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Wednesday, May 24, 2017

Chlorinated Solvents and Sinking Plumes

Posted by: James King, Ph.D., LPG - Vice President of Operations on Wednesday, May 24, 2017 at 12:00:00 am

In their pure form, chlorinated solvents are dense non-aqueous phase liquids (DNAPLs) that are, by definition, heavier than water. So, plumes of chlorinated solvents dissolved in groundwater must sink, right? I’ve had many conversations over the years where this claim was made, and I always inwardly cringed a bit. Let’s take a closer look at it.

The density of water is a function of its temperature and the amount of dissolved matter it contains.  The presence of dissolved substances in groundwater can increase its density under certain conditions. For our discussion, we’ll assume the temperature of shallow groundwater varies seasonally within a narrow range, which allows us to focus on density differences related only to the dissolved load in groundwater.

Laboratories report analytical results in either milligrams per liter (mg/L - the mass of solute per 1 liter of water) or parts per million (ppm - the mass of solute per the mass of 1 liter of water). These same relationships hold for micrograms per liter (µg/L) and parts per billion (ppb). We typically assume the two sets of units are equivalent, which is true for the range of concentrations we usually see during environmental investigations. However, the equivalency between these two unit sets is based on the assumption that 1 liter of water weighs 1 kilogram (K), or unit density. For you geeks, this assumption is strictly true only for pure water at 3.89ºC, but ignoring this level of scientific “purity” doesn’t affect our discussion.

The error introduced by assuming unit density isn’t greater than any other type of analytical errors until the concentration of dissolved matter in water exceeds about 7,000 mg/L1 (for comparison, the dissolved load of naturally occurring inorganic salts in groundwater in Indiana is usually 500 to 1,000 mg/L). For concentrations greater than 7,000 mg/L, density starts becoming a factor, and a correction for density should be applied when converting from mg/L to ppm, or vice versa. We can extend this thought to state that the amount of dissolved matter in a plume of contaminated groundwater must be at least, and probably greater than, 7,000 mg/L before the density contrast between the body of contaminated groundwater (a “plume”) and the surrounding groundwater is sufficient to create a density gradient that could cause the plume to sink or “dive” within the flow system.

Let’s consider the aqueous solubilities (the maximum amount of a substance that can be dissolved in water) of the common chlorinated compounds we deal with every day – tetrachloroethene (PCE), 206 mg/L; trichloroethene (TCE), 1,280 mg/L; and 1,1,1-trichloroethane (TCA), 1,290 mg/L.2 I think you see where this is going. Based on these solubility limits, not enough of any of these compounds can dissolve from a pure-phase product source into groundwater to create a plume that is denser than the surrounding groundwater. Nor does the fact that the solute is derived from a dense chlorinated compound make any difference.  To claim otherwise is to believe, for example, that 10 mg of TCE dissolved in 1 liter of groundwater (10 mg/L) is denser than 10 mg of sulfate (or any other solute) dissolved in a liter of groundwater – 10 mg is 10 mg, regardless of the substance.

So, how did groundwater 60 feet directly beneath my dry cleaner site become contaminated with PCE, you may ask? Only a few explanations are plausible. Unless a nearby pumping well has drawn the PCE downward within the flow system, the most likely cause is that PCE in pure-phase product (DNAPL) form has moved downward beneath the site and created a vertical source column that has dissolved into the groundwater. Vertical dispersion may also occur as a plume moves away from a source, and a plume may “dive” when vertical recharge from overlying soils or strata pushes it deeper into the flow system, but these are typically shallow phenomena, neither is related to plume density, and both would affect plumes of any dissolved substance.

So, with a little basic physics and chemistry, we’ve debunked the misconception that plumes of dissolved chlorinated compounds in groundwater dive or sink as a result of their perceived greater density.  Unless the laws of physics are repealed, we have to rely on them to explain what we observe – part of the process of developing conceptual site models that assist us in accurately characterizing and remediating contaminated sites.

1Hem, J.D., 1985, Study and Interpretation of the Chemical Characteristics of Natural Water, US Geological Survey Water-Supply Paper 2254, 3rd Ed. (

2US EPA, 2016, Regional Screening Level (RSL) Chemical-specific Parameters Supporting Table May 2016. (

Wednesday, April 26, 2017

Top 10 Reasons Why Wilcox is the Best Place to Work!

Posted by: Holly Cooper on Wednesday, April 26, 2017 at 12:00:00 am

Wilcox is in the midst of one of the most exciting times in our history. After more than 20 years of continued growth, in offices we had vastly outgrown, we decided to move to a brand new state of the art facility in downtown Speedway, right across from the Indianapolis Motor Speedway (IMS).  

We have long been a part of the revitalization of Speedway, which is continuing to grow and bringing in exciting new businesses that are strengthening the area and making it one of the best neighborhoods in Marion County.

The transformation should be exciting to watch, and is certainly a big step in our continuing growth. We are excited to have an office that measures up to the talent at Wilcox, which sets the stage for our future. I highly recommend you take some time to check out this up and coming neighborhood.

Now…in light of our recent move, check out the top ten reasons why Wilcox is the best place to work!

1. Our beautiful new office… everything is shiny and new!


2. We have an amazing view of IMS. Even if you’re not a race fan, you can’t help but marvel at the view.

3. We’re just steps away from several great lunch spots! Dawson’s, Bourbon & BBQ and Big Woods, and coming soon… Tacos & Tequila and O’Reilly’s Irish Pub!

4. Having access to nearby walking trails and an employee discount to the Speedway Walking and Running Club. Employee wellness is important to Wilcox. Our healthcare is great too!

5. The open/collaborative office environment. However, we have several private rooms if you need some quiet time to work alone.

6. Being a part of Speedway’s redevelopment efforts and getting to see the area transform. We’ve been working with Speedway for many years to improve the area, so moving here was a perfect fit for us.

7.  A front row seat and excellent parking for all of the events on Main Street. Speedway has a lot more to offer than just the IMS! There are monthly concerts and events right here on Main Street throughout the year!

8. Our AWESOME employee lounge which showcases restored original hardwood flooring, indoor and outdoor seating for 50 people, full kitchen, bar, media/gaming area and free gourmet coffee. I’m not sure how any of us will get any actual work done!


9. Our employee gatherings and events are a blast! Picnics, theme parties, holiday parties, team building, after-hours hangouts, and monthly birthday celebrations are some of the fun things we do throughout the year.

10. US! We have an amazingly talented and fun, diverse group of people…

Tuesday, March 7, 2017

New IDEM 2017 Screening Level Tables

Posted by: Scott Stoldt, CPG, LPG, PG on Tuesday, March 7, 2017 at 12:00:00 am

On an annual basis, IDEM compares its risk-based screening levels against the most recent updates the U.S. EPA applies to its own regional levels. Changes to state and federal screening and closure levels can affect environmental liabilities for companies across Indiana with respect to how the primary risk driving chemicals, specific industries or ongoing site characterizations could be affected, positively or negatively. Certain changes sometimes have significant ramifications. For 2017, however, most of the changes are relatively minor.

IDEM’s 2017 Screening Level Tables (Table A-6 and A-7), effective March 6, 2017, are now available on IDEM’s Screening and Closure Levels web page located at It is notable that updated Table A-6 include the same list of chemicals shown in the 2016 Table. In addition, updated Table A-6 also shows new screening levels for the following 4 chemicals: thallium selenite, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, and o-toluidine (also known as 2-methylaniline). Table A-7 (Recreational Soil Direct Contact Screening Levels) remain unchanged.

As with prior changes, there is a 6-month transition period, which ends this year on September 6, 2017. Per IDEM’s Remediation Closure Guide, however, 2016 screening and closure levels remain applicable if a remediation or corrective action work plan is submitted by a responsible party during the transition period. After the transition period has ended, 2017 screening and closure levels become enforced.

Wilcox Environmental Engineering continually monitors ever-changing regulations at both the state and federal levels. Prompt awareness permits us to analyze changes for our clients and thus maximize the benefits of positive change, or conversely, minimize the impact of negative change to their specific environmental liabilities.

Monday, February 20, 2017

Basic Risk Assessment Concepts

Posted by: James M. King, Ph.D., LPG on Monday, February 20, 2017 at 12:00:00 am

The Indiana legislature’s passing of House Enrolled Act 1162 in April 2009 and IDEM’s adoption of the Remediation Closure Guide (RCG) in March 2012 put Indiana back on track for using the risk-based approaches for site closures that were more common before the previous Risk Integrated System of Closure (RISC) guidance took effect in early 2001. These changes restored our flexibility to use site-specific information to evaluate potential health risks associated with exposure to site contaminants.

Exposure risks can be evaluated and managed using several approaches, either singly or in combination. In order of increasing complexity, these are: 

  • Comparing contaminant concentrations to pathway-specific Screening Levels (SLs),
  • Using site-specific qualitative and quantitative “lines of evidence”,
  • Developing risk-management strategies (institutional or engineering controls) to reduce or eliminate exposures, and
  • Comparing contaminant concentrations to calculated site- and pathway-specific screening levels or remediation objectives developed through health-based risk assessments and standard risk equations. 

This article focuses on the last option – health-based risk assessments, which to the uninitiated may seem like a cryptic practice. Methods for assessing potential health risks from contaminated sites took root in the 1980s with the EPA’s Superfund program and have evolved into practical tools for guiding environmental remediation and risk-management decisions.

Experience with environmental remediations has shown that restoring contaminated sites to their pre-development conditions is often not possible, too costly, or even necessary in many cases. Risk assessments allow us to determine how much, or whether, remediation is necessary so that remediation costs can be balanced with acceptable reductions in exposure risk. Risk assessments: 

  1. Consider site-specific physical, chemical, and exposure conditions,
  2. Require little information beyond that collected during a thorough site characterization,
  3. May establish defensible, site-specific cleanup goals,
  4. Allow the scope and cost of cleanups to be defined in advance of actual remediation, and
  5. Often reduce cleanup costs by limiting remediation to higher-risk contaminants and/or site areas or by supporting the adoption of institutional and engineering controls to manage exposure risk rather than eliminating it. 


What Are Risk Assessments?

Risk assessments help us evaluate exposure to contaminants by answering these questions: 

  • Who may be exposed to the contaminants, now and in the future?
  • How, how often, and for how long could the exposure occur?
  • Which contaminants pose health risks?
  • Do those contaminants occur at potentially harmful levels?
  • How can the exposure risk be reduced or eliminated?
  • What contaminant levels can safely remain at the site?


These questions are posed in the approximate order of their consideration during the risk assessment process. 

The Risk Assessment Process.

Several conditions must occur simultaneously for risk from exposure to a contaminant to exist: 

  1. The contaminant must be toxic or carcinogenic to receptors,
  2. The contaminant must occur in the environment at a level that is toxic or carcinogenic to receptors (human and non-human populations most likely to be exposed),
  3. A pathway must exist through which exposure to the contaminant is reasonably possible, and
  4. The frequency and duration of the exposure must exceed certain thresholds.


Requiring these conditions to exist at the same time makes risk assessment an inherently conservative process. Many contaminants are not toxic or carcinogenic at any level, and contaminants that occur at potentially harmful levels may not pose a health risk if they occur below certain concentrations or if exposure to them is unlikely or brief.

As suggested by the above questions and conditions, risk assessments are site- and contaminant-specific and proceed through a sequence of steps: Data collection and evaluation, exposure assessment, toxicity assessment, and risk characterization.

Data collection and evaluation occur throughout the investigation of a site as its physical characteristics are defined and the types, sources, transport mechanisms, and distributions of contaminants in soil, groundwater, surface water, and air or vapor are characterized. These are the basic elements of a Conceptual Site Model, or CSM (see Wilcox Blog “IDEM Strengthens Its Emphasis on Conceptual Site Models for Environmental Projects”, November 29, 2011).

The exposure assessment is the final part of CSM development when potential exposure pathways, potential receptors, scenarios through which exposure could occur, and exposure routes are identified. Common exposure scenarios are residential, commercial/industrial, recreational, and soil excavation. Each scenario is characterized by assumptions about the pathways, routes, frequency, and duration of exposure that are captured in standard risk equations developed for each scenario by the US EPA. The example equation below is for calculating non-carcinogenic Health Protective (screening) Levels (HPLs) for direct contact with soil through ingestion in a residential exposure scenario.

Exposure “pathways” and “routes” are not synonymous terms, and they are often erroneously used interchangeably. Pathways are environmental media or mechanisms, such as groundwater, soil, vapor intrusion, and soil excavation that bring contaminants into contact with receptors. Exposure routes are potential entry points of contaminants into the body such as ingestion, inhalation, and dermal contact.

Other sometimes confusing terms are “complete” and “incomplete” with respect to assessing exposure pathways. In the traditional risk-assessment sense, any contact with a contaminant results in a completed exposure pathway. Whether that exposure could result in a health risk depends on whether the contaminant is capable of producing harmful effects at the concentration, frequency, and duration at which the exposure occurs. It’s common to have completed pathways that don’t result in health risks. This aspect of risk assessment is the toxicity assessment, which is discussed below.

A thorough exposure assessment considers all potential on- and off-site exposure pathways and routes, though some may be eliminated during the assessment as inapplicable or complete but of low risk based on other lines of evidence. Other descriptors can be used to identify pathways for which risks will be managed using institutional controls or for which no remediation is necessary even if exposure would occur.

Toxicity assessments are performed through epidemiological, clinical, and animal research to identify the types and severity of health effects associated with exposure to specific chemicals. Consultants use the results of toxicity assessments in the risk-characterization step described below but normally don’t perform them. Within a toxicity assessment, a dose-response (DR) evaluation explores how the severity of adverse health effects varies with the concentration of a contaminant and the duration and frequency of exposure to it, ultimately identifying an exposure level (dose) below which adverse health effects are unlikely. DR evaluations may also distinguish between adults and children, who are particularly sensitive receptors and potentially prone to adverse health effects at lower doses, frequencies, and/or durations than adults. The DR evaluation may also differentiate between long-term (chronic) effects from exposure to low levels of contaminants over long periods and short-term (acute) effects from brief exposures to high levels of contaminants.

Risk characterization brings together information from the exposure and toxicity assessments to produce quantitative estimates of the risk of adverse health effects in populations exposed to the contaminants. The potential risk for each contaminant associated with each completed pathway is calculated using standard equations (see attached example). The individual compound-specific risk estimates are then summed to yield a quantitative estimate of total, cumulative risk for each pathway. The cumulative risks for toxic and carcinogenic compounds are compared with levels of acceptable risk established by the US EPA or state guidelines.

For non-carcinogenic contaminants, toxic effects are expressed as a Hazard Quotient (HQ) for each contaminant. The HQ compares the expected exposure level for the contaminant to a reference exposure level (dose) that is not expected to cause an adverse health effect. The HQs for all contaminants associated with an exposure pathway are summed to yield the Hazard Index (HI) for that pathway. The US EPA and IDEM consider individual HQs and cumulative HIs of less than 1.0 to be associated with low risk of non-carcinogenic, toxic effects.

For carcinogenic contaminants, calculated total excess lifetime cancer risks within the range of 10-4 to 10-6 are considered acceptable by the US EPA and IDEM. This range means that one additional incidence of cancer over the background cancer rate per 10,000 to 1,000,000 exposed individuals is considered acceptable. The screening levels for carcinogenic compounds in the IDEM Remediation Closure Guide are based on an intermediate excess lifetime cancer risk of 10-5, i.e., risk levels that would theoretically result in one additional incidence of cancer over the background cancer rate per 100,000 exposed individuals. While IDEM is supposedly open to a 10-4 risk level, the RCG offers no clear guidance for justifying this higher risk level.

If the toxicity assessment and risk characterization show that site contaminants are either not harmful or not present at harmful levels, the risk assessment may be halted. Often, a risk assessment will eliminate most site contaminants from further consideration while some higher-risk contaminants are retained, possibly for remediation or some other form of risk management. For example, ethylbenzene and xylenes may be eliminated as sources of risk at a petroleum site, but benzene, a known human carcinogen, may remain as a contaminant of concern.

Risk Assessments Lead to Site-Specific Risk-Management Decisions. Important uses of risk assessments are to determine if remediation is necessary and, if so, to establish cleanup goals for soil, groundwater, and vapor intrusion. If the risk assessment determines that the potential risk is already less than the maximum acceptable level (e.g., HQ/HI < 1.0 or carcinogenic risk < 10-5), the site or portions of it may not require remediation. If the potential risk exceeds the acceptable levels, the risk assessment can be used to “back calculate” protective remediation goals by identifying the highest concentration of each contaminant, or perhaps the most toxic or carcinogenic contaminants, that can be left in place without posing an unacceptable level of risk to potentially exposed receptors.

Groundwater Remediation Goals. The EPA has established or proposed health/risk-based drinking water standards for dozens of chemicals under the Safe Drinking Water Act. The Maximum Contaminant Levels (MCLs) and non-zero MCL Goals (MCLGs) generally serve as cleanup (screening) levels for groundwater that is currently or may be used as a residential drinking water source. Many chemicals, however, have no MCLs and their remediation goals may be established using risk assessment. Where contaminated groundwater discharges to surface water, remediation goals may be based on ecological protection and use of the surface water as a drinking water supply.

Soil Remediation Goals. Cleanup goals for soil depend on whether the use of a property is or will be residential, commercial or industrial, or recreational. Predicting the future use of a contaminated site is difficult and introduces uncertainty into the risk-assessment process.

Where current or future residential land use is anticipated, cleanup goals must allow unrestricted access and safe, unlimited exposure to site conditions. Soil cleanup goals for commercial and industrial land uses are generally less stringent than residential goals because adult workers are assumed to have less frequent and shorter periods of exposure to soil contaminants and to be less sensitive to exposures than children living and playing on a property. As a result, regulatory closures of commercial and industrial sites usually allow higher levels of contaminants to remain in place. Recreational land uses assume occasional, short-term exposures, which should theoretically allow higher contaminant concentrations to remain at recreational sites; however, children are typically more sensitive receptors than adults, and the political realities of allowing contamination to remain at parks and playgrounds are common factors in determining how risks are managed at contaminated recreational sites.

Using Risk-Based Thinking for Our Sites

Assessing and managing exposure risk at our clients’ sites should go beyond merely comparing analytical data to screening levels. We should also consider the exposure assumptions used to derive the screening levels and other factors (site zoning, accessibility, presence of exposure barriers, etc.) as site-specific lines of evidence to characterize the actual likelihood of exposure and adverse effects from exposure to contaminants at our sites. While a full, quantitative risk assessment as described above may not be warranted for a particular site, the same types of considerations and assumptions come into play when assessing risk in a more qualitative manner.

If you’d like more information about assessing, managing, or remediating health risks related to site contaminants, please contact me at (317) 472-0999 or

Thursday, December 8, 2016

Why You Need a Data Management Workflow Process And How to Develop One

Posted by: Lacy Smith on Thursday, December 8, 2016 at 12:00:00 am


It is standard practice when conducting any environmental field work to rely on written standard operating procedures (SOPs). In fact, there are a number of organizations that provide detailed technical information about what those SOPs should look like for specific environmental field activities (e.g. USEPA, ASTM, ISO, various industry groups, and State Environmental Agencies). But just as important as having the technical procedures clear for your staff is having a clearly mapped out data management workflow process. Let’s dive in to exactly what role a workflow process plays in allowing for more efficient management of environmental data.

Organizations Run on Rules

All organizations need to follow a set of rules in order to function. These rules can be broken down into policies, processes, and procedures. As SweetProcess points out, “Too often these three items are used interchangeably, but there are key details in each that make them necessary on their own for a complete working system.” While policies provide the rules or guidelines, processes give a big picture perspective of how all of the tasks or procedures fit together. Processes define –

  • Activities – what are we doing?
  • Resources/Starting Points – what/who is needed to complete this task?
  • Work Products – what are we going to produce? How do we know when we’ve achieved our objective?

Specific procedures are used within the process to accomplish the task at hand. The process guides the individuals along the way. Ensuring that an organization has clearly defined policies, processes, and procedures is also one of the primary keys to organizational growth!

An Environmental Example

In the environmental industry, the legislation and policies implemented at both federal and state levels govern the processes and procedures that ensure the protection of human health and the environment. For most activities, such as groundwater sampling, well installation, and laboratory analysis, specific technical procedures have also been defined by these governing bodies. Additionally, state governments set up programs which define the process of meeting the requirements of the policies and laws. For example, the Process Overview of IDEM’s Leaking Underground Storage Tank Program is found on page 8 of this document. While the process provides direction on how to meet the requirements of IDEM’s LUST program, any one of these steps in the process has its own sub-processes and can be achieved in a number of different ways by different companies. Defining these individual workflow processes within a specific organization or project can provide considerable benefit, especially for consultants who do similar types of work for multiple clients.

Benefits of Workflow Process Mapping

Most environmental project managers develop workflow processes over time that make sense to them and help get their jobs done. With data coming in from multiple field and laboratory sources and a multitude of reporting deadlines, the typical project manager has little time to think about the best way to manage all of the data coming in. Over time, each project manager creates workflow processes and associated work products that fit their needs. Often, refinement to the process is made when errors are found or deadlines are missed. However, a more proactive and efficient approach is to spend a few hours thinking about the entire process of data collection – from scope and planning all the way through to the final production of the deliverable document. While doing this on an individual level will produce insights and efficiencies, developing a workflow process for common tasks from a company perspective will yield even more efficiencies. As the saying goes, how do you make a million widgets? You figure out the process to make one widget perfectly and then do that process a million times.

The major benefits of workflow process mapping include:

  • Clear identification of what needs to get done.
  • Knowing what resources we need to get the job done – both people and equipment.
  • Understanding the expected outcome.

Additional benefits of workflow process mapping include:

  • Providing a way to identify bottlenecks and more easily re-direct work.
  • Enabling all team members to understand the big picture and how their piece of the work contributes to the larger effort – a tool to keep everyone on the same page!
  • Identifying data and resource gaps ahead of time so we can plan for needed contingencies and/or redundancies.
  • Providing a tool to outline and communicate changes to the process throughout the organization.

The greatest benefit to workflow process mapping is that it allows an company or project team to take a task and develop a customized tool to bring clarity to the entire team on what is to be done and how to do it. At the same time, there is no fancy software or database needed. A white board and dry erase markers or large sticky notes can get you started. Just be sure to document your work by snapping a picture of the white board or notes before you leave the room so as not to lose your work!

How to Create Workflow Process Maps

Creating a workflow process map, while it will require some thought and time, is not a difficult process in and of itself. The simple three-step outline below will allow you and your team to build workflow processes for any task you perform. A good starting workflow process would be for routine groundwater sampling and reporting – a task most environmental professionals do on a regular basis.

Step 1: Assemble your team and pick your workflow to map

Ideally, when working with a team, a workflow process map should not be created by one person. In our example case of a groundwater sampling event, there are a number of people involved in accomplishing this task. It is important to include one or two people who know the details of all the tasks and sub-tasks that need to be accomplished. In addition, it is important to define what will (and what will not) be covered in the specific workflow process. Making the process as specific as possible will aid in its usefulness.

Step 2: Set aside a couple of hours to brainstorm

You will want to get on paper all the steps that are needed to get the job done, including people and resources utilized. A whiteboard is great for this work as it allows you to draw connections between steps and easily write and re-write items that need to be included. Timing of specific steps should also be identified as well as contingencies and quality assurance steps.

Step 3: Finalize and Communicate

After the initial brainstorming process, you will want to formalize the information you have mapped out. This can be done in a number of different graphics programs such as Microsoft Visio. In this step, it may be useful to give the workflow to those performing the job and ask them to verify the steps you’ve outlined as they do it. Incorporating feedback will help identify whether the process you’ve mapped reflects how the job should be done and where perhaps the job is not being done correctly. Finally, communicating the workflow process to all involved and describing how it should be used – both for training and day to day reference – is key to making this an effective tool.

Communicate and Use Workflow Process Documents

A workflow process map is not a whole lot of good if the entire team isn’t able to access and use it. Once you’ve finalized your process, be sure to communicate to all individuals involved in the process what their role is and how the process flows. Over time, processes may need to change. The workflow process map should be updated on an as needed basis. This document can function as both a guide for daily use as well as provide an accountability tool to ensure that individuals are performing their jobs as expected. The key to its usefulness will be in regular review to ensure it reflects accurately how the job is to be performed.

This workflow process mapping is a tool that Wilcox has and continues to use on a regular basis to streamline and ensure maximum efficiency in all our services. For more details regarding Wilcox’s data management and graphics services, please contact Lacy Smith (