# GROUND-WATER HYDROLOGY OF VOLUSIA COUNTY, FLORIDA, WITH EMPHASIS ON OCCURANCE AND MOVEMENT OF BRACKISH WATER

By A. T

. Rutledge

U.S. GEOLOGICAL SURV EY Wa ter-Resources Invest igations Report 8 4- 4206

In cooperation with VOLUSIA COUNTY , FLORIDA

1985

## U.S. DEP A RT MENT OF THE INTERIOR DONALD P A UL HODEL, Secretary

U.S. GEOLOGICAL SUR VEY Dallas L. Peck, Director

Th e use of firm, trade , and b ra nd na me s in thi s rep o rt is fo r i dentificatio n p u rpo s e so n ly and doe s n o t con s titute end orsement by th e U

. S. Geo l ogi cal Survey.

For add itio nal informatio n wri t e to: Di stri ct Chi e f U.S. Geological Su rvey Su ite 3 015 227 N. Brono ugh Stre et Tallahassee, FL 323 01 Co pies of th is re port can be purchase d from: U. S. Geo l ogical Survey Branch of Info rmation Services Box 25 286 De nver , CO 802 25-028 6 800-ASK-USGS Additional information abou t water r esour ces in Florida is available on the W

o rld W ide W e b at http://fl.water

. usgs.gov

# CONTENTS
Abstract

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... ..... .... 1 Introduction

. . .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... .... ..... .... ..... .... ..... .... 2

Background and problems

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... 3 Purposes and scope
....................... ...................... ....................... ...................... ................ .. ..... .... ..... .... ..... .... 4 Previous work

..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... ..... .... 5 Data collection

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... ..... .... 5 W

e ll -numbering system

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... .... ..... .... ..... .... 5 Environmental setting

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... 6 Climate

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... ..... .... 6 Geography

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .. ... .... ..... .... ..... .... ..... .... 6 Geology

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... 9 Hydrogeology

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... ..... .... 9 Ground-water use

. . .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... . ... ..... .... ..... .... ..... .... 14 S urficial aqui fer

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .. ... .... ..... .... ..... .... ..... .... 16 F l oridan aquifer system

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... 16 W

ater

- level trends..

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... ..... .... 19

S urficial aqui fer

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .. ... .... ..... .... ..... .... ..... .... 19 F l oridan aquifer system

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... 27 W

ater budget

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... ..... .... 34 Surficiallayer

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... .... ..... .... ..... .... ..... .... 34 Rainfall and evapotranspirati on
. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... 34 Streamflow

.. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .. ... .... ..... .... ..... .... ..... .... 34 V

ertical leakage

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... ..... .... 36 W

ater budget of th e surficial layer

. . .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... 38 F l oridan aquifer system

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... 38 S p eci f ic capacities

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... ..... .... 40 T

esting estimates of flow in the Fl oridan aquifer system against recharge estimates

. ..... .... ..... .... ..... .... 42 W

ater budget of th e Floridan aquifer system

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... 45 Concepts of brackish water occurrence and movement

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... 46 Baseline salinity

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... .... ..... .... 46 Chloride concentration change ratio

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .. .. ..... .... ..... .... 46 Physical nature of freshwater

- saltwater interface

.. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... 49 Brackish water in the surfi cial aquifer

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... . ... ..... .... ..... .... 51 Present distribution

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... ..... .... 51 Comparision of past and present

. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... 51 Brackish water in the Fl oridan aqui fer sy stem

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... 51 Present distribution

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . .... ..... .... ..... .... ..... .... 51 Comparision of past and present

. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... 56 Nonpublic-supply wells

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... .... ..... .... ..... .... 56 Public-supply wells

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... . ... ..... .... ..... .... ..... .... 60 Ef fects of management alternatives on movement of brackish water

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... 67 S urficial aqui fer

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .. ... .... ..... .... ..... .... ..... .... 67 F l oridan aquifer system

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... .... ..... .... ..... .... 67

Co nte n ts iiiSummary

..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. .... ..... .... ..... ..... .... ..... 74 Selected references
.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .. .. ..... .... ..... ..... .... ..... 76 Supplemental data --chl oride concentrations in public-supply wells

.... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... .... . 7 8

ILLUSTRA TIONS Figure 1

. Mapshowing lo cati on of V o lu si a County and ridg e areas and major physio graphi c features in V

o lusia County

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . ..... .... ..... 3 2. Hydrograph s howzing averag e yearly rainfal lduring5-ye ar intervals at thre e rain gages, 1951-80

. . ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... ..... .... ..... 8 3. Map showing topography in V o lusi a County

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 10 4. Geologic sections

. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ... .. ..... .... ..... 1 1 5

. Mapshowing areas of artesi anflow from the Fl oridan aqui fer system in V o lusia County , September 1982

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... . .... .... ..... 13 6. Map showing altitude of top of Floridan aquifer system

.... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 15 7. Map showing distribution of surf icial-aquifer we lls that are used for irrigation purposes

.. .... ..... 17 8. Map showing distribution of surficial-aquifer wells that are used for domesti c purposes
... .... ..... 18 9. Map showing locati ons of publ ic-supply wells and available water

- use rates, 1955

. ..... ..... .... ..... 20 10. Map showing locati ons of publ ic-supply wells and water

- use rates, 1980

.... .... ..... .... ..... ..... .... ..... 21 1 1

. Map sh o wingdistributio n of Floridanaqui fer sy stem w e lls that areuse d for irrigation and whic h
are greater than 4 inches in diameter

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... . .... 22 12

. Map sh o wingdistributio n of Floridanaqui fer sy stem w e lls that areuse d for irrigation and whic h are 4 in ches or less in diameter

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .. .. ..... 23 13

. Map sh o wingdistributio n of Floridanaqui fer sy stem w e lls that areuse d for domestic purpos es 24 14. Map showing locati ons of the major artifi c ial drainage systems inV o lusia County

.. ..... ..... .... ..... 25 15

. Hy dro graph s ho wingdailymaximum water leve ls in surf icial-aquifer well s 910-1 10-13 and 913- 1 1 6-01, January 1978- December 1983

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 26

iv C o n t entsFigure 16

. Hydrograp hsh owing m onthlyrainfall fo r th e 1 8 -m onth period s upto and in cludingmo nth sof three mass water

- level measurementson F l oridan aquifer system wells...

..... .... ..... .... ..... .... ..... .... ..... 28 17

. Map sh o wingpo tentio me tric surface of th e upper part of the Floridanaquif er sytem, Novemb er 1955

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 29 18

. Map sh o wingpo tentio me tric surface of th e upper p art o f th e Floridan aqui fer sys tem , Septemb er 19 82 , andarea inwhic h thepo tentiometric surface declined morethan 10 feet from November 1955 to September 1982..

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 30 19

. Map sh o wingpo tentio me tric surface of th e upper p art of th e Flo ridanaquifer s y stem , May 1981

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 31 20. Hydrographs showing water

- level records of fiveFloridan aquifer system wells, 1955-83

. ..... ... 32 2 1

. Hydrographs showingdailywater lev e l s in four F l oridanaqui fer system wells, January19 81

- December 1983

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 33 22. Map showing surface-drainage features, stream-g aging stations, and raingages
.... .... ..... .... ..... ... 35 23. Map showing ratios of specific capacity tolength o f op en ho le for Fl oridanaqui fer sy stem wells of 6-inch and larg er diameters
. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 41 24

. Map sh o wingpo tentio me tric surface of th e upper p art o f th e Floridan aqui fer sys tem , Septemb er 1982, and four drainage areas for which flowanalyses are given

. .... ..... .... ..... .... ..... .... ..... .... ..... ... 43 2 5

. Hydrographs showingperio dic record s of chlori de concentration in water from Floridan aquifer system wells that have not been used for public supply , Januar y 1978-June 1979

.. .... ..... .... ..... ... 47 2 6

. Hydrographs showingperio dic record s of chlori de concentration in water from Floridan aquifer system wells that have not been used for public supply , 1953 -83

. .... ..... .... ..... .... ..... .... ..... .... ..... ... 48 27. Concep tual cross sec tions showing the occurrence of bracki sh ground water and the mov ement of brackish water caused by pumping

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... 50 28. Map showing th e chloride concentration in the surficial aquifer and chloride concentration change ratios for water from wells that tap the surficial aquifer

... .... ..... .... ..... .... ..... .... ..... .... ..... ... 52 29. Diagram showing average ionic composition of water from eight surficial-aquifer wells in central V o lusia County

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .. .. ..... ... 53 30

. Map sh o wingchlo ride c on centration in water from wells that tap the upper p art of the Floridan aqui fer system
.. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .. .. ..... ... 54 3 1

. Mapshowing estimated maximum thickness of zone in the F l oridan aquifer system in which the water is fresh or slightly brackish

... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... .... . ... 55

Co nt ents IVFigure 32. Di agram showing average ionic compositions of water inthre e parts of the Floridan aquifer system

. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ... . ..... ..... .... ..... 57 33

. Map sh o winglocatio n sof 21 Floridan aqui fer sys tem wells fo r whichan alys es of io n concentrations inwater are given

.... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 58 34

. Map sh o wingchlo ride -con centratio n ch ange ratios for wells open to the Flori dan aquifer system that have not been used for publicsupply

. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 59 35

. Map sh o wingchlo ride -con centratio n ch ange ratios b ase d onolddata v ersu sdata from March-April 1982 for public -supply wells

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 64 36

. Map sh o wingchlo ride -con centratio n ch ange ratios b ase d onolddata v ersu sdata from August 1982 for publ ic-supply wells

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... .... . 6 5 37

. Map sh o wingchlo ride -con centratio n ch ange ratios b ase d onolddata v ersu sdata from December 1982 for public-supply wells

.. .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 66 3 8

. Hydrograph s showingchloride conc entration of water from three Dayton a Beachpublicsupply wells, 1974-83

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... ..... 68 39. Hydrographs showing chloride concentration of water from four Holly Hill public-supply well s, 1979-83

. . ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... . .... ..... .... ..... 69 40

. Map sh o wingpublic-supplywells in u se during19 54 -5 7 and chlorideco nc entration sof water from public-supply wells in northeast V o lusi a County

........... ....................... ....................... ......... 70 41

. Map sh o wingpublic-supplywells in u se during19 82 and chlorideco nc entratio n sof water fro m publ ic-supply wells in northeast V o lu sia County

.. ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 71 42. Concep tual cross sec tion s hoving movement of fres hwater

- saltwater interface under pumping wells

... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .. .. ..... ..... .... ..... 73

T

ABLES

T

a

ble 1. Data on wells referenced in thi s report which have been inventoried

. ..... .... ..... .... ..... .... ..... ..... .... ..... 7 2. Estimated ground-water use in V o lu sia County

.... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... ..... 14 3. Measured and estimated average streamflow for six gaging stations

... .................. .................. ..... 37 4. Estimated water budget of the surficial layer for each topograp hy-hydrology type

................. ..... 39 5. Estimated water budget of the F l oridan aquifer system in V o lusia County

... .... ..... .... ..... ..... .... ..... 45 6. Chl o ride concentrations in water from wellsin the monitoring network sugg ested in th e northwest V o lusia County report

..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... .... ..... ..... .... . .... 61

vi C o n t ents

### C ONVERSION F A CT OR S For use of those readers who may prefer to use metric unitsrather than U.S. inch-pound units, the conversion factors fo r the terms used in this report are listed below: Multiply By Length T oobtain inch (in.) 2 5.4 m illimeter (mm) foot (f t) 0.3048 meter (m) mi le (mi) 1. 609 kil o me ter (km) Area square foot (f t2 

### ) 0.0929 squa re met e r (m 2 

### ) square mile (mi 2 

### ) 2.590 squa re kil o met e r (km 2 

### ) Flow gallon per minute (gal/mm) 0.003785 cubic meter per minute (m 3

### /m in) million gallons per day (Mgal/d) 0.0438 cubic meter per second (m 3

### /s) inch per year(in/yr) 2 5.4 millimeter per year (m 3

### /s) cubic-foot per second (f t 3

### /s) 0.02832 cubic meter per second (m 3

### /s) T ransmissivity foot squared per day (f t2 

### /d) 0.0929 meter square d per day (m 2 

### /d)

Co nt ents IVGR OUND- W A

TER H Y D ROLO G Y O F VOLUSIA C OUNT Y , FLORIDA, WITH EMP HASIS ON OC C URREN C EAND MOVEMENT OF B RA C KISH W A

TER

By A. T. Rutledge

ABSTRACT
Volus ia County i s a 1,200

— square —mile are a in east

— c entral Floridawhich inclu des the communi ties of DaytonaBeach, Ormond Beach, New Smyrna Beach, Delan d, and Deltona. The area is orient ed toward tourism, especi ally along the coast
. The t wo aquifers und erlying the are a are the uncon fined surficial aquifer and t he confined Flo ridan aquifer sy stem. The surfi cial aquifer con sists of sand, clay, and shell beds of Pleistocene and H olocene age, and th e Floridan aquif er system con sists of lime stone and dolo mite of Eocen e age. The tw o aqui­ fers are sep arated by confining clay beds of Miocen e o r Pl iocene age. Both aquif ers contain good qualit y w ater in most of Volusia County , b ut brackish water is present in the eastern and we stern fri nges of the county inthe surfi­ cial a quifer and in the upp er zones of the Flori dan aquifer system p resently tappe d by w ells. Saltwater is prese nt throughout the county in the re latively untap ped lower zones of the Floridan aquifer system. Developm ent in the fringes has caused movement of the brackish water. There is a need for a n under standing of th is movement so that future pro blems can be av oided.
Aver a ge ground

- water w i thdrawal in 1980 in Volusia County was 6 6 million gallo ns pe r day, of which 30 was for public supply, 24 was fo r agri cultural irrig ation, and 12 was for other uses. Grou nd

—water use quadrupl ed b etween 1955 and 1980. More than 9 5 percen t of the ground water pumped is from the Floridan aquif er system.
Water l evels in Floridan aquif er system wells decline d m ore than 10 feet over an ar ea of 70 square miles from 1955 to 1 982. This drawdown, which occurred in the are a of Ormond Bea ch, DaytonaBeach, and Por t Orange, was ca used by pump­ ing.
The annua l w ater budget of the surficial layer cons ists of 53 inches rain- fall, 1 inch upward leakage from the Florid an aqu ifer system, 0.5 inch recharge from Floridan aquifer system withdraw als, and 0.5 inch stream inflow, counter- balan ced with 39 inc hes evapotranspi ration, 11 inch es stream outflo w, and 5 inche s downward leak age to the Flor idan aquifer sy stem.

1The annual water bud get of the Flori dan aquife r system consists of 5 inches downw ard leakage inf low, 1 inch upw ard leakage out flow, 1 inch ho rizontal inflo w, 1.5 inches horizonta l outflo w, 2.5 inches discharge from springs and flowi ng wells, and 1 inch pumpage.
Brack ish wa ter mo vement, or in trusion, apparently is occurring in the surf­ icial a quifer on the barrier isl and in the northeast part of th e study area. Intru sion is probably occurri ng in other sections of the barri er island, but there is no evidence that it is occ urring in inland a reas. Futu re intrusio n is likel y i n t he surficial aquifer on the bar rier island as groundwate r w ithdraw­ als i ncrease. There is little evidenc e that intru sion i s occu rring uniformly over large areas i n t he Floridan aquifer syst em. Most nonpublic supp ly wells have not exhib ited long

— ter m changes i nsalinity, although sign ificant increa ses in chlor ide concentration in wate r f rom five nonpublic supply we lls in the coastal area of Or mond Beach and Daytona Beac h may be associated with grou nd

—water withd rawals in northeast Volus ia C ounty. Vertical intrus ion is occurring at sites o f p ublic supply pumping bec ause these wells are usual ly deeper, are pumpe d a greater amou nt of the time, and are pumped at higher rates. Many of these we lls in t he e astern and western fringes of Volu sia County have been aband oned and replac ed by new wells closer to the central part of the county.
Water

—management p ractices that may minimi ze future m ovement of brackish water in the Floridanaquifer system i nclude minimizin g well depths, mi nimizing drawd own, installing wel ls where the freshwat er zone is thickest, in creasing head in the freshwater zone byusing injection wells, andreducing head inthe saltw ater zone. Drawdown can be re duced by increasing the number of supply wells per desired water

—use rat e. Minimizing well depth ma y be the sing le most effec tive step again st intrusion.

INTRODUCTION Backg round and Probl ems
Volus ia county, in e ast

— central Flo rida, is oriente d toward touris m, espe­ ciall y along the coast. The 1,200

— square —mile count y i s 1 5 m iles north or Orlan do and includes the coastal communities of Daytona Beach, Ormond Beach, and New Smyrna Beach in addit ion to the inland communities of De Land and Del­ tona (fi g. 1). Rapid population grow th has greatly increased dem and on public — water suppli es. The two aquifers that supply most of the water are the Floridan aquif er syste m, a limestone aquifer under artesian conditions in Volusia Count y, and the surficial aquifer, an unconfined sand aquifer. Although both conta in go od qua lity water in mo st of Volus ia Cou nty, brackish water is present in the eas tern and western fringes o f the county inthe surficial a quifer andin upper zo nes of the Floridan aquifer sys tem presently tapped by wells

. S altwater is p resent through out the count y in lower zo nes of the Fl oridan aquifer system no t presently tapped. Ma ny of the fring e areas, especially to the east, are populated and are characteri zed by heavy pump ing of gro und wa t er and the accompanying drawdown of water le vels.


### 2The extent of brackish water has appa rently i ncreased in rec ent year s in both aqui fers. The re is a needto determine the ex tent, mec hanism, a nd rate of movement of brackish wa ter in th e aquifers of Volusia County. F urthermore, there is aneed to u nderstand how fu rther movement can be minimize d.

Purpo ses and Scope
The study of bra ckish—water occurre nce in V olusia County is one of many wate r—resources investigation s that have been con ducted bythe U.S. Ge ological Surv ey in coo peration with Volusia County

. The pur poses of this study, which was cond ucted during 198 0—82, were to:
1. Evalu ate gro und—water use, w ater—level trends, and t he water budget for both aquif ers;
2. Deter mine the occurrenc e of brackish water i nthe upper part of th e Floridan aquif er system and i nthe surficial aquifer;
3. Diffe rentiate bet ween areas of natural ly occurringbrackish ground wate r and areas of recent intr usion;
4. Diffe rentiate bet ween areas of lateral and vert ical brackis h water i ntrusion and i nvestigate the cause and exten t of the intrus ion; and
5. Descr ibe the e ffects of alternative water—manageme nt actions that couldmin­ imize future saltwat er intrusion.
This report is the full documentation o f all results of the stu dy. The infor­ mati on here includes the follow ing: an assessment of ground—water wit hdrawals from both aquifers, a det ailed des cription of water— level tre nds for the Floridan aqui fer system, esti mates of the wat er budgets of th e surficial laye r and the Flor idan aquife r system, maps s howing chlo ride concen tration inboth aquifers thro ughout th e study area, an ass essment o f eviden ce of saltwater intrusion in surf icial—aquifer wells and in nonpublic supply wells open t o the Floridan aqui­ fer system, a se parate as sessment of eviden ce of intrusion in pu blic—supply wells open to the Floridan aquifer system, and description s of possible counter measures agai nst future intru sion. The study enc ompassed the entire county, altho ugh emphasis was on data col­ lect ion in the eastern and western fringes wh ere brackishwater is present i nthe uppe r Florida n aquifer system and in the surficial aquifer. Most data co llection for this st udy was done duri ng 1981—82, although numerous analyses in this report invo lve pre—198 1 data. For the purpose of determi ning change s in wa ter levels and wate r qualitydue to dev elopment, recent data were compare d to data c ollected main ly during 1953—5 6.
Detai led analysis is limited generally to the surfi cial aquifer and the upper Flor idan aquifer sys tem. Detailed a nalyses of the lower zones of the

4Flor idan are not possible because of the scarcity of dat a. For the purposes of area l calcula tions, th e study area does no t include the areas o f Lake George, Lake Monr oe, and Lake Har ney.

Previ ous Work
The general ground

—w ater hyd rology o f Volusi a Countywas described by Wyrick (196 0, 1961). Hi s investigati on is most valuable to this repor t because i t pro­ vide s the historical water

— leve l and water

— quali ty data base which is needed to dete rmine lon g — term ch anges cau sed by development . Knochenmus and Beard (1971) asse ssed th e quali ty and quantit y of the surface

—wat er and ground- water r esources of Volusia County; the section on groun d water in that report provides ad ditional wate r — quality datafor many wells that had been p reviously sampled by Wyr ick. A map report by Knochenmus (1968) discussed drainage feasibility throughout the coun ty. Bush (1978) presented a gr ound

—water flow mo del of Volusia County. Simo­ nds and others (1 980) demonstra ted relations between water

— level trends in the surf icial aquifer and vegetative classifica tions in cen tral Volusia County. Rut- ledg e (1982) eval uated the eff ects of irrig ation withdraw als on the Floridan aqui fer system in no rthwest VolusiaCounty.

Water

— resources datacollected in th e county includ e several daily or peri­ odic records of stream di scharge, stream s tage, andwater levels in wel ls. Many of thes e records span more than 20 years. Long

— term records of water

— quality and disc harge hav e been maintained for two spr ings in Volusia County and l ong — term reco rds of stage have been maintainedfor two lakes. Al l of these record s exceed 15 y ears in length.

Data C ollection

Data collection for this study incl uded water

— level measurements i nwells, wate r sampling fr om wells, andoperation of water

— level recorders to monitor vari ation of water level with time

. Specifi c — capacity tests were made to provide a better understanding of the hydr ologic pr operties of the Floridan aquifer sys­ tem.
Much of the data coll ection effort involved the inve ntory update of many well s that were inventoried by Wyr ick (1960 , 1961). Addition al wells were inven­ tori ed where needed. All major publ ic

— supply (muni cipal) wells we re inventoried.

Well

—Numbering Syste m
Wells inv entoried by the U.S. Geological Surve y ar e ref erenced by local well numb ers based on lati tude and longit ude coordinates derived from a g rid of 1 — minu te pa rallels of latitude and longitud e. Numbers consist of the last digit of the degree and the two di gits of the minute of the l ine of latitud e on the south side of the quadrang le, the last di git of the degr ee and the two

5digi ts of the minu te of the line of longitude on the east s ide of the qua drangle, and t he two

—digit sequence number ass igned in the orde r in which the wel l within the quadrangl e was inventoried. For example, well 90 5

— 116

— 02 was the second well inve ntoried in the 1

—minute qu adrangle north of lat 29 ° 05 ’ and west of long 81 ° 16 ’
. Table 1 gives inf ormation about the wells referenced by local wel l number in this report. Addition al data for a wel l may be retrieve d from the comput er files of the U.S. Geol ogical Su rvey. Thi s data is r etrieved by the 15

—digit station num­ bers shown in the table

. As of the date of this publicat ion, more than 1,000 wells have been inventorie d by the U.S. G eological Surve y in Volusia Co unty.

ENVIRONME NTAL SETTING
Cl imate

The climate in Volusia County i s subtropica l; the average temperature is 71 ° F and t he average rainf all is 53 inches p er year. The col dest months are D ecember, Janu ary, an d Febr uary, when te mperatures average around 60 ° F; the warmest are June , July, and August which average around 80 ° F. More t han hal f of the yearly rain fall occurs duri ng the humid summer months of June

— September.
Long

— term yearlyrainfall records are shown in figur e 2. Ra infall has been slig htly hig her tha n averag e at the De La nd site in recent years, and slightly belo w average at the Cres cent Cit y site. Long

— term rainfall is noticeably lower near the coast than it is inland.

Geo graphy

From a bro ad perspective, the top ography in Volusia Coun ty is of two types: Kars t topogra phy and leveled terraces. Karst topography is the name applied to the undulatin g, pittedland surface that oc curs wher e sinkho les are numerous and drai nage is pr imarily downward. This type of topography i s common in the are as in Volu sia C ounty where land surface is highest

—— the Crescent City Ridge and the De Land Ridge (fig. 1). The remainin g areas are characterized as leveled t erraces. Surf ace drainage is more typical of these leveled terraces.

Terra ce formation during the P leistocene pla yed an import ant part in shaping the land surface in Vol usia Coun ty (Cook e, 1945; Wyrick, 1960). Terraces are expa nses of la nd of rel atively unif orm altitude which wer e the sea floor whe n the sea level s tood higher than present sealevel. Terrace f ormation ac counts for the flat ness of muchof Volusia County. The Crescent Cit y Ridge and the De LandRidge are remnants of the Penholoway Terrace, which has been e roded large ly by sinkhole acti vity. The other three terraces in Vo lusia Cou nty (fig. 1) are re latively unch anged and are th erefore relativ ely level.

6Table 1.-- Data on well referenced in this report which have been inventoried STATION AQUIFER ALT DEPTH NO. LOCAL NO. AND WELL NAME PENETRATED LAND WELL 284736080515101 84705106 COUNTY LINE WELL NR MAYTOWN,FL FLRD 6 200 284821081075501 84810701 LEMON BLF FSM CMP WELL,S.OF OSTEEN, FL FLRD 10 138 284857081081201 84810801 LEMON BLUFF WATER ASSOC., S. OF OSTEEN FLRD

-- 202 285105080515801 85105101 PUTNAM GROVES WELL, SW OF OAK HILL FLRD 6 90 285341080532401 85305302 BROWN & COPELAND WELL, NR ARIEL FLRD 8 225 285403080514390 35405103 INDIAN MARS. ESTATES OF EDGEWATER FLRD 10 150 285512081202801 85512001 USGS WELL 1.9MI S.OF BLUE SPG NROR.CTY FLRD 9.52 200 285636081175501 85611702 ORAN.CITV P.S. WELL #3, ORANGE CITY FLRD 23 257 285745081054001 85710501 USGS OBSER WELL AT ALAMANA, FL. FLRD 35.9 121 285716081053901 85710502 USGS TEST WELL 12, N.OF LK.ASHBY FLRD 35 241 285953083574701 85905709 NSB PS WELL. NUMB 4 IN 1980, N.SMYRNA FLRD 22.12 190 290107081062001 90110602 USGS TEST WELL. E 1, W.SAMSULA FLRD 41 111 290129081072901 90110701 USGS TEST WELL 8, W.SAMSULA FLRD 40 241 290138081203202 90112002 USGS J—2 TEST WELL, W.OF DELAND FLRD 42 500 290251081001401 90210001 USGS TEST WELL I,NE OF SAMSULA FLRD 26 700 290324080580501 90305801 MENDRICKS WELL TURNBULL BAY ROAD, NSB FLRD 7 104 290447081102301 90411004 I-4 DEEP WELL, E OF DELAND FLRD 39.9 241 290541081132902 90511304 USGS 04 DP TEST W.NR DELAND, FL.6"CSG FLRD 38.35 639 290606083581901 90605803 S. SIDE OF ROSE BAY, ALLANDALE FLRD 5 125 290651080582802 90605814 HARBOUR OAKS SUP.WELL,ALLANDALE FLRD 3.72 150 290646081213701 90612101 16S29E W.WARDS WELL,W DELEON SPRINGS FLRD 57 325 290612081214101 90612107 MAGSTROM DSL WELL, N. GLENWOOD FLRD 46

-- 290704081155301 90711502 16S30E11 HAGSTROMS 10"MARSH RD WELL FLRD 54 600 290804081215601 90712101 12” FLOW N OF DELEON SPRINGS FLRD 5 210 290752081220901 90712102 8”FLOW WELL W.OF DELEON SPRINGS FLRD 5 96 290816080574101 90805701 DON MEMBRY WELL IN WILBUR-BY-THE-SEA FLRD 12 130 290920081063001 90910601 USGS OBSER NR DAYTONA BEACH, FL. FLRD 27.04 235 290959031231601 90912301 DAIRY FLOW WELL #1,SW OF BARBERVILLE FLRD 12 241 291025081050201 91010501 USGS OBSER NR I—95 AT DAYTONA BCH., FL FLRD 26.05 498 291032081065201 91010601 DAYTONA P.S. WELL #49, SW OF DAYTONA FLRD 28 210 291004081101401 91011001 TIGER BAY TEST WELL 1A, W OF DAYTONA FLRD 41 220 291007081101613 91011013 TIGER BAY TEST WELL 350 SM NR DAYTONA SURF 41.17 20 291036081175801 91011701 HENDRIX WELL CN SR11, E OF BARBERVILLE FLRD 43.93 180 291107080591601 91105902 BLUE WATERS MCTEL. WELL, DAYTONA BCH FLRD 25 133 291133081035801 91110302 DAYTONA P.S. WELL #37, DAYTONA FLRD 28 205 291133081040601 91110404 G.E. PLANT 6-INCH W. AT DAYTON BEACH,F FLRD 27.55 235 291124081043401 91110410 DAYTONA P.S. WELL #41, DAYTONA FLRD 28 290 291105031052301 91110504 DAYTONA P.S. WELL #46, DAYTONA FLRD 33 210 291155081022901 91210237 DAYTONA P .S. WELL #32, TUSC., DAYTONA FLRD

-- 160 291353081160401 91311601 UNION CAMP SHALLOW WELL NR BARBERVILLE SURF 34.13 20 291429081024702 91410213 HOLLY HILL P.S. WELL #7A, HOLLY HILL FLRD 9.2 200 291425081024501 91410214 HOLLY HILL P.S. WELL #8, HOLLY HILL FLRD 9 215 291436081024701 91410216 HOLLY HILL P.S. WELL #9, HOLLY HILL. FLRD 8.02 216 291435081025501 91410218 HOLLY HILL P.S. WELL. #ll, HOLLY HILL FLRD 8

-- 291646081034501 91610306 ORMOND P.S. WELL #6, ORMOND BEACH FLRD 8 200 291715081281801 91712801 J.C. MEW WELL AT SEVILLE, FL. FLRD 14.9 180 291835081324201 91813201 USED 426 PINE ISLAND, W.OF SEVILLE FLRD 4.36 155 291904081055501 91910504 TOMOKA ESTATES 2” WELL NW OF ORMOND FLRD 8.59 140 7Land surface altitude ranges from 0 to 120 fe et in Volusia County. The top ographic high s are in the Cresce nt Ci ty R idge and t he D e Lan d Rid ge. Lowest areas are along the coast a nd in the St. Johns Rive r valley (fig. 3) . Generally , land surface alti tude rise s in a stepl ike progr ession f rom the Silver Bluff Terrace to the Pam­ lico Terrace to the Talbot Terrace to the ridges i nwestern Volus ia County.

Ge ology

Four stratig raphic u nits are discus sed in the following paragraphs and are illu strated i nfigure 4. Descriptions of t he forma tions are from Wyrick (1960) and figure 4 was d erived from ge ologic logs of the Florida B ureau of Geolo gy (for­ merl y FloridaGeologic al Survey ). Well numbers on t hese figu res are assigned by the Florida Bureau of Geology. The Olds mar Lime stone of early Eocene age, alth ough illu strated, is not discussed because no kn own wate r wells penetrate it in t he study area.
The sedim ents of Pleistocene and Holocen e ag e con sist of fine— to medium— grai ned qua rtz san d, sandy clay s, and locally , small amoun ts of shell. In some area s, t he s and has been cemented into “hardpan ” by dep osition of iron oxide at the water table. The Plei stocene a nd Holoc ene depos its are generally 20 to 50 feet thic k, but locally t hey can be as much as 100 feet thick. The Miocene and Pliocene deposits consist of unconsolidat ed beds of fine sand , shells, and calc areous sil ty clays. The ove rall thickn ess of the Miocen e or Plio cene deposits inVolusia Countyis generally 2 0 to 70 feet.
The Ocala Limeston e, of late E ocene age, is composed of cream to whit e lime- ston e mottled with gray zones. T he Ocala Limestone is generally only slightly dolo mitized i nVolusiaCounty. Because of e xtensive erosion t he format ion is thin in m ost of Volusia C ounty, and abse nt in much of t he De Land Ridg e.
The Avon Park Limes tone of late mi ddle Eocene age , varies in co lor from chal ky white to light brown or ashen gray, and consists of laye rs o f da rk—brown dolo mite sepa rated by layers of ch alky lime stone. Th e dolomit e is crystalline and cont ains few fossils, but the lim estone is very fossiliferou s. The limestone is exte nsively d olomitized. Some o f the Avon Park Formation was removed by erosion befo re the overlyingOcala Limeston e was deposited

.
Hydrogeology

The a quifers discuss ed are the surf icial aquifer a nd the Floridanaquifer syst em. The surficial aquifer is c omposed o f poorly consolid ated sand , clay, and shel l bed s of Plei stocene and Holocene ages. The Flori dan a quifer system is made up o f the limeston e and dolomite of Eocene age . Although the shell beds of Miocene and Pliocene age s may yieldsome water , these bed s are exclu ded from di scussion beca use few wells inVolusia Countyare open to th em. Of

9grea ter i mportance from a hydraulic standpoint are the clay layers of Miocene or Plio cene age which for m the confining b ed that retards w ater moveme nt betweenthe surf icial aquifer an d the Floridan aquifer system. The surficial aquifer is the layer of sand a nd shell from lan d surface down to the firs t areally persistent and rel atively impermeable l ayer of clay, or down to the limesto ne if no clay bed thus descr ibed is p resent. Altho ugh the s urficial aqui fer may co ntain local zones of clay and hardpan, t he clay zo nes are i nconsis­ tent enough and the hardpanis permeab le enough t hat these d o not signi ficantly reta rd the flow of water inthe aquifer . The surfic ial aquifer is generally 10 to 50 feet thick. It is thickest in the De L and Ridge area, where it reach es 100 feet in s ome places.
The sur ficial aquifer is uncon fined because it contain s the top of the zone of saturation, the w ater table , which is free to r ise and fall inthe aquifer. Typi cal seaso nal water —table f luctuations range from 4 to 5 feet. The average dept h to the water table in most of Volusia Co unty is less than 10 feet, although in the De Land Ridg e area depths typic ally exceed20 fee t. In ot her ridge areas (fig . 1), the average depth to t he wate r table is typically 5 to 1 5 feet, but in nonr idge areas the average d epth to the w ater table is only 0 to 5 feet. Simonds and others (1980 ) showed re lations betwe en depth to the water table and vegeta­ tive classification.

Water enters the surfici al aquifer by direc t infiltrat ion of r ainfall, rech arge caus ed by applicationto the lan d surface of Floridan aquifer system withdrawals, streamfiow, and le akage in areas of upw ard grad ient from the Flori­ dan aquifer system

. It leaves as evapotransp iration, streamflow, and leakage in area s of downward gradient to the Floridan aquifer system. Lateral movement into or out of the study area in the surfi cial aquifer is small be cause hydrauli c gra­ dien ts are small andthe ability of the aquifer to transmit water is slight.

Water l evels in wells open to the Flor idan aquifer system in Vol usia County are above the top of the aquife r. In areas o f artesian flo w (fig. 5) th e water leve l in wells is above lan d surface. I nother part s of VolusiaCounty, the water leve l in Florida n aquifer sy stem wells i s generally 10 to 40 fe et below lan d sur­ face . Because the Floridan aquifer system i s artesia n, it is completely s aturated from bottom to t op. Altho ugh water levels cannot rise and fall within the aquifer, theycanris e an d fa ll i nwe lls that penetrate the aquifer. Thi s fl uctuation is indi cative o f press ure chan ges wit hin the aquifer . Typic al seaso nal wat er—level fluc tuations are 4 feet in u ndeveloped areas and 5 to 10 feet in areas of pumping. The surfa ce d efined by water levels in wells tapping the Florid an aquifer system is called t he potentio metric sur face of the Flori dan aquifer system. The slop e of this surface denotes the direction of later al ground—water f low withi n the aqui­ fer. Furtherm ore, the differen ce in altitude between the w ater tab le and the pote ntiometric surface determin es the direc tion o f leak age b etween the a quifers. If the water table is higher thanthe pote ntiometric s urface, thenthe leaka ge is from the su rfical aqui fer down to the Floridan aquifer s ystem. Conv ersely, if the pote ntiometric sur face is hig her than th e water tab le, then th e leakage i s from the Floridan aquifer system up to t he surficial aquifer.

12Water ente rs the Flori dan aquifer system in Vo lusia County by downward leakage from the surficial aquifer through the con fining la yer and by horizontal inflow from outside Volusia County. It l eaves as upward leakage through the c onfining laye r, spring discha rge, well disch arge, and horiz ontal outflow t o other areas. Figur e 6 shows the altitude of the top of the Fl oridan aquifer system. The top of the freshwater zone is located at this surface an d the th ickness of this zone is zero to 1,400 feet depend ing on lo cation. The freshwater zone is thinnest in coastal areas and near th e St. J ohns River and th ickest in central Volusia Coun ty. Belowthis freshwater zone are lime stone anddolomite formatio ns that are satu rated with saltw ater.

GROUND-WATER USE
Estimates of ground—water use are given in table 2. Withd rawal rates have appr oximately tripled during 1955—80 for all uses except irrigat ion. Ir rigation use h as increased mor e than tenfold, probably becaus e of the increas ed use of wate r for irrigati ng the leathe r leaf fern, which is grown commercially on the Cres cent CityRidge and t he De Land Ridge. Th e largest withdraw als are for public— supp ly use; ir rigation wat er use ra nks second. In 1980, all other water uses com­ bine d made up less than th e public supply or the irrigation use. Total ground— wate r use has quadrupled between 19 55 and 1980.

Table 2.--Estimated ground—water us e in Volusia Co unty [In mil lion gallons pe r day]

1955 19 67 1980 Publi c Supply 10 15 .8 30.2 Agric ultural irrigat ion 1.7 6 .1 23.7
Domes tic, self-suppl ied 1.8 2 .0 4.5
Heat pump and lawn i rrigation 2.0 3 .4 6.2 Other 0.5 0

. 6 1.2 Totals 16.0 27 .9 65.8

1 /Sou rce 19 55 - Knochenmus and Beard, 197 1, and Florida Bureau of Geology project files
19 67 - Files of U .S. Geological Survey 198 0 - Project files of U.S. Geologi cal S urvey and S t. Johns River Wa ter Management District
14More than 95 percent of th e ground water withdra wn in Volusia County is pumpe d from the Floridan aquifer system, and t he remain der is taken from the surfici al aqu ifer. T he fol lowing discussion deals with the various categ ories of water use for bo th aquif ers and shows how withdrawals for each category are di stributed in th e study area.
The VOLDATA file, which is mentioned in thi s se ction, is a data file maint ained by the Vol usia CountyBuilding Inspection Department and inclu des d ata o n all well s per mitted by that department since 1976. It is usefu l as a so urce of informati on perta ining to water use. Additional data conti nue to be addedto VOLDATA.

Surfici al Aquifer In Volusia County, the total pre sent (19 80) pumpa ge from the surfi­ cial aquifer is approxima tely 3 Mg al/d. There are veryfew agri cultural irrig ation we lls and no public—supply wells that are ope n to the s urficial aquif er. Most of the agricultural ir rigation wells tappin g th e s urficial aquif er are locate d in the Cr escent City R idge area andare used fo r irri­ gatin g ferner ies. The total pumpage from these w ells is probablymuch less than 1 Mgal/d.
Water from the surficia l aquifer is used m ostly for lawn irr igation. Figur e 7 show s the dis tribution of surficial aquife r ir rigation wells in the VOLDATA f ile. In January 1983 , there were 1,952 surficial aquifer irrig ation wells in the VOLDATA fil e out of a tota l of 7,257 for all well types , or 27 percent. An e stimate of the pumpage in Volusia County from the surficial aquifer for lawn irrigation purposes is ab out 2 Mgal/d. This is based on these ass umptions: (1) there are approxim ately 5,000 lawns irrig ated wit h water from the surficial aquifer, (2) th e averag e lawn is 8,000 ft

, (3) the a verage applica tion rate is 30 in/yr. As figure 7 shows, most surf icial aquifer irrigation well s are in coast al ar eas. Although the surfi cial aquifer is an important s ource for lawn irriga tion, its contributio n to total agri cultural irriga tion is small. The second largest use of water from the surf icial aqu ifer is for domes tic purposes. The VOLDATA file contain ed d ata f or 39 0 su rficial aqui­ fer dom estic wells of a total of 2,6 00 domestic wells on Jan uary 1983. An estimate of the domestic pumpage from t he surfic ial aqui fer may be obtined by multip lying the ratio 390/2600 by the total domestic gro und—water use in tab le 2; the pumpage f rom the surficial aquifer for domes tic use is thus 0.7 Mgal/d. Figure 8 shows that m ost of these wells are located in the N ew Smyrna Beachand Edgewater areas.

Floridan A quifer System
All but a small f raction of th e groun d wate r used in Volusia County is from the Flor idan aquifer system. All public—s upply wells and most agri­ cultu ral irrigation wells are open to the Floridanaquifer system

.

16Figures 9 and 10 show the distributions of public—supply wells in1955 and 1980. Also shown are the pum ping rates for each supplier. Daytona Beach is the largest supplier. Public suppliers sho wn in figure 10 that are not shown in figure 9 we re not in existence in 1955. Figure 11 shows that the greatest conce ntration of agricultural irrigation wells is in northwest Volusia County, where most of the fern industry is located. The map shows the distribution, as documented in the VOLDATA file, of Floridan aquifer system we lls used for ir rigation which are greater than 4 inches in d iameter. The 1980 withdrawal rate for ag ricultural irrigation was 23.7 Mgal/d

. Figure 12 i s a plot of Floridan aquifer system we lls documented in the VOLDATA system th at are used for irrigation and which are 4 inche s or l ess in diameter. A few of the wells in this group may be used for agricultural irriga­ tion, but mo st are used for lawn irrigation. The greate st concentrations are in the areas o f Ormond Beach, Daytona Beach, and Port Orange. Figure 13 is a map showing the distribution of Flori dan aquifer wells doc­ umented in the VOLDATA fil e that are used for domestic purposes. The greatest numbers of these wells are in the De Land Ridge.

WATER-LEVEL TRENDS In Volusia County, the practices that cause lowering of water levels are pumping or drainage or a combination of the two. Drainage most directly causes water—level declines in the surficial aquifer, but may also induce declines in the F loridan aquifer system because the surficial aquifer acts as a reservoir for recharg e to the Floridan aquifer system. The lo wering of water levels caused by development may be estimated by comparing recent water levels with water levels measured during a time of less development. Water—level declines due to development are difficult to ascertain because they often are masked by water—level fluctuations caused by variations in ra infall.
Surficial Aquifer

Water levels in the surficial aquifer have not been monitor ed extensively in Volusia County. Nonethe less, it is pos sible to define areas of greatest water—level decline in the surficial aquifer base d on amounts of drainage and pumpage. Figures 7 and 8 show that most of the wells open to the surficial aquifer a re located in coastal areas where about 3 Mgal/d are pumped for lawn irrigation. The other developmental s tress on the surficial aqu ifer is artifi­ cial drainage. Figure 14 shows that the are as of greatest arti ficial drainage are the Dayt ona Beach area, the Port Orange area, and the Lake Ashby area. The largest declines in the surf icial aquifer due to development are, therefore, in the coas tal areas and in the Lake Ashby area.
Figure 15 sh ows two water—level records for surfici al—aquifer wells unaf­ fected by d evelopment, beginning in 1978. The hydro graphs show typical 

### 19fluctuation s due to rainfall variations. The troughs in the records during the summer of 19 81 were caused by a drought that caused re cord low water levels at many sites in Volusia County.
Floridan Aquifer System

Water levels in the Floridan aquifer system measured during the mid—l950’s can be compared to levels measured recently to determine water—level declines due to pumping and drainag e. To accomplish this, the w ater levels obtained at three different times——November 1955, May 1981, and September 1982, are com­ pared. Changes in the pote ntiometric su rface are caused by the net effects of rainfall var iations and ground—water development. Figu re 16 shows that rainfall totals fo r the 6 months ending Nov ember 1955 and September 1982 were 28.5 and 32.5 inches, respectively. Any significant difference s between the respective potentiomet ric s urface maps are, therefore, caused mainly by development. The rainfall trend upto May 1981, on the other hand, is different from the other two. Although the periods up to November 1955 and Septe mber 1982 represent average rainfall, the period up to May 1981 represents unusually deficient rainfall. The differences between the November 1955 and the May 1981 potentio­ metric surface maps are, therefore, cau sed by both rainfall trends and develop­ ment.
Figures 17, 18, and 19 s how the poten tiometric surface of the upper part of the Flori dan aquifer system for November 1955, Septe mber 1982, and May 1981. Also shown in figure 18 is th e area in which the potentiometric surface decline from November 1955 to September 1982 exceeds 10 feet. This is a 70—square—mile area which includes much o f Ormond Beach, Daytona Beach, and Port Orange. All of this decline may be attributed to pumping. Figure 19 shows a potentiometric surface which has been affected by development and drought. Most of the water— level measurements made in Volusia County for the May 1981 potentiometric sur­ face map were the lowest ever measured. In the Ormond Beach, Daytona Beach, and Port Orange area, the potentiometric surface was below sea level in an area exceeding 100 square miles; in November 1955, potentiometric surface levels there range d from 3 to 20 feet above sea level.
Figure 20 sh ows long—term water—level hydrographs f or five Floridan aqui­ fer system wells. Sig nificant downwar d trends are apparent for well 911—104—04, located within 300 fee t o f a pub lic—supply well in Daytona Beach, and for well 909—106—01, southwest of Daytona Beac h. The downward trends are caused predom­ inantly by increased pumping, and the seasonal fluctuation s are caused by vari­ ations in rainfall and pumpage . The seasonal fluctuations at the other three wells are caused by variations in rainfall rates. The lowest water levels gen­ erally occu rred in the summer of 1981 because of dr ought conditions.

Further detail of seasonal fluctuations is shown in figure 21. Largest fluctuation s occur in areas of pumping. Well 859—057—09 is within apublic—sup­ ply well field and 912—102—37 is in a populated area of Daytona Beac h. Well 857—105—01, in south—central Volusia County, is farthest from ar eas of pumping.
27WATER BUDGET Surficial Lay er The surficial layer consis ts of the land surface, the l akes, streams, ditches, the surficial aquifer, and the vegetation. Generally, the surficial layer includes everything between th e atmosphere and the conf ining layer. An assessment of the water budget of this layer aids the determinati on of the water budge t of the Floridan aquifer system.

The water bu dget of the surficial layer may be expr essed generally as: R + LI + SI + RW = ET + LO + SO (1) where

R = rainfal l; LI = leakage inflow through a confining layer; SI = stream inflow; RW = return water from pumping of Floridan aquifer system; ET = evapotr anspiration; LO = leakage outflow; and SO = stream outflow. Rainfall and Evapotranspiratio n The average annual rainfall in Volusia County for the period 1951—80 was approximate ly 5 3 i nches based on an average of five stations in and near Volu­ sia C ounty. The locations of five rain gage s, and their corres ponding 30—year average annual rainfall, are shown in figure 22. Rainfall comprises more than 95 percent of the inflow (recharge) to the surficia l layer in Volusia County. Evapotranspi ration is the return of water from the land surface to the atmosphere. The avera ge ev apotranspiration for Volusia County is estimated at 39 inches per year based on v alues used by other investigators in central Flor­ ida. Lichtle r and others (1968, p. 145) estimated that in Orange County, evapo­ transpirati on is 70 percent of rai nfall. Knochenmus and Beard (1971, p. 45) estimated an evapotranspiration rate of 35 inches per year in Volusia County based on a rainfall rate of 52 inches per year. Grubb and Rutledge (1979, p. 21) calculat ed an average evapotranspiration of 40 inc hes per year in the Green Swamp, an area about 40 mile s southwest of Volusia County. The evapotranspira­ tion rate is somewhat vari able from place to place dep ending on the rainfall, the depth t o the water table, and other factors suc h as vegetation type.

Streamflow

Streamflow is the second largest outflow fro m the surficial layer. Volusia County can b e subdivided into three major surface drain age areas (fig. 22). One drains nor t h to Middle Ha wand Little H aw Creeks, o ne drains

34west into the S t. Johns River, and the othe r drains seaward. Waters in the fi rst two areas are se parate in VolusiaCounty, but eventu ally con- verge north of Volus ia County near Palatka.
The locatio ns of six continuo us str eam—gaging stations are shown in figur e 22 along with the l ong—term streamf low rate, in inches per year, for the ar ea upstream from each gage . These long—term streamflow rates are pur ported to represent the av erage flow during the 31—year period 1952— 82. A 31—year reco rd exists for Litt le Raw Creek near Se ville and for Sp ruce Creek near S amsula. The recor ds from these two s ites were used as in dices for estimating the lo ng—term average disc harges for the other s tations. For example, th e 7 —year average discha rge at Middle Raw Creekfor 1976—82 w as multiplied bythe ratio of the 31—year av erage of Littl e Raw Creek over the 7—year average of Little Raw Creek for 1976—82 to obtain the 31—year average of Midd le Raw Creek. Th e mean of the long— term a verage discharge e stimated using Li ttle Haw Creek as an i ndex, and the lo ng—term discharg e estimated using S pruce Creek as an in dex, is the streamflow rate shown i nfigure 22. Table 3 shows measured ave rage dis­ charg es for the six streams and show s long—ter m estimate s of d ischarge for e ach.
The streamflow from abasin is influe nced by the type of to pography and surface hydrologic conditions in the basin. For example, a basin whichincludes more are as of artesian flo w than ridges will have more streamflow than a basin t hat includes more r idges than areas of artesian flow. The topography—hydrology types and the character istic st reamflow rate for each may be as follows: Estimated Topog raphy—hydrologytype s treamflow rate (in/yr ) Areas of artesian fl ow 18 Nonri dge areas witho ut artesian flo w 1 1 Ridge areas with sur face drainage 6 Ridge areas in close d basins 0
Streamflow is mostly o utflow from the s urficial la yer in Volusia Count y because all significant surface—drainag e systems in Volusia Count y have their he adwaters w ithin the county. There i s, however , a sligh t e astward Stream inflow fro m F lagler County into northe ast Volusia Count y and a westward str eam inflow from Bre vard County into so uth Volu­ sia Co unty (fig. 22). Th e total area from wh ich these streamfl ows orig­ inate is about 60 square miles, whereas t he entire 1,200—squ are—mile area o f Volusia County is contributing to st ream outflow. If st ream dis­ charg e pe r uni t ar ea is abo ut th e same fo r th e thr ee c ounties, then stream inflow is onl y about 5 perce nt of stream ou tflow.

Vertic al Leakage
Altho ugh values for ver tical leakage bet ween the surficia l aquifer and the Floridan aquifer system ma y be small, th ey are importan t in the under standing of the wa ter budget of the t wo aquifers. Leaka ge is out- flow from the surfic ial

36layer in mo st of V olusia Coun ty, but also is inflow t o the s urficial layer in areas of ar tesian flow fro m the Floridan aquifer system. The net leakage t o the Floridan aquifer system may be estimated as rain

— fall, minus evapo transpiration andstreamflow. If it i s assumed that ra infall and evapotran spiration are 53 and 39 inc hes per year, respe ctively, a nd that the aver age stream flow for the si x basins shown in figure 22 is 12 inches per year, then the estimated leakage to the Flori dan aquifer system in th ese bas ins is 2 inches per year. Leakage is estimated as a small residual th at results after accou nting for the other elements of the water budget. R ainfall andstreamfio w are measured but have e rror built in. Evapotranspirat ion is only est imated andis subje ct to g reater erro r. Therefor e, the errors in these co mponents place a high degree of uncertainty in the leakage estimate.
Water Budget of the Surficial Layer
Table 4 gives est imates o f the water budget of the surficial layer for four topograp hy

—hydrology types. Ridge areas in closed basins have rainf all a nd ev apotranspiratio n rate s tha t are slig htly d ifferent from the others. Reported ra infall is slightly higher bec ause most ridge areas in closed basins are l ocated near t he De Land rain gage wh ich has an average rainfall of 54 inches per year. Evapotranspir ation is lower becau se the depthto the wate r table is a s much as 5 0 feet. Upwar d leak- age from the Floridan aquifer is zero with the exception of one topogra­ phy

—hydrology type. St reainflow rates va ry as estimated pre viously. Streamflow and downwar d leakage suppleme nt each other in tha t an area of high streamflow will h ave low downwardleakage, and an a rea of low streamflow will have high downwar d l eakage. Additional co mponents of the water budget are str eam inflow, discussedearlier, and r echarge to the surfi cial laye r caused by F loridan a quifer sy stem withd rawals, e stimated as the tot al withdrawal from the Flor idan aquifer system for ir rigation and h eat pump supply , from table 2.
The components of inflow a nd outflow for the en tire Volusia County surfi cial l ayer a re esti mated as the areall y—weighted averages of each inflo w and outflo w comp onent in tabl e 4. The annual water budget is thus 53 inc hes rainfall, 1 inc h upward leakage fr om the Floridan aqu ifer sys­ tem, 0.5 i nch recharg e from Floridan aquifer sys tem withdr awals, and 0.5 inch stream inflow, counterba lanced w ith 39 inches evapotransp iration, 11 inc hes stream outflo w, and 5 inches downward leakage to the Floridan aquif er system. As discussed earl ier, these water

—budg et values are sub­ ject to considerable error.

Floridan A quifer System
The purpose of this se ction is to assemble a wa ter budg et of the Flori dan aquifer system in Volusia County. If tranami ssivity and poten­ tiome tric surface of th e Floridan aquifer system are known, s ome of the recha rge (inflow) rates previously esti mated may be t ested. Spring dis­ charg e rates are als o used to
38test t hese recharge estimates. Then, these tested rech arge and discharge rates are placed into abudget of the Floridanaquifer system along with estimates of horizont al inflow and outflow rat es derived from the transmissivity esti mates. The equatio n for the water budget of the Floridan aquifer system is a
modified ve rsion of equation 1: LI +H I = LO +HO +P + FW +SPG (2)
where
RI = horizontal grou nd—water inflow ; HO = horizontal grou nd—water outflo w;

P = pumpage; FW = flowing well di scharge; SPG = spring dischar ge;
and other t erms are as previously defined.

Specific Capa cities The sp ecific capacity of a well is related to transmissivity of the pe netrated aquifer. The specific capac ity is the ratio of pumping rate from a well to the drawdown in the well. Because transmissivity is a cha racteristic of the entire aquifer thickness, and because most wells penetrate only a fraction of that thicknes s, it is necessary to adjust data to esti­ mate the specific cap acity of fully

—pene trating wells. This may be don e by dividing the spe­ cific capacity of eachwell by the lengthof well that is open to the aquifer, then mult iplying t his ratio by the aqui fer thick ness to estimate the specific capacity that would have be en obtained ha d the well pe netrated the e ntire thickness of the aqui fer. It i s as sumed that the aquifer contribute s wa ter t o th e we ll un iformly from top to bottom.
Ratio s of specific capacities t o lengths of open hole are shown in fig ure 23. All wells shown are at least 6 inches in diameter and all but one are used for public supply or irrigation. Although these values vary, it is possib le to discern general areal trends. Five physio graphic areas and the average ratio fro m figure 23 are as follows: Average r atio of specifi c capacity Area to l ength of open h ole, in gallons p er minute per f oot per foot
Cresc ent City Ridge De La nd Ridge Talbo t Terrace and R ima

Ridg e Pamli co Terrace and

Atla ntic Coastal Ri dge Coast al areas 0.3 1.9 0.5
15
1.3

40

### --- ---

--- ---

---

-- - - -- ---

---

-- ---

---

---

---

-- ---

---

---

---

-- ---

---

--- If it is assumed tha t the Floridan aquifer system is an isot ropic, homogeneous, and nonl eaky aquif er, then the specific capacity of wells fully penetrating the aquifer is r elated to transm issivity by the following:



### Q

- ≈ ( 4 π T )

- t s w 2.30 log 2.25 T r w 2 s (fro m Lohman, 1979, p. 52) (3)
wher e
T = transmissivity (feet squared p er day); S = storage coeffic ient (dimension less);

Q = discharg e rate from pumping well (cubi c feet per day) ; t = time aft er discharge st arted (days); s w= drawdownat production well, (feet); a nd r w= radius o f production we ll, (feet).
The e quation shows th at specific capa city, Q/s wis nea rly proportional to T at a give n value of t, but gr adually di minishes as t increases by the amount l /log 10 t. The value of trans missivity calculate d fo r a given test is sens itive to specific capa city but relatively inse nsitive to values of t, r w, and S. Som e e rror is built into this ana lysis because leakage is not consider ed a nd be cause some of the assump­ tion s about the aquifer ’ s prope rties may not be accurate. If it is ass umed th at t = 0.03 day, that r w= 1 f oot, that S = 0.00 05, and that the aquifer thicknes s is that of the upper permeable zone of the Floridan aquifer system as defined by Miller (198 1), which is 300 feet in Volusia Cou nty, then the relation bet ween the ratio deri ved above and tr ansmissivity is as follows:
Avera ge ratio of spe cific capacity to le ngth of open ho le, in gallons Transm issivity, per m inute per foot per foot in ft 2 /d 0.5 35,000 1.0 74,000 1.5 114,000

Test ing Estimates o f Flow in the F loridan Aquifer System Agai nst Recharge Es timates
The flow wi thin an aquifer ma y be c ompared to the net recharge (leakage) esti­ mate d for areas upgradient t o determine if estima tes of recharge rates a re realis­ tic. Figure 24 shows fo ur areas for which these c omparisons are ma de. The flow rates from areas 2, 3, and 4 are measure d discharges from sprin gs, and tha t of area 1 is dete rmined from hydr aulic gradient and transmissiv ity.
If the hea d gradient across the outf low bounda ry of a recharg e area is known and the transmissiv ity at that bound ary is also known, then the average recharge rate for th e area may be calculat ed. Considering ar ea 1 as an area bounded bya ground— wate r divide on the west and by an outflow line onthe
42east , the outflow line may be subdivided into segment s A through J for the purpose of calcul ating outflow. The flow through each segm ent may b e ca lculated from the expr ession: Q= T I L (4)
wher e Q = rate of f low perpe ndicular t o a potentiometric contour, in cu bic feet per day; T = transmissivity of the aquifer in feet squaredper day; I = hydraulic gradient ap proximated a s the chan ge in headbetween t he two conto urs, in feet, divi ded by the distance between the two con tours, in feet; and L = w idth of the segment midway bet ween contours, in feet.
Becau se this outflow l ine is on the Rima Ridg e and the Talbot Terrace, where the aver age ratio of specific capacity to leng th o f o pen hole is 0.5 gallons per minu te per foot per foo t, the average tr ansmissivity is e stimated as 35,0 00 ft 2 /d

. Tota l fl ow t hrough segments A through J is thus 31.4 ft 3 /s

. Bec ause the area upgra­ dien t is 99 mi , this rate cor responds to an aver age net recharge in flow to the Flor idan aquifer sys tem of 4.3 in/y r. Area 1 consi sts of 6 per cent areas of artesian flow, 92 percen t no nridge areas with out artes ian flow, and 2 per cent ridg e areas having surface drainage. The weig hted—average net re charge ca lculated using tab le 4 is 3.6 in/yr, which compares reas onably with the 4.3 in/yr calcu lated from flowin the Florida n aquifer syste m. Area 2, which is the d rainage ar ea of Ponce d e Leon Springs, consists of 38 per- cent area s of arte sian flow, 19 percent nonridge areas with out artesian flow, 21 perc ent ridge ar eas with su rface drainag e, and 22 percent ridg e areas in closed basi ns. Using the estima tes in table 4, the w eighted—average net recharg e is 5.3 in/ yr. For a 76— square—mile area, total flow is 30 ft 3 /s. This is equal to the measured long—term average di scharge of Ponc e de Leon Sprin gs. The drainage area of Blue Spring s is divided i nto areas 3 an d 4 so that t he flow whic h origina tes in Volusia County may b e separa tes from that which originates pre- domi nantly in Lake Count y. Area 3 is 138 mi consi sting of 1 percent are as of arte­ sian f low, 29 percent nonrid ge areas without arte sian flow, 12 percent r idge areas havi ng surfac e draina ge, and 58 percent ridge ar eas in closed basins. The w eighted— aver age recharge, 12.8 in/yr , is equivalent to flow of 130 ft 3 /s. Most of the 59 mi in area 4 are in Lake County, but 7 mi areridge area s in clo sed basins in Volusia Coun ty. This latter area yields 9.4 ft 3 /s of recharge whereas the rem aining area yiel ds only 4.7 ft 3 /s be cause mos t of it is an area of artesian flow in the St. Johns Rive r b asin. The net recharge cal culated for areas 3 and 4 is thus 14 4 f t 3 /s , which comp ares reaso nably to the long—term average discharge of Blue Springs, 161 ft 3 /s. It i s assumed in thi s analysis that all recharge i s discharged bythe local

44spring. It is possible that some of this rech arged wat er is moving downward to more distant points of discharge , or th at water recharged outside of the study area is enterin g this ground

—wate r basin.

Water Budget of the Floridan Aquifer System
Table 5 gi ves the estimated flow budget of t he Floridan aquifer system in Volusia County. Leakage figures were deriv ed from the rates givenin table 4 which h ave been substantiated by analyses of flow in the Floridan aquifer s ystem. The figure for spring discharge is the sum of discharges from Blue Spr ings, Ponce de Leon Springs, and 8 ft 3 / 

### s for two small springs near Lake Monroe. Th e discharge from flowing wells is an estimate. Pumpage is equal to the 19 80 water

—use rate. The horizontal flow into and o ut of Flagler County and the horizontal flow i nto the Atlantic Ocean were calculat ed from the equation 

### Q = T I L. Finally, the horizontal inflow and outflow at “ other boundaries ” was estimated. These boundaries are the east shore of Lake Georg e an d L ake Harney, the north shore of Lake Monroe, and the Lake County, Sem inole County, and Brevard County bounda ries. These flow rates through “ other

Table 5.--Estimate d water budget of the Floridan aquifer system in Volusia County

Inflow Downward le akage Horizontal inflow: From Fla gler County From oth er boundaries Total

Outflow Upward leak age Spring disc harge Flowing

—wel l discharge Pumpage Horizontal outflow: To Atla ntic Ocean To Flag ler County

To other bou ndaries Total Cubic feet Inches per second per year 460 5.2

20 0.23 50 0.57 530 6.0
Cubic fee t Inches per second per year 100 1.1 190 2.1

20 0.23 100 1.1

30 0.34 10 0.11 80 1.0 530 6.0



### 45boun daries ” we re calcula ted as residuals to the other components. The e stimated annu al water budget of the Flo ridan aquifer syste m in Volusia County thu s consists of 5 inches d ownward leakage inflow, 1 inch upward leakage outflow, 1 inch horizon­ tal inflow, 1.5 inches ho rizontal outflow, 2.5 inche s dischar ge from springs and flow ing wells, and 1 inch pumpage . These water

—budget figures are subject to consid­ erab le er ror. The largest component of this budget , le akage, was derived as a resid­ ual in the bu dget of the surficial aquif er, and that budget was const ructed from othe r estimates.

CONCE PTS OF BRACKISHWATER OCCURREN CE AND MOVEMENT
Basel ine Salinity
Chlor ide concentrat ion is used in this report as the inde x of salinity because chlo ride ions make up the larges t component of the total sa linity of seawa ter and beca use chloride analysis i s a re latively simple labo ratory determinati on. Most nat­ ural ly occurr ing wate rs have chloride in some am ount. For this report, water having a chloride concentrati on less than 50 mill igrams pe r liter (mg/L) is co nsidered fres hwater. If the concentra tion is about 19,000 mg/L, the water ha s a salt concen­ trat ion c lose to that of t he oc ean, and is c onsidered saltwater

. Wa ters having chlo­ ride concentrations intermediate be tween these ext remes may be co nsidered bracki sh. Freshground water in Volusia County co ntains some of the salts present inthe ocea n. This mixture probably exists because salt

— laden aerosols from the ocean pre­ cipi tate on land. Ground w ater also contains constitu ents diss olved fro m the rocks and the soil.
Value s of chloride concentrat ion in water from individual sites not exhibiting intr usion may vary bec ause of seasonal effects. Fi gure 25 shows var iations inthe chlo ride conc entration in water from freshwater wells. Most f resh grou nd water in Volu sia County has a chlorid e concentration exc eeding 10 mg/L and vary ing within a rang e of 10 mg/ L. Figur e 26 shows variations in ch loride c oncentrations in brackish wate r wel ls. The r ecords shown, with the exception of the recor d for 911

— 059

— 02, exhi bit changes caused by se asonal fluctuatio ns, as opposed to chang es caused by a tren d. Many rec ords vary i nsuch a way that t he maximum is more th an twice a s much as t he minimum.

C hloride Concent ration Change R atio
The terms “ brack ish water m ovement ” or “ intrusion ” used herein, refer to a sig­ nifi cant increase in chlori de concentration, wi th time, at given monitor ing sites. Intr usion may be assessed by compar ing chlor ide conce ntrations in water from wells duri ng 1951

— 57 with data collected from the same v eils during 197 7

— 82 as follows :

46

### -- ---

-- ---

---

---

-- -- ---

---

-- ---

---

---

---

-- -- ( F C n – C t ) chloride con centration = 

### - (5) change ratio 

### C n + C t

- 2 where

C n= chloride concentration now (1977-82), in millig rams per liter; C t = chloride concentration then (1951

— 57), in milli grams per liter; an d F(C n -C t ) = C n -C t -lO, if C n— C t is greater than +10 = C n -C t +lO, i f C n -C t is less than

— 10 = zero, if C n— C t falls in the

— 10 to +10 range

This ratio is more meaningful than a simple ratio of concentration change over average concentratio n because the latter ratio would be the same for a change of 10 to 20 mg/L as it would for a change o f 1,000 to 2,000 mg/L, which is much more significant.
If the chlor ide concentration change ratio exceeds + 0.5 or falls below

— 0.5, the n the change is probably l arger than that which can be attributed to seasonal variations. Changes thus de scribed may be evidence o f intrusion or freshening.

Physical Natu re Freshwater-Saltwater Interface
In coastal aquifers within Volusia County, the freshwater is boun ded by saltwater lat erally and vertically. The theoretical alt itude of the freshwater — saltwater interface may be calculated using the Ghyben

—Herzberg pri nciple as modified by Hubbert (1940). This p rinciple states that when freshwater in a coastal aquifer is inequilibrium with the und erlying saltwater , the altitude of the interface between them is

— 40 times the headof the fres hwater system immediately above the interface. Because the freshwater head immediately above the interface differs from the head that is measured in wells that tap the upper parts of the aquifer, and because the saltwater system is us ually not static, estimat es o f t he a ltitude of the interface are subject to error. It is reasonable to assume, though, that the p osition of the interface becomes lower as the measu red water level in the upper part of th e aquifer increases. Figure 27a shows that the transition from freshwater to saltwater is a zone of mixing which contains brackish water. This transition zon e is formed because of mi xing caused by water

— level fluctuations anddispersion. Generally, the thicknes s of this zone becomes greater as the vertic al component of ground— water flow increases. Figure 27b shows, conceptually, the movement of the tran­ sition zone caused by pumping.

49WATER BUDGET


### BRACKISH WATER IN THE SURFICIAL AQUIFER Present Distribu tion

Most ot the surficial aqu ifer in Vo lusia County contains fr eshwater. Fig ure 28 sho ws that th e bar­ rier island is generally the only area where ch loride c oncentrations exceed 250 mg/L. Brackish water
occur s in coasta l area s and, to a lesser extent, in the St. Johns River valley area. The areal distri­ butio n of chl oride concentrations sho wn i n th e fi gure was obtained from samplings of app roximately 70 wells . Most wells sam pled are in coast al areas.

In freshwater zones of the surf icial aquifer, th e water is considerably less mineralized than water in the freshwate r zones of the Florida n aquifer sy stem. Most of the fres hwater in t he surficial aquifer is a cal cium bicar bonate—type water, a lthough so dium and chloride are lo cally prev alent. Fig ure 29 shows
avera ge i onic compositions for eight surfic ial—aquifer wells in the central Volu sia C ounty area, where the diss olved solids concentra tion of water from the surficia l aquifer is approximatel y one—third of that from the upper part of the Flor idan aquifer system in the same ar ea. The bra ckish water in the surfi cial aquifer is a sod ium chloride— type water that is les s mineralizedthan the brackish wa ter in the Florid an aqu ifer s ystem at th e same locat ion. Sodium chloride and calcium bicarbonate conce ntrations are l ess in the surfi cial aquifer thanin the Floridanaquifer system.
Compariso n of Past and Pr esent

Chlor ide—concentratio n change ratios for 10 surficial aquifer wells are shown in figu re 28. Depths of these wells are 12 to 4 5 feet. Fourratios are above +0.5, one is belo w —0.5, and five are be tween — 0.5 and +0.5. The four that exceed +0.5 are on the barrier island north of Ormond Beach and indicate that intrusion i s apparently occurring th ere. The me aning of th e one value below —0.5 is somewhat dubi­
ous because the wel l had a measure d depth of onl y 14 feet in 1981 v ersus the 40 f eet report ed depth. The five wells for which th e chloride concen tration change rat io was insignific ant (between —0.5 and +0.5)
are a ll located in ar eas where the sur ficial aquifer h as freshwater.

It is apparent that intru sion is oc curring in the surficia l aquifer on the bar rier island. Unfor­ tunat ely, no sur ficial aquifer veils sampled during 1951—57 are currently avai lable for re sampling south of Ormond Beach on the bar rier island. This is bec ause the fe w that were sampled thenwere destro yed or
cover ed before this s tudy.

BRACKISHWATER IN THE FL ORIDAN AQUIFER S Y S TEM

Present Di stribution
Figur e 30 shows the distri bution of brackish w ater in the upper part of the Floridan aqui fer system deriv ed from sam pling approximately 250 w ells during 1977—82. Dept hs of these wells are 50 to 400 feet. The F loridan

51WATER BUDGET

Average ion concentration s of water from F loridan a quifer s ystem wel ls in three different parts of the Volusia County ground—water s ystem are shown in figure 3 2, and the lo cations of the wells used a re in figur e 33. The three water types shown are the brackish water in the St. Johns River ar ea, the brackish water of the coastal area s, and the freshwater in between . All three have a calcium bicarb onate “back- ground” caused by dissolutionof the l imestone that makes up the aquifer. This disso lution causes fresh-

water in the Floridan aquif er system to be more miner alized than fr eshwater in th e surficial aquifer. Super imposed upon this calcium bicarbona te background is amixture of the sa lts found in seawa ter. This

mixture is very dilute i n the freshwaterin central Volu sia, (calcium bic arbonate—type wa ter) and is stronge r for the two bra ckish—water area s (sodium chlori de—type water). T he ratio of calc ium ions to bicarbonate ion s is about 1 for fresh gr ound water but is noticeably higher for br ackish water i n the Flori dan. The rea son for thi s may be t hat cation e xchange is taking place. The sodium and magnesium ions in the brack ish water s are switching places w ith calcium ions in the limestone , thus creating a highe r calcium to bicarbonate rati o in the water.

The ratio of sodium to chloride ions in freshwate r in central Volusia, 1 .00, is equal to that of table salt and that of bra ckish areas is nearly th at of seawa ter, 0.85. T he ratio of sodium to chloride in brackish Flor idan aquifer system wate r is actual ly slightly smaller thanthat of seawater beca use of the c ation exchange p reviously mention ed.

The sulfate concentra tion in coastal brackish ground water is d isproportionatel y low compared to the concentration in the St . Johns Riv er basin bra ckish ground water and seawater. The ratio of sulfate to chloride ions i s 0.042 for t he formertype and 0.1 0 for the lat ter two water types. Th e reason for these di fferences is unclear; a poss ibility is that sulfate red uction is occurring prefe rentially in coast al ground water.

Comparison of P ast and Present

Chlor ide concentration s in the past wer e compared with r ecent concentrat ions to determine brackish watertrends inthe Florid an aquifer system. This analysis is separated into two p arts

—— one forwells that have not been used for public supply and another for wells that have been used. The latter category inclu des abandoned public

— sup ply wells. Public

— supply we lls are discussed separately bec ause results foundfor public—supp ly wells were mar kedly different from results fou nd for other well s.

Nonpublic—Suppl y Wells
Range s of chlo ride

— concentratio n change ratios for 154 veils are shown in figure 34. Most wells sampl ed are in areas where the Florid an aquifer system contai ns brackish water. If change ratios indi­ catin g a sig nificant change are those above or equal to +0. 5 and be low or equal to

— 0.5, then 10 wells showe d a significant increase and 11 showed a significa nt decline

. Neither group exhibited distinct areal trends. A few g eneralizations ma y be made, howev er: five

56wells showing a significant increase are in the coastal area from Daytona Beach to north of O rmond Beach; t hree wells sho wing significant increases are in the Ponce de Leon Springs area; and five wells showing asignificant decline are in the inland areas from Oak Hill to New Smyrna Beach. All of these groups, how- ever, are intermixed with wells that did not exhibit signif icant changes. Wells for wh ich chloride —concentration change ratios were within t he — 0.5 t o +0.5 range li kewise did not show areal patt erns. The significant increases in chloride concentration in the water from five wells in the coastal area of Ormond Beach and Daytona Beach may be associated with ground

—water withdrawals in northeast Volusia County. Figures 10 and 12 indicate that many wells exist there and figure 18 shows larg e drawdown in the area.
The mos t marked increase in c hloride concentration in anonpublic

— supply well is in well 911

— 05 9

— 02 on the barrier island in Dayt ona Beach. This well showed a gradual increase from 110 mg/L in 1956 to 580 mg/L in 1979, followed by a jump to 1,400 mg/L in 1 981 (fig. 26). Well 9 1 1

— 059

— 02 is one of the five wells in northea st Volusia County which exhibited significant changes (fig. 34).
Twenty

— two irri gation wells were resampled in January 1983, as part of an intrusion monitoring network that was suggested by Rutledge, (1982). Table 6 gives chloride concentrations in the wells resampled. Of the 22 wells, only one showed a marked change. Well 907

— 122

— 01 yielded wa ter with a chloride concen­ tration of 280 mg/L in 1980 and 500 mg/L in 1983. It is noteworthy that this well is in the area of Ponce de Leon Springs, near the three wells previously mentioned that exhibited chloride

— concentration change ratios g reater than +0.5 (fig. 34). Generally, there is little evidence th at intrusion is occurring uniformly over large areas in the Floridan aquifer system in Volusia County. This means that if intrusion is taking place, it is local upcon ing of brackish water. Such a m ovement would tend to be noticeable from samplings of wells that are deeper, are pumped a greater amount of the time, and are pumped at higher rates.

Public

— Supply Wells For the purpose of evaluating chloride

— concentration change ratios for public

— supp ly wells, samplings during three periods of 1982 are compared to previous samplings. Figures 35, 36, and 37 show the ratios thus determined dur­ ing March

—April, August, and December 1 982, respectively. Of the 14 wells sam­ pled du ring March

—April 1982, 9 exhibited chloride concentrationchange ratios that equaled or exceeded +0.5. The remaining 5 ratios are in the range o f

— 0.5 to +0.5. Of the 23 wells sampled in August 1982 (fig. 36), 8 yielded ratios that equale d or exceeded +0.5, and the remainder fe ll in the range of



### — 0.5to +0.5. Of the 27 wells sampled in December 1982 (fig. 37), 5 yielded ratios that equaled or exceeded +0.5 and 4 yielded ratios below or equal to



### — 0.5. Increases inchloride concentration occur primarily during the dry



### 60Table 6.-- Chloride concentration in water from wells in the monitoring network suggested on the northwest Volusia County report. DATE OF CHLORIDE SAMPLING (YR- TIME OF CONCENTRATION STATION NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING (MG/L) 290532081213501 90512101 290532081213501 90512101 290532081213501 90512101 290532081213501 90512101 290532081213501 90512101 290538081213501 90512102 290538081213501 90512102 290538081213501 90512102 290538081213501 90312102 290538081213501 90512102 290538081213501 90512102 290538081213501 90512102 290538081213501 90512102 290538081213501 90512102 290512081213801 90512111 290512081213801 90512111 290512081213801 90312111 290635081202101 90612005 290635081202101 90612005 290646081213701 90612101 290646081213701 90612101 290646081213701 90612101 290646081213701 90612101 290646081213701 90612101 290646081213701 90612101 290646081213701 90612101 290642081214001 90612102 290642081214001 90612102 290642081214001 90612102 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290612081214101 90612107 290613081213001 90612108 290613081213001 90612108 290613081213001 90612108 290613081213001 9 0 612108 290613081213001 90612108 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 290804081215601 90712101 C.F. GREENS #1 WELL, GLENW000 C.F. GREENS #1 WELL, GLENW000 C.F. GREENS #1 WELL, GLENW000 C.F. GREENS #1 WELL, GLENW000 C.F. GREENS #1 WELL, GLENW000 C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D C.F. GREENS DEEP WELL, GLENW00D BOOKERS IRR. WELL, GLENWOOD BOOKERS IRR. WELL, GLENWOOD BOOKERS IRR. WELL, GLENWOOD C. RICHARDS0N'S #24 WELL, DELEON SPGS C. RICHARDS0N'S #24 WELL, DELEON SPGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS 16S29E W.WARDS WELL,W DELEON SPRINGS LAWRENCE WELL, DELEON SPRINGS LAWRENCE WELL, DELEON SPRINGS LAWRENCE WELL, DELEON SPRINGS HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D HAGSTROM DSL WELL, N. GLENW00D LUCAS IRRIG WELL, S OF DELEON SPGS LUCAS IRRIG WELL, S OF DELEON SPGS LUCAS IRRIG WELL, S OF DELEON SPGS LUCAS IRRIG WELL, S OF DELEON SPGS LUCAS IRRIG WELL, S OF DELEON SPGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 12” FLOW W OF DELEON SPRINGS 61 79—02—10 816 142 79—11—30 600 110 80--02--05 550 130 80—03—03 635 65 83—01—18 505 120 78—12—14 1600 500 79—01—23 —— 665 79—02—10 535 655 79—02—10 818 650 79—12--27 630 360 80—01—02 555 800 80—02—05 600 670 80—03—03 640 620 83—01—18 500 360 80—01—02 820 64 80—03—03 655 58 83—01—18 515 46 79--12--27 700 31 83--01--18 615 30 78—12—18 1000 930 79—01—23 —— 790 79—02—10 608 920 79—02—10 758 880 79—12—01 700 790 80—02—05 635 700 80—03—03 610 640 79—12—27 610 430 80—03—03 620 400 83—01—18 550 380 78—12—18 915 450 79—01—23 —— 490 79—02--10 603 478 79—02—10 804 480 79—12—01 645 470 79—12—27 615 400 80—01—02 540 500 80—03—03 625 440 83—01—18 525 450 78—12—18 1015 710 79—02—10 556 798 79—02—10 808 792 80—02--05 630 710 83—01—18 535 660 57—04—29 —— 390 66—01—20 —— 670 79—06—15 1400 438 79—09—10 1340 678 79—12—10 1500 810 80—02—05 700 780 81—12—15 1310 510 82—04—14 1020 720 83—06—02 900 830 84--05—03 905 810---- Table 6.-- Chloride concentrations in water from wells in the monitoring network suggested om the northwest Volusia County report--Continued DATE OF CHLORIDE SAMPLING TIME OF CONCENTRATION STATION NO. LOCAL NO. AND WELL NAME (YR—MO—D) SAMPLING (MG/L) 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290752081220901 90712102 290737081220301 90712201 290737081220301 90712201 290815081194801 90811902 290815081194801 90811902 290815081194801 90811902 290849081202601 90812004 290849081202601 90812004 290849081202601 90812004 290849081202601 90812004 290849081202601 90812004 290910081202801 90912003 290910081202801 90912003 290910081202801 90912003 290917081222201 90912203 290917081222201 90912203 290917081222201 90912203 290917081222201 90912203
290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301 290959081231601 90912301
290959081283501 90912801
291017081235001 91012006 291017081235001 91012006 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS 8"FLOW WELL W.OF DELEON SPRINGS HAGSTROM IRRIG WELL, W OF DELEON SPGS HAGSTROM IRRIG WELL, W OF DELEON SPGS FG INTERNAT #1 WELL, DELEON SPGS FG INTERNAT #1 WELL, DELEON SPGS FG INTERNAT #1 WELL, DELEON SPGS HCBLICK #4 WELL, E OF DELEON SPGS HCBLICK #4 WELL, E OF DELEON SPGS HCBLICK #4 WELL, E OF DELEON SPGS HCBLICK #4 WELL, E OF DELEON SPGS HCBLICK #4 WELL, E OF DELEON SPGS CRIBB'S IRRIG WELL, N OF DELEON SPGS CRIBB'S IRRIG WELL, N OF DELEON SPGS CRIBB'S IRRIG WELL, N OF DELEON SPGS DAWSON BRN FLOW WELL SE OF BARBERVILLE DAWSON BRN FLOW WELL SE OF BARBERVILLE DAWSON BRN FLOW WELL SE OF BARBERVILLE DAWSON BRN FLOW WELL SE OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE DAIRY FLOW WELL #1, SW OF BARBERVILLE
B.F. TURNER WELL, SR4O, NR EMPORIA
BLACKWELDER N WELL, DELEON SPGS BLACKWELDER N WELL, DELEON SPGS 62 57—04—30 —— 7200 79—09—10 1350 4275 79—12—10 1515 4800 80—02—05 0650 4700 81—12—15 1340 3800 82—04--14 1030 4000 83—06—02 0900 4500 84—05—03 0850 4200 80—05—13 1030 280 83—01—18 0600 500 80—01—02 0640 8.7 80—03—03 0750 11 83—01—18 0625 9.8 79—06—21 1600 266 79—12—05 1530 230 79—12—05 1630 230 80—03—03 0855 260 83—01—18 0640 274 79—12—27 0730 10 80—03—03 0915 10 83—01—18 0655 9.1 56—04—23 —— 14 66—01—20 11 79—12—05 1600 11 82—04—14 1000 11
53—11—06 —— 326 66—09—13 —— 478 67—01—03 1530 422 67—02—27 0930 445 67—05—01 1145 400 67—07—10 1215 425 67—09—11 1025 425 67—11—01 1145 430 68—01—04 1000 435 68—03—08 1110 430 68—05—03 1030 370 68—10—25 0850 445 69—05—06 1110 450 70—09—26 —— 455 70—11—04 —— 455 72—05—10 1900 300 72—09—06 1115 450 79—12—10 1430 470 80—01—23 1100 470 81—12—16 1400 450 82—04—14 0930 440 83—08—04 1715 450 83—08—04 1715 450
79—02—10 0730 15
79—02—01 0725 14 83—01—18 0700 11Table 6.-- Chloride concentrations in water from wells in the monitoring network suggested in the northwest Volusia County report--Continued DATE OF CHLORIDE SAMPLING (YR- TIME OF CONCENTRATION STATION NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING (MG/L) 291112081282601 91112802 291112081282601 91112802 291111081291401 91112915 291111081291401 91112915 291216081215601 91212101 291208081292501 91212906 291426081224001 91412205 291422081254701 91412505 291422081254701 91412505 291422081254701 91412505 291435081255301 91412509 291452081261701 91412610 291452081261701 9141261C 291454081291101 91412903 291522081265201 91512611 291522081265201 91512611 291525081260601 91512619 291525081260601 91512619 291507081290601 91512903 291507081290601 91512903 291507081290601 91512903 291508081302801 91513001 291508081302801 91513001 291508081302801 91513001 291508081302801 91513001 291621081304901 91613002 291724381275701 91712703 291724381275701 91712703 291715081281801 91712801 291715081281801 91712801 291838081280601 91812803 291838081280601 91812803 291838081280601 91812803 291838081280601 91812803 291834081281101 91812804 291834081281101 91812804 291834081281101 91812804 291834081281101 91812804 291910081312401 91913101 291910081312401 91913101 RICHARDSON’S #13 WELL, EMPORIA RICHARDSON’S #13 WELL, EMPORIA MCCOLLOUGH EMPOR. RD WELL, EMPOR. MCCOLLOUGH EMPOR. RD WELL, EMPOR. STRWMD TEST WELL, SR40, E OF BARBERVILE S.SMITPH HARP+PET. RD SW WELL, EMPORIA UNDERHILL 10” WELL, NR BARBERVILLE 14S28E36 TAYLOR’S MISERY WELL, PIERSON 14S28E36 TAYLOR’S MISERY WELL, PIERSON 14S28E36 TAYLOR’S MISERY WELL, PIERSON R.JONES 8” WELL,MISERY+WASH. RD,PIERSON R.JONES WELL N OF WASH. ST, PIERSON R.JONES WELL N OF WASH. ST, PIERSON T.TAYLCR CARLYLE WELL, W. PIERSON WORTHINGTON PINE ST WELL, NE PIERSON WORTHINGTON PINE ST WELL, NE PIERSON CARTER’S IRRIG WELL. NE PIERSON CARTER’S IRRIG WELL. NE PIERSON BRADDOCK WELL, W OF WASH RD, PIERSON BRADDOCK WELL, W OF WASH RD, PIERSON BRADDOCK WELL, W OF WASH RD, PIERSON SJRWMD WELL 2 MI W OF PIERSON SJRWMD WELL 2 MI W OF PIERSON SJRWMD WELL 2 MI W OF PIERSON SJRWMD WELL 2 MI W OF PIERSON 14S28E19 KELLY'S 2”WELL NW OF PIERSON M.SMITH L.B.C. RD 8” WELL, SEVILLE M.SMITH L.B.C. RD 8” WELL, SEVILLE J.C. MEW WELL AT SEVILLE, FL. J.C. MEW WELL AT SEVILLE, FL. W.COLMANS COWART RD WELL, SE SEVILLE W.COLMANS COWART RD WELL, SE SEVILLE W.COLMANS COWART RD WELL, SE SEVILLE W.COLMANS COWART RD WELL, SE SEVILLE M.COLMANS COWART RD WELL, SE SEVILLE M.COLMANS COWART RD WELL, SE SEVILLE M.COLMANS COWART RD WELL, SE SEVILLE M.COLMANS COWART RD WELL, SE SEVILLE 13S27E36 MILLICANS WELL W OF SEVILLE 13S27E36 MILLICANS WELL W OF SEVILLE 78—12—14 1115 11 79—02—10 0755 13 78--12—13 0940 11 83—01—18 0940 10 79—02—39 1310 22 79—02—10 0800 12 78—12—15 1310 10 78—12—08 1445 8 79—02—10 0705 13 83—01—l8 0715 8.8 73—12—14 1330 9 78—12—20 1315 8.4 83—01—18 0725 8.9 83—01—18 0825 9.6 79—02—10 0635 11 83—01—18 0800 8.2 80—01—02 0545 7.9 83—01—18 0745 7.2 78—01—l0 0955 8 79—02—10 0840 12 83—01—18 0815 7.5 78—12—20 1210 11 79—02—09 0950 14 79—09—27 1445 11 79—12—18 1530 11 79—12—18 1600 200 79—01—29 0800 13 83--01--18 0920 9.4 79—09—06 1915 10 80—01—08 1410 11 78—11—30 1115 12 79—01—29 0730 15 80—01—02 0740 11 83—01—l8 0850 13 78—01—11 0820 29 79—02—10 0555 29 80—01—02 0745 21 83--01--18 0900 31 78—12—20 1350 17 79—01—29 0845 16

63seas ons when water le vels are low and w ater withdrawals are high. Concen trations decr ease t emporarily during periods of higher water levels and reduced water use such as Dec ember 1982. Figures 3 8 and 39 show large fluct uations in the chlori de concen­ trat ion of water fro m public—supplywells.
The f act that the wate r from many publ ic—supply wells has undergone a n et wors­ enin g over the years is best ex emplified by the aban donment of producti on wells and by th e replacement of abandoned wells with new wells i nareas of freshe r ground wate r. Figures 40 and 41 show public—supply wells in use in t he mid-19 50’s and in 1982 , respectively, f or northeast Volu sia County. The we ll fields belong ing to the cityof Da ytona Beac h have changed d ramatically. In 1954 —57, the city wa s suppliedby thre e sets of wells——one on the bar rier island, one near the interse ction of U .S. 92 and S.R. 5A, and the thi rd nort h of the airport. In 1982, the fi rst two sets of wells had be en abandoned entire ly and three of the well s north of the airport h ad also been aban doned. A new well field n ear the intersecti on of Indian Lake Road an d U.S. 92 was put i nto operation in1982. Pumping s tress for the cit ies of Ormond Bea ch, Port Oran ge, and Holly Hill h as also shifted toward central Volusia County. A new well fiel d belon ging to the city of New S myrna B each wa s inst alled 7 miles inland of the old we ll field (figs. 9 and 1 0) in 1981. The newest wells belonging to t he Deltona Corp oration are northeast of t he older wells ( fig. 10), away from the brackish ground wate r in the St. Johns River area ( fig. 30).
The table of supplemental data at the back of this report shows chloride concen­ trat ions in public—s upply wells.

EFFEC TS OF MANAGEMENT ALTERNATIVES ON MOVEMENT OF BRACKISH WATER
Surfi cial Aquifer

The move ment of brackish water in the surf icial aquifer will probab ly continue on the barrier islan d. This intr usion is dif ficult to ma nage because of lack of control of withdr awals. Reduction of withdraw als during dry seasons may slow the rate of intr usion.
Most int rusion in the surficial aquifer is caus ed by pumping in areas close to brac kish water. Litt le intrusion is therefore like ly in mainland areas.

Flori dan Aquifer Sys tem
Possi ble wat er—management alternat ives inc lude mi nimizing well d epths, minimiz­ ing d rawdown, installi ng new wells where the freshwater zo ne is thickest, in creasing headin th e freshwat er zone using in jection we lls, and reducing head in the s altwater zone . The best appro ach may be a co mbination of th e above practic es.

67Mini mizing well depth may be t he single most effect ive step against intr usion. The idea is t o k eep as much distance as poss ible between the botto m o f the well and the unde rlying bra ckish wate r. Because the thickness of the freshwater zone i ncreases towa rd central Vo lusia (fig. 31), the max imum safe we ll depth als o increases i nthat dire ction.

Numer ous manag ement alte rnatives may reduce drawdown. One of the most p ractical poss ibilities is to inc rease the di stance between pumping wells to reduce mutual well inte rference. Cyclin g pumping among pr oduction wells so that no individu al well is pump ed for more than a limited time may reduce drawdown. If the number of supply well s per desired water

—use rate is maxi mized, d rawdown c ould be reduced. Two wells 1,00 0 feet apart each pumpi ng 300 gallons per minu te will create less dra wdown than one well p umping 600 gallons per min ute. Altho ugh the area of influence will actually be larger for the former situation, the “ point drawdown ” a t the well s would be less. It is th is point drawdown tha t influences the move ment of the transitio n zone below the well the most.
Altho ugh increasing the penetr ation of the aquifer tends to reduc e dr aw—down, it may de feat the purpose of avoi ding intrusion if wel l depths become exces sive. This conc ept is illustrated in f igure 42. Pumpage is equal for these two condi tions, but one well penetrat es 200 feet of the aquif er and the other penetrat es 400 feet. Assum­ ing that hydraulic p roperties of the aquifer a re uniform , the drawdown i nthe shallow well is app roximately twice the draw

—down in the deep we ll. However , the drawdown belo w the deeper wel l near the inter face is enough t o induce an upwa rd movement of the interf ace t hree t imes greater than the movement under the shallow well. If the inte rface is induced upward byapproxima tely one

—h alf the original distance between the interface and the bottom of the pump ed well, the condit ion is u nstable, andthe inte rface may sudden ly move to the bottom of the w ell (Bouwer, 19 78).
If all other things re main equal, the best locations for public

— supply well s are area s wher e the potenti ometric surface was highest during times of no p umping because thes e areas are cha racterized by maximum thickne ss of the fres hwater zone. F igure 31 show s that the maximum thick ness of the zone contai ning fresh or slightl y brackish wate r is located beneath the Talbot Terrace (fig. 1). G enerally, if a well is inst alled in this area, the re will be a thicker saf ety zone between the b ottom of the well a nd the transitionzone. Unfortunat ely, the transmiss ivity of the Flori dan aqui­ fer syste m un der t he Ta lbot Terrace may not be as high as i t is else where, so greater drawdown may occur t here. Injec tion wells may be used t o increase hydraul ic head in the freshwa ter zone and cont rol intrusi on. This would involve in jection of storm runoff o r tertiary

— treated sewa ge, and therefor e would require that steps be taken to avoid pollution.
Reduc ing hydraulic head i nthe saltwat er zone below produc tion we lls maybe an effe ctive way of contr olling intrusion , but is expensive relative to other methods. This method would involve installin g deep wells op en to

72salt water zones a nd sea led ti ghtly from f reshwater zones. These deeper wells would be pump ed contin uously t o reduce saltwate r head and the wate r would be discharged into natu ral saltwater bo dies at the sur face.

SUMMARY
Volus ia Count y is a 1,2 00

— square —mile area in e ast

— central Florida which incl udes the communit ies of Daytona Beach, Ormond Beach, New Smyr na Beach , De Land, and Deltona. The are a is oriented to ward touri sm, especi ally alongthe c oast. The two aqui fers underlying t he area are the unc onfined surficia l aquifer and the confined Flor idan a quifer system. The surficial aquifer consists of sand, clay, and shell beds of Ple istocene and Holocen e age, and the Floridan a quifer system consi sts of lime- ston e and dolom ite of Eoce ne ag e. The two aquif ers ar e sep arated by c onfining clay beds of Miocene or P liocene age.
Both aquifers contain goo d quality water in most of Volusia Cou nty, but brackish wate r is prese nt throughou t the eas tern and western frin ges of the county i nthe surf icial aquif er and in the upper zone s of t he Floridanaquifer system p resently tapp ed by wells. Salt water is present throughout the county in the re latively unta pped lowe r zones of the Flo ridan aqu ifer sys tem. Incr eased us e of water because of d evelopment in th e fringes has c aused intrusion

.
In 1980, the average ground

—water withdrawal in Volusi a County was 66 million gall ons per day. Gro und

—water use quadrup led betwee n 1955 and 1980 . More than 95 per- cent of the gro und water pumped is from the Floridanaquifer sys tem. All pub lic

— sup­ ply wells and most agricultural

— i rrigation wells are open to t his aquifer. T he total withdrawals for p ublic supply and a gricultural irrigatio n were 30 and 24 million gal­ lons per d ay, respec tively. Mos t of the 3 million ga llons per day pumpage from the surf icial aquifer is used for lawn irrigation.

Water levels i nFloridan aquifer sy stem wells declined mo re than 1 0 feet ov er an area of 70 square miles from November 1955 to Septemb er 19 82. T his dr awdown, which occu rred in the areas of Ormond Bea ch, Daytona Beach, and Port Orang e, was cau sed by pump ing. Considerablygreater declines were observed for May 1981 because o f drought cond itions.
The annual wat er budget of the s urficial lay er consists of 53 i nches rainfa ll, 1 inchupwar d leaka ge fro m the Florid an aqu ifer s ystem, 0.5 i nch re charge from Floridan aqui fer system withdrawa ls, and 0.5 in ch stream inflow, counterbala nced with39 inch es evapotranspira tion, 11 inches st ream outflow, and 5 inches downward l eakage to the Floridan aquifer system. The annual water budget of the Floridan aquifer system consists of 5 inches down- wardleakage inflow, 1 inch upward leak age outflow , 1 in ch horizont al inflow, 1.5 inch es hor izontal outflow, 2.5 inches discharge from springs and flowing wells, and 1 inchpumpage.

74Chlor ide concentratio n, which is used a s an index of sali nity, may vary at in dividual si tes not exhibiting trends b ecause of seasonal fluc­ tuati ons. Chlor ide concent rations inbrackish—w ater wells may f luctuate in su ch a way that t he maximum is m ore than twice the minimum.

Brack ish water movement, or int rusion, is apparentl y o ccurring in the s urficial aquifer on the barrier isl and in the northea st part of Volus ia County. It is li kely that intrusi on has also occurre d in other secti ons of the barrier island, al though this is difficul t t o a scertain becau se of the scarcity of lo ng—term chloride concentration data from these areas. The ba rrier island is generally the only part of t he study area where chlori de conc entrations in the s urficial aquifer exceed 250 milli grams per liter. Intrusion is likelyto c ontinue inthe s urficial aquif er on the barrier i sland. Little or n o intrusion is occ urring in the s urficial aquife r in inland are as.
There is little evidenc e that intru sion i s occu rring uniformly over large are as in the Flori dan a quifer system. Most nonpublic —supply wells have not exhib ited long—term changes in salinity

. Of 154 nonpub lic—sup­ ply wells sampled , 10 showed a significant incre ase an d 11 showed a sig­ nific ant decline in chlor ide concentr ation over time. Sig nificant incre ases in chloride c oncentration in wa ter from five such w ells in the coast al area of Ormond B each and Daytona B each may be associ ated with groun d—water withdra wals in northea st Volusia Coun ty.
There is upconing or verti cal intru sion at sites of publi c—supply pumpi ng. Publ ic—supply wells are usu ally dee per, are pumped a greater amoun t of t he time, and are pumped a t higher rates th an other wells. Intru sion manif ests itsel f as surges that are greatest d uring times of low rainfall and heavy water use. Many public—supply wells located close to brackish water zones in the fringes of Volusia County have been aban­ donedand replaced bynew wells in the cen tral part of the county, where the f reshwater zone is thickest.
Possi ble water—mana gement alterna tives to intr usion in the Floridan aquif er system include m inimizing well de pths, minimizing d rawdown, insta lling wells where the freshwater zone is thickes t, in creasing head in the freshwater zone u sing injection we lls, and reducing h ead in the saltw ater zone. Drawdo wn can be reduced by i ncreasing the number of sup- ply wel ls per desired water—use ra te. Minimizing well dep th is probably the s ingle most effe ctive step in c ontrolling intr usion.

75SELECT ED REFERENCES-- Continued

Bouw er, Herman, 1978 , Groundwater hydrology:New Yo rk, McGraw—Hill , 480 p.

Bush , P. W., 1978, Hydrologic evalu ation of part o f central Volus ia County, Flori da: U.S. Geological Surv ey Open—File Re port 78—89, 50 p.
Cook e, C. W., 1945, Geology of Flori da: Florid a Geologic al Survey Bulletin 29, 342 p.
Grubb, H. F., and Ru tledge, A. T., 1979, Long—term water supply p otential, Green Swamparea, Florida: U.S. Geologica l Survey Water—Resources Inves tigations 78— 99, 7 6 p.
Hubb ert, M. K., 194O , The theory of ground—water m otion: Journal of Geology, v. 48, p. 78 5—944.

Knoc henmus, D. D., 1 968, Surface dr ainage characte ristics in Volu sia County, Flori da: Flori da Bureau of Ge ology Map Serie s 30, 1 sheet.

Knoc heninus, D. D. , and Beard, M. E., 1971, E valuation of t he qua ntity a nd qual ity of water resources of Volusi a County, Florida: Fl orida Bureauof Geolo gy Report of Inves tigations 57, 5 9 p. Lich tler, W. F., An derson, Warren, and Joyner, B. F., 1968, Wate r resources of Orange Count y, Florida: Flo rida Bureau of Geology Report of Investigatio ns 50, 150 p.
Lohman, S. W., 1979, Ground—water hydraulics: U.S. Geological Sur vey Professiona l Paper 708, 70 p.
Lohman, S. W., and other s, 1972, Definitio n of selected groun d—water terms——r evisions and c onceptual refin ements: U.S. Ge ological SurveyWater—Supply P aper 1988, 21 p.
Mare lla, Richard, 19 82, Annual wate r use survey: 1 980: St. Johns River Water Man age­ ment District Techni cal Report no. 14, 166 p.
Mill er, 3. A., 1 981, Thicknes s of the upp er permeable zone of the tertiary lim estone aquif er system, sout heastern UnitedStates: U.S. G eological Surve y Water— Resou rces Investigat ions Open—File Report 81—1179, 1 sheet.

---- -, 1984 , Geohydrologic framework of the F loridan aquifer system in Fl orida a nd in parts of Georgia, So uth Carolina, a nd Alabama: U.S . Geological Su rvey Profes­ siona l Paper ---- (i n press).
Rutl edge, A
. T., 1982, Hydrology of the Floridan aquifer in northwest Volusia County, Flori da: U.S. Geolog ical Survey Ope n—File Report 8 2—108, 116 p.

76SELECT ED REGERENCES-- Continued
Schi ner, G. R., and Hayes, E. C., 1 982, Potentiome tric surface of the Floridan a qui­ fer in the St. Johns River Wate r Ma nagement District and vicini ty, F lorida, Sep­ tembe r 1982: U.S. Ge ological SurveyOpen—File Repo rt 83—30, 1 she et.
Simo nds, E. P., Jr., McPherson, B. F., and Bush, P

. W., 1980, Sha llow groundwate r condi tions and veget ation classific ation, central Volusia County, Flori da: U.S. Geological Surv ey Open—File Re port 80—752, 1 sheet.

U.S. Soil Conservati on Service, 198 0, Soil survey of Volusia Coun ty, Florida: 207 p

. Wyri ck, G. G., 1960, The ground—wat er resources of Volusia County , Florida: Flori da Geological S urvey Report of Investigations 22, 65 p. 1961, Record of wells in Volusia County, Florida: Florida Geolog ical S urvey Informa­ tion Circular 24, 96 p.

77TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS.

DATE OF CHLORIDE SAMPLING TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME (YR—MO—D) SAMPLING ON (MG/L) 291423081011901 91410101 OLD P.S. WELL, SEABREEZE #1, DAYTONA 54—03—02 —— 146 291423081011902 91410102 OLD P.S. WELL, SEABREEZE #2, DAYTONA 54—03—02 —— 130 291422081012101 91410103 OLD P.S. WELL, SEABREEZE #3, DAYTONA 54--03—02 —— 96 291423081012201 91410104 OLD P.S. WELL, SEABREEZE #4, DAYTONA 54—11—02 —— 116 291421081012301 91410105 OLD P.S. WELL, SEABREEZE #5, DAYTONA 54—03—02 —— 188 291421081012202 91410106 OLD P.S. WELL, SEABREEZE #6, DAYTONA 54—03—02 —— 630 291421081012202 91410107 OLD P.S. WELL, SEABREEZE #7, DAYTONA 54—03—02 —— 682 291421081012202 91410107 OLD P.S. WELL, SEABREEZE #7, DAYTONA 81—05—04 1250 130 291421081012202 91410107 OLD P.S. WELL, SEABREEZE #7, DAYTONA 81—07—14 1115 120 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—07—11 —— 1645 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—07—16 —— 1585 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—07—24 —— 355 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—37—27 —— 1160 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—07—29 —— 1085 291204081020501 91210201 DAYTONA P.S. WELL #1, ORANGE AV, DAYTONA 37—08—02

----- 890 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 39—00—00 —— 100 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 50—00—00 —— 96 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 54—02--25 —— 146 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 81—04—28 1225 160 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 81—04—28 1245 160 291158081015801 91210202 DAYTONA P.S. WELL #2, MALEY, DAYTONA 82—12—08 1415 150 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 39—00—00 —— 113 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 50—00—00 —— 134 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 54—02—28

—- 186 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 79—09—10 —— 1010 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 81—04—28 1022 750 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 81—04—28 1032 1000 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 81—04—28 1102 1000 291159081020201 91210203 DAYTONA P.S. WELL #3, MALEY, DAYTONA 82—12—08 1450 300 291202081020101 91210204 DAYTONA P.S. WELL #4, PALSY, DAYTONA 39—00—00 —— 117 291202081020101 91210204 DAYTONA P.S. WELL #4, PALSY, DAYTONA 50—00—00 —— 134 291202081020101 91210204 DAYTONA P.S. WELL #4, PALSY, DAYTONA 54—02—28 —— 182 291205061020301 91210205 DAYTONA P.S. WELL #5, ADAMS, DAYTONA 39—00—00 —— 119 291205061020301 91210205 DAYTONA P.S. WELL #5, ADAMS, DAYTONA 50—00—00 —— 134 291205061020301 91210205 DAYTONA P.S. WELL #5, ADAMS, DAYTONA 54—02—28 —— 160 291207081020301 91210206 DAYTONA P.S. WELL #6, ADAMS, DAYTONA 39—00—00 —— 102 291207081020301 91210206 DAYTONA P.S. WELL #6, ADAMS, DAYTONA 50—00—00 —— 122 291207081020301 91210206 DAYTONA P.S. WELL #6, ADAMS, DAYTONA 54—02—28 —— 146 291210081020501 91210207 DAYTONA P.S. WELL #7, ADAMS, DAYTONA 39—00—00 —— 99 291210081020501 91210207 DAYTONA P.S. WELL #7, ADAMS, DAYTONA 50—00—00 —— 127 291210081020501 91210207 DAYTONA P.S. WELL #7, ADAMS, DAYTONA 54—02—28 —— 132 291213081020701 91210208 DAYTON P.S. WELL #8, ADAMS, DAYTONA 39--00--00 —— 90 291213081020701 91210208 DAYTON P.S. WELL #8, ADAMS, DAYTONA 50—00—00

---- 86 291213081020701 91210208 DAYTON P.S. WELL #8, ADAMS, DAYTONA 54—02--28 —— 98 291215081020801 91210209 DAYTONA P.S. WELL #9, ADAMS. DAYTONA 39—00—00 —— 99 291215081020801 91210209 DAYTONA P.S. WELL #9, ADAMS. DAYTONA 50—00—00 —— 70 291215081020801 91210209 DAYTONA P.S. WELL #9, ADAMS. DAYTONA 54—02—28 —— 82 291207081020801 91210211 DAYTONA P.S. WELL #11, KEECH, DAYTONA 50—00--00 —— 198 291207081020801 91210211 DAYTONA P.S. WELL #11, KEECH, DAYTONA 54—02—25 —— 148 291210081021001 91210212 DAYTONA P.S. WELL #12, KEECH, DAYTONA 50—00—00 —— 78 291210081021001 91210212 DAYTONA P.S. WELL #12, KEECH, DAYTONA 54—02—25 —— 86 291212081021101 91210213 DAYTONA P.S. WELL #13, KEECH, DAYTONA 50—00—00 —— 62 291212081021101 91210213 DAYTONA P.S. WELL #13, KEECH, DAYTONA 54—02—25 —— 88 291210081021401 91210214 DAYTONA P.S.WELL #14, CAROLINE, DAYTONA 50—00—00 —— 60 291210081021401 91210214 DAYTONA P.S.WELL #14, CAROLINE, DAYTONA 56—02—25 —— 94 78TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS. CONTINUED DATE OF CHLORIDE SAMPLING (YR-- TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME MO—D) SAMPLING ON (MG/L) 291208081021301 91210215 291208081021301 91210215 291158081020901 91210216 291158081020901 91210216 291156081020701 91210217 291156081020701 91210217 291156081020301 91210218 291156081020301 91210218 291159081020401 91210219 291159081020401 91210219 291202081020501 91210220 291207081022101 91210221 291207081022101 91210221 291210081022301 91210222 291210081022301 91210222 291215081022501 91210223 291215081022501 91210223 291219081022801 91210224 291219081022801 91210224 291224081023001 91210225 291224081023001 91210225 291229081023201 91210226 291229081023201 91210226 291233081023501 91210227 291233081023501 91210227 291237081023701 91210228 291237081023701 91210228 291242081023901 91210229 291242081023901 91210229 291202081022301 91210235 291202081022301 91210235 291202081022301 91210235 291155081022901 91210237 291155081022901 91210237 291155081022901 91210237 291152081023701 91110203 291152081023701 91110203 291139081032401 91110305 291139081032401 91110305 291139081032401 91110305 291140081033601 91110306 291137081034801 91110303 291133081035801 91110302 291133081035801 91110302 291133081035801 91110302 291133081035801 91110302 291133081035801 91110302 291130011040601 91110407 291130011040601 91110407 291130011040601 91110407 291130011040601 91110407 DAYTONA P.S. WELL #15,CAROLINE,DAYTONA DAYTONA P.S. WELL #15,CAROLINE,DAYTONA DAYTONA P.S. WELL #16.CAROLINE,DAYTONA DAYTONA P.S. WELL #16.CAROLINE,DAYTONA DAYTONA P.S.WELL #17,CAROLNE,DAYTONA DAYTONA P.S.WELL #17,CAROLNE,DAYTONA DAYTONA P.S.WELL #18, KEECH,DAYTONA DAYTONA P.S.WELL #18, KEECH,DAYTONA DAYTONA P.S. WELL #19, KEECH, DAYTONA DAYTONA P.S. WELL #19, KEECH, DAYTONA DAYTONA P.S. WELL #20, KEECH, DAYTONA DAYTONA P.S. WELL #21, NOVA, DAYTONA DAYTONA P.S. WELL #21, NOVA, DAYTONA DAYTONA P.S. WELL #22, NOVA, DAYTONA DAYTONA P.S. WELL #22, NOVA, DAYTONA DAYTONA P.S. WELL #23, NOVA. DAYTONA DAYTONA P.S. WELL #23, NOVA. DAYTONA DAYTONA P.S.WELL #24, NOVA. DAYTONA DAYTONA P.S.WELL #24, NOVA. DAYTONA DAYTONA P.S. WELL #25, NOVA, DAYTONA DAYTONA P.S. WELL #25, NOVA, DAYTONA DAYTONA P.S. WELL #26, NOVA, DAYTONA DAYTONA P.S. WELL #26, NOVA, DAYTONA DAYTONA P.S. WELL #27, NOVA, DAYTONA DAYTONA P.S. WELL #27, NOVA, DAYTONA DAYTONA P.S. WELL #28, NOVA. DAYTONA DAYTONA P.S. WELL #28, NOVA. DAYTONA DAYTONA P.S. WELL #29, NOVA, DAYTONA DAYTONA P.S. WELL #29, NOVA, DAYTONA DAYTONA P.S. WELL #30, TUSC., DAYTONA DAYTONA P.S. WELL #30, TUSC., DAYTONA DAYTONA P.S. WELL #30, TUSC., DAYTONA DAYTONA P.S. WELL #32, TUSC., DAYTONA DAYTONA P.S. WELL #32, TUSC., DAYTONA DAYTONA P.S. WELL #32, TUSC., DAYTONA DAYTONA P.S. WELL. #33, DAYTONA DAYTONA P.S. WELL. #33, DAYTONA DAYTONA P.S. WELL #34, DAYTONA DAYTONA P.S. WELL #34, DAYTONA DAYTONA P.S. WELL #34, DAYTONA DAYTONA P.S. WELL #35, DAYTONA DAYTONA P.S. WELL #36, DAYTONA DAYTONA P.S. WELL #37, DAYTONA DAYTONA P.S. WELL #37, DAYTONA DAYTONA P.S. WELL #37, DAYTONA DAYTONA P.S. WELL #37, DAYTONA DAYTONA P.S. WELL #37, DAYTONA DAYTONA P.S. WELL #33, DAYTONA DAYTONA P.S. WELL #33, DAYTONA DAYTONA P.S. WELL #33, DAYTONA DAYTONA P.S. WELL #33, DAYTONA 79 50—00—00 —— 99 54—02—25 —— 128 50—00—00 —— 123 54—02—25 —— 186 50—00—00 —— 145 54—02—00 —— 188 50—00—00 —— 150 54—02—00 —— 186 50—00—00 —— 145 54--02--00 —— 202 54—02—00 —— 198 54—02—28 —— 82 54—03—31 —— 126 54—02—28 —— 78 54—03—31 —— 92 54—02—23 —— 64 54—03—31 —— 78 54—02—28 —— 68 54—03—31 —— 80 54—02—00 —— 52 54—03—31 —— 48 54—02—00 —— 48 54—03—31 —— 44 54—02—00 —— 56 54—03—31 —— 56 54—02—00 —— 56 34—03—31 —— 52 54—02—00 —— 52 54—03—31 —— 54 79—09—00 580 79—09—06 1325 581 82—08—24 1200 640 80--12--31 —— 150 80—12—31 1115 150 80—12—31 1121 140 82—08—24 1120 170 82—12—01 1545 150 57—03—00 —— 78 57—03—13 —— 70 57—03—21 —— 78 57—03—13 —— 30 57—03—13 —— 30 57—03—00 —— 33 57—03—13 —— 30 57—33—21 —— 33 82—03—20 1135 66 82—12—01 1325 53 57—03--13 —— 32 82—03—22 1500 99 82—08—20 1130 35 82--12--01 1312 40TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS. CONTINUED DATE OF CHLORIDE SAMPLING (YR- TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING ON (MG/L) 291126081041701 91110406 291126081041701 91110406 291126081041701 91110406 291120081042701 91110408 291120081042701 91110408 291120081042701 91110408 291126081043401 91110410 291126081043401 91110410 291126081043401 91110410 291120081044501 91110412 291120081044501 91110412 291116081045501 91110413 291116081045501 91110413 291116081045501 91110413 291116081045501 91110413 291113081050601 91110503 291113081050601 91110503 291113081050601 91110503 291113081050601 91110503 291113081050601 91110503 291113081050601 91110503 291113081050601 91110503 291109081051601 91110501 291109081051601 91110501 291109081051601 91110501 291105081052301 91110504 291105081052301 91110504 291105081052301 91110504 291105081052301 91110504 291101081053601 91110505 291101081053601 91110505 291047081061301 91010602 291047081061301 91010602 291032081065201 91010601 291032081065201 91010601 291032081065201 91010601 291032081065201 91010601 291032081065201 91010601 291031081065601 91010603 291043081071201 91010701 290830381074401 90810705 290823081080401 90810807 290820081081401 90810808 290812081083201 90810810 290139081182401 90111701 290139081182401 90111701 290139081182401 90111701 290156081183501 90111801 290156081183501 90111801 290156081183501 90111801 290156081183501 90111801 290156081183501 90111801 DAYTONA P.S. WELL #39, DAYTONA DAYTONA P.S. WELL #39, DAYTONA DAYTONA P.S. WELL #39, DAYTONA DAYTONA P.S. WELL #40, DAYTONA DAYTONA P.S. WELL #40, DAYTONA DAYTONA P.S. WELL #40, DAYTONA DAYTONA P.S. WELL #41, DAYTONA DAYTONA P.S. WELL #41, DAYTONA DAYTONA P.S. WELL #41, DAYTONA DAYTONA P.S. WELL #42, DAYTONA DAYTONA P.S. WELL #42, DAYTONA DAYTONA P.S. WELL #43, DAYTONA DAYTONA P.S. WELL #43, DAYTONA DAYTONA P.S. WELL #43, DAYTONA DAYTONA P.S. WELL #43, DAYTONA CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL CITY WELL 44 AT DAYTONA BEACH, FL DAYTONA P.S. WELL #45, DAYTONA DAYTONA P.S. WELL #45, DAYTONA DAYTONA P.S. WELL #45, DAYTONA DAYTONA P.S. WELL #46, DAYTONA DAYTONA P.S. WELL #46, DAYTONA DAYTONA P.S. WELL #46, DAYTONA DAYTONA P.S. WELL #46, DAYTONA DAYTONA P.S. WELL #47, DAYTONA DAYTONA P.S. WELL #47, DAYTONA DAYTONA P.S. WELL #48, SW OF DAYTONA DAYTONA P.S. WELL #48, SW OF DAYTONA DAYTONA P.S. WELL #49, SW OF DAYTONA DAYTONA P.S. WELL #49, SW OF DAYTONA DAYTONA P.S. WELL #49, SW OF DAYTONA DAYTONA P.S. WELL #49, SW OF DAYTONA DAYTONA P.S. WELL #49, SW OF DAYTONA DAYTONA P.S. WELL W—1, W. OF DAYTONA DAYTONA P.S. WELL W—2, W.OF DAYTONA DAYTONA P.S. WELL W—3,SW. OF DAYTONA DAYTONA P.S. WELL W—5. SW OF DAYTONA DAYTONA P.S. WELL W—6. SW OF DAYTONA DAYTONA P.S. WELL W--8, SW OF DAYTONA DELAND P.S. WELL #2, DELAND DELAND P.S. WELL #2, DELAND DELAND P.S. WELL #2, DELAND DELAND P.S. WELL #3, DELAND DELAND P.S. WELL #3, DELAND DELAND P.S. WELL #3, DELAND DELAND P.S. WELL #3, DELAND DELAND P.S. WELL #3, DELAND 80 57—03—13 —— 32 82—03—22 1505 71 82—08—20 1125 71 57—03—13 —— 30 82—12--01 1307 55 83—01—31 1245 48 63—09—12 —— 34 82—08—20 1115 55 82—12—01 1303 42 82—03—22 1510 42 82—08--20 1110 40 66—06—26 —— 63 82—03—22 1515 61 82—08—20 1105 63 82—12—01 1254 69 66—06—24 —— 74 69—05—15 1030 39 71—06—09 —— 41 72—05—08 1220 38 82—08—20 1100 130 82—12—01 1250 110 83—01—31 1250 72 66—07—06 —— 55 82—05—20 1050 210 82—12—01 1232 160 72—06—01 —— 35 79—09—00 —— 47 82—08—20 1040 230 82—12—01 1240 42 72—06—02 —— 30 52—08—20 1030 33 82—03—22 1520 33 82—08—20 945 34 72—07—14 —— 34 80—03—00 —— 30 80—03—11 945 27 82—03—22 1525 31 82—08--20 1000 36 82—12—28 1045 25 82—12—28 1105 27 82—12—16 1250 19 82—12—16 1245 23 82—12—16 1240 33 82—12—16 1220 32 57—04—22 —— 24 52—08—20 1400 13 82—11—30 850 20 57—04—22 —— 19 66—02—15 —— 19 82—03—23 1400 35 82—08—20 1405 33 82—11—30 840 40TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS--CONTINUED CHLORIDE DATE OF TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME SAMPLING SAMPLING ON (MG/L) 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290156081183401 90111802 290219081190601 90211901 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290227081171301 90211701 290208081172401 90211702 290113081173201 90111703 290113081173201 90111703 290113081173201 90111703 290308081182301 90311801 290308081182301 90311801 290156081192701 90111902 290156081192701 90111902 285419081153901 85411505 285419081153901 85411505 285419081153901 85411505 285419081153901 85411505 285416081154401 85411504 285416081154401 85411504 285416081154401 85411504 265359081161701 85311601 265359081161701 85311601 265359081161701 85311601 265359081161701 85311601 285525081143301 85511401 285525081143301 85511401 285525081143301 85511401 285525081143301 85511401 285525081143301 85511401 DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #4, DELAND DELAND P.S. WELL #5, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6, DELAND DELAND P.S. WELL #6A, DELAND DELAND P.S. WELL #7, DELAND DELAND P.S. WELL #7, DELAND DELAND P.S. WELL #7, DELAND DELAND P.S. WELL #7A, DELAND DELAND P.S. WELL #7A, DELAND DELAND P.S. WELL #8, DELAND DELAND P.S. WELL #8, DELAND DELT. P.S. WELL #1, WELLINGTON. DELTONA DELT. P.S. WELL #1, WELLINGTON. DELTONA DELT. P.S. WELL #1, WELLINGTON. DELTONA DELT. P.S. WELL #1, WELLINGTON. DELTONA DELT. P.S. WELL #2, WELLINGTON, DELTONA DELT. P.S. WELL #2, WELLINGTON, DELTONA DELT. P.S. WELL #2, WELLINGTON, DELTONA DELT. P.S. WELL #3, DIAMOND ST. DELTONA DELT. P.S. WELL #3, DIAMOND ST. DELTONA DELT. P.S. WELL #3, DIAMOND ST. DELTONA DELT. P.S. WELL #3, DIAMOND ST. DELTONA DELT. P.S. WELL #4, ELKCAM BLVD, DELTONA DELT. P.S. WELL #4, ELKCAM BLVD, DELTONA DELT. P.S. WELL #4, ELKCAM BLVD, DELTONA DELT. P.S. WELL #4, ELKCAM BLVD, DELTONA DELT. P.S. WELL #4, ELKCAM BLVD, DELTONA 81 57--04--22 —— 21 58—07—15 —— 17 66—02—00 —— 19 66--02--15 —— 19 71—06—08 —— 26 76—08—17 0820 19 77—09—01 1515 18 80--03--11 3800 46 82—08—20 1410 20 82—11—30 0835 28 83—02—01 1240 28 83—03—31 1250 25 83—04--29 1015 25 83—05—27 1230 27 83--06--30 1135 26 83—09—30 1200 28 83—11—29 0930 30 84—01--31 0920 29 84—04—05 1245 28 84—05—04 0940 33 86—06—07 0930 27 84—07—06 1200 33 82—08—20 1415 12 65—09—00 —— 15 65—09—02 —— 15 65--10--28 1620 12 65—11—00 —— 12 65—11—01 —— 12 65—12—00 1440 10 65—12—00 1540 8 65—12—02 —— 10 65—12—02 1440 10 65—12—02 1540 8 82—08—20 1420 11 57—04—22 —— 24 58—07—15 —— 18 61—05—12 —— 18 82—03—23 1405 14 82—08—20 1425 13 82—03—23 1410 16 82—08--20 1430 12 67—12—13 —— 10 82—03--29 1000 23 82—08--24 0800 16 82—12—01 0955 12 67—10—25 —— 9 82—03—29 1005 79 82—08—24 0805 24 65—07—13 —— 28 82—03—29 1010 19 82—08—24 0815 10 82—12—01 0900 9 67—10—25 —— 53 79—09—10 1230 80 82—03—29 1015 105 82—08—24 0820 110 82—12—01 0815 100TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS--CONTINUED DATE OF CHLORIDE SAMPLING (YR- TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING ON (MG/L) 285259081132101 85211301 285259081132101 85211301 285406081152301 85411501 285406081152301 85411501 285406081152301 85411501 285406081152301 85411501 285201081150201 85211504 285410081152301 85411502 285410081152301 85411502 285410081152301 85411502 285410081152301 85411502 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285348081140801 85311402 285503081124701 85511201 285340081140801 85311401 285340081140801 85311401 285340081140801 85311401 285253081141301 85211401 285253081141301 85211401 285253081141301 85211401 285253081141301 85211401 285253081141301 85211401 285631081105201 85611001 285352081141001 85311403 285352081141001 85311403 285352081141001 85311403 285634081105301 85611002 285904080554601 85905504 285904080554601 85905504 285904080554601 85905504 285904080554601 85905504 285904080554601 85905504 285904080554601 85905504 285904080554601 85905504 28585808055701 85805501 28585808055701 85805501 285852080561401 85805601 285852080561401 85805601 291444081022201 91410201 291444081022201 91410201 291444081022201 91410201 291444081022201 91410201 291444081022201 91410201 DELT. P.S. WELL #5, SAXON, DELTONA DELT. P.S. WELL #5, SAXON, DELTONA DELT. P.S. WELL #6, FIRE STA., DELTONA DELT. P.S. WELL #6, FIRE STA., DELTONA DELT. P.S. WELL #6, FIRE STA., DELTONA DELT. P.S. WELL #6, FIRE STA., DELTONA DELT. P.S. WELL #7, WHISKEY L., DELTONA DELT. P.S. WELL #8, FIRE STA., DELTONA DELT. P.S. WELL #8, FIRE STA., DELTONA DELT. P.S. WELL #8, FIRE STA., DELTONA DELT. P.S. WELL #8, FIRE STA., DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #9, SAXON BLVD, DELTONA DELT. P.S. WELL #11, NEMO ST. DELTONA DELT. P.S. WELL #12, HOLLYHOCK, DELTONA DELT. P.S. WELL #12, HOLLYHOCK, DELTONA DELT. P.S. WELL #12, HOLLYHOCK, DELTONA DELT. P.S. WELL #14, SAXON BLVD,DELTONA DELT. P.S. WELL #14, SAXON BLVD,DELTONA DELT. P.S. WELL #14, SAXON BLVD,DELTONA DELT. P.S. WELL #14, SAXON BLVD,DELTONA DELT. P.S. WELL #14, SAXON BLVD,DELTONA DELT. P.S. WELL #15, COURTLAND, DELTONA DELT. P.S. WELL #16, DELTONA DELT. P.S. WELL #16, DELTONA DELT. P.S. WELL #16, DELTONA DELT. P.S. WELL #17, COURTLAND, DELTONA EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #1, W. OF EDGEWATER EDGEWATER P.S. WELL #2, W. OF EDGEWATER EDGEWATER P.S. WELL #2, W. OF EDGEWATER EDGEWATER P.S. WELL #3, W. OF EDGEWATER EDGEWATER P.S. WELL #3, W. OF EDGEWATER HOLLY HILL P.S. WELL #1, HOLLY HILL HOLLY HILL P.S. WELL #1, HOLLY HILL HOLLY HILL P.S. WELL #1, HOLLY HILL HOLLY HILL P.S. WELL #1, HOLLY HILL HOLLY HILL P.S. WELL #1, HOLLY HILL 82 65--11--15 —— 38 82—04—13 1100 99 66—03—14 —— 39 82—04—13 1105 22 82—08—24 825 18 82—12—01 845 15 67—10—25 —— 9 67—01—03 —— 9 82—04—13 1110 49 82—08—24 830 12 82—12—01 947 14 66—12—13 —— 15 77—11—02 1330 140 82—03—29 1025 240 82—08—24 835 120 82—12—01 833 78 83—02—01 1320 60 53—03—31 1400 89 83—04—29 930 97 83—05—27 1145 64 83—06—30 1215 58 83—09—30 1300 56 83—12—02 840 66 84—01—31 1030 73 84—04—05 1410 51 84—05—06 1045 64 84—06—07 1050 66 68—12—16 —— 360 82—04—13 1115 67 82—08—24 840 70 82—12—01 830 70 70—12—07 —— 60 79—09—10 1140 114 82—03—29 1030 170 82—08—26 840 42 82—12—01 836 24 82—03—29 1035 30 82—03--29 1040 240 82—08—24 845 130 82—12—01 835 91 82--03--29 1045 9 57--12--00 —— 64 58--06--10 —— 45 72--05--10 1500 78 76--08--27 945 58 79--09--00 —— 110 82--03--22 1145 210 82--12--08 1240 210 82--03--22 1150 160 82--12--08 1250 140 82--03--22 1155 58 82--12--08 1245 55 50--04--05 —— 70 50--08--00 —— 73 50--09--00 —— 75 54--11--16 —— 71 77--11--02 1515 160TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS--CONTINUED DATE OF CHLORIDE SAMPLING (YR- TIME OF CONCENTRATI STATION NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING ON (MG/L) 291434081025002 91410211 291429081024702 91410213 291429081024702 91410213 291429081024702 91410213 291425081024501 91410214 291425081024502 91410215 291436081024701 91410216 291436081024701 91410216 291436081024701 91410216 291436081024701 91410216 291435081025501 91410218 290039081204701 90012022 290039081204701 90012022 290039081204701 90012022 290039081204601 90012021 290039081204601 90012021 290039081204601 90012021 285840081135601 85811301 285840081135601 85811301 285840081135601 85811301 285951080574701 85905705 285951080574701 85905705 285951080574701 85905705 285951080574701 85905705 285951080574701 85905705 285952080574801 85905701 285952080574801 85905701 285951080575101 85905702 285951080575101 85905702 285949080575001 85905703 285949080575001 85905703 285949080575001 85905703 285951080575501 85905712 285953080575902 85905710 285953080575902 85905710 285945080580001 85905801 290040081050101 90010501 290047081052301 90010503 285641081175501 85611703 285641081175501 85611703 285641081175502 85611704 285636081175501 85611702 285636081175501 85611702 285638081175501 86511705 291645081034801 91610301 291645081034801 91610301 291645081034801 91610301 291644081034701 91610302 291644081034701 91610302 291644081034701 91610302 HOLLY HILL P.S. WELL #6A, HOLLY HILL HOLLY HILL P.S. WELL #7A, HOLLY HILL HOLLY HILL P.S. WELL #7A, HOLLY HILL HOLLY HILL P.S. WELL #7A, HOLLY HILL HOLLY HILL P.S. WELL #8, HOLLY HILL HOLLY HILL P.S. WELL #8A, HOLLY HILL HOLLY HILL P.S. WELL #9. HOLLY HILL HOLLY HILL P.S. WELL #9. HOLLY HILL HOLLY HILL P.S. WELL #9. HOLLY HILL HOLLY HILL P.S. WELL #9. HOLLY HILL HOLLY HILL P.S. WELL #11, HOLLY HILL L.BERESFORD P.S. WELL #1, SW OF DELAND L.BERESFORD P.S. WELL #1, SW OF DELAND L.BERESFORD P.S. WELL #1, SW OF DELAND L.BERESFORD P.S. WELL #2, SW OF DELAND L.BERESFORD P.S. WELL #2, SW OF DELAND L.BERESFORD P.S. WELL #2, SW OF DELAND L. HELEN P.S. WELL, LAKE HELEN L. HELEN P.S. WELL, LAKE HELEN L. HELEN P.S. WELL, LAKE HELEN NSB PS WELL NUMBERED 3 IN 1947,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1947,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1947,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1947,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1947,N.SMYRNA NSB PS WELL NUMBERED 1 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 1 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 2 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 2 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 3 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 6 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 7 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 7 IN 1980,N.SMYRNA NSB PS WELL NUMBERED 8 IN 1980,N.SMYRNA NSB P.S. WELL #53, SAMSULA NSB P.S. WELL #55, SAMSULA ORAN.CITY P.S. WELL #1, ORANGE CITY ORAN.CITY P.S. WELL #1, ORANGE CITY ORAN.CITY P.S. WELL #2, ORANGE CITY ORAN.CITY P.S. WELL #3, ORANGE CITY ORAN.CITY P.S. WELL #3, ORANGE CITY ORAN.CITY P.S. WELL #4, ORANGE CITY ORMOND P.S. WELL #1, ORMOND BEACH ORMOND P.S. WELL #1, ORMOND BEACH ORMOND P.S. WELL #1, ORMOND BEACH ORMOND P.S. WELL #2, ORMOND BEACH ORMOND P.S. WELL #2, ORMOND BEACH ORMOND P.S. WELL #2, ORMOND BEACH 83 82—12—01 1013 70 82—03—22 1630 190 82—12—01 958 150 83—01—31 1330 240 80—09—23 1530 440 82—12—01 1030 140 79—09—00 —— 74 82—03—22 1635 210 82—12—31 955 320 83—01—31 1315 340 82—12—01 1000 70 65—08—18 —— 68 82—08—24 1305 170 82—12—08 1545 230 65—08-18 —— 25 82—05—24 1310 24 82—12—08 1550 51 50—11—21 —— 10 66—04—28 —— 10 82—12—08 1015 11 70—05—07 —— 73 71—05—14 —— 56 71—06—08 —— 53 72—05—10 1400 80 82—12—08 1225 88 82—12—01 1150 100 83—01—31 1045 98 79—09--00 —— 82 82—03—22 1105 94 55—06—02 —— 54 82—12—01 1200 61 83—01—31 1040 55 79—09—00 —— 71 77—12—05 1130 76 78--05--00 —— 71 82—03—22 1100 51 82—03—22 1050 13 82—03—22 1040 9 64—08—26 —— 20 65--08--19 —— 14 81--12--18 915 18 65—01—19 —— 11 68—08—24 —— 16 82—03—23 1420 19 54—11—16 —— 200 82—08—20 1215 230 82—12—01 1101 230 54—11—16 —— 220 82—08—20 1220 180 82—12—01 1101 120TABLE OF SUPPLEMENTAL DATA--CHLORIDE CONCENTRATIONS IN PUBLIC-SUPPLY WELLS--CONTINUED DATE OF CHLORIDE STATION SAMPLING (YR- TIME OF CONCENTRATI

NO. LOCAL NO. AND WELL NAME MO-D) SAMPLING ON (MG/L) 291643081034601 91610303 291643081034601 91610303 291643081034601 91610303 291643081034401 91610304 291641081034501 91610307 291646081034601 91610306 291646081034601 91610306 291646081034601 91610306 291646081034601 91610306 291616081040301 91610404 291616081040301 91610404 291616081040301 91610404 291614081040901 91610406 291607081042301 91610408 291607081042301 91610408 291607081042301 91610408 291608081042101 91610409 291608081042101 91610409 291558081044301 91510401 291628081040101 91610413 291628081040101 91610413 291628081040101 91610413 291623081041101 91610614 291611081043201 91610416 291601081060801 91610603 291527081064601 91510605 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290742081013901 90810103 290813081013801 90810104 290818081013801 90810105 290813081014101 90810106 290813081014101 90810106 290835081013801 90810108 290840081013801 90810109 290846081014401 90810111 290846081014901 90810112 290846011015501 90810113 290846081020101 90810202 290846081020701 90810203 ORMOND P.S. WELL #3, ORMOND BEACH ORMOND P.S. WELL #3, ORMOND BEACH ORMOND P.S. WELL #3, ORMOND BEACH ORMOND P.S. WELL #4, ORMOND BEACH ORMOND P.S. WELL #5, ORMOND BEACH ORMOND P.S. WELL #6, ORMOND BEACH ORMOND P.S. WELL #6, ORMOND BEACH ORMOND P.S. WELL #6, ORMOND BEACH ORMOND P.S. WELL #6, ORMOND BEACH ORMOND P.S. WELL #8, ORMOND BEACH ORMOND P.S. WELL #8, ORMOND BEACH ORMOND P.S. WELL #8, ORMOND BEACH ORMOND P.S. WELL #10, ORMOND BEACH ORMOND P.S. WELL #12, ORMOND BEACH ORMOND P.S. WELL #12, ORMOND BEACH ORMOND P.S. WELL #12, ORMOND BEACH ORMOND P.S. WELL #13, ORMOND BEACH ORMOND P.S. WELL #13, ORMOND BEACH ORMOND P.S. WELL #17, ORMOND BEACH ORMOND P.S. WELL #18, ORMOND BEACH ORMOND P.S. WELL #18, ORMOND BEACH ORMOND P.S. WELL #18, ORMOND BEACH ORMOND P.S. WELL #19, ORMOND BEACH ORMOND P.S. WELL #21, ORMOND BEACH ORMOND P.S. WELL #22, ORMOND BEACH ORMOND P.S. WELL #24, ORMOND BEACH PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #4, PORT ORANGE PORT ORANGE P.S. WELL #5, PORT ORANGE PORT ORANGE P.S. WELL #6, PORT ORANGE PORT ORANGE P.S. WELL #7, PORT ORANGE PORT ORANGE P.S. WELL #7, PORT ORANGE PORT ORANGE P.S. WELL #9, PORT ORANGE PORT ORANGE P.S. WELL #10, PORT ORANGE PORT ORANGE P.S. WELL #12, PORT ORANGE PORT ORANGE P.S. WELL #13, PORT ORANGE PORT ORANGE P.S. WELL #14, PORT ORANGE PORT ORANGE P.S. WELL #15, PORT ORANGE PORT ORANGE P.S. WELL #16, PORT ORANGE
84 54—11—16 —— 190 82—08—20 1225 240 82—12--01 1103 130 54--11--16 —— 200 82--12--01 1105 130 23—07—00 —— 146 23—07—08 —— 146 54—11—16 —— 196 71—06—08 —— 192 82—03—23 1200 150 82—12—01 1129 110 83—01—31 1410 170 82—03—23 1205 140 72—05—05 1100 136 79—09—00 130 82--12--01 1121 120 79--09--00 —— 110 82—03—23 1210 120 82—03—23 1215 130 82—03—23 1220 190 82—12—01 1113 190 83—01—31 1400 200 82—03—23 1225 170 82—03---23 1230 130 82—03—23 1235 120 82—03—23 1240 72 72—05—10 1300 89 76—08—27 820 68 78—04—10 —— 93 79—08—16 —— 68 79—09—07 1145 76 80—03—25 —— 78 80—10—08 —— 85 82—03—22 1300 83 82—03—22 1305 85 82—03—22 1310 58 82--12--01 1100 160 83--01--31 1130 150 82—03—22 1315 59 82—03—22 1320 66 82—03—22 1325 72 82—03—22 1330 84 82—03—22 1335 63 82—03—22 1340 63 82—03—22 1345 61