PM Strauss & Associates
Technical Advisor to community groups
throughout the US
Technical Advisor to Center for Public
Environmental Oversight (CPEO) on the
Moffett Field and MEW Technical
Remedial Process Optimization
• In June, EPA ordered that each of the
MEW companies, the Navy and NASA to
develop remedial process optimization
(RPO) studies for each of the source
areas and the regional system.
• As I understand it, after EPA provides
comments on the RPOs, the FFS will
continue and the results of the RPO
studies will be melded into it.
Need for RPO
• The basic premise of RPO is a systematic
evaluation and enhancement of remediation
• Systems at MEW/Moffett were designed with
knowledge and conditions at the time
• New technology has developed
• Old systems haven’t worked as well as
• Extraction and monitoring wells were located in
places that may not be ideal
• Land use has changed.
Need for RPO
Examples from other sites
• A well rehabilitation program was initiated to
improve the well yields
• A removal technique focusing on the source
area may allow discontinuation of all site-related
active remediation in less than six months
(reducing remediation time by 9 years if pump
and treat continued).
• A Cost Effective Sampling process was
developed that addressed the issue of sampling
frequency. The above study examined where
monitoring wells should be placed.
• RPO means different things to different people.
• The RPO is a double edged sword: while it may
accelerate and enhance remediation,
responsible parties may see it as an opportunity
to focus on what they can do less of (e.g., less
extraction, less monitoring, abandonment of
some extraction wells, opportunity to change
remedial action objectives).
Remedial Process Optimization –
The community believes that RPO should
Reducing plume migration
Increasing the rate of mass removal
Improving health and safety (e.g., reducing risk).
Improving the long-term monitoring system
Cost and efficiency should be evaluated, but
should not be the primary decision criteria.
Optimization of Remediation
• Alternatives that replace current systems must speed up
remediation, remove or destroy contaminants that are
not being addressed by the current system, and/or
increase mass removal rates.
• Delineate an exit strategy
• Consider natural resource use
• Evaluate the effectiveness of existing institutional
controls as well as the need to establish new institutional
• Evaluate hot spot removal.
• Evaluate changes in systems to simplify them
Well Location, Removal and
• If wells are being removed or extraction rates
decreased, there should be a guarantee that
capture zones will be maintained.
• Evaluate the need for additional wells and/or
increasing extraction rates.
• Evaluate lateral dispersion/convection to
identify preferential pathways.
• Evaluate the need to refurbish or replace
extraction and monitoring wells.
• Evaluate effectiveness of long term monitoring, as
little attention is paid to this in the RI/FS process.
• Evaluate less costly/more accurate approaches to
• If there are changes to the remediation system, the
monitoring system should be adjusted accordingly so
that it will monitor changes in performance.
• Long-term monitoring should also be integrated into a
contingency plan (e.g., failure of slurry walls).
Health and Safety
• Ensure that the systems will be at a minimum
as protective to environment, and health and
safety, as systems already in place
• The RPO process should not be used to
change Remedial Action Objectives; although
it may provide basis for doing so, RAOs
should only be changed by ROD amendment,
with appropriate public participation.
• Assess changes in environmental conditions
and land-use, and strategies should be
developed that address these changes.
Examples of Recommendations
• Evaluate the frequency of monitoring and the
efficiency of the program
• Discharge to the Palo Alto Regional Water
Quality Control Plant (RWQCP) without
• Reduce extraction rate/close some wells
• In conjunction with the optimization activities, the
existing RAOs should be evaluated
• No modifications to the treatment system
components are necessary to optimize its
• Pulsed Extraction
• Treat subsurface prior to extraction and treatment of the
groundwater, such as surfactant flushing
• Treat VOCs in multiple matrices, e.g., dual-phase
• Permeable Reactive Barriers (including modifying
existing slurry walls)
• In-situ Bioremediation
• In-situ Chemical Oxidation
• MNA (monitored natural attenuation)