Executive Field Trip Guide to the NGLA

2013
Senior Executive
FIELD TRIP
of the
Northern Guam
Lens Aquifer
Senior Executive
FIELD TRIP
of the
Northern Guam
Lens Aquifer
1
Objective
Examine, in a single, short trip, the four
physical components of the Northern
Guam Lens Aquifer that determine its
production capacity and its vulnerability to
contamination or misuse. Current conditions
of the aquifer and steps that should be taken
to support sustainable development and
optimal management are also presented and
discussed.
2
Preface
Hafa Adai!
On behalf of the faculty and staff of the University of Guam’s
Water & Environmental Research Institute of the Western
Pacific, I am honored to welcome our island’s senior
leaders and policy-makers to this first offering of our senior
executive short course on Guam’s primary water resource—
our Northern Guam Lens Aquifer. As the island’s premier
source of new scientific research, analysis, and information
on Guam’s water resources, we are committed to supporting
informed policy choices and sustainable management of Guam’s water resources,
especially given the anticipated expansion of our civilian economy and military
activities over the next decade and beyond. For this field trip we have carefully
selected four of the island’s most accessible and instructive sites for an informative
“hands-on” explanation of the aquifer’s principal components, all of which can
be visited well within the span of a single workday. We have also prepared this
field trip guide to provide you with an uncomplicated introduction and concise
ready reference on our island’s most important natural resource. We hope you will
find this valuable and enjoyable, and that you will feel free to call on WERI at any
time for whatever advice and assistance you might find useful in meeting present
and future water resource needs for commercial and military activities on Guam,
and for providing the highest quality of life for both its permanent residents and
visitors.
Sincerely,
Shahram Khosrowpanah, Ph.D., P.E.
Director, WERI
3
Abstract
This field trip takes you to four sites, each of which is a premier example of the four
basic components of the Northern Guam Lens Aquifer: the tight, nonproductive
volcanic basement rock that constitutes the floor of the aquifer; the porous and
soluble water-bearing limestone bedrock that is the source of our drinking water;
the surface catchment that captures the recharging rainwaters; and the features of
the surface that control and distribute the entry of water into the aquifer. At each
site, we observe and discuss the geological and hydrological properties that control
the capture, storage, and production of potable water, and the opportunities
and challenges faced by geologists and engineers in exploring, developing, and
managing groundwater production. While traveling between sites we observe
features of regional importance to groundwater development and aquifer
protection. We also discuss basic facts and statistics related to drinking water
production, consumption, and conservation on Guam and nationwide.
4
Table of Contents
The Northern Guam Lens Aquifer: Basic Facts
The Northern Guam Lens Aquifer: Water Processes
Surface of the Northern Guam Lens Aquifer
Groundwater Basins of the Northern Guam Lens Aquifer
Idealized profile of the Northern Guam Lens Aquifer
Cross-section along the Yigo Trough
6
7
8
9
10
12
Field Trip Map and Schedule of Stops
14
Stop 1:
The Floor of the Aquifer – the Volcanic Basement Rock
16
Stop 2:
The Core of the Aquifer – the Limestone Bedrock
18
Stop 3:
Plumbing of the Aquifer – Surface and Internal Drainage
20
Stop 4:
The Roof of the Aquifer – the Water Catchment System
22
From Sustainable Yield to Sustainable Management
Acknowledgments
Further Reading
Authors
24
26
27
28
5
The Northern Guam Lens
Aquifer: Basic Facts
N
G
L
A
³
³
³
³
³
Geographic extent
all of northern Guam
Total surface area
83 sq mi (214 sq km)
Average annual rainfall
~100 inches / year
467 million gallons per day
Estimated recharge
238 million gallons per day
Current production1
44 million gallons per day
GWA
39
DoD
4
Private
<1
105
15
9
5
9
7
(19% of estimated recharge)
³
Number of production wells
Active: 123
Other:
27
³
Current consumption2
~30 million gallons per day*
Information on the number of wells and production is from Guam EPA, Guam Waterworks
Authority Engineering Department, US Navy, and US Air Force.
2
The gap between current production and consumption is thought to be due to a combination of
loss through leakage and undocumented consumption through unmetered usage.
1
6
The Northern Guam Lens
Aquifer: Water Processes
RA
IN
FA
L
L
Eva
por
atio
SOIL (0-1 ft)³
n
EPIKARST³ Tran
spi
Ove
(10s of feet)
rat
rla
ion
n
fl
o
Infi
w d
ltra
VADOSE
tion
ZONE ³
Int
ern
(100s of feet)
al r
uno
Vad
ff
per os
ont colat e
hs
to y ion
ear
s)
(m
Freshwater
PHREATIC ³
ZONE
(<~200 feet)
Ph
RE
rea
tic
oh
CH
sto
Vad
os
f
a
(m
inu st flo e
tes
w
t
our
AR
rag
s)
GE
ea
nd
flow
Overflow
Spring/Seep
Discharge
7
Surface of the
Northern Guam Lens Aquifer
LIMESTONE TERRAIN
VOLCANIC TERRAIN
SINKHOLES
and other closed
contour depressions
Major geologic faults
Pago-Adelup fault
8
Groundwater Basins of the
Northern Guam Lens Aquifer
GROUNDWATER SETTINGS:
BASAL WATER
PARABASAL WATER
SUPRABASAL ZONE*
* Supra-basal water is found in discontinuous
patches and conduits within this zone.
SIX BASINS
Discharge boundaries
color-coded by basin:
z Hagåtña
z Yigo-Tumon
z Finegayan
z Agafa Gumas
z Andersen
z Mangilao
Basement contours
Sea level contour
Basin boundary (fixed)
Basin boundary (loose)
Pago-Adelup fault
9
Vertical scale is greatly exaggarated. Please see
next page for a “to scale” diagram representation.
Idealized profile of the
Northern Guam Lens Aquifer
T H R E E
Reef
BASAL WATER
t
t
t
t
O F
underlain by seawater
vulnerable to sea water contamination
variable quality water
easy to find (underlies most of northern Guam)
G R O U N D W
PARA-BASA
t underlain by
t resistant to s
nation
t ”upstream”
t more affecte
than basal w
t hard to find
LIMESTONE
g zone
Water table
1:40
Mixin
SALTWATER
T Y P E S
FRESHWATER LENS
Saltwater toe
10
10
W A T E R
AL WATER
y basement rock
sea water contami-
from surface threats
ed by wet-dry cycles
water
S E T T I N G S
SUPRA-BASAL WATER
t
t
t
t
t
t
underlain by basement rock
standing above sea level
invulnerable to sea water contamination
very high quality water — catchment “headwaters”
more responsive to wet-dry cycles than para-basal water
very hard to find (luck is important, even with map...)
e
Mean sea level
VOLCANIC BASEMENT
11
11
PARA-BASAL WATER
This cross section depicts the actual proportions of
the freshwater lens and geologic units along the axis
of the basement valley that heads between Mount
Santa Rosa and Mataguac Hill and extends from there
beneath Dededo to Tumon. Called the “Yigo Trough”
by local hydrologists, it collects and carries fresh
water, much like a surface stream valley, beginning in
the area around Yigo and discharges it into the ocean
in Tumon Bay. The Yigo Trough is the aquifer’s most
prolific producer of drinking water.
BASAL WATER
~75%
Tumon Bay
Mean sea level
of northern Guam
SALTWATER
12
12
<5%
of northern Guam
Water table
FRESHWATER LENS
Saltwater toe
SUPRA-BASAL WATER
Cross-section along
the Yigo Trough
Water found only in isolated conduits and discontinuous patches
~20%
of northern Guam
Mt. Santa Rosa
LIMESTONE
VOLCANICS
FRESH WATER
SALTWATER
NOTE: Vertical scale on this diagram is realistic. The following values are used:
Horizontal and vertical scale: 1 inch = 3168 ft (1 km); Cross-section width 7.5 miles;
Elevations: Mt. Santa Rosa (MSR) +830 ft, central plateau surface +400 ft, volcanic contact
at the coast -800 m, volcanic contact offshore -1500 ft, water table +4 ft, 50% isochlor -200 ft
13
13
Field trip map
and schedule of stops
1
2
3
4
Starting point: Adelup
Stop 1: Mt. Alutom
Stop 2: DPW Quarry
Stop 3: Mataguac Hill
Stop 4: Mt. Santa Rosa
3
2
1
14
14
4
Itinerary
0800-0900
Van meets and pick up participants at Adelup
0930-1000
Stop 1 : THE FLOOR OF THE AQUIFER
(Alutom Formation, Mt. Alutom)
1045-1130
Stop 2 : THE CORE OF THE AQUIFER
(DPW Quarry, Dededo)
1145-1230
Stop 3 : PLUMBING OF THE AQUIFER
(Mataguac Hill Peace Memorial Park)
1245-1315
Stop 4 : THE ROOF OF THE AQUIFER
(Summit of Mt. Santa Rosa)
1345-1400
Van delivers participants to point of departure
Bottled water will be available. Boxed lunches will be provided on the way to Stop #3,
Mataguac Memorial Peace Park, where we restrooms will also be available.
There will be no hiking, but participants are advised to wear appropriate casual field
clothes, headgear, and footwear, and be prepared for intense sunlight. Sunglasses are
advisable for the quarry visit. Safety gear will be provided for the quarry visit.
15
Stop 1: The Floor of the Aquifer
– The Volcanic Basement Rock
Alutom Formation, Mt. Alutom
Here, around the crest of Mount Alutom, are the island’s
best outcrops of the practically impermeable volcanic basement
rock that underlies the entire Northern Guam Lens Aquifer. The
summit of Mount Alutom also provides an impressive view of the
northern limestone plateau—the surface of the aquifer—which we
will visit in the next three stops. To the far northeast can be seen
Mount Santa Rosa, where the volcanic basement rock emerges
above the surface of the northern limestone plateau. The summit
of Mount Santa Rosa will be our fourth and final stop, where we
will be able to see and discuss in more detail the surface features
that control the amounts and rates of aquifer recharge.
16
Hydrologic role of basement rock
Named the Alutom Formation, this hydrologically “tight” volcanic rock forms
subterranean hills and ridges beneath the overlying limestone bedrock. The basement
topography is the single most important consideration for successful groundwater exploration
on northern Guam. Beneath about one-fifth of the plateau surface the basement partitions the
aquifer into six semi-contiguous groundwater basins. Descending groundwater concentrates
along the axes of valleys above sea level and may even be impounded in some small subterranean
reservoirs. Although very difficult to locate, such streams and patches of “supra-basal” water
are the freshest water in the aquifer, and are invulnerable to seawater contamination. The water
descending down the hills and valleys to sea level is concentrated into a “para-basal” rim of
freshwater that is underlain by volcanic basement rock rather than seawater. Because it is thus
very fresh and much less vulnerable to seawater contamination the surrounding “basal” water of
the freshwater lens, the para-basal zone has long been the zone of choice for development and
production of groundwater.
17
Stop 2: The Core of the Aquifer –
the Limestone Bedrock
Barrigada Limestone, DPW Quarry, Dededo
Active quarrying of the limestone here in the “Dededo Coral
Pit” provides some of the island’s best exposures of the rock that
comprises the core of our aquifer. This limestone is actually not
from coral, but is rather a granular, “detrital” limestone, formed in
deeper waters mostly from accumulation of shells and fragments
of shells left behind over millions of years by tiny organisms that
colonize the bottoms of shallow banks and the water above. Fresh
cuts in the quarry walls provide outstanding examples of the kinds of
porosity that constitute the internal plumbing of the aquifer.
18
Hydrologic role of the Barrigada Limestone
The Barrigada Limestone is by far the most extensive and important of the three major
limestone units of the aquifer. Even a casual inspection shows that this limestone is, overall,
noticeably porous. A somewhat closer look, however, also reveals that the porosity of this rock
can vary remarkably over the scale of just a few tens of feet. Thus, even though this rock is very
porous at the regional scale, only about one in three or four exploratory wells usually proves
suitable for production. Production from successful wells can be extremely high, however—500
to 750 gallons per minute. Inside the quarry, we will examine the qualities and features of the
rock that determine the success or failure of new wells and the paths by which contaminants may
enter and move through the aquifer.
19
Stop 3: Plumbing of the Aquifer –
Surface and Internal Drainage
Surface water and sinkhole, Mataguac Hill Peace Memorial Park
In addition to its significance as a World War II historical
site, the Peace Memorial Park provides an outstanding example
of a natural sinkhole, with a visible active swallow hole at its
bottom. The swallow hole has formed along the contact between
the soluble limestone bedrock above and the insoluble volcanic
basement below. Here, spring water that constantly flows from
the nearby spring that forms in the volcanic rock of Mataguac
Hill, and storm waters that occasionally run off the flank of
Mataguac Hill, enter the aquifer and descend some 400 vertical
feet to the water table.
20
Hydrologic role of sinkholes, shafts, and caves
Recharging waters enter the aquifer and descend to the water table in two ways: 1) by
slow (months to years) percolation of water from ordinary rainfall that infiltrates through the
ground surface, and 2) by fast flow (minutes to days) of water that ponds in natural surface
depressions (“sinkholes”) during
heavy storms. The fast flow process
is permanently on display here
in this sinkhole on the flank of
Mataguac Hill, where the perennial
Mataguac Spring provides a modest
but steady flow of water to the
nearby open cave (see photo on
opposite page) and into the swallow
hole located at the cave’s bottom
(see photo below).
21
Stop 4: The Roof of the Aquifer –
the Water Catchment System
Vista of entire aquifer, Summit of Mt. Santa Rosa
This final stop provides a spectacular view of the entire
aquifer surface, including each of its six basins, from the Hagatña
Basin at the extreme southwest; the Finegayan Basin on the far
side of Mataguac Hill, to the west; the Agafa Gumas Basin to the
northwest; the Andersen Basin just to the north; and the Mangilao
Basin, which starts on the southern flank of Mount Santa Rosa
and runs southwest along the Pacific coastline to the southeastern
flank of Barrigada Hill. This view provides a particularly good
perspective of the Yigo-Tumon Basin, which heads between
Mount Santa Rosa and Mataguac Hill and runs southwest beneath
the villages of Yigo, Dededo, Tamuning, and Tumon. The axis
of the Yigo-Tumon Basin, termed the Yigo Trough by local
hydrologists, is the single most prolific production zone of the
aquifer.
22
Hydrologic role of the aquifer surface
All of the water that recharges the freshwater lens begins as rainwater that falls on the
surface of the plateau. Some 70 percent of Guam’s rainfall arrives during its wet season, from
July through December. Ongoing studies of cave dripwaters suggest that hardly any of the other
30 percent that falls during the dry season contributes to recharge of the lens. Consistent with
these findings, a recent independent study of recharge suggests that about 50 percent of total
annual rainfall evaporates or is taken up and transpired by vegetation growing on the plateau,
while the other 50 percent descends through the limestone—either directly to the water table
or onto the flanks of the basement hills and valleys that occupy the 20 percent of the aquifer
within the supra-basal zone. Past studies suggest that over the long term up to about 30 percent
of recharge may descend via fast flow routes, such as observed at the previous stop. Quantifying
aquifer recharge is one of the outstanding challenges of hydrological research on Guam.
23
From Sustainable Yield to
Sustainable Management
24
³
1982 Northern Guam Lens Study:
“The rate of production that can be sustained without
unacceptably degrading water quality.”
So…
What is acceptable quality?
Who decides?
How?
³
NGLS quality target: 150 mg/l chloride
1982 SY: 59 mgd
1992 SY: 80 mgd
³
USEPA standard: 250 mg/l chloride
Current production: ~45 mgd
Current consumption: ~30 mgd
American Waterworks Association
U.S. daily indoor per capita water use: 69.3 gallons
U.S. daily household average: 350 gallons
FAUCETS 10.9
SHOWERS 11.6
16%
17%
LEAKS 9.5
14%
CLOTHES
WASHERS 15.0
22%
BATHS 1.2
2%
DISHWASHERS 1.0
TOILETS 18.5
1%
28%
And for Guam?
For 30 mgd consumption
and 200,000 people
daily per capita consumption = 150 gallons
25
Further Reading
Selected Current and Historical Technical Sources
AECOM Technical Services Inc., 2011, Guam Water Well Testing Study to Support US Marine
Corps Relocation to Guam, Volume Contract Number N62742-06-D-1870, TO 036: Pearl
Harbor, HI, Naval Facilities Engineering Command, Pacific.
CDM, 1982, Final Report, Northern Guam Lens Study, Groundwater Management Program,
Aquifer Yield Report, Camp, Dresser and McKee, Inc. in assoc. with Barrett, Harris &
Associates for Guam Environmental Protection Agency.
Contractor, D.N., and Jenson, J.W., 2000, Simulated Effect of Vadose Infiltration on Water
Levels in the Northern Guam Lens Aquifer: Journal of Hydrology, v. 229, p. 232-254.
Drew, D. and Hötzl, H., 1999, Karst Hydrogeology and Human Activities. Impacts,
Consequences and Implications: Balkema, Rotterdam, 322 pp.
Ford, D. and Williams, P., 2007, Karst Hydrogeology and Geomorphology: London, Wiley
Chichester, 576 p.
Goldscheider, N. and Drew, D., Eds., 2007, Methods in Karst Hydrogeology: London, Taylor &
Francis, 264 pp.
Habana, N.C., Heitz, L.F., Olsen, A.E., and Jenson, J.W., 2009, Vadose flow synthesis for the
Northern Guam Lens Aquifer, WERI Technical Report No. 127: Mangilao, Water &
Environmental Research Institute of the Western Pacific, University of Guam.
Jenson, J.W., and Jocson, J.M.U., 1998, Hydrologic data collection on Guam: FY 1998 Report,
WERI Technical Report No. 83: Mangilao, Water & Environmental Research Institute of
the Western Pacific, University of Guam.
Jenson, J.W., Keel, T.M., Mylroie, J.R., Mylroie, J.E., Stafford, K.W., Taboroši, D., and Wexel, C.,
2006, Karst of the Mariana Islands: The interaction of tectonics, glacio-eustasy, freshwater/salt-water mixing in island carbonates: Geological Society of America Special
Paper, v. 404, p. 129-138.
Johnson, A.G., 2012, A water-budget model and estimates of groundwater recharge for Guam,
Volume U.S. Geological Survey Scientific Investigations Report 2012–5028 , p. 53.
Krešić, N., 2007, Hydrogeology and Groundwater Modeling, Second Edition: Boca Raton, New
York, London, CRC Press/Taylor & Francis, 807 p.
Lander, M.A., Jenson, J.W., and Beausoliel, C., 2001, Responses of well water levels on northern
Guam to variations in rainfall and sea level: WERI Technical Report No. 94, p. 36.
Mylroie, J.E., and Carew, J.L., 1995, Karst development on carbonate islands, in Budd, D.A.,
Harris, P.M., and Saller, A., eds., Unconformities and Porosity in Carbonate Strata, Volume
Memior 63, American Association of Petroleum Geologists, p. 55-76.
Mylroie, J.E., and Jenson, J.W., 2000, The Carbonate Island Karst Model applied to Guam:
Theoretical and Applied Karstology, v. 13-14, p. 51-56.
26
Mylroie, J.E., Jenson, J.W., Taboroši, D., Jocson, J.M.U., Vann, D.T., and Wexel, C., 2001, Karst
features on Guam in terms of a general model of carbonate island karst: Journal of Cave
and Karst Studies, v. 63, p. 9-22.
Partin, J., Jenson, J., Banner, L., Quinn, T., Taylor, F., Sinclair, D., Hardt, B., Lander, M., Bell, T.,
Miklavič, B., Jocson, J. and D. Taboroši, 2012, Relationship between modern rainfall
variability, cave dripwater and stalagmite geochemistry in Guam, USA: Geochemistry,
Geophysics, Geosystems 13 (3).
Siegrist, H.G., and Randall, R.H., 1992a, Carbonate geology of Guam, in Richmond, R., ed.,
Proceedings of the Seventh International Coral Reef Symposium, Volume 2: Mangilao,
Guam, University of Guam Marine Laboratory & Water & Energy Research Institute of the
Western Pacific, p. 1195-1216.
—, 1992b, Carbonate Geology of Guam: Summary & Field Trip Guide, 7th International Coral
Reef Symposium: Mangilao, Guam, Water & Energy Research Institute of the Western
Pacific & Marine Laboratory, p. 39 p.
Siegrist, H.G., and Reagan, M.K., 2008, Geologic Map and Sections of Guam, Mariana Islands
(1:50,000), Revision of original map from USGS Professional Report 403A, 1964, by
Tracey, J.I., Jr., Schlanger, S.O., Stark, J.T., Doan, D.B. & May, H.G. Field interpretations for
2008 revision assisted by Randall, R.H. and Jenson, J.W., Water & Environmental Research
Institute of the Western Pacific, University of Guam, Mangilao, Guam.
Tracey, J.I., Jr., Schlanger, S.O., Stark, J.T., Doan, D.B., and May, H.G., 1964, General Geology
of Guam: US Government Printing Office, Washington, D.C., U.S. Geological Survey
Professional Paper.
Simard, C.A., Jenson, J.W., and Lander, M.A., 2013, in review, Analysis of Salinity in the
Northern Guam Lens Aquifer, in Savarese, M., and Glumac, B., eds., 16th Symposium on
the Geology of the Bahamas and Similar Regions: Gerace Research Center, San Salvador
Island, Bahamas.
Taboroši, D., 2004, Field Guide to the Caves and Karst of Guam: Honolulu, Bess Press, 105 pp.
Taboroši, D., Jenson, J.W., and Mylroie, J.E., 2005, Karst features of Guam, Mariana Islands:
Micronesica, v. 38, p. 17-46.
Ward, P.E., Hoffard, S.H., and Davis, D.A., 1965, Hydrology of Guam: US Government Printing
Office, Washington, D.C., U.S. Geological Survey Professional Paper 403-H.
White, W. B., 1988, Geomorphology and Hydrology of Karst Terrains: New York, Oxford:
Oxford University Press.
Note: The on-line version of this field trip guidebook can be accessed on the WERI website by
searching for ‘WERI Northern Guam Lens Aquifer Field Trip Guide’. It contains links to many of
the documents listed above.
27
Authors
John W. Jenson, PhD
Senior Hydrogeologist & Professor of Environmental Geology
Water & Environmental Research Institute of the Western Pacific
University of Guam, Mangilao, GU 96923
[email protected]
Ph.D. Geology, Oregon State University
M.A. Applied Economics, University of Michigan
B.S. Economics, US Air Force Academy
Dr. Jenson has studied the Northern Guam Lens Aquifer for some two decades since joining the WERI faculty in 1993.
His research encompasses both applied and theoretical groundwater hydrology and related environmental science. Recent
work on Guam includes assessment of newly-drilled and rehabilitated wells, rehabilitation of long-out-of-service wells, and
reconnaissance of promising sites for new production wells. Recent applied work also includes evaluation of the stormwater
drainage potential of a large sinkhole on Andersen Air Force Base, in collaboration with Dr. Taboroši; and an updated study
of spatial patterns and temporal trends in the salinity of water from Guam’s production wells. He is currently supervising the
construction of a new aquifer database and an update of the map of the aquifer basement. Dr. Jenson’s basic scientific research
activities include development of the Carbonate Island Karst Model and reconstruction of past wet-dry cycles and sea levels on
Guam from field geology and geochemical clues in cave deposits on northern Guam. Dr. Jenson also served a 30-year career as
a US Air Force officer, with tours in strategic missile operations and staff duty at HQ Strategic Air Command, HQ US Air Force,
HQ US Forces-Japan, and HQ 13th Air Force.
Danko Taboroši, PhD
Director
Island Research & Education Initiative, Palikir, Pohnpei, FM 96941
[email protected]
Ph.D. Earth Science, Hokkaido University
M.S. Environmental Science, University of Guam
B.S. Marine Biology, College of Charleston
B.A. Geology, College of Charleston
Dr. Taboroši’s research focuses on carbonate geology, karst processes, and coastal and island geomorphology.
His Masters research was a landmark inventory of the karst features of Guam, which included the first thorough
maps of the island’s sinkholes and caves. He has remained active in Guam water resources research. His doctorate
at Hokkaido University took him into detailed interdisciplinary studies of calcium carbonate precipitation, cave
microclimates, limestone coastal processes. He has taught sedimentology, stratigraphy, and oceanography at
the American University of Beirut in Lebanon, and a professional development course on the Northern Guam
Lens Aquifer at the University of Guam in collaboration with Dr. Jenson. Dr. Taboroši is also the Pohnpei-based
Island Research & Education Initiative for which his work includes mapping erosion, and studying water resources
infrastructure and water use on Micronesian atolls. In addition to numerous professional papers, he has authored
textbooks and children’s books for the Federated States of Micronesia as well as Guam, including Field Guide to
Caves and Karst of Guam, Student Atlas of Guam, and Environments of Guam. Dr. Taboroši has traveled in over 100
countries and is fluent in seven languages.
28
Acknowledgments
Special thanks to Mr. Carlos Taitano and
his colleagues at the University of Guam’s
Professional and International Programs
Office for logistic and administrative support
in preparing the field trip and this guide.
Thanks also to Mr. Nathan Habana at WERI
for assistance with maps and photography,
and to Mr. Alfred Santos at the Department
of Public Works Quarry in Dededo for
graciously assisting in preparation and
hosting visits to the quarry.
29
2013
30
Examine, in a single, short trip, the four
physical components of the Northern Guam
Lens Aquifer that determine its production
capacity and its vulnerability to contamination
or misuse. Current conditions of the aquifer
and steps that should be taken to support
sustainable development and optimal
management are also presented and discussed.
ISBN 978-982-9123-58-9
© 2013 WERI