Retrospective Study of Closed Leaking Underground Storage Tank (UST) Sites in Wisconsin

A.M. Pelayo*, T.A. Evanson, J.M. Bahr and M.E. Gordon

*Wisconsin Department of Natural ResourcesBureau for Remediation & Redevelopment

aristeo.pelayo@wisconsin.gov

GSA, Oct. 7, 2008

What is “Closure?”

State regulator agrees with request from responsible party that NO FURTHER ACTION is necessary.

Closure involves proper abandonment (i.e., filling and sealing) of all monitoring wells.

Brief Administrative History Affecting WI UST Closures

• Nov. 1996: Allowed “flexible closure” for sites that may still exceed state cleanup standards

• May 2001: Implemented web-based “GIS Registry of Closed Remediation Sites” (http://dnrmaps.wi.gov/imf/imf.jsp?site=brrts2)

1999-2000: Huge influx of closures (1,378 now in GIS Registry)

Retrospective Study

1. Database– Devised a stratified random sampling to select sites

for review– Compiled site-specific information (133 site reviews)– Evaluated collective data for metric(s) to determine

effectiveness of NA as a remedy

2. Post-closure fieldwork at 10 sites– Did forecast prove to be true?

ClosuresReviewed

133 Sites from 45 counties

0 50 10025

Miles

Milwaukee, Brown and Dane had 34% of sites reviewed.

Stratified-Randomly Selected Sites

DB QueriesMonitoring

Wells Total number of wells with GW data Median: 7 wells

Remediation

Soil Excavation? 85 Yes  Pump and Treat? 33 Yes

38 sites (or 29%) implemented NO remediation.

Depth to Groundwater

Count

91

20

83 0 0 0 1 0 0

0

10

20

30

40

50

60

70

80

90

100

≤ 0

> 0

. to

≤ 1

0.

> 1

0. to

≤ 2

0.

> 2

0. to

≤ 3

0.

> 3

0. to

≤ 4

0.

> 4

0. to

≤ 5

0.

> 5

0. to

≤ 6

0.

> 6

0. to

≤ 7

0.

> 7

0. to

≤ 8

0.

> 8

0.

Median6.5 ft

Mean9.3 ft

# of Sites in database with information: 123

Minimum depth to Water (ft)

≤10’

Highest Concentrations in GW Samples from the Database Sites

102

10.

1.

0.1

103

104

105

106

107

Ma

xim

umC

onc

ent

ratio

n(u

g/l)

fro

mS

iteG

rou

nd

wat

er

Sa

mp

les

Naphthalene(31)

Benzene(1,790)

MTBE(51,000)

Increasing Solubility in Water (Sw)

Xylene(160)(Sw, mg/l)

Ethylbenzene(170)

102

10.

1.

0.1

103

104

105

106

107

Ma

xim

umC

onc

ent

ratio

n(u

g/l)

fro

mS

iteG

rou

nd

wat

er

Sa

mp

les

Naphthalene(31)

Benzene(1,790)

MTBE(51,000)

Increasing Solubility in Water (Sw)

Xylene(160)(Sw, mg/l)

Ethylbenzene(170)

1% Sw

8.5% Sw

2% Sw

1% Sw

10% Sw

102

10.

1.

0.1

103

104

105

106

107

Ma

xim

umC

onc

ent

ratio

n(u

g/l)

fro

mS

iteG

rou

nd

wat

er

Sa

mp

les

Naphthalene(31)

Benzene(1,790)

MTBE(51,000)

Increasing Solubility in Water (Sw)

Xylene(160)(Sw, mg/l)

Ethylbenzene(170)

1% Sw

8.5% Sw

2% Sw

1% Sw

10% Sw

29Sites

21Sites 16

Sites

8Sites

0 Site37 Sites (or 28%) have NO Naphthalene

data!

HISTORICAL Maximum

Benzene in Groundwater

132 sites w/ data

1

6

12

30

52

28

3

1 10 100 103 104Factor above ES 105

10

20

30

40

50

60

0

Countof

Sites

Benzene

HistoricalMaximumLevels(ug/l)

Max:210,000

Mean6,300

Median1,200

1% Sw18,000

Below ES

CLOSURE Maximum

Benzene in Groundwater

132 sites w/ data

1 10 100 103 104Factor above ES

10

20

30

40

50

60

0

Countof

Sites

Benzene

ClosureMaximumLevels(ug/l)

Max:20,000

Mean690

Median56

1% Sw18,000

Below ES

37 38

27

4

1412

0

>0

.0to

0.5

>0

.5to

1.0

>1

.0to

1.5

>1

.5to

2.0

>2

.0to

2.5

>2

.5to

3.0

>3

.0to

3.5

>3

.5to

4.0

>4

.0to

4.5

>4

.5to

5.0

>5

.0to

5.5

>5

.5to

6.0

>6

.0to

6.5

>6

.5to

7.0

>7

.0to

7.5

>7

.5to

8.0

>8

.0to

8.5

>8

.5to

9.0

>9

.0to

9.5

>9

.5to

10

.0

>1

0.0

to1

0.5

>1

0.5

5

10

15

0

Countof

Sites

Time (Years)

Time Interval BetweenHistorical Benzene Maximum and

Most-Recent “Closure” Benzene Maximum

Max:Mean:

Median:

10.43.12.6

ALL RemedYES

RemedNO

10.43.73.5

6.71.51.1

5 101

No. of Sites: 132 94 38

years

Median Time Interval:

3.5 yr for sites with active remediation

1.1 yr for MNA-sites

Synopsis – Database Study

• Collectively, a factor of 10 reduction in maximum benzene concentration

• Short monitoring period, even shorter for sites that were not remediated

Will we see similar decrease 5 years post closure?

10 Field Sites in the WI Closure Protocol

Study

Former Retail Station

Non-Commercial Site

Post-Closure Field Study

Post-Closure Investigation

• Installed monitoring wells:– Near locations where previous site

investigation (SI) detected benzene– Further downgradient than SI

• Used GeoProbe, except at 2 of the 10 sites. PC water-table wells had screens as long as SI wells.

Total BTEX

Plumes

Closure (Blue) Outline

Post Closure Outline

[Keller, 2005][Greve, 2007]

Closure

Post-Closure

Groundwater flow variabilityTotal BTEX Plume [Greve, 2007 ]

1998 20052000

Former Grandma’s Restaurant site’s plume axis Former Grandma’s Restaurant site’s plume axis shifted roughly 40°. shifted roughly 40°.

0 100 ft

Benzene Maximums

RedPost-Closure > Closure

Out of the 10 Field Sites ...

• We found 5 sites with benzene levels higher than their respective closure maximums.

• BUT ... We did not find benzene in as many wells as previously found for all 10 sites.

SI0 200 Ft100

20 40 60 80 1000 150 Ft

UtilityPole

UtilityPole

UtilityPole

YellowR/W Post

OldMW-2

Garage

House

PrivateWater SupplyWell

WoodenShed

Asphalt Shoulder

PrivateGravel

Driveway

ApproximateLocation of

Former DispenserIsland

ApproximateLocation of

Former USTs

PrivateGravel

Driveway

PrivateGravel

DrivewayAsphalt Shoulder

Asphalt Shoulder

Asphalt Shoulder

Concrete

Concrete

MW-1

MW-3

MW-6MW-7

SI benzene detection (1991 to 1999)

Post-Closure

P-C benzene detection (2005 - 2006)

BenzeneDetections

BTEXPlume

Q: Did we miss the B plume in our Post-Closure investigation?

• A: Perhaps. But if we missed B, why are we finding TEX at locations farther than previously found?

• Let’s look further at the Naphthalene data.

Naphthalene Detections (at Water-Table Monitoring Wells)

Previous Site Investigation

Site NameNo. of SI W-T

WellsWells w/ N

detectsDetection

Frequency

Brown County Reforestation Camp

4 1 25 %

Martin Oil 12 2 17 %

Town of Rutland Garage

5 2 40 %

Woods Garage 10 4 40 %

Grandma's Restaurant & Truck Stop

11 4 36 %

Charles Packard Property

8 4 50 %

Grafton DPW 6 2 33 %

WI Lions Camp 15 12 80 %

City of Racine Parks Dept

7 1 14 %

UW Oshkosh Field Studies Building

12 11 92 %

Post-Closure Investigation

No. of P-C W-T Wells

Wells w/ N detects

Detection Frequency

9 3 33 %

9 4 44 %

12 5 42 %

9 5 56 %

12 6 50 %

10 6 60 %

10 5 50 %

10 3 30 %

12 3 25 %

10 3 30 %

Post-Closure Investigation

No. of P-C W-T Wells

Wells w/ N detects

Detection Frequency

9 3 33 %

9 4 44 %

12 5 42 %

9 5 56 %

12 6 50 %

10 6 60 %

10 5 50 %

10 3 30 %

12 3 25 %

10 3 30 %

Naphthalene Improvement?

RedPost-Closure > Historical Max

YellowImprovement, but not by a

factor of 10!

Post-Closure VOC Plume

• Characteristic has changed over time

– P-C benzene levels at the source wells about as high as closure max, but benzene plume more spatially constrained, tending to remain near the source.

– P-C naphthalene levels at the source wells as high as historical max, and plume extended farther from the source.

Post-Closure0 200 Ft100

20 40 60 80 1000 150 Ft

P-1P-2

P-3

UtilityPole

UtilityPole

UtilityPole

YellowR/W Post

OldMW-2

TW-2

TW-4

TW-9

TW-3

Garage

House

PrivateWater SupplyWell

WoodenShed

Asphalt Shoulder

PrivateGravel

DrivewayP-4

P-5

P-6

P-7

Piezometer(25‘-30’ screen)

TW-11

TW-12P

TW-14 TW-13

TW-12

Piezometer(25‘-30’ screen)

ApproximateLocation of

Former DispenserIsland

ApproximateLocation of

Former USTs

PrivateGravel

Driveway

PrivateGravel

DrivewayAsphalt Shoulder

Asphalt Shoulder

Asphalt Shoulder

Concrete

Concrete

MW-1

MW-3

MW-6MW-7

Post-Closure BENZENE detection

Post-Closure0 200 Ft100

20 40 60 80 1000 150 Ft

P-1P-2

P-3

UtilityPole

UtilityPole

UtilityPole

YellowR/W Post

OldMW-2

TW-2TW-6

TW-1

TW-4

TW-9

TW-3

Garage

House

PrivateWater SupplyWell

WoodenShed

Asphalt Shoulder

PrivateGravel

DrivewayP-4

P-5

P-6

P-7

Piezometer(25‘-30’ screen)

TW-11

TW-12P

TW-14 TW-13

TW-12

Piezometer(25‘-30’ screen)

ApproximateLocation of

Former DispenserIsland

ApproximateLocation of

Former USTs

PrivateGravel

Driveway

PrivateGravel

DrivewayAsphalt Shoulder

Asphalt Shoulder

Asphalt Shoulder

Concrete

Concrete

MW-1

MW-3

MW-6MW-7

Post-Closure NAPHTHALENE detections

BTEXPlume

Conclusion/Recommendation After the Study

• Contaminant concentrations in source zones are relatively unchanged 5 – 6 years post-closure.

• Unable to make realistic projections of when standards will be met in groundwater. (Monitoring ~ < 5 yrs; Time to reach standards ~ 10s of Decades or Longer)

• Effective land use controls are needed far into the future to account for the long period of time contaminants are likely to remain in soil and groundwater.