Webinar Series on Complex Sediment Sites – Innovative Approaches to Source Identification and Cost Allocation

News & Events

March 14, 2019

Please join Gradient scientists for a two-part webinar series highlighting some of our recent environmental sciences work.  Each series contains three presentations by Gradient scientists covering technical aspects of source identification and allocation at sediment sites, including:

  • Weathering effects on PAH sources
  • Allocating PCB sources using chromatogram cumulative response curves
  • Approaches for evaluating relative contaminant contribution at multi-contaminant sites
  • Evaluating naturally occuring and anthropogenic background in an urban watershed 

Several applications for identifying and quantifying contaminant sources that are being used for remedial investigation and decision-making at complex sites will be highlighted.


Register for each webinar:

Session 1: Wednesday, March 27, 2019 at 2:00PM ET

Session 2: Wednesday, April 3, 2019 at 2:00PM ET


Details on Session 1: March 27, 2019 from 2-3PM ET


Is Urban Background an Urban Myth?
Speaker:  Tim Verslycke, Ph.D., Principal

Identification of appropriate background concentrations can be a major challenge in the selection of protective, reasonable, and implementable cleanup goals at contaminated sediment sites.  Background is also often a key consideration in contaminated sediment site allocation.  In recognition of this, sediment background has been the focus of several recent federal and state guidance documents.  This presentation will discuss key issues and describe successful approaches for addressing background in risk-based remedial decision making and allocation at contaminated sediment sites. 


Source Allocation Of PCBs Derived from Quantile Analysis of Cumulative Response Curves Combined with Monte Carlo Analysis
Speaker:  Eric Butler, Ph.D., Principal

Hydraulic fluid containing PCBs was discharged from two facilities into the same stream. Chromatograms from the two source areas and the receptor area (the stream) were converted into families of cumulative response curves, one family of curves for each of the three areas. Use of the complete chromatograms obviated any difficulties that might have otherwise arisen from differing interpretations of individual sample chromatograms by laboratory analysts. Quantile regression analysis was performed to enable mathematical analysis of the families of cumulative response curves. Subsequent Monte Carlo analysis enabled conclusions to be drawn as to the relative contribution of the two sources to the stream.


Understanding Background Conditions as a First Step in Developing Remediation Goals in Mined Areas
Speaker:  Karrie Radloff, Ph.D., Senior Environmental Engineer

Remedy selection is particularly challenging for mined areas where the complex geology associated with the mine makes it difficult to distinguish impacts from background (both of non-mineralized and mineralized areas).  We present an approach for distinguishing non-mineralized background from mineralized background from impacted groundwaters. Understanding both types of background conditions, and how they differ from impacted conditions, was essential for the development of remediation alternatives and achievable risk-based clean up goals.



Details on Session 2: April 3, 2019 from 2-3PM ET

Diagenetic Magnification of Persistent Organic Pollutants from Combined Sewage Overflow Sources
Speaker:  Caroline Tuit, Ph.D., Senior Environmental Chemist

Combined sewer overflows (CSOs) are a high-volume, organic-rich, relatively low concentration source of contaminants to sediments, but it can be difficult to estimate their impact. Diagenetic magnification, or the differential weathering of organic matter and contaminants from CSOs, can alter contaminant concentrations preserved in the sediment. Depending on the site specific conditions, analyses of end of the pipe CSO samples may not fully represent potential CSO impacts to the sediment.

Incorporation of a Chemical Weathering Model in Sediment Source Apportionment Models
Speaker:  Jeffrey Rominger, Ph.D., Senior Environmental Engineer

Contaminated sediment sites often contain chemical contributions potentially spanning decades from multiple parties.  Over time, weathering processes can drastically alter chemical fingerprints in the sediments. However, typical forensic and source apportionment analyses often assume that chemical fingerprints remain static and unchanged over time.  In this work, Dr. Rominger will show how chemical weathering models can be incorporated into the forensic analysis portion of sediment cost allocations.


Quantitative Methods for Allocating Multiple Contaminants in Sediments
Speaker:  Kurt Herman, M.Eng., P.G., Principal

Urban sediments are often impacted by multiple contaminants from multiple legacy and ongoing sources. One common issue in cost allocation proceedings is finding a quantitative method of allocating sediment impacts among the various contaminants. This presentation will discuss quantitative methods for doing so.