MONITORED NATURAL ATTENUATION (MNA) FOR SITE CLEANUP: APPROPRIATE TOOL OR EASY WAY OUT? Charles Newell, Ph.D., P.E. David Adamson, Ph.D., P.E. GSI Environmental Inc. GSI Environmental Inc. Houston, Texas, USA Houston, Texas, USA [email protected] [email protected] ROAD MAP • Intro: Changing Paradigms and MNA Principles • Key Attenuation Processes  Biodegradation  Abiotic Processes  LNAPL source zone degradation processes  Other processes (immobilization, storage, dilution) • Field Techniques and Technologies  Groundwater sampling and analytical methods  Compound Specific Isotopes Analysis (CSIA)  Molecular Biological Tools (MBTs)  Natural Source Zone Depletion (NSZD) • Should MNA be Used? Data Analysis and Monitoring Tools  Data requirements, LTM, and statistics to understand MNA rates  Common Graphics and Calculations  Remediation Timeframe Calculations  Computer Models • Implementation Topics 3 SOURCE PARADIGM 1970s – early 1990s 4 SOURCE PARADIGM 1970s – early 1990s 5 PUMP AND TREAT THE PLUME Recovery Well Installation Well Screen Centralizer Wire-Wrap Well Screen Driller’s knee Sand- Driller’s Gravel helper Filter Pack 6