HYDROGEOLOGIC REPORT

SHELLER-GLOBE CORPORATION LANDFILL KEOKUK, IOWA

EPA Site ID# IAD980630750

EPA Contract No.: 68-W9-0006 Work Assignment No.: C07009

EPA Work Assignment Manager: Anne Olberding Controller Project Manager: John H. Parks

prc

30324997

Superfund

PRC Environmental Management, Inc.

TABLE OF CONTENTS

Section Page

1.0 EXECUTIVE SUMMARY................................................................................................. . 1

2.0 INTRODUCTION.................................................................................................................... 1

3.0 BACKGROUND...................................................................................................................... 2

3.1 LOCATION....................................................................................... 2

3.1.1 Study Area...................................................................................................... 23.1.2 Site Location.................................................................................................... 23.1.3 Site Description.............................. 2

3.2 SITE HISTORY.......................................................................................................... 4

4.0 INFORMATION RESOURCES .................. 4

4.1 GENERAL REFERENCE .......................... 44.2 PUBLISHED BULLETINS AND ARTICLES......................................................... 54.3 TECHNICAL REPORTS .......................................................................................... 5

5.0 GEOLOGY................................................................................................................................ 5

5.1 REGIONAL GEOLOGY............................................................................................. 5

5.1.1 Bedrock ............................ 65.1.2 Fracture Trace Analysis.............................................................................. 105.1.3 Fluvial Deposits ........... 145.1.4 Soil.................................................................................................................. 14

6.0 HYDROLOGY ............................ 16

6.1 PRECIPITATION ...................................................................................................... 166.2 SURFACE WATER........................................................ 166.3 AQUIFER CHARACTERISTICS .......................................................................... 176.4 GROUNDWATER FLOW................................................................ 186.5 CONTAMINANT TRANSPORT..................................................................... 19

7.0 CONCLUSIONS ................................................... 20

8.0 BIBLIOGRAPHY ................................................................................................................. 21

LIST OF FIGURES

Figure Page

3-1 Site Location Map............................................................................................................. 35-1 Gordon Paleo Channel Location Map .................................................................................... 75-2 Geological Cross Section in Lee County ............................................................ 85-3 Stratigraphic Column . . . ......................................................................................................... 95-4 Fracture Trace Concept............................................................................................. 125-5 Keokuk Area Fracture Trace Map ................................................................ 135-6 Typical Soils Diagram ........................................................................................................... 15

1.0 EXECUTIVE SUMMARY

The U.S. Environmental Protection Agency (EPA) has tasked PRC Environmental

Management, Inc. (PRC), to evaluate the possible interconnection of the aquifers below the

former Shelier-Globe landfill in Lee County, Iowa. The site is located approximately 1-1/2 miles

east of the Mississippi River and 3 miles north of the city of Keokuk, Iowa.

Based on a review of existing data on the hydrogeology and setting of the Shelier-Globe

landfill site, PRC believes that the surface hydrologic unit and the underlying Mississippian

aquifer are hydraulically interconnected. Studies by the U.S. Geological Survey and the Iowa

Geological Survey both state that the recharge of the Mississippian aquifer in this region is

through the infiltration of meteoric water. The area surrounding the site has completed wells in

assorted aquifers, all of which are primarily recharged through meteoric water infiltration. This

factor alone suggests the interconnection. When the additional factors are considered, the

possibility of isolating the upper aquifer from the lower aquifers becomes even more remote.

The highly eroded bedrock escarpment abutted with alluvial sands and gravels on the east, and

the glacial outwash materials on the west, both suggest interconnection since there is no barrier to

prevent the migration of water directly into the Mississippian aquifer.

The hazardous ranking system (HRS) rule requires that aquifers be distinct and

continuously separated throughout the 3 mile radius of the site. Within 2 miles of the site,

drinking water wells withdraw water from various aquifers. The glacial drift, St. Louis

Formation, and the Burlington-Keokuk Formation, all produce water that is used for human

consumption. With erosional and depositional forces having a wide variety of impacts, the

interconnection between aquifers is certain because the barriers between aquifers have been

eliminated. The exact boundaries of these aquifers and aquitards have not be determined,

horizontally or vertically, in the study area.

Analytical testing of the groundwater in the lower aquifer (Burlington-Keokuk

Formation) reveals elevated levels of lead and zinc. These metals are detected in high levels in

on-site soils. Other completed local wells in the same formation do not show similar metal

contamination. The metal concentrations have gradually increased the more the on-site well has

been used. These increases are probably due to the well drawing in the contamination from the

area of the aquifer where the contaminant plumb descends into the lower aquifer.

1

2.0 INTRODUCTION

PRC received Work Assignment No. C07009 under EPA Contract No. 68-W9-006 (TES 9)

to provide general negotiation support at the Sheljer-Globe Corporation disposal site near

Keokuk, Iowa. As part of this support, PRC was tasked to prepare a ground water position

paper.The position paper will summarize the hydrogeologic and geologic information available

on the Sheller-Globe site and present a defensible conclusion on the degree of interconnection

between the aquifers beneath the site.

3.0 BACKGROUND

3.1 LOCATION

The following subsections describe the Sheller-Globe study area, location, site description,

and history.

3.1.1 Study Area

The study area is comprised of portions of the Nauvoo, Keokuk, Niota, and Hamilton 7-

1/2-minute-quadrangle, U.S. Geological Survey topographic maps, all photo revised in 1975. The

term "study area" as used in this report includes all of the features within a 4-mile-radius of the

site. This will assure that the 3-mile-radius for HRS consideration is included. (40 CFR Part

300, Appendix A). The aerial extent of the study area is shown in the HRS package and is

approximately 50-square-miles.

3.1.2 Site Location

The former Sheller-Globe Corporation landfill is located approximately 4 miles north of

Keokuk, Iowa, about 2 miles east of Highway 218 on Airport Road (see Figure 3-1). The

approximate legal description of the site is the SW 1/4, SW 1/4, SW 1/4, Section 35, Township 66

North, Range 5 West, Lee County, Iowa (USGS. 1975).

2

MAP LOCATION SCALE 1:24000

0 .5 1 MILE

1 KILOMETER

GRIMES PROPERTY KEOKUK, IOWA

WASTE SITE TRACKING NO.: IA0133 ECOLOGY AND ENVIRONMENT FIT, JAN. 1BMPREPARED BY: ED HUBERT SOURCE: U3QS 7.5' KEOKUK, IA QUAD. 1B75

FIGURE 3-1: SITE LOCATION MAP

3.1.3 Site Description

The former Sheller-Globe landfill occupies approximately 5 acres in a heavily-wooded,

rural area. The site is located in an upland area, bordered on the south by Airport Road, and on

the west by Grimes Road. On the north and east, the site slopes steeply down to two intermittent

streams, approximately 50 feet below the top of the hill. These streams intersect north of the

site, and flow northeast into Lamalees Creek, approximately one mile from the site (see Figure 3-

1). .

The upland portion of the site is relatively level, and has been cleared and planted with

grass. The hillsides and the areas along both Grimes and Airport Roads remain heavily wooded.

Considerable waste material is exposed on the east-facing hillside and along the stream east of the

site. Waste material also is visible in the woods between the Grimes’ yard and Airport Road, in

the southern portion of the site. Waste material consists primarily of scrap rubber stripping.

However, 14 intact and 38 damaged, rusty drums are exposed on the surface (E&E/FIT, 1988).

A few of the exposed drums are relatively sound. Most of the damaged drums are empty, though

a few contain scrap rubber.

3.2 SITE HISTORY

From 1947 to 1972, Sheller-Globe used the site for open burning of solvents and

disposing of industrial waste materials (Woodward-Clyde, 1989). Waste liquids and sludges were

deposited in an open ravine without a liner or diversion system. Wastes also included

approximately 250 exposed and buried drums. The property was purchased by David Grimes in

1973. He and his family reside on-site. The Grimes’ obtain drinking water from an on-site,

300-foot well. Approximately 1,125 residents in the area obtain their drinking water from wells

completed in the shallow aquifers around the site (E&E/FIT, 1988).

Wastes and contaminants known to be present at the Sheller-Globe Corporation disposal

site include: scrap rubber stripping, polyurethane foam, paint sludges containing heavy metals,

methyl ethyl ketone, benzene, toluene, bis (2-ethy hexyl)-phthalate, methylene chloride, and

other miscellaneous solvents (E&E/FIT, 1988).

On-site soil samples have been found to contain elevated levels of 14 metals: arsenic,

barium, cadmium, calcium, chromium, cobalt, copper, lead, magnesium, mercury, selenium, zinc,

nickel, and silver. Toluene, methyl ethyl ketone, benzene, two phthalate compounds, and various

PAH compounds have also been detected in on-site soil samples (E&E/FIT,1988). Elevated levels

of toluene, arsenic, chromium, lead, zinc, and cadmium, have been found in on-site groundwater.

4

The Sheller-Globe Corporation disposal site has recently been proposed for the National

Priorities List by the U. S. Environmental Protection Agency.

4.0 INFORMATION RESOURCES

The information discussed in this report has been compiled from four sources: reference

text books, published bulletins and articles, technical reports, and EPA site investigation and

hazardous ranking system reports. A brief description of these resources is provided in the

following sections.

4.1 GENERAL REFERENCE

The general references used for this report consist of Groundwater (Freeze and Cherry,

1979); Groundwater and Wells (Driscol, 1986); and Soil Survey of Lee Countv. Iowa (U.S.

Department of Agriculture, Soil Conservation Service, 1979).

4.2 PUBLISHED BULLETINS AND ARTICLES

Publications by the Iowa Geological Survey on the study area include: Geology of Lee

Countv (1893); Water Resources of Southeast Iowa (1971); Mississippian Aouifer of Iowa (1973);

Underground Waters of the Southeastern District Lee Countv (1912); and Pre-Wisconsinan

Stratigraphy in Southeastern Iowa (1980).

Publications by the U.S. Geological Survey in the study area include: National Water

Summarv-Iowa (1984); and Log Data from IGS and USGS Cooperative Geologic Files (1988).

4.3 TECHNICAL REPORTS

The final report on the follow-up investigation. Grimes Property site, Keokuk, Iowa,

prepared by E&E/FIT, dated July 13, 1988, provided information on site-specific data and

general regional information. This report was a major investigative effort by EPA contractors oh

the Sheller-Globe site and detailed much of the background information used in this report.

Comments on Proposed Addition of the Sheller-Globe Corporation Site. Keokuk. Iowa, to

the National Priorities List Hazard Ranking Svstem. dated June 29, 1989, prepared by

Woodward-Clyde Consultants, also was reviewed for pertinent information.

The unpublished comments of Bob Mvers, EPA HQ, Washington, D.C., on Unresolved

Issues: Aquifers of Concern was reviewed.

The EPA-HRS package containing extensive bibliographic information also was reviewed

for pertinent data to be incorporated into this report.

5

)

5.0 GEOLOGY

5.1 REGIONAL GEOLOGY

The study area lies on an upland area of Devonian and Mississippian aged bedrock

between the Mississippi River Valley and the Gordon Paleo Channel. The bedrock of the area

has undergone extensive erosion over the last 250 million years since they were deposited. The

past erosion of the ancestral Mississippi River has dissected the bedrock substantially. One mile

west of the site, the Gordon Paleo Channel has been eroded into the bedrock over 400 feet deep.

One mile east of the site, the present course of the Mississippi River has cut a channel

approximately 200 feet into the Mississippian bedrock.

The Devonian bedrock consists of 110 feet of cherty limestone with interbred siltstone

and 220 feet of shale with minor siltstone. The Mississippian bedrock consists of 400 feet of

dolomitic limestone with shale and siltstone. The area’s bedrock surface is highly weathered from

the long term effects of river erosion and channel movement. Figure 5-1 is a bedrock contour

map of the region showing the location of the Gordon Paleo Channel and the Mississippi River

(see also the cross section of the area from the Geological Report on Lee County in Figure 5-2).

The area is covered unconformably by pre-lllinoisan till. This till is composed of multiple basal

tills and inter-till stratified sediments. This till is covered by a thin mantle of windblown silt

deposits (loess). Figure 5-3 is a generalized stratigraphic column showing the sequence generally

encountered in the vicinity of the study area (E&E/FIT, 1988).

5.1.1 Bedrock

Log wells in the study area indicate that the area has underlying Devonian, Mississippian,

and Quaternary-aged unconsolidated deposits to a depth of approximately 700 feet.

The Devonian rock units are approximately 330 feet thick. The lower 110 feet consist of

the Wapsipinicon and Cedar Valley Formations. These formations are described as cherty

limestone with inter-bedded siltstone. The upper 220 feet is the Yellow-Spring Group consisting

of the Lime Creek, Sheffield, Maple Mills, and English River Formations. These formations are

made up of shale with minor siltstones.

6

EXPLANATION

■ soo-Bedrock contours

Show altitude of bedrock surface. Dashed where approximately located. Contour in­terval is 50 feet. Datum is mean sea ievei

GRIMES PROPERTY KEOKUK, IOWA

SCALE 2

MILES

WASTE SITE TRACKING NO.: I A013 3 PREPARED BY: C. WILLIAMS

ECOLOGY & ENVIRONMENT FIT MAR. 1988SOURCE

FIGURE 5-1: GORDON PALEO CHANNEL LOCATION MAP

7

SECTION FROM SONORA TO ARGYLE.

FIGURE 5-2: GEOLOGICAL CROSS SECTION IN LEE COUNTY

PRC-EMI

V’j'j'r*

SECTION GENERAL LITHOLOGY_g“ Glacial till, fluvial dapoaita IvN %«w«i^jW8mk/^WV>W

220

HYDROLOGY KEY

ST. LOUIS FM.Limestone - arenaceous.

WARSAW FM.

Shale with Interbec charty llmastona

BURLINGTON-KEOKUK FM.

Llmastona - dolomltie, charty

PROSPECT FM.

Siltstona

McCRANEY FM.

Llmastona - dolomltie, charty

YELLOW SPRING GROUP

Shale with minor siltstona

WAPSIPINICON &CEDAR VALLEY FMS.

Limestone charty with interbaddad siltstona

WI SCON SAN FM.

Llmastona - charty

Aquifer

Aquifer

Aquitard

MajorAquifer

Aquitard

Aquifer

RegionalAquitard

Aquifer

Aquifer

Oof omit*

□’ i »

8*00*0 Chart

□ no□ □ □Quvttit*

C*fOan*u*e Shaf*

Ar*rv

UVJB BB

mi a &*v*t

GRIMES PROPERTY KEOKUK, IOWA

rOVertical Scale (feat)

WASTE SITE TRACKING NO.: PREPARED BY: C. WILUAM8

ECOLOGY & ENVIRONMENT FIT MAR. 1988

FIGURE 5-3: STRATIGRAPHIC COLUMN

9

The Mississippian-aged bedrock units are approximately 360 feet thick. In ascending

order, the Mississippian bedrock consists of (1) McCravey Formation, a dolomitic, chert

limestone, 65 feet thick, (2) the Prospect Formation, a 40-foot-thick siltstone, (3) the Burlington-

Keokuk Formation, a dolomitic, cherty limestone, 165-to 200-feet thick. The Burlington-

Keokuk Formation is followed by the Warsaw Formation, which consists of shale with

interbedded cherty limestone, 20-to 60-feet thick. The Warsaw Formation has overlying

remnants of the St. Louis Formation, an arenaceous limestone up to 40 feet thick. The St. Louis

Formation is the uppermost bedrock and has been exposed to the extensive erosion.

The rock sequence is covered by quaternary glacial basil till, fluvial deposits, and loess.

These deposits unconformably overlie the eroded Devonian and Mississippian bedrock surfaces.

The presence of the Gordon Paleo Channel on the west and the current Mississippi River

channel to the east, has a direct impact on the configuration of the area bedrock. These channels

are both within two miles of the site. There is extensive erosion of the St. Louis, Warsaw, and

the Burlington-Keokuk Formations at the edges of the bedrock escarpment between the two

erosional channels. Because of these erosional features, the sequence of bedrock below the site is

in direct contact with Pleistocene unconsolidated materials. The erosion of the local bedrock has

progressed entirely through the Mississippian strata in the Gordon Paleo Channel to the west,

exposing the Devonian-aged Yellow Springs Group in the bottom of the channel. On the east

side of the site in the Mississippi River, channel erosion has progressed through the St. Louis and

Warsaw Formations, approximately through half of the sequence. The Burlington-Keokuk

Formation is exposed beneath the Mississippi River valley. Figure 5-2 was published by the

Iowa Geologic Survey in 1893, and presents a cross section of Lee County, east to west, not far

from the site. This cross section shows the relationship of the two channels to the site.

5.1.2 Fracture Trace Analysis

Groundwater can migrate through bedrock and soils in both primary hydraulic

conductivity or secondary hydraulic conductivity. Primary hydraulic conductivity is the

interconnected void space in sediment or rock that was present at the time of deposition.

Secondary hydraulic conductivity occurs through the interconnected void spaces that happen after

deposition and lithification.

The bedrock of the study area is primarily dolomitic limestone and suggests alteration and

the formation of fractures. The dolomite is secondary in origin, formed by geochemical

alteration of calcite. This mineralogical transformation causes an increase in both primary and

secondary hydraulic conductivity because the crystal lattice of dolomite occupies approximately

13 percent less space than that of calcite (Freeze and Cherry, 1979).

The presence of fractures in the area bedrock has been noted in many publications. The

St. Louis and Burlington-Keokuk Formations rely on the fractures to produce sufficient water to

10

be considered aquifers. This suggests the presence of secondary hydraulic conductivity features,

such as joint fissures and solution cavities. The formations of the area are broken by fractures

and crevices extending for considerable distances that are partially interconnected (Horick and

Steinhilber, 1973).

Due to the linear nature of secondary hydraulic conductivity features, a major portion of

the ground water flows in an area that may be concentrated in one or more fracture zones.

Fracture traces in bedrock can often be seen on aerial photographs and topographic maps as

lineaments or lines that are structurally controlled. The lineaments are distinguishable as a linear

trend in soil color, vegetation alignment, straight stream sections, topographic expressions

(straight contour lines), or sink hole alignments. In order to determine if large scale fracturing is

present in the study area, a detailed fracture trace analysis using aerial stereo pair photographs is

needed. The topographic maps of the study area do reveal many fracture traces that connect the

ground water regimes. Figure 5-4 is a fracture trace concept diagram showing the hypothetical

appearance of fractured bedrock in the subsurface (Lattman and Parizek, 1964).

Figure 5-5 is a topographical map of the study area with some interpreted fracture traces.

The map shows that there are numerous linear features in the study area.

5.1.3 Fluvial Deposits

The Mississippi River valley is a partially-filled trough, incised into the surrounding

bedrock. The grain size of the sediments typically becomes finer upward through the sequence.

The thickness of the alluvium is controlled by irregularities in the bedrock surface. Regionally,

the maximum thickness of the alluvium is up to 200 feet (Keys, 1895).

The exploration of the Gordon Paleo channel has been limited. Based on available

information, the lower portion of this trough has traces of sand and gravel that are remnants of a

pre-glacial river deposits. These inter-bedded sands and gravels are an important water supply

locally. This channel usually has one or two sand layers that will yield enough water for domestic

needs (Coble, 1971). Obviously, there is sufficient water percolating through the glacial clay till

to recharge these sand layers. Similarly, the bedrock in contact with these deposits will be

recharged through this process.

11

FIGURE 5-4: FRACTURE TRACE CQNCEPT

12 PROEM!

FIGURE 5-5: KEOKUK AREA FRACTURE TRACE MAPPRC-EMI

13

5.1.4 Soil

The soils within the study area consist of glacial, eolian, and colluvial and alluvial soils of

Pleistocene to Holocene age, and residual soils formed by the in situ weathering of the bedrock.

The site area soils consist of four major types in descending order: the Clinton silt loam,

the Weller silt loam series, the Lindley loam, and the Keswick series. The soils are distributed

similar to Figure 5-6.

The Clinton silt loam is formed on upper side slopes and high benches along major

streams and rivers. It is found in leached loess, 6-to 10-feet thick.

The Weller silt loam series consists of moderately well drained soils on convex summits

and side slopes of upland ridges. These soils formed in leached loess, 4-to 8-feet thick.

The Lindley loam consists of well drained soils on the rounded ends of narrow ridge tops

and irregular, complex, side slopes on uplands.

The Keswick series consist of moderately well drained soils on narrow ridge tops and

convey short side slopes. These soils developed in previously weathered glacial till (USDA, 1979).

All of these soil types are considered well drained because of the water’s ability to

migrate through the material (USDA, 1979). The till in the area has been studied in detail, and

the Iowa Geologic Survey Publication on Illinoisan and pre-Illinoisan stratigraphy of southeast

Iowa and adjacent Illinois has mapped the tills of the area. The till has been identified as the

Hickory Hills till, member of the Wolf Creek Formation tills and is in the pre-Illinoisan;

Yarmouth stage. The Hickory Hills till member is relatively sandy and has sand fractions of 45-

to 50-percent through the study area (Hallberg, 1980).

14

REFERENCE: USDA.1979

5-6 TYPICAL SOILS DIAGRAM

PRC-EMI

i s

6.0 HYDROLOGY

6.1 PRECIPITATION

The normal average precipitation for Keokuk, Iowa, is approximately 34.6 inches per year

and the evaporation rate is 23 inches per year; therefore, the net .precipitation is 11.6 inches per

year. Seventy-five percent of the annual precipitation occurs during the 6 month period from

April to September. June is usually the wettest month, and dry periods are most likely in July

(USDA, 1979). The I-year, 24-hour, precipitation event is approximately 2.75 inches (USEPA,

1982). Ten to 20 percent of the precipitation infiltrates into the groundwater system and is the

primary source of recharging for the aquifers in the region (Karsten and Burkart, 1985).

6.2 SURFACE WATER

The study area lies in the Mississippi River drainage area. The surface water within the

study area flows either east to the Mississippi or south to the Des Moines River. The ground

elevation of the site is approximately 640 feet above sea level, while the elevation of the

Mississippi River, approximately 1-1/2 miles east, is 518 feet above sea level (USGS, 1975).

6.3 AQUIFER CHARACTERISTICS

The depth to the water table is approximately 8 feet below ground level in the valley

(E&E/FIT, 1988). The water table elevation will fluctuate in response to precipitation and

climatic conditions.

Ground water within the study area is produced from a variety of sources. The alluvial

sands and gravels along the Mississippi River produce large amounts of drinking water. Stratified

sands and gravels in the Gordon Paleo channel produce water along with bedrock wells drilled

into the St. Louis, Keokuk, and Burlington Formations.

The deposits possibly impacted by the study area can be divided into seven general

hydrogeologic units: the glacial deposits aquifer; the alluvial aquifers; the St. Louis Formation; the

Warsaw Formation; the Burlington-Keokuk Formation; the Prospect Formation; and the

McCraney Formation (see Figure 5-3).

The glacial deposits consist of sand, gravel, silt and clay, and have a variety water­

bearing capacities. Yields range from a few gallons-per-minute to large yields of 50-to 100-

gallons- per-minute (Gordon, 1980).

16

The alluvial aquifers consist of sand, gravel, silt, and clay, with yields from 25-to 100-

gallons-per-minute. This aquifer is present along the Mississippi River and is recharged rapidly

by the infiltration of surface waters. This alluvium has many high production wells in the region

(Gordon, 1980).

In the Mississippian bedrock, specific capacity of most wells in the area is much less than

1 gallon per minute per foot of drawdown (9 pm/ft). Yields are generally 3-to 10-gallons-per-

minute (gpm) in the St. Louis Formation. Yields in the Burlington-Keokuk and McCraney

Formations are reported at 10-to 30-gpm. Variations in production are directly related to the

degree of interconnection between the well location and the surrounding aquifers (Horick and

• Steinhilber, 1973).

These aquifers are separated by bedrock units of lower hydraulic conductivity; the

Warsaw Formation and the Prospect Formation are considered aquitards. Because of extensive

fracturing and erosion, these beds are not continuous over the study area. The percolation of

groundwater through portions of these beds may be slowed, but it is not prevented from

migrating. The migration of water through these low conductivity beds would therefore

eliminate them from being considered aquicludes.

Ordinarily, a clay or shale formation is nearly impermeable and is called an aquiclude,

i.e., a formation through which virtually no water moves. Formations that do yield some water,

but usually not enough to meet even modest demands, are called aquitards. In reality, almost all

formations will yield some water, and therefore are classified as either aquifers or aquitards. In

water-poor areas, a formation producing small quantities of water may be called an aquifer,

whereas the same formation in a water-rich area would be an aquitard (Driscoll, 1986).

6.4 GROUNDWATER FLOW

Regional groundwater flow in the upper elevations is generally toward the Mississippi

River. The deeper aquifers (Devonian-and Ordovician-aged) generally flow toward the west

following the regional dip of the bedrock.

The migration of water through the subsurface is not controlled by the specific matrix

permeability, but with a two-domain flow concept for soil water flow. Water flow utilizing a

two-domain system could allow rapid vertical and horizontal transport of fluids.

The two-domain soil water flow system is composed of a rapid flux, flowing through

fractures or channels; and a slow flow, flowing through very small pores created by soil particle

contacts. This phenomenon is the same as that of the Burlington-Keokuk limestone below the

site. The rapid water flow and the slow flow both occur in the macropores.

Recent research has shown that the predictive models of contaminant migration have not

correlated between predicted and observed containment migration. The presence of macropores

17

has allowed the migration of material deep into the subsurface. The transport of particles

through macropores also allows for the "tunneling out" of pores to increase size and velocities.

The typical permeability test conducted on soils measures only the micropore flow and

does not address the possibility of a macropore adjacent to the sample point. This factor can lead

to the conclusion that materials will not migrate through a soil when in actuality the flow is many

orders of magnitude greater. Likewise the migration of water within the bed rock is primarily

controlled by joints and fractures. The water is available in irregularly spaced and unpredictable

crevices and passages dissolved along bedding planes and vertical fractures by percolating

groundwater.

The groundwater flow system in the study area is very complex with multiple flow

pattern possibilities. The limestone and shale bedrock formations are recharged from

precipitation that infiltrates through the glacial till and loess deposits. The water then begins to

percolate vertically through the bedrock via secondary hydraulic conductivity features such as

joints, faults, fractures, or solution channels (macropores). To a minor extent, water can flow

vertically via existing primary hydraulic conductivity. Vertical movement of groundwater is

complicated by the presence of less permeable shale units. Typically, groundwater may flow

horizontally along bedding planes forming solution channels and continue vertically at the next

open permeable fracture zone. A portion of the bedrock groundwater may discharge to the

surface via springs and seep east of the site in the lower elevation areas. The remainder of the

bedrock groundwater may ultimately discharge into the Mississippi River alluvium, the Gordon

Paleo channel deposits or into the Mississippi River itself. The remaining portion will be stored

in aquifers. Pumping wells may influence the flow patterns by withdrawing water thus altering

normal flow gradients and possibly even reversing them.

6.5 CONTAMINANT TRANSPORT

A potential pollution hazard to the Mississippian aquifer exists in the outcrop area, which

includes the study area. The aquifer in the outcrop area is recharged through the glacial drift;

therefore, any deleterious materials introduced into the surficial flow system eventually will reach

the Mississippian aquifer. Deleterious materials may be in the form of farm chemicals that are

over-applied and infiltrate the ground or may be downward percolating leachate produced from

waste-disposal sites (Horick and Steinhilber. 1973).

The analytical results of several sampling sequences are important to the establishment of

the interconnection between the upper and lower aquifers. The surface soils have been sampled

and analyzed, and found to contain a wide variety of contaminants most notable of which are

lead and zinc. These metals are common constituents of paint wastes deposited at the site

(E&E/FIT, 1988).

18

Shallow monitoring wells installed at the site have detected significant levels of arsenic,

chromium, nickel, lead, and zinc (E&E/FIT, 1988).

The Grimes’ well has been sampled three times (E&E/FIT, 1988). The initial sampling

was in October, 1980, by Sheller-Globe. At that time the well was newly drilled . No

contaminants were detected in that sampling (EPA, 1983). The well was sampled again in March

of 1986, when 3700 ug/I of zinc and 55 ug/1 of lead were detected (E&E/FIT, 1988). The final

sampling was conducted in December 1987. The samples showed 6600 ug/1 zinc and 35 ug/1 lead.

Background wells completed upgradient and in the same formation have not contained detectable

amounts of these metals (E&E/FIT, 1988).

19

7.0 CONCLUSIONS

Based on the information presented in this report, the separation of the aquifers in the

three-mile radius within the site has not been clearly defined. The area consists of a complex

aquifer-aquitard system of heterogeneous and anisotropic formations and is much more difficult

to define.

The 34 inches of precipitation falling onto the land surface in and around the site is the

source of recharging for the surface aquifers, the St. Louis and Burlington-Keokuk Formations

below the site. Ten-to 20-percent of that precipitation is the primary source of recharging for all

the aquifers in Iowa. This water infiltrates through primary hydraulic conductivity and through

secondary hydraulic conductivity into the aquifers of the region. The secondary hydraulic

conductivity can be responsible for a majority of the transport of groundwater. The fracturing

of the bedrock gives preferential flow paths for rapid transport of both water and contaminants

into aquifers. The aquitards of the region are affected by the fracturing along with erosional

processes to limit the true nature of an aquitard. The aquitards of the area do not function as

aquicludes and therefore allow migration of water into the aquifers below them.

The migration of surface water into the subsurface allows for the transport of

contaminants into the aquifers along with the flow of water. The contaminant transport process

places the entire Mississippian aquifer at risk of being contaminated. With the rapid flow of

water, the contaminants can be carried deep into the aquifer and spread over large areas.

Analytical results from wells on-site have documented that heavy metals have been

released into the groundwater system. The water from the Grimes’ well completed in the lower

Mississippian aquifer has been analyzed and has shown an increase in heavy metal content. This

report documents the presence of interconnections between the upper water table and lower

Mississippian aquifers below the site.

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8.0 BIBLIOGRAPHY

Driscol, Fletcher G., 1986, Groundwater and Wells, Johnson Division, St. Paul, Minnesota.

Ecology & Environment/FIT, 1986, Site Inspection of the Grimes Property Site.

Freeze, Allen R., and John A. Cherry, 1979, Ground Water, Prentice-Hall, Inc., Englewood Cliffs, N.J.

Hallberg, George R., 1980, Pre-Wisconsinan Stratigraphy in Southwest Iowa, Iowa Geologic Survey Technical Information, Series No. 11.

Hansen, Robert E., 1973, Bedrock Topography of Southeast Iowa, U.S. Geological Survey, Washington, D.C.

Horick, P.J., and W.L. Steinhilber, 1973, Mississippian Aquifer of Iowa, Iowa Geological Survey, Miscellaneous Map Series 3.

Iowa Geologic Survey, 1971, Water Resources of Southeast Iowa, Water Atlas No. 4.

Karsten, Richard, and Michael Burkart, 1984, National Water Summary-Iowa, U.S. Geological Survey, Reston, Virginia.

Keyes, Charles R., 1895, Geology of Lee County, Iowa Geological Survey, Vol. Ill,Second Annual Report.

Lattman, L.H., and R.R. Parizek, 1964, Relationship Between Fracture Traces and theOccurrence of Groundwater in Carbonate Rocks, Journal of Hydrology, Volume 2.

Norton, W.H., 1912, Underground Waters of the Southeastern District: Lee County, Iowa Geologic Survey, Annual Reports, Volume XXI.

U.S. Department of Agriculture, 1979, Lee County Soil Survey, Soil Conservation Service.

U.S. Environmental Protection Agency, 1982, HRS User’s Manual.

U.S. Environmental Protection Agency, 1983, Potential Hazardous Waste Site.

U.S. Geological Survey, 1975, 7.5 Minute Topographic Map, Keokuk, Iowa Quadrangle, Washington, D.C.

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