April 2017 Presented by Roux Associates Phase I Site - PowerPoint PPT Presentation

April 2017 Presented by Roux Associates

Phase I Site Characterization Objectives  Evaluate the conditions at all Site features  Refine the list of COPCs that require further investigation  Refine the understanding of groundwater flow and groundwater quality beneath the Site  Develop a more detailed understanding of the depths, thicknesses and extents of the various hydrogeologic units  Develop data to support the preparation of the Baseline Risk Assessment Work Plan

Site Features Site Features Map

Summary of Field Activities April 2016 - September 2016 Site Reconnaissance  Pre-Intrusive Activities – Geophysical Survey / Soil Gas Survey / GPR Utility  Mark outs Drilling program   Completion of 95 soil borings  Installation of 44 new monitoring wells Asbestos Landfill exploratory test pitting  Test pitting of the borrow pit area  Sampling of various media including soil, groundwater, surface water,  sediment, and soil gas Collection of over 700 samples with varying analyses 

Phase I Investigation Locations

Phase I Site Characterization Drilling Program 95 locations completed to 12 feet below  land surface utilizing Geoprobe drilling technology 44 monitoring well locations completed to  varying depths utilizing Sonic drilling technology  Deepest drilling depths were 300 ft-bls  Wells installed at the water table and deeper 43, 32-point incremental composite soil  samples from grid cells utilizing geoprobe drilling technology

Hydrogeology  Upper Hydrogeologic Unit  Glacial outwash and alluvium  Coarse, higher permeability  Below Upper Hydrogeologic Unit  Glacial Till – varying sizes (gravel, sand, silt, clay)  Stiff, tight, lower permeability  Geologic cross Sections to review hydrogeology in two dimensions

Example Geologic Cross Section Up Upper er Hydr droge ogeolo ologic ic Un Unit Glac acia ial l Till ll Bedr droc ock – Teak akettle tle Mountain tain

Groundwater Flow  Groundwater flow is interpreted based on depth to groundwater measured within Site monitoring wells  Groundwater elevations measured on August 30, 2016 and November 29, 2016  Both gauging events indicate that groundwater flow is south-southwest towards the Flathead River

Potentiom iometri ric Surface ace Co Contour our Ma Map Augus gust 30, 2016

Phase I Site Characterization Sampling Program More than 400 soil samples collected across multiple  intervals during drilling:  Surface – 0 - 0.5 ft-bls  Shallow – 0.5 - 2 ft-bls  Intermediate Depth – 10 -12 ft-bls  Below Water Table – Varying depths depending on depth of water 60 Groundwater samples and 22 surface water  samples collected during Round 1 of sampling 12 sediment samples  • Cyanide • PCBs • Fluoride • Pesticides • Metals • Total Organic Carbon • SVOCs • Geotechnical parameters • VOCs

Soil Sampling Results Summary  Cyanide concentrations only exceeded the USEPA Industrial RSL in less than 1% of all Site- wide soil samples.  Fluoride concentrations did not exceed the USEPA Industrial RSL in any soil samples.  SVOCs (primarily PAHs) were detected across the Site, most frequently in surface soil samples.  PAHs at concentrations that exceeded the USEPA Industrial RSLs were primarily focused around the Main Plant and operational areas of the Site.

Example e Soil Thematic ic Ma Map Benzo zo(a (a)ant )anthracene hracene in Surface ce Soil

Groundwater Sampling Results Summary  Highest concentrations of cyanide and fluoride were observed immediately downgradient of West Landfill / Wet Scrubber Sludge Landfill, suggesting these landfills are the source  Iso-concentration maps show elevated concentrations are directed towards Flathead River (i.e., follow groundwater flow paths)  Concentrations are non-detect next to Aluminum City

Concentrations oncentrations of Cyan anide ide in Groundw undwat ater er

Concentr oncentrations ations of Flu luoride oride in Groundw undwat ater er

Surface Water Results Summary  Cyanide concentrations exceed screening levels in the Backwater Seep Sampling Area – historically permitted as part of the MPDES program  One detection of cyanide in Cedar Creek – requires additional evaluation  No exceedances of fluoride in any samples

Example e Surface ace Water Thematic ic Ma Map Cya Cyanide ide in Surface ace Water

Sediment Results Summary  Sediment was not present at most surface water locations in Flathead River and Cedar Creek Reservoir Drainage Overflow Ditch  High velocity flow environment limits sediment deposition  Cyanide and PAHs detected in samples from North Percolation Ponds and Backwater Seep Sampling Area  Sediment results evaluated in Screening Level Ecological Risk Assessment (SLERA)

Example e Sediment ent Thematic ic Ma Map Cya Cyanide ide in Sediment ent

Next Steps  Round 3 of groundwater/surface water sampling Underway  Round 4 of groundwater/surface water sampling scheduled to begin June 2017  Preparation of Baseline Risk Assessment Work Plan and Baseline Ecological Risk Assessment Work Plan  Phase II Sampling and Analysis Plan at end of 2017  Phase II Investigation in Summer 2018

Complete? Remedial Investigation/ Feasibility Study Task Schedule Estimated Completion Dates AOC is executed November 30, 2015 Jan – March 2016 Project Planning / Subcontractor Procurement Site Reconnaissance / Geophysical Survey / Soil Gas Screening April 2016 Sampling and Analysis Plan Addendum May 2016 May – September 2016 Drilling Program September – October 2016 Groundwater Sampling Event #1 Draft Phase I Site Characterization Data Summary Report February 2017 Draft Screening Level Ecological Risk February 2017 Assessment Report Baseline Risk Assessment Work Plans 3 rd Quarter 2017 Phase II Site Characterization Field Program 3 rd Quarter 2018 Phase II Data Summary Report 1 st Quarter 2019 3 rd Quarter 2019 Baseline Risk Assessment 1 st Quarter 2020 Final Remedial Investigation Report 3 rd Quarter 2020 Feasibility Study Work Plan 1 st Quarter 2021 Feasibility Study Report Submitted to EPA

Questions?