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EFFECT OF STORM RUNOFF DISPOSAL AND OTHER ARTIFICIAL RECHARGE TO HAWAIIAN GHYBEN-HERZBERG AQUIFERS
by
Frank L. Peterson
&
David R. Hargis
Technical Report No. 54
November 1971
Project Completion Report
of
EYALUATION OF ARTIFICIAL RECHARGE IN HAWAIIAN GHYBEN-HERZBERG AQUIFERS
OWRR Project No. A-02B-HI, Grant Agreement No. 14-31-0001-3211
Principal Investigators: Frank L. Peterson and Doak C. Cox
Project Period: July 1, 1970 to June 30, 1971
The programs and activities described herein were supported in part by funds provided by the United States Department of the Interior as authorized under the Water Resources Act of 1964, Public Law 88-379.
ABSTRACT
Artificial recharge for the purpose of replenishing the fresh ground-water body in Hawaii has been deliberately practiced in a few areas for many years, and has been recognized as incidental to other practices, principally irrigation, in many areas for several decades. The effects of these various artificial recharge practices on Hawaii Ghyben-Herzberg aquifers are briefly described in this report.
In recent years, the practice of artificially recharging wastewater such as storm runoff, sewage effluent, and various industrial wastes into the subsurface has become of growing importance in Hawaii. In 1970 the Kahului Development Company began construction of a collecting basin and four deep injection wells for the disposal of storm runoff from a residential development in Kahului, Maui. This presented a unique opportunity to evaluate the suitability of the site for artificial recharge and to study the possible effects recharge of storm runoff might have on the local ground-water body, both from a water quality and a hydraulic standpoint. Studies were made to determine the following information: (i) the concentrations of selected chemical and biological parameters in storm runoff from residential areas in the town of Kahului and in the ground-water body in the area of the collecting basin and injection wells for the purpose of predicting the effects of artificial recharge of storm runoff on the water quality of the existing local ground-water body, (ii) the injection rates that can be expected for the completed injection wells by means of pumping and injection tests, and (iii) the movement of the injected water by monitoring water levels and selected chemical and biologicaZ parameters at observation wells near the injection site.
The results of pumping and injection tests of one completed well and one test hole indicate that the finished injection wells should be able to inject at rates in excess of 5500 gallons per minute per well if significant clogging from sediment does not occur, and if hydraulic interference between the four wells operating simultaneously is not significant.
Water analyses indicate that quality of the storm runoff from the Kahului area is generally good, with low dissolved solids and low chloride concentrations. Some fecal coZiform will undoubtably be introduced into the aquifer during injection of storm runoff. However, dilution of the injected runoff by the ground water and the hostile environment presented by the saline water in the disposal zone should eliminate any bacterial hazard. The most serious potential water quality problem may be a reduction in injection efficiency owing to possible well clogging by heavy sediment loads. The general water quality effects of injecting storm runoff into the ground-water body will be to decrease the dissolved solids concentration of the ground water in the vicinity of the wells.
iii
CONTENTS
LIST OF FIGURES .......••........................•••..........•••....... v
LIST OF TABLES ...........•.................•...........••.•.•......... vi
INTRODUCTION .. .......................•......•....•...•.•...•....•.•...• 1
Background of Study ......................•....•...................•• 1
Objectives ........................................................... 1
Condu ct of Study .................................................... 2
SUMMARY OF ARTIFICIAL RECHARGE PRACTICES IN HAWAII Artificial Recharge Incidential to Irrigation Practices ...........•. 3 Artificial Recharge by Spreading and Induced Ditch and Reservoi r Leakage ................................................... 5
Artificial Recharge through Wells and Shafts •...•..........•........ 6 Sewage Effl uent Di 5 posa 1 ............................................ 7
Cess POQ 1 S.eepage ....•............................................... 7
Industrial Waste Disposal ...........••....•.....•••.............•... 8
ARTI FI CIAL RECHARGE OF STORM RUNOFF ................................... 10 Hilo, Hawaii ..................................•.................... 12
Puukapu, Hawaii .................................................... 13
Wa i 1 u k u, and Ka h u 1 u i , M a u i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 3
Kahu 1 ui Development Company, Maui .................................. 17
CONCLUS IONS ••..•••.••..••....•••...•.•••.•••.•.••••..•.......••••••••. 46
RECOMMENDATIONS ••.•.••••..•.•....•••••••••..•.••...•••.•....•••••..••. 48
ACKNOWLEDGEMENTS. • • • • . • • • . . . . . • • • . . . • • • . . • • • • • . • . • . • • . . . . • • . . • • • . . . •• 49
RE FERENCES ..•••••••...••••.••••...•••..•••••..••••..•.••••...•.•.•.••• 50
LIST OF FIGURES
1. Maui isthmus location map .....••..•...••.••...••••...•....••••.•... 9 2. Geologic logs of Maui Land and Pineapple wells 20-A, B, C, D, and
Kahului Development Company test hole KD-l ••••.....••.•..•....•..• ll 3. Typical storm disposal well at Kahului, MauL ..................... 14 4. Geologic logs of Maui County storm runoff disposal wells ..•••••... 19 5. Ground-water level contour map of the Maui isthmus ..•••.•.••.•.••. 22 6. Chloride concentration versus depth in test hole KD-l ...••..•..••• 23
v
7. Tidal response of shaft 13, well 20-A, and well 20-C, compared to tides at Kahului Harbor ................................ 24
8. Location of Kahului Development Company's storm runoff disposal system ..................................................................................................... 26
9. Plan of Kahului Development Company's collecting basin and disposal wells .....•.........•• ~ ................. " ....•....••.. .... 27
10. Detailed plan of Kahului Development Company's injection wells .............................................................. 28
11. Chloride concentration versus pumping rate and time in test hole KD-l ........................................................................................................ 30
12. Chloride concentration versus amount of water pumped and time in test hole KD-1 following injection of fresh water ........•. 31
13. Conductivity in shaft 13 for the period March 26-30, 1971, during injection and pumping test of wells KD-l and KD-2 ........... 34
14. (A) Diagram of pumping and injection tests of wells KD-1 and KD-2 on March 27, 1971. (B) Summary of water level measurements in wells KD-l and KD-2 during the pumping and injection tests ............................................................................................. 35
15. Chloride concentration versus time in well KD-3, during pump and injection testing on wells KD-l and KD-2 on March 27, 1971 ........................... III ........................................................................... 36
16. Nitrate concentrations of ground water, uncontaminated rain, and stream water from Mau i and Oahu ................................ 41
LIST OF TABLES
1. Analyses of ground water, storm runoff, cannery waste water, and dissolved streat sweepings from Kahului, Maui •••...•......••... 16
2. Summary of analyses from fecal coliform in ground water and storm runoff at Kahului t Maui .................................. 43
3. Comparison of storm water quality from Kahului, Maui with other reported resu 1 ts ............................................................. 44
vi
INTRODUCTION
Background of Study
Todd (1959) has defined artificial recharge as the supplementing
of natural infiltration of surface water or precipitation into under
ground formations by using some construction, spreading the water, or
otherwise changing the natural conditions. Most commonly, the purpose
of artificial recharge is to replenish the fresh ground-water body.
In Hawaii, artificial recharge has been deliberately practiced in a
few areas for many years, and has been recognized as incidental to
other practices (principally irrigation) in many areas for several
decades. Hargis and Peterson (1970) have described artificial re
charge practices in Hawaii, and where possible, have attempted to eva
luate the effectiveness of these practices.
In recent years, another aspect of artificial recharge has be
come important in Hawaii. This is the growing practice of artificially
recharging waste water such as storm runoff and sewage effluent into
the subsurface. Ideally, such recharge is best kept out of fresh
ground-water aquifers. However, owing to the rather unique Hawaiian
hydrologic and geologic conditions in Hawaii (Peterson, 1971), most
artificial recharge eventually reaches the basal lens and in some
instances may contaminate fresh ground-water aquifers.
Objectives
Because of the great interest in exploring the possibility of
replenishing Hawaii's fresh ground-water bodies by artificial recharge,
as well as the growing concern about possible contamination of these
same fresh ground-water bodies by artificial recharge of less desirable
waters, this report summarizes the effects of all types of artificial
recharge on Hawaii's ground-water bodies. The principal objective,
however, is to describe the effects of artificial recharge of storm
runoff to Hawaiian ground-water bodies.
2
Conduct of Study
The investigation of artificial recharge practices in Hawaii
was first begun in July 1969 by the Water Resources Research Center,
University of Hawaii with the initial intent of compiling all known
sites where artificial recharge was practiced in Hawaii, obtaining
quantitative information on the amounts of water recharged and eva
luating the effectiveness of the various methods used. The results
were reported by Hargis and Peterson (1970). In a related Water
Resources Research Center study, Tenorio, et al.~ (1969) and Tenorio,
et al.~ (1970) described the general chemical effects of recharge of
return irrigation water to the subsurface.
In July 1970, a second phase of the investigation of artificial
recharge practices in Hawaii was begun, concerned mainly with recharge
of storm runoff to the basal ground-water body and restricted primarily
to the Maui isthmus area. Essentially, the conduct of this study
consisted of three main tasks: chemical and biological analyses to
determine the quality of the recharge and receiving waters, pumping
and injection testing to determine possible recharge rates, and water
level and water quality monitoring to determine the probable movement
of the recharge waters.
SUMMARY OF ARTIFICIAL RECHARGE PRACTICES IN HAWAII
Artificial recharge practices in Hawaii may be summarized as
follows (Hargis and Peterson, 1970):
(i) incidental ditch and reservoir leakage and other non
deliberate recharge of irrigation water,
(ii) induced leakage from ditches and reservoirs and deliberate
spreading of excess irrigation water,
(iii) deliberate recharge of fresh water, primarily stream-flow,
through wells, shafts, pits, eta.~
(iv) storm drainage disposal, usually through wells and pits,
Cv) disposal of treated sewage effluent, primarily through wells,
and
(vi) cesspool seepage.
In addition, minor amounts of artificial recharge also occurs from
miscellaneous practices such as subsurface disposal of industrial
wastes and cooling water, excess water from car washes, etc.
Artificial Recharge Incidental to Irrigation Practices
3
"The most significant source of artificial recharge to ground-water bodies in the Hawaiian islands is undoubtably ground-water recharge which is incidental to irrigation practices. Owing to the extremely high permeability of Hawaiian soils and rocks, most unlined reservoirs and ditches leak considerable amounts of water which becomes available for groundwater recharge. Likewise, direct application of irrigation water to the fields results in large amounts of water deeply percolating to become recharge, mainly to basal ground-water bodies (Hargis and Peterson, 1970, p. 3).11
Unfortunately, owing to a general lack of data, it is difficult
to estimate the actual amounts of ground-water recharge which occur
incidental to irrigation practices. Mink (1962) calculated that for
central Oahu between 50 and 60 percent of the annual average of 123
inches of irrigation water applied to the fields eventually recharges
the ground-water body. Caskey (1968) calculated that for the eastern
slopes of West Maui, approximately 60 to 70 percent of the irrigation
water applied to the fields becomes ground-water recharge. The
amounts vary from plantation to plantation and island to island owing
to differences in irrigation practices and climatic differences, but
it is generally agreed that at least 50 percent of the water applied
to the fields during irrigation becomes ground-water recharge and con
siderally more water is incidentally recharged during conveyance to
the fields.
It has long been recognized in a general way that irrigation
practices in Hawaii have contributed a large volume of recharge as
irrigation return water to the basal aquifers underlying irrigated
areas, and that the irrigation return water carried with it dissolved
solids contributed by the application of fertilizers and related
agricultural practices as well as dissolved solids from the irrigation
water itself. However, with the exception of early work by Bryson
(1953), Mink (1962), Ayres and Hagihara (1963), and Lee (1967) in a
few selected areas, which show only tabulations of chemical data with
4
little discussion of the detailed effects, neither the influence of
irrigation nor that of agricultural practices on the quality of Hawaiian
basal aquifers has been studied to any considerable extent.
The first extensive study on the qualitative and quantitative
effects of irrigation return water on basal ground-water was done by
Visher and Mink (1964) in southern Oahu. By comparing the magnitude
of specific index constituents (silica, nitrate, sulfate, and bicar
bonate) from irrigation return water with those normally found in un
contaminated water from various ground-water aquifers on Oahu, they
were able to verify that large volumes of irrigation water containing
significantly high concentrations of dissolved solids recharge the basal
ground-water bodies underlying irrigated areas in southern Oahu. In
addition, Takasaki and Valenciano (1969) also verified the presence
of irrigation return water in lesser amounts than found by Visher and
Mink in the Kahuku, Oahu area by the persistent occurrence of elevated
nitrate concentrations.
Most recently, the Water Resources Research Center of the
University of Hawaii has concluded an extensive three-year study of
the identification and effect of irrigation return water in southern,
central, and northern Oahu, and west and central Maui. The results
of the study of Maui and northern Oahu by Tenorio, Young, Burbank,
and Lau (1970) indicate irrigation return water is definitely present
in the basal water bodies underlying the three study areas. Consi
derable increases in nitrates, sulfates, bicarbonates, and silica
over a period of approximately two years or exceeding one complete
cycle of planting and harvesting of sugarcane, verify the strong
influence of irrigation and agricultural practices in altering the
overall quality of the basal water sources in the three areas.
The basal water quality of West Maui has deteriorated in part owing
to fertilization, and to a greater extent, owing to heavy pumping and
recycling of the basal water.
Ground-water quality in the Kahuku area of northern Oahu shows
the obvious presence of irrigation return water, but, unlike West
Maui, the magnitude of the increases relative to uncontaminated water
sources is considerably smaller.
The study in southern and central Oahu (Tenorio, Young, and
5
Whitehead, 1969) indicated effects similar to those found in the
Kahuku area. Nitrates from ground-water bodies in irrigated areas
commonly are two to three times as great as from uncontaminated areas
and sulfates may be as much as 10 to 20 times as great. Furthermore,
as is indicated by well conductivity logs (Tenorio, Young, and Whitehead,
1969, pp. 21-25), the irrigation return water forms a layer of poorer
quality water on the top of the basal lens 40 to 50 feet thick under
most irrigated areas.
It is interesting to note, however, that the chloride concen
trations in basal aquifers recharged by irrigation return water
generally has not been greatly increased. In fact, in some ground
water bodies with relatively high chloride concentrations, such as
central Maui and where significant amounts of irrigation water come
from imported surface sources of low salinity, recharge by irrigation
return water decreased the chloride concentration in the ground water.
Artificial Recharge by Spreading and Induced Ditch and Reservoir Leakage
In addition to recharge incidental to irrigation, considerable
amounts of deliberate artificial recharge associated with irrigation
practices also occur. These primarily consist of recharge by water
spreading and induced ditch and reservoir leakage. There are at least
three locations where this type of recharge is known to occur and there
are probably numerous other locations where this form of recharge is
practiced on a smaller scale. However, much like incidental recharge,
it is difficult to quantitatively assess the magnitude of this recharge.
The deliberate recharge of excess irrigation water to the sub
surface is practiced by the Hawaiian Commercial and Sugar Company on
central Maui. Over the past 20 years, in excess of 50,000 million
gallons of fresh water have been recharged to the subsurface by spread
ing in gulches and irrigation ditches and seepage from reservoirs and
pits (Hargis and Peterson, 1970).
Approximately 100 million gallons of water is estimated to be
recharged to the subsurface annually by induced leakage from the
Waiawa reservoir in leeward Oahu. Four reservoirs in Nuuanu Valley,
6
also on Oahu, are thought to recharge a significant, but unknown,
amount of water to high-level ground-water bodies beneath them
(Hargis and Peterson, 1970).
The effects of deliberate recharge to the basal ground-water
bodies in irrigated areas are difficult to separate from those of non
deliberate recharge incidental to irrigation practices. In cases
of deliberate recharge of excess water by spreading on fields and in
duced leakage from ditches, the effects probably are very similar to
recharge incidental to irrigation. In cases of deliberate recharge
by spreading in gulches and on other uncultivated and unfertilized
land, the general effect depends on the relative qualities of the
recharge and ground water, and generally the effect is to improve the
ground-water quality.
In all cases, however, the amount of water deliberately recharged
to the basal ground-water body near irrigated areas is insignificant
compared to the amount of water recharged as incidental to irrigation
and its effect most likely is completely obscured by irrigation return
water.
Artificial Recharge Through Wells and Shafts
At the present time, the only deliberate artificial recharge of
fresh water through wells and shafts in Hawaii is practiced by the
McBryde Sugar Company at Hanapepe, Kauai. Surface water from the
Hanapepe River is diverted into a shaft-and-tunnel system and recharges
the basal ground-water body. Ground water is pumped from the same shaft
for irrigation use so that only in the wet winter months when irrigation
requirements are not great does the amount of recharge exceed the
pumpage. Since 1924, when the recharge practice began, approximately
103,000 million gallons of water have been recharged through the
Hanapepe shaft (Hargis and Peterson, 1970).
Because annual pumpage from the Hanapepe shaft exceeds annual
recharge, the net quantitative effect is very local in nature and is
felt during only a few months of the year. Qualitatively, the most
serious effect is sedimentation in the shaft sump and tunnels which
require periodic clean-up.
7
Until recently, surface water from the Lawai Stream also was
diverted by McBryde Sugar Company for an artificial recharge operation
similar to the one at Hanapepe. However, severe sedimentation problems
have clogged some of the tunnels and forced the operation to be dis
continued at this location.
Sewage Effluent Disposal
No recharge to the subsurface of sewage effluent is known to
be practiced in Hawaii at the present time. However, several sewage
treatment plants which will utilize subsurface effluent disposal are
presently under consideration.
The state plans to recharge treated sewage effluent to the
subsurface from its new tertiary treatment plant in Waimanalo, Oahu.
The deep well disposal facility has already been completed and recharge
will begin as soon as sewerage accouterment are constructed. Three
IS-inch diameter wells will dispose of the treated sewage into a
highly permeable limestone formation, approximately 100 to 200 feet
thick, which underlies the Waimanalo coastal plain. Preliminary
results (Lum, 1969) indicate that the disposal wells have a minimum
capacity of 14 million gallons per day, and that, furthermore, each
disposal well has a minimum injection capacity of four to five
million gallons per day with two to five feet of injection head.
The potential effects of the sewage effluent as recharge to the
subsurface at Waimanalo are uncertain, however, saline water saturates
the limestone disposal zone (Lum , 1969) so that no fresh~water
aquifers should be affected. Once recharge begins, the entire system
will be very closely monitored and the project should serve as an
excellent model for the design of future subsurface sewage disposal
systems.
Cesspool Seepage
Cesspool seepage contributes an unknown, but small amount of re
charge to ground-water bodies in Hawaii. Rough calculations (D. Cox,
personal communication) indicate that approximately 20 years ago, when
8
the sewerage syst.em expansion was just beginning in Honolulu, cesspool
seepage contributed as much as perhaps 10 percent of the total ground
water draft in the Honolulu district. However, its signifieance is
steadily decreasing owing to the increased use of unified sewerage systems
in the development of urban areas. Cesspool seepage has produced no known
bacterial contamination in basal ground water (except in the Red Hill
shaft which probably was contaminated from South Halawa stream). and there
is no epidemiologieal evidence of viral disease transmission. Nitrate
levels only at Waialae shaft have been of some concern, but are well below
tolerance limits. Thus, the effect of cesspool seepage is minor in terms
of the total quantity of water recharged and is significant only in terms
of local contamination of shallow ground-water bodies by overloaded or
improperly constructed installations.
Studies by Koizumi, Burbank, and Lau (1967); Young, Lau, and Burbank
(1967); Ishizaki, Burbank, and Lau (1967); and Tanimoto, Burbank, Young,
and Lau (1968), have investigated rates of infiltration and percolation
rates of sewage through different Hawaiian rocks and soils.
Industrial Waste Disposal
Disposal of industrial waste by artificial recharge to the
subsurface is known to be practiced at several locations in the Honolulu
and Pearl Harbor areas in southern Oahu. However, in all of these
instances, recharge is by wells constructed in the sedimentary caprock
which contains brackish water. The only known case of recharge of
industrial wastes to a fresh basal ground-water body is practiced by
the Maui Land and Pineapple Company at Kahului, Maui and, in this
case, the zone of disposal is in the salt water below the fresh basal
lens.
The Maui Land and Pineapple Company injects a mixture of salt
water and fresh water used in cooling and washing at their Kahului
cannery into wells 20-A and 20-D (see Fig. 1 for location). Well
20-A is a 6-inch diameter hole drilled in 1948 to a depth of 285
feet below sea level and cased to a depth of 220 feet below sea level.
The water that enters this well is first treated with ammonia to
neutralize the sulfuric acid used in the processing operations in the
E9 DRILLED WELL
SA.MPLE POINTS
• PIT WITH TWO WELLS
FIGURE 1. MAUl ISTHMUS LOCATION MAP.
MAUl
\0
10
cannery, and then injected at rates of 650 to 700 gpm with a head bUild-up
of about ten feet (F. Fukunaga, personal communication, 1971). The
geologic log for this well, shown in Figure 2, indicates the disposal
zone is in basalt.
Well 20-D is a 20-inch diameter hole drilled in 1958 to a depth
of about 315 feet below sea level and cased to a depth of about 114
feet below sea level. The geologic log for this well (Fig. 2), in
dicates the disposal zone also is in basalt. An injection test
performed on this well by R. Bruce and W. Wilmore (1959) resulted in
a head bUild-up of six feet at an injection rate of 2500 gpm. Debris
from the injected water appears to have. partially clogged the well, so
the hole was cleaned out and tested once again. Debris-free water was
injected at a rate of 3700 gpm with a head build-up of almost seven
feet (Bruce and Wilmore, 1959). The injection rate per foot of head
build-up per foot of the open hole is about 2.3 gpm/ft/ft for well 20-A
and 2.6 gpm/ft/ft for well 20-0. These rates indicate that the per
formance of the two wells is about the same, the difference is pro
bably due to the larger diameter of well 20-0. Serious clogging pro
blems, which have developed in well 20-0 over the past few years
and are believed to be caused by particulate matter picked up by the
injection water during the industrial process at the cannery, now
necessitate the treatment of the well with dry ice every few months
(F. Fukunaga, personal communication, 1970).
ARTIFICIAL RECHARGE OF STORM RUNOFF
Historically, disposal of urban storm drainage in Hawaii has
been accomplished by direct discharge into the ocean or by discharge
into natural streams which discharge into the ocean. In the past few
years, owing to gr~atly increased urbanization and to an ever-growing
concern about possible degradation of nearshore ocean waters by in
creased sedimentation from urban runoff, disposal of urban storm
drainage into the subsurface has become increasingly popular.
There· are four locations in Hawaii where disposal of storm runoff
to the subsurface either is already being practiced or where such
J-III III II.
!
Z 0 j: ~ III .J III
+40
+ 20
MAUl PINEAPPLE COMPANY WELLS
WELL 20-A ELEV. +15'
WELL 20-D
ELEV. +7'
WELL 20-B ELEV. lEI'
'WELL 20-C ELEV. lEI'
KAHULUI DEVELOPMENT COMPANY TEST HOLE KD-I ELEV. :!IO'
SEA H;::'~J F::t E.t~ rn M LEVEL '§;. '.;.:: ~'..'.
-50
-100
-ISO
-200
-2SO
-:!Ioo
~ tl BOTTOM OF CASING
F fJ
ELEV. -2SS'
(FROM DRILLER'S LOG, SAMSON a SMOCK, L TD,I
BOTTOM OF CASING
CALCAREOUS SAND
~ CORAL RUeBLE
ALLUVIUM
~l GRAVEL
f'::.j BASALT
CLAY AND GRAVEL
VERTICAL ELEVATION, 1"=50'
HORIZONTAL MEASUREMENT,
NOT TO SCALE
(FROM DRILLER'S LOG,
SAMSON a SMOCK, LTD.!
ELEV. -:!IllS'
DRILLER'S
SAMSON a
LTD.!
BOTTOM OF CASING
BOTTOM OF CASING
ELEV. -:502' ELEV. -2&&
(FROM DRILLER'S
LOG, SAMSON a
SMOCK, LTD.!
PROPOSED
CASING
DEPTH
ELEV. -220'
(FROM DRILLER'S
LOG, ROSCOE
MOBS CO.!
FIGURE 2. GEOLOGIC LOGS OF MAUl LAND AND PINEAPPLE WELLS 20-A,B,C,D, AND KAHULUI DEVELOPMENT COMPANY TEST HOLE KD-l.
i-' i-'
12
facilities will become available in the near future. In Hilo, Hawaii
and Wailuku and Kahului, Maui, local urban storm runoff has been
recharged into the subsurface through a series of shallow wells and
pits for the past several years. At Puukapu, Hawaii near Kamuela,
facilities for r~charge of storm runoff to the subsurface are available,
but have not yet received extended use owing to general drought con
ditions for the past two years in the area. Finally, a recharge in
stallation consisting of four deep wells for disposal of storm runoff
from a Kahului Development Company housing development at Kahului, Maui presently is being completed and should be r~ady for the coming winter's
storm drainage. The operation of the first three of the above installa
tions has been described in detail by Hargis and Peterson (1970) and
is only summarized here. The Kahului Development Company recharge
installation has been described in an unpublished report by S. Bowles
(1970) and in an unpublished University of Hawaii Master's thesis
(Hargis, 1971). However, because of its potential importance as a
model for other installations for disposal of urban storm runoff in
Hawaii, a detailed description of the recharge facility and related
research conducted by D. Hargis in Kahului is included in this report
in the section entitled, "Kahului Development Company, Maui," p. 17.
Hilo, Hawaii
Some 26 storm runoff disposal pits (for location see Hargis and
Peterson, 1970, pp. 29-30) have been constructed in poorly drained
residential and industrial areas in Hilo, Hawaii by the County of
Hawaii Department of Public Works to dispose of standing water after
heavy rains. The recharge pits consist of shafts approximately 5
feet in diameter with varying depths from 7 to 30 feet. They are con
str.ucted at topographic low areas in the streets so that water will
flow into them by gravity and directly into the basal ground-water body
underlying the area. Steel gratings at street level protect the shafts
from debris.
The recharge pits have relieved most of the problems of standing
water after heavy rains, but, unfortunately, no quantitative data are
availabie on the performance of these shafts and their effect on the
ground-water body.
13
Puukapu, Hawaii
The United States Soil Conservation Service and the State of
Hawaii completed construction of a holding reservoir and a battery of
six. recharge w~lls to inject flood waters by gravity into basalts
in the Puukapu area on the iSland of Hawaii in 1968 (for location see
Hargis and Peterson, 1970, p. 26). This facility is very similar
in construction and intent to that installed in Kahului by the Kahului
Development Company. The six recharge wells, which are each 24 inches
in diameter, range in depth from 125 to 175 feet, and all terminate
in unsaturated rock, probably several hundreds of feet above any
water-bearing zone. The six disposal wells are estimated to have a
combine,d recharge capacity of 294 cfs or 49 cfs each (Shogren, personal
written communication, 1970.). These recharge rates are based on a
series of injection tests performed on six test holes also drilled in
the reservoir invert (Olson, 1966).
Wailuku-Kahului, Maui
The County of Maui Department of Public Works has installed
some 17 recharge wells in residential areas in Wailuku and Kahului
to dispose of storm rUJ1.off and to eliminate standi~g water in poorly
drained areas after heavy rains (Fig. 1). In addition, two dis
posal pits, about 100 feet in diameter and 20 feet deep, have been
constructed in Kahului.
The wells penetrate from 21 to 89 feet below' sea level and range
in elevation from 5 feet to 105 feet above sea level. They are in
stalled in the bottom of shallow pits about six feet and four feet
on a side, excavated just below street level at locations that ex
perience large concentrations of standing water after storms. In
several cases, two separate pits are excavated below street level
and connected by a pipe. One pit then serves as a collecting basin
and the well is drilled in the bottom of the second pit to dispose of
the water. Heavy iron gratings at street level prevent large debris
from entering the collecting basins, and U-tube attachments at the
intake duct to the well prevent floating debris from entering the
wells. Figure 3 shows a sketch of a typical disposal well installation.
14
RUNOFF DISPOSAL WELL INSTALLATIONS - KAHULUI
STEEL GRATING
aROUND SURF E ·---3·--·~
OONCRETE "-...
U~ TUBE TO PREVENT CLOGGING BY DEBRle __ --.....Jtc.4-~
STEEL PLATE
SURFACE 1-0-1 .. --- 4' ---1---<001
S'
4'
I ....L WELL
I I
STEEL GRATING
S'
COLLECTING BASIN
DISPOSAL BASIN
FIGURE 3. TYPICAL STORM DISPOSAL WELL AT KAHULUI, MAUl (AFTER HARGIS AND PETERSON, 1970).
The hydrogeology of the Wailuku-Kahului area is discussed in a later
section (pp. 13 ) of this report.
There are no quantitative data available on the amount of
water recharged by these wells, but it is reported (Araki and Stone,
personal communication, 1970) that the wells have been effeetive in
limiting the duration of standing water to a few hours where it used
to last for days.
Chemical and biological analyses of water samples taken from
well 3-A to provide background water quality information for the
Kahului Development Company recharge project described later in this
report show several interesting but disturbing results. Nitrate
concentrations in well 3-A, averaging 5.8 mg/l and ranging between
3.5 and 7.0 mg/l (Table I), are significantly higher than those from
15
the other sampling points in the area. Initially, these high nitrate
concentrations were attributed to runoff from surrounding lawns .• However~
nitrate concentration from actual runoff samples collected near well
3-A are considerably lower than in the well so that it appears likely
that well 3-A is being contaminated from another source. A sewer
line is located about thirty feet away from the well and some forty
feet above the water table. Two lateral lines from private residences
also pass within a few tens of feet of the well, but they are located
some forty feet above the water table (F. Araki, personal communica
tion, 1971). Whether or not this is the source of the nitrqte found
in well 3-A is not definitely known.
Fecal coliform analysis conducted on a sample from well 3-A
yielded 200 colonies per 100 milliliters which is in excess of standards
established by the State of Hawaii for water for drinking and food processing
(Hawaii Department of Public Health, 1967). This sample was taken
several hours after a heavy rain during which the well received runoff
from the surrounding residential area. A sample of the runoff draining
into well 3-A had a fecal coliform count of 9,000 colonies per 100
milliliters (see Aleo Place runoff, Table 1). Thus, it seems likely
that fecal coliform are introduced into the ground water through well
3-A and a similar situation probably exists at the other fourteen wells
of this type installed by the County of Maui. For example, runoff
samples obtained at Onehee Avenue also yielded high fecal coliform
16
TABLE 1. ANALYSES OF GROUND WATER? STORM RUNOFF? CANNERY WASTEWATER? AND DISSOLVED STREET SWEEPINGS FROM KAHULUI? MAUl. DATA FOR lAO STREAM? SHAFTS 16? 18? 19 AND 24 FROM TENORIO?et al' J (1969).
DEPTH RELATI VE TO MEAN SEA SUSPENDED
SI'MPLING LEVEL TOTAL DISSOLVED SOLlDS FECAL COLI FORM SITES (FEET) DATE CI NO, po, COD SOLIDS SOLlDS (CALCULATED) COLONIES PER 100 ml
lAO STREI'M 4/1S/68 4.7 o. a 0.0 56 6/19/68 6.0 o. a 0.20 67 1121/69 7.0 0.0 0.03 81 417169 5.0 2.7 0.04 41
SHAFT 24 6/17 /68 '+S5 20 0.50 1122 1/20/69 392 19 0.45 944 "/8/69 8.5 4.8 0.06 "0
SHAFT 19 "/IS/68 525 1.8 0.10 1303 6/17168 508 32 0.16 1392 1/20/69 "78 12 0.22 1"54 4/8/69 465 16 0.22 1384
SHAFT 18 6117/68 490 23 0.30 1182 1120/69 338 15 0.42 896 4/8/69 435 17 0.33 1112
SHAFT 16 4/18/68 304 1.6 0.20 946 6/17/68 380 22 0.44 1040 1/20/69 70 6.6 0.13 276 4/8/69 330 17 0.33 1003
WELL 3-A -5 1113/71 55 3.5 0.19 12.3 512 414 98 200 3/11/71 64 6.0 0.31 20.9 389 263 126 3/12171 67 0.56 47.8 2955 251 2704 3/13171 63 0.52 44.7 392 272 120 3/14171 41 5.5 0.41 56.6 435 282 153
SHAFT 13 0 11/12/70 86 2.2 0.61 4.5 436 "36 12/3170 77 2.1 0.55 0.2 275 1/8171 103 2.2 0.76 5.8 368 2/3/71 95 2.1 0.57 1.0 350 2/10/71 81 1.6 0.30 ".1 267 2/17171 99 1.9 0.'+8 '+.5 363 363 3/11171 126 2.1 0.32 0.7 327 3115/71 12" 1.8 0.65 2.5 344
WELL 20-A -268 1/12/71 22,000 0.90 32.1 28,307 27,969 338 1/13171 19,100 0.76 25.3 28,329 28,116 123
WELL 20-C TAP ON PUMP 9118170 18,800 a 0.19 47.4 33,625 33,625 10/1/70 19,100 0 0.19 47.0 37,600 37,600 12/3/70 19,000 0 0.19 52." 37,960 37,960 2/3/71 19,300 a 0.19 41.4 35,590 35,590 2/10171 19,900 0 0.19 47.2 35,840 35,840 2/17/71 19,900 ° 0.19 44.9 38,990 38,990 3/11/71 19,800 0 0.19 32.0 36,370 36,370 3/15/71 19,800 0 0.19 29.5 36,020 36,020
WELL KD-l -3 1/14/71 138 0.31 2.2 435 407 28 -20 3/ll/71 95 0.18 1.8 335 281 54 -20 3/12/71 94 1.6 0.27 3.0 296 267 29 -20 3/13/71 94 1.4 0.41 0 422 107 -20 3/14/71 98 1.5 0.43 1.1 336 24
-206 1/14/71 18,300 0 0.32 45.9 37,787 37,764 23 -206 3/11/71 8,500 0.8 0.25 31.8 32,112 15,227 16,885
3/12/71 8,600 0.8 0.31 11.9 30,851 15,113 15,738 3/13/71 9,700 0.9 0.3'+ 27.4 37,701 17,240 20,461
-20& 3/14/71 7,300 a 0.36 18.4 21,733 13,890 7,8'+3
UHU STREET RUNOFF 1/13171 6.5 0 13.4 281 3'+ 2"7 a
1/1"171 3.0 0 17.0 "04 47 a 1/15/71 3.0 0.20 48.3 232 38
ALEO PL. RUNOFF 1/13/71 4.5 0.28 15.5 194 114 80 9,000
ONEHEE AVE. RUNOFF 1/14/71 2.5 12.3 174 51 123 1,000
SWEEP 1 (ALEO PL.) 3/15/71 100 36." 363 245 118
SWEEP 2 (UHU ST.) 3/15/71 100 0.06 33.1 229 83 146
SWEEP 3 0.08 40.3 386 143 243 (ONEHEE AVE.) 3/15/71 100
CANNERY WASTEWATER 3/10/71 1,400 1." 2.33 16.9 5,792 4,670 1,122
3/12/71 50 1.2 1. 93 90.0 2,306 1,577 729
17
counts of 1,000 colonies per 100 milliliters (Table 1).
Although the amount of water recharged by these wells is small, the
storm runoff is recharged directly into the top portion of the relatively
fresh ground-water body underlying this area. Consequently, this presents
a potential contamination hazard to the fresh basal ground-water body,
which could be avoided by drilling and casing the wells through the
fresh water zone as has been done by the Maui Land and Pineapple Com
pany and the Kahului Development Company.
Kahului Development Company, Maui
In addition to the shallow Maui County recharge wells already
in operation in Wailuku and Kahului, in June 1970, the Kahului Develop
ment Company, a subsidiary of Alexander and Baldwin, Inc., proposed
the construction of a collecting basin and four deep wells as an
alternative to an ocean outfall for the disposal of storm runoff from
residential areas to be developed in the town of Kahului, MauL A
test hole on the site of the proposed collecting basin and well field
was drilled and tested in June 1970. Highly permeable zones were
indicated in the underlying rocks by preliminary injection and pumping
tests and the decision was made to proceed with the construction of a
basin and four disposal wells. This situation presented a unique op
portunity to make a quantitative evaluation of the suitability of the
site for artificial recharge and the possible effects artificial recharge
of storm runoff might have on the local ground-water body, both from a
water quality and a hydraulic standpoint. The Maui County wells, a
horizontal water-development shaft and the 3 deep wells of the Maui Land
and Pineapple Company located in the immediate vicinity of the proposed
collecting basin and deep disposal wells provided ample data collection
points. Furthermore, the four proposed deep disposal wells could be used
for various pumping and injection experiments to provide valuable informa
tion on the nature of the aquifer in the area and the injection rates
that could be expected in an actual recharge situation involving storm
runoff.
HYDROGEOLOGY. Th.e Maui isthmus consists of a broad plain formed by lavas
18
from Haleakala ponding against the eastern slope of West Maui. Much of
the isthmus is covered by consolidated and semi-consolidated calcareous
sand dunes blown inland during lower stands of the sea. The western edge
of the isthmus is overlapped by consolidated deposits of older alluvium
consisting of poorly sorted fanglomerates and unconsolidated deposits of
younger alluvium consisting of stream-deposited brown silt, sand, and
gravel (Stearns and Macdonald, 1942).
Geologic logs from Maui Land and Pineapple Company wells, located
directly north of the recharge site, and the Kahului Development Company
test hole (KD 1) show a veneer of calcareous sand, alluvium, and gravels
up to 70 feet thick covering the basalts in this area (Fig. 2). The
calcareous sand and gravels are highly permeable, and the alluvium,
generally, is of lower permeability. Geologic logs of the Maui County
disposal wells all show the same general sequence of calcareous sand at
the surface, which grades into alluvium, and then gravel and cinders
(Fig. 4). In general, farther north of the Kahului Development Company's
test hole the sediments overlying the basalts extend below sea level.
In the immediate vicinity of the collecting basin, the contact between
the basalt and the overlying alluvium appears to be about at sea level.
Although detailed information is scarce, the head in the Maui
isthmus is known to be low, from 2 to about 5 feet above sea level.
In about 1956 the East Maui Irrigation Company installed water stage
recorders to measure head simultaneously over parts of the Maui isthmus.
These measurements, which were continuous, showed that there was very
little change in head relative to contemporaneous daily or weekly sea
level, except in the drawdown cones of the wells, which are large. Major
apparent changes in head of about 0.7 feet resulted from seasonal changes
in mean sea level (D. Cox, personal communication).
A cooperative effort of the Hawaiian Commercial and Sugar Company,
the U.S. Geological Survey, and the Water Resources Research Center on
December 5, 1970, succeeded in measuring water levels on the Maui isthmus
concurrently at selected wells and shafts during a two-hour period. The
results of this survey are shown as the water-level contours in Figure 5.
It should be emphasized that the water-level contours in Figure 5 are
uncorrected for tidal fluctuations, which are as great as one foot or
more near the shore, and thus, represent the water-table configuration
GEOLOGIC LOGS OF' RECHAFbLOGIC LOGS OF' RECHARGE WELLS IN
IS' ::::ASED
EAST KAHUWI AR WEST KAHULUI AREA
WELL 10 KAllAl ST.
{ ELE~.2e'
:LL I HOLUA AVE.
11.+93'
WELL 2 349 HOLUA AVE.
WELL :3 KUNU PLACE ELEII.+105'
?
~A LEVEL-Jm----------------------Il~-----------_t_1;-------
• • '. • • .. • • • · . • • -54'
-? .31'
VVEST ~.-~----------Ieoo· ----------2000·
I~trr:~ttt] SAND
~DIRT ROCK
A CINDERS
SAND a CLAY
ROCK a CIND
~ DIRT; ROCK a
FIGURE 4.~I).
___________ ~~ EAST
21
only at a specific point in time. It is to be expected that the water
level contours change with variations in draft and recharge, but it seems
reasonable to assume that the general configuration of the water-table
throughout the year is probably approximately represented by the map
(Fig. 5).
Water levels in the vicinity of the Wailuku and to the west are
considerably higher than in the rest of the Maui isthmus, and range from
20 to 30 feet above sea level. This contrast in heads indicates the
presence of a hydrologic boundary between the Wailuku basalts and the
Haleakala lavas and suggests that the direction of ground-water flow is
from the Wailuku basalts into the Haleakala lavas.
Despite the high permeability of the sand dunes, which cover much
of the Kahului area, and low runoff, recharge to the basal lens from
local rainfall is thought to be small. Furthermore, the low rainfall and
the low head in the area indicates that normally only brackish water should
occur. However, large amounts of runoff and imported irrigation water, as
well as subsurface interflow, all primarily from West Maui, are apparently
recharging the Haleakala lavas in very large amounts (Bowles, 1970).
Consequently, as a result of hydrologic investigations accompanying the
Kahului Development Company's recharge project (Bowles, 1970; Hargis,
1971), it has been discovered that an unusually thick lens of fresh water
occurs under the low heads found in this area and that, furthermore, a
relatively large seaward flow of fresh water likewise occurs. For example,
salinity profi~es from the Kahului Development Company test well, where
the head is approximately 3 feet above sea level, show a zone of fresh
water (250 ppm Cl or less) at least 80 feet thick (Fig. 6).
Previous pumping and injection tests on wells at Maui Land and
Pineapple Company have defined the high permeability of lavas in this
area. Preliminary data from KD-l confirmed these high permeabilities and
suggest that horizontal permeability might be as great as 10 times
vertical permeability (Bowles, 1970). In addition, tidal fluctuation in
wells at Maui Land and Pineapple Company (Fig. 7) likewise indicate very
high horizontal permeability.
DESIGN AND OPERATION OF THE DISPOSAL SYSTEM. The Kahului Development
Company storm disposal system is designed to provide a storm drainage for
22
14 o
MAAL.AEA BAY
• SHAFT
o DRI LL ED WELL
" WATER-TABLE ·O,ELEVATION IN FEET
ABOVE SEA LEVEL
I: 62,500
FIGURE 5. GROUND WATER LEVEL CONTOUR MAP OF THE MAUl ISTHMUS.
Hl5
SEA J ••••••••••••••••••••••••••••••••••••••••••••••••••••••• GROUNO WATER l-EVEL. 13-L.EVEL. .... -
-25
-50
-75
.... -100
1&1 1&1 IL
-125
-150
-175
-200
-225
-250 ao 50
./" I , \ t I
'" I 1.
1/1..,/71 THIEF SAMPL.ES
A--.II.--o 8/70 SAIL.EFt AND THIEF SAMPL.ES
" , '-------....... _---
100
o .......... ~ .............
PFtOPOSED CASING DEPTH
FOFt FtUNOFF DISPOSAL. WEL.L.S
250 500 1000
-------~ '1
10,000
CL.- CONCENTFtATION IN PPM
19,000
FIGURE 6. CHLORIDE CONCENTRATION VERSUS DEPTH IN TEST HOLE KD-l (DATA FOR 6/70 FROM S. BOWLES).
N tN
"3.B
~3.e
.1,3.4
+3.2 .J W > W 1-3.0 .J
~ .e.2 W CD
0 +e.o
I-
W 1-5.B
> ~ ~5.6
.J W 0: +5.4
I-~0.4 W
W b..
~0.2
.J W SEA ~ LEVEL .J
-0.2 0: W I- ~3.0
~ 1-2.0
+1.0
SEA LEVEL
N M
" 112/70
N M N M N M N M N
11113/70 11114170 11/15/70 11/19/70 11/17/70
M N
TIDES IN SHAFT 13
(NOTE CHANGE IN SCALE)
TIDES IN WELL 20-A
(NOTE CHANGE IN SCALE)
TIDES IN WELL 20-C
(NOTE CHANGE IN SCALE)
PREDICTED TIDES AT KAHULUI
HARBOR (FROM NATIONAL
OCEANIC AND ATMOSPHERIC
ADMINSTRATION)
M N M
11119170 11/19.'70
FIGURE 7. TIDAL RESPONSE OF SHAFT 13? WELL 20-A? AND WELL 20-C? COMPARED TO TIDES AT KAHULUI HARBOR.
N .j::..
25
an area of approximately 400 acres zoned for residential use. The system
consists of a conventional storm drain and collection network, which is
connected by about 0.5 miles of 72-inch pipe to a 2.7 million cubic foot
capacity collection basin containing four deep disposal wells (Fig. 8).
The collecting basin was designed to have a storage capacity of 2.7 million
cubic feet so that its capacity will be adequate to hold the storm water
if the disposal wells fail to operate at the expected injection rates.
Total runoff from the design storm was computed to be 2.5 million cubic
feet, based on a design storm with a 10-year recurrence interval using
the rational formula according to standards established for the City and
County of Honolulu (R. Hayashi, personal communication, 1971).
The four disposal wells are located in pairs in two separate concrete
chambers constructed on either side of a drainage pipe outlet. The loca
tion of the wells and chambers, relative to the drainage pipe outlet
(Fig. 9), should place the wells in a backwater area as shown by the
circulation pattern (sketched in the same figure), which will deposit
sand and silt in areas away from the wells. This will prevent gravel and
debris from being washed directly into the well chambers. Storm runoff
will enter the wells through a siphoning elbow after passing through a
screened outer chamber (Fig. 10). No provision has been made to hold the
water in settling basins in order to dispose of the suspended matter.
The four wells have l6-inch inner diameters and are 280 feet deep
from the finished grade, which is six feet above sea level. The upper
130 feet of each well is cased with l6-inch diameter casing to prevent
the introduction of storm water into the fresh water that occurs to a
depth of about 100 feet below sea level. Since a dense basalt zone occurs
at a depth of 120-160 feet below sea level, the casing should prevent the
upward movement of injected water. Storm runoff injection will then occur
through the 150 feet of open hole between 124 and 274 feet below sea
level.
The calculated capacity of 3000 gallons per minute for each of the
four finished disposal wells is based on the results of a pumping test
of the l2-inch test hole KD-l drilled at the site in June 1970. Assuming
an injection rate of 3000 gallons per minute (6.7 cfs) for each of the
four effluent wells, approximately 27 hours will be needed to inject the
2.5 million cubic feet of runoff generated by the design storm.
, \ ~ '\
. Baldwin I • High School ~ .. \ - 1'\ , \,'
!eu:, I
/
AVE
; J LA"'E
"} ,r; " /
" .")
FIGURE 8. LOCATION OF KAHULUI DEVELOPMENT COMPANY'S STORM RUNOFF DISPOSAL SYSTEM (FROM INFORMATION AND DRAWINGS SUPPLIED BY R. HAYASHI).
27
LEGEND: -----:;z:. .. -32~ GROUND CONTOUR IN FEET
o WELL
FLOW PATTERN IN BASIN
SCALE:
," = 100'
32' ____ _
SOUTH HINA AVENUE
FIGURE 9. PLAN OF KAHULUI DEVELOPMENT COv1PANY'S COLLECTING BASIN AND DISPOSAL WELLS (FROv1 DRAWINGS SUPPLIED BY R. HAYASHI).
28
STEEL GRATING
GENERAL OUTLET
PLAN
(NO SCALE)
STEEL GRATING-...J.+-++++
I •
STEEL GRATING~~++++
I •
DRAINAGE PIT PLAN
IS'
00
• I
.1
--4---STEEL PLATE COVER
_--STEEL PLATE
-In++~f-H~~!I~-----:::S:-'''' COVER
(NO SCALE)
~I I I I I
I----II-IS" WELL
FIGURE 10. DETAILED PLAN OF KAHULUI DEVELOPMENT COMPANY'S INJECTION WELLS (FROM DRAWINGS SUPPLIED BY R. HAYASHI).
29
EFFECTS OF RECHARGE. Although this recharge facility is not yet in opera
tion so that actual performance data is not available, it is of critical
importance to estimate the possible effects recharge of storm runoff
might have on the ground-water body. Essentially three types of informa
tion were of primary interest: the injection capacity of the wells
estimated from pumping and injection tests on the 12-inch test well (KD-I)
and one of the completed l6-inch disposal wells (KD-2), the probable
movement of the recharge water explored by injection tests and water
level and water quality monitoring, and the qualitative effects of the
injected storm runoff on the ground water investigated by chemical and
biological analyses of the storm recharge and receiving waters.
In order to obtain more detail~d hydrologic and geologic informa
tion, the l2-inch diameter test hole was drilled and tested on the site
of the proposed collecting basin in June of 1970. This test well was
drilled from an elevation of about 30 feet above sea level to a depth
of 220 feet below sea level. The geologic log, shown in Figure 2,
indicates about 30 feet of sand, gravel, clay, and small boulders resting
on basalt at sea level. Thirty-six feet of temporary casing was installed
to prevent the sand and other sediments from caving into the hole during
subsequent testing and excavating of the collecting basin. Furthermore,
although not shown in Figure 3, an 11 foot thick dense hard rock was
indicated on the driller's log at a depth of 135 feet below ground level
(Bowles, 1970). If this strata, which is probably a dense. ~a flow of
relatively low permeability, has any degree of lateral extent, it should
greatly restrict vertical ground-water flow. All injection will be
restricted to the portion of the wells below this level. The depth of
this hard rock also roughly corresponds to the bottom of the fresh water
lens in the vicinity of the recharge basin. Following completion of
the test hole, both pumping and injection tests were run.
On June 20, 1970, a step-up pumping test was conducted to give an
indication of the aquifer permeability and its effects on well hydraulics.
A maximum rate of 3000 gallons per minute was pumped from the l2-inch
hole with no measurable drawdown. An air line and recorder were used to
measure the water level. Although the test results show it is possible
to pump 3000 gallons per minute from 214 feet of l2-inch hole with no
drawdown, it does not immediately follow that 3000 gallons per minute
30
can be injected into the same hole with no head bUild-up. The chemical
quality of the injected water and the mechanics of injection must be con
sidered, particularly with regard to sediment load and air entrainment.
The injected storm water will carry some sediment into the wells that will
decrease the capacity of the aquifer to transmit water, but the magnitude
of the decrease is impossible to predict as this time.
Further evidence of high rates of horizontal permeability is shown
by salinity data collected at different pumping rates (Fig. 11). The
~ n.. Ii
370
340
310
PUMPING RATE IN GPM
--500 ---'loI)I.;,..(- --700 -----;)I+oI(E- t -*t*3000-"*-700~ 1520 2400
Z280
w o 1l:260 o J I o
230
200 ~~~--~--~----~--~ __ ~ __ ~~~ ____ L-__ ~ __ ~ __ ~ __ o 60 90 120 150 180 210 240 270 300 330 360
TIME AFTER PUMPING STARTED IN MINUTES
FIGURE 11. CHLORIDE CONCENTRATION VERSUS PUMPING RATE AND TIME IN TEST HOLE KD-l (AFTER S. BOWLES, 1970).
pump intake was set at a depth of 75 feet, or approximately 45 feet below
sea level, and 48 feet below the water table. The chloride concentration
of the water at this depth was 80 ppm (Bowles, 1970). It can be seen
clearly from Figure 11 that the chloride concentration of the water is
directly related to the pumping rate, although the relative changes in
chloride concentrations for different pumping rates is relatively small.
This would indicate that water of higher salinity from zones deeper in the
aquifer is not moving into the well in significant amounts, even at the
31
higher pumping rates. Instead. the aquifer at shallower depths nearer
the pump intake is able to supply the increased demand with water of low
salinity.
Following the pumping test on June 20. 1970. approximately 230,000
gallons of water from the County of Maui's domestic supply was injected
into the test hole at an average rate of 320 gallons per minute over a
13-hour period. The chloride concentration of this water was 40 ppm
(Bowles, 1970). No head bUild-up was detectable in the test hole at any
time during the injection (Bowles. 1970). Following this injection, the
hole was pumped for a little over 7 hours at a rate of 700 gallons per
minute. The chloride concentrations of the water pumped are shown in
Figure 12 at test 1. They are essentially the same as pumped from the
hole at 700 gallons per minute before the injection.
280
260
240 1 0. 0. 220
~ 200
W o II 180
o ..J l: 160 o
1000 GALLONS PUMPED 42 84 126 168 210 252
/:s; til 6 TEST I JUNE 21, 1970
• • • TEST 2 JUNE 22, 1970
140~----~------~----~------~ ____ ~ ______ ~ ____ ~ ____ ~~
4 5 6 7 8 HOURS PUMPED
FIGURE 12. CHLORIDE CONCENTRATION VERSUS AMOUNT OF WATER PUMPED AND TIME IN TEST HOLE KD-l FOLLOWING INJECTION OF FRESH WATER (APTER S. BOWLES, 1970).
Water from the County of Maui's domestic supply was again injected
into the hole at an average rate of 320 gallons per minute for the next
16 hours. A total of over 300,000 gallons was injected over this time.
The test hole was then pumped again at an average rate of 700 gallons
32
per minute, but this time for only four hours. A total of almost 170,000
gallons was extracted. The chloride concentrations of the water pumped
during this 4-hour period are shown in Figure 12 as test 2. The water
appears to be slightly fresher.
The salinity data presented in Figure 11 would again suggest a high
permeability for the aquifer. The injected water of 40 ppm chloride
evidently moves quickly away from the well and mixed with the native
ground water. Even pumping immediately after the cessation of injecting
does not reveal any appreciable freshening of the pumped water.
Well KD-2, the first of four l6-inch diameter wells to be drilled
in the collecting basin, was completed in March 1971. It was drilled
from an elevation of approximately 10 feet above sea level to a depth
270 feet below sea level and is cased to a depth 120 feet below sea level.
In order to obtain better data on the recharge capacity of a completed
disposal well, pumping and injection tests were conducted on this well.
On March 27, 1971, well KD-2 was pumped at a rate of 5500 gpm fur
about 3 1/2 hours. The 5500 gpm pumped from KD-2 was injected into test
hole KD-l to obtain a better estimate of the injection capacity for the
disposal wells than was obtained from the limited injection tests conducted
earlier on KD-l. Also, since KD-l is cased only to sea level, it was
possible to trace the movement of the saline water pumped from KD-2 as
it entered the fresh water zones of the aquifer near sea level through
test hole KD-l and useful information could be obtained to estimate the
rate of movemen~ of injected storm runoff in deeper zones of the aquifer.
The bottom of the casing in KD-2, at a depth of 120 feet below sea
level, is located in the transition zone between fresh and salt water
and has a chloride concentration of about 10,000 mg/l (Fig. 9). Two
samples obtained from a tap on the pump during the pumping test of KD-2
yielded a chloride concentration of 12,600 mg/l. This represents a
mixture of the water drawn from between 120 and 270 feet below sea level
in well KD-2. As shown in Figure 6, water with 19,000 mg/lchloride is
reached at a depth of about 200 feet below sea level. It would appear
that most of the water pumped from KD-2 during this test was drawn from
the transition zone and little mixing occurred with water deeper in the
aquifer.
33
A recording conductivity bridge was placed in shaft 13 (owned by
Maui Land and Pineapple Company), a distance of 1200 feet from the injec
tion site (for location see Fig. 1), to detect any changes that might
result from movement of the saline water injected into the fresh water
lens. The ground water contour map developed for the area indicates, however, that the direction of flow is to the northeast, and not to the
north toward the shaft (Fig. 5). In order to establish a gradient between
the injection site and shaft 13, the shaft was pumped at a rate of 2800
gallons per minute from 3 P.M. on March 26 until 7 P.M. on March 27,
with a drawdown of 1.5 feet in the shaft. No change in salinity that
could be definitely be attributed to the injection test is indicated by
the conductivity record obtained from the shaft (Fig. 13).
Well KD-3, only 30 feet from the injection site and directly
down-gradient from it, was sampled periodically during the testing and
analyzed for chloride content. At the time of the injection and pumping
tests on March 27, this well had a depth of 38 feet below sea level.
Although no measurable change in water level was observed during the
pumping and injection test, bailer samples from KD-3 revealed a signifi
cant change in chloride concentration within a relatively short time
after injection began.
A diagrammatic sketch of the testing set-up is presented in Figure
14. Brackish water from the transition zone was pumped from well KD-2
and piped directly into well KD-1 at a depth of ten feet below sea
level. There is little doubt that some of the water injected into KD-l
returns to KD-2 and is re-cyc1ed through the system, but it is also
evident from the salinity data collected from KD-3 that significant
amounts of the saline water are entering the fresh water lens just below
sea level in KD-1. This will not be the case, of course, in the finished
disposal wells, as they will all be cased to approxim~te1y 120 feet
below sea level.
The salinity data collected in well KD-3 is presented in Figure 15.
The first saline water to reach KD-3 requir~d less, than 32 minutes to
traverse the thirty feet between KD-l and KD-3. The chloride concentra
tion at KD-3 continued to increase throughout the injection test, and
appears to have leveled off at 1600 mg/l.
A summary of the head measurements taken in well KD-1 and KD-2
during the pumping and injection test (Fig. 14), shows the water levels
~ o .... fD o I
800
~ L b r
::l.700 -
z
>-I-:::600 I-o ::J o Z o o
3/25/71
~ 6 ~ 6 ~ 6 ~ 6 ~ 6 ~ 6 ~ 6 ~ 6 ~ 6 ~
3/26/71 3/27/71 3/28/71 3/29/71 3/30/71
TIME IN HOURS
FIGURE 13. CONDUCTIVITY IN SHAFT 13 FOR THE PERIOD MARCH 26-30, 1971, DURING INJECTION AND PUMPING TEST OF WELLS KD-1 AND KD-2.
(;:I -1:>0
ELEVATION 5500 GPMI<D_2 IN FEET I<O-~ I<D-I
+10 ~ 0
-10 'If if
if
I .....-.-
I II I
t I I I I ~
I I I 'II 30' ~
I -220
A -270
..... 5· ...
ORIGINAL WATER LEVEL IN KD-l AND KD-2
+a -----------------------------------_______ _ ••••••••••••••••••••••••• 0..-00
..J +2 W
••• 1'\. o •••• .() 000·...,
> W ..J
« W (J)
o I-
w > ~ ..J W II:
o « 11.1 I.
+1
o
-I
-2 I
-3 I I -----....
100
.. --a KD-2 (PUMPING) 0 .... 0 KD- I (PUMPING)
t ......... -&
I I I I I ...... RECOVERV .......
TIME IN MINUTE.S TIME IN MINUTES AFTER
BEFOR PUMP STARTED PUMPING STOPPED
B
35
FIGURE 14. (A) DIAGRAM OF PUMPING AND INJECTION TESTS OF WELLS KD-l AND KD-2 ON MARCH 27, 1971 (ARROWS INDICATE GENERAL DIRECTION OF WATER MOVEMENT). (B) SUMMARY OF WATER LEVEL MEASUREMENTS IN WELLS KD-l AND KD-2 DURING THE PUMPING AND INJECTION TESTS.
10 I
0 '!J.
~ J
" C) ~
Z
J 0
36
2000
STOP IN..IECTION AT KD-'\
1000
500
100
IN.JECTION .l START
AT KD-I
10~--~----~----~--~ ____ ~ ____ ~ __ ~ ____ -L ____ ~ __ ~L-____ _
9 10 II 12 :2 3 4 5 6
TIME IN HOURS ON MARCH 27, 1971
FIGURE 15. CHLORIDE CONCENTRATION VERSUS TIME IN WELLS KD-3? DURING PUMP AND INJECTION TESTING ON WELLS KD-l AND KD-2 ON MARCH 27? 1971.
o ~
A.LIAI
37
in both wells dropped as soon as pumping began in KD-2 with the coincident
beginning of injection in well KD-I.
co~stant throughout the test at 5500
is a negative injection head in well
The pumping and injection rates were
gallons per minute. There apparently
KD-l, probably owing to the fact
that injection of saline water into the fresh water zone in KD-l dis
places the head equilibrium downward. Thus we see a net drawdown in
KD-l, the injection well, where we would expect to see a head build-up.
An interesting note was that as soon as injection was halted in KD-I, the
water level dropped several more tenths of a foot, and then slowly began to
recover (Fig. 14). This drop probably represents the dissipation of the
injection head that had developed in the hole, about 0.5 feet.
Neither well recovered immediately to its original water level, due
in part to the salinity chan~es caused in the well column by pumping and
injection. Injection of the saline water into the fresh water zones in
well KD-I caused an increase in the density of the fresh water, which in
turn caused the water level to recover slowly to its original level as
the saline water is dispersed into the fresh water zone. On the other
hand, the fresh water was removed from the casea well KD-2, and the head
in this well eventually will recover to sea level or a little higher than
sea level, depending on the relative densities of the brackish water in
jected into the well column and the more saline water at lower depths.
This test demonstrated that the disposal wells should be able to
inject at rates of at least 5500 gallons per minute, when injecting
sediment-free water, with a very small injection head of probably less
than one foot. The test also demonstrated that high rates of movement
can be expected for the injected water in the aquifer close to the in
jection wells. The data obtained indicates a gross velocity in the im
mediate vicinity of the well of approximately one foot per minute, which
indicates extremely high horizontal permeability of the aquifer in this
area.
In addition to the determinations of recharge capacity and rates
of water movement, water quality is of major importance in the storm run
off disposal scheme. The effects of the storm runoff to be injected at
the Kahului Development Company's disposal wells on the ground water
quality in the area and the possible effects of injected runoff on water
users down gradient from the injection site were of major interest in
this study. Consequently, ground water samples were collected from wells
38
20-A, 20-C, 3-A, KD-l and shaft 13. Storm runoff samples were also col
lected in the study area during heavy rains in the month of January (for
location see Fig. 1). The wells and shaft 13 can continue to be monitored
during future storm runoff injection at the Kahului Development Company's
disposal site to detect any changes in water quality that might result
from the storm runoff injection.
The ground water and storm runoff samples obtained in January were
analyzed for chloride, nitrate, phosphate, chemical oxygen demand, total
solids, dissolved solids, and fecal coliform. Chloride is used as an
indicator of general \'later quality, and was used earlier to define the
limits of the fresh water lens. Nitrogen in the form of nitrate is a major
nutrient for vegetation and is essential to all life (Hem, 1970). Phosphate
is also an important nutrient for plant growth, and both nitrate and phos
phate are major constituents in commerical fertilizers. In addition,
phosphorous and nitrogen are present in animal wastes and can be used as
indicators of sewage contamination. Nitr!te has been widely used in
Hawaii to indicate the presence of return irrigation water in the sub
surface, and, as indicated earlier in this report, significant enrichment
of ground water bodies with respect to nitrate has been found on Oahu by
Visher and Mink (1964) and on Maui by Tenorio, et al .. ~ (1969, 1970).
Phosphorous enrichment of ground water bodies in Hawaii by percolating
irrigation water has not been demonstrated. It appears that phospnorous
is fixed by most Hawaiian soils and is not leached by percolating irriga
tion water in significant amounts. Chemical oxygen demand is an indicator
of the organic load in sewages and wastes (Sawyer and McCarty, 1967). In
this study, its primary use was to indicate the organic load in the runoff
samples collected from the study area.
Although determination of total solids and dissolved solids were of
indirect importance in this study, it is critical in the computation of the
suspended solid content. The suspended solids concentration that could be
expected in the storm runoff recharged through the wells is of vital
importance when trying to predict the performance of the wells. A high
sediment load in the injection water will most likely cause a decrease in
the capacity of the wells over a length of time, and may even clog them
completely.
Fecal coliforms are present in the intestinal tract of warm-blooded
39
animals, and can survive for only a few days once they have been passed
out of the animal's body. Their presence in water indicates recent contact
with human sewage or animal wastes, and indicates a strong possibility that
other pathogenic organisms are present in the water.
The nitrate concentration of samples from the fresh water zone in
the Kahului area is of interest in determining the origin and source of
recharge of the ground water body in that area. Samples from the fresh
water zone were obtained at shaft 13, well KD-l, and well 3-A, and these
analyses together with analyses of water from shafts 24, 19, 18 and 16
of the Hawaiian commercial and Sugar Company (HC & S) obtained by Tenorio,
et aZ.~ (1969), are presented in Table 1. (The location of these shafts
is shown in Figure 5.) The HC & S shafts are all surrounded by irrigated
sugar cane fields and their nitrate concentrations range from a low of 1.6
mg/l to 20 mg/l, and average about 15 mg/l. In contrast, shaft 13, has
an average of 2.0 mg/l and a range of 1.6 mg/l to 2.2 mg/l and well KD-l
has an average of 1.4 mg/l and a range of 1.3 to 1.6 mg/l. Thus, both
shaft 13 and well KD-l contain significantly less nitrate than the shafts
of the HC & S Company, which receive recharge from percolating irrigation
return water. Well 3-A exhibited significantly higher nitrate concen
trations than the other sampling points in the study area, averaging
5.8 mg/l and ranging between 3.5 and 7.0 mg/l. This well is one of the
county's street runoff disposal wells and the higher nitrate concentra
tions may be the result of a leaky sewer line, as discussed earlier.
Well 20-C, which penetrates through the fresh water lens and pumps
from the salty zone, has markedly lower nitrate and.phosphate levels
than samples taken in the fresh water zone. None of the samples taken
from well 20-C contained any detectable nitrate, the threshold for
detection being 0.5 mg/l. Similarly, the phosphate concentration of all
samples taken from the salty zone was a uniform 0.19 mg/l (Table 1).
Wells 20-A and KD-l, which also penetrate through the fresh water lens
and into the salty zone, exhibited correspondingly low nitrate concen
trations of less than 1.0 mg/l, but yielded phosphate concentrations
ranging from 0.25 mg/l to 0.90 mg/I. Well 20-A receives wastewater
from the Kahului cannery of the Maui Land and Pineapple Company, which
could account for the slightly higher phosphate and nitrate concentrations
than those found in well 20-C. Two samples of cannery wastewater, which
40
consists of a mixture of water pumped from shaft 13 and wells 20-8 and
20-C, were analyzed and the results are presented in Table 1. The
nitrate concentrations are low, probably representing a dilution of the
nitrate in shaft 13. On the other hand, the phosphate concentrations
in the wastewater are several times greater than the levels present in
shaft 13 and wells 20-8 or 20-C. This explains the phosphate enrichment
found in samples taken from the salty zone in well 20-A. The wastewater
evidently picks up some phosphate in the cannery at some point in its
operation.
Data collected on Oahu by Visher and Mink (1964) is compared in
Figure 16 to data on nitrate levels collected on Maui during the study
reported here and by Tenorio, et at., (1969). Shafts 3 and 14 on Oahu
and wells in Area lIon Oahu are all located in irrigation areas and have
nitrate concentrations ranging from 7.5 mg/l at shaft 14 to 8.7 mg/l at
shaft 3. Shafts 24, 19, and 18 on Maui, also located in irrigated areas,
have nitrate concentrations ranging from 14 to 18 mg/l. Among the
Kahului wells sampled during the current study, only well 3-A approached
these higher concentrations. In contrast, uncontaminated basal water on
Oah~ has a nitrate concentration of about 1.1 mg/l and uncontaminated
stream water has less than 0.5 mg/l nitrate. Four samples collected from
the upper reaches of lao Stream on West Maui and analyzed by Tenorio,
et at., (1969), had nitrate concentrations ranging from 0.0 to 2.7 mg/l.
This is considered to be uncontaminated stream water. The low nitrate
values at shaft 13, wells KD-l and 3-A indicate that any return irrigation
water reaching Kahului from the irrigated lands to the south and east
is obscured by mixing with uncontaminated basal water, probably underflow
from the valleys of West Maui. Although the study area in Kahului is
sewered, it is likely that some leaks occur in the sewer system and small
amounts of nitrate reach the ground water in the area from this source,
as well as from fertilizers used locally on lawns, etc.
A single sample obtained on February 24, 1971, from shaft 13 of the
Maui Land and Pineapple Company was analyzed for tritium and yielded
a value of 17.2 ± 3.1 tritium units (1 tritium unit = 1 TU = 1 atom
tritium per 10 18 atoms total hydrogen; Davis and DeWiest, 1966). For
comparison purposes, average tritium levels for rain on Oahu are 22.0
TU in the summer and 12.0 TU in the winter. The Wahiawa and Halawa
1
41
UNCONTAMINATED BASAL WATER, OAHU
UNCONTAMINATED STREAM WATER, OAHU
SHAF"T 14, IRRIGATED AREA, OAHU
SHAF"T 3, IF.tRIGATED AREA, OAHU
AREA II WELLS. IRRIGATED AREA, OAHU
STREAM, UNCONTAMINATED, WEST MAUl
SHAF"T 24, IRRIGATED AREA, CENTRAL MAUl
SHAF"T 19, IRRIGATED AREA. CENTRAL MAUl
SHAF"T lB. IRRIGATED AREA, CENTRAL MAUl
SHAF"T la, KAHULUI, MAUl
WELL KD-I, KAHULUI, MAUl
WELL 3-A. KAHULUI, MAUl
NOa IN MGIL
FIGURE 16. NITRATE CONCENTRATIONS OF GROt...t.lD WATER, t...t.ICONTAMINATED RAIN, AND STREAM WATER FROM MA.UI AND OAHU (ALL OAHU DATA ARE FROM VISHER AND MINK, 1964, AND MA.UI DATA FOR lAO STREAM, AND SHAFTS 18, 19, AI'IID 24 ARE FROM TENORIO" et aZ • .) 1969).
42
shafts on Oahu have yielded values less than 3.0 TU for basal water,
and wells in Honolulu have values less than 1.0 TU (T. Hufen, personal
communication, 1971). The high tritium level in the Maui sample would
probably indicate that the water is rapidly-circulating meteoric water.
Phosphate concentrations in all samples from the study area were
less than 1.0 mg/l and differences between the Kahului data and data from
other shafts on the isthmus are not significant.
Samples from wells 3-A and KD-l and shaft 13 were also analyzed for
chemical oxygen demand. Well 3-A exhibited a chemical oxygen demand
significantly higher than the other two sampling points in the fresh water
zone (Table 1). This would indicate a higher organic load in 3-A than in
shaft 13 or well KD-l, which could again be attributed to runoff from the
surrounding residential area recharged into the well. Chemical oxygen
demands of samples obtained from deeper zones in the aquifer, which contain
water of essentially the same composition as sea water, are one order of
magnitude larger than values obtained for samples from the fresh water
portion of the lens. These higher values reflect the high total solids
concentrations in these deeper samples (Table 1).
Of the five samples taken at the 206-foot depth in well KD-l, only
the January sample shows the level of chloride concentration that would be
expected ~t that depth, according to the chloride profile presented in
Figure 6. The remaining four samples taken on March 11, 12, 13, and 14
yielded chloride levels less than 10,000 mg/l (Table 1). This apparently
puzzling situation is most likely the result of several acre-feet of storm
runoff which drained into this well during heavy rains in late January.
In addition to the chloride concentrations, the diss~lved solids
concentrations for the four samples obtained on March 11, 12, 13, and 14
from KD-l also exhibit a marked decrease when compared to the sample ob
tained on January 14 (Table 1). At the time of sampling, these samples
were noted to be very turbid, which would indicate- that a considerable
amount of suspended matter was carried into KD-l by the storm runoff re
charged through the well in late January.
The results of the fecal coliform analyses conducted during this
study are presented in Table 2. All of the wells except for 3-A, the
shallow county runoff disposal well, were free of fecal coliform. Further
more, both the effect of dilution of the storm runoff by the ground water
and hostile environment presented by the highly saline ground water at depth
TABLE 2. SUMMARY OF ANALYSES FOR FECAL COLIFORM IN GROUND WATER AND STORM RUNOFF AT KAHULUI; MAUl.
FECAL COLIFORM SAMPLE DATE COLONIES PER 100 ML.
SHAFT 13 1/7/71 a 1/12/71 a 1/13/71 a 1/14/71 a
WELL 20-C 1/7/71 a 1/12/71 a 1/13/71 a 1/14/71 a
WELL 3-A 1/13/71 200
WELL 20-A 1/12/71 a 1/13/71 a
UHU ST. RUNOFF 1/13/71 a 1/14/71 a
ALEO PL. RUNOFF 1/13/71 9,000
ONEHEE AVE. RUNOFF 1/14/71 1,000
43
would tend to reduce the hazard represented by any high fecal coliform
counts found in this study.
Little information is available on the quality of storm runoff from
suburban residential areas in Hawaii. Several studies have investigated
the quality of urban storm runoff in the United States in recent years, among
them Bryan (1970) who analyzed storm runoff from the Durham, North Carolina
basin. This study included residential, industrial, and commercial areas
that are not similar to the residential area studied in Kahului, Maui, but
the data is presented for purposes of comparison. Data obtained from the
Salt Lake area on Oahu by a study conducted by the Water Resources Research
Center as well as that compiled by Bryan (1970) from Durham, North Carolina,
and additional information obtained from other sources is compared to the
analyses of storm runoff from Kahului, Maui in Table 3. The locations at
which the runoff samples were collected in Kahului are indicated in Figure
1. The Kahului runoff yielded consistently lower values than those re
ported by Bryan and others for urban runoff in the mainland United States,
but the Kahului results are very similar to those for the Salt Lake area
on Oahu. However, the chemical oxygen demands measured for the Kahului
samples were much lower than for those on Oahu, indicating low organic
LOCATION
KAHULUI, MAUl
TABLE 3. COMPARISON OF STORM WATER QUALITY FROM A SUBURBAN AREA IN KAHULUI, MAUl, WITH RESULTS REPORTED BY OTHERS. DATA FOR SALT LAKE, OAHU, COURTESY OF R. CHING, UNIVERSITY OF HAWAII (AFTER BRYAN, 1970).
TOTAL DISSOLVED SUSPENDED Cl NOs PO ... COD SOLIDS SOLIDS SOLIDS
mg/l mg/l rug/l rug/l mg/1 mg/1 mg/l
MEAN 3.9 0 0.10 21.3 257 73 200 SUBURBAN STORMWATER RANGE 3.0-6.5 .01-0.28 12.3-48.3 174-404 34-194 80-357
SALT LAKE, OAHU MEAN 9.5 4.9 341 243 SUBURBAN STORMWATER RANGE 5.0-16.0 (}.7-10.8 149-584 25-595
OURI-IA/'o1, N.C. MEAN 7.7 0.58 179 2730 URBAN STORMWATER RANGE 1.8-237 0.15-2.50 40-600 274-13,800
CINCINNATI, OHIO MEAN 12 1.1 111 227 URBAN STORMWATER RANGE 3.0-428 0.02-7.3 20-610 5-1200
COSHOCTON, OH IO MEAN 1.7 79 313 RURAL STORMWATER RANGE 0.25-3.3 30-159 5-2074
STOCKHOLM, SWEDEN MEDIAN 188 300 URBAN STORMWATER MAXIMUM 3100 3000
FECAL COLIFORM COLONIES PER 100 ML
2,058 0-9,000
0
30,000 7,000-86,000
500-76,000
2-56,000
.j:I.
.j::>.
f ___________________________________ _
45
loads in the Kahului runoff. Suspended solids in the Kahului runoff
ranged from 80 to 357 mg/l. This is equivalent to 12,500 and 55,600
pounds of suspended matter, respectively, for a storm that produces 2.5
million cubic feet of runoff, the amount of runoff expected from a ten
year maximum design storm. The amount of suspended matter that will
actually reach the recharge wells once the system is operational is
difficult to predict. If the amounts of sediment delivered to the wells
is within the computed range, serious clogging problems could result. It
remains to be seen if the predicted circulation pattern in the collecting
basin discussed earlier is effective and allows most of the sediment to
be deposited before the storm runoff enters the wells.
It should be noted that the quality of the storm runoff at the begin
ning of a storm, the so-called "first flush," will differ markedly from the
runoff produced after several minutes of rain. All of the runoff samples
from Kahului analyzed for this study were obtained on consecutive, not
isolated, rainy days and do not represent the first flush. The first flush
dissolves and carries off the soluble salts, dust, and other particulate
matter that has collected. on the ground and paved surfaces since the previous
rain. Material from the first flush is quickly washed away, however, and
the bulk of the storm runoff that will be recharged through the wells can
be represented by the runoff analyses presented in Table 1. Three 100-
square-foot areas in the study area, near the points where the runoff sam
ples were collected, were swept with a broom and the sweepings were dis
solved in one liter of distilled water and analyzed for the same parameters
as the runoff samples. The amount of water used to dissolve the street
sweepings is arbitrary, and is presumed to yield a rough estimate of what
can be expected in the first flush. The results of these analyses are re
ported as sweep one, two and three in Table 1. As the analyses show, the
chloride concentrations for the dissolved sweepings are much higher than
the runoff samples collected: 100 mg/l as compared to less than 10 mg/l for
the runoff samples, but chemical oxygen demands for the sweepings are all
less than 17 mg/l. The dissolved solids in the sweepings are also higher,
in general, than the runoff samples. This would be expected in a first
flush. The street sweepings yielded low nitrate and phosphate values com
parable to the actual runoff samples obtained.
An examination of the chloride concentrations at about the 200-foot
46
depth in wells KD-l (Figure 6), 20-C, and 20-A (Table 1) indicates that the
disposal zone will lie in water having a chloride and total solids concentra
tion eq~ivalent to sea water, roughly 19,000 and 36,000 mg/l, respectively.
This is in marked contrast to the storm runoff which is generally less than
10 mg/l chloride and 500 mg/l total solids, with one exception (Table 1).
The nitrate and phosphate concentrations in the runoff, however, are about
the same as the ground water in the disposal zone. The injected runoff will
then reduce the salinity and total solids concentration of the ground water
in the vicinity of the recharge wells. However, as described earlier alter
nate injection and pumping of the disposal wells show that it is very dif
ficult to recover any of the injected water. The high aquifer permeability
in the disposal zone enables the injected water to move quickly away from
the wells. Fecal co1iforms introduced into the aquifer through the disposal
wells in the salty zone are not believed to present a serious hazard because
dilution effects of the ground water on the storm runoff and the hostile
environment presented by the saline water in the disposal zone should reduce
the hazard represented by the high fecal coliform counts found in the storm
runoff.
CONCLUSIONS
Artificial recharge practices in Hawaii have been summarized by Hargis
and Peterson (1970) as follows:
1. incidental ditch and reservoir leakage and other non-deliberate
recharge of irrigation water,
2. induced leakage from ditches and reservoirs and deliberate
spreading of excess irrigation water,
3. deliberate recharge of fresh water, primarily stream-flow,
through wells, shafts, pits, etc.,
4. storm drainage disposal, usually through wells and pits,
5. disposal of treated sewage effluent, primarily through wells,
6. cesspool seepage, and
7. miscellaneous industrial wastes, cooling water, excess water from car washes, etc.
The recent works 6f Tenorio, et al., (1969, 1970) have provided con
clusive quantitative and qualitative evidence that fertilizer components,
principally nitrates and sulfates, leach into the basal aquifers as a result
47
of application of irrigation water to fields.
The effects of deliberate artificial recharge practices in Hawaii, al
though in many cases of considerable importance locally, have been relatively
minor compared to the recharge incidental to irrigation. However, the in
creasing practice of subsurface disposal of storm runoff, sewage effluent,
and other wastewaters may present a potential contamination hazard to some
basal ground-water bodies.
Of particular interest in this study is the injection of storm runoff
into the basal ground-water bodies at Hilo, Hawaii and Wailuku and Kahului,
Maui. Virtually no quantitative data are available from the shallow County
wells in Hilo and Wailuku and Kahului, however, the amount of recharge is
known to be small. Qualitative information from these wells likewise is
sparse, however, the data which is available (chemical and biological anal
yses of water samples from well 3-A) show high fecal coliform counts after
recharge of storm runoff. Because these wells are shallow, and recharge is
directly into the freshest portion of the basal lens, a potential contamina
tion hazard from these wells exists, which should be further investigated.
In addition to the County wells, the Kahului Development Company re
charge facility at Kahului is planned to inject storm runoff into the ground
water body, but at a depth below the fresh water lens. Consequently, the
freshest portion of the lens will not be endangered and the hostile environ
ment presented by the saline water in the disposal zone should reduce the
hazard represented by the high fecal coliform counts obtained for some
runoff samples from the Kahului area.
Pumping and injection tests of wells KO-l and KD-2 indicate that the
finished disposal wells should be able to inject at rates in excess of
5500 gpm, if significant clogging from sediment does not occur and if hy
draulic interference between the four wells operating simultaneously is not
significant. Data collected indicate that suspended solids concentrations
may be as high as 55,600 pounds of sediment for the maximum design storm,
which could greatly reduce the efficiency of the disposal operation. How
ever, pumping and injection tests of test hole KO-l both before and after
recharge of several acre feet of storm runoff in late January 1971 do not
reveal any decrease in capacity in spite of high sediment loads in the in
jected runoff.
The anticipated effects of injecting storm runoff into the ground-water
48
body should be to decrease the dissolved solids concentration and increase
the suspended solids load of the ground water in the vicinity of the Kahului
Development Company wells.
RECOMMENDATIONS
Because many problems unearthed in the course of this investigation
are beyond the scope of the present study, the following recommendations
for further research are made:
1. More detailed quantitative information should be gathered at
all locations where artificial recharge, deliberate or otherwise,
is known to be practiced in Hawaii. In particular, the effects
on ground-water quality should be closely studied in areas where
subsurface disposal of storm runoff, sewage effluent, and other
wastewaters is practiced.
2. More quantitative and qualitative information should be gathered
to determine the rate of recharge and, even more important, the
chemical and biological effects of recharge of storm runoff through
the shallow county wells at Hilo, Hawaii and Wailuku and Kahului,
M~i.
3. Further testing and monitoring of the Kahului Development Company
recharge facility should include
(i) pumping and injection testing of the disposal wells as
each well is completed in order to define any interference
that might develop between the four wells when they are
operated simultaneously,
(ii) continued monitoring of the water quality at the shaft
and wells of the Maui Land and Pineapple Company to
detect any changes in water quality that might be at
tributed to storm runoff injection,
(iii) measurement of the rate of water movement between the
injection wells and wells of the Maui Land and Pineapple
Company,
(iv) drilling several small diameter test holes near the basin
to the northeast, to make quantitative assessment of the
rate of movement of the injected water in the aquifer as
1
1
49
well as to monitor the dispersion characteristics of the
aquifer (monitoring of such holes would further insure
that the effects of recharge from the Kahului .Development
Company facility would not be confused with possible
deleterious effects from recharge in the shallow Maui
County wells nearby),
(v) collection of more information concerning general storm
runoff quality from the Kahului area, and frequent moni
toring of the quality of the storm runoff actually in
jected into the disposal wells once they become operational,
with special emphasis placed on observing any effects from
sediment loads.
ACKNOWLEDGEMENTS
The authors received cooperation and assistance from many individuals
and organizations during this study. We are especially grateful for the
invaluable exchange of ideas and assistance received from Stephen Bowles
throughout the qourse of this project. Garner Ivey and Ralph Hayashi of
the Kahului Development Company also deserve special thanks for their co
operation and assistance. Financial support from Alexander and Baldwin,
Inc., made possible a portion of the water quality work in this project,
and the authors are most grateful for this support. Francis Fukunaga,
Michael Moline, and other employees of the Maui Land and Pineapple Company,
assisted in water sampling and instrument location and maintenance. Fred
Araki and Stan Funitake of the County of Maui Department of Public Works
assisted in water level monitoring. Theo Hufen provided the tritium
dates. Finally, special thanks are due to Doak Cox for his review
of the entire manuscript and to Reginald Young for his review of the
water quality sections.
50
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