Bedrock Characterization Mottolo Pig Farm Superfund Site

Transcription

1 Bedrock Characterization Mottolo Pig Farm Superfund Site Andrew Drew Hoffman, PE NH Department of Environmental Services Acknowledgments GZA GeoEnvironmental (lead consultant) Hager-Richter (sub for geophysics) EPA, Region 1 NH Geological Survey (regional bedrock) USGS (geochemistry / arsenic expertise) 2 1

2 What s Ahead 3 Site Orientation & Defining the Problem TCE Investigation Geophysical Surveys 3D Model (Representation) Groundwater Hydraulics & Geochemical Studies Results Questions & Discussion Site Location & Orientation Randy Lane North 4 2

3 Site Features & EPA Cleanup Actions FORMER DRUM DISPOSAL AREA 5 SHALLOW BEDROCK MWs SHALLOW BEDROCK FLOW TO BROOK A Former Piggery Buildings EPA s 3 rd Five-Year Review Completed August 2008 Questioned the Protectiveness of Remedy Increasing concentrations of TCE & arsenic in several on-site monitoring wells Increased residential development 6 3

4 2009 Expanded Residential Well Sampling 7 Residential sampling began in TCE Concentrations Detected above DW standard Non-Detect Detected below standard 8 4

5 Arsenic Concentrations 9 Unanswered Questions 1. Does the TCE found in residential wells originate from the Mottolo Site? 2. Any of the arsenic Site-related? 3. Extent of remedy? 10 5

6 What s Ahead 11 Site Orientation & Defining the Problem TCE Investigation Geophysical Surveys 3D Model (Representation) Groundwater Hydraulic Studies Conclusions & Findings Lessons Learned & Options for Scale-Down Questions & Discussion Bedrock Groundwater Contours Brook A 12 6

7 13 What s Ahead Site Orientation & Defining the Problem TCE Investigation Geophysical Surveys Surface geophysical methods Borehole geophysical methods 3D Model (Representation) Groundwater Hydraulic Studies Conclusions & Findings Lessons Learned & Options for Scale-Down Questions & Discussion Geophysical Surveys Surface Geophysical Methods: Very Low Frequency Electromagnetics (VLF) Electromagnetic Induction - EM34 Earth Resistivity Imaging (ERI) Borehole Geophysical Methods: Optical Televiewer (OTV) Acoustic Televiewer (ATV) Fluid Temperature & Fluid Resistivity Heat Pulse Flow Meter (HPFM) Ambient & Pumped Conditions 14 7

8 Surface Geophysical Methods: VLF & EM34 Fracture Interpretation Former Drum Disposal Area N 15 Surface Geophysical Methods: Earth Resistivity Imaging Former Drum Disposal Area Perspective View Looking Northwest 16 8

9 Geophysically Logged Wells 17 Borehole Geophysical Logging Fracture & Flow Interpretation Blue Fracture Plane in 3D Model 18 9

10 3D Geophysical Conceptual Model North Former Drum Disposal Area Well or Borehole Logged by Hager-Richter or USGS Area of concentrated groundwater withdrawals 19 Perspective View Looking Northeast N Surface Traces of Modeled Fracture Planes Former Drum Disposal Area 20 10

11 What s Ahead 21 Site Orientation & Defining the Problem TCE Investigation Geophysical Surveys 3D Model (Representation) Groundwater Hydraulics & Geochemical Studies Results Questions & Discussion Pump Test Pumped from Site Well 30 gpm for First Two Days; 50 gpm Remaining Five Days Treated Extracted Water for VOCs and Arsenic Measured Groundwater Level Response at 27 Locations 22 11

12 Pump Test Drawdown Pumping well D Geophysical Conceptual Model With Pump Test Results Well with Immediate Drawdown Well with Delayed or No Drawdown Pumped Well MOT_MW-103 Former Drum Disposal Area Perspective View to the Southeast Looking Down-Dip Of Modeled Green Fracture Plane 24 12

13 Area 1 Remedial Area 25 Results Bedrock groundwater flow and contaminant migration largely influenced by a dominant set of fractures and pumping of residential wells TCE generally detected in wells intersecting the dominant bedrock fractures 26 Water line remedy addressed residences that were impacted or likely to be impacted 13

14 Results (continued) Predictions of plume contraction since of 25 former drinking water wells became additional site monitoring wells Have not detected site-related VOCs since pre-water line 27 Continued sampling of residential wells and site wells support remedy decision Lessons Learned Data from residential wells critical Multiple lines of evidence inform decisions 3D model can be kept simple to explain the primary bedrock fracture network Integration of multidiscipline team was key to decision making process 28 14

15 Questions and Discussion 29 15