report documentation form€¦ · abstrac1' pilot field tests were conducted in the continuing...
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REPORT DOCUMENTATION FORMWATER RESOURCES RESEARCH CENTER
University of Hawal I at ManoaTechnical Memorandum 2COWRR 03-a, C, D, E, F;Rpnort No. 76 Field-Group O~; 06-a
9Grant AgencyCity and County of HonoluluHonolulu Board of Water Supply;State of Hawaii Department ofLand & Natural Resources
5NO. ofPages ix + 42
42
July 1984"ReportDate
6No. of 17NO. ofTables 2 Fiaures
Membrane Water-Storage Enclosures:A Pilot Study in East Loch, PearlHarbor, Hawaii
Dr. Yu-Si FokMr. Edwin T. Murabayashi
3Title
1 ReportNumber
IlAuthor(s)
10Grant/Contract No.003924 (SVS>
11pes_c::!!P_~()r§_:__ ~ater _storage,--~able __dams,_~r_eservoir_linings, __*_rese~oir __storage, *marbranes, hydraulic models
Identifiers: *stream-water storage, East Loch, West Loch, Pearl Harbor,Oahu. Hawaii
12Abstract (Purpose, method, results, conclusions)
Pilot field tests were conducted in the continuing conceptual devel0Irmf>nt of using impermeable membranes as separating liners to store freshstream water in an embayment. The storage of fresh water in the ocean wasconceived as a less expensive way of storing surplus stream water for subsequent use than in land-based rigid dams and reservoirs. Three basictypes of nanbrane storage enclosures were tested: floating reservoir, bag,and curtain. Each has its particular advantages and disadvantages whichdetermine their suitability to any particular application. The testingtook place in East Loch of Pearl Harbor, a protected inland estuarineembayment, to capture the freshwater flow fran Kalauao Springs near Pearlridge on oahu, Hawaii. The tidal effect, particularly low tide, has asignificant effect on the enclosures. On the curtain, the effect was theamount of slack needed to retain the water captured at high tide as thetide recedes. With the OPen reservoir and bag, low tide left the enclosuregrounded and unsupported on the muddy bottan. A site needs sufficientwater depth to keep the enclosures afloat at all times. A rotating collarwould prevent the bag and OPen reservoir fran becoming twisted around ananchor p:>int. A membrane floating canal and pipeline for water transmission on the ocean surface were also develoPed and tested successfully. Inall testing, 6-mil p:>lyethylene film was used as the membrane during thisproof-of-concept stage. Sufficient progress has now been attained that inthe next stage a first priority effort should be the selection of a suitable operational quality membrane. No adverse environmental impacts weredetected during or after the pilot study.
2540 Dole Street· Honolulu. Hawaii 96822 • U.S.A.• (808) 948-7847
AD'lHORS:
Dr. Yu-Si FokProfessor of Civil EngineeringResearcher, Water Resources Research centerUniversity of Hawaii at Manoa(808) 948-7298
Mr. Edwin T. MurabayashiResearch AssociateWater Resources Research centerUniversity of Hawaii at Manoa(808) 948-8008
$4.00/copyChecks payable to: Research Corporation, University of Hawaii
Mail to: University of Hawaii at Manoawater Resources Research center2540 Dole StreetHonolulu, Hawaii 96822Tel.: (808) 948-7847 or -7848
MEMBRANE WATER-SlORPGE EN(l,()S{JRES:
A PILOI' S'!UDY IN EAST LOOI,PEARL HARBOR, HAWAI' I
Yu-Si Fok
Edwin T. Murabayashi
Technical MemorandlDll Report No. 76
JUly 1984
Final Technical Completion Report
for
Pilot Study of Flexible Membrane Irrpmndmentof Stream Water in a Coastal Embayment
BWS Contract No. 003924
Project Period: 1 February 1983-31 January 1984
Principal Investigator: Yu-Si Fok
The work on which this report is based was supported in p:lrt by fundsprovided by the City and County of Honolulu Board of Water Supply,Hawaii State Dep:lrtment of Land and Natural Resources, and the University of Hawaii at Manoa Water Resources Research center, Honolulu,Hawaii.
WATER RESOURCFS RESEAROI CENTERUniversity of Hawaii at Manoa
2540 Dole StreetHonolulu, Hawaii 96822
v
ABSTRAC1'
Pilot field tests were conducted in the continuing conceptual develop
ment of using impermeable membranes as separating liners to store fresh
stream water in an embayment. The storage of fresh water in the ocean wasconceived as a less expensive way of storing surplus stream water for sub
sequent use than in land-based rigid darns and reservoirs.
Three basic types of membrane storage enclosures were tested: float
ing reservoir, bag, and curtain. Each has its partiCUlar advantages and
disadvantages which determine their suitability to any particular applica
tion. The testing took place in East Loch of Pearl Harbor, a protected
inland estuarine embayment, to capture the freshwater flow from Kalauao
Springs near Pearlridge on O'ahu, Hawai' i.
The tidal effect, partiCUlarly low tide, has a significant effect on
the enclosures. On the curtain, the effect was the amount of slack needed
to retain the water captured at high tide as the tide recedes. With the
open reservoir and bag, low tide left the enclosure grounded and unsupport
ed on the muddy bottom. A site needs sufficient water depth to keep the
enclosures afloat at all times. A rotating collar would prevent the bag
and open reservoir from becoming twisted around an anchor point.
A membrane floating canal and pipeline for water transmission on the
ocean surface were also developed and tested successfully.
In all testing, 6-mil polyethylene film was used as the membrane dur
ing this proof-of-concept stage. Sufficient progress has now been attained
that in the next stage a first priority effort should be the selection of a
suitable operational quality nenbrane.
No adverse environmental impacts were detected during or after the
pilot study.
vii
FABRICATION • • • • • •
Curtain. • • • • •
Desirable Site Characteristics •
Bag. . • •..••
1
3
3
3
11
13
15
16
. . . .. . . .
Study Site Description •
Floating Reservoir •
INIroDUCl'ION. • • •
PILar S'!UDY SITE.
DEPLOYMENT AND TESTIN3.
. . . . . . . . . .
Curtain••••••
Bag and Floating Reservoir •
Floating Canal and Floating Pipe •
ENVIRONMENTAL IMPACT.
.. . . . . . . . . .
16
16
31
34
39
SUMMARY, OONCLUSIONS, AND REOOMMENl)ATIONS •
REFERENCES. • • •
40
41
42
Figures
1. Location of Membrane Storage Study Site, East Loch 4
2. Close-up of Study Site Location at Mouth ofKalauao Springs Drainage into East Loch. • • . . . . . . . . . 4
3. View of Stream Mouth from seaward Side of Bridgeat Nearly Low Tide • • • • • • • • • • • • • • •
4. Close-up of Bridge Abutments to Which Curtain was Tied
5
5
5. Effect of Low and High Tides on Streamflow at Study Site • 7
6. Ski.nming Mechanism for Intake of Fresh Stream WaterNear Surface • • • • • • • • • • • • • • • • • . . . . . . . 7
7. Up3trearn View from Bridge at High Tide ShooingCaliforniagrass-covered Banks. • • • • • • • • 8
8. Flat, Muddy Harbor Bottom at Low Tide Shooing MiredTire That is Completely Covered at High Tide • • • • . . . . . . . 8
viii
9. Bridge Abutment at Low Tide••
10. Bridge Abutment at High Tide.
. . . . 9
9
11. Large Naval Vessel in Deep water OlannelRelative to study Site ••••••••• • • • . • 10
12. . . . . . .
12. Heat-Seaming Polyethylene Sheets Together using Teflon-Sheathed Clothes Iron in Fabricating the Curtain • • • .• • •• 12
13. Adjusting Temperature of Clothes Iron in Preparationfor Einbedding and Sealing Rope Along Border of Bag •
14. sand-Filled Tubes Used for Curtain Anchorage BeingLoaded onto Rafts for Deployment • • • • • • • • • · . • .• 14
17
15. Flotation System of Standard Foam Rubber Pipe InsulationStrung Together with Parachute Strap MoOring Line. • • • • • • •• 14
16. Fabrication of an Inlet Tube for Subsequent Attachmentto the Main Body of a Floating Reservoir • • • • • • • • • • • •• 17
17. Joining Ropes Before Sheathing it in Membrane Alongthe Border of a Bag•••••••••••••••••
18. Curtain Unloaded on Jogging Path that Crosses BridgeBelow Which Stream Flows into East Loch•••••••• • 19
19. Unrolling of 200 ft Long x 18 ft Wide Curtain securedto Mangrove Tree to Prevent Drifting • • • • • • • • • • • • • •• 19
21. String of floats Prior to Insertion into Curtain Sleeves.
20. Unrolled, Spread Out Curtain Showing Fabricated Sleeveson Both Edges Prior to Insertion of Floats • • • • • • • · . . 20
20
22. 'lWo Strings of Floats Being Pulled Simultaneously intoEach Manbrane Sleeve • • • • • • • • • • • • • • • • • · . 21
23. Currents and Wind Constantly Shifted Membrane and Floats,Making it Difficult to Keep Components Together•••••• 21
24. SChematic Layout of Curtain Location and Configurationand Eight sampling Sites • • • • • • • • • • • •
25. Partially in Place Curtain Prior to Placement ofsand-Tube Anchors. • • • • • • • • • • • • • • •
· . . . . .· . . . ...
22
23
26. Anchoring sand-Tube Ballast Being Placed Along CenterLine of Curtain. • • • • • • • • • • • • • • • • • · . . . . . 23
27. Person on Mart>rane Errplacing and stepping on sandBallast Tubes to Push Tubes and Membrane into SoftMuddy Harbor Bottom. •• .• • • • • • • • • • • • • • • • • • • •• 24
28. Canpleted Curtain Deployment ••••
29. Completed Curtain Enclosure in Place •
ix
24
25
30. Both Ends of Curtain Tied to Bridge Abutments; ExcessStream Water Escapes Through '1Wo Unobstructed OpeningsBetween Curtain and Abutment • • • • • • • • • • • • • 25
31. Approximate Deflection of Curtain from High to Low Tideat the Proposed Location of Prototype Membrane, Pearl Harbor 29
32. Bag Being Unrolled for Deployment, While Open InletTube is Held at Bridge Where Intake Will Take Place. • • • • • •• 31
33. Skinming Intake Opening Used for Filling Bag andFloating Reservoir • • • • • • • • • • • • • • • 32
34. Floating Reservoir and Bag Being Filled Through Inlet Tubes. • 32
35. Fully Filled Floating Reservoir.
36. Fully Filled Bag • • • • • • •
37. Floating Canal at High Tide.
38. Floating Canal at Low Tide ••
39. Streamwater Spilling Out of Floating Canal Unsupportedby Seawater at Low Tide. • • • • • • • • • • • • • •
40. Floating Pipe at High Tide During Initial Filling. •
41. Floating Pipe at Low Tide••••••••••••••
33
33
36
• • •• 37
37
38
38
42. Wood-Framed Floating Pipe Intake Designed to Skim StreamWater Floating on Denser Seawater. • • • • • • • • • • • • • • •• 39
Tables
1. Advantages and Disadvantages of Curtain,Floating Membrane, and Bag Enclosures••
2. Salinity Readings at the Curtain Enclosures.
2
26
IN1'OODUCl'ION
Pilot field tests were conducted in the continuing conceptual develop
ment of using impermeable membranes as separating liners to store fresh
stream water in an anbayment. The storage of fresh water in the ocean was
conceived as a less expensive way of storing surplus stream water for sub
sequent use than in land-based rigid dams and reservoirs. The membrane it
self does not need the structural strength of rigid conventional reservoirs
because the pressure on both sides of the merrbrane is in dynamic equilib
rium at all points and all depths.
The concepts, principles, and initial research efforts which included
laboratory hydraulic models as well as preliminary short-term field trials
is detailed in an earlier report by Murabayashi and Fok (19B3). For this
study the concept is developed further toward operational application by
exPanding on the knowledge gained in the earlier short-term trials through
longer field testing periods and by using larger capacity prototypes.
Three basic types of membrane enclosures field tested on a pilot scale
are a floating reservoir, bag, and curtain, as shown below. The floating
. - F I00 t 5 - ___
'-."
FLOATINGRESE RVOIR
SEAWATER
BAG
reservoir is essentially a hemisphere with floats around its perimeter.
The bag is simply that, a bag corrpletely enclosing the captured water. And
the curtain can be likened to a membrane dam, separating the captured fresh
water from the ocean.
The advantages and disadvantages of the three enclosures (Table l) de
termine their appropriateness to any particular application. Although
Murabayashi and Fok (19B3) identified the curtain as the method most physi
cally suited for the West Loch site should an operational deployment take
TABLE 1. NNPNrNlsES AND DlSADVPNrNlsES OF aJRI'IAN, FLOATIl'G MEMBRANE, AND BAG :rna..osuRES tv
Enclosure Type
Curtain
Floating Reservoir
Bag
Advantages
Best suited for catchment of storm runoffcaptures water from diffused (nonpoint)
inlets (submarine springs within reservoir area)
Stores large volume of waterOpen surface provides catchment for rain
fallNo stress placed on membrane since within
another water bodyCan be readily ranoved if need arisesSingle curtain feature requires small
amount of membraneSeparates fresh water from seawaterEasily captures and stores rainfallRequires moderate amount of membrane
because of OPen topVery little environmental i.rrq;>act
Easiest to prefabricate, deploy, andmaintain in field
No evaporation lossNo wave overtopping problemscanplete separation of fresh water from
seawaterVery little of membrane exposed to
weatheringBuoyancy controlled by leaving small
amount of air in bag to prevent dragging on sea bottom and to compensatefor sediment in stored water
Disadvantages
catchment water cannot be completelypumped out as in rigid dam
Waves may overtop float systemMean net annual evaporation loss in Pearl
Harbor area 782.3 rom (30.8 in.)Fresh water floating on sea water evapo
rates first and seawater entrappedbelow reduces freshwater storage
Surface parts subject to weathering andweathering degradation
Cumbersome field preparation of attachingfloats and ballast to curtain
Stored water subject to evaporation lossSurface parts subject to weatheringOVertopping waves could mix with stored
waterAroount of stored water limited by size
and number of reservoirsCumbersome field preparation of attaching
floats to curtains
Larger amount of membrane needed thanother types because water fully encases
Aroount of water stored is limited by sizeand number of bags
Only debris-free water can be stored toprevent puncturing of membrane
Underwater snags and obstacles might ripthe bay
3
place, all three methods were tested in this study. Since this subject is
relatively new, additional suggested references include Fok and Murabayashi
(1980), Fok and Murabayashi <1981>, Fok (1983), and Murabayashi and Fok(1984).
Most of the materials presented is a photographic docurnentationof the
operation as the major effort was concentrated in field work.
PIIDI' STODY SITE
Desirable Site Characteristics
Desirable characteristics of a pilot study site were identified as
follows.
1. The stream size should be snaIl enough to allow Equipnent deploy
ment and handling with only manpower and no machinery, yet large
enough to demonstrate the study concept.
2. The anbaYrnent should be relatively free of obstacles such as
rocks, structures, trees, and boat traffic. The water depth
should not be too deep (not roore than 4 ft [1.2 m]) for safety in
deployment and should have a snooth bottom.
3. The location should be accessible by car to facilitate transporta
tion of materials and personnel.
4. Permission for conducting the pilot study should be obtainable
with little or no commitment of funds.
5. The site should not pose any danger to working personnel and by
standers. A public telephone should be located nearby should any
emergencies occur.
The study site selected met these criteria, except for being too
shallow at low tide as became evident during the testing.
study Site Description
The test site is located at the mouth of Kalauao Springs as it enters
East Loch of Pearl Harbor (Figs. 1, 2). .This is at the Loch's northwestern
boundary, directly downstream from the spring's source at Sumida's water
cress farm adjoining the Pearlridge Shopping center. Just as it dis
charges into East Loch, the stream flows under a snall jogging path bridge
(Figs. 3, 4). The bridge's concrete abutment constricts and controls the
/./
'.,- ...r"
.. ,..... ...-""""r'"
/
"'/l .. (
~/l ..J,..STR..../1';-'" "''',....... ,
"'-'" ..".-- ...",/
..j/.
ir'o"
\)
/'
157°56'
KalouaoSpring?
3000 It, i
2000,
EAST LOCH
1000!
Waiau
PEARL HARBOR
oI
4
210 0 1000 m 210n' L...---------------------1-57...l.-S"""6'--.....L--..'-------....:...-------122'
Figure 1. Location of membrane storage study site, East Loch, Pearl Harbor
PearlridgeShopping Center
PILOT STUDYSITE
//,,
II
I,I\ ,, /, /" ,
" "................... ---,,'"400 It
Figure 2. Close-up of study site location at mouth of KalauaoSprings drainage into East Loch, Pearl Harbor
Figure 3. View of stream IOOuth from seaward side of bridgeat nearly low tide. Algal growth narks hightide level on bridge abutments; renmants ofexperimental floating membrane canal in foreground.
Figure 4. Close-up of bridge abutments to which curtainwas tied. Raft is used to transport naterialsand is towed by hand. Tubular naterials arefloats sheathed in membrane sleeves describedin Fabrication section; remainder of membraneextends underwater.
5
6
flow to a point source discharge, thereby greatly enhancing its manage
ability in the experiment as opposed to having the flow diffused through a
mangrove-overgrown delta which is more cormnon through this area. The
bridge also serves as a reference point in that it represents the stream
mouth where the curtain was attached to capture the streamflow and filling
of the floating reservoir and bag took place.
The gradient upstream from the bridge is flat and at the same eleva
tion as the harbor for about 300 ft (91 m); therefore, the water level in
the stream rises and falls with the harbor tides. This produces an estua
rine extension of the harbor up into the stream, which had an effect on
portions of the testing. As shown in Figure 5, the streambed is exposed at
maximum low tide, and the entire flow is essentially fresh water. At high
tide and intermediate stages, however, the uppermost water layer is fresh
water flowing downstream, below which is salt water extending upstream from
the harbor. This horizontal fresh and seawater stratification effectively
permits skimning of the fresh water into bags and open reservoir--even
though the intake is at sea level--rather than being caught before the
stream water comes in contact with the ocean. A skinming intake mechanism
at the bridge abutment is shown in Figure 6. Another effect in the case of
the curtain is that its deployment in the harbor would block the seawater
from moving upstream, thereby changing it from an estuary.
The muddy streambank is overgrown with Californiagrass which forms
floating mats along wider portions of the stream (Fig. 7), but there is
OPen water in the channel itself. The stream water is relatively clean as
compared to the muddy ocean but is by no means pr istine. There are rusty,
algae-covered automobile parts as well as miscellaneous cans and rocks in
the stream at the bridge. The water appear unsavory and polluted. Tilapia
and other fishes were d:>served in the stream and under the bridge.
On the seaward side of the shore where the rnent>ranes were deployed,
the nearly flat muddy harbor bottom (Fig. 8) is relatively shallow and is
exposed for about 150 ft (45.7 m) seaward at low tide and about 2 ft
(0.6 m) deep at high tide. A comparison of tidal change is shown in Fig
ures 9 and 10. A deeper channel at the mouth of the stream was probably
gouged by torrential storm waters disgorged through the bridge. This
channel is about 4 ft (1 m) deep at the bridge and becomes gradually
shallower, extending about 100 ft (30 m) offshore where it meets the same
7
LOW TIDE
Seawater
HIGH TIDE
Cross Section
Figure 5. Effect of low and high tides on streamflow at study site.At low tide stream flows on bottom of bed; at high tide,lighter fresh stream water floats on top of heavier seawater. The actual freslMater flow appears larger than itactually is because of the underlying seawater.
Figure 6. Skinming mechanism for intake of fresh streamwater near surface without taking in seawaterbelow. Intake consists of rectangular woodenframe onto which intake tube is attached.
8
Figure 7. Upstream view from bridge at high tide showingcaliforniagrass-covered banks. Surface flowis stream water underlain by strata of harborseawater.
Figure 8. Flat, muddy harbor bottom at low tide showingmired tire that is completely covered at hightide. Water in foreground and center is streamflow from under the bridge at left; membranestructure from lower left to upper right is experimental floating canal which conveys freshwater at ocean surface.
Figure 9.Bridge abutment at low tide
9
Figure 10. Bridge abutment at high tide
10
Figure 11. Large naval vessel in deep water channelrelative to study site
depth as the surrounding bottom.
The U.S. Navy's deep, navigable dredged channel is about 900 ft
(274 m) offshore. The project site did not extend into these waters
(Fig. 11).
Normal wind direction during trades is directly offshore and was not
unUSUally strong. No storms occurred during the investigative period.
Waves were usually small and undulating with no whitecaps. These were
mainly generated by ships p:lssing in the harbor channel, since the normal
winds from offshore would not have had sufficient expanse of open water
from shore to develop waves of any consequence within the test area.
There is a multiplicity of jurisdiction and a need to obtain permits
from each before testing could begin. East Loch is under U.S. Navy juris
diction; the coastal area of East Loch is within the Hawaii State conser
vation zone for which the Hawaii State Dep:lrtment of Land and Natural
Resources has regulatory and protection responsibility; and the jogging
path which is the only road for transporting materials to the site is under
the City and County of Honolulu Parks and Recreation jurisdiction. The
U.S. Army Corps of Engineers is responsible for navigable waterways that
also cover the general area of the pilot study site. Permission to conduct
11
the pilot study at this site had to be obtained from the above goverrnnental
agencies. Because of the temporary nature of the study, an envirornnental
impact statement was not required. Pertinent permits and related documents
are included in Appendix A.
FABRICATION
The design, naterials used, and fabrication of the membrane structures
were essentially similar to that develoPed earlier by Murabayashi and Fok
(1983). A prototype curtain, floating reservoir, and bag were fabricated
for field testing. Figures 4 to 9 show some aSPeCts of the fabrication.
The membrane used in fabrication consisted of 6 mil thick black poly
ethylene film which are obtainable in standard sheets of 20 x 100 ft (6.1 x
30.5 rn). Polyethylene was selected because while not having all the attri
butes of an ideal naterial, it does have the distinct advantages of being
rffidily available locally in large sheets which greatly facilitate the fab
rication of the large membrane structures, as well as being lightweight for
handling ease without machinery and enviromnentally nontoxic.
Heat-seaming is the only means of joining polyethylene sheets; there
is no glue that adheres to it. The desired joint (seam) is placed over an
aluminurn sheet, then pressed with a teflon-sheathed clothes iron. Inme
diately after the desired melt is attained, the seam is cooled with a damp
cloth to stabilize the polyethylene, thereby preventing wrinkling, and
producing a strong, smooth, watertight joint. Figures 12 and 13 illustrate
the heat-seaming operation.
12
Figure 12.Heat-seaming polyethylene sheetstogether using a teflon-sheathedclothes iron in fabricating thecurtain
Figure 13. Adjusting temperature of clothes iron inpreparation for anbedding and sealing ropealong border of bag
13
CUrtain
The curtain method requires flotation, mooring, and anchorage systems
to position the membrane. For ease of field deployment a U-shaped (in
cross section), double-membrane design was adopted, as shown below.
/Floats~
MiddleComportment
1~_----1--Membrane
AnchorBallast
u-shaped cross section
The anchoring system seals the curtain to the bottom of the bay and
side-slopes. Such a system should minimize seepage under the membrane and
be strong enough to remain imnobile when subjected to mrrnal ocean move
ments. A flexible weight system which conforms to uneven bottoms is neces
sary and locations with steep side-slopes should be avoided or modified to
make it less sloping.
The anchoring ballast consisted of sand-filled 4 in. (0.1 m) diameter
cylindrical polyethylene tubes in 2 to 3 ft (0.6-0.9 m) lengths weighing
8 Ib/ft <3.6 kg/m) laid end to end (Fig. 14). This simple technique
allowed easy placement of the ballast after the rnent:>rane had been deployed
on the water, and met the need for even anchor distr ibution to effect
bottom sealing. The U-shaped curtain allows placement of additional
ballast if the need arises. The alternative of preassembling the anchor
with the curtain makes the whole unit very heavy, and attaching anchors
while deploying the membrane is very cLmlbersorne in the field •. The U-shaped
method also gives double-membrane separation of the two water bodies.
The flotation system consisted of standard 4 in. (0.1 m) diameter
x 6 ft (1.8 m) long foam rubber pipe insulation. The insulation was
strung together with a nylon parachute strap pulled through the center hole
(Fig. 15). This was placed in a membrane sleeve formed at the edge of the
membrane as shown below. The membrane sleeve through which the float
14
Figure 14. Sand-filled tubes used for curtain anchoragebeing loaded onto rafts for deployment
Figure 15. Flotation system of standard foam rubber pipeinsulation strung together with parachute strapmooring line
.~-- Foam Rubber Float
Mooring Line
--+--- Sleeve
Curtain Membrane
]
COMBINED FLOTATIONAND MOORING SYSTEM
15
pa~ses is made sufficiently large to allow additional strings of floats to
be added if necessary.
The foam rubber pipe insulation makes an ideal float because (1) it
has good buoyancy and Ooes not waterlog easily; (2) the circular shape dis
tributes the load evenly on the membrane, whereas square corners will tend
to cut through; (3) the softness and flexibility throughout its length
allows easy bending without stress IX>ints where they are joined, whereas
with rigid floats, the membrane tends to wear out where the floats are con
nected because this is the only IX>int where flexing can take place; (4) the
center hole allows the floats to be strung together by pulling a line
through it, thereby corrt>ining the flotation and mooring control system; and
(5) the insulation is light and easy to handle.
The parachute strap used for the mooring system also strengthens the
floating edge of the curtain. With both ends moored to the shore, the
strap holds the curtain in place. The parachute strap used was soft and
pliable, thereby resisting any tendency to cut into the foam rubber. The
double-sheet curtain extends vertically 10 ft (3.05 m) and horizontally
200 ft (61 m) •
Floating Reservoir
The floating reservoir is a flat IX>lyethylene sheet with its edges
gathered to a smaller perimeter, thereby forming a catclunent basin. A 40 x
50 ft (12.2 x 15.2 m) sheet with a float perimeter of 100 ft (30.48 m) was
fabricated providing a 15,000-gal (S6.8-m3 ) capacity when filled. The flo
tation system is similar to that of the curtain. Sleeves were seamed into
each edge but the corners left open to allow the floats to be more readily
16
pulled through. The corners were then pinned in place over the float to
provide a watertight seal.
To fill the reservoir a 3-ft <O.9l-rn) diameter by 100 ft long tube
similar to that used on the bag is seamed into the main body just below the
flotation system. The tube is reinforced with rope around its inlet and
two sides of its length and ties into the flotation system of the main
body. Fabrication of an inlet tube prior to attaching onto the main body
is shown in Figure 16.
Bag
Flat membrane sheets seamed at the edges form the bottle-shaped bag.
The bag edges were reinforced with 3/8 in. (9.55 mn) polypropylene rope
embedded with the menbrane as shown below and being fabricated in Fig
ures 16 and 17.
Membrane
Rope
i~::e~r~ed --l'- B_A_G >----~:Cxtra Rope'-Inlet
Tube
Final Irodel--Plan view
This allows the load to be evenly distributed along the rope. The final
design of the bottle-shaped bag is 20 ft (6.1 rn) wide and 100 ft (30.48 rn)
long. Its maximum capacity is 2000 ft3 (56.6 rn3 ) •
DEPLOYMENT AND TESTIOO
CUrtain
The curtain was unloaded at the project site (Fig. 18), hand carried
to the water, and rolled out and spread on the surface to allow the inser
tion of the floats. The curtain floats while this is being done because of
17
Figure 16.Fabrication of an inlet tubefor subsequent attachment tothe main body of a floatingreservoir
ll.:
Figure 17. Joining ropes before sheathing it in membranealong the border of a bag
18
its near neutral buoyancy coupled with air trapped between the curtain and
the water. Two strings of the foam rubber float-IOOOring lines were in
serted into each sleeve. Float insertion is a cumbersome operation that
requires the full use of all the manpower. This phase of the operation is
shown in Figures 19 to 23.
The curtain is subsequently aligned in its desired configuration to
enable catchment of the stream outflow (Fig. 24.) Flexibility inherent in
the curtain method allowed the selection of a deployment aligrunent, which
included a mangrove tree within the enclosure, without compromising its
structural integrity of a water body as shown in Figure 25.
To facilitate laying of the ballast, the inner edge of floats (the
edge closest to the stream mouth) is tied in place at the bridge abutment,
thus somewhat spreading out the curtain. After this, two rows of sand-tube
ballast, providing about 16 lb (7.3 kg) anchorage per lineal feet, was
placed on the center line of the curtain as it floated (Figs. 26, 27). A
worker then steps on the ballast to push it and the curtain down into the
water and further into the soft muddy bottom about 4 in. (0.1 m). This
trenching helped to seal the curtain to the bottom and also reduced the
possibility of having it dragged along the bottom.
The loose edge of floats was subsequently tied to the bridge abutment
in aligrunent with the other edge to effect the completion of the deployment
(Figs. 28, 29). Excess water from the stream inflow was allowed to escape
through openings left on the ends where the curtain was tied to the bridge
abutment, as diagrammed in Figure 24 and shown in Figure 30.
When the curtain method is used, the water on both sides is initially
salty; however, the seawater within the enclosure is subsequently diluted
by the freshwater inflow. salinity readings, using a hand-held refractom
eter, were taken to measure dilution. Figure 24 shows the location of each
salinity measuring station. At stations 1 and 8, upstream from the bridge,
salinity measurenents of the stream inflow were taken at the surface before
it enters the enclosure. Stations 2 to 7 are located within the curtain,
and station 9 is located outside the enclosure to provide a seawater salin
ity reference point. The salinity readings at each station during the
13 days of the run are presented in Table 2. Both surface and bottom read
ings were taken at most stations because of possible vertical stratifica~
tions.
Figure 18. Curtain unloaded on jogging path that crossesbridge below which stream flows into East Loch(right)
Figure 19. Unrolling of 200 ft long x 18 ft wide curtainsecured to mangrove tree (left) to preventdrifting
19
20
Figure 20. Unrolled, spread out curtain shCMing fabricatedsleeves on both edges prior to insertion offloats
Figure 21. String of floats prior to insertion intocurtain sleeves
Figure 22. '!Wo strings of floats being pulled simultaneously into each rnent:>rane sleeve
Figure 23. Currents and wind constantly shifted menbraneand floats, making it difficult to keep cornponents together
21
EAST LOCH
22
@•
Outflow ofexcess water~ -
JOGGING/BIKEPATH
BRIDGE
Mangrove
@ •
..... Outflow of....... excess water
JOGGING/BIKEPATH
• <D
~~>..
•®..
Stream
Figure 24. Schematic layout of curtain location andconfiguration and eight sampling sites
Figure 25. Partially in place curtain prior toplacement of sand-tube anchors
Figure 26. Anchoring sand-tube ballast being placedalong center line of curtain
23
24
Figure 27. Person on membrane anplacing and stepping onsand ballast tubes to push tubes and membraneinto soft muddy harbor bottom
Figure 28.Cooq;>leted curtain deployment
25
Figure 29. Corrpleted curtain enclosure in place
Figure 30.Both ends of curtain tied tobridge abubnentsi excessstream water escapes throughtwo unobstructed oPeningsbetween curtain and abubnent
TABLE 2. SALINITY READIN;S AT 'lHE aJRTAIN ENCLOSURES
UPSTREAM WI'IHIN ENa.oSURE OUTSIDE UPSTR~ KAMSl'ATION 1 8 2 3 4 5 6 7 9 mY BRIOOE
Dav 1983 Time Tide S B S B S B S B S B S B S B S B S B S B
1 8/19 1320 High 6 - 6 - 6 16 9 36 6 32 6 24 7 28 6 - 34 36
2 8/20 1015 Low 4 - 4 - 2 2 2 3 3 4 4 4 4 4 4 - 24 35
3 8/21 1010 Low 4 - 4 - 2 2 2 2 3 3 4 5 3 4 4 - 28 29
4 8/22 1345 High 5 - 5 - 3 5 4 32 6 26 5 10 5 12 5 - 32 32
5 8/23 1245 Mid 1 - 2 - 2 2 2 29 2 7 3 3 3 3 2 - 32 34 2 -
6 8/24 1200 LCM 4 - 3 - 4 4 4 5 4 6 4 6 4 6 4 - 28 32 3 -7 8/25 1215 Low 3 - 3 - 4 4 3 4 3 3 2 4 2 2 3 - 33 33 2
8 8/26 0845 High 2 - 2 - 3 3 2 2 2 4 2 2 4 2 2 - 30 35 2 -9t 8/27 1105 Mid 1 - 0 - 1 1 1.5 1.5 1 2 2 2 2 2 2 - 28 35 0 -
lot 8/28 1255 LOll 0 - 0 - 1 1 1 1 0 1 1 1 1 1 1 - 34 35 0 0
lIt 8/29 1605 HIGH 0 - 0 - 1 1 0.5 1 1 1 1.5 1.5 1 1 0 - 35 36 -13t 9/01 0930 Mid 5 - 5 - 414 6 22 3 13 2 18 1 10 1 - 35 37
NJTE: S = surface sanq;>le, B = bottan sample; measurements in parts per thousand for salinity readings.roTE: Tear in curtain discovered on day 10 (8128).*Elevation above sea level; no possible contact with seawater.tNew salinometer used.
N
'"
27
The highest salinities were recorded on the first day as would be ex
pected since the seawater had not been diluted to any great extent. By the
second day sufficient inflCM would have occurred, thus, conpletely removing
the seawater, as reflected in the readings. Because the water depth is
relatively shallow, it is unlikely that vertical stratification remained,
although the higher bottom readings on day 4 are unexplainable. It is
worth noting how low the salinity is overall within the enclosure as com
pared to the outside at station 9, as well as how close the enclosure water
is to the inflow water at stations 1 and 8. The curtain is evidently very
successful in separating the seawater from the stream water. In this ex
periment, the relatively large stream inflow into a relatively small enclo
sure could have placed an overriding advantage on the freshwater side.
On day 10 a tear from top to bottom was discovered at mid-length of
the curtain. The break was of sufficient magnitude to definitely compro
mise the curtain' sability to keep the waters separated by allowing the
heavier seawater to flow in beneath the fresher surface water within the
enclosure and the fresh water to escape out to sea. Nevertheless, the
readings thereafter indicate that salinity did not increase within the
enclosure even at depth.
Although initially attributed to vandalism, the tear in the curtain
was subsequently deduced as being probably related to tidal ebbing in the
following sequence. As the tide ebbs, support wanes on the outside of the
curtain, but the inside is still full of water because of the continuous
streamflow. The water inside the enclosure can neither overtop the cur
tain because of the high buoyancy of the floats nor escape from the bottom
because the curtain is well sealed by the anchoring sand tubes. Conse
quently, as the tide gradUally ebbs, at some IX>int a tear occurs in the
membrane which is the weakest component. A close examination of the break
indicated that it follCMed the edge of a seam where two sheets had been
joined. Evidently during the heat seaming process, the edge may have been
stretched thin while soft or otherwise weakened. The seam itself was sound
because of its double thickness. Also, coincidentally or not, in the model
studies by Murabayashi and Fok (1983), overtopping occurred at mid-length
of the curtain when the outside water was lowered to simulate low tide. In
that test the ment>rane was much too strong to be ripPed by the shallow
depths involved.
28
The adverse effects of tides has been amply demonstrated in this pilot
study in a way that could not have been fUlly anticipated in the previous
laboratory roodeling (Murabayashi and Fok 1983) because of the 1:1 scale
involved in this phase. These observations of tidal effects on the curtain
can be used in analyzing its consequences on the prop:>sed west Loch water
storage project. The issue has to do with the amount of curtain slack
needed to contain the water within the enclosure as the tide drops from
high to low tide. The curtain requires slack to contain the water as the
tide ebbs as shown below. Obviously, volume A has to equal volt.m\e B, only
Low Tide
High Tide
VOLUME A
Cross Section
it has been displaced to the low tide level. The prop:>sed west Loch cur
tain reservoir site has about 277 acres Cl.2l x 106 m2 ) of water surface
(Fig. 31). Thus, when the tide ebbs with an average tidal height differ
ence of 1.5 ft (0.5 m), 415.5 acre-ft (5.12 x 10 5 m3 ) or 18,099,180 ft 3
(5.1 x 105 m3 ) of water moves from volt.m\e A to B. With a curtain length of
3500 ft Cl 066.8 m) and assuming a mean depth of 10 ft 0.05 m) at low
tide, the slack would have to be 1034 ft 015.16 m) long as shown below.
b Water Surface
Slack
s
J-f--- 3500 ft curtainlength
18,099,180-ft 3
volume
29
NAVAL RESERVATION
Pt.
LOCH
WAIPAHU
'OOOm
) ,3000 It
WEST
2000,I
500
,,,/> /
\/"-,0'" /" c.'/ ,e. ";'<.~e\,ot. I
. ,/ (0 0'". , / / ~~~ C>' v /
'~ /\ "V" 0···
Lauiaunul Is. OJ /NAVAL RES FISHPOND
IIII
'000
HONOULIULI
o
21°22'
OOURCE: Murabayashi and Fok (1983).
Figure 31. Approximate deflection of curtain fran high to low tide atproposed location of prototype membrane, Pearl Harbor
30
To solve the slack, S,
volume = area· length
Sh18,099,180 =2'" . 3500
b = 2 • 18,099,1803500 • 10
b = 1034 ft
and by the Pythagorean theorem,
S2 = h2 + b 2
S = l(h2 + S2)
= 1(102 + 10342)
slack S = 1034 ft, the samelength as base b
area of curtain = S • L
1034 • 3500
area of curtain = 3,619,000 ft2 •
Obviously the 1034 ft length of slack and the 3,619,000 ft 2 of membrane
needed for it is quite large. Additional slack is needed to capture and to
store runoff and streamflow, which is the primary purpose of the curtain.
Since tidal volume change is directly related to surface area, a narrow and
deep water body will have less need for tidal slack in its ment>rane thari
for a similar volume of water contained in a wide and shallow body such as
West Loch. Thus, a question arises regarding the viability of using the
curtain in West Loch.
To alleviate the tidal effect on the curtain membrane structure in
West Loch, several schemes can be considered:
1. Develop a movable curtain membrane structure that is weighted but
not anchored at the bottom to enable the movement of the curtain
with the rise and fall of the tide, which results in considerably
decreasing the required length of slack to 25 - 30 ft (7.6 ~ 9.1 rn)
2. Use several anchored membrane structures spaced parallel to the
axis of the membrane curtain so that the length of the slack of
each curtain structure is shortened to a manageable length, thus
providing better storage security of Waikele Stream waters
3. Compartmentalize the freshwater storage pool in West Loch by using
membrane bags or floating membrane reservoirs which float with the
tide and thus sustain minimal tidal effect.
A combination of schemes 1, 2, and 3 can consolidate their advantages to
31
alleviate tidal effects on the membrane structures in West Loch.
The tide has a positive effect in that it can quickly purge seawater
from the enclosure after deployment by allowing the seawater to escape
through one-way valves as the tide recedes.
Bag and Floating Reservoir
The bag and floating reservoir will be discussed together because of
their similarity in deployment, although the bag is easier to use because
it does not require the insertion of floats. Both were deployed on the
same day, one after the other.
The rolled-up bag and floating reservoir were unloaded from the truck,
placed in the water, and unrolled as shown in Figure 32. As in the cur
tain, the membrane floats because of the polyethylene's near neutral buoy
ancy, as well as the snaIl amount of air trapped within its folds. In the
case of the floating reservoir, the floats are inserted and secured at this
point. The mouth of the inlet tube is then tied to the bridge abutment so
that the freshwater outflow from the stream is skinmed from the surface
without catching the deeper salty water, as shown in Figure 33. Figures 34
to 36 show stages of filling the floating reservoir and the bag.
Figure 32. Bag being unrolled for deployment, while openinlet tube is held at bridge where intake willtake place
32
Figure 33. Skinming intake opening used for filling bagand floating reservoir. A piece of foam rubberpipe insulation is used to prop open the inletwhich also keeps it afloat for skinming and tworopes keep it in place.
Figure 34. Floating reservoir and bag being filled throughinlet tubes
Figure 35. Fully filled floating reservoir
Figure 36. Fully filled bag. Workers in air inflatedraft are skirrming over the bag withoutdarnaging the merrt>rane
33
34
SUbs~uent to fillin;J, the bag and open reservoir were hand towed
about 300 ft (91 m) and both tied to a anall isolated mangrove tree about
150 ft (46 m) offshore to discourage vandalism while simulatin;J storage.
All filling, towing, and securing operations went very smoothly.
The following day, the bag and the floating reservoir were plrtially
awash and twisted around the mangrove tree. The initial thought was that
vandals had slashed the membrane, but on closer examination it became
evident that only the bag had ripped. As in the curtain, this had occurred
either at an edge of a seam where sheets were joined, or at a fold in the
menbrane as it came from the manufacturer. The bag on the other hand seems
to have simply deflated and let out most of the fresh water. No damage to
the 1llE!'lt>rane was evident.
As in the case with the curtain, what probably ha~ed was that a low
tide during the interim period left the bag and open reservoir unsupported
and exposed on the mud flat. The bag ripped because the water could not
escape and the floating reservoir simply collapsed allowing the captured
water to flow out over the floats. Sub~uent to this, wind and current
movement further entwined the structures when the tide rose. Both struc
tures were left in place and observed over the next two weeks, durin;J which
they continued to deteriorate as natural factors took their toll.
The bag and the open reservoir had twisted themselves around the man
grove tree. Thus, it is imperative that they be tethered so that they can
turn easily without becoming entwined, such as to a buoy with a free
turning collar.
The experiment was not repeated with new bag~ and floating reservoirs
because no secure place was available to anchor them in deeper water. The
risk could not be taken of havin;J the structures break free and drift into
the navigable ship channels. Also, driving a stake into the bottom to
serve as an anchor was not considered sufficiently secure given the size of
the bag and open reservoir.
Floating Canal and Floating Pipe
FI..OA.TIro CANAL. At the conclusion of the curtail) experiment, it be
came obvious that another completely different use could be made of the
membrane before its distx>sal. And that was to ranove the sand tube anchor,
thereby transforming it into a floating canal for transtx>rting flowing
35
fresh water on the ocean surface as shown belOlrl.
Curtain membranewith sand tubesremoved
-.... ................
Floating canal
The intake end was tied to the bridge abubnent and stiffened with wood at
its leading edge to preclude its collapse as the water flOlrled into the
canal.The canal worked very well at high tide during the two weeks that is
was deployed (Fig. 37). The only problsn that arose was that at 10lrl tide,
the ocean water receded leaving the canal lUlsupported on the nuddy bottan.
This caused water to flOlrl out over the side (Figs. 38, 39). The usable
length was 100 ft (30.5 m> because of the tear in the middle of the origi
nal 200-ft (6l-m> curtain. The offshore end was anchored with sand bags to
prevent it from wavering with the currents.
This method is obviously meant for water transmission rather than for
storage. That being the case, a floating reservoir sump for purrping out
water could be a desirable ancillary fixture at its terminus.
FLQATIR; PIPELINE. A floating pipeline is a meni>rane tube for water
transmission similar in concept to a floating canal except that it is
enclosed. No flotation devices are needed to keep it afloat and the tube
provides a c~lete separation of fresh water fran seawater. Figures 40
and 41 show the pipe at high and 10lrl tides, respectively. '!'he slightly
lighter freshwater density and the slight buoyancy of the polyethylene
(density about 0.92) is sufficient to keep the pipeline floating. An
accumulation of sediment deposition in the pipe over a long period may,
however, neutralize this natural advantage.
While anall, 3 ft (0.9 m> wide inlet tubes were used for filling the
floating reservoir and bag, the enphasis here was on a large pipe with a
9-ft (2.7~) circumference as shO'tln below.
36
"'"'"."'"'"
K '"7ft~
Floating Pipeline
The pipeline is not cylindrical, but flattened to conform to the hydraulic
characteristics of lighter fresh water being supported by denser seawater.
Because there is no pressurization, it is essentially an open-channel flow.
The test pipe was 100 ft long and anchored at its terminus with sand
bags to preclude movement with the ocean currents. At its intake end
a reinforcing rectangular wooden frame l~ ft by 6 ft (0.5 x 1.8 rn) was
attached to the tube to support the pipeline mouth. By using wood in the
Figure 37. Floating canal at high tide. The break in thefloats on the left is from the rupture when ithad been used as a curtain.
Figure 38. Floating canal at low tide. canal water isbeing lost over the side at right where floatsare over-ridden by the escaping water.
Figure 39. Streamwater spilling out of floating canalunsupported by seawater at low tide
37
38
Figure 40.Floating pipe at high tideduring initial filling.The fullness in the foreground is where it hasfilled; the unfilled portion is dr ifting to theleft. Bump on left sideof pipe is an air bubbleunder the membrane.
Figure 41. Floating pipe at low tide. There is lesslikelihood of spillage as compared to thefloating canal.
39
framing, this intake was designed to slightly float thereby nSl.ng and
falling with the tide while skimming the surface fresh water (see Fig. 42).
The pipe and the fluctuating skimming intake worked well. Salinityreadings taken during the I wk test period indicated that the separation of
waters continued even after vandals had thrown large rocks onto the pipe.
These rocks Penetrated the top membrane but not the bottom. There was undoubtedly some leakage outward from the pipeline but it was judged insignificant because the torn edges of the membrane did not even ripple to
indicate outflow, or inflow for that matter. While it would be imprudentto walk on the pipe, skimming over it by swimming did not adversely affect
the pipe of its flow.
The advantage of the pipe over the canal is that no flotation device
is needed and complete separation of waters is assured.
Figure 42. Wood-framed floating pipe intake designed toskim lighter stream water floating on denserseawater. Held in place by straps, it risesand falls with the tide.
ENVIRONMENTAL IMPAC1'
After testing was completed, all materials were removed from the site,
making it impossible to detect that the project had taken place. No de-
40
tectable envirorunental i.np:lcts occurred, even with the curtain enclosure
because of its relatively small size. There was free passage of biota
during its testing because excess inflow water was allowed to escape at
both ends of the curtain.
SUMMARY, CDNCLUSIONS, AND REXDMMmDATIONS
This pilot field study tested the storage of stream water in a coastal
embayment by using impermeable membrane liners to separate seawater from
fresh water. Prototype field-scale models of a curtain, bag, and floating
reservoir were tested. Among these the bag was the easiest to fabricate
and deploy, followed by the floating reservoir. The curtain was the JOOst
difficult. In addition to the above structures, a floating canal and a
floating pipeline for conveying flowing water on the ocean surface were
tested.
Based on the study, the following conclusions and reconmendations are
presented.
1. The adverse effects of tides on the ment>rane structures were
graphically demonstrated. A receding tide left the water-filled
bag and floating reservoir completely aground on the muddy bottom
and consequently without support. This caused the bag to rupture
and the floating reservoir to spill out its freshwater content.
It is therefore imperative that a storage site for these struc
tures have sufficient water depth to keep them afloat at low tide.
The bag and floating reservoir are still considered viable water
storage options and their further developnent should be pursued.
2. The bag and floating reservoir twisted themselves around the man
grove tree to which they were tied. A tethering mechanism that
moves in the same direction as the membrane structure affected by
currents is needed on the anchorage.
3. Tides also affect the curtain. The large amount of slack needed
to confine the captured water as the tide recedes greatly curtails
its usefulness. On the other hand, a receding tide can be used to
rapidly rE!Ilove seawater captured within the curtain at the time of
deployment by allowing the water to escape through one-way valves.
However, the need for the large amount of tide-related slack is a
41
drawback needing examination of alternative deployment schanes.
4. A ment>rane floating canal and floating piPeline were develoPed and
tested as means of conveying water as continuous flow from one
point to another CNer the seawater, rather than for storage. The
design is sinple and the prototypes worked well. They can be used
to carry water from the stream IOOUth to anywhere along the shore
where it can be pumped out for use. Since the canal and pipe
float on the surface, boats cannot pass over thEm without damaginJ
the membrane.
5. Sufficient progress has now been attained that in the next stage
a first priority effort should be made on the selection of a
suitable membrane.
6. A demonstration project could be develoPed of prefabricated rnenrbrane structures to store fresh water in a coastal ent>ayment.
7. The site of a demonstration project should be selected early to
enable the necessary applications of permits and other reqUire
ments, such as the preparation of an environmental impact state
ment.
8. It would be desirable to inprove the permit grantinJ processes
for research projects to facilitate their starting on time.
9. The private sector should be asked for their input to the demon
stration project.
10. The general public should be informed when the demonstration
project is goinJ through different stages of developnent.
11. No adverse environmental impacts were detected during or after
the pilot study.
The authors wish to especially thank the project Advisory Coomittee
meut>ers: Mr. John Y.C. Chang of the Board of water Supply, City and
County of HonolulU; Mr. Francis Mau, Environmental Branch, u.S. Department
of the Navy, Naval Facilities Engineering canmand, ~cific ocean Division;
Mr. Manabu Tagomori, Division of water and Land Developnent, Hawaii State
Department of Land and Natural Resources; and Mr. Johnson J.S. Yee, water
Resources Division, u.S. Geological Survey. Their suggestions and interest
42
in the project contributed to the successful testi.r:g of this pilot study.
Our appreciation is also extended to the above agencies and to the Depart
ment of Transportation Services, City and County of Honolulu for approving
the right-of-entry pennits necessary for using the project site.
We are grateful for the all-around assistance and the Fhotographs
taken by Henry K.Gee, Research Associate, WRRC; and the work in fabrica
tion and deployment of the membrane IOOdels by our field crew of Shan-Hsin
Chiang, Michael Miyahira, Ronald Lau, Melissa King, and volunteers, Thomas
W. Giambelluca and Daniel Dugan. The successful testing of the membrane
models could not have been acconplished without their assistance. To
Dr. L. Stephen Lau, Director, Water Resources Research Center, University
of Hawaii at Manoa, our special thanks for his constant encouragement and
interest in this project throughout its various FOases.
Fok, Y.-S. 1983. Plastic membranes as engineering construction materials.for water resources developnent. Taiwan Water Conservanc.Y 31:13-18.
___, and Murabayashi, E.T. 1980. utilizing of flexible membrane toimpOund runoff water in receivi.r:g coast for water conservation andquality control. .1n Proc.« Int. Conf. on Water. Resources Deyelo.gnent,vol. III, pp. 1003-1008, Taipei, Taiwan, Republic of China, May.
___, and 1981. Water reuse by rainwater cisterns and imper-vious rnent>ranes. In Pmc.« Water Reuse fWmsium II 3: 2487-99,Washington, D.C., August.
Murabayashi, E.T. 1984. Impenneable membrane reservoir-·Stream-waterstorage in the ocean using an impenneable membrane liner. In Alternatiye Water SOurces in the Pacific, QI2M Hill seminar, Ala ltk>ana Americana Hotel, Honolulu, Hawaii, 15 August, 22 pp.
___, and Fok, Y.-S. 1983. Stream-water storage in the ocean by usingan impenneable membrane. Tech. Rep. No. 152, Water Resources ResearchCenter, University of Hawaii at Manoa, Honolulu. 64 pp.