Simply put, the proper characterization of an environmental problem is the first and most critical step in solving an environmental problem. This is true regardless of whether the ultimate remedy is an engineered solution or natural attenuation, or risk assessment, or the simple demonstration that no remedial actions are required. For the most part, today’s regulatory climate rewards those that know how to collect the right site-specific data, interpret the data, and present it in a manner that simplifies the issues and clearly demonstrates the best pathway to close the project.

As a result, often it is the wise environmental manager that understands the balance between the up-front investigation costs to characterize the nature and extent of contamination versus the often much larger downside costs of remediating the site because the regulator was not convinced that the problem posed no threat to human health or the environment.

Investigations and remediation are EME’s core services and our principals are active participants in their implementation. From principal to entry-level staff, we work closely with our clients to ensure that our investigation strategy generates the right data needed to answer their questions and to move the project to closure. Our in house expertise is capable of developing the most suitable sampling and analysis programs to achieve our clients’ objectives and meet any applicable regulatory requirements

EME stays current, as such we know the strengths and weakness of both innovative and conventional investigation approaches. More importantly, we scope our investigations from our clients’ perspective and align our activities with their exit strategy. This affords our clients the peace of mind of knowing that EME’s data collection activities have been well thought through in advance of going into the field. Our field personnel are aware of the overall strategy, and as such, our experienced staff can make the appropriate field decisions necessary to ensure that useful and representative data are collected without project delays.

But EME’s ability to support our clients’ needs does not end there because we understand how to evaluate the data. This may seem like an obvious skill of every environmental professional. But often, investigations are designed by the project manager in the office and implemented by junior field personnel without much direct hands-on oversight from the project manager. Not at EME — we believe that seeing is the first step to understanding. As such, our principals, senior level staff, and project managers take a hands-on approach to ensure that the field activities are appropriate and logical with regards to the project objectives and site conditions. To encourage the active involvement of our senior level staff during the data collection activities, our staff is allowed to use flexible billing rates. For example, if one of our senior staff members is performing technician level groundwater sampling activities, that activity will be billed at a lower rate appropriate of the task and not the experience level of the employee. Ultimately, this is a win for our clients and the project.

During the initial investigation of a large industrial laundry, free-phase PCE was recovered from the bedrock aquifer. Shortly afterwards it was discovered that the Facility had a release of PCE in the 1970's. This site is underlain by a well developed karst bedrock aquifer that provides drinking water to the community.

The discovery of free-product prompted a surprising recommendation — DO NOT INSTALL costly bedrock wells to delineate the downgradient extent of impact. Instead, an innovative approach was proposed that delineated the dissolved-phase plume using natural hydraulic features. Our approach started in the library where numerous publications on the area-specific groundwater flow characteristics were reviewed to gain a fundamental and, essentially, free, understanding of the hydrogeology. Then, a conceptual fate and transport model was developed based on the structural flow controls of the aquifer and our understanding of the unique chemical, physical, and biological properties of PCE.

Based on this model, it was theorized that the primary flow of contamination from the site would be advective flow within discrete conduits. The affects of diffusion and dissolution would be minimal due to the nature of the bedrock aquifer. This would result in the development of a long and narrow downgradient plume oriented along primary axes and that groundwater within these conduits would naturally discharge to the surface along a local hydraulic boundary.

After presenting our conceptual model, the overseeing agency approved it without comment. The subsequent water quality data validated our model. However, even though the agency agreed with the findings, they still requested that a network of confirmatory wells be installed. The location of the wells were selected based on the earlier data and the results further validated our original model. Through this process, we estimate that the number of bedrock wells needed to delineate the plume was reduced from 12 to 6 wells. At this site, each bedrock well can range between $20,000 and $70,000.

An RFI Work Plan was prepared for a spent solvent management facility permitted to store and treat hazardous waste. The plan called for 18 Solid Waste Mangement Units (SWMUs) to be investigated as a single area called a solid waste management area (SWMA). This concept was presented to and approved by the regulatory agency. It eliminated the more costly SWMU-by-SWMU investigation approach and has proven to have been the right way to assess this site due to its complexity.

This particular site is in the Alabama Valley and Ridge Physiographic Province, which is an area characterized by complex structural geology and hydrogeology. The complexity of the site setting coupled with the unique fate-and-transport characteristics of the numerous chlorinated solvent contaminants and VOCs present, required the use of both conventional and innovative investigation and data collection techniques.

The data collected has aided in our understanding of the site’s complexity and the nature and extent of Facility-associated contaminants. The data collection techniques employed included passive soil-gas, GeoProbe soil and groundwater sampling, hollow-stem auger drilling, air-rotary and rock coring drilling techniques, hydrologging aquifer testing, discrete fracture zone groundwater sampling, acoustic televiewer, and a suite of other downhole geophysical logging techniques. These various data collection techniques were used and were highly successful at characterizing this site.

Current ongoing activities include the final stages of the RFI and a CMS. In addition, the aquifers geochemistry is being evaluated to assess its ability to naturally attenuate the various chlorinated solvent compounds detected in the aquifer.

At this ongoing site, trichloroethene and its daughter products were found in groundwater in the vicinity of this closed 1960's era dump. However, none of these associated contaminants had been detected in shallow groundwater or in leachate samples collected from the landfill. Because of the known improper disposal practices that were employed by a company that is responsible for several other trichloroethene sites around the county, Tennessee Department of Environment and Conservation (TDEC) officials raised concerns that trichloroethene maybe present in the landfill as a result of illegal dumping, but had yet to be detected.

The characteristic of trichloroethene to act as a Dense Non Aqueous Phase Liquid (DNAPL), if present in sufficient quantities, prompted TDEC officials to request a groundwater investigation be conducted at greater depths than previous investigations. Based on the potential karst nature of the bedrock, TDEC further stipulated that the investigation focus on the primary groundwater migration pathways potentially present within the geology/karst features.

Due to the complex hydrogeologic setting and the unique fate and transport characteristics of TCE within this environment, focusing the sampling program to target preferential groundwater flow pathways with depth would be a difficult, if not, impossible task using conventional investigation techniques. As a result, an innovative geophysical technique, typically used for mineral exploration, was used in an effort to identify areas of deep weathering developed on fracture trends in the bedrock. Analysis of the geophysical results was compared to the results of geologic field mapping done in the area to identify the dominant bedrock fracture trends in the area. The results of the geophysical survey identified several fairly well defined trends which matched the bedrock fracture trends mapped in the area.

To date, an exploratory drilling program has been conducted that has confirmed that the results of the geophysical survey. Deeply weathered features (in excess of 300 feet below ground surface-bgs) have been identified in the bedrock. Drilling conducted offset from the subsurface trends identified by the geophysical survey encountered bedrock at much shallower depths (70 feet bgs). Screening level samples collected during the bedrock profile drilling program indicated the presence of trichloroethene in these deeply weathered zones.

By adapting this geophysical survey tool, which is typically used for mineral exploration, to characterize groundwater flow within the subsurface media, the scope of the drilling activities was significantly reduced and, what is more important, the limited data that was collected is sufficient to move the project onto the next stage of the investigation. If conventional bedrock profiling techniques were used to characterize the bedrock surface, project costs could have easily exceeded three to four times the costs of this phase of work.