Guidance On Natural Attenuation For Petroleum Releases January 2014 RR-614 Wisconsin Department of Natural Resources P.O. Box 7921, Madison, WI 53707 dnr.wi.gov, search “brownfield” ii TABLE OF CONTENTS PURPOSE .................................................................................................................................................................. IV APPLICABILITY AND LIMITATIONS............................................................................................................................... IV OTHER RELEVANT GUIDANCE DOCUMENTS ................................................................................................................ V DISCLAIMER ............................................................................................................................................................... V INTRODUCTION ........................................................................................................................................................... 1 SECTION 1 .................................................................................................................................................................. 3 SITE INVESTIGATION NEEDS ............................................................................................................................... 3 I. FORMATION OF A CONCEPTUAL MODEL ............................................................................................................. 3 II. IDENTIFY RECEPTORS ......................................................................................................................................... 4 A. Determine Location of Receptors ............................................................................................................. 4 B. Information Sources for Identifying Receptors ....................................................................................... 4 III. SOIL & GROUNDWATER CHARACTERIZATION .................................................................................................. 5 A. Source Zone Characterization .................................................................................................................. 6 B. Source Zone Contaminant Mass Distribution & Interim Measures ...................................................... 7 C. Groundwater Characterization ................................................................................................................ 7 D. Chemical/Physical Properties of the Contaminants ................................................................................ 9 IV. DETERMINING DISSOLVED PLUME BEHAVIOR ............................................................................................... 10 A. Methods to Define Behavior of a Dissolved Contaminant Plume ........................................................ 10 B. Interpretations of Plume Behavior ......................................................................................................... 13 V. CONDITIONS WHERE NATURAL ATTENUATION SHOULD NOT BE USED AS A SOLE REMEDY FOR GROUNDWATER CONTAMINATION ....................................................................................................................................................... 14 VI. SITE INVESTIGATION REPORT (NR 716.15) ................................................................................................... 15 SECTION 2 ................................................................................................................................................................ 17 DATA ANALYSIS FOR NATURAL ATTENUATION......................................................................................... 17 I. LINES OF EVIDENCE SUPPORTING NATURAL ATTENUATION ............................................................................... 17 A. Primary Line of Evidence – Decreasing Contaminant Trends ............................................................. 17 B. Secondary Line of Evidence – Trends in Geochemical Parameters ..................................................... 18 C. Third Line of Evidence – Microbial Studies and Other Analysis ........................................................ 18 II. DATA REQUIREMENTS ...................................................................................................................................... 18 III. PRIMARY LINE OF EVIDENCE – CONTAMINANT TREND ANALYSIS ................................................................... 19 A. Estimates of Contaminant Decay Rate in Groundwater ....................................................................... 19 B. Estimates of Contaminant Decay Rate in the Source Zone .................................................................. 20 IV. SECONDARY LINE OF EVIDENCE – TRENDS IN GEOCHEMICAL PARAMETERS................................................... 21 A. Assessing Geochemical Trends ................................................................................................................ 21 B. Assimilative Capacity ............................................................................................................................... 21 C. Screening Models ..................................................................................................................................... 22 V. THIRD LINE OF EVIDENCE – MICROBIAL AND OTHER STUDIES ........................................................................... 22 VI. PROGRESS REPORTS ..................................................................................................................................... 23 VII. REMEDIAL ACTION OPTIONS REPORT OR CLOSURE REPORT .......................................................................... 23 SECTION 3 ................................................................................................................................................................ 24 NATURAL ATTENUATION MONITORING RECOMMENDATIONS ........................................................... 24 I. GEOCHEMICAL PARAMETERS AS INDICATORS OF NATURAL ATTENUATION .......................................................... 24 A. Introduction .............................................................................................................................................. 24 B. Data Quality.............................................................................................................................................. 24 II. METHODS OF COLLECTING & ANALYZING SAMPLES FOR GEOCHEMICAL PARAMETERS ...................................... 25 A. Well Purging ............................................................................................................................................. 26 i B. Sample Methodology for Geochemical Parameters .............................................................................. 27 C. Quality Control Checks for Field Measurements .................................................................................. 30 III. MONITORING FOR CONTAMINANTS OF CONCERN .......................................................................................... 31 A. Data Quality.............................................................................................................................................. 31 B. Parameters & Methodology for Petroleum Contaminants ................................................................... 31 IV. MONITORING SCHEDULE .............................................................................................................................. 31 A. Recommended Monitoring Schedule ...................................................................................................... 31 B. Long Term Monitoring ............................................................................................................................ 32 V. DATA REPORTING ............................................................................................................................................. 32 SECTION 4 ................................................................................................................................................................ 34 REGULATORY REQUIREMENTS FOR SITE CLOSURE WHEN USING NATURAL ATTENUATION AS A REMEDIAL ACTION........................................................................................................................................... 34 I. SITE CLOSURE CRITERIA ................................................................................................................................... 34 A. Summary of NR 726.05(6)(a)1. to 5. Requirements, Source Zone & Interim Actions Completed .... 34 B. Satisfying the Requirements of NR 726.05(6)(a) and (c) Related to Demonstrating Effectiveness of Natural Attenuation Processes................................................................................................................ 34 C. Satisfying the Requirements of NR 726.05(6)(b) Related to Meeting NR 140 Standards within a Reasonable Period of Time ..................................................................................................................... 35 D. Continuing Obligations ............................................................................................................................ 36 II. NR 726, CASE CLOSURE REQUEST & REPORT ................................................................................................... 37 REFERENCES