Public Comments on Draft EPA Five-Year Review Report on Cleanup at MEW & Moffett Field
(Aug 05, 2004) U.S. EPA Region 9 requested public comments on the
Draft Five-Year Review Report
evaluating cleanup activities and results at the Middlefield-Ellis-Whisman (MEW) Area
in Mountain View. (This report also covers Moffett Field, since contamination at both
sites is commingled.) All public comments received by EPA are listed below in alphabetical
order with links to the complete documents. Many thanks to EPA for providing them.
Where possible, we have blanked out email addresses to prevent spammers from harvesting them.
Comments generally praised EPA's work in preparing an excellent report, but did suggest
some changes to the report. Beneath the title for each comment document is a brief summary
list of its major and/or significant suggestions. These summaries attempt to be objective
but were not provided by parties who submitted the comments. For completeness and accuracy,
read the linked comment documents themselves.
Many comments agree on certain issues, but there are also significant disagreements.
To inform the affected community, help clarify or resolve disagreements, and provide a
forum for community input on the cleanup issues, there will be a public forum and debate
at the NMAC meeting on Wed August 18. The forum will include a briefing, panel, and
community participation. For details on the forum, see
MEW-Moffett Cleanup Issues Forum.
Center for Public Environmental Oversight by Lenny Siegel [76 KBytes]
- Take action quickly to better define MEW groundwater plume west of
Whisman Road since the community has little confidence in reported
- Take action quickly to better define vapor intrusion west of Whisman
Road since recent discovery of indoor air contamination there suggests
residents may have suffered exposures for 3 decades or more.
- Continue to base investigation, mitigation, and remediation on the
provisional TCE screening levels while they are under review.
The Draft Toxicity Assessment for TCE was praised by EPA’s Science
Advisory Board peer review committee, but EPA headquarters has
deferred finalizing it in apparent response to pressure from the
Defense Department, other polluters, and the White House.
Fairchild Semiconductor and Raytheon by Locus (Elie Haddad) [127 KBytes]
- Do not use EPA 2001 Draft TCE Health Risk Assessment ("Draft TCE
Risk Assessment") as a basis for assessing TCE toxicity. This is
scientifically inappropriate and contrary to EPA policy and law.
- Correct misconception that source control recovery wells are
designed to control geographical areas. These wells have been
installed to control sources, not necessarily the entire
property where the sources are located.
- Include a quantitative analysis of concentration trends. Report
provides only a qualitative evaluation of trends, with a general
statement about overall decreasing trends. Then it focuses on a
few wells with increases.
Mountain View City by Kevin Woodhouse [26 KBytes]
- Broaden follow-up actions for air to address buildings "in the
vicinity of" TCE groundwater contamination and not just "overlying"
it, in case TCE vapors have traveled via preferential pathways into
homes not over the plume.
- Require mitigation when indoor TCE levels are inside EPA's
health protective risk range at the high end. Draft report
only requires mitigation where TCE is detected above
protective risk range.
- Revive deep aquifer TCE extraction and sampling at the Silva Well
and investigate the source of this deep aquifer contamination.
- Consider further soil monitoring or mitigation because of possible
vapor intrusion from TCE remaining in soil. Soil cleanup standards
for TCE (0.5 mg/kg outside slurry walls and 1.0 mg/kg inside) were
set to achieve groundwater cleanup and did not consider air
contamination from TCE vapor intrusion.
- Note that groundwater in the area is a potential future source of
drinking water although not currently used for this.
- All sample analysis should use laboratories that can detect TCE
at the 10-6 residential risk level. Some laboratories
now used by EPA, Navy, and MEW Responsible Parties cannot.
- Develop one consistent, uniform and accurate plume map. Plume
maps produced by the Navy and MEW Responsible Parties use
different methodologies, causing confusion over plume boundaries.
- The plume map should show concentrations below 5 ppbA, to
show possible relation between groundwater concentrations and
vapor intrusion into the air.
NASA by Don Chuck [46 KBytes]
- Consider fully investigating all potential Navy sources of
contamination at former NAS Moffett Field, not just the WATS area,
since the Navy withdrew from agreement allocating responsibilities
for commingled regional plume area north of Hwy 101.
- Correct report to state that soil concentrations at Navy buildings 29
and 31 were above action levels, not below them.
- Expand writeup on Navy WATS Advanced Oxidation Process (AOP) treatment
system that destroys VOCs to explain that it required additional
liquid-phase GAC units to remove acetone produced by it.
- Qualify statement that petroleum hydrocarbons in the plume are helping
degrade PCE and TCE in the Navy WATS area by explaining that no evaluation
shows degradation has progressed past vinyl chloride (which is more
toxic than TCE) to ethene.
U.S. Navy by Rick Weissenborn and Mary Parker [50 KBytes]
- Report states that additional work is needed in the Navy’s source areas
and that Navy remedial system is not effective, but that MEW companies’
remedies are effective. However, the individual source control
descriptions/evaluations for MEW state that the contaminants have not
always been captured, etc.
- Vapor intrusion pathway and toxicity of TCE are undergoing peer review.
While potentially protecting human health and the environment, they
cannot be imposed on MEW, Navy, or NASA.
NEC by GeoSyntec (Susan Skoe) [18 KBytes]
- The 0.005 mg/L contour line, in Figures 2-5, 2-6, 5-1, 5-3, 5-4,
and 5-15 is drawn by interpolating between widely scattered points in
some parts. It should be identified by a dashed (not solid) line to
indicate it uses extrapolated data, rather than actual data
- The concentration contour figures should mention that contour lines
are estimated or interpolated or approximated.
Santa Clara Valley Water District by Thomas Mohr [49 KBytes]
- Map solvent contamination with 1 ppb, 10 ppb, 100 ppb, etc. contours.
Current 5 ppb contours show where concentrations exceed cleanup
standard, but 1 ppb contour would help indicate contaminant migration
pathways and show the total area where TCE has been found. Detailed
1 ppb contours may reveal patterns and flow paths that cannot be
discerned from 5 ppb contours.
- Display all plumes on the map, including nearby concentrations,
whether or not interconnection to the main plume has been established.
This may aid interpretation of patterns of contaminant distribution.
For example, show contamination at Moffet Field Orion Park Housing, at
327/333 Moffett Blvd (northeast of its intersection with Central Av), etc.
- Resume pumping remaining moderate levels of TCE contamination in lower
aquifer (C zone) at the Silva Well. This is in direct connection to
drinking water wells used by Mountain View. Although now used
infrequently and providing less than 10% of the City’s water, these
wells might be needed in case of contract problems, prolonged drought,
Silicon Valley Toxics Coalition prepared by Peter Strauss [47 KBytes]
- Re-evaluate MEW soil cleanup standards set in late 1980s in light of
vapor intrusion pathway and new models/information about soil to
groundwater pathway. These standards did not consider vapor intrusion
pathway and were not based on hard scientific information.
- Develop regional conceptual model for vapor diffusion and intrusion.
- Continue experimentation with innovative technologies to remediate
soil and groundwater to lower levels.
- Develop plans to quicken cleanup of shallow contamination, because
of its relation to vapor intrusion problem.
- Ensure that data and methodologies used to draw plume contours by
NASA, the Navy, and MEW companies are uniform and consistent.
Contours now drawn by these three parties differ, depending on the
point they wish to make.
- Contours should show 1 ppb, as in the past at MEW and other sites in EPA
Region 9. This is important information for the community because the
vapor pathway is not necessarily correlated with groundwater contours.
- Enhance the community’s ability to monitor progress by including
cleanup performance goals with milestones tied to dates.
- Address discharges of effluent from TCE treatment facilities into
- Evaluate possible increase in diffusion of contaminants from
groundwater to air because of higher groundwater levels inside
- Use more protective end of EPA risk range (10-6,
corresponding to 1 in 1 million additional cancer deaths) in
- Clarify why pumping ceased in 2001 at the 465 ft. deep Silva Well
(near Sherland and Tyrella) which has contamination from unknown sources.
Cleanup here is important because it could contaminate Mountain View’s
drinking water well field.
SMI by PES Environmental (Susan Gahry) [133 KBytes]
- Replace Figure 5-7, that inadvertantly mixes data from
different dates and is mislabeled, with attached figure showing
correct contours and estimated capture zone for November 2003.
Vishay and SUMCO by Geomatrix (Frank Szerdy) [95 KBytes]
- It is inappropriate to use the EPA 2001 Draft TCE Health Risk Assessment.
Vishay General Semiconductor and SUMCO concur with Locus' detailed
comments on this.
- TCE contamination said to be increasing in two monitoring wells is not increasing
attached graphs [13 KBytes]).