United States
                    Environmental Protection
Environmental Monitoring
Systems Laboratory
Las Vegas, NV 89193-3478
                    Research and Development
EPA/600/SR-93/107  September 1993
w EPA      Project Summary

                    Case  Studies in  Wellhead
                    Protection Area
                    Delineation  and  Monitoring
                    Beth A. Moore
                     Groundwater monitoring is one of
                    many management options for Well-
                    head Protection Program implementa-
                    tion. Groundwater  parameters  are
                    monitored (1) to assess source-control
                    measures, (2) to  monitor compliance
                    with drinking water standards at sites
                    other than the wellhead, and (3) to pro-
                    vide advance warning of contaminants
                    in ground water. Cooperative  research
                    was conducted with five municipalities
                    to develop long-term monitoring pro-
                    grams for their existing wellhead pro-
                    tection  areas. The  product of this
                    research is a technical assistance docu-
                    ment which  contains a methodology
                    for planning and implementing a well-
                    head protection monitoring program.
                    The methodology emphasizes source
                    assessment, correct  wellhead protec-
                    tion area  delineation, and hydrogeo-
                    logic characterization. Five case studies
                    are included in the document  to exem-
                    plify the monitoring  methodology for
                    different hydrogeologic  and  contami-
                    nant source settings.
                     The five case study research sites
                    include Stevens Point, Wl; Littleton, IMA;
                    Sioux Falls, SD; Dover, NH; and Spring-
                    field, MO. Three of these municipalities
                    obtain their drinking water from uncon-
                    fined aquifers; two aquifers receive sig-
                    nificant recharge  from a nearby pond
                    and river. Two other case study sites
                    are situated  in fractured-bedrock and
                    karst limestone aquifers. The document
                    emphasizes  a multi-disciplinary  ap-
                    proach for hydrogeologic characteriza-
                    tion,  wellhead   protection  area
                    delineation, and flowpath assessment.
                    Hydrogeologic characterization tech-
niques include: well installation, water
quality sampling and assessment, geo-
logic and structural-control mapping,
aquifer testing, dye tracing, borehole
geophysics, analytical solutions, and
groundwater flow modeling. Long-term
monitoring programs for wellhead pro-
tection include monitoring objectives,
existing and new monitoring sites, guid-
ance for monitoring site construction
and installation, sampling protocol, op-
timal monitoring parameters and fre-
quencies, and quality assurance and
quality control considerations.
  This Project Summary was developed
by  EPA's  Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at

  The increasing contaminant threat  to
public water supply wells has created a
new political and technical awareness of
groundwater protection programs. Recog-
nizing the need for conjunctive manage-
ment of contaminant sources and public
water supplies to prevent, or minimize,
groundwater quality degradation, Congress
amended the Safe  Drinking Water Act in
1986 to include Section 1428. This sec-
tion mandated the  development  of the
Wellhead Protection Program (WHPP),
which established a legal framework  to
protect public water supply wells, wellfields,
and springs from contamination. An im-
portant technical element of WHPP imple-
mentation is wellhead  protection area
                                                                     Printed on Recycled Paper

                                                 Monitoring well
                       Water well
                                                                                             Water table
                                                                      contamination plume
Figure 1.  Conceptual wellhead protection area and monitoring scenario.
delineation. A wellhead protection area
(WHPA)  is defined as the surface and
subsurface  area  surrounding a well,
wellfield,  or  spring, through which con-
taminants may pass and reach the ground
water contributing  to the supply  source
(Figure 1). Criteria and methods for WHPA
delineation are given in  several U.S. Envi-
ronmental Protection Agency (EPA) guid-
ance documents.
  Groundwater monitoring may enhance
source characterization, WHPA delinea-
tion, and new water supply  evaluation.
This technical assistance document pro-
vides information to local, state, and tribal
governments and the EPA Regions in their
implementation of  WHPPs. The primary
goals of  this document are to present a
monitoring methodology for WHPAs and
to  exemplify  this  methodology  in five
unique case study  settings.

Wellhead Protection Area
   In  1989,  U.S.  EPA's  Environmental
Monitoring Systems Laboratory (EMSL) at
Las Vegas, NV, engaged in cooperative
research with five  carefully selected mu-
nicipalities to develop proposed, long-term
monitoring  programs  for their  existing
WHPAs. The  product  of the cooperative
research contains two types of informa-

    (1)  A recommended methodology for
        planning and implementing a well-
        head protection monitoring pro-
        gram which emphasizes source
        assessment, correct WHPA de-
        lineation, and hydrogeologic char-
    (2)  Five case" study narratives used
        to exemplify the monitoring meth-
        odology for different  hydrogeo-
        logic  and  contaminant source
        settings (Table 1).

  The monitoring methodology is intended
to  serve  as a  guide for  WHPP  imp-
lementors in establishing technically de-
fensible, reliable, and effective groundwa-
ter monitoring programs for wellhead pro-
tection. This  methodology emphasizes
saturated zone monitoring.  The first four
case study narratives are presented in the
document in order of  increasing hydro-
geologic complexity (aquifer heterogene-
ity). The exception to this organization is
the Springfield, MO, case study, which is
presented in abbreviated form in an ap-
  Basic hydrogeology concepts and equa-
tions are reviewed including: groundwa-
ter systems and flow, conceptual hydro-
geologic models and flow nets, and accu-
rate delineation and monitoring  in differ-
ent hydrogeologic settings. The spectrum
of unconfined to confined  aquifer condi-
tions is discussed in relation to porous,
granular aquifers; fractured-bedrock aqui-
fers; and karst aquifers.
  Physical and chemical parameter moni-
toring apply to wellhead protection. Three
types of groundwater monitoring are use-
ful in  managing WHPAs: ambient trend,
source  assessment, and  early-warning
detection monitoring. Ambient trend moni-
toring  detects the temporal and spatial
trends in physical and chemical  quality of
the groundwater system. Source assess-
ment monitoring evaluates the existing or
potential impacts on the physical  or chemi-
cal groundwater system from a proposed,
active, or abandoned contaminant source.
Early-warning detection monitoring is con-
ducted upgradient from  the wellhead,
based on known travel times, to trigger a
contingency response  to  prevent public
exposure to contaminants.  These types of
monitoring are incorporated to measure or
detect  contaminants  in  aquifers, and
should  not be mistaken as  preventative or
remedial measures.

Table 1.  Characteristics of the Case Study Research Sites.
                                     Hydrogeologic setting
        Characterization tasks
  Stevens Point, Wl
  Littleton, MA
  Sioux Falls, SD
  Dover, NH
  Springfield, MO
                       Unconfined aquifer
                       Unconfined aquifer, rehcarge from
                       Spectacle Pond
                       Undonfined aquifer; recharge from the
                       Big Sioux River
                       Fractured-bedrock aquifer, discrete
                       flow system
                       Mature karst (porous limestone)
                       aquifer, conduit flow system
Flowsystem modeledwith FLOWPATH (2-dimensional, steady
state); point and nonpoint sources assessed

Flow system modeled with FLOWPATH (2-dimensional,
steady state); MODFLOW (3-dimensional, steady state);
and FLOWCAD (2-dimensional, transient); Industrial and
commercial point sources assessed

Flow system modeled with FLOWPATH (2-dimensional,
steady state); Big Sioux River assessed as a line source;
point and nonpoint sources present

Flow system characterized with lineament analysis,
structural control mapping, aquifer testing, dye tracing, and
borehole geophysics; a few commercial, point sources,
and natural sources

Flow system determined by watershed boundaries, dye
tracing, and flow analysis; point and nonpoint sources
  Source assessment is a critical first step
in designing an effective monitoring pro-
gram. Target  monitoring parameters  for
early-warning  detection and source  as-
sessment are selected from a compre-
hensive list of known and suspected con-
taminants associated with land-use activi-
ties and practices. Optimal monitoring sites
may be determined, reflecting prioritization
of sources.  An  inventory  of  common
sources  of contamination within and in
proximity to WHPAs is included.
  The monitoring methodology  is divided
into three phases:

   Phase  I:   WHPP  Elements and
    Scoping Tasks
   Phase II:  Research Monitoring Pro-
   Phase III: Wellhead Protection Moni-
    toring Program

Phase I WHPP  elements  and scoping
tasks include:  designating roles and a
management framework,  preliminary
WHPA delineation, and source assess-
ment. To support the research monitoring
task, an  initial information base of  ancil-
lary and  monitoring data should be com-
piled and reviewed to determine data limi-
tations and gaps. The strategy is to maxi-
mize information content; to define moni-
toring objectives; and to conduct field stud-
ies with the least, but still adequate num-
ber of monitoring points. Existing monitor-
ing sites identified  in this phase can be
incorporated  in the long-term monitoring
                                  network. Phase I generally requires a 3-
                                  to 6-month period for completion.
                                    Phase II is aptly named the Research
                                  Monitoring Program, or the phase of ac-
                                  quiring information  pertaining to how the
                                  subsurface system operates and  of  for-
                                  mulating interpretations. Research  moni-
                                  toring is conducted to  improve, or verify,
                                  elements of the hydrogeologic conceptual
                                  model. A technically defensible concep-
                                  tual flow model ensures a more protective
                                  and reliable monitoring program. Research
                                  monitoring for wellhead protection includes
                                  baseline water  quality characterization,
                                  aquifer testing  and characterization, re-
                                  fined  or verified WHPA delineation, and
                                  groundwater flowpath determination to re-
                                  late sources to the water supply well or
                                  spring. The product of research monitor-
                                  ing is a proposed long-term  monitoring
                                  program that may be partly implemented
                                  in Phase II. Phase II may require 1 to 1.5
                                  years for completion,  depending on  the
                                  complexity of the site  hydrogeology and
                                  the quality of the initial  information base.
                                    The by-product of Phases I and II is a
                                  proposed wellhead protection monitoring
                                  program,  Phase  III. Generally,  the pro-
                                  gram is submitted as a plan to be imple-
                                  mented in stages, as labor and financial
                                  resources  become available. The  plan
                                  should include an  organization chart, a
                                  source assessment map and list,  and a
                                  map depicting the WHPA and protective
                                  zones, as well  as a  description  of  the
                                  delineation criteria  and method(s). Gen-
                                  eral  and specific objectives for ambient
                                  trend, source assessment, and early-warn-
           ing detection  monitoring should  be de-
           tailed.  Each objective should justify the
           selection of monitoring sites, parameters,
           and frequencies.
             The  locations of existing and  recom-
           mended monitoring sites in the proposed
           network should be shown  on a map. A
           formal  identification system with  a mini-
           mum set of data elements should be used
           to label each site. The integrity  of the
           design and construction of each existing
           site should be considered  prior to inclu-
           sion in the monitoring network to ensure
           data quality. New sites that require instal-
           lation should be described  in detail, con-
           cerning  completion  depth,  open  or
           screened interval,  schematic design, and
           construction materials, as well as the meth-
           ods of installation, development, and test-
           ing. Physical and chemical parameters to
           be monitored at select frequencies should
           be listed and technically justified. Monitor-
           ing site information should be stored in an
           automated data base for convenient and
           safe storage, update, and retrieval. Each
           monitoring program should formulate a
           minimum set of quality assurance and con-
           trol objectives to match the objectives of
           the wellhead  protection  monitoring pro-
             A 15-step approach for the design of a
           wellhead protection monitoring program is
           depicted as a flowchart in  Figure 2. The
           monitoring program should be reviewed
           and improved  in an iterative process over
           the life span of the WHPP. The organiza-
           tion of  the case studies research follows
           the logical outline of Phases I, II, and III.

Stevens Point, Wl: Case Study
  The city of Stevens Point is located in
central Wisconsin and has a population of
approximately 23,000. The source of the
city water supply is from the Airport and
Iverson wellfields. These wellfields pump
an average  of 5  million gallons of water
per day from a shallow, unconfined aqui-
fer. The aquifer is composed of coarse,
unconsolidated sediments deposited  by
meltwater during the Wisconsin glaciation.
The preliminary wellhead protection zones
for the combined wellfields were based on
estimates of the zone of influence, the 5-
year time-of-travel (TOT) zone (analyti-
cally determined), and the recharge area.
In the review process, the validity of the
5-year TOT calculation was  questioned,
and the WHPA was never promulgated.
  An extensive,  historical source assess-
ment was conducted within the B Zone of
the preliminary WHPA using aerial photo-
graphic interpretation techniques combined
with conventional methods such  as sur-
veys of directories, local and state records,
visual inspections, and monitoring data.
Point and nonpoint sources  were identi-
fied, ranked, and prioritized for manage-
ment and regulation. Existing contaminant
sources were given highest priority.  Po-
tential sources were then prioritized based
on source type, quantity, hazard, and lo-
   A network of 55 monitoring sites (single
monitoring wells, well nests,  and a multi-
level well) were  used to measure water
levels, to sample ground water,  and to
conduct  aquifer  tests in  the unconfined
aquifer. Of the total network, three single
wells and four well nests represent new
monitoring points installed for this research.
Aquifer parameter results from slug, con-
stant-discharge,  and recovery tests indi-
cate a range of hydraulic conductivity  val-
ues for three distinct geologic settings:
820 to 1,700 ft per day (ft/d) for the buried
valley, 220 to 240 ft/d for outwash plains,
and 2 to 3 ft/d for bedrock highs.
   Hydrochemical data indicate that nitro-
gen concentrations, a key indicator of con-
tamination,  have increased over time.
 Currently, nitrogen concentrations in the
 monitoring  network range from less than
 0.2 to 26.0 mg/L Other indicators of
 groundwater degradation include iron  and
 manganese from organic-rich soils located
 along the Plover River, chloride in proxim-
 ity to roads where  de-icing occurs,  and
 previous volatile organic compound con-
 tamination  at the Airport and several un-
 derground storage tanks.
   A two-dimensional,  groundwater  flow
 model (FLOWPATH) was used  to delin-
 eate the 5- and 10-year TOT zones for
 the Airport  and Iverson wellfields. In corn-
            program design
       Conduct source assessment
             within WHPA
                                              Determine sampling frequencies
                                                 for monitoring parameters
        Compile & organize existing
            information base
                                                   Assess need for new
                                                     monitoring sites
          Identify deficiencies of
            information base
                                                      Establish new
                                                     monitoring sites
       Determine data & processing
     needs for system characterization
                                                   Implement monitoring
           Establish monitoring
                                                    Review & interpret
                                                    monitoring results
          Determine monitoring
                                                Incorporate interpretations in
                                                characterization assessments
        Identify existing monitoring
         sites based on objectives
                                                Update monitoring objectives,
                                                 network design, & program
                                                 f  Iterate monitoring  N
                                                 V       process      J
Figure 2.  Flowchart of the 15-step monitoring methodology for wellhead protection areas
parison, the previous, analytically derived
B Zone is larger; however, the 5-year TOT
zone from FLOWPATH extends farther to
the east due to the effects of pumping at
the Iverson wellfield and the presence of
bedrock highs.
  A long-term groundwater monitoring net-
work  is  proposed for  the  Airport  and
Iverson wellfields consisting of 34 existing
and proposed wells. Nine new well loca-
tions are proposed to fill data gaps in the
existing  network,  primarily along  the
boundaries  of the 5- and 10-year TOT
zones. Wells in the long-term monitoring
network should be sampled twice a year
in April and September for  indicator pa-
rameters. Water levels should be recorded
each time a well is sampled. Compliance
monitoring networks are recommended for
point sources of highest priority.
  The wellhead protection  contingency
plan consists  of three components: (1)
reaction to the early-warning detection sys-
tem based on preventive action and state
drinking water limits,  (2) spill response,
and (3) new water-supply development
and implementation.

Littleton, MA: Case Study
  The town of Littleton is located approxi-
mately 35 miles northwest of Boston in
northeastern  Massachusetts.  The daily
water demand for the town's population of
7,300 is from  800,000 to  1,500,000 gal-
lons per day from four production wells.
Techniques  for  refined delineation and
long-term monitoring  of the WHPA sur-
rounding Production Well Number 5 (PW-
5) are discussed.  Production Well Num-
ber 5 is completed at a depth of 167 ft

within saturated, stratified valley-fill depos-
its. The aquifer is unconfined and receives
significant surface-water recharge (20 to
25%) from nearby Spectacle Pond and
Bennetts Brook.
  Land-use activities within the .WHPA
cover a range of commercial, industrial,
and to a lesser degree, agricultural opera-
tions. Collectively, these land-use activi-
ties pose potential contamination threats
to the aquifer, including heavy metals, vola-
tile  organic compounds, pesticides, and
nutrients. Baseline monitoring results indi-
cate that groundwater quality within the
capture zone of  PW-5 is currently  unaf-
fected by source operations. Sodium is
the only exception. Slightly elevated lev-
els  of sodium in surface water and the
shallow aquifer are attributed to roadway
de-icing. Manganese and iron concentra-
tions are elevated throughout the recharge
area of PW-5, primarily  because of their
occurrence in wetland sediments and gla-
cial deposits. The levels of these param-
eters have increased at  PW-5 for several
years and  may warrant treatment in the
  The PW-5 WHPA consists of three pro-
tection zones delineated using  a combi-
nation of numerical groundwater flow mod-
els  (FLOWPATH,  FLOWCAD,  and
MODFLOW) and hydrogeologic mapping.
Zone I is the 400-foot sanitary protective
radius mandated by the State of Massa-
chusetts. Zone II is the most critical man-
agement area and was delineated con-
servatively as the union of three numeri-
cal capture zone solutions. These numeri-
cal solutions incorporate two- and three-
dimensional flow, as well as steady-state
and transient flow conditions. Local and
regional groundwater flow simulations are
based on the results of short- and long-
term aquifer testing.
  Zone II generally represents the steady-
state capture zone for  PW-5 that corre-
sponds  approximately  to the 400-day
travel-time contour. Flowpath simulations
indicate that Zone II  extends to the bot-
tom of the aquifer and is  constrained by
bedrock and glacial  till. Within  Zone II,
three existing wells and two new wells are
proposed for inclusion in  the monitoring
network for early-warning  detection  and
source assessment purposes.  These wells
lie  along  either  the  150-day  or the 300-
day travel-time contours. Screened inter-
vals for the  new monitoring wells  were
chosen based on results from MODPATH
computer flow simulations. Monitoring pa-
rameter groups  for these wells  include
general  water  quality,  site-specific,  and
physical parameters. Recommended moni-
toring frequencies  for  these  parameter
groups vary from quarterly to annually,
 depending on the travel-time distance from
 the monitoring well to PW-5 and the moni-
 toring well depth.
   Zone  III is defined  as the upgradient
 area of the aquifer that contributes to Zone
 II and extends to the  watershed bound-
 ary. Zone  III is monitored at two surface-
 water locations, one at the inflow and one
 at the outflow of Spectacle Pond. In addi-
 tion,  Zone III is  monitored biannually at
 existing compliance  networks around
 waste management and industrial sites.
 Monitoring parameters for the compliance
 wells include general water quality, site-
 specific, and physical parameter groups.
   The Littleton WHPP incorporates con-
 tingency planning. Catastrophic releases
 initiate a spill-response plan that involves
 many departments and  agencies. In  the
 event of contamination  of PW-5  or  an-
' other production  well,  Littleton has sited
 a new production well. The proposed well
 site is approved by the State, and protec-
 tion Zones I, II, and III are delineated. The
 adjacent town of Boxborough shares the
 recharge  area  to  the  proposed well.
 Boxborough has  adopted complementary
 strategies with Littleton to ensure its water
 quality protection.

 Sioux Falls, SD: Case Study
   The city of Sioux  Falls is located in the
 southeast corner of South Dakota. The
 Big Sioux  aquifer is  the primary source of
 water for  about  125,000 persons in  the
 Sioux Falls metropolitan  area. One of the
 municipal  wells in the Big Sioux aquifer,
 the airport wellfield, is underlain by surficial,
 glacial  outwash  deposits. The Big Sioux
 River is located directly west  of the airport
 wellfield and flows south  over and through
 the outwash, draining approximately 4,000
 square miles of upstream land.
   The city's wells pump  most of their wa-
 ter directly from  the aquifer  and a small
 quantity from the Big  Sioux River. How-
 ever, the  river is hydraulically connected
 to the aquifer, and recharge from the river
 in the airport wellfield area is significant.
 In 1988,  approximately 79% of the re-
 charge to  the airport wellfield aquifer was
 induced from the river due to wells pump-
 ing.  Induced flow from  the river to the
 aquifer is demonstrated by decreased flow
 in the river during low  recharge periods.
   This research  was conducted to evalu-
 ate (1) the hydraulic connection between
 the Big  Sioux River and the adjacent aqui-
 fer,  and (2) the potential impact of the
 river on  aquifer water quality.  In  the
 broader perspective, additional goals in-
 cluded  refined delineation of the wellfield
 protection area and design of a long-term
 water quality monitoring  program.
  Drilling logs indicate that the thickness
of the aquifer in the wellfield area ranges
from 20 to 50 ft. Aquifer testing results
yield an  average  hydraulic conductivity
value of 800 ft/d and a transmissivity value
of approximately 21,000 ft2/d for the aqui-
  Many potential point  sources of  con-
tamination exist in  the study area. These
include: industrial and commercial areas,
the South Dakota Air National Guard facil-
ity,  a petroleum pipeline, the Sioux Falls
Regional Airport, and a  decommissioned
municipal  landfill. The threat of contami-
nation from these sources is underscored
by the recent history of contaminant re-
leases in the area.
  To estimate groundwater travel times in
the study  area, aquifer testing,  dye trac-
ing, and groundwater modeling were em-
ployed. During aquifer  testing, two dye
injections were made. The first dye was
injected in a well approximately 40 ft north
of the pumping well. Detectable dye con-
centrations first arrived at the pumped well
after about  12 hours. The second dye
was injected in a well near the edge of the
river, approximately 140 ft  north of the
pumping well. Detectable dye concentra-
tions from the second injection  site first
arrived at the pumped well in 7 to 9 days.
Aquifer testing and dye-tracing results in-
dicate that a contaminant could travel from
the river to the wellfield  in less than  9
  A two-dimensional, steady-state model
(FLOWPATH) was used to generate time-
related capture zones for the municipal
wells and to  simulate contaminant travel
times.  One-,  two-, and  five-year capture
zones  were  calculated for  each of the
municipal wells in the airport wellfield.
Modeling of simulated spill sites from sev-
eral of the potential point-source contami-
nation areas indicates that contaminants
entering the aquifer at areas to the north
and south of the well field could reach the
municipal wells in 1 to 2 years.
  The City of Sioux Falls and Minnehaha
County have delineated wellhead protec-
tion areas by using  the  hydrogeologic-
mapping method. Wellhead protection or-
dinances  are  designed  to impose guide-
lines and restrictions on  new land uses, or
proposed changes in existing  use, in or-
der to  protect the aquifer water quality.
   A wellhead protection monitoring pro-
gram at the airport wellfield is proposed to
document ambient water quality conditions
and to serve  as an  early-warning detec-
tion system. Line-source monitoring is pro-
posed to monitor the Big Sioux aquifer
and the diversion  canal for contaminants
that could potentially enter the aquifer.
Point-source  and  nonpoint-source moni-

toring are proposed to monitor water qual-
ity between the  airport wellfield and po-
tential sources. The categories of param-
eters for monitoring are general water qual-
ity, volatile organic compounds, trace met-
als, pesticides, and nutrients.  Sampling
frequencies for each of the categories were
selected as a function of the type of source
to be  monitored.
  Contingency planning is warranted to
establish emergency  responses to con-
taminant releases at  the  surface  of the
aquifer and in the river. Alternative water
supply development must  also be contin-
ued as part of the  contingency planning

Dover, NH: Case  Study
  Dover is a city of 26,000 people located
in the seacoast region of New Hampshire.
To meet the increasing water supply de-
mands of the future, the city embarked on
a water  exploration effort in a fractured-
bedrock  aquifer  at the Blackwater Brook
site. A test well was installed to a depth of
400 ft in the bedrock aquifer as part of the
groundwater exploration program. A well-
head protection  area and  groundwater
monitoring strategy were  established for
the test  well.  This study  describes how
the conceptual hydrogeologic model  for
the site was developed and refined.
  The bedrock aquifer consists primarily
of quartz monzonite and metasedimentary
rocks that interfinger along a  fractured,
faulted contact zone trending north 60 de-
grees east (N60E). A N5-10W trending
lineament and fracture zone intersects the
N60E zone at the site. The bedrock aqui-
fer Is directly overlain by Pleistocene-age
sands and gravels. These sediments are
overlain  by low-permeability marine  clay
and  lodgement  till. It is  estimated  that
20%  of the water produced from the bed-
rock  aquifer is derived from overburden
sediments in the watershed area.
  Four overburden and bedrock well pairs
constitute the present monitoring network
for the test well.  Two well pairs lie along
the N60E faulted contact zone, and two
well  pairs  lie along the perpendicular
N30W trend. The test well and four of
five bedrock wells airlift in excess of 150
gal/min.  Few contaminant  threats exist
near the site. Baseline sampling indicates
that minor, elevated levels of iron, manga-
nese, and radon pose the only water qual-
ity problems at present.
  Test drilling and borehole surveys (cali-
per,  video camera,  acoustic televiewer,
thermal-pulse  flowmeter, and  hydro-
physical  logging) indicate that fracturing
and groundwater flow are highly discrete.
Flow occurs at  isolated, definable depths
rather than uniformly along the length of
the borehole. Hydrophysical logging indi-
cates that the borehole water is distinctly
layered with respect  to the fluid electrical
conductivity  parameter.  Most  borehole
water is produced by  moderately to steeply
dipping fractures and fracture zones that
intersect the wells.
  Aquifer testing and dye-trace results in-
dicate that the  N30W and N60E direc-
tions have higher aquifer transmissivities
relative to the surrounding bedrock matrix.
Drawdown contours  are elongate about
the N30W well  alignment, suggesting pre-
ferred flow in this direction. Dye-trace  re-
sults indicate more rapid travel of injected
dye  along the  N30W  direction than the
N60E direction.  Dye traveled  152 ft  in
130  minutes (the time of first arrival of the
dye) from injection in a bedrock monitor-
ing well along the N30W trend to the test
well, which was pumped at 200 gal/min.
This represents a velocity of  1,680 ft/d.
Dye injected in  a bedrock monitoring well
located 596 ft  from  the test well arrived
there in 148Siours, indicating a velocity of
96 ft/d along the N60E direction.
   Flowmeter and acoustic televiewer sur-
veys  indicate  that   a  moderately
west-dipping fracture zone provides inter-
connection between the test well and bed-
rock well R2 along the N30W trend. Lack-
ing discrete flow information beyond the
test well and well R2, statistical fracture
descriptions become good approximations
of flowpaths  at increasing distances from
the  site. Therefore, prominent fracture
peaks along the N5-10W  and  N60E
trends represent the most probable flow
directions within the  bedrock fracture sys-
tem at Blackwater Brook. The N60E trend
is substantiated by  the  existence of the
faulted, fractured contact zone along this
strike. Evidence to suggest preferred flow
along the N5-10W direction is structural
and  hydrogeologic. Structural control is
inferred by strong expression of the linea-
ment on several platforms of photography
and in outcrop fracture trends. Enhanced
transmissivity along the N30W direction
is  attributed to the proximity  and similar
orientation of the N5-10W fracture zone.
  A  quadratic equation is derived  from
accepted hydrogeologic  relationships
(Darcy's Law and the Thiem equation). In
this equation, groundwater travel time (de-
termined using the time of first  arrival of
dye at the test well) is directly proportional
to the square  root of distance  from the
test well.  Constants of proportionality for
the quadratic relationship are calculated
for the N30W and the N60E directions
based on dye-trace velocities. Distances
for the 200-day and 1,000-day TOT thresh-
olds are then calculated for the two frac-
ture zone  directions: N5-10W and N60E.
  Three wellhead protection zones are
delineated within the recharge area for
the test well using a variety of criteria and
methods.  Zone  I  is the state-mandated
400-foot sanitary  radius.  Zone IIA con-
sists of two 1,000-foot-wide "arms" along
the N5-10W and N60E directions, ex-
tending to the  200-day  TOT distances.
Zone IIB is the area within a smooth curve
connecting the outer boundaries of Zone
IIA, producing an oval shape. Zone III is
the  upgradient area  contributing to the
1,000-day TOT distance modified by hy-
drogeologic features. Recommended regu-
lation  of  the wellhead  protection zones
varies from complete  control  and restric-
tion of activities in Zone I to public educa-
tion  in Zone III.
   A major component of wellhead protec-
tion  program management is  long-term
groundwater monitoring.  Under present
conditions, monitoring of the test well and
existing monitoring wells will focus on a
moderate effort to assess  ambient water
quality and physical parameters. After the
production well is developed, the monitor-
ing frequency and list of monitoring pa-
rameters increases. Proposed frequencies,
parameters, and  new sites for monitoring
derive from technical and management
goals. Action levels are proposed to trig-
ger contingency responses.
                                                                       -&U.S. GOVERNMENT PRINTING OFFICE: 1993 - 7504711/80082


   Bath A. Moore iswith Lockheed Environmental Systems & Technologies Company,
     Las Vegas, NV 89119.
   Steven P. Gardner Is the EPA Project Officer (see below).
   The complete report, entitled "Case Studies in Wellhead Protection Area Delineation
     and Monitoring," (Order No. PB93-213510AS; Cost: $61.00, subject to change)
     will be available only from:
          National Technical Information Service
          5285 Port Royal Road
          Springfield, VA22161
          Telephone: 703-487-4650
   The EPA Project Officer can be contacted at:
          Environmental Monitoring Systems Laboratory
          U.S. Environmental Protection Agency
          Las Vegas, NV 89193-3478
United States
Environmental Protection
Centerfor Environmental Researchlnformation
Cincinnati, OH 45268

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