Hydraulic Effects of Recharging the 

Magothy Aquifer, Bay Park, New York, 

With Tertiary-Treated Sewage 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 751-F 

Prepared in cooperation 

with Nassau County 

Department of Public Works 

Hydraulic Effects of Recharging the 

Magothy Aquifer, Bay Park, ,New York, 

With Tertiary-Treated Sewage 

By JOHN VECCHIOLI, HENRY F. H. KU, andDENNISJ. SULAM 

DEEP-WELL AR TIFICIAL-.RECHARGE EXP'ER,IMENTS 

AT BAY PARK, LONG ISLAND, NEW YORK 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 751-F 

Prepared in cooperation 

with Nassau County 

Department of Public Works 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1980 
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary 

GEOLOGICAL SURVEY 

H. William Menard, Director 

Library of Congress Cataloging in Publication Data 

V ecchioli, John. 

Hydraulic effects of recharging the Magothy aquifer, Bay Park, New York, with tertiary-treated sewage. 

(Deep-well artificial-:rtecharge experiments at Bay Park, Long Island, New York) (Geological Survey professional paper ; 751-F) 

Supt. of Docs. no.: I 19.16:751-F 

Bibliography: p. 

1. Water, Underground-New York (State)-Bay Park-Artificial recharge. 2. Sewage disposal in the 

ground-New York (State)-Bay Park. I. Ku, Henry F. H., joint author. II. Sulam, Dennis J., joint 

author. III. Nassau Co., N. Y. Dept. of Public w.orks.IV. Title. V. Series. VI. Series: United States .. 

Geological Survey. Professional paper ; 751-F. 

TD765.V38 628'.36 78-27041 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 

Stock Number 024-001-03291-1 
CONTENTS 

Page Page 

Conversion factors and abbreviations ---------------

Abstract -----------------------------------------

Introduc~on -------------------------------------

IV 

F1 

1 

1 

2 

2 

3 

3 

4 

4 

4 

5 

5 

6 

6 

6 

Injection-well performance ------------------------ F7 

Changes in specific capacity ------------------- 7 

Effect of temperature on specific capacity --- 10 

Purpose and scope --------------------------- Water-reclamation WeU clogging -------------------------------- 11 and recharge facilities _____ _ Mechanical clogging ---------------------- 11 Geohydrology of recharge site -----------------

Previous work -------------------------------- Biological clogging ----------------------- 13 

Chemical clogging ------------------------ 14 Acknowledgments --------- ______ -------------- Flowmeter surveys ----------------------- 14 Nature of testing --------------------------------

Pumping tests -------------------------------

Injection experiments with public-supply water __ 

Redevelopment of recharge well ---------------- 16 

Pumping and surging --------------------- 16 

Acid treatment --------------------------- 17 Injection experiments with reclaimed water ___ _ Bactericide treatment --------------------- 18 Well-redevelopment experiments --------------- Resting __ _ __ _ __ _ __ __ ___ __ _ _ _ ___ _ _ _ ___ _ __ _ 19 

Effect of injection on aquifer head -----------------

Theoretical head buildup ----------------------

Observed head buildup -----------------------

Summary ---------------------------------------- 19 

References cited ---------------------------------- 20 

ILLUSTRATIONS 

Page 

FIGURE 1. Map showing location of artificial-recharge site, Bay Park, New York --------------------------- F2 

2. Graph showing time drawdown curves for observation well 20 ft from injection well from measurements taken during pumping tests before any injection and after final injection test ------------ 7 

3. Graph showing time drawdown curves for injection well from measurements taken during pumping 

tests before any injection and after final injection test -------------------------------------- 8 

4. Curves showing relation between distance from injection well and drawdown or head buildup after 1 

day, at pumping rate of 350 gal/min. (Based on water levels in observation wells 20, 100, and 200 

ft from injection well.) _____________________ ---·------------ __________ ------------- _________ 8 

5. Graph showing equilibrium head buildup at selected depths and distances from injection well. (Based 

on water levels in observation wells 20, 100, and 200 ft from injection well and at injection rate 

of 350 gal/min.) -------------------------------------------------------------------------- 9 

6. Hydrographs of selected observation wells during injection test RW13, October 24, 1972, to May 11, 

1973 -------------------------------------------------------------------------------------- 9 

7. Graph showing comparison of head buildup and turbidity during test RW7, April 14 to, May 17, 1970__ 12 

8. Diagram showing head buildup in injection well during test RW9, April 27 to May 7, 1971, and turbidity of water injected ---------------------------·-------------------------------------------- 13 

9. Graph showing relationship between suspended solids in injected water and rate of head buildup in 

injection well _____________________ ------------ __________________ -------------------------- 14 

10. Diagram showing depth distribution of flow through well screen during (a) initial flowmeter survey before any injection, (b) pumping before test RW4, and (c) injection in test RW4 --------------- 15 

III 
IV 

TABLE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

CONTENTS 

TABLES 

Page 

Data on injection tests at Bay Park, N.Y., 1968-1972 __ -------------------------------------------- F4 

Injection data from test RW13, October 1972 to May 1973 --------------------------------------- 5 

Statistical comparison of drawdowns at observation wells after 1 day of pumping with head buildups 

after 1 day of injection ------------------------ -------------------------------------------- 6 

Clogging rates in test RW13, October 24, 1972, to May 11, 1973 ---------------------------------- 9 

Unadjusted and adjusted end-of-test specific capacities determined in each injection test ------------ 10 

Turbidity of injected water in tests RW3-RW13 (except RW6) and corresponding decrease in specific 

capacity --------------------------------------·-------------------------------------------- 13 

Aluminum, iron, and phosphate concentrations and pH of liquid pumped after acid treatment of injection well after test RW7 -------------------- -------------------------------------------- 14 

Redevelopment data, test RW13, October 24, 1972, to May 11, 1973 --------------------------------- 18 

CONVERSION FACTORS AND ABBREVIATIONS 

Inch-pound system 

inch (in) 

foot (ft) 

gallon (gal) 

million gallons ( Mgal) 

gallon per minute (gal/min) 

gallon per day (gal/d) 

million gallons per day 

(Mgal/d) 

foot per day ( ft/ d) 

cubic foot per day (ft'1/d) 

gallons per minute per foot 

[ (gal/min)/ft] 

gallons per minute per 

square foot [(gal/min) I 

ft~] 

=25.4 

= 0.305 

= 3.785 

= 3.785X10° 

= 3.785 

3.785 

4.381 x1o-~ 

0.305 

2.832x1o-~ 

= 2.07x1o-l 

=40.677 

Metric units 

millimeters ( mm) 

meters (m) 

liters (L) 

liters (L) 

liters per minute ( L/min) 

liters per day (L/d) 

cubic meters per second (m3 /s) 

meter per day (m/d) 

cubic meters per day (m3 /d) 

liters per second per meter 

[ (L/s) /m] 

litel'ls per minute p·er square 

meter [ (L/min) /m2] 
DEEP-,t\I'ELL ARTIFICIAL-RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER, 

BAY PARK., NEW YORK., WITH TERTIARY-TREATED SEWAGE 

By JoHN VECCHIOLIJ HENRY F. H. Ku} and DENNis J. SuLAM 

ABSTRACT 

From 1968 to 1973, water from public supply and water 

reclaimed from sewage were used in a series of 19 artificialrecharge experiments at Bay Park, N.Y. Recharge to the 

Magothy aquife-r was through a fiberglass-cased well with a 

16-inch-diameter stainless-~steel screen set from 418 to 480 

feet below land surface. Tests ranged from 2 to 33 days, 

except for the final test, in which water was injected intermittently over a 6-month period. During the 6-month test, a 

total of 42 million gallons of water was injected. In some 

tests, selected treatments were applied to the injectant to 

evaluate their effects on well clogging and to determine 

whether they caused geochemical reactions within the aquifer. 

After each test, the injected water was pumped out of the 

aquifer. 

The recharge well and contiguous parts of the aquifer developed varying degrees of clogging, which resulted in excessive head buildup in the recharge well. Maximum reduction 

in specific capacity from 23.5 to 2.5 gallons per minute per 

foot occurred during injection of 14 million gallons of reclaimed water. 

Clogging of the recharge well was caused primarily by suspended-solids content (turbidity) of the injected water. Concentrations above 1 milligram per liter as silica caused disproportionately higher rate·s of clogging than those below 1 

milligram per liter. Microbial growth was an insignificant 

factor in clogging as long as a total residual chlorine level 

of about 2 milligrams per liter was maintained. 

Specific capacity of the recharge well diminished gradually 

during injection but was partly restored by pumping and 

surging the well. Pumping rate was commonly 400 to 500 

gallons per minute. Dosing the well with hydrochloric acid 

aided in removal of clogging material that could not be dislodged by pumping alone. Dosing with solutions of sodium 

hypochlorite and a bactericidal ammonium compound resulted 

in some improvement in specific capacity. Biodegradation of 

the clogging materials occurred when the well was idle after 

injection; redevelopment by pumping and surging was more 

successful after idle periods of several weeks. 

INTRODUCTION 

Growth in the population of Nassau County, a 

suburb of New York City, has been accompanied by 

increased withdrawals. of ground water, which, in 

197 4, was the only source of public-supply water. Net 

withdrawals from the ground-water system have resulted in declining ground-water levels and decreased 

streamflow (Franke, 1968; Garber and Sulam, 1976) 

and in local landward movement of salty ground 

water (Lusczynski and Swarzenski, 1966; Cohen and 

Kimmel, 1970). A continued increase in net withdrawals is expected as population, per capita water 

use, and percentage of population served by sewers 

increase. These growth factors indicate a watersupply deficit of between 71.1 and 91.1 Mgal/ d by 

1990 (Temporary State Commission on Water Supply Needs of Southeast·ern New York, 1972, J>. 

142-144). 

One of several alternatives under consideration by 

Nassau County to me·et the anticipated water-supply 

deficit is reclamation of wa~ter from sewage and injection of the reclaimed water into the ground-water 

reservoir (Peters and Ros.e, 1968). From 1968 to 

1973, the Nassau County Department of Public 

Works operated a pilot advanced waste-treatment 

plant at Bay Park, N.Y., near the south shore of 

Nassau County (fig. 1). Reclaimed water from this 

plant was used in a series of deep-well artificial-recharge experiments by the U.S. Geological Survey in 

cooperation with the Nassau County Department of 

Public Works. These tests were- intended to provide 

some of the scientific and engineering data needed 

to evaluate the degree, causes, and remedies for 

well clogging that results from injection of reclaimed 

water and the geochemical compatibility of the 

reclaimed water with the aquifer. 

PURPOSE AND SCOPE 

This report is the sixth and last chapter in U.S. 

Geological Survey Professional Paper 751, "DeePWell Artificial-Recharge Experiments at Bay Park, 

F1 
F2 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

jill I 

10 0 

'lO 

I 

I I 

10 20 

I 

20 

I 

30 MILES 

I 

30 KILOMETERS 

FIGURE 1.-Location of artificial-recharge site, Bay Park, New York. (From Vecchioli and others, 1974, p. 2.) 

Long Island, New York." The report documents the 

testing that was done, evaluates the hydraulic response of the aquifer to the recharge, and describes 

the performance of the recharge well and the factors 

that affected performance. In this report, emphasis 

is on the hydraulic aspects of the testing; geochemical and microbiological aspects are covered in earlier 

chap:bers. (See section "Previous Work.") 

WATER-RECLAMATION AND RECHARGE FACILITIES 

Reclaimed water for recharge was obtained by 

tertiary-stage treatment (Peters and Rose, 1968; 

Peters, 1968; Vecchioli, Oliva, Ragone, and Ku, 

1975) of about 0.6 Mgal/d of the ·effluent from an 

acti,vated-sludge type 60-Mga.I/ d sewage-treatment 

plant. This treatment consisted generally of coagulation and sedimentation, primary filtration through a 

dual-media sand-anthracite filter followed by secondary filtration through one to four activated carbon 

columns, and finally chlorination. Additional treatm·ent that was applied at times at the recharge facility included degasification, pH adjustment, and 

dechlorination. 

Major components of the recharge facility included (1) a 50,000-gallon storage tank into which 

either public-supply water or reclaimed water was 

delivered, (2) a vacuum-operated degasifier, (3) injection and redevelopment pumps with automatic 

flow controls, ( 4) an injection well consisting of an 

18-inch-diameter fiberglass casing above a 16-inchdiameter stainless-steel well screen set at 418 to 480 

feet below land surface, ( 5) 18 observation wells, 

ranging f~om 20 feet to 200 feet from the injection 

well, some of which were equipped with water-level 

recording equipment, and ( 6) equipment for monitoring several chemical and physical characteristics 

of the water. 

GEOHYDROLOGY OF RECHARGE SITE 

The recharge site is in the Atlantic Coastal Plain 

and is underlain by 1,250 feet of unconsolidated deposits of Pleistocene and Late Cretaceous age, which, 

in turn, overlie crystalline bedrock of Precambrian 

age. The recharge well is screened within the lower 

part of the Ma.gothy aquifer in the Matawan GroupMagothy Formation undifferentiated of Late Cretaceous age, at a depth of 418 to 480 feet belo·w land 

surface. The screened interval (injection zone or receiving zone) is mostly a stratified fine to medium 

quartz sand sandwiched between and semiconfined 

by beds of the Magothy Formation of lesser hydraulic conductivity. At Bay Park, the Magothy 

aquifer is confined by the underlying clay m·ember of 

the Raritan Formation, also of Late Cretaceous age, 

but above, it is virtually unconfined, owing to the 

generally coarse-grained character of the overlying 

Pleistocene deposits. Lateral hydraulic conductivity 

of the stratified injection zone averages 940 (gal/ 

d) /ft2 or 126 ft/ d, but flowmeter surveys indicated 

considerable variation within this interval. The hydraulic characteristics of the aquifer system were 

determined by standard aquifer-test methods; the 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F3 

results were later verified by electric analog-model 

studies. 

PREVIOUS WORK 

The geology and ground-water conditions in southern Nassau and southeastern Queens Counties, including the Bay Park area, were discussed by Perlmutter and Geragthy (1963). Lusczynski and Swarzenski (1966) gave a detailed description of the 

hydrologic environment in southeast Nassau County. 

General discussions of more recent regional hydrologic conditions were given by Cohen, Franke, and 

Foxworthy (1968). The geohydrology of the Bay 

Park site was described in brief by Perlmutter, 

Pearson, and Bennett ( 1968) and in detail by 

Vecchioli, Bennett, Pearson, and Cerrillo ( 197 4) . 

Scope and objectives of the Bay Park wastewaterreclamation and artificial-recharge project have been 

described by Cohen and Durfor (1967) and by Peters 

and Rose (1968). These reports also contain general 

descriptions of the facilities. A detailed description 

of the recharge well was given by Cohen and Durfor 

(1967). Koch, Giaimo, and Sulam (1973) described 

in detail the design and operation of all recharge facilities, including the injection well. 

Many progress reports have dealt with all or most 

aspects of the project in varying detail. Peters 

(1968) commented on the overall project and included some discussion of early operations of the 

treatment and injection plants. V ecchioli and Ku 

(1972) presented preliminary results of early injection experiments. These early results were later updated and summarized by Vecchioli (1972). Principal conclusions drawn from all the tests made were 

discussed in brief by Vecchioli, Oliva, Ragone, and 

Ku (1975). Significant features of the longest recharge test ( 41.7 Mgal over a 6-month period) were 

reported by Sulam ( 1973). 

Reports dealing specifically with geochemical aspects of the recharge experiment include Vecchioli 

and Giaimo (1972) on potential corrosion of metals; 

Faust and V ecchioli ( 197 4) on several problems ; 

Ragone, Vecchioli, and Ku (1973) and Ragone, Ku, 

and Vecchioli (1975) on dissolution of iron from 

the aquifer; Ragone and Vecchioli (1975) on pyrite 

dissolution and ion-exchange reactions; and Ku, 

Vecchioli, and Ragone (1975) on movement of sewage-related substances through the aquifer. Ragone 

(1977) p~resented a comprehensive discw;;sion of all 

geochemical problems studied. 

Baoterial growth around the injection well and the 

significance thereof was described by V ecchioli 

(1970) and Ehrlich, Ehlke, and Vecchioli (1972 and 

1973). Movement of bacteria through the aquifer 

along with the injected water was discussed by 

Vecchioli, Ehrlich, and Ehlke (1972). Additional 

microbiological aspects were reported in detail by 

Ehrlich, Ku, Vecchioli, and Ehlke ( 1979). 

ACKNOWLEDGMENTS 

Individuals who had a major role in the design and 

construction of the injection facilities include John 

H. Peters, former Commissioner of the Nassau 

County Department of Public Works; John L. Rose, 

formerly of Burns and Roe, Inc.; Philip Cohen and 

Bruce L. Foxworthy, U.S. Geological Survey; and 

Charles N. Durfor, formerly with the Geological 

Survey. Particular recognition is given Messrs. 

Cohen and Durfor, whose efforts early in the project 

made possible the detailed testing of the hydraulics 

and hydrochemistry of the aquifer system. 

The installation and early testing of the wells 

were done under the joint direction of Messrs. Cohen 

and Durfor. Most of the credit for the design of the 

op·erating controls and monitoring instrumentation 

of the injection facilities. belongs to Mr. Durfor. In 

preparation for the injection of reclaimed water, 

Gordon D. Bennett of the Geological Survey directed 

extensive hydraulic testing of the injection facilities, 

the injection well, and the aquifer; many of the test 

procedures developed by him were followed with 

little modification throughout the! project. G. D. Bennett and F. J. Pearson, Jr., directed the early recharge tests, where public-supply water was used; 

s.ome of the data from those tests are included in 

this report. 

The authors are especially grateful to former Commissioner John H. Peters and Deputy Con1missioner 

James S. Gillen, Nassau County Department of Public Works, for making available the physical and 

human resources of the Department throughout the 

project. Particular thanks are given also to Francis 

J. Flood, former Superintendent of Operations and 

Maintenance; James A. Oliva, Sanitary Engineer; 

and to many others in the Department for coordinating water-treatment operations with the injection 

experiments, for providing assistance in modifying 

the injection equipment, and for helping with various 

measurements. Louis S. Guaracini of the Department of Public Works provided numerous chemical 

analyses throughout the project. 

Advice and assis·tance on chemical as:pects of well 

clogging were provided by Samuel D. Faust, Department of Environmental Science, Rutgers University, 

and by Stephen E. Ragone, Geological Survey. Garry 

G. Ehrlich and Theodore A. Ehlke, Geological Sur-
F4 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

vey, gave advice and assistance on microbiological 

aspects of deep-well injection. 

Several personnel of the Geological Survey assis,ted in making test measurements and in reducing 

and compiling data. Particular recognition in this 

respect is given Anthony A. Giaimo and Lillian B. 

Mach lin for their assistance throughout the project. 

The authors are grateful to all who assisted. 

NATURE OF TESTING 

PUMPING TESTS 

Pumping tests were made on the injection well 

and some of the observation wells before the sbirt 

of the injection experiments to determine initial hydraulic characteristics of the injection well and the 

aquifer zone tapped by the well (Vecchioli and 

others, 1974). Numerous other pumping tests, ~anging from several hours to several days in duration, 

were made on the injection well from time to time 

throughout the testing period. Changes in hydraulic 

characteristics resulting from injection were determined by comparison of early pumping-test results 

with later ones. 

The pumping rate in most pumping tests of the 

injection well was approximately 400 gal/min. The 

rate was determined with a magnetic flowmeter. 

Volumetric calibrations of flow were made in nearly 

all tests. 

Water levels in the injection well and selected 

observation wells were measured in all tests. These 

measurements were obtained with a combination of 

automatic float-activated water-level recorders, electric water-level indicators, and chalked steel tapes. 

Flowmeter surveys were run in the screened part 

of the injection well during the initial pumping tests 

(Vecchioli and others, 1974) and in some of the 

pumping tests that followed early injection tests. 

Percentage of total discharge contributed by each 

5-foot interval of well screen was measured by a 3-

inch Au-type current meter. 

INJECTION EXPERIMENTS WITH PUBLIC-SUPPLY 

WATER 

Before reclaimed water was injected, four injection tests with water from the local public-supply 

distribution system were completed. These tests 

were done to identify any major problems associated 

with the injection operation and to evaluate procedures of operation and data collection. The period of 

injection in these tests was from 2 to 3 days. The 

rate of injection was either 200 or 400 gal/min, 

TABLE 1.--Data on injection tests at Bay Park, N.Y., 

1968-1972 

Approxi- Injec- mate Gallons 

length tion injected Special 

Test 1 Date rate treatment of (gal/ (thou- of watet· time sands) 

(days) min) 

Public-Supply Water 

1 ______ Feb. 27-29, 2 190 570 Degasified, 

1968 dosed with H~SOl and Na2S0:1. 

2 ______ Mar. 12-14, 385 1,118 Dosed with 

1968 H2SO.t and Na2S03. 

3 ______ Mar. 25-27, 3 185 840 Degasified. 

1968 

4 ______ Apr. 16-19, 3 390 1,655 Nona. 1968 5 ______ Feb. 17-19, 2 400 1,200 Dosed with 

1970 H3PO!. 

6 ------Sept. 13-17, 4 395 2,281 None. 1971 

Reclaimed Water 

RW1 ______ Oct. 8-10, 2 200 616 Degasified. 

1968 RW2 ______ Dec. 10-12, 2 350 1,063 Degasified. 

1968 RW3 ______ Feb. 25-27, 2 350 1,066 None. 19!69 RW4 ------May 6-16, 10 360 5,247 None. 1969 RW5 ______ Sept. 15-25, 10 350 5,117 Degasified. 

1969 RW6 ______ Mar. 17-19, 340 1,133 None. 1970 RW7~ _____ Apr. 14-May 33 200 or850 13,970 None. 17, 1970 RW8 ______ Nov. 30-Dec. 10 340 4,930 U nchlorinated. 

10, 1970 RW9 ______ Apr. 2.7-May 10 355 5,156 None. 7, 1971 RW10 _____ Nov. 1-11, 10 350 5,180 Bypassed 

1971 carbon 

adsorbers. RW10A ____ Jan. 10-14, 4 350 2,000 U nchlorinated. 

1972 

RWll _____ Mar. 6-16, 10 350 5,124 Dosed with 

1972 Na2S20a 

·6H20. RW12 _____ June 5-15, 10 355 5,050 Dosed with 

1972. NaOH. RW13:: ____ Oct. 24, 1972- 84.5 355 41,695 None. May 11, 

1973 

1 Tests 1-6 used public-supply water; RW indicates that reclaimed water was used. ~ Inject'on rate was decreased after 19 days because of reduced output from treatment plant. :: Injection was done intermittently. (See table 2.) 

depending on whether the degasifier was used. Selected chemical treatments were applied to the water 

(table 1) to test their effect on well clogging or on 

geochemical reactions. Later, during inJection tests 

using reclaimed water, two additional tests were 

made in which public-supply water was injected for 

2 and 4 days. The public-supply water experiments 

were run to test hypotheses concerning geochemical 

reactions. (See Ragone, 1977.) 

The same kinds of measurements that were made 

in the pumping tests were also made during the 

injection tests. However, in some tests, water-level 

measurements in the injection well (N7884) and in 

two observation wells (N7885, N7886) were made 

with water and (or) mercury manometers, depending on the head buildup, instead of with float-activated recorders or tapes. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F5 

INJECTION EXPERIMENTS WITH RECLAIMED WATER 

Thirteen injection experiments with reclaimed 

water were done between October 1968 and May 

1973. (See table 1.) These tests ranged in duration 

from 2 days to 6 months. The usual injection rate 

was 350 gal/min. Except for brief shutdowns during a few of the tests, water was injected continuously in all tests but RW13. Injection in test RW13 

was discontinuous because pl1anned weekend shutdowns, equipment breakdowns, and short periods of 

backflushing for well redevelopment divided the injection period into 18 separate segments (table 2). A 

total of 42 Mgal was injected during test RW13. 

In all tests but RW6, including the tests using 

public-supply water, water was pumped into the injection well through the injection line entering the 

well at a depth of 192 feet. (Details are given by 

Koch and others, 1973, p. B3.) In test RW6, water 

was injected through the injection line entering the 

well at land surface. Because disruptive vibrations 

were caused by the impact of the water stream on 

pipes suspended in the well when water was injected 

into the well at land surface, the surface-injection 

route was not used in any other tests. The third 

possible injection route-through the column of the 

redevelopment pump-was not used at all. 

Chemical quality of water was purposely varied in 

the tests using public-supply water and seven of the 

tests using reclaimed water to evaluate the significance of water quality on various aspects of the injection regime (table 1). 

The injection rate was monitored with the magnetic flowmeter mentioned earlier and calibrated 

volumetrically in each test. Water-level measurements in the injection well and in selected observation wells were made in all tests with a combination 

of automatic float-activated water-level recorders, 

water and (or) mercury manometers, and pressure 

gages. Flowmeter surveys in the screened part of 

the injection well were made during the early tests 

but were discontinued in the later tests because they 

turned out to be of questionable value. (See section 

"Flowmeter Surveys" and fig. 10.) 

WELL-REDEVELOPMENT EXPERIMENTS 

Several methods of redevrelopment were tried in an 

attempt to restore well capacity, which decreased to 

snme degree during each injection test. Prolonged 

pumping of the well with a deep-well turbine pump, 

which is an integral part of the injection-well installation (see Koch and others, 1973, p. B7, for details), 

was done either alone or in combination with some 

other technique. The well was pumped at different 

rates, ranging from 100 to 1,000 gal/min, but 400 to 

500 gal/min was most common. 

On many occasions, the well was surged by a 

cyclic starting and stopping of the pump at short 

intervals; this pumping was generally at the maximum rate of 1,000 gal/min. After one injection test, 

when the deep-well turbine pump had to be removed 

for repair of the well casing, the well was surged by 

swabbing with a double surge block in combination 

with air-lift pumping. 

TABLE 2.-lnjection data from test RW13, October 1.972 to May 1973 

[Injection rate 350 gal/min. unless otherwise noted. Modified from Sulam, 1973] 

Date Date Total Total Cumulative Head Specific capacity 

Segment started ended number gallons gallons buildup [(gal/min) /ft] 

of days injected injected (ft) Start End Change 

1 -------- 10-24-72 10-27-72 3 1,598,400 1,598,400 19.5 23.7 118 - 5.7 

2 -------- 11- 7-72 11-17-72 10.5 5,192,400 6,790,800 28.5 25.8 12.3 -13.5 

3 -------- 11-20-72 11-22-72 2.5 1,213,600 8,004,400 28.5 12.3 12.3 0 

4 -------- 11-27-72 12- 8-72 11.5 5,657,300 13,661,700 52.6 12.3 1 6 - 6.3 

5 -------- 12-13-72 12-15-72 2.5 1,246,800 14,908,500 30.8 14.7 11.3 - 3.4 

6 -------- 12-19-72 12-21-72 2.5 1,255,400 16,163,900 36.0 11.3 1 9.7 - 1.6 

7 -------- 1- 3-73 1-12-73 9.5 4,706,700 20,870,600 43.6 11.7 7.9 - 3.8 

8 -------- 1-15-73 1-19-73 4.5 2,246,600 23,117,200 48.7 7.9 1 7.1 - .8 

9 -------- 1-29-73 2- 4-73 6.5 3,206,300 26,323,500 48.7 12.8 1 7.1 - 5.7 

10 -------- 2- 6-73 2- 9-73 3 1,470,600 27,794,100 50.2 13.0 1 6.9 - 6.1 

11 -------- 2-10-73 2-10-73 .33 149,400 27,943,500 30.2 11.6 

12 -------- 2-12-73 2-13-73 .67 324,700 28,268,200 ~ 24.8 C) 

13 -------- 3-12-73 3-16-73 4.5 2,207,700 30,475,900 38.3 12.6 9.2 - 3.4 

14 -------- 3-19-73 3-30-73 11.5 5,678,200 36,154,100 46.2 9.2 8.1 - 1.1 

15 -------- 4- 2-73 4- 6-73 4 1,963,000 38,117,100 50.1 8.1 1 7.0 - 1.1 

16 -------- 4- 9-73 4- 9-73 .5 233,500 38,350,600 32.8 13.3 111 - 2.3 

17 -------- 5- 2-73 5- 4-73 2.5 1,177,400 39,528,000 33.8 12.7 9.8 - 2.9 

18 -------- 5- 7-73 5-11-73 :c 4.5 2,166,700 41,694,700 40.9 9.8 8.6 - 1.2 

1 Redevelopment. (See table 8.) ~Injection rate reduced to 200 gal/min. :: Hydrochloric acid added. 
F6 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NRW YORK 

Several chemical treatments were applied to observe their effectiveness in restoring specific capacity. 

During two tests, the well was dosed with hydrochloric acid; during other tests it was dosed with 

bactericides. Solutions of an ammonium compound 

were used in two tests; solutions of sodium hypochlorite were used in three tests. 

EFFECT OF INJECTION ON AQUIFER HEAD 

THEORETICAL HEAD BUILDUP 

When water is injected into an aquifer through a 

well, a cone of elevation, or mound, forms around 

the well in the shape of an inverted cone of depression. Theoretically, in a confined isotropic homogeneous aquifer of infinite areal extent, the cone of 

elevation would be the mirror image of the cone of 

depression, given equal time periods of and rates of 

pumping and provided that· the water injected had 

the same viscosity as the native ground water. 

Although the injection zone at Bay Park differs 

somewhat from the theoretical model (Vecchioli and 

others, 197 4), the observed hydraulic response 

closely approximated the theoretical response within 

a radius of 200 feet of the injection well, which is 

the limiting radius of observation at Bay Park. Accordingly, the shape of the cone of elevation, and 

water levels in wells within the cone at any time, 

should be predictable from observations made during 

pumping tests. Any departure from predicted response, after all appropriate corrections are made, 

would indicate a change in the hydraulic characteristics of the receiving zone. 

OBSERVED HEAD BUILDUP 

Head-buildup data obtained at each of the observation wells tapping the Magothy aquifer and during each injection test were compared with corresponding drawdown data to evaluate the "mirror 

image" theory. These data were also examined for 

any progressive change in the hydraulic characteristics that might have occurred over the course of 

the injection experiments. 

Values of head buildup at each well were grouped 

according to the type of water injected, and each 

group was evaluated statistically (table 3). Mean 

head-buildup values at each well and in each group 

of tests were compared with the drawdown value 

obtained from the initial pumping tests at the corresponding time. The hypothesis that the injectiont~est means were the same as the pumping-test 

values was evaluated at the 95-percent confidence 

level. The hypothesis was acceptable in all instances 

except for observation well N7886, 20 feet from the 

injection well, during tests with reclaimed water .. 

Reasons for the difference in response at well 

N7886 are unclear. This well is screened in the same 

depth interval as the injection well and is only 20 

feet from it. During the recharge tests, well N7886 

was pumped at 1 to 2 gal/min for sampling. The 

pumping interfered slightly with the water-level 

observations, and corrections for the interference 

were not made rigorously. This interference would 

cause the head buildup to be low in relation to the 

pumping-test drawdown, and observation confirmed 

this. Also, throughout most of the tests using reclaimed water, for ease of computation, average 

tidal-efficiency and barometric-efficiency factors 

were applied in adjusting the observed water levels 

at all the wells; however, individual factors were 

applied to all well results during the initial pumping 

tests. This discrepancy adds additional uncertainty 

to the accuracy of the comparison. 

TABLE 3.-Statistical co·mparison of drawdownR at obsr1·vation wrlls afte·r 1 day of pumping with head buildups afte·r 1 day of 

·injection 

!Values are in feet per 100 gallons per minute! 

Initial Public-supply water injection test.; Reclaimed-water injection tests 

Obser- pumping 

vat ion test Number Maxi- Mini- Standard Number Maxi- Mini- Standard 

well 1 of Mean devia- Rnmlt" of Mean devia· Result 2 

tests mum mum tion tests mum mum tion 

N7886 --------- 1.77 6 1.78 1.65 1.70 0.05 A 13 1.71 1.55 1.64 0.04 R 

N7887 --------- .35 6 .41 .34 .38 .03 A 13 .41 .32 .36 .03 A 

N7888 --------- .19 6 .27 .20 .24 .03 A 13 .28 .16 .21 .04 A 

N7889 --------- .35 6 .42 .31 .37 .04 A 13 .41 .30 .36 .03 A 

N7890 --------- 1.06 fi 1.09 1.00 1.03 .03 A 13 1.08 .92 1.00 .04 A 

N7891 --------- .20 5 .22 .28 .26 .03 A 13 .27 .18 .21 .03 A 

N8022 --------- .79 6 .85 .79 .83 .03 A 13 .84 .72 .77 .03 A 

N7290 --------- .30 5 .38 .31 .35 .03 A 12 .38 .29 .33 .03 A 

1 Locations are given in Koch and others ( 197::1, fig. g). 

"Test of hypothesis: The mean of the injection tests i>< equal to the m:oan of pumping test at !15-percent confidence level. A, acceptance; R, re- jection. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F7 

On the other hand, the slightly lower head buildup 

observed at well N7886 during injection could reflect 

a slight dilation of the receiving zone in res.ponse 

to the increase in pore pressure. This dilation, if 

present, would be greatest in the vicinity of the injection well, where the disturbance was greatest. 

Moreov.er, the dilation near the injection well would 

be greater than the compaction that might occur 

near the injection well during pumping. Dilation of 

the receiving zone upon injection would tend to increase the hydraulic conductivity; hence, head buildup would be less than drawdown if all conditions 

other than direction of flow were equal. 

No chronologie trend was observed in headbuildup values. Also, drawdown data from. a pumping test (well N7886) made after conclusion of the 

injection tests were virtually identical to those from 

the initial pumping tests (fig. 2) except for drawdown in the injection well (fig. 3). Differences in 

drawdown values of the injection well reflect residual partial clogging of the well, as discussed in the 

later section "Injection-Well Performance." These 

observations indicate that no significant cumulative 

changes in the hydraulic properties of the aquifer 

resulted from the experiments. 

Comparison of the slope of the cone of elevation 

formed during injection with the slope of the cone 

of depression formed during pumping (fig. 4) shows 

the two to be similar. The slightly discrepant data 

from well N7886, 20 feet from the injection well, indicate the 0one of elevation to be slightly smaller 

than the cone of depression and to have a slightly 

lesser slope. 

Figure 5 illustrates the head-buildup distribution 

that was observ·ed vertically and radially in the Magothy aquifer when water was injected at a rate of 

350 gal/min. In layers above the Magothy aquifer 

that are less than 100 feet below land surface, waterlevel fluctuations (fig. 6) indicated no head buildup. 

A small amount of head buildup in these layers 

probably occurred but was masked by water-level 

fluctua;tions caus-ed by other factors. Head buildup 

in all zones observed was virtually stable after 1 day 

of injection. 

INJECTION-WELL PERFORMANtm 

CHANGES IN SPECIFIC CAPACITY 

Performance of the injection well during the injection experiments can be evaluated in terms of the 

specific capacity of the well. When water is withdrawn from a well, the specific capacity of the well 

is the rate of yield, in gallons per minute per foot 

of drawdown; when water is injected into a well, 

the specific capacity of the well is the rate of injection per foot of head buildup. If no well clogging ·ocw 

.... 

:::> .. z 

~~ 

a:: a: 

c(w 

-1.0 5 a.. 

en en 

QZ 

>-g 

al..J 

<( 

~Use right scale 

~ for points . . ..... -1.5 0 (!) 

w 

00 

-w 

~a: 

oo 

Use left scale 

/ 

for curve 

10 100 1000 

TIME SINCE PUMPING BEGAN, IN MINUTES 

zz 

2.0 ~~ 

oa: Ow 

~a.. 

<( .... a::w 

-2.5 0 w 

LL 

10,000 z 

FIGURE 2.-Time drawdown curves for observation well 20 ft from injection weU from measurements taken during pumping 

tests before any injection and after final injection test. Solid curve, pumping tests before injection; solid circles, pumping test after last injection. 
F8 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

w 

.__ 

:::> .. z 

w-

(!)~ 

a: a: 

<(w Q 0..2.0 

en en 

csz 

>-g 

Q'l...J 

<( 

0(!) 

w 

co 

-w 

~a: 

co 

zZ 

:::> 

~:I: 3.0 

oa: 

~~ <(.__ 

a:w 

Ow LL 

z 

Use 

for 

left 

curve 

scale ~ 

10 100 

Use right scale 

• ••• ~ for points 

1000 

....... 

z. 

TIME SINCE PUMPING BEGAN, IN MINUTES 

FIGURE 3.-Time drawdown curves for injection well from measurements taken during pumping tests before any injection and 

after final injection test. Solid curve, pumping tests before injection; solid circles, pumping test after last injection. 

100 

EXPLANATION 

------ Initial pumping test 

Final pumping test 

---• -- Public-supply-water 

injection test 

------ Reclaimed-water 

injection test 

1000 

RADIAL DISTANCE FROM RECHARGE WELL, IN FEET 

FIGURE 4.-Relation between distance from injection well and drawdown or head buildup after 1 day, at pumping rate of 

350 gal/min. (Based on water levels in the observation wells 20, 100, and 200 ft from injection well.) 

curs, the head buildup observed in the well during 

injection should theoretically equal the drawdown 

that would occur if the well were pumped at the 

same rate, other things being equal. Head buildup in 

excess of that amount is an indication of clogging 

of the well and (or) the aquifer and is reflected in a 

decrease in the injection specific capacity of the well. 

The rate of clogging differed considerably from 

test to test and within individual tests, as shown by 

the data in table 4 for test RW13. The average rate 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F9 

12 

1-

~ 10 LL 

~ 8 

a: 

:::> 

c 

..J 

5 

co 

c 

<( 2 w 

:I: 

0 

0 50 100 150 200 

RADIAL DISTANCE FROM RECHARGE WELL, 

IN FEET 

FIGURE 5.-Equilibrium head buildup at selected 

depths and distances from injection well. (Based 

on water levels in observation wells 20, 100, and 

200 ft from injection well and at injection rate 

of 350 gal/min.) (From Vecchioli and others, 1975, 

p. 207.) 

are considered, however, the average rate of clogging 

was approximately 3 feet of excessive head buildup 

per 1 Mgal. This value is probably the more representative of long-term clogging rates. 

Initially, the pumping specific capacity of the injection well was 32.8 (gal/min) /ft after 2 days of 

TABLE 4.-Clogging rates in test RW13, October 24, 1972, to 

May 11, 1973 

[Modified from Vecchioli and others, 1975~ p. 208] 

Reclaimed water volume 

injected 

(Mgal) 

1.598 

Excessive head buildup 1 

(ft) 

Head buildup per injection 

volume 

(ft/Mgal) 

2.5 

2.7' 

4.9 

2.8 

6.9 

of clogging observed during test RW13 was approximately 4 feet of excessive head buildup per 1 Mgal. 

If only the recharge episodes greater than 3 Mgal 

12.063 

2.502 

6.953 

3.206 

1.471 

9.849 

3.344 

4.0 

32.5 

12.3 

19.4 

22.0 

23.8 

22.2 

13.1 

1 Amount of head buildup attributed to well clogging. 

16.2 

2.3 

3.9 

1-

w 

w 

LL 

~ 

...1 

w 

> w 

....J 

a: 

w 

I-

~ 8. 

LL 

0 

w 

0 

:::) 

1-

i= 

....J 

<( 

6. 

OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL 

5 1 0 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 

I I I I I I I I I I I I I I I I I I I I I I I I I I I II I I I I I I I I I I I I 

N7675 (Depth 34ft, distance 200ft) 

N7677 (Depth 87 ft, distance 200 ft) 

N7888 (Depth 317ft, distance 20ft) 

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 

SEPTEMBER OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY 

1972 19·73 

FIGURE 6.-Hydrographs of selected observation wells during injection test RW13, October 24, 1972, to May 11, 1973. 
FlO ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

pumping. Both the specific capacity and drawdown 

changed very little after 1 day of pumping and became virtually stable after 2 days (fig. 3). In fact, 

the difference between the specific capacity after 4 

hours of pumping and after 2 days was only a few 

tenths of a unit. Hence, evaluations of long-term 

changes in specific capacity during inj-ection were 

made from data from shorter pumping tests. Pumping specific capacity was determined before and after 

each injection experiment. 

The injection specific capacities observed in each 

injection test were lower than the corresponding 

pumping specific capacities obtained before ea.ch 

test, as shown by data in colun1ns 1 and 2 of table 5. 

Even after adjustments for differences in wate,r 

temperature, as discussed fqrther on, the injection 

specific capacities were lo\. _ than the pretest values 

in all tests, and the pretest specific capacity of 32.8 

(gal/min) /ft was not res~tored during the injection 

experiments. This indicates that some clogging of 

the well and (or) the contiguuus part of the aquifer 

had o-ccurred in each injection test. 

EFFECT OF TEMPERATURE ON SPECIFIC CAPACITY 

Temperature of native water in the 420-to 480-

foot interval (recharge zone) of the Magothy aquifer 

is l5°C. Temperature of water injected varied from 

test to test, ranging from 9°C in one of the tests 

using public-supply water to 23°C in one of the tests 

using reclaimed water (table 5). Adjustments were 

made in the observed specific capacities. to correct 

for the temperature differences because (1) the 

vis~cosity of the water is inversely related to the 

temp·erature, (2) the hydraulic conductivity of the 

aquifer is inversely related to the viscosity of the 

water, and (3) the specific capacity of the well is 

directly related to the hydraulic conductivity of the 

aquifer. 

Obs-erved specific capacities were adjusted according to a method described by G. D. Bennett (written 

commun., 1969). In Bennett's method, the extent of 

the cylinder of injected water (.the temperature of 

which differs from that of the aquifer) is taken into 

consideration. The head-buildup correction needed 

at any time as a result of temperature difference is 

calculated from the equation : 

SwTt- Swt = (-1--2_) 2

.

3

Q log ( rTt ), 

KLT KL 21rD r w 

where Sum-Swt=head bulildup at injection well for 

injection of water temperature T, 

at time t, minus head buildup in 

TABLE 5.-Unadjusted and adjusted end-of-test specific capacities determined in each injection test 

[Specific capacities are in gallons per minute per foot] 

(2} (3) (6) (1) Unad- Approxi- Pretest jus ted Apparent (4) (5) AdjU~Sted (7) 

Test mate 2-day end-of- decrease Water Head- end-of- Adjusted 

No. length pumping test in- in specific tempera- buildup test in- decrease (days) capacity ture correction jection in specific 

of test specific jection (col. 1 minus (oC) (ft) specific capacity capacity specific 

capacity col. 2) capacity 

Public-Supply Water 

11 ---------- 2 32.8 32.3 0.5 10 -0.48 35.1 0 

2 ---------- 2 32± 28.2 3.8± 11 - .96 30.4 1.6± 

3 ---------- 3 32± 27.8 4.2± 12 - .33 29.2 2.8± 

4 ---------- 3 32± 27.4 4.6± 13 - .39 27.8 4.2± 

5 ---------- 2 25.3 19.6 5.7 9 -1.26 20.9 4.4 

6 ---------- 4 26.7 24.4 2.3 18 .45 23.7 3.0 

Reclaimed Water 

RW1 ------- 2 31.7 28.6 3.1 22 +0.50 26.7 5.0 

RW2 ------- 2 30.4 27.4 3 16 + .14 27.1 3.3 

RW3 ------- 2 30.5 30.3 .2 14 - .14 30.6 0 

RW4 ------- 10 30.3 17.7 12.6 18 + .53 17.2 13.1 

RW5 ------- 10 28.9 14.7 14.2 23 1.21 14.0 14.9 

RW6 ------- 2 24.3 20.8 3.5 14 - .14 21.0 3.3 

RW7 ------- 33 23.5 2.5 21.0 16- + .27 2.5 21.0 20 

RW8 ------- 10 26.5 11.0 15.5 18 + .42 10.8 15.7 RW9 _______ 10 26.5 15.3 11.2 18 + .44 15.0 10.5 

RW10 ______ 10 25.6 15.2 10.4 21 + .97 14.6 11.0 ~RWlOA 4 26± 23.8 2.2± 17 

RWll ______ 10 24.9 22.8 2.1 15 0 22.8 2.1 

RW12 ______ 10 22.5 16.1 6.4 21 + .97 15.4 7.1 1 RW13 ------ 84.5 25.8 8.6 

1 Rate control poor; specific-ca;:>acity data uncertain. ~ Adjustments for temperature not mad.e. Water injected in previous test not repumped. 

::Adjustments for temperature not made. Test consisted of 18 separate segments of continuous injection. Eleven episodes of redevelopment were interspersed between injection segments. End-of-test specific capacity is specific capacity at end of last injection segment. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER Fll 

injection well for formation water, 

at time t, in feet, 

Kr,1' =lateral hydraulic conductivity to injection water of temperature T, in 

feet per day, 

KL =lateral hydraulic conduc.tivity to 

formation water, in feet per day, 

Q =injection rate, in cubic feet per day, 

D =thickness of injection stratum, in 

feet, 

rTt =radius of cylinder of injected water 

of temperature T, at tin1e t after 

start of injection, in feet, and 

rw =radius of injection well, in feet. 

The lateral hydraulic conductivity of the formation to injection water at temperature T, KLT, is obtained by multiplying the hydraulic conductivity to 

formation water, Kr,, by __!!:_, where 1t is the viscosity 

P..T 

of the formation water and p..r is the viscosity of the 

injected water. 

In ap·plying the temperature adj ustn1ents, one 

must make several simplifying assumptions that are 

not entirely valid. Hence, the adjustments to the 

specific capacities as given in table 5 represent extreme values; the actual adjustments should probably be somewhat less. Accordingly, the true end-oftest specific capacity probably lies somewhere 

between the observed value and the adjusted value. 

WELL CLOGGING 

Clogging of injection wells results from three general types of action-biological, mechanical, and 

chemical (American Water Works Association, Task 

Group 2440-R on Artificial Ground Water Recharge, 

1965). Individual mechanisms of each type can operate separately or together to cause clogging. Some 

may clog wells abruptly, whereas others may do it 

gradually. Identification of the clogging mechanism(s) is essential for selection of proper treatm·ents to remedy the clogging and to prevent or 

minimize its recurrence. 

Biological clogging may result from e1ither the 

growth of foreign organisms introduced by injection 

or from the growth of indigenous organisms stimulated by nutrients in the injected water. These 

growths may occur within the well, at the aquifer 

face, or within the aquifer at son1e distance from 

the well. According to Ehrlich (1972, p. 299), bacteria are the organisms of main concern in the injection well/aquifer regimen. 

Mechanical or physical clogging can be caused in 

several ways. Reversing the direction of water movement in the aquifer adjac·ent to the injection well 

may rearrange particles, which could result in denser 

packing and a consequent reduction in hydraulic 

conductivity. Particles susp·ended in the injected 

water may filter out and accumulate either within 

the gravel pack, at the interface between the gravel 

pack and the aquifer, or within the interstices of the 

aquifer. The particles may be introduced by the injected water or they may come from erosion of residual drilling mud that was not removed completely 

during well development. Microorganisms carried 

by the water may also plug the gravel-pack and (or) 

aquifer interstices in the same manner as inorganic 

particles. Air bubbles entrained in the injected water 

or dissolved gases that are liberated once the water 

is within the aquifer may cause binding of the 

aquifer. 

Chemical clogging may result from chemical reactions between the injected water and the aquifer 

particles and (or) the native water. Ion-exchange 

reactions involving injected water having high sodium concentrations (generally more than 50 percent of cation concentration) may result in a disp~ersal of clay particles, which may plug interstices. 

Mineral species in solution in either the injected or 

native water may become unstable upon mixing of 

the two waters, with the result that a chemical precipitate may form. The pr~ecipitate may act as a cement and seal aquifer intel'stices. Carbonates, sulfides, and hydroxides-commonly of iron-are the 

groups generally of concern with respect to chemical 

clogging. 

A considerable part of the Bay Park study was 

devoted to identification of clogging mechanisms and 

methods of either controlling these mechanisms or 

remedying the resultant clogging. Mechanical clogging predominated in this study; biological clogging 

was significant only when the reclaimed water was 

not chlorinated before injection. Some chemical clogging probably occurred, but its effect on excessive 

head buildup was greatly overshadowed by that of 

mechanical clogging. Evidence for these conclusions 

follows. 

MECHANICAL CLOGGING 

Mechanical clogging resulted mainly from the filtra.tion, onto the aquifer face, of suspended matter 

carried by the injectant. Because determination of 

the very low suspended-solids concentration in the 

injected water is difficult, turbidity was used as a 
F12 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

w 

~ 0.35 

z 

i 

ffi 0.30 Q. 

z 

0 

< ~ 0.25 (!J 

a: 

w 

Q. 

1- 0.20 

0 

0 

~ 

~ 0.15 

w 

(!J 

a:: 

< 6 0.10 w 

a: 

...... 

0 

;::i 0.05 l: 

TOTAL TIME OF INJECTION, IN DAYS 

70 

~ 

0 

60 ~ ffi 

:::>1-

t-::J 

~c:: 

50 :::> w ~a. 

~~ ~< 

40 w ~ ~::J I- ...I 

~i :::> 30 ~ z :::>-. 

UQ'I 8 00 I 

20 >en C::< 

w 

en 

m 

0 

10 

FIGURE 7 .-Comparison of head buildup and turbidity during 

test RW7, April 14 to May 17, 1970. A, head buildup 

divided by rate of injection; B, cumulative maximum turbidity. (From Ehrlich and others, 1972, p. B243.) 

measure of the variations in suspended-solids 

concentration. 

Figure 7 shows the relation of turbidity to clogging of the injection well during test RW7. In this 

figure, the maximum turbidity values observed each 

day are cumulated and compared with the specific 

head buildup (~ head/injection rate), which is the 

reciprocal of the specific capacity during injection. 

Similarity of the two curves is readily apparent. 

Specific head buildup would have leveled off after 

the second day if there had been no clogging. 

The fine- to medium-grained characte·r of the injection stratum renders it very effective in filtering 

particulate matter from the injectant. Moreover, 

considering that the inJection-well complex has a 

diam·eter of 3 feet and a screen length of 62 feet, the 

aquifer face was loaded at a rate of approximately 

0.6 (gal/min) /ft 2 when the injection rate was 350 

gal/min·. Thus, even though levels of suspendedsolids concentration (in turbidity units) were generally below 1 mg/L (milligram per liter) accumulation of the injected solids at the aquifer face was 

considerable. Particulate accumulation in the gravel 

pack caus·ed little clogging; heads in an observation 

well screened in the gravel pack differed from thos·e 

in the injection well by only about 0.1 foot throughout all tests but RW8. (Reasons for anomalous heads 

in test RW8 are discussed in section "Biological 

Clogging.") 

Variations in turbidity of the water injected in 

tests RW3 through RW13 (except RW6) are summarized in table 6, together with the corresponding 

decrease in specific capacity per million gallons of 

water injected. Little correlation is evident between 

mean turbidity and decrease in specific capacity. 

However, in tests in which the m.aximun1 turbidity 

values were less than 1 mg/L, decrease in specific 

capacity was slight. Slugs of injectant having turbidity greater than 1 mg/L seemed to affect the 

well's specific cap·acity to a disproportion3Jtely 

greater degree than water of lower turbidity. 

The sensitivity of the rate of clogging to seemingly 

small changes in turbidity is seen in figure 8. In test 

RW9, head buildup increased at a low rate in the 

early part of the test, when the turbidity of the inJectant averaged 0.1 mg/L and did not exceed 0.75 

mg/L. How·ever, in the latter part of the test, when 

turbidity increased to an average of 0.6 mg/L and 

·reached a maximum of 1.5 mg/L, the rate of head 

buildup increased sharply. 

The amount of clogging caused by a given sus1 pended-solids concentration generally depended on 

: the degree to which the well was clogged at the time. 

A given suspended-solids load caused less head buildup when specific capacity was high than when it was 

much lower. This relation was definable only in very 

general terms. However, a crude relation was developed between suspended-solids concentration and 

excessive head buildup within the range of specific 

capacity observed during test RW13; this relation 

is shown in figure 9. Only injection periods of 1 week 

or longer, uninterrupted by redevelopment, were 

considered. Inje~ted suspended-solids load was computed from turbidity determinations. Specific capacity of the injection well throughout test RW13 

ranged from 6 (gal/min) /ft to 13 (gal/min) /ft, 

except during the first several days of the test. Over 

this range of well efficiency, the unit change in head, 

in feet per million gallons, was 0.74 times the change 

in suspended-solids load, in pounds per million 

gallons. 

Well clogging caused by the release of entrained 

air or dissolved gases from the injected water was 

not observed. The reclaimed water injected was degasified in two of the 2-day te~ts and in one 10-day 

test, and, contrary to expectations, the excessive 

head buildup in those tests was higher than in com-

:rarable tests in which the water was not degasified. 

Any minor beneficial influence of degasification was 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F13 

~-------;_A.verage turbidity.0.'1 m:..;og~/L=:-------')I!Io-!1~<----....!::.~· Maximum turbidity 0.75 mg/L 

1-

w 

w 

LL 20 

z 

0: 

=> 

0 

....J 

=> 

co 

0 10 <( 

w 

I 

----~~---aHead= 1.5 ft /d -----~ 

2 4 6 8 10 

NUMBER OF DAYS SINCE INJECTION BEGAN 

FIGURE 8.-Head buildup in injection well during test RW9, April 27 to May 7, 1971, and turbidity of water injected. (Modified from Vecchioli, 1972, p. 93.) 

TABLE 6.-Turbidity of injected water in tests RW3-RW13 (except RW6) and corresponding decrease in specific capacity 

Turbidity 

[mg/L as StO~] Specific-capacity decrease 

Test Number divided by vo.Jume injected 

[ (gal/min) /ft J Minimum Maximum Mean Standard of Mgal deviation determina- tions 

RW3 ------------ 0.3 0.8 0.6 0.2 9 0 

RW4 ------------ .2 1.8 .9 .4 68 2.5 

RW5 ------------ .1 1.6 .6 .3 134 2.9 

RW7 ------------ .2 7.5 1.6 1.4 77 1.5 

'RW8 ------------ 0 .3 .1 .1 3 10 3.2 

RW9 ------------ 0 1.4 .4 .4 92 2.0 

RW10 ----------- 0 3.3 .8 .8 50 2.1 

RWll ----------- 0 .7 .2 .3 41 .4 

RW12 ----------- 0 1.5 .2 .3 42 1.4 2 RW13 ----------- 0 1.9 .4 .3 385 

1 Injection water not chlorinated. ~Injection discontinuous. See table 2 and figure 9 for further information. ~ Daily average of at least four determinations. 

indiscernible because of the overriding influence of 

variations in turbidity on well clogging. 

The Bay Park recharge system permitted little 

air entrainment because the water was injected 

under pressure well below static level. Also, because 

the temperature of the reclaimed water was about 

equal to or warmer than the temperature of the 

aquifer water in all tests, any gases dissolved in the 

injected water would tend to remain in solution 

within the higher pressure and lower temperature 

environment of the aquifer. 

BIOLOGICAL CLOGGING 

The reclaimed water that was injected was ordinarily chlorinated as the final step in the tertiarytreatment process. A chlorine dosing of 5 to 7 mg/L 

provided an effective bacterial kill. With this dosage 

and approximately 2 hours of contact time, the residual chlorine level of the water at the point of 

injection was approximately 2 mg/L. Under these 

conditions, microbial growth around the screen of 

the recharge well was effectively suppressed, and 
F14 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

l-en 

w 26 

~0 ....J Z....J -<( 

0:<.9 

:::> z 4 oa ....J_ 

-....J 

::J....J 

me~ 

<(a: 2 ww ::z:O.. 

~H=0.74~SS 

0~----~----~------~----~----~ 

0 2 4 6 8 

SUSPENDED SOLIDS, IN POUNDS 

PER MILLION GALLONS 

10 

FIGURE 9.-Relationship between suspended solids in 

injected wate,r and rate of head buildup in injection well. (From Vecchioli and others, 1975, p. 

208.) 

clogging caused by microbial factors was insignificant (Ehrlich and others, written commun., 1977). 

Considerable microbial clogging did take place, 

however, in test RW8, in which unchlorinated water 

was injected (Ehrlich and others, 1973). Although 

turbidity of the injectant in this test was very low, 

the rate of clogging was higher than in other tests 

in which chlorinated water having higher turbidity 

was injected. (See table 6.) Moreover, in this test, 

much of the clogging took place within the gravel 

pack of the injection well, in contrast with the clogging observed in other tests, which was mostly at 

the interface between the gravel pack and the aquifer. Near the end of test RW8, the head in the injection well was about 12 feet higher than in the 

observation well within the gravel pack, whereas in 

all other tests, the difference in head was on the 

order of 0.1 foot. Bacterial analyses of water recovered from the filter pack and of material in a sandfilled probe suspended in the observation well tapping the filter pack during the test indicate that 

microbial growth and associated slimes caused much 

of the observed loss in specific capacity of the recharge well (Ehrlich and others, 1973, p. 344). 

CHEMICAL CLOGGING 

Compounds of iron, aluminum, and phosphorous 

accumulated in the vicinity of the injection well and 

contributed to clogging in most of the tests. Part of 

the accumulation resulted from the filtration of the 

colloidal or larger particulate form of these constituents from the injected water. However, part of 

the accumulation may have resulted from the chemical precipitation of the dissolved fraction of these 

constituents at or near the aquifer face. According 

to Ragone (1977), application of WATEQ, the computer program of Truesdall and Jones (1974), to the 

chemical data showed that the water recovered early 

during pumping of the injection well was supersaturated with aluminum and iron hydroxy species 

and iron oxide species. Hence, some chemical precipitation of some or all of these species could have 

occurred in some of the tests. 

It was not possible to demonstrate that purely 

chemical clogging occurred in any test because of 

the overwhelming influence of mechanical clogging 

and because the chemical species involved also made 

up part of the particulate load injected. For example, Ragone and others (1973) found that the 

amount of iron recovered from the recharge well 

during repumping after test RW10 was equal to the 

amount of colloidal iron in the reclaimed water injected. In any event, some of the material that 

caused clogging of the recharge well could not be 

removed by pumping and surging alone, as one 

might expect if the clogging were purely mechanical. 

Dosing the well with hydrochloric acid after test 

RW7 led to recovery of water high in aluminum, 

iron, and phosphorus (table 7) and to a nearly 50-

percent improvement in specific capacity (Vecchioli, 

1972, p. 95). A second acid treatment applied at the 

end of test RW13 ;esulted in a 25-percent improvement in specific capacity. These redevelopment episodes are described more fully in a following section. 

FLOWMETER SURVEYS 

Attempts were made at using flowmeter surveys 

to identify those zones in the screened interval of 

the injection well that became clogged most readily 

during recharge. These surveys were made with a 

TABLE 7.-Alwninum, it·on, and phosphate concentrations and 

pH of liquid pumped after acid treatment of injection well 

after test RW7 

fAll chemical concentrations are in milligrams per liter. From Vecchioli, 

1972, p. 95] 

Total gallons 

pumped at time Total Total Total 

of sample aluminum ir~m phosphorus pH 

collection (AI) (Fe) as POt (thousands) 

C) 5 0 0.1 

8 94 44 61 0.30 

16 28 15 13 .65 

24 17 12 11 .70 

32 16 10 8.2 .94 

40 12 3.4 7.2 1.00 

48 10 8.3 6.0 1.07 

96 4 7.2 2.2 1.42 

144 2.6 1.9 1.6 1.68 

192 1.8 1.5 .9 1.93 

1 Analysis of acid. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F15 

3-inch Au-type current meter suspended at different 

depths in the recharge well. Flowmeter surveys 

made during pumping and before injection indicated 

that the zone between 440 and 450 feet below land 

surface was the interval of highest yield (Vecchioli 

and others, 197 4, p. 17). The surveys also indicated 

that roughly 60 percent of the yield was contributed 

through the lower half of the screen. (See figure 

10.) 

Iw 

w 

u. 

~ 

w' 

u 

< u. 

a: 

::> 

en 

0 

z 

< ....J 

3: 

0 

....J 

w 

m 

::L 

Ia.. 

w 

0 

In contrast, roughly 60 percent of the flow was 

transmitted through the upper half of the screen 

during injection. This difference was first recognized 

410.-----------~-----------.----------~------------~----------~ 

420 

(c) Injection surveys, 

test RW4 

(b) Pretest pumping surveys, 

test RW4 

430 (a) Initial pumping survey 

440 

450 

460 

470 

480 o-==----------l.2o _______ 4...Lo _________ 6~o ______ so.____ ___ _ 

100 

PERCENTAGE Of TOTAL FLOW 

FIGURE 10.-Depth distribution of flow through well screen during (a) initial flowmeter survey 

before any injection, (b) pumping before test RW4, and (c) injection in test RW4. 
F16 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

by G. D. Bennett (written commun., 1969) during 

the early s·eries of recharge experiments made with 

public-supply water. In all injection tests in which 

flowmeter surveys were made, results differed distinctly from those of the pumping surveys, regardless of the degree to which the injection well was 

clogged. For example, in figure 10, the band of injection surveys repres·ents the spread of five individual surveys made at widely spaced time intervals 

during test RW4. The first flowmeter survey was run 

within 3 hours of the sta~t of injection, when little 

or no clogging had developed; the last survey was 

run after 10 days of injection, by which time the 

specific capacity of the well had decreased by more 

than 40 percent. No time-related trend was apparent 

among the five flowmeter surveys, which suggests 

that the spread re·presents variations in measurement procedure rather than any correlation with the 

degree of well clogging. Similar results were obtained in several other tests. 

The direction of flow apparently controls the relative contribution or acceptance of water at the different depth intervals in the screened zone. A possible explanation may be that the 3-inch-diameter 

current meter that presumably was centered in the 

16-inch-diameter well screen may not have been 

sensing the same proportion of flow through the 

cross section for both directions of flow. The difference between the injection-survey results and the 

pumping-survey results is not great (fig. 10). 

Another explanation may be related to the slight 

vertical gradient in the aquifer when the well is not 

being oper31ted. The head in the aquifer opposite 

the top of the screen is less than the head in the 

aquifer opposite the bottom of the screen. The actual 

difference is not known but is probably less than a 

tenth of a foot. Therefore, when the head in the well 

is drawn down during pumping, a slightly greater 

gradient toward the well is formed in the lower half 

of the screen than in the upp2r half. During injection, when the head in the well is raised, the reverse 

is true; that is, the gradient away from the well is 

steeper in the upper half of the screen than in the 

lower half. Although these differences in gradient 

are slight, they could account at least in part for the 

slight differences in the configuration of the flowmeter surveys. 

In summary, the flowmeter surveys were not useful in determining whether any zones clogged preferentially. The difference between results of surveys 

made during pumping and those made during injection -was at least as great as the differences within 

either group. 

REDEVELOPMENT OF RECHARGE WELL 

PUMPING AND SURGING 

After each injection test, the injection well was 

redeveloped by pumping and surging at different 

rates up to 1,000 gal/min. In general, this restored 

specific capacity only partly. For example, after the 

specific capacity of the well was reduced from 30.3 

to 17.7 (gal/ min) I ft after 10 days of injection in 

test RW4, redevelopment of the well was attempted 

by continuous pumping at varying rates ( 400, 500, 

and 900 gal/min) for 5 days. After the first hour of 

pumping, specific cap,acity improved to about 26 

(gal/min) /ft but increased to only 28.5 (gal/ 

min) /ft after 5 days. The well was then surged 10 

times by pumping at 1,000 gal/min, the maximum 

capacity of the equipment, for 10-minute intervals 

followed by 5-minute shutdown periods. No improvement in specific capacity was noted. This procedure 

was repeated after 2 days of continuous pumping; 

this time 20 surge-and-rest cycles. were applied, but 

without causing noticeable improve·ment. Another 

10 surge-and-rest cycles were ap.plied 2 days later, 

again with no apparent success. 

The longest period of injection uninterrupted by 

redevelopment was 33 days (test RW7), in which 

about 14 Mgal of reclaimed water was injected. Rate 

of injection during this test was 350 gal/min during 

the first 19 days and 200 gal/min during the last 14 

days. The rate decrease was brought about by a 

m·echanical failure of one of the filters at the treatment plant. During this test, the specific capacity 

of the injection well decreased from a pretest value 

of 23.5 (gal/min) /ft to an end-of-test value of 2.5 

(gal/min) /ft. The major cause of clogging in this 

test was attributed to the suspended-solids load of 

the injected water (Ehrlich and others, 1972). 

Redevelopment by pumping began 2 days after 

injection ended. Pumping at a steady rate of 300 

gal/min resulted in improvement of specific capacity, as follows: 

Time since pumping started 

(min) 

Specific capacity 

[(gal/min) !ft] 

10 3.7 

60 5.4 

1,460 5.6 

After pumping for 1 day, the well was shut down 

for 3 hours and then restarted and pumped for 1 

hour at 700 gal/min~ At this rate, the specific capacity improved to 8.1 (gal/min) /ft after 10 

minutes and to 9.3 (gal/min) /ft after 60 minutes. 

Pumping was then halted for 3 weeks to observe 

potential changes in both the chemistry and microbiota of the injected water. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F17 

Pumping was then resumed at 850 gal/min, and a 

specific capacity of 15 (gal/min) /ft was observed 

after 4 hours of pumping. Continued pumping for 

an additional 20 hours at 500 gal/min resulted in no 

further improvement, and an abrupt increase to 900 

gal/min resulted in only a slight improvement, to 

15.5 (gal/min) /ft. The well was then surged 20 

times by pumping at 1,000 gal/min for 10-minute 

cycles, with 2-minute shutdown periods. After pumping overnight at 400 gal/min, the specific capacity 

was observed to be 17.8 gal/min. The same pattern 

of surging was repeated on the following 2 days, 

with only insignificant improvement in specific capacity to 18 (gal/min) /ft. 

The well head was then dismantled for repair of 

an epoxy joint. Because the pump had to be removed 

to make the repair and because increased surging i 

due to stepped increases in pumping rate had 

resulted in substantial improvements to the well's 

specfic capacity, increased agitation within each 

increment of screen was attempted with a double 

surge-block air-pumping technique. The surge-block 

assembly consisted of two sets of flexible washers, 

which fit snugly in the screen, separated by a 2-foot 

length of slotted pipe. The 2-foot section of pipe 

served as the intake for water pumped out of the 

well by means of air-lift pumping. The double surge 

block was worked in a swabbing motion up and 

down the length of the screen in increments of 5 to 

10 feet while water was being pumped from the well 

at 200 gal/min. Presumably the agitation caused by 

the swabbing and pumping was largely confined to 

the 2 feet of well screen opposite the 2-foot interval 

between the surge blocks. At any given interval, the 

water pumped at first was typically extremely 

turbid, but became less so as the swabbing continued. 

Much particulate matter, some of it fine-grained 

aquifer material, was removed during this operation. 

Analysis of a water sample collected early in a 

swabbing run showed it to contain 1,820 mg/L total 

suspended solids, of which 248 mg/L were volatile. 

However, upon reinstallation of the pumping equipment, testing showed little improvement in specific 

capacity. 

One possible reason for the lack of success in improving the specific capacity was that the agitation 

generated by the surge-block swabbing was no 

greater than that generated by starting the turbine 

pun1p. The turbidity of the water pumped during 

swabbing indicates that the agitation during swabbing exceeded that during pumping; however, if 

the increased agitation were confined largely to the 

filter pack of the well and not transmitted to the 

aquifer interface, then the particulate matter removed during the swabbing came primarily from the 

filter pack. This is quite possible because the 10-inchthick filter pack could have dissipated more energy 

vertically than laterally within the interval opposite 

the surge blocks. Hence, if the filter pack had been 

cleaned sufficiently by the preswabbing pumping, so 

as not to contribute significant head losses, further 

cleaning of the filter pack would result in no improvement of the well's specific capacity. In other 

words, the well's specific capacity at this point was 

being controlled primarily by reduction of permeability at the aquifer interface and a short distance 

beyond it, and this zone was apparently not affected 

by the swabbing any more than it had been earlier 

by simple pumping. 

Effectiveness of pumping and surging in restoring 

specific capacity lost during each segment of test 

RW13 is summarized in table 8. During this test, except for an aborted start, injection was terminated, 

and the well was redeveloped by pumping whenever 

the specific capacity of the well decreased to 6 to 7 

(gal/min) /ft. The well was redeveloped seven times, 

and the specific capacity was increased to 12 to 13 

(gal/min) /ft. The amount of water pumped for redevelopment totaled about four percent of the 

amount injected. 

ACID TREATMENT 

In early tests, it was found that the water repumped from the injection well initially had high 

concentrations of iron and phosphate, mostly in particulate form (Vecchioli and Ku, 1972, p. 10). In test 

RW7, high concentrations of aluminum were noted 

also. After the redevelopment attempts by pumping and surging after test RW7, it was thought by 

the authors that chemical deposits might be so firmly 

attached to the mineral framework of the aquifer 

that they could not he loosened by the surging action 

of the repumped water. The mode of formation of 

these deposits was not determined; that is, it is not 

known whether the deposits resulted from purely 

physical filltration of particulate matter or whether 

they resulted from coprecipitation of iron, aluminum, 

and phosphate at the interface or whether the process 

was a combination of the two. In any event, theresidual deterioration in well capacity was thought by 

the authors to result largely from persistence of 

these compounds at the· aquifer interface. Because 

many compounds of iron and aluminum are soluble 

in hydrochloric acid, the well was dosed with acid in 

an attempt to dissolve or at least dislodge these 

compounds. 
F18 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

TABLE B.-Redevelopment data, test RW13, October 24,1972, to May 11, 1973 

(From Sulam, 19731 

Redevelop- ment 

episode 

2 

3 

5 

7 

8 

9 

10 

11 

Date 

10-27-72. 

10-29-72 

Subtotal 

12-11-72 

12-12-72 

Subtotal 

1- 2-73 

1-22-73 

1-23-73 

Subtotal 

2- 5-73 

Subtotal 

2- 9-73 

2-15-73 

2:....16-73 

Subtotal 

2-23-73 

2-27~73 

3- 9-73 

Subtotal 

4- 6-73 

Subtotal 

4-30-73 

5- 1-73 Subtotal 

Number 

of times pumped 

~~:.~/~: Rate Total gals 

(minutes) [ (galjmin/ft) pumped 

10 1{) 900 90,0(}0 

1 120 400 48,000 

------------------------------- 138,000 

1 60 500 30,000 1 00 900 54,000 4 10 900 36,000 {) 10 900 54,000 1 240 400 96,000 

------------------------------- 270,000 

30:> 400 120,000 

1 10 500 30,000 10 10 900 90,000 

1 240 400 96,000 

------------------------------- 216,000 

1 60 500 30,00·0 10 10 900 90,000 1 240 400 96,000 

------------------------------- 216,000 

'1 60 500 30,000 

10 10 900 90,00{' 1 240 400 96,000 1 60 400 24,000 

5 10 900 45,000 1 240 400 96,000 

------------------------------- 381,000 

220 800 1 176,000· 

120 800 96,000 

10 900 18,000 30 8{)0 24,000 

------------------------------- 42,000 

1 69 400 27,600 4 10 900 36,000 

1 120 400 48,000 

------------------------------- 111,600 

5 10 900 45,000 1 240 400 96,000 

------------------------------- 141,000 

1 After sodium hypochlorite solution was injected. 

A 2,400-gallon slug of 32-pereent commercialgrade hydrochloric acid was injected into the well 

by way of the annular-space observation well. This 

volume was determined to be suffic.ient to displace 

all water within the sc.reened zone of the injection 

well and the annul~r-space well, as well as the water 

within the filter pack and within the first few inches 

of formation. 

After the acid was injected, the turbine pump 

was turned on momentarily a few times to surge 

the well and thus assure even distribution of the 

acid around the well. The acid was then left standing in and around the well screen overnight (more 

than 12 hours) . The following day, the pump was 

turned on, and the well was pumped continuously 

at 800 gal/min. An immediate improvement in specific capacity was noted. After 4 hours of pumping, 

the specific capacity was 26.5 (gal/min) /ft-an imSpecific capacity 

[ (galjmin) /ft] 

Before After redevelop- redevelop- Change ment ment 

18 25.8 -f-7.8 

6 

14.7 -f-8.7 

9.7 11.7 -f-2.0 

7.1 

13.0 -f-5.9 

7.1 

13.0 -f-5.9 

6.9 

11.6 -f-4.7 

12.0 -f-5.1 

12.6 

7.0 

13.3 -f-6.3 

11.0 12.7 -f-1.7 

Cumulative 

gals 

pumped 

138,000 

408,000 

528,000 

744,000 

960,000 

1,341,000 

1,517,000 

1,613,000 

1,655,000 

1,766,600 

1,766,600 

1,907,600 

Remarks 

Specific 

capacity 

test. 

Specific 

capacity 

test. 

Specific 

capacity 

test. 

Specific 

capacity 

test. 

Repeated 

specific 

capacity 

test. 

Specific 

eapacity 

test after chlorine 

treatment. 

provement of almost 50 percent over what it had 

been before the acid treatment and a 12-percent improvement over wha.t it had been before test RW7. 

High concentrations of iron, aluminum, amd phosphorus were noted in the liquid pumped from the 

well, as discussed in a previous section "Chemical Clogging." 

The well was similarly treated with acid at the 

end of test RW13, and specific capacity improved 

from 20 to 25 (gal/min) /ft. 

BACTERICIDE TREATMENT 

In test RW8, about 5 Mgal of unchlorinated reclaimed water was injected at 340 gal/min. During 

this test, the specific capacity of the injec,tion well 

dropped from a pretest value of 26.5 to 11 (gal/ 

min) /ft. Most of the clogging in this. test was attributed to a buildup of microbial slime within the 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F19 

filter pack and perhaps a short distance into the formation (Ehrlich and others, 1973). A head difference of about 12 fe~et between the injection well and 

the annular-space well was noted toward the end of 

the test; this reflects the slime buildup within the 

filter pack. 

Redevelopment by pumping at rates up to 1,000 

gal/min was effective in restoring the specific capacity to only about 23 (gal/min) /ft. The pumping 

also resulted in a removal of all but about 0.5 foot 

of head difference between the injection well and 

annular-space well when pumping at about 400 gal/ 

min. Before this last injection test, this head difference had been only 0.1 foot at a pumping rate of 

400 gal/min. As most of the residual clogging was 

thought by the authors to be of bacterial origin, 

shock chlorination was considered a reasonable 

remedial measure. 

Chlorine was added to the well by injecting 33,000 

gallons of aquifer water into which a 15-percent solution of sodium hypochlorite was mixed; this resulted 

in a total chlorine residual of 200 mg/L. This volume was sufficient to displace all water within the 

well casing below the point of injection, the screened 

interval, the filter pack, and the format,ion to a radial 

distance of almost 8 feet from the axis of the well. 

The chlorine solution was left standing overnight 

(more than 8 hours). The following day, after 4 

hours pumping, the specific capacity was 26.5 (gal/ 

m!in) /ft, which was equal to the specific capacity before injection of the unchlorinated reclaimed water. 

Also, the abnormal head difference between the annular-space well and the injection well had disappeared. Hence, the chlorine dosing was effective in 

destroying the residual bacterial slime around the 

injection well. 

The well was similarly treated with chlorine after 

test RW9. Postinjection redevelopment by pumping 

had restored specific capacity to 24.6 (gal/min) /ft. 

After the chlorine treatment, the specific capacity 

was improved to 27.1 (gal/min) /ft. 

The well was treated a third time with chlorine 

after segment 12 of test RW13. However, this treatment produced no significant improvement in specific capacity. 

The recharge well was dosed with a commercial 

am.monium compound designed to control the growth 

of nuisance organisms in wells after test RW 4 and 

after considerable redevelopment by pumping and 

surging. This treatm·ent resulted in a 7 -percent improvement in specific capacity (Vecchioli and Ku, 

1972, p. 10). A later treatment did not produce any 

improvement, however. 

RESTING 

Some impvovement in specific capacity resulted 

from biodegradation of the clogging materials during periods after injection in which the well was 

rested for s·everal weeks. Evidence for thls phenomenon was observed after tests RW7, RW10, and 

RW13. 

In test RW7, an increase in pumping rate from 

700 gal/min to 850 gal/min after 3 weeks of rest 

was acCiompanied by a more than 60-percent improvement in specific capacity. This increase is probably more than would have occurred had the pumping rate been increased before any resting period. 

A£ter test RW10, the injection weB was pumped 

at 300 gal/min for 110 minutes immediately after 

injection ended. The specific capacity was about 

20 (gal/min) /ft. The well was then rested for 35 

days, after which it was again pumped at 300 gal/ 

min for about 60 minutes. Specific capacity then was 

25.9 (gal/min) /ft. High bacterial counts, high dissolved sulfide concentrations, and high total organic 

carbon concentrations. in the recovered water suggest that bacteria were solubilizing the· organic part 

of the clogging mat.erials during the resting period 

(Ehrlich and others, 1979). 

Similarly, at the end of test RW13, the specific 

capacity of the well was 8.6 (gal/min) /ft. The well 

was rested for almost 1 month before redevelopment began. Highly turbid, odiferous water similar 

to that observed in test RW10 was pumped initially. 

Pumping and surging after the 1-month test restored the specific capacity to between 19 and 20 

(gal/min) /ft, whereas similar redevelopment attempts immediately or within a few days after different segments of injection resulted in sp,ecificcapacity imp:rovement to only 12 or 13 (gal/ 

min) /ft. 

SUMMARY 

Public-supply water and water reclaimed through 

tertiary treatment of sewage were injected into 

the Magothy aquifer at Bay Park, N.Y., in a series 

of 19 artificial-Techarge experiments from 1968 to 

1973. Injection was done through a well screened 

from 418 to 480 feet below land surface. Injection 

rates ranged from 185 to 400 gal/min, and tests 

ranged from. 2 to 33 days in length, except for the 

last experiment, in which almost 42 Mgal of reclaimed water were injected intermittently in 18 

segments over a 6-month period. Selected treatments were ap·plied to the injectant in some tests to 

evaluate their effect on well clogging or on geochemi-
F20 ARTIFICIAL-RECHARGE EXPERIMENTS, BAY PARK, LONG ISLAND, NEW YORK 

cal reactions within the ·aquifer. The water injected 

was repumped after each test. 

Head buildup. in the aquifer during injection 

virtually mirrored drawdown during pumping of 

comparable magnitude and time. However, the injection well and (or) contiguous part of the aquifer 

became clogged to varying degre·es in each test and 

resulted in excessive head buildup in the injection 

well. The amount of excessive head buildup and corresponding decrease in specific capacity differed 

widely from test to test. Maximum reduct;ion in specific cap·acity, from 23.5 to 2.5 (gal/min) /ft, was 

during injection of 14 Mgal of reclaimed water. 

Clogging of the well was due primarily to suspended solids in the injectant. Suspended-solids concentrations above 1 mg/L, as Si02 , measured in 

terms of turbidity, caused disproportionately higher 

rates of clogging than concentrations below 1 mg /L. 

Clogging due to microbial growth was insignificant 

as long as a total residual chlorine level of about 2 

mg/L was maintained in the inje~ctant. However, in 

a 10-day test in which unchlorinated reclaimed wate1r 

was injected, clogging due mainly to microbial factors was more severe than in comparable tests in 

which water of higher turbidity was injected. Compounds of iron, aluminum, and phosphorous contributed to clogging, but the e~tent to which these 

compounds precipitated within the aquifer relative 

to the particulate content of the injectant remained 

unresolved. 

Redevelopment of the recharge well by pump•ing 

and surging was effective in partly restoring the 

specific capacity los!t during an injection test. Maximum pumping rate was limited by the equipment to 

1,000 gal/min. Dosing the well with hydrochloric 

acid helped remove clogging material that could not 

be dislodged by pumping alone. Specific capacity improved from 18 to 26.5 (gal/min) /ft after the first 

acid treatment and from 20 to 25 (gal/min) /ft after 

a second treatm.ent. Dosing of the well with solutions of sodium hypochlorite resulted in a 10- and 

15-percent improvement in sptecific capacity on two 

occasions, but produced no significant imp·rovement 

on a third. Dosing with an ammonium compound 

bactericide resulted in a 7 -percent improvement in 

specific capacity, but a later, similar ap·plication 

produced no improvem.ent. Redevelopment by pumping and surging was enhanced if the injection well 

was rested for s.everal weeks after injection; this 

was because of biodegradation of the clogging materials during the rest periods. 

REFERENCES CITED 

American Water Works Association, Task Group 2440-R on 

Artificial Ground-Water Recharge, 1965, Experience with 

inje·ction wells for artificial ground-water recharge: 

American Water Works Association Journal, v. 57, no. 5, 

p. 629-639. 

Cohen, Philip, and Durfor, C. N ., 1967, Artificial-recharge ex-· 

periments utilizing renovated sewage-plant effluent-a 

feasibility study at Bay Park, New York, U.S.A.: International Association of Scientific Hydrology Publication 

72, p. 194-199. 

Cohen, Philip, Franke, 0. L., and Foxworthy, B. L., 1968, An 

atlas of Long Island's water resources: New York Water 

Resources Commission Bulletin 62, 117 p. 

Cohen, Philip, and Kimmel, G. E., 1970, Status of salt-water 

encroachment in 1969 in southern Nassau and southeastern Queens, Long Island, New York, in Geological Survey Research 1970: U.S. Geological Survey Professional 

Paper 700-D, p. D281-D286. 

Ehrlich, G. G., 1972, Role of biota in unde·rground waste 

injection and storage, in Cook, T. J., ed., Underground 

Waste Management and Environmental Implications: 

American Association of Petroleum Geologists Memoir 

18, p. 298-307. 

Ehrlich, G. G., Ehlke, T. A., and Vecchioli, John, 1972, Microbiological aspects of ground-water recharge-injection of 

purified chlorinated sewage effluent, in Geological Survey 

Re-search 1972: U.S. Geological Survey Professional 

Pap·er 800-B, p. B241-B245. 

Ehrlich, G. G., Ehlke, T. A., and Vecchioli, John, 1973, Microbiological aspects of ground-water recharge-injection of 

purified unchlorinated sewage effluent at Bay Park, Long 

Island, New York: U.S. Geological Survey Journal of 

Research, v. 1, no. 3, p. 341-344. 

Ehrlich, G. G., Ku, H. F. H., Vecchioli, John, and Ehlke, T. 

A., 1979, Microbiological effects of recharging the 

Magothy aquifer at Bay Park, New York, with tertiarytreated sewage: U.S. Geological Survey Professional 

Paper 751-E, 18 p. 

Faust, S. D., and Vecchioli, John, 1974, Injecting highly 

treated sewage into a deep sand aquifer: American 

Water Works Ass·ociation Journal, v. 66, no. 6, p. 371-377. 

Franke, 0. L., 1968, Double-mass-curve analysis of the effects 

of sewering on ground-water levels on Long Island, New 

York, in Geological Survey Research 1968: U.S. Geological Survey Professional Paper 600-B, p. B205-B209. 

Garber, M. S., and Sulam, D. J., 1976, Factors affecting declining water levels in a sewered area of Nassau County, 

New York: U.S. Geological Survey Journal of Research, 

v. 4, no. 3, p. 255-265. 

Koch, Ellis, Giaimo, A. A., and Sulam, D. J., 1973, Design 

and operation of the artificial-recharge plant at Bay 

Park, New York: U.S. Geological Survey Professional 

Paper 751-B, 14 p. 

Ku, H. F. H., Vecchioli, John, and Ragone·, S. E., 1975, 

Changes in concentration of certain constituents of treated 

waste water during movement through the Magothy 

aquifer, Bay Park, New York: U.S. Geological Survey 

Journal of Research v. 3, no. 1, p. 89-92. 

Lusczynski, N. J., and Swarzenski, W. V., 1966, Salt-water 

encroachment in southern Nassau and southeastern 

Queens Counties, Long Island, New York: U.S. Geological Survey Water-Supply Paper 1613-F, 76 p. 
HYDRAULIC EFFECTS OF RECHARGING THE MAGOTHY AQUIFER F21 

Perlmutte-r, N. M., and Geraghty, J. J., 1963, Geology and 

ground-water conditions in southern Nassau and southeastern Queens Counties, Long Island, New York: U.S. 

Geological Survey Water-Supply Paper 1613-A, 205 p. 

Perlmutter, N. M., Pearson, F. J., Jr., and Bennett, G. D., 

1968, Deep-well injection of treated waste-wate-r-an experiment in re-use of ground water in western Long 

Island, in New York State Geological Association Guidebook 40th Ann. Mtg: p. 221-231. 

Peters, J. H., 1968, Supplemental water supply by tertiary 

treatment and recharge, in Proceedings of the Fourth 

American Water Res·ources Conference: American Water 

Resources Association Proceedings Series, no. 6, p. 330-

343. 

Peters, J. H., and Rose, J. L., 1968, Water conservation by 

reclamation and recharge: American Society of Civil Engineers Proceedings, Journal of Sanitary Engineering 

Division, v. 94, No. SA4, p. 625-639. 

Ragone, S. E., 1977, Geochemical effects of recharging the 

Magothy aquifer, Bay Park, New York, with tertiarytreated sewage: U.S. Geological Survey Professional 

Paper 751-D, 22 p. 

Ragone, S. E., Vecchioli, John, and Ku, H. F. H., 1973, Shortterm effe·ct of injection of tertiary-treated sewage on iron 

concentration of water in Magothy aquifer, Bay Park, 

New York: American Association of Petroleum Geologists, Second International Symposium on Underground 

Waste Management and Artificial Recharge, v. 1, p. 273-

290. 

Ragone, S. E., and Vecchioli, John, 1975, Chemical interaction 

during deep-well :recharge, Bay Park, New York: Ground 

Water, v. 13, no. 1, p. 17-24. 

Ragone, S. E., Ku, H. F. H., and Vecchioli, John, 1975, Mobilization of iron in water in the Magothy aquifer during 

long-term recharge with tertiary-treated sewage, Bay 

Park, New York: U.S. Geological Survey Journal of Research, v. 3, no. 1, p. 93-98. 

Sulam, D. J., 1973, Summary log of injection test RW13, Bay 

Park, N.Y.: U.S. Grological Survey open-file report, 23 p. 

-k U.S. GOVERNMENT PRINTING OFFICE: 1980 0- 311-344/27 187 

Temporary [New York] State Commission of Water Supply 

Needs of Southeastern New York, 1972, Scope of public 

water supply needs: Albany, New York, p. 142-144. 

Truesdall, A. H., and Jones, B. F., 1974, WATEQ, a computer program for calculating chemical equilibria in 

natural waters: U.S. Geological Survey Journal of Research, v. 2, no. 2, p. 233-248. 

VecchioH, John, 1970, A note on bacterial growth around a 

recharge well at Bay Park, Long Island, New York: 

Water Resources Research, v. 6, no. 5, p. 1415-1419. 

---1972, Experimental injection cxf tertiary-treated sewage 

in a deep well at Bay Park, Long Island, New York-a 

summary of early results: New England Water Works 

Association Journal, v. 86, no. 2, p. 87-103. 

Vecchioli, John, Bennett, G. D., Pearson, F. J., Jr., and Cerrillo, L. A., 1974, Geohydrology of the artificial-recharge 

site at Bay Park, Long Island, New York: U.S. Geological Survey Professional Paper 751-C, 29 p. 

Vecchioli, John, Ehrlich, G. G., and Ehlke, T. A., 1972, Travel 

of polluti10n-indicator bacteria through the Magothy aquifer, in Geological Survey Research 1972: U.S. Geological 

Survey Professional Paper 800-B, p. B237-B239. 

Vecchioli, John, and Giaimo, A. A., 1972, Corrosion of wellcasing and screen metals in water from the Magothy 

aquifer and in injected reclaimed water, Bay Park, Long 

Island, New York, in Geological Survey Research 1972: 

U.S. Geological Survey Professional Paper 800-B, p. 

p. B247-B251. 

Vecchioli, John, and Ku, H. F. H., 1972, Preliminary results 

of injecting highly treated sewage-plant effluent into a 

de€.'P sand aquifer at Bay Park, New York: U.S. Geological Survey Professional Paper 751-A, 14 p. 

Vecchioli, John, Oliva, J. A., Ragone, S. E., and Ku, H. F. H., 

1975, Wastewater reclamation and recharge, Bay Park, 

New York: American Society of Civil Enginee·rs, Journal 

of the Environmental Engineering Division, v. 101, no. 

EE2, Proceedings Paper 11232, p. 201-214. 

Deep-Well Artificial-Recharge 

Experiments at Bay Park, 

Long Island, New York 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 751 

This volume was published 

as separate chapters A-F 
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary 

GEOLOGICAL SURVEY 

H. William Menard, Director 
CONTENTS 

[Letters designate the chapters] 

(A) Preliminary results of injecting highly treated sewage-plant effluent into a deep sand aquifer at Bay 

Park, New York, by John Vecchioli and Henry F. H. Ku. 

(B) Design and operation of the artificial-recharge plant at Bay Park, New York, by Ellis Koch, 

Anthony A. Giamo, and Dennis J. Sulam. 

(C) Geohydrology of the artificial-recharge site at Bay Park, Long Island, New York, by John 

Vecchioli, G. D. Bennett, F. J. Pearson, Jr., and L. A. Cerrillo. 

(D) Geochemical effects of recharging the Magothy aquifer, Bay Park, New York, with tertiarytreated sewage, by Stephen E. Ragone. 

(E) Microbial effects ofrecharging the Magothy aquifer, Bay Park, New York, with tertiary-treated 

sewage, by Garry G. Ehrlich, Henry F. H. Ku, John Vecchioli, and Theodore A. Ehlke. 

(F) Hydraulic effects of recharging the Magothy aquifer, Bay Park, New York, with tertiary-treated 

sewage, by John Vecchioli, Henry F. H. Ku, and Dennis J. Sulam.