New Jersey Department of Environmental Protection Site Remediation Program Ground Water Technical Guidance: Site Investigation Remedial Investigation Remedial Action Performance Monitoring April 3, 2012 Table of Contents Intended Use of Guidance Document....................................................................................................................... iii 1.0 Purpose ..................................................................................................................................................................1 1.1 Document Overview .........................................................................................................................................1 2.0 Site Investigation of Ground Water ....................................................................................................................2 2.1 Overview.............................................................................................................................................................2 2.2 Ground Water Remediation Standards...........................................................................................................2 2.3 Considerations for When a Site Investigation of Ground Water is Necessary............................................2 2.4 Cross Contamination of Ground Water ..........................................................................................................3 2.5 Ground Water Site Investigation Sampling Locations...................................................................................3 2.5.1 Horizontal Biasing of Ground Water Samples .............................................................................................3 2.5.2 Vertical Biasing of Ground Water Sample Locations for LNAPL Contaminants ........................................4 2.5.3 Vertical Biasing of Ground Water Sample Locations for DNAPL Contaminants........................................4 2.5.3 AOC Specific Ground Water Sampling........................................................................................................5 2.6 Soil Logging and Field Screening.....................................................................................................................5 2.7 Ground Water Sampling Methods and Analyses............................................................................................5 2.8 Determination of Off-Site Contribution of Ground Water Contamination .................................................5 2.8.1 Ground Water Investigation to Demonstrate Off-site Contribution..............................................................6 2.8.2 Ground Water Remediation Standard Based on Background Contamination ..............................................6 2.9 Determination of Natural Background............................................................................................................7 3.0 Remedial Investigation of Ground Water ...........................................................................................................8 3.1. Overview............................................................................................................................................................8 3.1.2. The Triad Approach...................................................................................................................................10 3.1.3. Conceptual Hydrostratigraphic Model.......................................................................................................10 3.1.3.1 Generic Conceptual Hydrostratigraphic Models for the Unconsolidated Formations and Sediments of NJ.....................................................................................................................................................................11 3.1.3.1.1 Generic Hydrostratigraphic Model for Coastal Plain Sediments ..................................................11 3.1.3.1.2 Generic Hydrostratigraphic Model for Glacial Sediments............................................................12 3.1.3.1.3 Generic Hydrostratigraphic Model for Unconsolidated Sediments Overlying Bedrock...............12 3.1.3.2. Generic Conceptual Hydrostratigraphic Models for the Bedrock Regions of NJ ..............................13 3.1.3.2.1 Generic Hydrostratigraphic Model for the Newark Basin ...........................................................14 3.1.3.2.2 Generic Hydrostratigraphic Model for Paleozoic Sedimentary Bedrock.....................................16 3.1.3.2.3 Generic Hydrostratigraphic Model for Crystalline Bedrock........................................................16 3.1.3.3 Literature Review ................................................................................................................................17 3.1.3.4 Perform Field Reconnaissance of the Site and Surrounding Area .......................................................19 3.2 Delineation of NAPL and Sources of Ground Water Contamination........................................................21 3.2.1 Development of a Conceptual Hydrostratigraphic Model of Source Areas..............................................21 3.2.2 Unsaturated Zone Sources of Ground Water Contamination.....................................................................21 3.2.3 Saturated Zone Sources of Ground Water Contamination.........................................................................21 3.2.3.1 Back Diffusion of Contaminants from Low Permeability Zones.........................................................22 3.2.3.2 Free and Residual Product ..................................................................................................................22 3.2.3.2.1 Field Methods for Detecting Free and Residual Product.......................................................22 3.2.3.2.1.1 Soil Field Screening Techniques...........................................................................................24 3.2.3.2.1.2 Geophysical Techniques .......................................................................................................24 3.2.3.2.1.3 Vertical Profiling Techniques ...............................................................................................24 3.2.3.2.1.4 Soil Gas Surveys...................................................................................................................25 3.2.3.2.2 Residual Product Presence Inferred from Soil and Ground Water Analytical Data ....................25 3.2.4 Interim Remedial Measure.........................................................................................................................25 3.3 Characterization of Unconsolidated Aquifers..............................................................................................26 3.3.1 Remedial Investigation Approach in Unconsolidated Aquifers..................................................................26 3.3.1.1 Determination of ground water flow direction.....................................................................................26 3.3.1.2 Delineation of Contaminant Plume using Transects, Vertical Profiling and Real Time Analysis.......27 3.3.1.3 Installation of Monitoring Well Network ............................................................................................29 3.3.1.4 Determination of Site Specific Hydraulic Properties...........................................................................29 3.3.1.5 Update the Hydrostratigraphic Model..................................................................................................29 i 3.3.2 Ground Water Classification Exception Area.............................................................................................30 3.4 Characterization of Bedrock Aquifers..........................................................................................................31 3.4.1 Remedial Investigation Approach for Bedrock Aquifers...........................................................................31 3.4.2 Investigating New Contaminated Bedrock Sites .......................................................................................31 3.4.2.1 Implement initial test drilling program ...............................................................................................31 3.4.2.2 Conduct borehole geophysical logging and other downhole characterization tests............................32 3.4.2.3 Conduct vertical flow measurements and sampling............................................................................33 3.4.2.4 Conduct packer tests ...........................................................................................................................34 3.4.2.5 Synthesize the testing results into the initial site-specific hydrogeologic model................................34 3.4.2.6 Convert the test holes into monitoring wells ......................................................................................35 3.4.2.7 Update Conceptual Hydrostratigraphic Model and Complete Plume Delineation..............................35 3.4.3 Investigating Contaminated Bedrock Sites with Existing Monitoring Wells ............................................36 3.4.4 Characterize the Ground Water Contamination Source Zone....................................................................37 3.4.5 Ground Water Classification Exception Area.............................................................................................38 3.4.6 Fractured Rock