Remedial Overview of USACE Reservoir Report

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22 févr. 2014 (il y a 3 années et 3 mois)

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Remedial Overview of USACE Reservoir Report

January 15, 2014


Jill Lowe, EPA


Travis Fatzinger, USACE

BoRit Asbestos Superfund Site

Overview



USACE Report on BoRit Reservoir


Reservoir Hydrology


Berm

Stability


Options Reviewed



BoRit Asbestos Superfund Site

USACE Report



Remedial Inter Agency Agreement (IA) with U.S. Army
Corps of Engineers (USACE)


Tasks


Analyze Hydraulics of Reservoir


Assess
Berm

Stability


Investigations Performed


Geotechnical Investigations


Water Level Investigation


Berm

slope stability and seepage

























BoRit Asbestos Superfund Site

USACE Report



Hydraulics Study


Transducers


March
-
August 2013


3 transducers in wells MW
-
01a, MW
-
02, and MW
-
03


1 in Reservoir


Transducer


July 2013
-
August 2013


1 transducer in background well, MW
-
07



Monitoring Locations

BoRit Asbestos Superfund Site

Ambler, PA

Figure 3.1

August 2013

Legend

Monitoring Well, Transducer

Monitoring Well, No Transducer

Staff Gauge, Transducer

Staff Gauge, No Transducer

Pennsylvania

BoRit

BoRit Asbestos Superfund Site

USACE Report



Hydraulics Study Conclusions


Reservoir


No direct correlation between groundwater and Reservoir


Water levels correlate to rainfall and evaporation


Known seep is not significant


Groundwater


Significant drawdown Monday through Friday

o
Identified 2
-
Non
-
potable production wells




BoRit Asbestos Superfund Site

USACE Report

Geophysical Investigation


Multi
-
channel analysis of surface waves (MASW)


Characterize Soil


Self
-
potential (SP)


Water flow


EM61 Metal Detector


Ground Penetrating Radar (GPR)


Probable pipe locations targeted based upon drawings from
Whitpain

Township and removal work


Known pipes likely filled in with sedimentation

8

Zone of Weak Material in SW Berm

BoRit Asbestos Superfund Site

Ambler, PA

Figure 2.2

August 2013

Geotechnical Investigation


Boring locations based on survey cross
-
sections,
geophysical results, and seepage locations


Three Borings



Continuous Split Spoon Sampling


Advanced until bedrock refusal


Lab testing on Samples


Included sieve analyses,
triaxial

consolidated
-

undrained
, unconfined compression

10

Locations of BOB
-
1, BOB
-
2, and BOB
-
3

BoRit Asbestos Superfund Site

Ambler, PA

Figure 2.4

August 2013

Slope Stability Model


GeoStudio

2012



Seep /W


Slope /W


Survey Profiles


Soil Profiles


Lab Results

12

BOB
-
2 Current Geometry High Head

BoRit Asbestos Superfund Site

Ambler, PA

Figure 4.5

August 2013

Legend


FS= 0.93

Pennsylvania

BoRit

Layer

Material

γ (
汢猯晴
3
)

φ(
°
)

Cohesion (lbs/ft
2
)

Region 1

Sandy SILT (Drained)

115

22

0

Region 2

Poorly Graded SAND (Drained)

120

33

0

Region 3

Bedrock

N/A

N/A

N/A

Region 4

N/A

N/A

N/A

N/A

Region 5

Clean Silty Sand FILL (Drained)

115

34

0

Region 6

Dense Silty SAND (Drained)

125

34

0

Region 7

Loose Silty SAND (Drained)

115

29

0

Current Condition

Slope Stability Results

Current Geometry

Boring

Factor of Safety
1

Normal Water Level

Factor of Safety

High Head


Level

BOB
-
1

3.28

2.70

BOB
-
2

1.12

0.93

BOB
-
3

1.46

1.26

1

Factor of Safety = material strength/design load. USACE target is 1.4

14

BoRit Asbestos Superfund Site

USACE Report



USACE Options to cover ACM and stabilize
berm


Option 1


Flatten exterior slope


Add stability
berm

to exterior toe of slope (
Wissahickon

side)


Option 2


Sheetpile


Option 3


Increase
berm’s

cross
-
sectional width


Flatten interior slope to 3H:1V =18
°


Material stable to 30
°

resulting in Factor of Safety of 1.7

BOB
-
2 Proposed Geometry Normal Head

BoRit Asbestos Superfund Site

Ambler, PA

Figure 4.8

August 2013

Legend


FS= 1.63

Pennsylvania

BoRit

Layer

Material

γ (
汢猯晴
3
)

φ(
°
)

Cohesion (lbs/ft
2
)

Region 1

Sandy SILT (Drained)

115

22

0

Region 2

Poorly Graded SAND (Drained)

120

33

0

Region 3

Bedrock

N/A

N/A

N/A

Region 4

N/A

N/A

N/A

N/A

Region 5

Clean
Silty

Sand FILL (Drained)

115

34

0

Region 6

Dense Silty SAND (Drained)

125

34

0

Region 7

Loose Silty SAND (Drained)

115

29

0

Region 12

BACKFILL

110

30

0

Proposed Geometry

Slope Stability Results

17

Proposed Geometry

Boring

Factor of Safety

Normal

with Fill

Factor of Safety

High Head


with

Fill

BOB
-
1

3.87

3.44

BOB
-
2

1.63

1.62

BOB
-
3

1.57

1.47

Option 3 with GCL


Supplement clay fill with Geosynthetic Clay Liner (GCL)


GCL consists of
bentonite

between layers


of Geotextile


“Self Healing” Properties


Benefits


Reduced berm width


Homogenous, uniform installation


Less fill and haul trucks required


Sand and Clay fill geotechnical properties testing complete


GCL FS for Bob
-
2 Normal head conditions 1.50, High head
1.41


GCL/ Backfill placement



Backfill material Sandy Lean Clay


Clay material placed on inside slope compacted in lifts
to 90% standard Proctor


GCL placed on top
-

then covered by 2
-
3 ft additional
compacted clay


Existing berm will be dry and compacted from
additional weight



BOB
-
2 GCL Normal Head

BoRit Asbestos Superfund Site

Ambler, PA

January 2014

Legend


FS= 1.500

Pennsylvania

BoRit

Layer

Material

γ (
汢猯晴
3
)

φ(
°
)

Cohesion (lbs/ft
2
)

Region 1

Sandy SILT (Drained)

115

22

0

Region 2

Poorly Graded SAND (Drained)

120

33

0

Region 3

Bedrock

N/A

N/A

N/A

Region 4

N/A

N/A

N/A

N/A

Region 5

Clean
Silty

Sand FILL (Drained)

115

34

0

Region 6

Dense Silty SAND (Drained)

125

34

0

Region 7

Loose Silty SAND (Drained)

115

29

0

Region 12

BACKFILL

110

30

0