Remedial Overview of USACE Reservoir Report

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