Making Mistakes
04/05/2006
by -- John Nicholson
Overcoming errors may be the key to a successful remediation project
Imagine you are the owner of a property that has a pump-and-treat system on site to control groundwater contamination. The system has been in operation for more than 10 years. You are paying over $60,000 annually on operation and maintenance costs (O&M) for this system. And there appears to be no end in site.
The above scenario is not a figment of the imagination; it was the reality for an industrial property owner in the Greater Toronto Area (GTA) whose property had groundwater contaminated with industrial solvents. A pump-and-treat system was installed in the early 1990s for the remediation of contaminant plume. The original objective of the project was to remove the contaminants until clean-up standards were met and to keep the contaminants from migrating off site.
Golder Associates, a Canadian-based international consulting firm, took over the project in 2000. They found the contaminant mass removal rates had steadily declined over the 10 years the system had been in operation, despite increasing groundwater recovery volumes.
Pressure to perform
The current method of dealing with contaminated properties by consulting engineers, contractors and regulators is to conduct Phase I, II and III Environmental Site Assessments to determine the extent of the contamination, explore alternatives for remediation, and implement a remedial approach. The problem with this approach is that once a course of action is chosen, the perception is that it is very difficult to change track. All parties become committed to the selected solution despite possible indications to the contrary once that solution is in place or once it has operated beyond the time frame of peak effectiveness.
With the current mentality among the profession of "study, design, build, operate," many systems are operated beyond their effective or cost-efficient life. Improved knowledge and experience has resulted in a greater understanding of the technological limitations of some remedial approaches. There is nothing wrong in re-evaluating the effectiveness and cost efficiency of remediation and improving it.
A recent United States Environmental Protection Agency evaluation of 20 remediation programs recommended that 13 (65 per cent) use more aggressive source removals for a proposed savings of net US$4.8 million.
It is clear from the U.S. EPA study that the re-evaluation of treatment success is required on any site where a long-term remediation program is in place or when remediation projects with high annual O&M costs occur.
Remedial process optimization
What is gaining popularity in the consulting profession is the use of remedial process optimization (RPO). Simply put, RPO is a systematic evaluation and enhancement of the site remediation process to ensure the environment is being protected over the long term at minimum risk and cost.
A good indicator of whether RPO should be implemented is the comparison of cumulative cost of the remediation program to the annual contaminant mass removal. If cost is heading in a different direction than the mass removal rate, it's time to reconsider the current approach to remediating the site.
The three main steps to RPO are as follows:
* Optimize the exit strategy -- What are the remediation objectives? Are they still practical?
* Optimize the remediation system -- Do components need to be removed from or replaced on the existing system? Does additional source reduction or hot-spot remediation need to occur?
* Optimize the monitoring plan -- Is the current frequency necessary? Can less costly analysis be substituted? Are all monitoring locations necessary?
As for the industrial property in the GTA that had a pump-and-treat system operating for 10 years, the RPO conducted by Golder Associates concluded that one of the original objectives of the system, hydraulic capture, was not being achieved. To prevent off-site migration of contaminants, two additional recovery wells were installed at the down-gradient edge of the contaminant plume.
Additional optimization by Golder included the temporary shutdown of three recovery wells and the injection of nanoscale, zero-valent iron particles to expedite the removal of the industrial solvents. An approximate forty-fold increase in the rate of contaminant mass removal was achieved as compared with the ongoing pump-and-treat program.
The key to the acceptance of RPO is the education of property owners that no groundwater remediation system is 100 per cent guaranteed and that changes will likely be needed depending on the results over the duration of the project. If the client understands that additional capital costs to tweak a system will result in overall project savings due to reduced O&M, then the RPO will be met with approval.
It is incumbent on consultants and contractors to periodically re-examine the success of groundwater treatment systems, or lack thereof. The use of RPO is a necessary tool in the phased approach to remediating sites.
John Nicholson is president of Environmental Business Consultants in Toronto. For further information, e-mail him at john.nicholson@ebccanada.com. He wishes to thank Steven Desrocher of Golder Associates for his contribution to the article. Mr. Desrocher can be reached at steven.desrocher@golder.com. |
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