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Remedial Overview of USACE Reservoir Report January 15, 2014 Jill Lowe, EPA Travis Fatzinger, USACE.

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Presentation on theme: "Remedial Overview of USACE Reservoir Report January 15, 2014 Jill Lowe, EPA Travis Fatzinger, USACE."— Presentation transcript:

1 Remedial Overview of USACE Reservoir Report January 15, 2014 Jill Lowe, EPA Travis Fatzinger, USACE

2 BoRit Asbestos Superfund Site Overview USACE Report on BoRit Reservoir Reservoir Hydrology Berm Stability Options Reviewed

3 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

4 BoRit Asbestos Superfund Site USACE Report Hydraulics Study Transducers – March-August transducers in wells MW-01a, MW-02, and MW-03 1 in Reservoir Transducer – July 2013-August transducer in background well, MW-07

5 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

6 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

7 BoRit Asbestos Superfund Site USACE Report

8 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

9 Zone of Weak Material in SW Berm BoRit Asbestos Superfund Site Ambler, PA Figure 2.2 August 2013

10 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

11 Locations of BOB-1, BOB-2, and BOB-3 BoRit Asbestos Superfund Site Ambler, PA Figure 2.4 August 2013

12 Slope Stability Model GeoStudio 2012 Seep /W Slope /W Survey Profiles Soil Profiles Lab Results 12

13 BOB-2 Current Geometry High Head BoRit Asbestos Superfund Site Ambler, PA Figure 4.5 August 2013 Legend FS= 0.93 Pennsylvania BoRit LayerMaterialγ (lbs/ft 3 )φ(°)Cohesion (lbs/ft 2 ) Region 1Sandy SILT (Drained) Region 2Poorly Graded SAND (Drained) Region 3Bedrock N/A Region 4 N/A Region 5Clean Silty Sand FILL (Drained) Region 6Dense Silty SAND (Drained) Region 7Loose Silty SAND (Drained)

14 Current Condition Slope Stability Results Current Geometry BoringFactor of Safety 1 Normal Water Level Factor of Safety High Head Level BOB BOB BOB Factor of Safety = material strength/design load. USACE target is

15 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 berms cross-sectional width Flatten interior slope to 3H:1V =18° Material stable to 30° resulting in Factor of Safety of 1.7

16 BOB-2 Proposed Geometry Normal Head BoRit Asbestos Superfund Site Ambler, PA Figure 4.8 August 2013 Legend FS= 1.63 Pennsylvania BoRit LayerMaterialγ (lbs/ft 3 )φ(°)Cohesion (lbs/ft 2 ) Region 1Sandy SILT (Drained) Region 2Poorly Graded SAND (Drained) Region 3Bedrock N/A Region 4 N/A Region 5Clean Silty Sand FILL (Drained) Region 6Dense Silty SAND (Drained) Region 7Loose Silty SAND (Drained) Region 12BACKFILL

17 Proposed Geometry Slope Stability Results 17 Proposed Geometry BoringFactor of Safety Normal with Fill Factor of Safety High Head with Fill BOB BOB BOB

18 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

19 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

20 BOB-2 GCL Normal Head BoRit Asbestos Superfund Site Ambler, PA January 2014 Legend FS= Pennsylvania BoRit LayerMaterialγ (lbs/ft 3 )φ(°)Cohesion (lbs/ft 2 ) Region 1Sandy SILT (Drained) Region 2Poorly Graded SAND (Drained) Region 3Bedrock N/A Region 4 N/A Region 5Clean Silty Sand FILL (Drained) Region 6Dense Silty SAND (Drained) Region 7Loose Silty SAND (Drained) Region 12BACKFILL


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