BoRit Asbestos Superfund SiteRemedial Overview of USACE Reservoir Report

January 15, 2014

Jill Lowe, EPA Travis Fatzinger, USACE

BoRit Asbestos Superfund SiteOverview

USACE Report on BoRit ReservoirReservoir HydrologyBerm StabilityOptions Reviewed

BoRit Asbestos Superfund SiteUSACE 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 SiteUSACE Report

Hydraulics StudyTransducers – 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 LocationsBoRit Asbestos Superfund Site

Ambler, PA

Figure 3.1

August 2013

LegendMonitoring Well, Transducer

Monitoring Well, No Transducer

Staff Gauge, Transducer

Staff Gauge, No Transducer

Pennsylvania

BoRit

BoRit Asbestos Superfund SiteUSACE Report

Hydraulics Study ConclusionsReservoir

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 SiteUSACE 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 workKnown pipes likely filled in with sedimentation

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Zone of Weak Material in SW BermBoRit 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 BoringsContinuous Split Spoon SamplingAdvanced until bedrock refusal

Lab testing on SamplesIncluded sieve analyses, triaxial consolidated-

undrained, unconfined compression

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Locations of BOB-1, BOB-2, and BOB-3BoRit Asbestos Superfund Site

Ambler, PA

Figure 2.4

August 2013

Slope Stability Model

GeoStudio 2012Seep /WSlope /W

Survey Profiles

Soil Profiles

Lab Results

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BOB-2 Current Geometry High HeadBoRit Asbestos Superfund Site

Ambler, PA

Figure 4.5

August 2013

Legend

FS= 0.93

Pennsylvania

BoRit

Layer Material γ (lbs/ft3) φ(°) Cohesion (lbs/ft2)Region 1 Sandy SILT (Drained) 115 22 0Region 2 Poorly Graded SAND (Drained) 120 33 0Region 3 Bedrock N/A N/A N/ARegion 4 N/A N/A N/A N/ARegion 5 Clean Silty Sand FILL (Drained) 115 34 0Region 6 Dense Silty SAND (Drained) 125 34 0Region 7 Loose Silty SAND (Drained) 115 29 0

Current ConditionSlope Stability Results

Current Geometry

Boring Factor of Safety1

Normal Water Level

Factor of SafetyHigh 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

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BoRit Asbestos Superfund SiteUSACE Report

USACE Options to cover ACM and stabilize bermOption 1

Flatten exterior slope Add stability berm to exterior toe of slope (Wissahickon

side)Option 2

SheetpileOption 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 HeadBoRit Asbestos Superfund Site

Ambler, PA

Figure 4.8

August 2013

Legend

FS= 1.63

Pennsylvania

BoRit

Layer Material γ (lbs/ft3) φ(°) Cohesion (lbs/ft2)Region 1 Sandy SILT (Drained) 115 22 0Region 2 Poorly Graded SAND (Drained) 120 33 0Region 3 Bedrock N/A N/A N/ARegion 4 N/A N/A N/A N/ARegion 5 Clean Silty Sand FILL (Drained) 115 34 0Region 6 Dense Silty SAND (Drained) 125 34 0Region 7 Loose Silty SAND (Drained) 115 29 0

Region 12 BACKFILL 110 30 0

Proposed GeometrySlope Stability Results

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Proposed Geometry

Boring Factor of SafetyNormal with Fill

Factor of SafetyHigh Head with Fill

BOB-1 3.87 3.44

BOB-2 1.63 1.62

BOB-3 1.57 1.47

Option 3 with GCLSupplement clay fill with Geosynthetic Clay Liner (GCL)GCL consists of bentonite between layers

of Geotextile“Self Healing” PropertiesBenefits

Reduced berm widthHomogenous, uniform installationLess 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 placementBackfill material Sandy Lean ClayClay material placed on inside slope

compacted in lifts to 90% standard ProctorGCL placed on top- then covered by 2-3 ft

additional compacted clayExisting berm will be dry and compacted

from additional weight

BOB-2 GCL Normal HeadBoRit Asbestos Superfund Site

Ambler, PA January 2014

Legend

FS= 1.500

Pennsylvania

BoRit

Layer Material γ (lbs/ft3) φ(°) Cohesion (lbs/ft2)Region 1 Sandy SILT (Drained) 115 22 0Region 2 Poorly Graded SAND (Drained) 120 33 0Region 3 Bedrock N/A N/A N/ARegion 4 N/A N/A N/A N/ARegion 5 Clean Silty Sand FILL (Drained) 115 34 0Region 6 Dense Silty SAND (Drained) 125 34 0Region 7 Loose Silty SAND (Drained) 115 29 0

Region 12 BACKFILL 110 30 0