bgs, and (3) 965 to 975 feet bgs. The mineral scale of the well casing increased with depth. The slots were noted to be approximately 75 percent open from 532 to 553 feet bgs, 50 percent open from 553 to 575 feet bgs, but totally plugged from 575 to 904 feet bgs. Slots in the interval of 904 to 925 feet bgs were approximately 50 percent open, but from 925 feet bgs to the bottom of the well, the slots were 60 to 80 percent plugged. The bottom of the well, as tagged by the video, was at 1,144 feet bgs. A schematic of Well No. 7 is presented on Figure 2.

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Weber began brushing Well No. 7 on December 9, and finished after 45 hours, on December 11, 2004. The "brush" consisted of a 15 foot stem of pipe with several (approximately 10) small-diameter wire brushes attached to the stem. The wire brush and scraper are used to dislodge debris from inside the casing and screen. Brushing and scraping are effective inside the well screen and casing, but have no effect on the surrounding formation. Brushing began at the water level (approximately 330 feet bgs) and worked downward to the bottom of the well, then back up again. After brushing every 200 feet, Weber would bring the stem up, check the brushes, and replace the worn ones.

At the end of the brushing operation on December 11, Weber measured 16 feet of sediment accumulated in the bottom of the well due to the brushing operation. Weber bailed out the sediment and disposed of the sludge off-site. The sludge, or scale, mixed with mud and sand, was black and oily.

A second video of Well No. 7 was conducted on December 15, 2004, and showed that 75 to 80 percent of the perforations were open after the brushing. Static water level on December 15 was

328 feet bgs. This represented a rise of approximately 6 feet in the static water level attributable to opening of additional well screen, which allows more access to the surrounding aquifer. Table

1 provides a summary of well construction information, as evidenced by the video logs, for Well

Nos. 7, 1 1, and 14.

After the second video logging of Well No. 7 was completed, the turbine pump was re-installed by Weber. The pump was run for several hours and bacteria samples were collected prior to re-connecting the well back to the drinking water system.

3.2 WELL NO. 11

Well No. 11 is the southern most well of the Base production wells. It is located inside a small brick building on Super Sabre Street, across the street (easi) from Building 101 7. Photographs of the well set up and building are provided in Appendix B. According to the well registration

(ADWR no. 55-609887) for Well No. 1 1, the well has an 18 inch casing diameter, is 820 feet deep, and was constructed in 1976. Based on a video log conducted on Well No. 11 in March

2000, there was a question as to whether there were casing reductions from 18 inch to 16 inch diameter at approximately 273 feet bgs and from 16 inch to 14 inch diameter at 391 feet bgs.

The March 2000 video noted the bottom of the well ("fill") at 739 feet bgs.

On January 14, 2005, Weber began dismantling the pump from Well No. 1 1. The initial plan was to use a 50 ton crane to remove the turbine pump from the well; however, upon closer

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examination, Weber determined that a larger (70 ton) crane would be necessary to remove the pump, based on the weight of the pump, the height of the building, and the longer-than-anticipated reach of the crane.

On January 21, 2005, the pre-brushing video was conducted. The video showed a static water level of 272 feet bgs and cloudy water to approximately 380 feet bgs. Although the water was cloudy, it appeared that there were two casing reductions: one at 272 feet bgs, and a second at

389 feet bgs (discussed in detail below). The video showed that the well was constructed with a continuous-slot well screen, sometimes referred to as Johnson rod-based wire-wrapped screen.

However, the well casing was heavily encrusted, making it difficult to see 'the slots and to distinguish between the screen and blank sections. All of the perforated intervals appeared to be completely plugged. At 734 feet bgs, the top of a steel pipe, approximately 2 inches in diameter, was observed; the pipe length continued down, and at 745 feet bgs, a second pipe became visible. At 748 feet bgs, the two pipes appeared to be connected to an apparatus, approximately

14 inches in diameter, which was covered with sediment, and totally obstructed the well. This apparatus was probably an old pump that became stuck in the casing screen. The video could not be continued below 748 feet bgs. A schematic of Well No. 11 is presented on Figure 3.

Weber began brushing the well on February 1,2005, starting at approximately 292 feet bgs down to 745 feet bgs. Weber finished brushing and swabbing the well on February 7. A total of 34 hours were spent brushing Well No. 1 1.

On February 14, 2005, the second video and a caliper log were conducted in Well No. 11. The caliper log was conducted because of the uncertainty of the casing diameter. In order to determine the size of submersible pump for the aquifer test, Weber needed to know the exact diameter of the casing. The caliper tool had three mechanical arms that extend outward from the center stem to measure the inner diameter of the casing or open borehole.

The second video showed a definite improvement fiom pre-brushing condition; however, the slots were still 80 to 98 percent plugged. The wire wrap in the second video was actually visible and four screened intervals were distinguishable: (1) from 396 to 51 1 feet bgs, (2) 564 to 592 feet bgs, (3) 633 to 667 feet bgs, and (4) 724 to somewhere below 745 feet bgs. Static water level in Well No. 11 on February 14, 2005, was at 285 feet bgs. This is an increase of approximately 7 feet of static water level, which may represent more access to the aquifer system.

The caliper log showed that the casing was 18 inches in diameter the entire length except for two points: at 270 feet and 388 feet bgs. At those two points, a section of casing approximately

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5 feet long was spliced into the casing string. The diameter of those two splices was approximately 19 112 inches. Hence, instead of two reductions in the casing diameter, it was actually two 5 foot long points of larger-sized casing diameter. (The reason for the two larger-sized casing splices is unknown.) A copy of the caliper log is provided in Appendix C.

3.2.1 Temperaturelspinner Flowmeter Logging and Depth-Specific Sampling

Southwest Exploration Services, LLC (Southwest) was contracted to conduct the temperature and spinner flowmeter logging and collect the depth-specific water samples from Well Nos. 11 and 14. On March 9,2005, immediately preceding the 24 hour aquifer test, Southwest conducted a temperature log of Well No. 11 under static conditions. After the temperature log was completed, the pump was turned on and the aquifer test began. Approximately one hour into the aquifer test, a second temperature log, under pumping conditions, was conducted, followed by spinner flowmeter logging.

A spinner flowmeter is a tool designed to measure vertical fluid velocity at various depths in a well. Spinner flowmeters are relatively simple tools, consisting of a centralized logging tool with an impeller mounted on the bottom. The tool counts the number of rotations of the impeller using an optical or magnetic sensor. The counts are expressed as counts per second. The counts per second are a function of fluid velocity, the speed of the logging tool in the well, and the size and shape of the impeller. Southwest conducted spinner flowmeter logging in the pumping well using 30, 50, and 70 counts per second.

Upon completion of the spinner flowmeter logging and evaluation of the data, it was decided by

URS and Southwest to collect depth-specific water samples from the following five zones: 396, 564, 635, 680, and 720 feet bgs. Selection of theses five zones was based on where the spinner log showed a significant contribution to the total flow from the well. An evaluation of the spinner flowmeter log for Well No. 11 is presented in Section 4.1, and a summary of the log, under pumping conditions, is provided in Appendix D.

A small-diameter sampling tool was used to collect a discrete water sample from each of the five zones. The sampling tool was approximately 2 inches in diameter and was lowered through the sounding tube. The sampling tool was disassembled and decontaminated before each depth-specific water sample was collected. The water samples were collected in the appropriate laboratory bottles, packed on ice, and shipped to Severn Trent Laboratories, Inc. (STL) in Denver, Colorado for analysis of the parameters listed in Table 2.

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On March 25, after the aquifer test but prior to removal of the temporary submersible pump, spinner logging was conducted again, under static conditions. The static logging was run at 30, 40,50, 60, and 70 counts per second.

3.2.2 Aquifer Test

A 75 horsepower (hp) submersible pump, set at 377 feet bgs, was temporarily installed by Weber and used for the aquifer testing of Well No. 11. Pumped water was discharged through a 6 inch diameter irrigation pipe to a discharge point approximately 100 feet northwest of the well and into a drainage canal outside of the fenced area surrounding Well No. 11. An orifice weir and manometer were installed on the end of the discharge pipe to measure flow rate.

Well MW-108, a monitor well located on the south side of Super Sabre Street, approximately

1,900 feet northeast of Well No. 1 1, was used as an observation well. Well MW-108 (ADWR registration no. 55-5 15901) is 430 feet deep, with a 6 inch casing diameter from ground surface to 343 feet bgs, 4 inch casing diameter from 343 feet to 420 feet bgs, and screened (Johnson screens) from 350 to 420 feet bgs. A pressure transducer was installed in Well MW-108 several days prior to the aquifer test to collect background water level data.

Step-drawdown tests are commonly used prior to a constant-rate aquifer test to evaluate the performance of the well at progressively increasing pumping rates and to select the optimum pumping rate for the constant-rate test. However, a step-drawdown test was not conducted on

Well No. 11 because it is a production well that is currently in service and hence the optimum pumping rate is already known based on normal operations.

Static water level was measured by a manual sounder in both Wells No. 11 and MW-108 just prior to the initiation of pumping on March 9 and compared to the pressure transducer readings.

Readings from both wells were within 0.10 feet of the manual measurement. Depth to groundwater, as measured by the pressure transducers, in Well No. 11 was 284.15 ft bgs, and

271.81 ft bgs in well MW-108.

The aquifer testing of Well No. 1 1 began at 10: 15 a.m. on March 9,2005, and was conducted for

24 hours at a rate of 560 to 577 gallons per minute (gpm). The normal operating discharge rate of Well No. 1 1 is approximately 1,100 gpm.

Water levels measured in Wells No. 11 and MW-108 were plotted versus time on a semi-logarithmic plot. The plots are provided in Figures 4 and 5, respectively. Residual drawdown, or water level recovery, was measured in the pumped well and observation well for the purpose of estimating aquifer hydraulic properties.

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Water levels in Well No. 11 dropped approximately 52.5 feet in the first 10 minutes then gradually stabilized to a maximum drawdown of 59 feet after approximately 3 hours and 50 minutes. Depth to groundwater after 24 hours of pumping was 271.98 feet bgs. Maximum drawdown in MW-108 was 0.55 feet after 24 hours. The Sc of the well pumping at 560 gpm at the end of the test was approximately 9.8 gallons per minute per foot (gprnlft) of drawdown.

Within 30 minutes after the end of the aquifer test, water levels in Well No. 11 had recovered to

85 percent of pre-pumping water level (to 292.93 feet bgs) and at 24 hours after the test, had recovered to 96 percent (within 2.5 feet) of pre-test water levels.

3.3 WELL NO. 14

Well No. 14 is located at the western end of the southwestern F-16 Parking Ramp, north of Super

Sabre Street, and near Building 996. Photographs of the well house and associated equipment are provided in Appendix E. The ADWR registration number for Well No. 14 is 55-507977.

Well No. 14 was constructed in March 1985 and, according to the well driller's report, is 910 feet deep, has a 16 inch casing diameter from ground surface to 490 feet bgs, then 14 inch casing diameter from 490 feet bgs to the bottom of the well.

Weber pulled the dedicated pump from Well No. 14 on May 3,2005, and the pre-brushing video log was conducted by Southwest on May 6, 2005. The video showed five separate screened

(Johnson wire-wrap) intervals: (1) 483 to 553 feet bgs, (2) 573 to 603 feet bgs, (3) 683 to 709 feet bgs, (4) 743 to 763 feet bgs, and (5) 819 to 862 feet bgs. The camera encountered fine sediments at 862 feet bgs, indicating the bottom of the well. The well has two casing diameter reductions: one at 386 feet bgs and one at 438 feet bgs. A caliper log was not run on the well, but it was assumed that the reductions were 14 inches at 386 feet and 12 inches at 438 feet. A schematic of Well No. 14 is presented on Figure 6. Static water level in Well No. 14 on May 6 was 3 12 feet bgs.

The top two screened intervals were shown to be clean and open, with no more than 10 percent of the openings clogged with sediments and encrustation. However, the openings of the lower three intervals were approximately 90 percent encrusted, and therefore, the decision was made to brush and bail the lower 180 feet of Well No. 14.

3.3.1 Brush and Bail

Weber began brushing Well No. 14 on May 23, 2005 and continued May 26, 2005. Sediment was bailed from the bottom of the well from May 27 through June 1, 2005. A post-brushing video was conducted of the well on June 6, 2005. The post-brushing video showed a definite

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improvement in the screen. The upper two intervals were clean and open prior to brushing, but after brushing, the third interval (683 to 709 feet bgs) was also clean and about 99 percent open.

The screen on the lower two intervals was significantly cleaner, i.e. no encrustation on the wire-wrap; however, fine-grained sediments which could potentially clog the screened area were seen behind the screen in the formation.

3.3.2 Aquifer Test and Depth-Specific Sampling

On June 2,2005, prior to the planned aquifer test, a pressure transducer was installed in a nearby monitor well, MW-5, in order to obtain background water level data for Well No. 14. Well

MW-5 is located approximately 600 feet west-southwest of Well No. 14, in the parking lot north of Building 993. Static water level in well MW-5 on June 2 was 273.20 feet bgs. According to the well driller's report for MW-5, the well is 410 feet deep and perforated from 344 to 410 feet bgs.

A temporary submersible pump and two access tubes (one for the water level sounder and one for the depth-specific sampling tool) were installed in Well 14 on June 14 and 15, 2005. The temporary pump was set at approximately 410 feet bgs, between the two casing reductions, and within the 14 in casing diameter interval. A McCrometer propeller meter was installed on the discharge pipe to measure flow rate. The 24 hour aquifer test, spinner flowmeter logging, and depth-specific sampling were planned to begin the morning of June 16. Prior to the aquifer test, a static temperature log and spinner flowrneter log were conducted on the morning of June 16.

The spinner flowmeter was run at 30,50, and 70 counts per second.

Static water level in Well No. 14, prior to the aquifer test, was 299.95 feet bgs. Upon completion of the static logs, the submersible pump was turned on at 1 1 :35 AM to begin the 24 hour aquifer test. The beginning flow rate was 500 gpm. Water levels dropped to 389 feet bgs within the first

90 seconds. Within three minutes of pumping, the storm drain to which the pumped water was being directed to began to back up and flood the ground surface. The aquifer test was then stopped. The discharge pipe was disconnected and re-connected to a different storm drain to the south.

At 12:46 PM, the pump was turned on to restart the aquifer test. The water level in Well No. 14, just prior to restarting the pump at 12:46 PM, was 309.44 feet bgs. At 12:48 pm, the flow meter reading was 250 gpm and water levels had dropped to 404.2 feet bgs. The temporary pump was set at 410 feet bgs. Weber, believing that the pump had been wired incorrectly, recommended the test be aborted again and they (Weber) re-wire the pump. At 155 pm, the pump, having been re-wired, was restarted on. The water level in Well No. 14 at 1 :54 PM was 314.00 f t bgs.

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Within 60 seconds of restarting the pump, the pump shut off automatically. One more attempt was made that afternoon to begin the aquifer test. However, it was concluded, based on discussions between URS and Weber, that due to the well casing reductions, the current pump setting, and the low Sc of the well (defined as pumping rate divided by drawdown), an aquifer test was not feasible on this well on this date.

Sc for Well No. 14, calculated from the few minutes of pumping conducted on June 16, ranged from approximately 2.8 to 5.5 gpdf t . According to a well pumping document from the Base's files, a 24 hour aquifer test was conducted on Well No. 14 in April 1985: flow rate was 500 gpm, maximum drawdown was 95 feet, resulting in a Sc of 5.3 gpdf t .

For comparison, the Sc for Well No. 7, as determined from the aquifer test in August 2003, was about 9.8 gpdf t . Well No. 11 also had a Sc of 9.8 gpdf t , calculated from the March 2005 aquifer test.

Pumping water levels in Well No. 14 had declined to depths just above the pump setting, which allowed air into the pump, causing surging and eventually total cessation of pumping. The pump could have been lowered to a depth below the pumping water level; however, because the well casing reduced to 12 inch diameter at 438 feet bgs, the well would not accommodate the pump and the two access tubes at the lowest depth. A smaller depth-specific sampling tool may have been available from another sub-contractor, but procuring another sub-contractor would have required Well No. 14 to be off-line for additional time. An aquifer test performed without conducting depth-specific sampling was not a primary objective of this investigation. After discussions with Weber and a review of existing data, URS decided that the additional costs and time required to remove the temporary pump, add more pipe, then lower the pump to a deeper setting, and re-install a smaller diameter access tube, if possible, were beyond the anticipated scope and costs of this project. In addition, water demand for the Base was high in June and

Well No. 14 was needed back on line as soon as possible to contribute to the water supply.

On June 22, 2005, Weber, URS, and Luke AFB staff met to discuss the current condition of the dedicated pump for Well No. 14. Weber pointed out that the current submersible pump and some of the lengths of column pipe from Well No. 14 were in need of serious repair.

In order to repair the well appurtenances, a new pump was purchased through base operations and installed. Thirteen (13) lengths of the column pipe were also replaced at that time. After installation, the pump and motor were tested, but the equipment failed and was found to be inoperable.

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The motor and pump were removed from Well No. 14 in March 2006 because the pump was inoperable. After Weber obtained a new motor, it was replaced along with the pump and column pipe on June 14,2006. The motor that was removed from Well No. 14 in March 2006 was a 75 hp 3-phase motor, and it was replaced with a 100 hp 3-phase motor. Following the installation of the pump, new motor, and column pipe, the well was operated for several days in order to purge the well properly prior to bacteriologic sampling.

The analysis of the bacteriologic sample did not reveal any coliforms, which allowed Well

No. 14 to be reconnected to the Base water system.

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4.0 EVALUATION OF LOG DATA

4.1 WELL NO. 11

As discussed in Section 3.2.1, temperature and spinner flowmeter logging were conducted on

Well No. 11 under both static and pumping conditions. Static temperature was relatively constant throughout the well, beginning at 78 degrees Fahrenheit (OF) at 372 feet bgs (the bottom of the access tube) to 79OF at 738 feet bgs. A slight increase, to 80°F, occurred at 567 feet bgs, indicating a flow zone at that point. Temperature logging under pumping conditions were very similar with the exception that the increase seen at 567 feet was a pronounced peak. Under static conditions, the spinner flowmeter logs indicate that the primary flow zone into Well No. 11 is between approximately 566 and 570 feet bgs, with a lesser flow zone between the interval of 41 0 and 420 feet bgs. Under pumping conditions, four flow zones were identified:

Under pumping conditions, the uppermost interval, 41 8 to 455 feet bgs, became the primary flow zone. The uppermost perforated interval in Well No. 1 1 is from 396 to 5 1 1 feet bgs. Depth-specific samples were collected from Well No. 11 at 396 feet, 564 feet, 635 feet, 680 feet, and 720 feet bgs. Four of the five depths were selected based on indications of distinct flow zones.

The 635 foot depth interval was selected because there was a perforated interval from 633 to 667 feet bgs that was not recognized in either the temperature or spinner flowmeter logging.

Flow Zone (feet bgs)

418 - 455 560 - 572

720 - 738

4.2 WELL NO. 14

As discussed above in Section 2.2, the geologic log from Well No. 14 (Test Well No. 3), describes a medium- to coarse- grained sandy interval from 390 to 480 feet bgs, which correlates well with the high flow zone seen in Well No. 11. The other three flow zones identified in Well No. 11 are correlative with clay zones with less than 30 percent silty sand in the geologic log from Test Well No. 3.

Rate (gpm)

8 5 5 0

Static temperature in Well No. 14 ranged between 81.5OF at 425 feet bgs at the bottom of access tube to 85OF at 868 feet bgs. Noticeable differential temperature increases occurred at 494 feet, Contribution to ~ o t s l low Into

Well (%)

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550 feet, and 572 feet bgs. The static spinner flowmeter logs indicated flow coming in just below the top of the uppermost perforated interval, at 490 and then between 540 and 550 feet bgs. Minor but uniform flow was noted from 570 feet bgs to the bottom of the hole.

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5.0 ESTIMATION OF AQUIFER HYDRAULIC PROPERTIES

The two most important aquifer hydraulic properties are T and storage coefficient (S). T is defined as the rate of flow in gallons per minute through a vertical section of aquifer one foot wide that extends the entire saturated thickness of an aquifer under a hydraulic gradient of one

(Driscoll, 1986). A higher T value means the aquifer system yields water more easily than an aquifer with lower T. The S or storativity represents water that is stored within the interstitial spaces between the lithologic materials that make up the aquifer (i.e., clays, silts, sands, and gravels). This value represents how much water can be removed by pumping (Driscoll, 1986).

Although two aquifer tests, one on Well No. 11 and one on Well No. 14, were anticipated for this

Well Rehabilitation Project, an aquifer test on Well No. 14 proved unfeasible due to the Sc and well construction. Therefore, the aquifer hydraulic properties discussed in this section are based solely on data obtained from the Well No. 11 aquifer test.

Aquifer parameters were calculated using AQTESOLV' Pro For Windows (Duffield, 2000) aquifer test analytical software. The AQTESOLV' calculations were made by matching modeled drawdown curves to the actual aquifer test data. Charts showing the data and the solution curves are provided in Appendix F.

The Cooper-Jacob and Theis Residual Recovery solutions for a confined aquifer in

AQTESOLV' were used to calculate an estimated aquifer T. The Cooper Jacob (1946) method was used on the water level data obtained during the aquifer test, and the Theis (1935) method was used on the recovery water level data.