EDER ASSOC PC - STUDY OF NATURAL ATTENUATION OF TCE IN ... · eder associates 1.0 INTRODUCTION 1.1 Study Objectives This report describes the natural attenuation trend of TCE in Plume

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STUDY OF THE NATURAL ATTENUATION

OF TCE IN PLUME 1-2

eder associatesenvironmental scientists and engineers

NATIONAL PRESTO INDUSTRIES, INC.

EAU CLAIRE, WISCONSIN

STUDY OF THE NATURAL ATTENUATIONOF TCE IN PLUME 1-2

PROJECT #497-8

FEBRUARY 1996

Office Location: Office Contact:EDER ASSOCIATES Leonard I. Eder, P.E.

480 Forest Avenue Mark RyvkinLocust Valley, New York 11560 Viktor Raykin

(516)671-8440

Offices in New York, Wisconsin, Michigan, Georgia, Florida, New Jersey and Massachusetts

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eder associatesenvironmental scientists and engineers

OFFICES:Locust Valley. NYMadison. WlAnn ArDor. MlAugusta. GAJacksonville. FLTrenton. NJTampa. FL

February 6, 1996File #497-8

Mr. Richard NaumanNational Presto Industries, Inc.3925 North Hastings WayEau Claire, Wisconsin 54703

Re: Study of the Natural Attenuation of TCE in Plume 1-2

Dear Rich:

I am enclosing a copy of the report "Study of the Natural Attenuation of TCE in Plume 1-2," as yourequested.

Please call me or Len if you have any questions.

Very truly yours,

EDER ASSOCIATES

Viktor RaykinSenior Project Hydrogeologist, CGWP

VR/mw

Enclosure

cc: w/enc L. Bochert, Esq.J. Bartl, Esq.D. KugleL. EderW. Warren.

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480 FOREST AVE., P. 0. BOX 707. LOCUST VALLEY, NEW YORK 11560-0707 • (516) 671-8440 • FAX (516) 671-3349

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CONTENTS

Page

LETTER OF TRANSMIT!AL

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Study Objectives ...............................'.................. I

1.2 Site Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.0 SOLUTE TRANSPORT OF VOC IN GROUNDWATER ....................... 32.1 Mechanisms Affecting Solute Transport of VOCs in Groundwater . . . . . . . . . . . 32.2 TCE Solute Transport in Plume 1-2 at the NPI Site . . . . . . . . . . . . . . . . . . . . . . 7

3.0 NATURAL ATTENUATION RATE OF TCE IN PLUME 1-2 . . . . . . . . . . . . . . . . . . . 9

3.1 The TCE Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2 Trends in TCE Concentrations over Time in Monitoring Wells

Along the Plume Centerline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.2.1 Selected Wells Indicating Declining Trend . . . . . . . . . . . . . . . . . . . . . . . 103.2.2 Selected Wells Indicating No Trend . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.3 Trends in TCE Concentrations over Time in Wells at the ECMWF . . . . . . . . . . 123.4 Trends in TCE Concentrations over Time in Monitoring Wells

Along the Plume Edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.0 HISTORICAL AND PREDICTED TCE PLUME 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.1 Historical TCE Plumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.2 Predicted TCE Plumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.0 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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TABLES

No. Description

1 Dissolved Oxygen Concentrations in Selected Wells in Plume 1-2, January 9, 1996

2 TCE Concentrations in Monitoring Wells Along the Plume Centerline3 Estimated Time for TCE Concentrations to Decline Below the Enforcement Standard4 TCE Concentrations in Monitoring Wells Along the Plume Edges

FIGURES

No Description

1 Site Map With Monitoring Wells and TCE Isocontours in Plume 1-2, 1995

2 Site Map With Monitoring Wells and TCE Isocontours in Plume 1-2, 1992

3 TCE vs. Time Graph - Monitoring Well RW-2A

4 TCE vs. Time Graph - Monitoring Well RW-2B

5 TCE vs. Time Graph - Monitoring Well RW-2C6 TCE vs. Time Graph - Monitoring Well RW-3A7 TCE vs. Time Graph - Monitoring Well RW-3B8 TCE vs. Time Graph - Monitoring Well RW-3C9 TCE vs. Time Graph - Monitoring Well RW-1410 TCE vs. Time Graph - Monitoring Well RW-1511 TCE vs. Time Graph - Monitoring Well RW-1612 TCE vs. Time Graph - Monitoring Well RW-16B

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FIGURES• Continued -

No Description

13 TCE vs. Time Graph - Monitoring Well RW-16C14 TCE vs. Time Graph - Monitoring Well RW-1715 TCE vs. Time Graph - Monitoring Well RW-1916 TCE vs. Time Graph - Monitoring Well RW-23

17 TCE vs. Time Graph - Monitoring Well MW-38A18 TCE vs. Time Graph - Monitoring Well MW-38B

19 TCE vs. Time Graph - Monitoring Well MW-38C

20 TCE vs. Time Graph - Monitoring Well MW-41A21 TCE vs. Time Graph - Monitoring Well MW-41B

22 TCE vs. Time Graph - Monitoring Well MW-43A23 TCE vs. Time Graph - Monitoring Well MW-43B24 TCE vs. Time Graph - Monitoring Well MW-44A25 TCE vs. Time Graph - Monitoring Well MW-44B26 TCE vs. Time Graph - Monitoring Well MW-45A

27 TCE vs. Time Graph - Monitoring Well MW-45B

28 TCE vs. Time Graph - Monitoring Well MW-45C29 TCE vs. Time Graph - Monitoring Well MW-46A


31 TCE vs. Time Graph - Monitoring Well MW-46C32 TCE vs. Time Graph - Monitoring Well MW-53A

33 TCE vs. Time Graph - Monitoring Well MW-53B34 TCE vs. Time Graph - Monitoring Well MW-55B35 TCE vs. Time Graph - Monitoring Well MW-55C

36 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-3A

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FIGURES

• Continued -

No Description

37 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-3B

38 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-3C

39 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-15

40 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-16B41 TCE vs. Time Graph With Best Fit Line - Monitoring Well RW-16C42 TCE vs. Time Graph With Best Fit Line - Monitoring Well MW-38B

43 TCE vs. Time Graph With Best Fit Line - Monitoring Well MW-43A

44 TCE vs. Time Graph With Best Fit Line - Monitoring Well MW-45C

45 TCE vs. Time Graph With Best Fit Line - Monitoring Well MW-53A46 TCE vs. Time Graph - ECMWF Production Well 1147 TCE vs. Time Graph - ECMWF Production Well 1548 TCE vs. Time Graph - ECMWF Production Well 1649 TCE vs. Time Graph - ECMWF Production Well 17

50 TCE vs. Time Graph - ECMWF Production Well 19

51 TCE vs. Time Graph - Monitoring Well RW-22

52 TCE vs. Time Graph - Monitoring Well MW-39A53 TCE vs. Time Graph - Monitoring Well MW-49A


55 TCE vs. Time Graph - Monitoring Well MW-69A56 3-D Conceptual Model of TCE Plume Based on 1985-1987 WESTON Data57 3-D Conceptual Model of TCE Plume Based on 1992 EDER Data58 3-D Conceptual Model of TCE Plume Based on 1995 EDER Data59 Predicted 3-D Model of TCE Plume in 15 Years

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1.0 INTRODUCTION

1.1 Study Objectives

This report describes the natural attenuation trend of TCE in Plume 1-2 using the current database.The natural attenuation analysis is based on the TCE data collected from 1985 through January 1996by Roy F Weston, Inc. (WESTON) and Eder Associates (EDER).

The objectives of this study are to determine the natural attenuation trend of trichioroethylene (TCE)in Plume 1-2 using the historical records of TCE analytical data and then to use that attenuation rateto assess the TCE concentrations expected to remain over time in the future.

1.2 Site Background

Plume 1-2 is a well-defined VOC plume that originates at the NPI site, extends westward throughan industrial park-airport area, and terminates at the north part of the Eau Claire Municipal Well Field(ECMWF), where groundwater is extracted and treated (Figure 1).

Plume 1 -2 moves through a sand and gravel aquifer in a buried valley system. Groundwater flowpaths are controlled by the location and orientation of the buried valley, which cuts deeply intothe sandstone and extends down to the underlying granite in places.

Groundwater flow in the northwest part of the NPI site is more complex because of the configurationof that part of the buried valley and because of a northwest-trending groundwater divide thatseparates the area into two groundwater basins. Groundwater west of the divide flows to theECMWF, and groundwater east of the divide flows north to Lake Hallie.

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A source characterization program found the following VOCs, which were detected in Plume 1-2:

TCE; tetrachloroethylene (PCE), 1,1,1-tetrachloroethane (1,1,1-TCA); 1,1- dichloroethane (1,1-

DCA), and 1,1-dichloroethene (1,1-DCE).

Recent groundwater sampling in monitoring wells in Plume 1 -2 showed that only TCE exceeds the

Wisconsin Enforcement Standard (ES) of 5 ug/1, which is the Federal Maximum Contaminant Limit

(MCL). The Wisconsin Preventive Action Limit (PAL) is generally five to ten times more stringent

than the enforcement standard. The PAL for TCE is 05 ug/1.

As a part of the Interim Remedial Action (IRA), extraction wells EW-1 and EW-2 (at the MelbyRoad Disposal Site) and extraction wells EW-3 and EW-4 (in the southwest portion of the property)started operating in early 1994 to eliminate source contributions of VOCs to groundwater from theNPI site. Groundwater is monitored quarterly to assure effective capture of the plumes in the sourceareas. The Melby Road Disposal Site will be capped, and the forge compound in Lagoon 1 has beenremoved.

EDER conducted a groundwater modeling study to estimate the remedial time frames under variouspumping scenarios to support a feasibility study (FS). The model predicted the aquifer restorationtime frames and included a retardation factor to account for contaminant adsorption. A retardationfactor of five was used in the model, assuming that five soil pore volume exchanges (flushes) wouldbe required to restore groundwater quality to the PALs or to the minimum levels that are technicallyand economically feasible. Assuming continuing pumping at the ECMWF and at the NPI site, the

model estimated the remedial time frame for Plume 1-2 at 160 years. This time frame represents the32- year travel time of the plume (one foot per day, average) multiplied by a factor of five (fiveflushes).

Other natural attenuation mechanisms that affect the transport of VOCs in the groundwater aredispersion, dilution, volatilization, chemical transformation, and biodegradation, all of which cansignificantly accelerate the natural decrease in VOC concentrations over time. These factors werenot used in the modeling study to assure a conservative model output.

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2.0 SOLUTE TRANSPORT OF VOC IN GROUNDWATER

2.1 Mechanisms Affecting Solute Transport of VOCs in Groundwater

Groundwater flow, characteristically laminar, occurs at low velocity without turbulence, and ischaracterized by parallel flow lines along a predictable path. This system description fits mostunconsolidated geological formations. Rock aquifers that allow flow only in fractures and beddingplanes also usually exhibit laminar flow, although the flow directions may be dictated by fracture

patterns. The flow system in the Eau Claire area includes geologic matrices of unconsolidatedalluvium and rock. Flow velocities in both media would be subject to laminar flow conditions.

When a solute moves in groundwater, it is dispersed both along and perpendicularly to the axis offlow, with the latter usually of greater magnitude than the former. The resultant dispersion patternhas a long axis in the directions of flow and is referred to as a plume.

Laminar flow prevents the solute from mixing with the groundwater and allows plumes to maintaintheir integrity over long distances. The solute is diluted as the plume migrates because dispersion isactually the intermingling of groundwater containing the solute with ambient groundwater at theplume's leading edge. On a microscale, contaminated water is moving into larger pores more rapidlythan into smaller pores, effecting a dilution with laminar flow even though there is no general mixingof the kind that occurs in surface water.

Organic compounds in groundwater have limited contact with the atmosphere, the potential forbiodegradation is lower than in shallow soil or surface water, and the temperature is relatively cooland even. These characteristics generally allow the contaminants to persist for relatively long periods- longer than would be the case in surface waters.

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The organic compounds in the plumes originating at the NPI site are dissolved in groundwater, andtheir concentrations are controlled by the amount of chemical originally available for dissolution andthe solubility of the individual chemical compounds. The dissolved chemicals are transported with

the groundwater flow.

This transport is not a simple migration pathway totally mimicking groundwater movement. Organiccompounds interact with geologic materials in the formation, most strongly with residual organicmatter (organic carbon). The interaction of solute chemicals with the geologic materials causespartitioning, which is the apportionment of the solute chemical between the solution and attraction(sorption) to the geologic substrate. Almost every organic solute has some attraction for geologicmaterials, and many tend to more closely associate with the geologic material than with thegroundwater, a tendency that increases with decreasing aqueous solubility. Organic substances thatare sorbed are removed from solution but may return to solution if conditions such as solutionconcentration change. This chemical reservoir slowly desorbs into the groundwater and a continuingcontamination source even after removal of the original source.

This interaction with geologic material tends to make the velocity of the organic solute slower thanthe velocity of groundwater. This slowing, or retardation, is a function of the fraction of organiccarbon in the aquifer matrix and the aqueous solubility of the organic solute compounds. The degreeof retardation is proportional to the organic carbon content of the geologic formation and inverselyproportional to the aqueous solubility of the compound.

Retardation is factored into contaminant transport through a retardation coefficient, which expressesthe relative velocity of contaminant chemical flow in relation to the velocity of groundwater flow.A retardation factor of five means that five pore volumes of water would have to move through a unitof aquifer in order to move the contaminant from an upgradient to a downgradient boundary.Retardation is the chief determinant of the time required to reduce contaminant concentrations to

values that meet the ES or to restore an aquifer to concentrations uniformly below detection. Theformer is much easier to achieve than the latter.

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The early stage of contamination dispersion decreases over time but tends to decrease in rate per unittime, resulting in a flattening curve and reaching a point at which the change per unit time becomes

small and remains virtually constant. The concentration vs. time plot approaches an asymptotic

relationship. The asymptotic part of the curve occurs because a chemical contaminant that is sorbed

into aquifer materials and occluded in small pores is very slowly released into the flowing

groundwater. The introduction of contaminants into an aquifer and the recovery is thus anasymmetrical cycle: what is introduced in minutes or hours takes months to years to recover.

The heterogeneity of the aquifer system complicates the process of interpreting the behavior ofcontaminants in groundwater. The uniformity of geology and flow in an aquifer system is calledisotropy, a state of uniform conditions in all directions from a given spot. A truly isotropic systemdoes not exist in nature. Some systems are reasonably isotropic in lateral directions or verticaldirections, but seldom in both directions because the deposition of geologic materials tends to resultin preferential geometric patterns for the mineral particles. For example, deposition of silt and clayparticles tends to result in the platelike particles lying face-to-face, a configuration that provides amore permeable flow path laterally than vertically. The net result is that aquifer systems tend to beanisotropic.

The proportions of fine-to-coarse particles that make up geologic formations are what influence thepermeability (ability to transmit water) of the formation. Because conditions that influenced the

original deposition of these materials varied greatly over small distances (as in a river depositing

suspended particles of different sizes according to the velocity of the water), permeability in aformation may vary widely over small distances. Monitoring wells that are emplaced to measureaquifer characteristics and allow collection of groundwater samples will show differences often toa hundred or more in permeability within the same formation. Each well is measuring only a virtualpoint in the aquifer system.

The wells are used as sampling points for the groundwater system. There is a tendency to believe thatthere should be uniformity in distribution of groundwater chemical constituents because, on a large

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scale, flow appears uniform. Actually, the heterogeneities of the system are reflected in well behavior.One well may monitor an area of high permeability and relatively rapid flow, whereas another wellmay be in a zone as much as a hundred times slower. Groundwater quality should reflect these flowconditions since the times of travel and flushing are proportional to permeability. A well in low-

permeability material should show much less rapid change in concentrations with time than one in ahigher-permeability area where transport is faster.

In a plume, another influence on contaminant distribution that is independent of the flow regime isthe type of contaminant input into the groundwater system. Contaminants are usually introducedintermittently with disposal events or effluent discharges. Contaminants are also introduced indiffering concentrations with their intermittent releases. Transport in groundwater tends to smooth

out some of the source variability with distance of transport, but it does not disappear.

With all of the sources of variability, one might question the feasibility of an interpretation orprediction about contaminant behavior. When fundamentals of the aquifer and contaminant chemicalcharacteristics are known, principles of flow and chemical behavior can be factored in to produce areasonably accurate picture of the way the system operates. It is understood that all sampling pointsand observations will not necessarily be uniform.

Biodegradation is another mechanism that may be significant in the transport and dissipation oforganic contaminants in groundwater. Recent studies have demonstrated that most aquifers harborbacteria capable of degrading a wide variety of organic chemicals. Variables that affect the rate andextent of degradation or transformation are dissolved oxygen content in the groundwater, density of

bacteria, availability of inorganic nutrients (nitrogen and phosphorus) to the bacteria, and the intrinsiccompound biodegradability. Generally, adding chlorine to the structure of an organic compounddecreases its biodegradability. Conversely, adding oxygen, sulfur, or nitrogen to an organiccompound's structure increases its biodegradability. For hydrocarbons such as benzene and toluenereleased into groundwater from gasoline, biodegradation can be a significant factor in the

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disappearance of the compounds. Chlorinated compounds are also biodegradable, but at a slowerrate.

Biodegradation is generally more rapid in water that contains more dissolved oxygen. Dissolved

oxygen was measured in eleven well clusters in the TCE plume on January 9, 1996 (Table 1). Thelevel of dissolved oxygen in six clusters was higher in the shallow wells (A) than in the deeper wells(B) because chemical reactions tend to deplete dissolved oxygen as oxygen-rich rainwater migratesdownward in the aquifer.

2.2 TCE Solute Transport in Plume 1-2 at the NPI SitePlume 1-2 originates in the southwest portion of the NPI site and is about 15,000 feet long and about1,700 feet wide (Figure 1). TCE is the only contaminant of concern detected above the ES.

TCE dissolved in groundwater has migrated from the sources on NPI property to the vicinity of theEau Claire north well field, following the path of groundwater flow. There were four areas in theplume where VOC concentrations were delineated by a 10-ug/l contour in 1992 (Figure 2). These

areas were the origin in the southwest portion of the NPI site; the vicinity of wells RW-15 and MW-38; the vicinity of wells RW-16 and RW-16B and C; and the vicinity of wells MW-52A and B andMW-53AandB.

The areas of higher concentration in 1992 had disappeared by the 1995 sampling (Figure 1). The1995 plume is delineated by 1- and 5-ug/l contours, except for the 10-ug/l contour that now occupiesa smaller area showing its origin on NPI property. The migration of TCE since 1992 has resulted insignificant attenuation. This distribution pattern is typical of plumes as they migrate and age, with

higher concentrations tending to disperse and dilute, while the low concentrations are maintainedthrough the slow release of contaminants from low-permeability zones and the desorption ofcontaminants from soil particles.

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TCE concentrations in most of the wells have decreased, and others have shown a relatively steadytrend over the period of record. The specifics of individual and overall trends will be discussed inthe following sections.

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3.0 NATURAL ATTENUATION RATE OF TCE IN PLUME 1-2

3.1 The TCE DatabaseThe TCE concentrations in the monitoring wells in Plume 1-2 have been measured for ten years.WESTON collected the groundwater samples from monitoring wells in Plume 1-2 and analyzed forVOCs in 1985-1987. EDER has been collecting groundwater samples from monitoring wells inPlume 1-2 from the end of 1987 until the present time.

There is no consistent historical record for each well during the ten-year period. Some of the earlywells were not sampled recently, and many more wells were installed during 1991 and 1992. Severalwells were sampled relatively frequently (five to ten times), while most of the wells were sampled onlytwo to three times.

Screen lengths in the monitoring wells also vary significantly. Many of the earlier wells screen up to40 to 50 feet of the aquifer saturated thickness. The groundwater samples collected from these wellsshow average TCE concentrations in the aquifer. Most of the monitoring wells were installed at alater time in two to three well clusters with 10-foot screens, and the groundwater samples from thesewells were collected at vertically discrete aquifer depths. These wells provide more accurate data onthe vertical distribution of TCE in the aquifer.

The TCE trends integrate all of the physical-chemical characteristics of the groundwater system, theTCE disposal history, and differences in the well screen zones. Although these factors may causevariations, the database is sufficient to analyze the current TCE trends, especially since several wellsshowing a clear TCE trend are screened at uniform depths and have been sampled several times overthe ten-year period.

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3.2 Trends in TCE Concentrations over Time in Monitoring Wells

Along the Plume CenterlineThe historical TCE data from thirty-three monitoring wells along the plume centerline are shown in

Table 2 and on Figures 3 through 35.

Most of the TCE data from wells that were sampled more than three times show clearly decliningtrends. The trends were described by the first order equation:

C = [Co * exp (-AT)] + 1 (1)

where C = the contaminant concentration at any time, ug/1

Co = the contaminant concentration at the beginning of the time interval, ug/1K = attenuation coefficientT = time, years1 = the asymptotic concentration at T = «, ug/1.

The natural rate of attenuation described by equation (1) is asymptotic, with a rapid decrease ascontamination is readily flushed from soil pore spaces followed by slow desorption andbiodegradation, which causes the contamination to persist in the groundwater at very lowconcentration. The TCE data at the plume edges shown in Figures 51 through 55 indicate that the

attenuation rate slows significantly when TCE concentrations approach 1 ug/1.

3.2.1 Selected Wells Indicating Declining TrendTCE concentrations in nine monitoring wells exceeded the ES in July 1995 and January 1996 (RW-3A and 3C, RW-15, RW-16B, MW-38A and B, MW-43A, MW-45C, and MW-53A). The TCEconcentrations in these wells range from 5.0 to 9.6 ug/1. Equation (1) was used to describe the TCEdata from the nine wells with the ES exceedances and two additional wells with a declining trend(RW-3B and RW-16C). The TCE data from MW-38A does not indicate a definite trend.

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The well cluster RW-3A,B,C is located at the end of the plume before it is captured at the ECMWF.The TCE concentrations at this cluster show a steep declining trend, falling below the ES by 1997.The TCE concentration decline at RW-3A,B,C is consistent with the data at the ECMWF, which also

show a consistent decline over time, after ECMWF production well 19 started operating in October

1993.

The TCE concentration vs. time graphs with the best fit lines are depicted in Figures 36 through 45.

The graphs show TCE concentrations declining below the ES from 1994 to 2008. The time estimatesfor the decline in TCE concentrations below the ES are summarized in Table 3. The data show thatTCE concentrations in most of the wells along the plume centerline should decline below the ES bythe year 2010.

3.2.2 Selected Wells Indicating No TrendThe TCE data from several wells along the plume centerline that were sampled more than three timesshow no declining trend.

No trend is observed, for example, in RW-2B and C, RW-19, and RW-23 (Table 2). The cluster wellRW-2B, C is located in a groundwater divide where the hydraulic gradient is very flat and thegroundwater flow velocity is very slow. The level of TCE at RW-19 and RW-23 is relatively low(2.5 to 4.5 ug/1), and the time frame from the first to last data points is approximately five years.Slow attenuation at this TCE level may not be noticed in this short period, especially wheregroundwater flow is significantly slower and in areas where there may be very little groundwater flow.

TCE concentrations in some isolated areas of the plume might exceed the ES in 15 years based onthe fact that TCE data from several monitoring wells does not show a declining trend. The TCE datafrom monitoring well MW-38A show no declining trend and recent TCE concentrations in this wellare at or slightly above the ES. This well is relatively close to the source (approximately 2000 feet)and it is possible that this well is still affected by the TCE from the source area before the extractionwells started operating. The TCE concentration in this area is not significantly affected by dispersion

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because it is close to the source, and the plume moves slowly in this area due to the relatively flat

hydraulic gradient.

3.3 Trends in TCE Concentrations over Time in Wells at the ECMWF

TCE concentrations in ECMWF production wells 11, 15, 16, and 17 have shown a significant decline

since well 19 started operating in October 1993. Well 19 intercepts the plume, and TCEconcentrations in this well are declining, although the TCE level is still slightly above the ES. TCEconcentrations in well 19 are projected to continue to decline based on the currently observed trend

and the data from the upgradient cluster RW-3 A,B,C, which also shows a consistent declining trend.The TCE concentrations in well 19 are projected to be consistently below the ES in two to threeyears.

TCE concentrations in the other ECMWF production wells (wells 11, 15, 16, and 17) are far below

the ES, and TCE trends in these wells show that TCE concentrations are near or below the PAL.The TCE data at the ECMWF are shown on Figures 46 through 50.

3.4 Trends in TCE Concentrations over Time in Monitoring Wells

Along the Plume EdgesTCE concentration trends were evaluated in five selected wells along the plume edges (RW-22, MW-39A, MW-49A and B, and MW-69A), wells with three or more data points. The TCE data for thesewells are shown in Table 4 and on Figures 51 through 55.

The data from these wells show only insignificant fluctuations in TCE concentrations over the general

range of 0.5 to 1 ug/1, or fluctuations declining below the TCE 1 ug/1 detection limit. The TCEconcentrations in these monitoring wells show the persistence of TCE at very low concentrations over

a relatively long period caused by the very slow desorption from soil, and biodegradation.

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4.0 HISTORICAL AND PREDICTED TCE PLUME 1-2

Three-dimensional (3-D) images of the historical TCE plumes were developed using GIS/Key and

GMS software packages. The input data consisted of the WESTON and EDER TCE databases,information on the extent of the buried valley, and the nature of the preferential groundwater flow

path.

4.1 Historical TCE Plumes

The TCE database and the conceptual understanding of the extent of Plume 1-2 have evolvedsignificantly since the mid-1980s, when WESTON conducted the initial site investigation.WESTON initially conceptualized Plume 1-2 as two plumes separated at the airport area. The 3-Dconceptual model of the TCE plume developed from the 1985-1987 data incorporated the currentconcept of one continuous plume. The 1985-1987 plume model shows the areas where TCEconcentrations exceed the 5 ug/1 ES and several areas where TCE concentration exceed 10 fig/1: inthe southwest portion of the NPI property extending to Highway 53, at the industrial park, at theairport, and in the area between the airport and the ECMWF (Figure 56).

The TCE database from the 1992 groundwater sampling is the most comprehensive. EDER installed

many monitoring wells during the RI, and groundwater samples were collected from most of these

wells. The 3-D conceptual model of the plume developed from the 1992 data shows that TCEconcentrations exceed 10 fig/1 in the southwest portion of the NPI property, to the east of Highway53, at the industrial park, and in the airport area. TCE concentrations in the area between the airportand the ECMWF declined from above 10 ug/1 in 1985-1987 to the range of 5 to 9 fig/1 in 1992

(Figure 57).

The 3-D conceptual model of the TCE plume developed from the 1995 data reflects continuingnatural attenuation and the impact of extraction pumping. The model shows several areas where

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TCE exceeds the ES. TCE concentrations exceed 10 ug/1 only in the southwest portion of the NPI

property (Figure 58).

4.2 Predicted TCE Plumes

The predicted 3-D plume image was developed from the historical TCE data by applying the TCEattenuation rate, which was established from the trend analysis to illustrate the declining TCEconcentrations. The attenuation rate is conservatively estimated at 12, which is derived from the

trend analysis in selected monitoring wells along the plume centerline. This attenuation rate wasused to estimate TCE concentrations in Plume 1-2 in 15 years.

The predicted 3-D plume image shows that by the year 2010 the TCE concentrations in Plume 1-2are projected to decline below the ES level. TCE concentrations are projected to exceed the ES only

in the southwest portion of the NPI property, where TCE contaminated groundwater is effectivelycaptured by the extraction wells (Figure 59).

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5.0 CONCLUSIONS

The following conclusions are drawn from this study of the natural attenuation of TCE in Plume 1-2:

• There is a clear declining trend in TCE concentrations.

• TCE concentrations in most of the monitoring wells are projected to decline belowthe ES before the year 2010.

• The declining trend in TCE concentrations becomes asymptotic at approximately 1ug/1.

• TCE concentrations in ECMWF production wells 11, 15, 16, and 17 have declinedsignificantly since well 19 started operating in October 1993, and TCE levels in these

wells are near or below the PAL.

• The TCE concentrations in ECMWF production well 19 show a declining trend andare projected to be consistently below the ES within two to three years.

• TCE concentrations in cluster well RW-3A,B,C, upgradient of ECMWF productionwell 19, are projected to decline below the ES in 1997.

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TABLES

NATIONAL PRESTO INDUSTRIESEAU CLAIRE, WISCONSIN

TABLE 1

DISSOLVED OXYGEN CONCENTRATIONS FOR SELECTED WELLSIN PLUMES 1 AND 2 MEASURED JANUARY 9, 19%

WELL NEST ID

MW-11MW-10MW-70MW-34MW-67MW-68MW-4

MW-23MW-69MW-71

MW-39

A WELL

D.O. CONCENTRATION (mg/l)

4.55.08.07.58.64.87.85.28.38.3

3.6

BWELL

D.O. CONCENTRATION (mg/l)

9.06.78.05.34.64.51.81.85.58.8

6.4

31-Jan-96


TABLE 2

TCE CONCENTRATIONS IN MONITORING WELLS ALONG THE PLUME CENTERLINE

SAMPLE I.D. :

AMPLE DATE :

Oct-85

Jul-87Oct-87Oct-88Jul-89Sep-89May-90Jun-90Jul-90Apr-91Dec-91

Jul-92Feb-94Mar-94Jun-94Aug-94Oct-94Jan-95Apr-95Jul-95Sep-95Jan-96

RW-3A

13

7.1NANANANANANANA66

6NANANANANANANA5

NA5.5

RW-3B

24

13NANANANANANANA109

9NANANANANANANA4

NANA

RW-3C

26

14NANANANANANANA11.09.0

9NANANANANANANA5

NA9.1

RW-15

NA

1114

NANA9.010.0NANA8.05.0

10NANANANANANA7.37

NA7.8

RW-16B

NA

NANANANANANANANA9.018.0

18NANANANANANANA8

NA8.9

RW-16C

NA

NANANANANANANANA9.08.0

8NANANANANANANA3

NANA

MW-38B

NA

NANANANANANANANA1110

10NANANANANANA1.76

NA9.6

MW-43A

NA

NANANANANANANANA76

6NANANANANANANA5

NA5

MW-45C

NA

NANANANANANANANANA9

9NANANANANANANA8

NA7.6

MW-53A

NA

NANANANANANANANANA7

7NANANANANANANA7

NA5.5

litoring wells RW-3A, RW-3B, RW-3C, RW.15, RW-16B, RW-16C, MW-38B, MW-43A, MW-45C, and MW-53A were used in trend analysis.- Not Analyzedconcentrations in ug/1.2 06-Feb-96 Page 1 of 3


TABLE 2

TCK CONCENTRATIONS IN MONITORING WELLS ALONG THE PLUME CENTERLINE

SAMPLE I.D. :AMPLE DATE :

Oct-85Jul-87Oct-87Oct-88Jul-89Sep-89May-90Jun-90Jul-90Apr-91Dec-91Jul-92Feb-94Mar-94Jun-94Aug-94Oct-94Jan-95Apr-95Jul-95Sep-95Jan-96

RW-2A

2.72.9NANA3

NA2

NANA3

NA3

NANANANANA1.91.91.9NANA

RW-2B

4.93.2NANA5

NA4

NANA4

NA5


RW-2C

6.96.1NANA6.0NA6.0NANA6.0NA6


RW-I4

NANANANANANANANA6

NANA6

NANANANANANANANANANA

RW-16

NA9.67.6NANANA8.08

NA8.08.08


RW-17

NA9

9.8NANANANA10.0NANANA10


RW-19

NA2.43.1NANANANANA3

NANA3


RW-23

NA4.14.6NANANANANA4

NANA4


MW-38A

NANANANANANANANANA755

NANANANANANA7.65

NA5.9

MW-38C

NANANANANANANANANANA44

NANANANANANA<14

NANA

MW-4IA



MW-41B



Not Analyzedoocentratioos in ug/l.

06-Feb-96 Page 2 of 3


TABLE 2

TCE CONCENTRATIONS IN MONITORING WELLS ALONG THE PLUME CENTERL1NE

SAMPLE I.D. :SAMPLE DATE :

Oct-85Jul-87Oct-87Oct-88Jul-89Sep-89May-90Jun-90Jul-90Apr-91Dec-91Jul-92Feb-94Mar-94Jun-94Aug-94Oct-94Jan-95Apr-95Jul-95Sep-95Jan-96

MW-43B


NANANANANANANA2

NANA

MW-44A



MVV-44B

NANANANANANANANANANA0.77


MW-45A


NANANANANANANA2

NANA

MW-45B


NANANANANANANA3

NANA

MW-46A



MW-46B



MW-46C



MW-53B


NANANANANANANA2

NANA

MW-55B



MW-55C



•JA - Not AnalyzedMl concentrations in ug/1.

WB2 06-Feb-96 Page 3 of 3


TABLE 3

ESTIMATED TIME FOR TCE CONCENTRATIONS TO DECLINEBELOW THE ENFORCEMENT STANDARD

WELLI.D. :

RW-3ARW-3BRW-3C

MW-38BMW-43AMW-45CMW-53A

RW-15RW-16BRW-16C

ESTIMATED TIME :

1996199519972001199520082002200220021994

(2 31-Jan-96


TABLE 4

TCE CONCENTRATIONS IN MONITORING WELLS ALONG THE PLUME EDGES

SAMPLE LD. :

SAMPLE DATE :

Jul-87

Oct-87Jul-90Apr-91Dec-91Jul-92Feb-94Mar-94Jun-94Aug-94Oct-94

Jan-95Apr-95Jul-95

RW-22

0.86

0.980.9NANA0.9NANANANANA

NANANA

MW-39A

NA

NANA0.8NA0.80.2

11

<1<1

NA<1NA

MW-49A

NA

NANANA0.70.7NANANANANA

NANA0.9

MW-49B

NA

NANANA

11

NANANANANA

NANA0.7

MW-69A

NA

NANANANA0.60.4

11

<1<1

<1<1NA

NA - Not AnalyzedAll concentrations in ug/1.

06-Feb-96

FIGURES

FIGURE 1

I

JW CMravMn WT/CW Av«c;

SITE MAP WITH MONITORINGWELLS AND TCE ISOCONTOURS IN

PLUME 1-2. 1995NATIONAL PRESTO INDUSTRIES. INC. SITE

EAU CLAIRE, WISCONSIN

eder associatesFIGURE 2

our «b>wMr»<f MIT fww pm*)

• USCPA UonHattf Mr f

• Ftu A** *fn**ttt MT Location

9 AAvM MT IT/TCf Om»<r»«bf>TCC

iw-rwAxWC I

S:|TOT Co

7QF M»ta> *l

SITE MAP WITH MONITORINGWELLS AND TCE ISOCONTOURS

PLUME 1-2. 1992NATIONAL PRESTO INDUSTRIES. INC. SITE

EAU CLAIRE. VWSCONSIN

IN

TCE vs. Time Graphs in Wells Along the Plume Centerline

Figures 3-35

>-HH

8

7

6

P 4

§ ,U 3

W

NATIONAL PRESTO INDUSTRIESMONITORING WELL RW-2A

0Nov-84

_i__.__.___J_._. „.. .j___ I

Nov-86 Nov-88 Nov-90DATE

Nov-92 Nov-94oc3)mCA>

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8

7§H—I

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5

4

3

NATIONAL PRESTO INDUSTRIESMONITORING WELL RW-2B

oNov-84 Nov-86 Nov-88 Nov-90

DATENov-92 Nov-94

oc00m

NATIONAL PRESTO INDUSTRIESMONITORING WELL RW-2C

TCE

CON

CEN

TRA

TIO

N (u

g/1)

i\j

9

8

7

6

5

4

3

2

1

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i ._ 1 i 1 i 1 j_ L • _i

-84 Nov-86 Nov-88 Nov-90 Nov-92 ISNov-94DATE

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§ «U

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Nov-84 Nov-86 Nov-88 Nov-90 Nov-92 Nov-94 Nov-96DATE

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0Nov-84 Nov-86 Nov-88 Nov-90

DATENov-92 Nov-94

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•—

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-84 Nov-86 Nov-88 Nov-90 Nov-92 Nov-94 Nov-96DATE

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10

9

76

5

8 4

y i

( (

NATIONAL PRESTO INDUSTRIESMONITORING WELL RW-14

0May-90 May-91 May-92

DATE -nOc20m(O


16

14S3"

I"H 10

8

U 6

§ 4U 4

UH

0Jul-86 Jul-88 Jul-90 Jul-92

DATEJul-94 Jul-96

ocmo

12

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,H

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UH

r


0Mar-86 Mar-87 Mar-88 Mar-89 Mar-90 Mar-91 Mar-92

DATEoc03m


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HWUy^jouwuH

Z.V7

18

16

14

12

10

8

6

4

2

0

. .»^-- . . - - - / ^^

- - - - - / - - - - - - ^ \. . . . ./.'.... . . . . . . . . - . . . . . . . > -- - / - - . . . . . . . . . . - • -

"

__ . __ . _ _ _ 1 _ _ _ _ __ . . 1 . .. . . J . _ . _ _ _ . _ __ l _ _ _ _ . 1 . . . . I

Nov-90 Nov-91 Nov-92 Nov-93 Nov-94 Nov-95DATE

QC33mto


Nov-90 Nov-91 Nov-92 Nov-93DATE

Nov-9425c33m


16

>4

H 10

I •U 6

O A.U 4

U 2H

0 __i_Mar-86 Mar-87 Mar-88 Mar-89 Mar-90 Mar-91 Mar-92 -n

DATE ?33m

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0


Mar-86 Mar-87 Mar-88 Mar-89 Mar-90 Mar-91 Mar-92 3

DATE cO)mOl


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0Mar-86

__j_ - -!__..„

Mar-87 Mar- Mar-89 Mar-90DATE

Mar-91 Mar-92ocDOrn

NATIONAL PRESTO INDUSTRIESMONITORING WELL MW-38A

TCE

CON

CEN

TRA

TIO

N (u

g/1)

I vr

9

8

7

6

5

4

3

2

1Oct

- . ^-"-90 Oct-9 1 Oct-92 Oct-93 Oct-94

DATEOct-95 Oct-96

31Qc33m

HH

H

H

§U

§UwuH

NATIONAL PRESTO INDUSTRIESMONITORING WELL MW-38B

12

11

10

9

8

7

6

5

4

3

2

1Oct-90 Oct-91 Oct-92 Oct-93

DATEOct-94 Oct-95 Oct-96

QC33m00

NATIONAL PRESTO INDUSTRIESMONITORING WELL MW-38C

8

6P 5

H 4

OUWUH

0Jun-91 Jun-92 Jun-93

DATEJun-94 Jun-95

TCE data at 0.5 ug/1 indicate that TCE was not detected (detection limit was 1 ug/1).

T]OcJDm—kCD

wU§UwUH

10

8


0Mar-91 Mar-92

DATE

oc3)mIN)o


10

8

HHH

§

uH

0Mar-91

DATE

. __ . . .—_. . . _..j_._....Mar-92 •n

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NATIONAL PRESTO INDUSTRIESTC

E CO

NCE

NTR

ATI

ON

(ug/1

)

1098

76

5

4

3

2

1Oct

ivivjmiivjivmuji YYJLLJLJ iviyy-*tj/\

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< i i i i i i i i i 1 i-90 Oct-91 Oct-92 Oct-93 Oct-94 Oct-95 Oct-96

DATE §c33mroro


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DATEJun-94 Jun-95 o

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c


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H

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u1

0Sep-91 Sep-92

DATE oc30mto

109

7

6

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0Sep-91 Sep-92

DATE•n25c3)mN>en


/ • * \•a

8 2§uw 1


DATEJun-94 Jun-95

c>c33mroo>

p

U

§uwuH

109876

5

4

3

2

1


oJun-91 Jun-92 Jun-93

DATEJun-94 Jun-95

31QC31m


TCE

CON

CEN

TRA

TIO

NS

(ug/

1)

* 4*

10

8

6

4

2

0Jim

" " ——— — —— ——— ——— MM

-91 Jun-92 Jun-93 Jun-94 Jun-95 Jun-96DATE oc

33mw00


7

6

U§ 2UW iU *H

0Sep-91 Sep-92

DATE 25c33mro(O


7

6

H4

H§ 3u

0

uH8 '

0Sep-91 Sep-92

DATE |mCOo

8

I7I6P 5

P 4

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U *

U 1H


oSep-91 Sep-92

DATET]Oc3DmGJ


14

12

§ 10h—IH

8

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UW 9U 2

0Jun-91 Jun-92 Jun-93 Jun-94

DATEJun-95 Jun-96

ocIDm

§

H

§U

§UwUH


14

12

10

8


DATEJun-94 Jun-95

25c3mGJ


8

P 5

H 4

§ 2UU 1H

oAug-91 Aug-92

DATEocDOmO)


8

7

P 5

§ 3

§ 20 Z

w tU 1H

0Sep-91 Sep-92 §

DATE cmOi01

TCE vs. Time Graphs in Wells Along the Plume CenterlineWith the Best Fit Lines

Figures 36 - 45


^ ^

*§>

wu§uwuH

C=9*exp(-T/12)+l

Jan-80 Jan-85 Jan-90 Jan-95 Jan-2000 Jan-2005 Jan-2010YEARS

Analytical Data Predicted Concentrations

25c3)muo>


C=21*exp(-T/5.6)+l

Jan-80 Jan-85 Jan-90

Analytical Data

Jan-95 Jan-2000 Jan-2005 Jan-2010YEARS

—— Predicted Concentrations

oc3)mGJ


30

P 20

H 15

§y 10

uH

0Jan-80

C=20*exp(-T/7.6)+l

ES

Jan-85 Jan-90

Analytical data

Jan-95 Jan-2000 Jan-2005YEARS

Predicted concentrations

Jan-2010

oc3DmCO00


16^e§p

iuw£

C=10*exp(-T/15)+l

ES

-I————I I————I————1————U -I——I——I——I——I——I I I

Jan-80 Jan-85 Jan-90 Jan-95 Jan-2000 Jan-2005YEARS

Jan-2010

Analytical data Predicted concentrationsoc33mOJ(O


"3x»§H

2018161412108

§uw

0Jan-80

G=14*exp(-T/9)+l

Jan-85 Jan-90

Analytical data


—— Predicted concentrations

oc3Dm


C=9*exp(-T/3)+l


Analytical data Predicted concentrationsoc33m


121110

Wu§uwuH

C=10*exp(-r

i i i i—i—i—i—i—I—\—i—i—i—i—i—i—i i—i—i—i * i i i i i i

Analytical data concentrations

1Jan-80 Jan-85 Jan-90 Jan-95 Jan-2000 Jan-2005 Jan-2010

YEARS

25c3)m*.ro


%£6P"jj

§u§uwu

i^.

1110o

87654121

______

. - - »«

_ _ _ _ ~ ~ ~ 1 - - - - - ; ,

C=6*exp(-T/13)+l -^'i

^5: ———r- T$F^-^

i i i

ES

r— _ .

~^~~- -—_.* • —

i, , , , i , , : , 1 , , , 1 , , , , i . . 1


• Analvtical data Predir.teH r.nnrpntratinnc

oc33m*>co



Jan-2000 Jan-2005 Jan-2010

Analytical data Predicted concentrationsoc33m


1>fPpauIpa

121110

87654

21

Jan-80

C=6*exp(-T/22)+l

ES

Jan-85i i i i

Jan-90 Jan-95 Jan-2000 Jan-2005 Jan-2010YEARS

Analytical data Predicted concentrationsoc3m•uen

TCE vs. Time Graphs in ECMWF Production Wells

Figures 46-50

Concentration, ppb01

om

oH

m

Concentration, ppb

o

m

Concentration, ppb01 too

u> vp

O

m

Concentration, ppbO1 en roo

O)

U>C/3

O

m

Concentration, ppb

o

m

09

TCE vs. Time Graphs in Wells Along the Plume Edges

Figures 51 -55


2.5

U 9>—i ^H

H 1.5

§U i

§ 'Upa 0.5u

0Jul-86

L. . __ . .__L . . _ _ _ _ L _ . . _ _ _ _ _ L._ . _._

Jul-87 Jul-88 Jul-89 Jul-90DATE

Jul-91 Jul-92 Jul-93c3)mUl


_ 2.5i >H 1-5

U

§UwUH

0.5

0Nov-90 Nov-91 Nov-92 Nov-93

DATENov-94

TCE data at 0.5 ug/1 indicate that TCE was not detected (detection limit was 1 ug/1).oc33m01


3

_ 2.5

8 2

H 1.5

§U i

§

u °-5UH

0Jun-91 Jun-92 Jun-93 Jun-94 Jun-95

DATE oc33men


"§>£3

£5H-H

H

pdL™"

£wCj

o[•T1

^

_>

2 5^•*J

2

1 5

1

0.5

0

'" " ~— —— -———__ ___

> i > i i i i iJun-91 Jun-92 Jun-93 Jun-94 Jun-95

DATEen


2.5

§ 2h—I •£H

P 1.5

u§uuH

0.5

0Mar-92 Mar-93 Mar-94 Mar-95

DATE

TCE data at 0.5 ug/1 indicate that TCE was not detected (detection limit was 1 ug/1).

oc33mtnen

3-D Conceptual Models of the TCE Plumes

Figures 56 -59

SDMS US EPA REGION VCOLOR-RESOLUTION - 2

IMAGERY INSERT FORMThe following page(s) of this document include color or resolution variations.Unless otherwise noted, these pages are available in monochrome. The originaldocument is available for viewing at the Superfund Records Center.

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DOCUMENTVARIATION

DATE OF ITEM(S)

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PHASE

OPERABLE UNITS

LOCATIONpij A cirr HASIir

(AR DOCUMENTS ONLY)

NATIONAL PRESTO IND

40954

3-D CONCEPTUAL MODEL

COLOR OR X RESOLUTION

2/1/96

4

AR

Box # 6 Folder # 6 SubsectionX Remedial Removal Deletion Docket Original

Update # Volume of

COMMENT(S)

Clj

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Documents

EDER ASSOC PC - STUDY OF NATURAL ATTENUATION OF TCE IN ... · eder associates 1.0 INTRODUCTION 1.1 Study Objectives This report describes the natural attenuation trend of TCE in Plume