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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