Groundwater Resources Association of California Web Seminar

  • by BPC Staff
  • on May 28, 2013

o f    C a l i f o r n i a

Presents a GRACast Web Seminar

1,4-Dioxane – the Emerging Contaminant that Keeps On Emerging

Thomas Mohr
Senior Hydrogeologist
Santa Clara Valley Water District

Tuesday, June 4, 2013
12:00 pm to 1:30 pm, Pacific Daylight Time (GMT-07:00)

Early Registration (by May 29) is $50 for Members* and $75 for Non-Members*
Registration after May 29 is $75 for Members* and $100 for Non-Members*

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1,4-Dioxane has been an often-overlooked yet ubiquitous contaminant found at solvent release sites, landfills, and in factory effluent. Currently, drinking water utilities are carrying out the Unregulated Contaminants Monitoring Requirements 3 (UCMR3), which includes testing for 1,4-dioxane using EPA Method 522 with a reporting limit of 0.3 µg/L or lower. The number of public and domestic well test results showing detections of 1,4-dioxane has been steadily increasing. There is growing awareness that this probable carcinogen is widespread and problematic. The hydrophilic nature of 1,4-dioxane makes it relatively immune to conventional treatment technologies commonly used for chlorinated solvents, and makes it the fastest moving contaminant found at solvent release sites and the first to arrive at municipal or domestic supply wells. Given that 1,4-dioxane was added as a stabilizer for many grades of 1,1,1-trichlorothane (TCA), and that more than 600,000 tons of TCA were used at more than 6,000 facilities nationwide, the already high frequency of 1,4-dioxane detection in drinking water is expected to increase further as more UCMR3 results come in. The market for 1,4-dioxane investigation, laboratory, and remediation services is growing, and there have been many recent and important technical advances in 1,4-dioxane remediation. The regulatory policy for 1,4-dioxane cleanup levels and drinking water advisory levels varies widely among U.S. states and countries around the world. In 2010, US EPA published a toxicological review of 1,4-dioxane recommending a steeper cancer slope factor, effectively lowering the drinking water advisory level for 1,4-dioxane. Accordingly, California and Illinois lowered their drinking water guidance levels to 1 µg/L, while Massachusetts set their guidance at 0.3 µg/L.

The Groundwater Resources Association of California is proud to present a 90-minute webinar on this important and challenging contaminant by Thomas Mohr, on June 4th at 12 PM Pacific Standard Time (7:00p GMT). The topical agenda for the webinar is listed below.

Outline for the 1,4-Dioxane Webinar by Thomas Mohr:

1. Contaminant Archeology of 1,4-Dioxane: Uses and Occurrence

• The Role of Solvent Stabilizers in Chlorinated Solvents
• Direct Uses of 1,4-Dioxane and its Occurrence in By-products
• Occurrence of 1,4-Dioxane in Recycled Water and Drinking Water

2. Chemical Properties of 1,4-Dioxane Governing Fate and Transport

• Chemical Structures of 1,4-Dioxane and Physical and Chemical Properties of 1,4-Dioxane
• Fate and Transport of 1,4-Dioxane
• Overview of Intrinsic Biodegradability: Bacterial Strains, Direct Metabolism, Co-Metabolism, Fungi and Evidence for Occurrence Under Ambient Conditions

3. Laboratory Analysis of 1,4-Dioxane – Challenges and Solutions

• Comparison of Laboratory Methods for 1,4-Dioxane Analysis

4. Field Examples: Plume Dynamics and 1,4-Dioxane Treatment Challenges and Costs

• Relative Rates of Migration
• Consequences of Late Discovery of 1,4-Dioxane at a Solvent Release Site
• Consequences of 1,4-Dioxane in Recycled Water
• 1,4-Dioxane remediation in the unsaturated zone

5. Myth-busting: Common misconceptions about 1,4-Dioxane

• 1,4-Dioxane Was a Stabilizer for 1,1,1-TCA and “other chlorinated solvents”
• 1,4-Dioxane Occurs Naturally in Chicken, Shrimp, Tomatoes, and other Foods
• There’s No Federal/State Standard – the Regulator Won’t Require 1,4-Dioxane Cleanup
• 1,4-Dioxane is a Good Candidate for Natural Attenuation
• The Monitoring Well Network Designed to Delineate the Chlorinated Solvent Plume is Sufficient to Characterize 1,4-Dioxane
• And more . . .  send your questions in advance.

6. Q&A and Discussion


Thomas Mohr works at the Santa Clara Valley Water District as Senior Hydrogeologist where he manages county-wide groundwater monitoring and salt and nutrient management plans, and was previously the District’s Solvents and Toxics Cleanup Liaison. He was the principal investigator for the District’s Study of Potential for Groundwater Contamination from Past Dry Cleaner Operations in Santa Clara County, and was the District’s project manager on a major perchlorate case that impacted hundreds of domestic wells.

Mohr is the principal author of the book, “Environmental Investigation and Remediation: 1,4-dioxane and Other Solvent Stabilizers in the Environment”, (Mohr/DiGuiseppi/Stickney) published by Taylor and Francis Group (CRC Press) in 2010. The book was the culmination of seven years of research and networking on the subject of 1,4-dioxane and other solvent stabilizers, and is now the leading reference on the subject, with copies housed in more than 100 university and corporate libraries in more than a dozen countries.

Mohr continues his work on 1,4-dioxane independently from his District employment and has given many conference presentations and webinars on 1,4-dioxane. His most recent publication was a 2012 article in EPA’s Technology News and Trends on point-of-entry treatment systems (POETS) to remove 1,4-dioxane from domestic wells. Mohr has been retained as an expert witness for several 1,4-dixoane groundwater contamination court cases in California and Florida. He has published on improvements to laboratory methods for 1,4-dioxane analysis, perchlorate isotope forensics, leveraging stable isotopes of water for investigating origins of nitrate contamination, anaerobic biodegradation of gasoline, and other topics. Mohr was the statewide President of the Groundwater Resources Association of California in 2006 and 2007 and served on GRA’s Board of Directors for 10 years.

Register For This Event —

* This GRACast will use a conference call for audio and WebEx to display the presentation slides. Each registration is allowed access via one phone line and one log in to the WebEx module. More than one person may participate per registration by using a shared computer screen and speaker phone. GRA reserves the right to invoice those individuals and/or organizations that are logged in or connected from telephone numbers that don’t correspond to a paid registration.

GRA is dedicated to resource management that protects and improves groundwater
supply and quality through education and technical leadership.

621 Capitol Mall, 25th Floor * Sacramento, CA 95814 * Ph: 916-446-3626 * Fx: 916-442-0382 *