HomeMy WebLinkAboutStaff Report 6929 (2)City of Palo Alto (ID # 6929)
City Council Staff Report
City of Palo Alto Page 1
Report Type: Action Items Meeting Date: 6/28/2016
Summary Title: 1451-1601 California Ave - Stanford/Mayfield Housing
Subdivision Amendment
Title: CONTINUED PUBLIC HEARING: 1601 California Avenue [15PLN-00500]:
Request by The Board of Trustees of the Leland Stanford Junior University to
Amend the Final Map for Tract Number 10281 Recorded January 2015 for the
1451-1601 California Avenue Development, Which Includes a Total of 180
Dwelling Units. Environmental Assessment: City of Palo Alto/Stanford
Development Agreement and Lease Project Environmental Impact Report
(State Clearinghouse No. 2003082103) Zoning District: Research Park and
Alternative Standards Overlay Two (RP(AS2)) District (Continued From June
27, 2016)
From: City Manager
Lead Department: Planning and Community Environment
Recommendation:
Staff recommends that Council adopt the Record of Land Use Action regarding the Amendment
to the Final Map for Tract No. 10281 (Attachment A).
Executive Summary:
On June 23, 2014, the City Council approved a Tentative Map to subdivide three existing parcels
(16.96 acres) into 83 parcels to accommodate the proposed development of 180 dwelling units
located at 1451-1601 California Avenue, as envisioned in the 2005 Mayfield Development
Agreement. Subsequently, the Final Map was recorded in January 2015 (Tract No. 10281).
During demolition of the site, characterization sampling (soil, soil gas and groundwater)
conducted pursuant to the Mayfield Development Agreement Mitigation Monitoring and
Reporting Plan (MMRP) revealed an area of isolated elevated trichloroethylene (TCE)
concentrations in the form of soil gas under the former footprint of 1601 California Avenue
building, where a former plating solution sump is believed to have been a source contributing
to this release. This area was not accessible for TCE testing until after the building was
demolished.
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City of Palo Alto Page 2
The isolated TCE in soil gas remains between 14’-6” and 25’-0” below ground surface and has
not migrated 50 feet beyond this localized area. Also within this isolated area, TCE was found in
one perched groundwater sample at a concentration that would not contribute to vapor
intrusion; concentrations in groundwater have not migrated from the property. As required by
the MMRP, the applicant reported the test results to California Department of Toxic Substances
Control (DTSC). Among other measures, the applicant proposed to DTSC that seven homes
originally planned to be located on or near the elevated TCE readings be moved at least 50 feet
away from the isolated area thereby eliminating any potential risk of vapor intrusion to future
occupants. The isolated area would be used for open space and streets. DTSC agrees that there
will not be a risk to future site users with the proposed redevelopment design (Attachment B).
In order to relocate the seven affected houses, applicant proposes to redistribute 29 residences
at the southern end of the site and create a jog in the new Amherst Street to accommodate the
all 180 homes. The total square footage of lots has been reduced, which also lowers the size of
the proposed homes on these parcels; however, there is now a proposed increase in common
open space.
The applicant requests an amendment to the Final Map (Tract No. 10281) to accommodate this
redesign. This amendment affects only the southern portion of the (formerly 1601 California
Avenue) project site; it does not affect the former 1451 and 1501 California Avenue sites.
Background:
In 2005, the City of Palo Alto and Stanford University entered into the Mayfield Development
Agreement (MDA). Under the MDA terms, Stanford University was to lease to the City of Palo
Alto the six acre Mayfield site, located at the corner of Page Mill Road and El Camino Real, for
$1 per year for 51 years. Stanford was to construct soccer fields on the Mayfield site at its
expense and turn the fields over to the City upon completion, which was done in 2006. In turn,
the MDA provided Stanford with vested rights to build 250 housing units on two sites in the
Stanford Research Park, where R&D/office buildings exist today. Given the City’s historic
jobs/housing imbalance, the MDA recognized that the additional housing would be a mutual
benefit to Stanford and the City. The MDA also granted Stanford the right to relocate 300,000
square feet (sf) of R&D/office floor area elsewhere within the Stanford Research Park. (This
amount of floor area is less than the amount of non-residential floor area to be demolished at
the two designated housing sites.)
The California Avenue Site (1451-1601 California Avenue) would accommodate 180 dwelling
units. The site received approval for the Tentative Map on June 23, 2014 and the Final Map was
recorded in January 2015.
An Environmental Impact Report (EIR) certified in 2005 covers the Development Agreement
and subsequent projects that implement the agreement. When the EIR was prepared and the
Development Agreement was entered into, the existence of contaminants at the project site
City of Palo Alto Page 3
was known, and TCE was identified as a hazardous chemical that was typically used at the
Stanford Research Park. In accordance with the MMRP, a full investigation could not be
completed until the 1601 California Avenue buildings were demolished and testing could be
conducted under the building footprints.
Stanford was required to prepare a ‘work plan’ for corrective action and controls, and a risk
assessment to identify acceptable clean up goals for the intended use of the California Avenue
Site, and submitted this work plan to the DTSC for review and approval (Attachment D). As a
result, the DTSC issued a ‘no further action’ status for the site (Attachment B). The specific area
referred to is the open space area from which residences were moved to create the revised
plan. The measures that will be reviewed and approved by DTSC are long-term management
measures restricting or prohibiting activities such as building any structures in this area which
would be enclosed (such as a community restroom, for example), drilling water wells, or
disrupting vapor barriers in utility trenches in this area.
Discussion:
To implement the revisions necessary for the project, a limited revision to the recorded Final
Map is required. Section 21.16.280 of the Palo Alto Municipal Code (PAMC) authorizes map
amendments. After a final map or parcel map is filed in the Office of the County Recorder, the
recorded map may be modified by a certificate of correction or an amending map if:
i. there are changes in circumstances which make any or all of the conditions of such a
map no longer appropriate or necessary,
ii. that the modifications do not impose any additional burden on the present fee owner of
the property,
iii. the modifications do not alter any right, title, or interest in the real property reflected
on the recorded map, and
iv. the map as modified conforms to the provisions of the Subdivision Map Act and Chapter
21.16 of this title.
The decision to approve or deny a modification shall be made by the City Council for final maps.
The hearing shall be confined to consideration of and action on the proposed modification.
The applicant’s request meets the four requirements of PAMC Section 21.16.280. First, there
are changes in circumstances (elevated TCE readings under seven home sites) that make certain
final map conditions (the locations of those homes) no longer appropriate or necessary.
Second, the modifications were proposed by Stanford and thus do not impose any additional
burden on the fee owner of the property. Third, the modifications do not alter any right, title,
or interest in the real property reflected on the recorded map as Stanford has not sold or
leased any of the affected lots. Fourth, the map as modified conforms to the provisions of the
Subdivision Map Act and PAMC Chapter 21.16.
Figure 1:
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Previously Approved Layout
Figure 2:
Proposed Revised Layout
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Summary of Key Issues:
While the City does not have regulatory authority over the TCE, the previously approved
Mitigation Monitoring and Reporting Plan (MMRP) for the project (Attachment F) requires the
City to monitor Stanford’s preparation of a Work Plan and Corrective Action Plan as well as the
DTSC’s approval of such plan. A Supplement Investigation and Risk Assessment (SIRA) report
was prepared by Haley Aldrich to comply with the mitigation (Attachment D). The locations and
depths of TCE soil vapor which could cause potential significant health risk via indoor air vapor
intrusion are also given in the narrative Section of 6.2.1 (Future Residents) of the SIRA. It was
from these readings at these depths at these locations that Stanford decided to move the
homes rather than install mitigations at these houses left in place. This decision required the
amendment to the Final Map.
Along with “future residents”, the SIRA evaluated impacts to “future commercial/industrial
workers” and “future users of recreation areas”. Figure 17 of the SIRA shows through the
location of the former building and future development (house footprints, streets and
recreation areas), the location of the site boring samples, the sample readings and depths.
Other figures show the types of soils, the location of the soil types in relation to the boring
samples.
Concentrations of VOCs are lower near the surface, and exposure to VOCs in soil vapor via
City of Palo Alto Page 6
inhalation of outdoor air is not expected to occur or pose an unacceptable health risk under the
conditions evaluated. This is based on the results of shallow soil vapor samples collected within
the recreational area. In the unlikely event that low concentrations of VOCs reach outdoor air,
they would be destroyed by sunlight and or naturally diluted and dispersed by wind.
The proposed location of the recreational area is not expected to pose a risk to the use of the
area. The Site Management Plan will have a restriction on building any future enclosed
structure in this localized area without adequate mitigation against vapor intrusion approved by
DTSC.
DTSC’s remaining role is to ensure that any approved mitigation measures in place be
protective and maintained. Stanford is currently discussing with DTSC the option of a Site
Management Plan in lieu of its standard Land Use Covenant to establish post-development
mitigation management measures (if warranted). Either option would involve managing any
soil activities greater than 10 feet below grade, requirements for human health protective
measures within future building designs, notification requirements to DTSC, etc. Any of DTSC
final requirements would be binding on Stanford and the community’s association.
Policy Implications:
The proposed revisions are consistent with the adopted Development Agreement.
Environmental Review:
The project implements the mitigations contained within the Mitigation Monitoring Reporting
Program (MMRP) established by the Final EIR for the Mayfield Development Agreement (2005).
The preparation of the work plan and subsequent review and conclusion by DTSC requires no
further environmental evaluation for the project.
The proposed final map amendment would not result in a substantial increase in the severity of
the environmental impacts identified in the Mayfield Development Agreement EIR. During
construction, impacts would be the same as under the approved final map. All Mayfield
Development Agreement EIR mitigation measures would continue to apply. No additional
protected trees would be removed or relocated.
Once the project is complete, impacts would be the same, or slightly less than, the less-than-
significant impacts identified with the approved final map. The reason for this is that although
the amended map still provides for a total of 180 dwelling units at the project (as required
under the Mayfield Development Agreement), as noted previously, some units will be reduced
in square footage and bedroom count, as the house redistribution will be accomplished in part
by switching some of the larger house plans to some of the smaller plans, and, in some cases,
combining these smaller plans into duplexes. As a result, the project’s total occupancy and,
therefore, its total vehicle trips, will likely be reduced compared to buildout under the January
2015 final map.
Attachments:
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Attachment A: Record of Land Use Action (DOCX)
Attachment B: DTSC Supplemental Investigation and Risk Assessment Report
Concurrence (PDF)
Attachment C: Correspondence (PDF)
Attachment D: Supplemental Investigation Risk Assessment (DOCX)
Attachment E: Applicant Letter (PDF)
Attachment F: Upper California MMRP (PDF)
Attachment G: Project Plans (DOCX)
1451-1601 California Avenue Page 1 of 3
Attachment A
APPROVAL NO.______
RECORD OF THE COUNCIL OF THE CITY OF PALO ALTO LAND USE ACTION
FOR 1451-1601 CALIFORNIA AVENUE: REVISED FINAL MAP APPLICATION
[FILE NO. 15PLN-00500]
On June 27, 2016, the City Council approved the Revised Final Map
application to subdivide 16.97 acres into 68 lots for single-family use, two (2)
condominium lots for 112 multi-family units, and 15 private street/common area lots for
a total of 85 parcels, making the following findings, determination and declaration:
SECTION 1. BACKGROUND. The City Council of the City of Palo Alto (“City
Council”) finds, determines, and declares as follows:
A. On April 4, 2016, the Department of Toxic Substances Control of the
State of California determined that based on the Revised Supplemental Investigation and
Risk Assessment Report (SIRA) dated March 18, 2016 for the 1601 S. California site that
sufficient site characterization has been performed to define the nature and extent of
contamination present at the site and agrees that there would be no significant risk to
future site residents, based on the future redevelopment plans presented in the SIRA
which illustrates the location of future residences outside of the localized on-site VOC soil
vapor plume.
B. On December 16, 2015, Chris Wuthmann of the Board of Trustees of
the Leland Stanford Jr. University applied for a Final Map Revision for Tract Map 10281 for
portions of the former 1451-1601 California Avenue site. Characterization sampling (soil,
soil gas and groundwater) conducted pursuant to the Mayfield Development Agreement
Mitigation Monitoring and Reporting Plan (MMRP) revealed an area of isolated elevated
TCE concentrations in the form of soil gas under the former footprint of 1601 California
Avenue building, where a sump is believed to have been a source contributing to this
release. This area was not accessible for TCE testing until after the building was
demolished. The isolated TCE in soil gas remains at depth and has not migrated 50 feet
beyond this localized area; Also within this isolated area, TCE was found in one perched
groundwater sample at a concentration that would not contribute to vapor intrusion;
concentrations in groundwater have not migrated from the property. As required by the
MMRP, Stanford reported the test results to DTSC. Among other measures, Stanford
proposed to DTSC that seven homes originally planned to be located on or near the
elevated TCE readings be moved at least 50 feet away from the isolated area thereby
eliminating any potential risk of vapor intrusion to future occupants. The isolated area
would be used for open space and streets. This design redistributes 29 residences at the
former 1601 California Avenue so that the required 180 homes are still provided; creates
a jog in the new Amherst Street to accommodate the redistributed homes; reduces the
1451-1601 California Avenue Page 2 of 3
total square footage of home sites and homes in the affected area; and increases common
area open space.
C. On June 23, 2014, the City Council upheld the Director’s approval of
the Architectural Review application (13PLN-00433) and approved the Tentative Map
application (11PLN-00203), to construct 68 single family homes and 112 multi-family homes
and subdivide three existing parcels totaling 16.97 acres into 68 lots for single family use, two
(2) condominium lots for 112 multi-family units, and 13 private street/common area lots for
a total of 83 parcels.
SECTION 2. ENVIRONMENTAL REVIEW. In conformance with the California
Environmental Quality Act (CEQA), an Environmental Impact Report was certified by the
City Council for the Mayfield Development Agreement in 2005. The City of Palo
Alto/Stanford Development Agreement and Lease Project Environmental Impact Report
(EIR) (State Clearinghouse No. 2003082103) concluded that the proposed project(s) would
not have a significant effect on the environment with mitigation as proposed except there
would be significant and unavoidable Noise impacts, due to the use of heavy equipment
during construction. The certified, Final EIR is available for review on the City’s web site at:
http://www.cityofpaloalto.org/gov/topics/projects/landuse/mayfield.asp. In March 2014,
Staff prepared an Environmental Confirmation Memo and determined there are no
substantive changes to the previously approved project or circumstances under which the
project is being undertaken and no new information, therefore the EIR provides the
necessary environmental clearance for this subject project. All mitigation measures as
stated in the approved Mitigation Monitoring and Reporting Program (MMRP) have been
incorporated into the conditions of approval for the associated Architectural Review project
(13PLN-00433).
SECTION 3. FINAL MAP REVISION FINDINGS
In addition to the amendments authorized by Government Code Section 66469, after a
final map or parcel map is filed in the office of the county recorder, the recorded map may
be modified by a certificate of correction or an amending map if:
1. There are changes in circumstances which make any or all of the
conditions of such a map no longer appropriate or necessary. There are changes in
circumstances (elevated TCE readings under seven home sites) that make certain final
map conditions (the locations of those homes) no longer appropriate or necessary.
2. That the modifications do not impose any additional burden on the
present fee owner of the property. The modifications do not impose any additional
burden on Stanford, which is the fee owner of the property.
3. The modifications do not alter any right, title, or interest in the real
property reflected on the recorded map. The modifications do not alter any right, title, or
1451-1601 California Avenue Page 3 of 3
interest in the real property reflected on the recorded map.
4. The map as modified conforms to the provisions of the Subdivision Map
Act and Chapter 21.16 of the Palo Alto Municipal Code. The map as modified conforms to
the provision of the Subdivision Map Act and the PAMC.
PASSED:
AYES:
NOES:
ABSENT:
ABSTENTIONS:
ATTEST: APPROVED:
City Clerk Director of Planning and
Community Environment
APPROVED AS TO FORM:
Senior Assistant City Attorney
Department of Toxic Substances Control
Matthew Rodriquez
Secretary for
Environmental Protection
April 4, 2016
Ms. Annette Walton
Stanford Real Estate Office
3160 Porter Drive, Suite 200
Palo Alto, California 94304
Dear Ms. Walton:
Barbara A Lee, Director
700 Heinz Avenue
Berkeley, California 94710-2721
Edmund G. Brown Jr.
Governor
The Department of Toxic Substances Control (DTSC) has reviewed the Revised
Supplemental Investigation and Risk Assessment Report (SIRA) dated March 18, 2016
for the 1601 S. California site (Site) in Palo Alto, California. The SIRA documents the
supplemental investigation activities performed to further evaluate the presence of
volatile organic compounds (VOCs) at the Site, as previously discovered during
historical sampling, The SIRA also presents evaluation using the comprehensive data
collected from the Site to determine if chemicals present would pose a significant risk to
future Site receptors, in particular residents of the planned faculty housing development.
DTSC concurs with the conclusions presented in the SIRA. DTSC agrees that sufficient
Site characterization has been performed to define the nature and extent of
contamination present at the Site, and agrees that there would be no significant risk to
future Site residents, based on the future redevelopment plans presented in the SIRA
which illustrates the location of future residences outside of the localized on-Site VOC
soil vapor plume.
DTSC hereby approves the SIRA. As detailed in the SIRA, elevated VOCs in soil vapor
were detected at the Site in one area (specifically in the vicinity of a former plating
solution sump and operational areas of the former manufacturing facilities) that could
potentially pose a significant risk to human health in a residential scenario. DTSC must
review and approve the measures by which this specific area will be addressed to
ensure that future Site users will not be exposed to such health risks prior to certifying
that all necessary actions have been taken at the Site.
@ Oil
Attachment B
Ms. Annette Walton
April 4, 2016
Page 2
If you have any questions, please contact Jovanne Villamater at
Jovanne.Villamater@dtsc.ca.gov, or via telephone at (510) 540-3876.
Sincerely,
Mark E. Piros, P.E., Unit Chief
Brownfields and Environmental Restoration Program -Berkeley Office
cc: Mr. Christopher Wuthmann (email to: cwuthman@stanford.edu)
Mr. James Keene (email to: James.Keene@cityofpaloalto.org)
Ms. Cara Silver (email to: Cara.Silver@cityofpaloalto.org)
Ms. Molly Stump (email to: molly.stump@cityofpaloalto.org)
Ms. Hillary Gitelman (email to: Hillarv.Gitelman@cityofpaloalto.org)
Ms. Jodie Gerhardt (email to: jodie.gerhardt@cityofpaloalto.org)
Ms. Susan Gallardo (email to: SGallardo@haleyaldrich.com)
Attachment C
S
Matthew Rodriquez
Secretary for
Environmental Protection
March 18,2016
Mr. Richard Stolee
President, CTRA Board
rstolee@qmail.com
Mr. Lenny Siegel
Executive Director, Center for Public Environmental Oversight
lsiegel@cpeo.orq
Dear Mr. Stolee and Mr. Siegel:
The Department of Toxic Substances Control (DTSC) thanks you and the other
attendees for participating in the meeting held on January 6,2016 regarding the 1601 S.
California site (Site) in Palo Alto, California. We appreciate everyone taking time out of
their schedules to attend.
Enclosed are the responses to the questions and comments posed to DTSC regarding
the Site. The College Terrace Residents'Association (CTRA) submitted to DTSC a
letter dated January 26,2016 (CTRA Letter), which requested that DTSC answer Site-
specific questions, specifically regarding the presence of trichloroethylene in various
environmental media at the Site. Along with the CTRA Letter, the submittal email also
included comments from Mr. Lenny Siegel, the Executive Director of the Center for
Public Environmental Oversight (CPEO), dated January 25,2016 (CPEO Comments).
ln collaboration with Haley and Aldrich, !nc. and Stanford University Office of Real
Estate, DTSC presents the enclosed responses to both the CTRA Letter and CPEO
Comments, with the hope to provide answers as well as to provide additional insight.
Edmund G. Brown Jr.
Governor
9-t:kt
:
Department of Toxic Substances Control
Barbara A. Lee, Director
700 Heinz Avenue
Berkeley, California 947 10-2721
@ Printed cn Rccycled Faoer
Mr. Richard Stolee and Mr. Lenny Siegel
March 18,2016
Page 2
!f you have any questions, please contact me via email at
Jovanne.Villamater@dtsc.ca.sov, or via telephone at (51 0) 540-3876.
Sincerely,
Jovanne Villamater
Project Manager
Brownfields and Environmental Restoration Program - Berkeley Office
Enclosure
cc: Via electronic email to:
Mr. Christopher Wuthmann
cwuthman@stanford.ed u
M. Jean McCown
imccown@stanford.edu
Ms. Hillary Gitelman
H i I larv. G itel man@citvofpaloalto.orq
Ms. Jodie Gerhardt
iod ie. qerha rdt@citvofpaloa lto. o rq
Mr. Fred Balin
fbalin@qmail.com
Mr. Roland Vogl
RVool@law.stanford.ed u
Ms. Molly Stump
mol lv. stu mp@citvofpa loalto.orq
Ms. Cara Silver
Cara. S i lver@citvofpaloalto.orq
M. Margit Aramburu
Maro ith i nd @comcast. net
Mr. Brent Barker
brentqbarker@omail.com
Mr. Richard Stolee and Mr. Lenny Siegel
March 18,2016
Page 3
Ms. Lucy Wicks
lwicks@stanford.edu
Ms. Annette Walton
nettie@stanford.edu
Mr. James Keene
James. Keene@citvofpa loalto.orq
Ms. Susan Gallardo
SGa I lardo@ ha levald rich. com
Ms. Kimi Klein
Kimi. Klein@dtsc.ca.sov
Mr. John Karachewski
John. Karachewski@dtsc.ca.qov
Ms. Veronica Lopez-Villasenor
Veron ica. Lopez-Vi I lasenor@dtsc.ca.qov
Ms. Sue Dremann
Staff Writer, Palo Alto Weekly
sd reman n@ paweeklv. co m
RESPONSE TO CENTER FOR PUBLIC ENVIRONMENTAL OVERSIGHT
March 18, 2016
SUBJECT: Response to Center for Public Environmental Oversight (CPEO) Comments
This document provides responses to questions raised by the Center for Public Environmental Oversight
(CPEO) in its January 25, 2016, letter to the College Terrace Residents’ Association (CTRA) regarding the
presence of trichloroethene (TCE) in subsurface soils at the University Terrace development located at
1451, 1501, and 1601 S. California Avenue in Palo Alto, California. The CPEO letter was transmitted to
the Department of Toxic Substances Control (DTSC) by CTRA on January 26, 2015. The responses and
information provided herein were prepared by the DTSC; Stanford University, Office of Real Estate
(Stanford), the property owner and developer; and its technical consultant, Haley & Aldrich, Inc. As
subsurface chemical impacts primarily were detected at the 1601 S. California Avenue parcel and it is
the focus of the current Preliminary Endangerment Assessment, this parcel is referred to by its address
or as the “Site”. References to the other parcels that comprise the University Terrace development are
referred to by their address.
Our specific responses to the five questions (and sub‐questions) provided by CPEO are below. CPEO’s
“top‐level” questions are underlined.
1. THE DECEMBER 2015 RISK ASSESSMENT UNDERSTATES THE RISK FROM TCE VAPOR INTRUSION.
The human health risk assessment (HHRA) included in the Supplemental Investigation and Risk
Assessment (SIRA) Report1 was completed in accordance with guidelines provided by the U.S.
Environmental Protection Agency (USEPA) and California Environmental Protection Agency (Cal‐EPA).
Following this guidance, the risk assessment was performed with both the cancer and non‐cancer target
indoor air concentrations.
CPEO states that the screening level for the concentration of TCE in soil vapor that was utilized in the
Site evaluation is problematic because the default DTSC screening level is higher than that currently
recommended by the USEPA. The default screening levels were used to provide an initial understanding
of the data. The results for every soil vapor sample collected at the 1501 and 1601 S. California Avenue
parcels were individually evaluated in the site‐specific assessment, regardless of whether the result
exceeds the default screening level. If a default screening level is exceeded, it does not indicate that a
health risk exists, but rather that additional evaluation is warranted, such as additional sampling or risk
characterization. With respect to the detections of TCE at the 1501 and 1601 S. California Avenue
properties, a thorough Site characterization program and Site‐specific risk assessment were performed.
Our response to CPEO’s comment 1 is presented in further detail below.
1 Haley & Aldrich, Inc., 2015, Revised Supplemental Investigation and Risk Assessment Report, 1601 S. California
Avenue, Palo Alto, California, December 21.
Response to Center for Public Environmental Oversight
March 18, 2016
Page 2
After comparing Site sampling results to default screening levels, further evaluation of the vapor
intrusion pathway was performed by comparing concentrations of volatile organic compounds (VOCs)
measured in soil vapor to risk‐based screening levels (RBSLs) that are protective of human health. The
RBSLs were developed with Site‐ and depth‐specific attenuation factors that incorporate soil physical
properties measured at the Site and the specific sampling depth at each soil vapor probe location.
By design, the HHRA included a conservative evaluation of the vapor intrusion pathway. Levels of
conservativism in the evaluation include, but are not limited to, the following:
At locations that were sampled several times, the maximum concentration of VOCs measured in
soil vapor at each sample point were evaluated in the HHRA.
Future residents at the Site were assumed to occupy their homes 24 hours per day for 350 days
a year for 26 years.
Site‐specific risk‐based screening levels were developed using target indoor air concentrations published
by USEPA and DTSC to evaluate cancer risks and non‐cancer adverse health effects.
To support the soil vapor fate and transport evaluation, an analysis was included in the HHRA to
evaluate the sensitivity of the Johnson & Ettinger vapor intrusion model (J&E model) to physical soil
properties and the heterogeneity of soil conditions at the Site (Appendix G, Section 8.3.2.2 of the SIRA
Report). The results of the sensitivity analysis supported the conclusions of the risk assessment. In
addition, a review of the near surface geology at the Site was performed, which supported the modeling
performed in the HHRA.
2. STANFORD’S PLAN DOES NOT SUFFICIENTLY MITIGATE THE RISK OF VAPOR INTRUSION.
Stanford’s proposed mitigation measures are protective of future University Terrace residents and there
is no significant public health risk associated with this development. Mitigation measures, including but
not limited to sub‐slab vapor barriers, were incorporated into the development plan to provide an
additional level of protection that is not required by DTSC. To be conservative, these measures were not
included for risk calculations presented in the HHRA. Specifically, the following measures have been or
will be implemented:
Clean compacted (95% relative density) engineered fill material was placed on Site in the latter
half of 2015 to raise grade up to 15 feet above current grade. Note that this material primarily
was imported from the excavation to construct a subterranean structure at the adjacent
1501/1451 S. California Avenue parcels; soil at these parcels is documented as predominantly
fine grained clay and silt. The fill material was tested for the presence of VOCs and other
constituents prior to use.
Homes, buffered away from the TCE‐impacted areas, will be constructed with 10‐inch thick post‐
tension slabs that are more resistant to cracking. Impacted areas overlying greater TCE
Response to Center for Public Environmental Oversight
March 18, 2016
Page 3
concentrations in soil vapor will be designated for outdoor recreational space, which is
considered acceptable per USEPA guidance.2
Future residents will not be permitted to alter the foundation slab of future homes based on
codes, covenants, and restrictions (CC&Rs); Stanford will retain ownership of the land.
Slab penetrations (e.g., pipes) will be sealed and the foundations will be constructed with vapor
barriers designed to prevent indoor vapor intrusion.
Utility corridors will be constructed with vapor plugs.
Stanford engaged external peer review of its findings and approach. Dr. Paul Johnson, an internationally
renowned expert on vapor intrusion, has reviewed, evaluated and concurred with the Site conceptual
model and Stanford’s approach to address vapor intrusion. A copy of his letter stating his position is
attached.
Our response to CPEO’s comment 2 is presented in further detail below.
CPEO advocates the use of two specific mitigation measures, subslab depressurization and venting
systems, at sites where there is “simply a potential for vapor intrusion.” In contrast, USEPA or Cal‐EPA
recommend evaluating the potential for vapor intrusion by using multiple lines of evidence to develop a
Site Conceptual Model to support informed risk management decisions.2,3 USEPA recommends several
risk management options for developing sites with the potential for vapor intrusion, including
designating areas as recreational space or undeveloped landscape, and constructing buildings with
vapor mitigation technologies. Similarly, DTSC recommends several options relative to the ranges of
risks and hazards that were observed at the Site in the risk management framework included in the
2011 Vapor Intrusion Guidance3 and 2011 Vapor Intrusion Mitigation Advisory.4 In this case, additional
data collection and risk characterization were performed, and potential risks to future residents were
addressed with the reconfiguration of the development plan (i.e., impacted areas are designated for
recreational space).
As described in the SIRA Report, a thorough characterization program was implemented at the Site to
develop and test the Site Conceptual Model. At the 8.5‐acre 1601 S. California Avenue parcel, 130 soil
vapor samples were collected from 118 soil vapor probes installed at 51 locations in 2004 and from 2012
to 2015. To evaluate potential sources of VOCs to the subsurface, soil samples were collected at 16
locations beneath the former building slab and pavement and 11 samples of soil/residual sludge were
collected from subsurface pipes during building demolition in 2015. Soil samples also were collected
from 23 soil borings advanced to depths between 25 and 35 feet bgs where TCE‐impacted soil vapor was
observed (Section 4.2.4 of the SIRA Report). Finally, a detailed stratigraphic analysis of the
2 USEPA, 2015, OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface
Vapor Sources to Indoor Air, Office of Solid Waste and Emergency Response, Publication 9200.2‐154, June.
3 DTSC, 2011, Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (Vapor
Intrusion Guidance), Final, October.
4 DTSC, 2011, Vapor Intrusion Mitigation Advisory, Final, Revision 1, October.
Response to Center for Public Environmental Oversight
March 18, 2016
Page 4
unconsolidated fluvial (stream and floodplain deposits) sediments was performed using boring log data
to construct geologic cross sections.
The following Site Conceptual Model was developed based on the results of the supplemental
investigation activities and historical Site data, including the stratigraphic analysis:
The source of the TCE appears to have been a plating solution sump located in the former Phase
1 building, and potentially a chemical storage area to the southeast. TCE has migrated laterally
from these areas, but the affected area is constrained.
The migration of TCE follows the more permeable and discontinuous channels
Migration of TCE beyond these channels is limited by the denser, more clayey soil conditions
that predominantly characterize the Site, as shown by significantly lower detections of TCE
around the perimeter and in other areas of the Site.
Finally, a HHRA was conducted to evaluate potential human health risks with respect to future
residential development. Based on the results of this HHRA, there is no significant public health risk
associated with future residential development of the Site based on the layout of houses as presented in
the University Terrace development plan. As additional protective measures, several vapor intrusion
mitigation measures will be in place at the University Terrace development. These measures were not
included in the HHRA evaluation (that is, conditions at the Site were evaluated assuming the absence of
protective mitigation measures). Specifically, the measures listed above have been or will be
implemented.
CPEO further states that “Without spending a lot of time calculating attenuation factors and assessing
risk, Stanford should design mitigation into all the new housing, not just at 1601 S. California.” As stated
in its letter, this position is supported with CPEO’s experience with the “Middlefield‐Ellis‐Whisman
(MEW) Superfund Study Area in nearby Mountain View. At the Site, a detailed characterization program
was implemented to support a Site‐specific vapor intrusion evaluation. A comparison of the conditions
at the Site and the MEW Study Area is presented in the attached Table 1. In summary, the MEW Study
Area is not comparable because the geologic and hydrogeologic conditions differ from the 1601
California Avenue Site. At the MEW Study Area, there is continuous water‐bearing stratum at relatively
shallow depths, VOC impacts to groundwater (including TCE) are sourced from multiple industrial sites
and cover an area of approximately 2 miles long by 1.2 mile wide. In contrast, no continuous water‐
bearing zone has been identified in the upper 45 feet of the 1601 California Avenue Site and the VOC
source to soil vapor impacts is localized.
Finally, CPEO indicates that vapor barriers will be used at the Site as a “stand‐alone vapor remedy.”
However, remediation was performed at the Site to remove historic TCE sources. The source of TCE in
the subsurface, the former plating solution sump was excavated and removed on March 19, 2015, and
all subsurface piping, including process, sewer, storm drain lines, subterranean structures and
foundation elements were removed in March and April 2015. Essentially, all potential historic sources of
TCE have been removed from the Site and there is no significant risk to public health associated with the
University Terrace development plan. Mitigation measures, including but not limited to sub‐slab vapor
barriers, were included in the development plan to provide an additional level of protection.
Response to Center for Public Environmental Oversight
March 18, 2016
Page 5
3. THE TECHNICAL DOCUMENTS FOR THE THREE DEVELOPMENT PARCELS DO NOT ADEQUATELY
EXPLAIN THE SOURCES, FATE, AND TRANSPORT OF TCE AT THE SITE.
As discussed above, a Site Conceptual Model that explains the potential sources of TCE in soil vapor,
distribution, conditions that result in its stability, and barriers to its migration was developed and tested
with a thorough Site characterization program. A discussion of the Site Conceptual Model is presented in
the Section 7.0 of the SIRA Report.
Our response to CPEO’s comment 3 is presented in further detail below.
CPEO indicates that the “identification of the TCE source is unconvincing.” However, there is ample
evidence that the primary source of TCE‐impacted soil vapor at the Site was the former plating sump:
TCE was detected in soil samples collected from borings advanced in 1990 and 1991 at the
former location as part of closure activities;
In 2015, TCE was detected in a residual sludge sample collected from a pipe exiting from the
former plating sump at a concentration of 2,200 micrograms per kilogram (µg/kg); and
The highest concentrations of TCE in soil were detected in samples collected from borings
advanced in the vicinity of the former plating sump (EX4‐04 and EX4‐06) at depths between 25
and 35 feet bgs. The maximum detected concentration of TCE was detected in the 35‐foot
sample from boring EX4‐06 at a concentration of 640 µg/kg, which is below the DTSC residential
screening level.
At soil vapor probes located within the footprint of the former chemical storage area (SG‐32, SG‐33, SG‐
34, and SG‐35), TCE was detected at relatively high concentrations in soil vapor (ranging from 9,100 to
110,000 µg/m3, with the highest concentrations detected at SG‐34 at 15 feet bgs [100,000 µg/m3] and
SG‐35 at 25 feet bgs [110,000 µg/m3]). TCE was detected at low concentrations (4.3 to 16 µg/kg) in
shallow soil samples (5 feet bgs) collected at this area (SG‐32, SG‐34, and SG‐35). TCE may have
migrated via preferential pathways from the former plating sump to these areas. TCE is heavier than air
and water, and migrates downward in the soil column along preferential pathways.
In addition, soil samples were collected beneath the slab and pipes during the removal of the building
slab and associated subsurface utilities in March and April 2015. Specifically, soil or residual sludge
samples were collected where 1) soil or sludge was identified within a subsurface pipe, 2) total VOCs
were measured in soil with a portable photo‐ionization detector (PID), or 3) former operational features
(e.g., utility and process water lines) were previously identified. Sixteen soil samples were collected at
beneath the building slab and pavement and an additional 11 samples of soil/residual sludge were
collected directly from subsurface pipes during building demolition in 2015 to evaluate potential sources
of VOCs to the subsurface. TCE was detected at a concentration of 2,200 micrograms per kilogram
(µg/kg) in one sample (PVC‐PIPE) of residual sludge collected directly from a polyvinyl chloride (PVC)
pipe at the former plating sump, indicating the presence of TCE at the sump. TCE was not detected in
any other soil samples collected directly beneath the building slab or pavement, or any residual sludge
Response to Center for Public Environmental Oversight
March 18, 2016
Page 6
samples. Finally, it is important to note that no potential sources of VOCs to the subsurface were
identified at the 1451 and 1501 S. California Avenue parcels.
In summary, the distribution of TCE at and near these potential source areas is well‐defined.
4. GROUNDWATER, SOIL, AND SOIL GAS CONTAMINATED WITH TCE SHOULD BE REMEDIATED AT THE
SITE.
As stated above, remediation to remove all potential sources of TCE was performed at the Site. The
source of TCE in the subsurface, the former plating solution sump was excavated and removed on March
19, 2015. In addition, during building demolition activities all subsurface piping, including process,
sewer, and storm drain lines were removed, as well as all subterranean structures and foundation
elements.
Deep excavation at the Site is not warranted as soil analytical results did not indicate the presence of a
significant source of TCE in soil; rather, it is the soil vapor that is identified as the media of concern at
the Site. Based on the proposed site layout of the future redevelopment project, the results of the HHRA
in conjunction with the University Terrace development plan indicate no significant public health risk on
Site or to the surrounding community. Additionally, excavation is not practical due to 1) the
considerable depth at which excavation could be required (greater than 35 feet below the pre‐
development grade5) to remove vapor‐impacted soil, and 2) the negative impacts to the surrounding
neighborhood. These negative impacts include increased traffic, dust generation, noise, and a much
longer project schedule associated with this type of excavation.
Active remediation technologies, such as soil vapor extraction (SVE), would not likely be effective at this
Site. SVE, a proven technology for remediating coarser‐grained soils, is not practical at this Site due to
the clayey nature of the subsurface lithology which inhibits air flow between soil particles. The lack of air
flow in the subsurface at the Site was demonstrated during Site investigation as no flow conditions6
were encountered during sample collection on at least one occasion at more than 25 percent of the soil
vapor sample probes (that is, a sample could not be obtained due to the lack of soil vapor flow).
A Site‐specific HHRA was conducted to evaluate potential human health risks with respect to future
residential development. Based on the results of this focused HHRA, there is no significant public health
risk associated with future residential development of the Site based on the layout of houses as
presented in the University Terrace development plan. In addition, no public health risk was identified
for the surrounding community. Therefore, there are no requirements for remediation.
Finally, regarding the process that DTSC is following for this Site, the DTSC has reviewed the
Supplemental Investigation and Risk Assessment (SIRA) report for the site, and has concluded that site
characterization is complete and the risk assessment appropriately considers site conditions relative to
5 Note that the site elevation has been raised by up to 15 feet over much of the area where the higher TCE
concentrations in soil vapor were detected.
6 “No flow conditions” refers to the inability to maintain a minimum soil vapor sampling flow rate.
Response to Center for Public Environmental Oversight
March 18, 2016
Page 7
public safety and future site development. With respect to the recommended formal finding, a summary
document to conclude the Preliminary Endangerment Assessment that has been conducted for the Site
will be prepared and reviewed and approved by DTSC. The summary document will summarize the
findings and conclusions from Site characterization reports, and provide the basis for the proposed
action to address the area of the Site where soil vapor has been found to be significantly impacted with
TCE. Land use restrictions are contemplated as an element of the proposed action since the area
currently cannot be used for unrestricted land use. The specific land use restrictions that are proposed
for the area will be identified and defined in the summary document. There will be a public notice prior
to a land use covenant or other mechanism with land use restrictions being put in place, which will give
CPEO an opportunity to provide input.
5. SAMPLING SHOULD BE CONDUCTED TO ENSURE THAT RESIDENTS OF COLLEGE TERRACE ARE NOT
AFFECTED BY TCE CONTAMINATION FOR THIS SITE.
Data collected at the Site adequately characterizes the extent of migration of soil vapor impacted by
TCE. Thus, no additional sampling is necessary.
Based on the sampling and subsequent evaluation conducted for the University Terrace site, soil vapor
with TCE at concentrations exceeding DTSC residential screening levels is more than 200 feet east of
California Avenue and does not extend to California Avenue. A figure that shows soil vapor sampling
locations parallel to California Avenue and highlights those locations where risk levels are below the
DTSC default residential screening level for TCE is attached (Figure 1). This figure additionally illustrates
those locations where concentrations were above screening levels but lower than the de minimis
incremental risk level of one in one million (1 x 10‐6) excess cancer risk, based on the Site‐specific risk
assessment performed for the Site.
Additionally, as shown on Figure 1, soil vapor sampling was conducted across the 1601 S. California
Avenue site in each compass direction to evaluate the distribution of TCE in soil vapor. Soil vapor
samples that did not contain detectable concentrations of TCE also were collected to the west, north,
northeast, and east of data point AMEC‐1 on the 1501 S. California Avenue parcel (note that not all of
these soil vapor sample locations are included on the figures presented in the appendix to the CTRA
letter).
The College Terrace community is safe with respect to potential vapor intrusion to constituents detected
in soil vapor at University Terrace based on several lines of evidence:
The lithology (geologic units) of primarily fine‐grained units along California Avenue inhibits
migration of soil vapor. A cross‐section parallel to California Avenue with concentrations of TCE
measured in soil vapor is presented as Figure 2.
The investigation data consistently indicate the absence of TCE above screening levels outside of
the operational and nearby area on the 1601 S. California Avenue site.
The release of TCE into the subsurface occurred at least several decades ago and all of the
potential sources of TCE (e.g., plating solution sump) were removed during Site demolition. Ten
Response to Center for Public Environmental Oversight
March 18, 2016
Page 8
years of soil vapor data at shallow depths have consistently demonstrated that concentrations
of TCE are below residential screening levels – levels designed to be fully protective of human
health and the environment ‐ except at some locations within and near the former operational
area of the Site.
Attachments:
Table 1 Comparison of Site Conditions, MEW Superfund Study Area, Mountain View and 1601 S.
California Avenue, Palo Alto
Figure 1 Soil Vapor Sample Locations
Figure 2 Cross Section X to X’
Letter from Dr. Paul Johnson to Annette Walton of Stanford dated January 5, 2016
Table 1
Comparison of Site Conditions
MEW1 Superfund Study Area, Mountain View and 1601 S. California Avenue, Palo Alto
MEW Superfund Study Area 1601 S. California Avenue
Depositional Environment Distal edge of Santa Clara Valley Alluvial Plain and
Bay Margin.
Upland margin of the Santa Clara Valley Alluvial
Plain.
Generalized Lithology Gravel, sand, silty and clayey gravels and sands; silts
and clay.
Clay, clayey sand, and subordinate sand with gravel
and clay.
Depth to First Water‐Bearing
Zone
Approximately 10 to 30 feet bgs. Greater than 45 feet bgs, although some lenses of
perched groundwater have been observed at
shallower depths.
VOC Source(s) Regional ‐ multiple sources
14 individual sites (some with multiple addresses)
contribute to the regional groundwater plumes.
Localized
single facility
VOCs of Concern Multiple VOCs, including but not limited to TCE,
tetrachloroethylene (PCE), cis‐1,2‐ dichloroethene,
trans‐1,2‐dichloroethene, and vinyl chloride.
TCE
VOC Concentrations in
Groundwater
TCE – varies; over 10,000 µg/L in certain source areas. TCE – 45 µg/L (maximum)
Soil Vapor Plume(s) area Approximately 2 miles long and ½‐mile wide. Local impact limited to on‐site former operational
area approximately 38,600 square feet (< 1 acre)
VOC = volatile organic compounds
bgs = below ground surface
VI = vapor intrusion
µg/L = micrograms per liter
1 Middlefield‐ Ellis‐Whisman (MEW) Study Area is comprised of three National Priorities List (NPL) or Superfund Sites as well as several other facilities and portions
of the former Naval Air Station Moffett Field Superfund site. The MEW Superfun Area is overseen by the U.S. Environmental Protection Agency. Detailed
information regarding the MEW Study area can be found at http://yosemite.epa.gov/r9/sfund/r9sfdocw.nsf/ViewByEPAID/CAD982463812
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1601 S. CALIFORNIA
1501 S. CALIFORNIA 1451 S. CALIFORNIA
RESIDENTIAL
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AMEC-13
SG-15SG-24SG-21
SG-26
SG-27
SG-29
AMEC-1
AMEC-8
SG-14
SG-38
SG-41
SG-23
SG-28 AMEC-10
SG-19
AMEC-7
SG-16
SG-17
SG-25
SV-8
SV-6
SV-7
SG-37
SG-18
SG-20
SV-1
SVA-2
SV-2
SV-3
SV-4
SV-5
SVA-14
SVA-12
SVA-15
SVA-10
SVA-9
SVA-7
SVA-6
SVA-4SVA-3
SVA-5
SG-39
SG-42
SG-31
SV-1
SV-10
AMEC-11
SV-9
SV-3
AMEC-12
SV-2
AMEC-2
AMEC-4
AMEC-9
SV-1
SV-3
SV-4
AMEC-3SV-11
SV-6
SV-7SV-8
SV-9
SV-10
SV-12
SV-4
SV-13
SV-7
SV-15
SV-5SV-6
SV-14
SV-8
SV-11
NOTES
1. THE 1451, 1501, AND 1601 S. CALIFORNIA AV ENUE PARCELSCOM PRISE THE UNIV ERSITY TERRACE PROJECT.
2. DEV ELOPM ENT PLAN SOURCE: W ILLIAM HEZ M ALHALCHARCHITECTS INC., REV ISED SITE PLAN, 9-23-2015.
3. µg/m 3 = M ICROGRAM S PER CUBIC M ETER
4. AERIAL IM AGERY SOURCE: ESRI
1451, 1501 AND 1601 S. CALIFORNIA AV ENUEPALO ALTO, CALIFORNIA
SOIL V APOR SAM PLE LOCATIONS
FIGURE 1SCALE: AS SHOW NFEBRUARY 2016
LEGEND
@@A DENOTES TCE W AS NOT DETECTED IN ANY SAM PLES AT ACONCENTRATION EXCEEDING THE RESIDENTIALSCREENING LEV EL (480 µg/m
3)
@@A DENOTES TCE W AS NOT DETECTED IN ANY SAM PLES AT ACONCENTRATION EXCEEDING AN ESTIM ATED LIFETIM EEXCESS CANCER RISK OF ONE-IN-A-M ILLION (1X10
-6 )
@@A DENOTES TCE W AS DETECTED IN AT LEAST ONE SAM PLE ATA CONCENTRATION EXCEEDING AN ESTIM ATED LIFETIM EEXCESS CANCER RISK OF ONE-IN-A-M ILLION (1X10
-6 )
PROPERTY BOUNDARY
0 100 200
SCALE IN FEET
110
100
90
80
70
60
50
40
30
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VERTICAL SCALE
SCALE IN FEET
HORIZONTAL SCALE
SV-1
SV-2
SG-20
SG-31
SG-18
SG-17 SV-8
SV-10 AMEC-11 AMEC-12
EB-8
EB-14
EB-3
SG-19
44 W
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51 E 19 E
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GROUND SURFACE ELEVATION
ALONG SECTION LINE (SEE NOTE 4)<8
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1451, 1501 AND 1601 S. CALIFORNIA AVENUE
PALO ALTO, CALIFORNIA
CROSS SECTION X TO X'
FIGURE 4SCALE: AS SHOWN
FEBRUARY 2015 22016
SV-10
2 W
<100
GEOLOGIC EXPLANATION BOREHOLE SYMBOLS
FILL
SILTS AND CLAYS (FINE GRAINED
UNITS)
CLAYEY GRAVELS AND SANDS
(COARSE GRAINED UNITS)
BORING DESIGNATION
OFFSET DISTANCE BETWEEN BORING AND
CROSS SECTION LINE (FEET)
STRATUM BOUNDARY
NO FLOW CONDITIONS DURING
SOIL VAPOR SAMPLING
MAXIMUM DETECTED SOIL VAPOR CONCEN-
TRATION OF TRICHLOROETHENE (TCE) IN
MICROGRAMS PER CUBIC METER
TCE NOT DETECTED IN SOIL VAPOR
SAMPLE. CONCENTRATION INDICATED IS
THE TEST DETECTION LIMIT
SG-17
16 W
NF
300
<8
NOTES:
1. REFER TO FIGURE 1- SITE VICINITY WITH DEVELOPMENT
PLAN AND CROSS SECTIONS, FOR PLAN LOCATION, DESIG-
NATION, AND ORIENTATION OF SUBSURFACE SECTIONS
AND AS-DRILLED EXPLORATION LOCATIONS.
2. TEST BORING GROUND SURFACE ELEVATIONS WERE
ESTIMATED AND SHOULD BE CONSIDERED APPROXIMATE.
3. SATURATED SOIL CONDITIONS WERE NOT ENCOUN-
TERED IN ANY OF THE TEST BORINGS SHOWN ON THIS
SECTION.
4. BORINGS SHOWN ABOVE AND BELOW THE GROUND
SURFACE ELEVATION ARE PROJECTED ONTO THE SECTION.
THE TOP OF BORING REPRESENTS THE GROUND SURFACE
ELEVATION AT THE LOCATION WHERE THE BORING WAS
DRILLED.
CROSS SECTION LOCATION PLAN
LIMITS OF 1601 S. CALIFORNIA PROPERTY LIMITS OF 1501 S. CALIFORNIA PROPERTY LIMITS OF 1451 S. CALIFORNIA PROPERTY
January 5, 2016
Annette Walton
Director - Environmental Management Real Estate Operations
3160 Porter Drive, Suite 200
Palo Alto, California 94304
Dear Annette –
As requested, this letter briefly summarizes key points of my review and our discussions related
to the health risk assessment and development plans at Stanford’s University Terrace Project,
which involves the redevelopment of three former industrial-use properties to a neighborhood
consisting of Stanford faculty housing and open park space.
No further action letters were issued in 2013 by the California State Department of Toxic
Substances Control (DTSC) for two of the properties (1451 and 1501 California Avenue, Palo
Alto, CA). Based on environmental reports provided to DTSC, they concluded that neither site
posed a significant threat to human health or the environment under residential land use.
Thus, my involvement has been focused on the third property at 1601 California Avenue, for
which supplemental investigation was conducted to thoroughly assess the potential for
significant health risks from post-remediation TCE residuals at depth in the subsurface. That
assessment is summarized in the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California, prepared by Haley & Aldrich, Inc.
Key points from my review and our discussions include the following:
Relative to the initial draft, conclusions in the final version of the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California were the same,
but strengthened by the thorough evaluation of the site conceptual model conducted by Murray
Einarson and the expanded range of site-specific inputs that were incorporated by Haley &
Aldrich, Inc. in their calculations. These additions increased confidence in the conclusions
stemming from vapor intrusion pathway analysis because the selection of defensible site-specific inputs and considering a range of possible scenarios is critical to generating confidence in the
results. It was also critical, because subsurface geology is a key controlling factor for vapor
migration at this site.
There is confidence in the use of the site data for the risk analysis because the historical information, subsurface geology conceptual model, and chemical distribution appear to be self-
consistent.
The site plan for the University Terrace Project reflects the analysis and conclusions contained in
the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California. Future residences are placed in areas with projected negligible risks and the
relatively isolated area of possible concern is open park space in the plan.
The risk assessment report concludes that the future residences will not be exposed to significant
health risks under any building construction design and that pre-emptive building-specific
mitigation measures are not needed (e.g., sub-slab depressurization systems). The sub-foundation
vapor barrier liners being incorporated in the residential construction, therefore, are not necessary, but will add an additional level of protectiveness from vapor intrusion and potential
comfort for the occupants.
Development plans also address the potential for vapor intrusion via alternative pathways, as we
discussed recent studies where vapor intrusion was observed in buildings off-set from subsurface vapor sources as a result of transport along utilities and utility conduits. The potential for this is
being eliminated in the planned development design by ensuring that utilities are not run through
the residual vapor source at the site and by having vapor plugs/seals installed along the utilities.
Should you have questions or require clarification of this summary, please feel free to contact me.
Sincerely,
Paul C. Johnson, Ph.D.
RESPONSE TO COLLEGE TERRACE RESIDENTS’ ASSOCIATION
March 18, 2016
SUBJECT: Response to College Terrace Residents’ Association (CTRA) Comments
Summary: This document provides responses to questions raised by the College Terrace Residents’
Association (CRTA) in its January 26, 2016 letter to the Department of Toxic Substances Control (DTSC)
regarding environmental conditions at the University Terrace development located at 1451, 1501, and
1601 S. California Avenue in Palo Alto, California. Because subsurface chemical impacts were primarily
detected at the 1601 S. California Avenue parcel and it is the focus of the current Preliminary
Endangerment Assessment, this parcel is referred to by its address or as the “Site.” References to the
other parcels that comprise the University Terrace development are referred to by their respective
addresses. The responses to questions asked and supporting information provided below were prepared
jointly among the DTSC; Stanford University, Office of Real Estate (Stanford), the property owner and
developer; and its technical consultant, Haley & Aldrich, Inc.
In its letter, CTRA provides comments and recommendations to address the presence of trichloroethene
(TCE) in the subsurface at the University Terrace development. As indicated in our response below,
which includes supporting information and figures, we have concluded the following:
The Site has been thoroughly investigated and evaluated.
The extent of chemical impacts to soil vapor are defined.
The development plan is protective of human health.
No additional testing at the Site or adjacent properties is needed.
Dr. Paul Johnson, an internationally renowned expert on vapor intrusion, reviewed, evaluated
and concurred with Stanford’s findings and approach to address vapor intrusion.
Questions/Answers: Specific responses to the nine questions and sub‐questions provided by CTRA are
addressed below with CRTA’s “top‐level” questions shown in italics.
1. HOW CAN WE KNOW THAT THE TCE LEVELS ACROSS CALIFORNIA AVE IN COLLEGE TERRACE, WHERE
HOMES HAVE NO VAPOR INTRUSION MITIGATION, ARE SAFE?
A thorough characterization program was implemented at the Site to evaluate the extent of TCE in soil
vapor. Key points regarding the distribution of TCE in soil vapor are summarized below:
Soil vapor sampling was conducted radially (i.e., extended laterally) and at multiple depths from
the on‐Site source area until the extent of TCE in soil vapor was fully defined.
The sampling pattern and analytical results demonstrate that TCE impacts in soil vapor are
defined and contained within the operational area of the Site.
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There are 15 soil vapor sampling locations collected parallel to California Avenue and opposite
the College Terrace community in which analytical results show that TCE either was not
detected or detected below the DTSC residential screening level. These results lead to the
conclusion that TCE‐impacted soil vapor does not extend off Site to S. California Ave.
Clayey soil beneath the Site inhibits the vertical and lateral migration of TCE in soil vapor (that is,
vapors have a hard time moving through clay). Borings drilled at the site found the presence of
clayey soil at shallow depths at the northern and western portion of the Site, as well as at other
boring locations throughout the Site. More permeable and discontinuous units were also
observed in the characterization borings located throughout the Site. These coarser grained
units at the Site, where higher concentrations of TCE in soil vapor were detected at some
locations, contain a considerable fraction of finer‐grained (clayey) soil.
A Site‐specific risk assessment identified locations on‐Site where the soil vapor results exceed
the threshold incremental risk level of one in one million (1 x 10‐6) excess cancer risk; the
exceedances are all within and immediately adjacent to the former operational area of the Site.
Stanford will not construct homes over these locations or within an established buffer zone.
A Site conceptual diagram of the environmental conditions relative to the Site development is shown on
Figure 1. No additional investigation or remediation (see CTRA question 2) is necessary for the Site or
surrounding area.
Our response to CTRA question 1 is presented in further detail below.
An iterative approach was implemented, so that the extent of TCE impact was clearly defined in all
directions at depths down to 25 to 35 feet below ground surface (bgs) from the area identified as the
source of the release. At the 8.5‐acre 1601 S. California Avenue parcel, 130 soil vapor samples were
collected at multiple depths from 118 soil vapor probes installed at 51 locations in 2004 and from 2012
to 2015. To evaluate potential sources of volatile organic compounds (VOCs) in the subsurface, soil
samples were collected at 16 locations beneath the building slab and pavement, and 11 samples of
soil/residual sludge were collected from subsurface pipes during building demolition in 2015. Soil
samples were also collected from 23 soil borings advanced to depths between 25 and 35 feet bgs where
TCE‐impacted soil vapor was observed. Finally, a detailed stratigraphic analysis of the unconsolidated
fluvial (stream and floodplain deposits) sediments was performed using boring log data to construct
geologic cross sections.
As presented in the Supplemental Investigation and Risk Assessment (SIRA) Report,1 which has been
reviewed and commented on and is supported by DTSC, data collected at the California Avenue parcels
demarcate the extent of soil vapor impacted by TCE. Based on the sampling and subsequent evaluation
conducted for the Site, soil vapor with TCE at concentrations exceeding DTSC residential screening levels
occurs more than 200 feet east of California Avenue and does not extend to California Avenue. A figure
that shows soil vapor sampling locations parallel to California Avenue and highlights those locations
where risk levels are below the DTSC default residential screening level for TCE is attached (dark blue
1 Haley & Aldrich, Inc., 2015, Revised Supplemental Investigation and Risk Assessment Report, 1601 S. California
Avenue, Palo Alto, California, December 21.
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circles; Figure 2). This figure additionally illustrates those locations where concentrations were above
screening levels but lower than the de minimis incremental risk level of one in one million (1 x 10‐6)
excess cancer risk (light blue circles), based on the Site‐specific risk assessment performed.
As additionally shown on Figure 2, soil vapor sampling was conducted across the 1601 S. California
Avenue Site in each compass direction to evaluate the distribution of TCE in soil vapor. Soil vapor
samples that did not contain detectable concentrations of TCE also were collected to the west, north
northeast, and east of data point AMEC‐1 on the 1501 S. California Avenue parcel (note that not all of
these soil vapor sample locations are included on the figures developed by CRTA, which are included as
an appendix in their letter).
The College Terrace community is safe with respect to potential vapor intrusion of constituents detected
in soil vapor at University Terrace based on several lines of evidence:
Clayey soil inhibits the migration of TCE in soil vapor. The lithology (soil type) of primarily
fine‐grained soil along California Avenue (cross‐section presented on Figure 3) inhibits
migration of soil vapor.
The investigation data consistently indicate an absence of TCE above screening levels
outside of the operational and nearby area on the 1601 S. California Avenue Site, as shown
on Figure 2.
The release of TCE into the subsurface occurred at least several decades ago and all of the
potential sources of TCE (e.g., plating solution sump) were removed during Site demolition.
Ten years of soil vapor data at shallow depths have consistently demonstrated that
concentrations of TCE are below residential screening levels – levels designed to be fully
protective of human health and the environment ‐ except at some locations within and near
the former operational area of the Site.
CTRA has asked about the screening level used in the analysis of site conditions and whether a lower
screening level may be appropriate. Note that screening levels are used to facilitate an initial evaluation
of site characterization data. If a screening level is exceeded, it does not indicate that a health risk exists,
but rather that additional evaluation is warranted, such as additional sampling or risk characterization.
With respect to the detections of TCE at 1601 S. California Avenue, a thorough site characterization
program and site‐specific risk assessment subsequently were performed. The risk assessment was
performed on a point by point basis, with all sampling locations and analytical data incorporated. The
need for mitigation and/or remediation is determined by the results of this site‐specific evaluation.
The attenuation factor used by DTSC to initially evaluate the presence of TCE in soil vapor is different
than that presented in the U.S. Environmental Protection Agency’s (USEPA’s) 2015 guidance document.
During the January 6, 2016, meeting with representatives of CTRA, Stanford, and the DTSC, Dr. Kimiko
Klein, DTSC Staff Toxicologist, discussed reasons why the USEPA screening level is not used at DTSC‐
regulated sites in California. Dr. Klein stated that there are several limitations to the use of the USEPA
empirical database of paired indoor air and subsurface data points; among them, the database from
which the USEPA derived its factor is from sites across the country, and includes sites where extreme
cold weather conditions enhance vapor migration into homes. Such weather conditions do not exist at
the 1601 California Avenue site and vicinity, or other locations in the Bay Area. Other important factors,
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such as soil type or sample depth, were not accounted for in the USEPA attenuation factor used to
derive its suggested screening level.
As part of question 1, CTRA commented that TCE was detected in groundwater samples collected at
1601 S. California Avenue as part of the groundwater monitoring and extraction program associated
with a site located on Page Mill Road on behalf of Hewlett Packard (HP). The groundwater investigations
completed at the nearby Page Mill Road site provide important information regarding the depths of
groundwater zones.
Groundwater extraction and monitoring at 1601 S. California Avenue related to the Page Mill
Road site is focused on very deep strata (Lower Santa Clara Formation), at depths greater than
250 feet. Consequently, there is 250 feet of fine‐grained sediments that exist between the deep
VOCs, including TCE, in groundwater and the ground surface, preventing exposure to vapor
receptors.
In 2013, the California Regional Water Quality Control Board, San Francisco Bay Region (Water
Board), which is the oversight agency for the Page Mill Road site, determined that VOC
concentrations in the deep water bearing zones beneath the 1601 S. California site were
sufficiently low so that the groundwater monitoring wells located on that site were no longer
needed, and granted its approval to close and remove the wells. The letter and subsequent
email from the Water Board describing the rationale for decommissioning and destroying the
wells is attached.
Note that shallow groundwater beneath the 1601 S. California Avenue site and near College
Terrace is within a different and much younger geologic unit (Quaternary alluvium) than the
deeper strata being addressed as part of the Page Mill Road remediation program. Site specific
geologic analysis, local topography, and regional monitoring data support an overall
groundwater flow direction to the east‐ northeast, that is, away from College Terrace, in the
shallow alluvium beneath the 1601 S. California Ave. site.
Finally, as part of its remediation program, groundwater extraction and treatment is ongoing at
the Page Mill Road site under the regulatory oversight of the Water Board. Groundwater
extraction removes chemical mass from the subsurface and also inhibits further movement of
impacted groundwater. Site remediation will continue until the Water Board deems that site
cleanup is adequate for protection of human health and the environment. This program
provides additional assurance that properties within the vicinity of the Page Mill Road site will
continue to be protected from the historical groundwater impacts.
2. WHY NOT REQUIRE REMEDIATION OF THE TCE CONTAMINATION?
Remediation was performed at the Site to remove TCE sources. The source of TCE in the subsurface, the
former plating solution sump, was excavated and removed on March 19, 2015. In addition, during
building demolition activities (conducted from March 19 to April 17, 2015), chemical storage areas, all
subsurface piping, including process, sewer, and storm drain lines were removed, as well as all
subterranean structures and foundation elements. This means that all potential historic sources of TCE
have been removed from the Site.
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A Site‐specific human health risk assessment (HHRA) was conducted to evaluate potential human health
risks with respect to future residential development. The results of this HHRA, show there is no
significant public health risk associated with the design of the future residential development of the Site
based on the layout of houses as presented in the University Terrace development plan. For the small
land area where the risk exceeds one‐in‐a‐million, the construction of new homes or other structures
will be prohibited with the adoption of a land use restriction. Finally, no public health risk was identified
for the development or surrounding community.
Our response to CTRA question 2 and sub‐questions is presented in further detail below.
A thorough Site characterization program was implemented during and following building demolition to
delineate and develop an approach to address TCE‐related impacts in the subsurface:
Soil samples were collected beneath the slab and pipes during the removal of the building slab
and associated subsurface utilities in March and April 2015. Specifically, soil or residual sludge
samples were collected where 1) soil or sludge was identified within a subsurface pipe, 2) total
VOCs were measured in soil with a portable photo‐ionization detector (PID), or 3) former
operational features (e.g., utility and process water lines) were previously identified. Sixteen soil
samples were collected from beneath the building slab and pavement and an additional 11
samples of soil/residual sludge were collected directly from subsurface pipes during building
demolition in 2015 to evaluate potential sources of VOCs to the subsurface.
o TCE was detected at a concentration of 2,200 micrograms per kilogram (µg/kg) in one
sample (PVC‐PIPE) of residual sludge collected directly from a polyvinyl chloride (PVC)
pipe at the former plating sump, indicating that a solution containing TCE had passed
through the sump. No visual indications or PID measurements were observed in shallow
soil at the former sump during the removal of sump. Therefore, no additional soil
samples were collected during demolition. However, this area was further evaluated
with the collection of soil samples at 5 foot intervals to a depth of 35 feet bgs from soil
boring EX4‐02, which was advanced at the location of the former sump. The maximum
detected concentration of TCE in soil samples collected at EX4‐02 was 26 µg/kg at 15
feet bgs, which is below the Regional Screening Level (RSL) for residential soil (940
µg/kg) published by USEPA (2015) and endorsed by DTSC (2015).
o TCE was not detected in any of the other 16 soil samples or 10 soil/residual sludge
samples collected directly beneath the building slab or pavement at the utility or
process lines, or where visual indications or PID detections were observed.
Soil samples also were collected from 23 soil borings (including EX4‐02) advanced to depths
between 25 and 35 feet bgs following Site demolition. The analytical results from these efforts
are presented in the SIRA Report. TCE concentrations in soil beneath the former operational
area, where detected, ranged from 4.3 µg/kg (SG‐02 at 5 feet bgs) to 640 µg/kg (EX4‐06 at 35
feet bgs); the Regional Screening Level (RSL) for residential soil published by USEPA (2015) and
endorsed by DTSC (2015) is 940 µg/kg. The results did not indicate the presence of a significant
source of TCE in soil.
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Finally, it is important to note that no potential sources of VOCs to the subsurface were
identified at the 1451 and 1501 S. California Avenue parcels.
The results of this sampling and monitoring program indicated that excavation of impacted soil is not
necessary at the Site as the analytical results for soil samples did not indicate the presence of a
significant source of TCE in soil; rather it is the soil vapor that is identified as the media of concern at the
Site.
Finally, the approach for addressing residual concentrations of TCE in soil vapor at the Site is consistent
with DTSC guidance. As described in the DTSC risk management framework (2011 Vapor Intrusion
Guidance), several activities are recommended for the ranges of risks and hazards observed at the Site
(i.e., risks between 1x10‐6 to 1x10‐4 and hazards greater than 1.0). In this case, additional risk
characterization was performed and the development plan was reconfigured to mitigate potential risks
to future residents. A Site‐specific HHRA evaluated concentrations of TCE measured in soil vapor to
determine potential human health risks with respect to future residential development. Based on the
results of this HHRA, there is no significant public health risk associated with future residential
development of the Site based on the layout of houses as presented in the University Terrace
development plan; however, Stanford has elected to implement additional protective measures to
guard against vapor intrusion (including engineering and institutional controls) at the University Terrace
development. To be conservative, these measures were not included in the risk calculations presented
in the HHRA. Specifically, the following measures have been or will be implemented:
Clean compacted (95% relative density) engineered fill material was placed on Site in the latter
half of 2015 to raise grade up to 15 feet above the post‐demolition grade. Note that this
material primarily was clean, fine‐grained imported fill from the excavation to construct a
subterranean structure at the adjacent 1451 and 1501 S. California Avenue parcels. Soil at these
parcels is documented as predominantly fine grained clay and silt. Chemical testing of the fill
material showed that it did not contain VOCs and other harmful constituents prior to use. The
additional clean fill material increases the depth to TCE‐impacted soil vapor, compared to the
depth evaluated in the HHRA.
Homes, buffered away from the impacted areas, will be constructed with 10‐inch thick post‐
tension slabs that are more resistant to cracking. Impacted areas overlying greater TCE
concentrations in soil vapor will be designated for outdoor recreational space, which is
considered acceptable per USEPA guidance.2
Future residents will not be permitted to alter the foundation slab of future homes based on
codes, covenants, and restrictions (CC&Rs); Stanford will retain ownership of the land.
Slab penetrations (e.g., pipes) will be sealed and the foundations will be constructed with vapor
barriers designed to prevent indoor vapor intrusion.
2 USEPA, 2015, OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface
Vapor Sources to Indoor Air, Office of Solid Waste and Emergency Response, Publication 9200.2‐154, p. 150, June.
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Utility corridors that will run through the area where TCE was detected in soil vapor will be
constructed with vapor plugs.
Note that Stanford engaged external peer review of its findings and approach. Dr. Paul Johnson, an
internationally renowned expert on vapor intrusion, reviewed, evaluated and concurred with the Site
conceptual model and Stanford’s approach to address vapor intrusion. A copy of his letter stating his
position is attached.
a. If TCE is not in the groundwater as the Risk Assessment and Stanford state (but we have
reasons to doubt), then why not just dig out contaminated soil?
b. If TCE is in fact in the groundwater, and cannot be remediated by mere removal, why not
mandate appropriate mitigation strategies?
With respect to specific remediation technologies:
As described above, soil sampling at the Site did not reveal concentrations of TCE in soil that would
warrant deep excavation, and the results of the HHRA in conjunction with the University Terrace
development plan indicate no public health risk on Site or to the surrounding community. Additional
excavation at the Site is not necessary, as analytical results for soil samples did not indicate the presence
of a significant source of TCE in soil, but rather are indicative of TCE in the vapor phase. Additionally,
excavation is not practical due to 1) the considerable depth at which excavation could be required to
remove vapor‐impacted soil (greater than 35 feet below the pre‐development grade3), and 2) the
negative impacts to the surrounding neighborhood. These negative impacts include increased traffic,
dust generation, noise, and a much longer project schedule associated with this type of excavation.
Active remediation technologies, such as soil vapor extraction (SVE), would not likely be effective at this
Site. SVE, a proven technology for remediating coarser‐grained soils, is not practical at this Site due to
the clayey nature of the subsurface lithology which inhibits air flow between soil particles. The lack of air
flow in the subsurface at the Site was demonstrated during Site investigation as no flow conditions4
were encountered during sample collection on at least one occasion at more than 25 percent of the soil
vapor sample probes (that is, a sample could not be obtained due to the lack of soil vapor flow).
3. HOW WIDESPREAD IS TCE ON THE UNIVERSITY TERRACE SITE?
The extent of TCE‐impacted soil vapor at the University Terrace development is defined; Figure 17 of the
SIRA Report graphically illustrates that TCE is not only defined by its location/extent, but also by the
potential incremental excess cancer risk (defined as a 1 x 10‐6 threshold) that soil vapor at that location
could pose to an individual. Additionally, the distribution of soil vapor is discussed in detail in Section 7.2
(titled “Distribution”) of the SIRA Report. In Figure 17, the orange circles represent TCE that would
exceed the residential risk threshold. Note that sample depths are based on the pre‐development grade,
3 Note that the site elevation has been raised by up to 15 feet over much of the area where the higher TCE
concentrations in soil vapor were detected.
4 “No flow conditions” refers to the inability to maintain a minimum soil vapor sampling flow rate.
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which subsequently has been filled by up to 15 feet of clean fill where higher TCE concentrations have
been detected. Every data point that is not orange represents locations where TCE concentrations in soil
vapor, if present, do not represent incremental health risk above the de minimis 1 x 10‐6 threshold. The
sampling strategy and risk assessment provide the supporting information that demonstrates TCE‐
impacted soil vapor does not extend beyond the 1601 S. California Avenue Site, with the exception of
one soil vapor sample location at 1501 S. California Avenue that is located directly adjacent to the 1601
S. California Avenue parcel. At that one location (AMEC‐1), TCE was detected in soil vapor at depths of
15 and 25 feet bgs at concentrations exceeding the DTSC residential screening level. However, TCE was
detected at a concentration below the DTSC residential screening level in a sample collected at 8 feet
bgs at that location. These results were further evaluated with a site‐specific risk assessment, which
indicated the presence of TCE at that location does not represent incremental health risk above the de
minimis one‐in‐a‐million threshold. TCE was not detected in soil vapor collected at nearby sampling
points at 1501 S. California Avenue at concentrations exceeding the DTSC screening level. The data
evaluation and results for 1501 S. California Avenue are fully discussed and described in the October
2013 report titled “Additional Environmental Investigation Results and No Further Action Request.” For
1601 S. California Avenue, the data evaluation and results are fully discussed and described in the SIRA
Report.
Our response to CTRA question 3 is presented in further detail below.
The attached Figure 2 that is provided with this memorandum illustrates soil vapor sampling locations at
each of the 1451, 1501, and 1601 S. California Avenue parcels (the University Terrace development).
(Note that not all of these soil vapor sample locations, particularly at 1501 S. California Avenue, are
included on the figures developed by CRTA and included as an appendix in their letter). The data
generated from these sampling locations demonstrate that the extent of impacts to soil vapor at the Site
are defined and primarily isolated to the former operational area at 1601 S. California Avenue. An
extensive evaluation of Site lithology has been conducted; the information generated through this
evaluation confirms that vapor concentrations are highest in coarser grained units (that is, coarser‐
grained soil in a clayey matrix) and that the finer‐grained, clayey soil effectively retards the migration of
TCE‐impacted soil vapor in the subsurface. The CTRA letter notes that elevated concentrations of TCE in
soil vapor exist from the sump area in an easterly direction; this distribution of TCE in soil vapor is
consistent with the observed, coarser‐grained lithology.
There is no evidence groundwater is a significant transport mechanism for TCE at the University Terrace
development. As discussed at the January 6. 2016, meeting, a continuous water‐bearing unit has not
been observed in the upper 40 feet of the 1601 S. California Avenue Site, and borings have been
advanced as deep as 68 feet without encountering saturated deposits. Figure 4 illustrates borings that
have been drilled to at least 25 feet below ground surface across the three parcels, i.e., including 1451
and 1501 S. California Avenue, and indicates whether saturated soil/groundwater has been observed
across the overall project Site. Analytical results are presented for these locations on Figure 5, indicating
that TCE was detected in groundwater at two of the nine locations (45 micrograms per liter [µg/L] at
SBA‐9 and 13 µg/L at GW‐20) at concentrations below the Environmental Screening Level (170 µg/L)
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published by the Water Board for the evaluation of potential vapor intrusion.5 Those results do not
represent a significant impact to groundwater.
At 1601 S. California Avenue, only a thin interval of saturated soil at approximately 29.5 feet bgs was
observed in the borehole (SBA‐9) from which a groundwater sample was obtained. The soil at that
location was documented as “poorly graded sand with clay.” The remainder of the lithology at that
boring location was documented as “clays and clayey sands” (i.e., finer‐grained units) and no other
observations of saturated soil were made.
As described in the response to CTRA question 1, TCE impacts to groundwater reported beneath the Site
as part of the Page Mill Road project were detected at depths greater than 250 feet bgs and were
addressed under the oversight of the Water Board.
4. IS THE TCE FROM THE 1601 CALIFORNIA AVE SPILL(S) IN THE GROUNDWATER?
Yes, TCE has been detected in shallow groundwater beneath the Site, but site data indicate that
concentrations are low, limited in extent, and below the environmental screening levels (ESLs) for
groundwater and would not contribute to vapor intrusion. Fifty‐four exploratory borings were advanced
to assess the nature and extent of VOCs at the University Terrace site. Locations of those borings were
selected based on knowledge of suspected release areas and former site features (e.g., plating solution
sump), to assess potential impacts from off‐Site sources, and to provide general coverage of the area.
Collection of groundwater samples was attempted at 12 locations. Sufficient groundwater from which to
obtain a sample was present in 9 of the 12 borings. TCE was detected at low concentrations in two of
those samples (45 µg/L at SBA‐9 and 13 µg/L at GW‐20). These groundwater data indicate that the TCE‐
impacts to groundwater are limited.
One of CTRA’s comments discussed the possibility of continuous meandering channels beneath the Site
which could serve as potential pathways for aqueous or vapor‐phase contaminant migration. As noted
above, a continuous shallow water‐bearing unit has not been encountered to the depths of borings that
have been drilled at the 1601 S. California Avenue Site, and the distribution of TCE in soil relative to the
Site lithology does not support the existence of a meandering channel. Further, meandering channels,
even if they were present beneath the Site, would not constitute pathways from the 1601 California
Avenue Site to the CRTA neighborhood. Figure 6 presents the locations of historical streams in the
vicinity of the 1601 S. California Avenue Site and the College Terrace community. These streams follow
the general topography of the area. As indicated by the San Francisco Estuary Institute’s Historical
Ecology Atlas and USGS topographic maps (1953), historical streams did not cross the 1601 S. California
Avenue Site or trend from the Site into the College Terrace neighborhood.
In addition to the historical streams, the detailed lithologic information obtained from the numerous
borings at the 1601 S. California Avenue Site did not identify subsurface stream channels that trend
5 The residential groundwater Environmental Screening Level (ESL) for the evaluation of vapor intrusion concerns
(fine‐coarse soil type) for TCE is 170 µg/L (Water Board, 2016, Environmental Screening Level Tables, Interim Final,
February).
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towards the College Terrace neighborhood. Instead, the discontinuous coarser‐grained units interpreted
as subsurface channels are interspersed within finer‐grained, clayey deposits.
Although a low concentration of TCE (13 µg/L from the depth interval of 52.5to 55.0 feet bgs at GW‐20)
was detected in one groundwater sample collected at the 1501 S. California Avenue parcel, it was below
the ESL6 published by the Water Board for the evaluation of potential vapor intrusion. If groundwater
was a transport mechanism for TCE, then TCE would be expected to be more widely distributed and
detected in soil vapor at 1501 S. California Avenue, and that is not the case, as discussed below.
Furthermore, AMEC concluded that it is likely that the presence of TCE in soil vapor at 1501 S. California
Avenue is attributed to limited vapor migration from 1601 S. California Avenue, as no source for TCE
impacts was identified at the 1501 S. California Avenue parcel. Importantly, DTSC reached the same
conclusion and noted that the sump at 1601 S. California Avenue was the likely source of the soil vapor
impact.
Finally, the conclusion that groundwater is not a significant transport mechanism is supported by soil
vapor samples collected at AMEC‐1 and the surrounding area at 1501 S. California Avenue. TCE was not
detected at a concentration exceeding the DTSC residential screening level in the soil vapor sample
collected at 8 feet bgs at AMEC‐1, and TCE was not detected in soil vapor at the surrounding locations.
Those results indicate that:
The proximity to TCE‐impacted soil vapor at 1601 S. California Avenue and lithology at this
location (AMEC‐1) allowed for the migration of TCE in soil vapor.
The migration of TCE in soil vapor is inhibited by fine‐grained, shallow soil.
TCE‐impacts to soil vapor do not extend beyond AMEC‐1.
The absence of TCE in soil vapor beyond AMEC‐1 provides additional evidence that groundwater
is not a transport mechanism for TCE.
Thus, TCE detected in soil vapor samples at AMEC‐1 are not indicative of a groundwater source.
5.IS THERE A POTENTIAL TCE CONTAMINATION FROM STORM WATER RUN‐OFF?
No. There is no possibility for TCE detected in soil and soil vapor to impact storm water runoff at the
Site, as described below. Stanford is managing storm water runoff at the University Terrace
development under a general permit issued by the Water Board. Storm water was tested on January 27,
2016 prior to off haul,7 which was required to meet a storage capacity issue. As expected, no VOCs,
including TCE, were detected. Stanford provided the Storm Water Unit of the Water Board this
information in support of this conclusion on February 3, 2016.
6 Water Board, 2016, Environmental Screening Level Tables, Interim Final, February.
7 Ground Zone Environmental Services, 2016, Letter regarding potential for TCE contamination to be released to
storm water during construction activities at 1501 and 1601 California Avenue, Palo Alto, California, February 2.
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Soil
The presence of TCE in soil was explored by collecting soil samples at multiple depths at 26 locations in
and around the operational areas of the Site.
At those locations where TCE was detected in soil, clean fill ranging in thicknesses from 5 to 15
feet has been placed atop as part of the surface grading for the development (the average depth
of the fill is approximately 12 to 13 feet over these sample locations).
No fill has been placed over 4 of the 26 sampling locations; at three locations, no TCE was
detected in soil. At the fourth location, the first detection of TCE in soil was detected at a depth
of 10 feet below ground surface.
Soil Vapor
With respect to storm water runoff, there is not a complete pathway for impacted soil vapor to come
into contact with storm water runoff at the Site. During rain events, surficial soil is saturated—the pore
spaces between soil particles are filled with water. TCE in soil vapor cannot migrate through saturated
soils and into storm water runoff.
At the Site, the area over which higher TCE concentrations in soil vapor have been detected also are
covered with clean fill that ranges up to 15 feet. Rain in contact with the ground surface will not take up
TCE from subsurface soil or soil vapor.
6. COULD BUILDING DEMOLITION HAVE IMPACTED THE TCE LOCATIONS?
No. Building demolition would not impact the distribution of TCE in soil vapor at the Site. It is possible
that building demolition could have caused some vibration; however, the subsurface structure of the
clayey soil would not be altered by this vibration, and the TCE, which moves by diffusion through the soil
pores, would not be triggered or enhanced by this short‐term vibration. The clay would continue to
effectively retard the migration of TCE impacted soil vapor.
7. WHAT WAS OR WERE THE SOURCE(S) OF THE TCE CONTAMINATION DISCOVERED AFTER THE 1601
CALIFORNIA AVE BUILDINGS (1962 ORIGINAL AND 1988 ADD‐ON) WERE VACATED AND
DEMOLISHED?
a. Sump?
b. Is there any documentation that Granger’s plating solution contained TCE?
c. Chemical Storage Source Area?
d. Did HP follow hazardous waste practices between 1971‐1977? If so, those records should reveal
how much TCE was trucked away from the site. Have those records been uncovered during the
risk assessment process?
e. Degreaser in the Model Room?
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Potential sources, including the model room, were evaluated to get a clear picture of the Site before
redevelopment. The sampling strategy and results are discussed above. Note that all of the operational
areas of the Site, inclusive of subsurface features such as utility and process water lines within the area,
were evaluated as potential sources. In addition to the extensive sampling program within and outside
of the operational area, an environmental technician was on Site during the demolition activities to
observe, monitor, and collect ambient air and soil samples where indications of potential contamination
existed. Upon advisement by the environmental technician, soil samples were collected at locations
where 1) soil or sludge was identified within a subsurface pipe, 2) total VOCs were measured in soil with
a portable PID, or 3) former process features were previously identified. Sixteen soil samples were
collected beneath the slab and pipes; an additional 11 samples of sludge/soil were collected directly
from exposed, subsurface pipes. TCE was detected at a concentration of 2,200 µg/kg in one sample
(PVC‐PIPE) of residual sludge collected directly from a PVC pipe at the former plating solution sump. TCE
was not detected in any other soil or residual sludge samples that were collected during the demolition
activities.
Observations made during demolition of specific feature locations (e.g., plating solution sump location),
along with historical plans that indicated locations of specific features (see Figure 3 in the SIRA Report)
were incorporated into the sampling strategy and design. The distribution of TCE at and near these
potential source areas is well‐defined.
As discussed in the response to CTRA question 2, additional information regarding potential sources was
explored following Site demolition. Soil samples also were collected from 23 soil borings advanced to
depths between 25 and 35 feet bgs where TCE‐impacted soil vapor was observed. The analytical results
from these efforts are presented in the SIRA Report. TCE concentrations in soil at and in the vicinity of
historical operational features did not identify additional potential sources of TCE to soil vapor.
8. IS THE CURRENT MITIGATION PLAN FOR SOME NEW HOMES ON THE 1601 CALIFORNIA AVE SITE
ADEQUATE?
Yes. The elective mitigation measures based on our redesign for the Site include not building homes
over and near the area with elevated concentrations of TCE in soil vapor, and placing plugs along utility
corridors that traverse or are near the impacted area. Additional measures that will be taken by
Stanford, which include installing vapor barriers beneath homes and placing fill (as part of the
development plan grading requirements), were not required mitigation measures, but provide an
additional level of protection. The placement of clean engineered fill and vapor barriers were,
conservatively, not incorporated in the HHRA.
The proposed 50‐foot buffer for the University Terrace development is appropriate and supported by:
The detailed knowledge of Site lithology relative to the distribution of TCE in soil vapor;
The density of soil vapor sampling locations and analytical results that delineate the extent of
TCE in soil vapor; and
Response to College Terrace Residents’ Association
March 18, 2016
Page 13
The release of TCE into the subsurface occurred at least several decades ago and all of the
potential sources of TCE (e.g., plating solution sump) were removed during Site demolition. Ten
years of soil vapor data at shallow depths have consistently demonstrated that concentrations
of TCE are below residential screening levels ‐ levels designed to be fully protective of human
health and the environment ‐ except at some locations within and near the former operational
area of the Site.
Dr. Paul Johnson, an internationally renowned expert on vapor intrusion, has reviewed, evaluated and
concurred with the Site conceptual model and Stanford’s approach to address vapor intrusion. A copy of
his letter stating his position is attached.
9. WHO IS RESPONSIBLE?
Stanford owns the 1601 California Avenue parcel, but did not operate the former facilities located at this
Site. In its environmental analysis for, and required by, the Mayfield Development Agreement, Stanford
investigated environmental conditions at each of the three parcels – 1451, 1501, and 1601 S. California
Avenue – that comprise the development area. Following its initial evaluations, Stanford has diligently
and responsibly worked to identify and address environmental conditions on the 1601 California Avenue
Site. Information regarding these efforts is included in the SIRA and the Remediation Completion
Report8 and Addendum.9
By entering into a voluntary agreement with the DTSC, Stanford has engaged regulatory oversight to
confirm that Site conditions meet current standards and are safe for future residents. In addition,
Stanford retained Dr. Paul Johnson to perform an independent peer review of the investigation and
analysis performed by Haley & Aldrich. Dr. Johnson concluded that this multiple mitigation approach
protects human health and the environment and goes well beyond industry standard.
Attachments:
Figure 1 Conceptual Site Diagram
Figure 2 Soil Vapor Sample Locations
Figure 3 Cross Section X to X’
Figure 4 Depth to Saturated Soil
Figure 5 Groundwater Analytical Results
Figure 6 Surface Drainage Displayed on 1953 USGS Map
April 23, 2013 Well Decommissioning Request from Stantec Consulting Services to the Water Board,
July 24, 2013 e‐mail from Roger Papler of the Water Board to Paul Paschke of Hewlett Packard
approving request for well decommissioning
Letter from Dr. Paul Johnson to Annette Walton of Stanford dated January 5, 2016
8 Haley & Aldrich, Inc., 2015, Remediation Completion Report – Excavation of Soil Containing Polychlorinated
Biphenyls, 1601 S. California Avenue, Palo Alto, CA, July.
9 Haley & Aldrich, Inc., 2015, Addendum to the July 2015 Remediation Completion Report – Excavation of Soil
Containing Polychlorinated Biphenyls, 1601 S. California Avenue, Palo Alto, California, 1 December.
SOIL VAPOR CONCENTRATIONS
NOT DETECTED OR
BELOW RISK-BASED
RESIDENTIAL TARGET
OPEN SPACE
BUFFER ZONE
10-15 FT.
COMPACTED FILL
CLAYEY SAND CHANNELS
IMPACTED AREA
~
~
RESIDUAL
SUBSURFACE
VAPORS
CLAYEY FLOOD
PLAIN DEPOSITS
SOIL VAPOR CONCENTRATIONS
NOT DETECTED OR
BELOW RISK-BASED
RESIDENTIAL TARGET
~15-20 FT.
UNIVERSITY
TERRACE
FIGURE 1
1451, 1501 AND 1601 S. CALIFORNIA AVENUE
PALO ALTO, CALIFORNIA
SITE CONCEPTUAL DIAGRAM
MARCH 2016
NOT TO SCALE
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1601 S. CALIFORNIA
1501 S. CALIFORNIA 1451 S. CALIFORNIA
RESIDENTIAL
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AMEC-10
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AMEC-7
SG-16
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SG-25
SV-8
SV-6
SV-7
SG-37
SG-18
SG-20
SV-1
SVA-2
SV-2
SV-3
SV-4
SV-5
SVA-14
SVA-12
SVA-15
SVA-10
SVA-9
SVA-7
SVA-6
SVA-4SVA-3
SVA-5
SG-39
SG-42
SG-31
SV-1
SV-10
AMEC-11
SV-9
SV-3
AMEC-12
SV-2
AMEC-2
AMEC-4
AMEC-9
SV-1
SV-3
SV-4
AMEC-3SV-11
SV-6
SV-7SV-8
SV-9
SV-10
SV-12
SV-4
SV-13
SV-7
SV-15
SV-5SV-6
SV-14
SV-8
SV-11
SG-36
SG-30
AMEC-6
AMEC-13
SG-15SG-24SG-21
SG-26
SG-27
SG-29
AMEC-1
AMEC-8
SG-14
SG-38
SG-41
SG-23
SG-28
SG-35
SG-34
SG-40SG-32
SG-33 NOTES
1. THE 1451, 1501, AND 1601 S. CALIFORNIA AV ENUE PARCELSCOM PRISE THE UNIV ERSITY TERRACE PROJECT.
2. DEV ELOPM ENT PLAN SOURCE: W ILLIAM HEZ M ALHALCHARCHITECTS INC., REV ISED SITE PLAN, 9-23-2015.
3. µg/m 3 = M ICROGRAM S PER CUBIC M ETER
4. AERIAL IM AGERY SOURCE: ESRI
1451, 1501 AND 1601 S. CALIFORNIA AV ENUEPALO ALTO, CALIFORNIA
SOIL V APOR SAM PLE LOCATIONS
FIGURE 2SCALE: AS SHOW NFEBRUARY 2016
LEGEND
@@A DENOTES TCE W AS NOT DETECTED IN ANY SAM PLES AT ACONCENTRATION EXCEEDING THE RESIDENTIALSCREENING LEV EL (480 µg/m
3)
@@A DENOTES TCE W AS NOT DETECTED IN ANY SAM PLES AT ACONCENTRATION EXCEEDING AN ESTIM ATED LIFETIM EEXCESS CANCER RISK OF ONE-IN-A-M ILLION (1X10
-6 )
@@A DENOTES TCE W AS DETECTED IN AT LEAST ONE SAM PLE ATA CONCENTRATION EXCEEDING AN ESTIM ATED LIFETIM EEXCESS CANCER RISK OF ONE-IN-A-M ILLION (1X10
-6 )
PROPERTY BOUNDARY
0 100 200
SCALE IN FEET
110
100
90
80
70
60
50
40
30
20
10
110
100
90
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0 50 100
VERTICAL SCALE
SCALE IN FEET
HORIZONTAL SCALE
SV-1
SV-2
SG-20
SG-31
SG-18
SG-17 SV-8
SV-10 AMEC-11 AMEC-12
EB-8
EB-14
EB-3
SG-19
44 W
49 W
43 E 4 W
2 E
6 E
47 E
3 W
2 W
35 E
51 E 19 E
16 W
24 E
SV-1
48 W
SV-2
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GROUND SURFACE ELEVATION
ALONG SECTION LINE (SEE NOTE 4)<8
<8
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<8
<8
<8
<8
<8
<8
<8
<8
<8
<100
<100<100
NF
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NF
NF
NF
NF
NF
SVA-4
0
<100
1451, 1501 AND 1601 S. CALIFORNIA AVENUE
PALO ALTO, CALIFORNIA
CROSS SECTION X TO X'
FIGURE 4SCALE: AS SHOWN
FEBRUARY 2015 32016
SV-10
2 W
<100
GEOLOGIC EXPLANATION BOREHOLE SYMBOLS
FILL
SILTS AND CLAYS (FINE GRAINED
UNITS)
CLAYEY GRAVELS AND SANDS
(COARSE GRAINED UNITS)
BORING DESIGNATION
OFFSET DISTANCE BETWEEN BORING AND
CROSS SECTION LINE (FEET)
STRATUM BOUNDARY
NO FLOW CONDITIONS DURING
SOIL VAPOR SAMPLING
MAXIMUM DETECTED SOIL VAPOR CONCEN-
TRATION OF TRICHLOROETHENE (TCE) IN
MICROGRAMS PER CUBIC METER
TCE NOT DETECTED IN SOIL VAPOR
SAMPLE. CONCENTRATION INDICATED IS
THE TEST DETECTION LIMIT
SG-17
16 W
NF
300
<8
NOTES:
1. REFER TO FIGURE 1- SITE VICINITY WITH DEVELOPMENT
PLAN AND CROSS SECTIONS, FOR PLAN LOCATION, DESIG-
NATION, AND ORIENTATION OF SUBSURFACE SECTIONS
AND AS-DRILLED EXPLORATION LOCATIONS.
2. TEST BORING GROUND SURFACE ELEVATIONS WERE
ESTIMATED AND SHOULD BE CONSIDERED APPROXIMATE.
3. SATURATED SOIL CONDITIONS WERE NOT ENCOUN-
TERED IN ANY OF THE TEST BORINGS SHOWN ON THIS
SECTION.
4. BORINGS SHOWN ABOVE AND BELOW THE GROUND
SURFACE ELEVATION ARE PROJECTED ONTO THE SECTION.
THE TOP OF BORING REPRESENTS THE GROUND SURFACE
ELEVATION AT THE LOCATION WHERE THE BORING WAS
DRILLED.
CROSS SECTION LOCATION PLAN
LIMITS OF 1601 S. CALIFORNIA PROPERTY LIMITS OF 1501 S. CALIFORNIA PROPERTY LIMITS OF 1451 S. CALIFORNIA PROPERTY
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RESIDENTIAL
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SG-16 25
SG-2425
SG-2625
EX4-0835
EX4-02 35
EX4-0435
EX4-0535
EX4-07 35
EX4-0935EX4-06 35
EX4-10 35EX4-0135
SG-3335
SG-2325 SG-3125
SG-3525.5
SG-3625.5
SG-3435
SG-4025.5SG-3235
SG-3035
SBA-640
SG-1925
EB-625
AMEC-625.5
AMEC-725.5
AMEC-1325.5
SG-1525
SG-1725
SG-2525
EB-225
SG-2125 SG-2725
SG-2925
AMEC-125.5
AMEC-825.5SBA-837
SG-1425
SG-3740
EX4-0335
SG-1825
SG-2025
SBA-3755
SBA-3549
SBA-3366
EB-125
EB-325
EB-525
EB-425SG-3825 SG-4125.5
SG-3925.5
SG-4225.5
SG-2825
EB-1425
AMEC-1225.5 EB-825
EB-1225
AMEC-225.5
AMEC-425.5
AMEC-925.5
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SBA-9 : 29.5 (NOTE 5)
SBA-11 : 37.5 (NOTE 4)
GW-2 : 31.4
GW-1 : 39.8
SB-9 : 34.5SB-10 : NOTE 7
SB-11 : 35.7 SB-12 : NOTE 7
SB-13 : NOTE 7
GW-20 : NOTE 6
EB-9 : 31.9 (NOTE 8)
EB-15 : 26 (NOTE 8)
EB-16 : 24.8 (NOTE 8)
NOTES
1. THE 1451, 1501, AND 1601 S. CALIFORNIA AV ENUE PARCELS COM PRISE THEUNIV ERSITY TERRACE PROJECT.
2. DEV ELOPM ENT PLAN SOURCE: W ILLIAM HEZ M ALHALCH ARCHITECTS INC.,REV ISED SITE PLAN, 9-23-2015.
3. DATA BASED ON BORING LOGS AND DOCUM ENTED INFORM ATION ININV ESTIGATION REPORTS FROM GEOM ATRIX CONSULTANTS, AM EC AND HALEYAND ALDRICH.
4. AT SBA-11, SATURATED SOIL W AS ENCOUNTERED, HOW EV ER SOILS W ERE NOTSUFFICIENTLY TRANSM ISSIV E TO ALLOW FOR COLLECTION OF A W ATER SAM PLE.
5. AT SBA-9, SATURATED AND COARSER GRAINED SOIL W AS OBSERV ED IN A LENSEXTENDING FROM APPROXIM ATELY 29.5 TO 30 FEET BGS. NO OTHER SATURATEDSOIL W AS OBSERV ED TO THE TOTAL DEPTH OF THE BOREHOLE.
6. AT GW -20, A GRAB GROUNDW ATER SAM PLE W AS OBTAINED FROM 50 TO 55FEET BGS. DATA FOR DEPTH TO FIRST SATURATED SOIL W AS NOT AV AILABLE.
7. AT SB-10, SB-12, AND SB-13, GRAB GROUNDW ATER SAM PLES W ERE OBTAINEDFROM W ELL SCREENS THAT EXTENDED FROM 28 TO 43, 16 TO 45, AND 27 TO 45FEET BGS, RESPECTIV ELY. DATA FOR DEPTHS TO FIRST SATURATED SOIL W ERENOT AV AILABLE.
8. THE PRESENCE OF GROUNDW ATER W AS DOCUM ENTED IN BORINGS EB-9, EB-15AND EB-16, W HICH W ERE DRILLED AS PART OF THE GEOTECHNICALINV ESTIGATION, AT THE DEPTHS SHOW N.
9. AERIAL IM AGERY SOURCE: ESRI
1451, 1501 AND 1601 S. CALIFORNIA AV ENUEPALO ALTO, CALIFORNIA
DEPTH TO SATURATED SOIL
FIGURE 4SCALE: AS SHOW NM ARCH 2016
LEGEND
PROPERTY BOUNDARY
&(
LOCATION OF BORING AT W HICH SATURATED SOIL W ASENCOUNTERED OR THE PRESENCE OF GROUNDW ATERW AS DOCUM ENTED (DEPTH SHOW N INDICATES DEPTHBELOW GROUND SURFACE TO SATURATED SOIL ORGROUNDW ATER)
LOCATION OF BORING ADV ANCED TO DEPTH INTERV ALNOTED BELOW ; SATURATED SOIL NOT ENCOUNTERED
@A UP TO 25.4 FEET BELOW GROUND SURFACE (BGS)
@A 25.5 - 35.4 FEET BGS
@A 35.5 - 45 FEET BGS
@A M ORE THAN 45 FEET BGS
0 100 200
SCALE IN FEET
25.0 DEPTH INDICATED IS TOTAL BOREHOLE DEPTH
36.7
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RESIDEN TIAL
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SBA-9SCREEN INTERVAL: 26-46TCE CONCENTRATION: 45
GW-20SCREEN INTERVAL: 52.5-55.0TCE CONCENTRATION: 13
SB-9SCREEN INTERVAL: 31-46TCE CONCENTRATION: <0.50
GW-1SCREEN INTERVAL: 36-41TCE CONCENTRATION: <0.50
SB-12SCREEN INTERVAL: 16-45TCE CONCENTRATION: <0.50
SB-11SCREEN INTERVAL: 31-46TCE CONCENTRATION: <0.50
SB-10SCREEN INTERVAL: 28-43TCE CONCENTRATION: <0.50
GW-2SCREEN INTERVAL: 27.5-32.5TCE CONCENTRATION: <0.50
SB-13SCREEN INTERVAL: 27-45TCE CONCENTRATION: <0.50
SG-23
SG-35
SG-36
SG-34
SG-40
SG-32
SG-30
SBA-6
SG-19
EB-6
AMEC-6
AMEC-7
AMEC-13
SG-15SG-16
SG-17
SG-24 SG-25
EB-2
SG-21
SG-26
SG-27
SG-29
AMEC-1
AMEC-8
SBA-8
SG-14
SG-37
EX4-08
EX4-03
EX4-02
EX4-04
EX4-05
EX4-07
EX4-09EX4-06
EX4-10
SG-18
SG-20
SBA-37
SBA-35
SBA-33
EX4-01
SG-33
EB-1
EB-3
EB-5
EB-4
SBA-11
SG-38
SG-41
SG-39
SG-42
SG-28
SG-31
EB-14
AMEC-12 EB-8
EB-9
EB-12
EB-15
EB-16
AMEC-2
AMEC-4
AMEC-9
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NOTES
1. THE 1451, 1501, AN D 1601 S. CALIFORN IA AV EN UE PARCELS COMPRISE THEUN IV ERSITY TERRACE PROJECT.
2. DEV ELOPMEN T PLAN SOURCE: W ILLIAM HEZ MALHALCH ARCHITECTS IN C.,REV ISED SITE PLAN , 9-23-2015.
3. DATA BASED ON BORIN G LOGS AN D DOCUMEN TED IN FORMATION ININ V ESTIGATION REPORTS FROM GEOMATRIX CON SULTAN TS, AMEC AN D HALEYAN D ALDRICH.
4. AT SBA-9, SATURATED AN D COARSER GRAIN ED SOIL W AS OBSERV ED IN A LEN SEXTEN DIN G FROM APPROXIMATELY 29.5 TO 30 FEET BGS. N O OTHER SATURATEDSOIL W AS OBSERV ED TO THE TOTAL DEPTH OF THE BOREHOLE.
5. AT GW -20, A GRAB GROUN DW ATER SAMPLE W AS OBTAIN ED FROM 50 TO 55FEET BGS. DATA FOR DEPTH TO FIRST SATURATED SOIL W AS N OT AV AILABLE.
6. AT SB-10, SB-12, AN D SB-13, GRAB GROUN DW ATER SAMPLES W ERE OBTAIN EDFROM W ELL SCREEN S THAT EXTEN DED FROM 28 TO 43, 16 TO 45, AN D 27 TO 45FEET BGS, RESPECTIV ELY. DATA FOR DEPTHS TO FIRST SATURATED SOIL W EREN OT AV AILABLE.
7. THE RESIDEN TIAL GROUN DW ATER EN V IRON MEN TAL SCREEN IN G LEV EL (ESL)FOR THE EV ALUATION OF V APOR IN TRUSION CON CERN S (FIN E-COARSE SOILTYPE) FOR TCE IS 170 µg/L (REGION AL W ATER QUALITY CON TROL BOARD, SANFRAN CISCO BAY REGION , 2016).
8. SCREEN IN TERV AL SHOW N IN FEET BGS
9. TCE CON CEN TRATION SHOW N IN MICROGRAMS PER LITER (µg/L)
10. AERIAL IMAGERY SOURCE: ESRI
1451, 1501 AN D 1601 S. CALIFORN IA AV EN UEPALO ALTO, CALIFORN IA
GROUN DW ATER AN ALYTICAL RESULTS
FIGURE 5SCALE: AS SHOW NMARCH 2016
LEGEND
PROPERTY BOUN DARY
&(GROUN DW ATER SAMPLIN G LOCATION
@A
BORIN G DRILLED TO DEPTH OF AT LEAST 25 FEET BELOWGROUN D SURFACE (BGS) W ITH N O GROUN DW ATEREN COUN TERED
0 100 200
SCALE IN FEET
NOTES
1. ALL LOCATIONS AND DIMENSIONS AR E APPR OXIMATE
2. TOPO MAP SOUR CE: 1953 NW/4 PALO ALTO 15' QUADANGLE
LEGEND
PR OPER TY BOUNDAR Y
0 1,000 2,000
SCALE IN FEET
1451, 1501 AND 1601 S. CALIFOR NIA AVENUEPALO ALTO, CALIFOR NIA
SUR FACE DR AINAGE DISPLAY ED ON 1953 USGS TOPOGR APHIC MAP
FIGUR E 6
SCALE: AS SHOWNMAR CH 2016
January 5, 2016
Annette Walton
Director - Environmental Management Real Estate Operations
3160 Porter Drive, Suite 200
Palo Alto, California 94304
Dear Annette –
As requested, this letter briefly summarizes key points of my review and our discussions related
to the health risk assessment and development plans at Stanford’s University Terrace Project,
which involves the redevelopment of three former industrial-use properties to a neighborhood
consisting of Stanford faculty housing and open park space.
No further action letters were issued in 2013 by the California State Department of Toxic
Substances Control (DTSC) for two of the properties (1451 and 1501 California Avenue, Palo
Alto, CA). Based on environmental reports provided to DTSC, they concluded that neither site
posed a significant threat to human health or the environment under residential land use.
Thus, my involvement has been focused on the third property at 1601 California Avenue, for
which supplemental investigation was conducted to thoroughly assess the potential for
significant health risks from post-remediation TCE residuals at depth in the subsurface. That
assessment is summarized in the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California, prepared by Haley & Aldrich, Inc.
Key points from my review and our discussions include the following:
Relative to the initial draft, conclusions in the final version of the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California were the same,
but strengthened by the thorough evaluation of the site conceptual model conducted by Murray
Einarson and the expanded range of site-specific inputs that were incorporated by Haley &
Aldrich, Inc. in their calculations. These additions increased confidence in the conclusions
stemming from vapor intrusion pathway analysis because the selection of defensible site-specific inputs and considering a range of possible scenarios is critical to generating confidence in the
results. It was also critical, because subsurface geology is a key controlling factor for vapor
migration at this site.
There is confidence in the use of the site data for the risk analysis because the historical information, subsurface geology conceptual model, and chemical distribution appear to be self-
consistent.
The site plan for the University Terrace Project reflects the analysis and conclusions contained in
the Supplemental Investigation and Risk Assessment Report, 1601 S. California Avenue, Palo Alto, California. Future residences are placed in areas with projected negligible risks and the
relatively isolated area of possible concern is open park space in the plan.
The risk assessment report concludes that the future residences will not be exposed to significant
health risks under any building construction design and that pre-emptive building-specific
mitigation measures are not needed (e.g., sub-slab depressurization systems). The sub-foundation
vapor barrier liners being incorporated in the residential construction, therefore, are not necessary, but will add an additional level of protectiveness from vapor intrusion and potential
comfort for the occupants.
Development plans also address the potential for vapor intrusion via alternative pathways, as we
discussed recent studies where vapor intrusion was observed in buildings off-set from subsurface vapor sources as a result of transport along utilities and utility conduits. The potential for this is
being eliminated in the planned development design by ensuring that utilities are not run through
the residual vapor source at the site and by having vapor plugs/seals installed along the utilities.
Should you have questions or require clarification of this summary, please feel free to contact me.
Sincerely,
Paul C. Johnson, Ph.D.
Stantec Consulting Services Inc.
15575 Los Gatos Boulevard, Building C
Los Gatos CA 95032
Tel: (408) 356-6124
Fax: (408) 356-6138
April 23, 2013
Mr. Roger Papler
California Regional Water Quality Control Board
San Francisco Bay Region
1515 Clay Street, Suite 1500
Oakland, CA 94612
RE: Request to Decommission Monitoring Wells MW-135 through MW-138, MW-163 and
MW-164 for the Groundwater Monitoring Program at 1501 Page Mill Road, Palo Alto,
California
Dear Mr. Papler:
On behalf of Hewlett Packard Company (HP), Stantec Consulting Services Inc. (Stantec) presents this
request to decommission groundwater monitoring wells MW-135 through MW-138, MW-163, and MW-164
located downgradient (i.e., off site) of HP’s 1501 Page Mill Road, Palo Alto, California site facility (Site). Wells
MW-135 through MW-138 are located at 1450/1454 Page Mill Road, and wells MW-163 and MW-164 are
located at 1601 California Avenue in Palo Alto, California (Figure 1). Three of the wells (MW-136, MW-138,
and MW-163) are screened in the Gamma 1 Zone and the remaining three wells (MW-135, MW-137, and
MW-164) are screened in the Gamma 2 Zone. Decommissioning of the wells is required to facilitate
redevelopment construction activities on those properties by the property owner, Stanford. Stanford intends to
redevelop the properties, including the locations where the wells are located, as single family residences in
late fall or early winter 2013 and has requested that HP remove the wells from the properties. Wells MW-135,
MW-136, and MW-164 are sampled annually as part of the current groundwater monitoring program for the
Site. Wells MW-137, MW-138, and MW-163 are not used for groundwater sampling, but have been used for
the annual measurement of groundwater level levels in the vicinity of the Site. The six monitoring wells are
not considered essential to the monitoring program and decommissioning of the wells would not adversely
affect the monitoring objectives of the current monitoring program. Historical analytical data for the wells are
presented in Table 1 and a brief discussion of each well follows.
Gamma 1 Zone Wells
Well MW-136. This well is located on the 1450/1454 Page Mill Road property. Trichloroethene (TCE) is the
principal volatile organic compound (VOC) detected in the groundwater at well MW-136. TCE concentrations
in the groundwater from this well are stable and have remained below the Federal and State Maximum
Contaminant Levels (MCLs; 5 µg/L) since April 1996 (Table 1).
Well MW-138. This well is located on the 1450/1454 Page Mill Road property. The well was sampled four
times between July 1993 and May 1994. No VOCs were detected in the groundwater from this well, and the
well was subsequently removed from the list of wells sampled for the groundwater monitoring program in
1994. The well is currently only used for the measurement of groundwater levels on an annual basis.
Mr. Roger Papler
April 23, 2013
Page 2 of 2
Well MW-163. This well is located on the 1601 California Avenue. The well was sampled 14 times between
August 1993 and July 1997. No volatile organic compounds (VOCs) were detected in the groundwater from
this well, and the well was removed from the list of wells sampled for the groundwater monitoring program in
1997. The well is currently only used for the measurement of groundwater levels on an annual basis.
Gamma 2 Zone Wells
Well MW-135. This well is located on the 1450/1454 Page Mill Road property. Historically, TCE has been the
principal VOC detected in the groundwater at this well. TCE concentrations in the groundwater have been
relatively stable ranging from 6 to 85 µg/L for the last 10 monitoring events (August 2003 through August
2012).
Well MW-137. This well is located on the 1450/1454 Page Mill Road property. The well was sampled nine
times between July 1993 and April 1997. No volatile organic compounds (VOCs) were detected in the
groundwater from this well, and the well was subsequently removed from the list of wells sampled for the
groundwater monitoring program in 1997. The well is currently only used for the measurement of
groundwater levels on an annual basis.
Well MW-164. This well is located on the 1601 California Avenue property downgradient of 1501 Page Mill
Road site. The well has been sampled as part of the groundwater monitoring program since 1993. No volatile
organic compounds (VOCs) have been detected in the groundwater from this well.
In summary, the six off-site monitoring wells are not considered essential to the monitoring program and
decommissioning of the wells would not adversely affect HP’s ability to monitor VOC-impacted groundwater
plume.
Upon your approval to decommission the wells, the wells will be destroyed to facilitate the proposed
redevelopment of the properties at which they are located. The wells will be destroyed consistent with well
destruction guidelines of the Santa Clara Valley Water District.
Please contact Mr. Paul Paschke of HP at (970) 898-0573 if you have questions regarding this request.
Sincerely,
STANTEC CONSULTING SERVICES INC.
Howard H. Koltermann, PG, CEG, CHG Mark Becker
Senior Hydrogeologist Senior Scientist
Tel: (408) 356-6124 Tel: (408) 356-6124
Cell: (408) 210-6573 Cell: (831) 246-0711
howard.koltermann@stantec.com mark.becker@stantec.com
Attachments: Figure 1 – Site Plan
Table 1 – Historical Groundwater Analytical Results for Wells MW-135 through MW-138,
MW-163, and MW-164
cc: Paul Paschke, Hewlett-Packard Company
Annette Walton, Stanford
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Figure No.
Title Site Plan
1
Hewlett-Packard Company
1501 Page Mill Road
Palo Alto, Santa Clara County, California
October 2012185702501
Notes
Legend
1.
2.
Coordinate System:
NAD 1983 StatePlane California III FIPS 0403 Feet
Aerial imagery provided by Digital Globe, 2010.
0 150 300ft
1 in = 300 ft
South Side Area Alluvium Zone and Santa Clara Zone 1
&A Monitoring or Piezometer Well Location
%!8 Inactive Extraction Well Location
S-Zone
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%!8 Inactive Extraction Well Location
Gamma - A Zone
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Gamma - 2 Zone
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%!Active Extraction Well
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Gamma - 3 Zone
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%!8 Inactive Extraction Well Location
Gamma - 4 Zone
&A Monitoring or Piezometer Well Location
%!8 Inactive Extraction Well Location
\\cd1004-f06\Work_group\01221\active\122140012_data_base_mgmt\Databases\185702367\Drawing\MXD\1501\2012-09-19\185702367_1501_Fig01_SitePlan.mxdRevised: 2012-10-01 By: sstroszkali
Table 1
Historical Groundwater Analytical Results for Wells MW-135 through MW-138, MW-163 and MW-164
Hewlett-Packard Company 1501 Page Mill Road Site
Palo Alto, California
Well ID Sample Flow Sample TCE PCE 1,1,1-TCA 1,1-DCA 1,1-DCE cis-1,2-DCE Benzene Toluene Ethylbenzene Xylenes, Total Other
Type Zone Date Constituents
MW-135 Gamma-2 Zone 1/21/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-135 Gamma-2 Zone 5/12/1993 14 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.98;
MW-135 Gamma-2 Zone 6/18/1993 19 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/6/1993 27 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- --- CHLFM = 0.84;
MW-135 Gamma-2 Zone 9/23/1994 20 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.88;
MW-135 Gamma-2 Zone 12/2/1994 <0.5 <0.5 <0.5 <0.5 33 <0.5 --- --- --- --- CHLFM = 1.2;
MW-135 Gamma-2 Zone 1/13/1995 18 <0.5 <0.5 <0.5 0.54 1.6 ------ --- --- CHLFM = 1.1;
MW-135 Gamma-2 Zone 4/20/1995 37 <0.5 <0.5 <0.5 <0.5 2.2 ------ --- --- CHLFM = 1.1;
MW-135 Dup Gamma-2 Zone 4/20/1995 43 <0.5 <0.5 <0.5 <0.5 2.2 --- --- --- --- CHLFM = 1.1;
MW-135 Gamma-2 Zone 7/7/1995 30 <0.5 <0.5 <0.5 <0.5 0.86 ------ --- --- CHLFM = 1;
MW-135 Dup Gamma-2 Zone 7/7/1995 31 <0.5 <0.5 <0.5 <0.5 1.1 --- --- --- --- CHLFM = 1.2;
MW-135 Gamma-2 Zone 10/20/1995 36 <0.5 <0.5 <0.5 <0.5 0.67 --- --- --- --- CHLFM = 0.77;
MW-135 Gamma-2 Zone 1/5/1996 24 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- ---
MW-135 Gamma-2 Zone 4/10/1996 19 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 7/9/1996 16 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- ---
MW-135 Gamma-2 Zone 10/9/1996 20 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 1/9/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 4/14/1997 17 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 7/15/1997 15 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 10/9/1997 17 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 1/8/1998 16 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- ---
MW-135 Dup Gamma-2 Zone 1/8/1998 16 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 4/10/1998 20 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 7/9/1998 12 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- ---
MW-135 Gamma-2 Zone 10/8/1998 14 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 1/5/1999 13 <0.5 <0.5 <0.5 <0.5 <0.5 ------ --- ---
MW-135 Dup Gamma-2 Zone 1/5/1999 14 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 4/12/1999 13 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 7/14/1999 15 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 10/8/1999 14 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 1/13/2000 14 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/21/2000 13 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/27/2001 17 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/21/2002 22 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Dup Gamma-2 Zone 8/21/2002 24 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/19/2003 43 <0.5 <0.5 <0.5 <0.5 3.2 ------ --- ---
MW-135 Gamma-2 Zone 10/5/2004 68 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-135 Gamma-2 Zone 8/31/2005 58 <1 <1 <1 <1 <1 --- --- --- ---
MW-135 Gamma-2 Zone 8/31/2006 5.9 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 6.3;
MW-135 Gamma-2 Zone 8/15/2007 27 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 5.4;
MW-135 Gamma-2 Zone 8/20/2008 71 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 1.5;
MW-135 Dup Gamma-2 Zone 8/20/2008 63 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 1.3;
MW-135 Gamma-2 Zone 8/3/2009 73 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-135 Gamma-2 Zone 8/3/2010 74 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-135 Gamma-2 Zone 8/1/2011 85 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-135 Gamma-2 Zone 8/13/2012 75 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
E:\HP\well_Destructions\20130411 - Table 1 - MW-135-138, MW-163,164.xlsx
185702205.200.044
Page 1 of 4
Table 1
Historical Groundwater Analytical Results for Wells MW-135 through MW-138, MW-163 and MW-164
Hewlett-Packard Company 1501 Page Mill Road Site
Palo Alto, California
Well ID Sample Flow Sample TCE PCE 1,1,1-TCA 1,1-DCA 1,1-DCE cis-1,2-DCE Benzene Toluene Ethylbenzene Xylenes, Total Other
Type Zone Date Constituents
MW-136 Gamma-1 Zone 2/21/1993 14 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-136 Gamma-1 Zone 3/9/1993 46 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-136 Gamma-1 Zone 5/12/1993 40 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.6;
MW-136 Gamma-1 Zone 12/3/1994 18 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 4/19/1995 30 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 10/20/1995 11 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 4/13/1996 1.7 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 10/18/1996 0.57 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 4/15/1997 0.7 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 10/9/1997 0.77 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 1/8/1998 0.95 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 4/7/1998 0.53 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 7/7/1998 1 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 10/9/1998 2.9 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 1/7/1999 3.0 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- MC = 6.2;
MW-136 Gamma-1 Zone 4/7/1999 4 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 7/13/1999 3.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 10/8/1999 2.2 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 1/13/2000 3.7 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/28/2000 0.75 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.69;
MW-136 Gamma-1 Zone 8/28/2001 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/9/2002 2 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.55;
MW-136 Gamma-1 Zone 8/15/2003 2.7 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.72;
MW-136 Gamma-1 Zone 10/5/2004 3.9 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/16/2005 3.4 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- --- CHLFM = 0.58;
MW-136 Gamma-1 Zone 8/31/2006 4.3 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/15/2007 4.2 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/20/2008 4.1 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-136 Gamma-1 Zone 8/3/2009 3.9 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-136 Gamma-1 Zone 8/2/2010 4.0 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-136 Gamma-1 Zone 8/1/2011 4.3 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-136 Gamma-1 Zone 8/13/2012 4.1 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-137 Gamma-2 Zone 7/20/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Acetone = 36; MEK = 240;
MW-137 Gamma-2 Zone 8/18/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Acetone = 22; MC = 5.5; MEK = 440;
MW-137 Dup Gamma-2 Zone 8/18/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 MC = 5.7;
MW-137 Gamma-2 Zone 11/19/1993 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 3/2/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 11/20/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 4/14/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 10/13/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 4/12/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-137 Gamma-2 Zone 4/21/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-138 Gamma-1 Zone 7/15/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-138 Gamma-1 Zone 11/23/1993 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-138 Gamma-1 Zone 2/25/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-138 Gamma-1 Zone 5/13/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
E:\HP\well_Destructions\20130411 - Table 1 - MW-135-138, MW-163,164.xlsx
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Table 1
Historical Groundwater Analytical Results for Wells MW-135 through MW-138, MW-163 and MW-164
Hewlett-Packard Company 1501 Page Mill Road Site
Palo Alto, California
Well ID Sample Flow Sample TCE PCE 1,1,1-TCA 1,1-DCA 1,1-DCE cis-1,2-DCE Benzene Toluene Ethylbenzene Xylenes, Total Other
Type Zone Date Constituents
MW-163 Gamma-1 Zone 8/27/1993 <5.00 <5.00 <5.00 <5.00 <5.00 --- 54 50.8 <5.00 <5.00
MW-163 Gamma-1 Zone 8/25/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 11/23/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 1/19/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 4/19/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 7/13/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 10/20/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 1/10/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 4/10/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 7/10/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 10/17/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 1/8/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 4/11/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-163 Gamma-1 Zone 7/16/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 9/17/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-164 Dup Gamma-2 Zone 9/17/1993 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5
MW-164 Gamma-2 Zone 8/24/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 11/23/1994 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 1/18/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 4/18/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 7/12/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/14/1995 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 1/11/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 4/12/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 7/10/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/17/1996 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 1/8/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 4/14/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 7/16/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/9/1997 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/13/1998 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/7/1999 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/28/2000 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 9/6/2001 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
MW-164 Gamma-2 Zone 8/9/2002 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Dup Gamma-2 Zone 8/9/2002 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/14/2003 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 10/5/2004 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/16/2005 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/30/2006 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/15/2007 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/20/2008 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 --- --- --- ---
MW-164 Gamma-2 Zone 8/3/2009 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-164 Gamma-2 Zone 8/2/2010 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-164 Dup Gamma-2 Zone 8/2/2010 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-164 Gamma-2 Zone 8/1/2011 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
MW-164 Gamma-2 Zone 8/13/2012 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 --- --- --- ---
E:\HP\well_Destructions\20130411 - Table 1 - MW-135-138, MW-163,164.xlsx
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Page 3 of 4
Table 1
Historical Groundwater Analytical Results for Wells MW-135 through MW-138, MW-163 and MW-164
Hewlett-Packard Company 1501 Page Mill Road Site
Palo Alto, California
Well ID Sample Flow Sample TCE PCE 1,1,1-TCA 1,1-DCA 1,1-DCE cis-1,2-DCE Benzene Toluene Ethylbenzene Xylenes, Total Other
Type Zone Date Constituents
Abbreviations:
--- = Not analyzed
All results reported in ug/L, except for lead.
TCE = Trichloroethene
1,1,1-TCA = 1,1,1-trichloroethene
1,1-DCA = 1,1 dichloroethane
1,1-DCE = 1,1-dichloroethene
cis-1,2-DCE = cis-1,2-dichloroethene
PCE = tetrachloroethene (perchloroethene)
CHLFM = Chloroform
MC = Methylene Chloride
MEK = Methyl Ethyl Ketone
E:\HP\well_Destructions\20130411 - Table 1 - MW-135-138, MW-163,164.xlsx
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Page 4 of 4
From:Papler, Roger@Waterboards
To:Paschke, Paul E (paul.paschke@hp.com)
Cc:Walton, Annette; Mark Becker (Mark.Becker@stantec.com); howard.koltermann@stantec.com
Subject:HP/PA - 1501 PMR: Comments - Well Decom Request
Date:Wednesday, July 24, 2013 6:41:16 PM
Hello Paul: Thank you for submitting the 23April13 Request to Decommission Monitoring Wells MW-135 throughMW-138, MW-163 and MW-164 (Request). Regional Water Board staff reviewed the Request and we have the following comments. It is ourunderstanding that the off-property wells were installed during the remedial investigation phase of thesubject site. Since that time, the groundwater monitoring data indicates that the groundwater plumesassociated with the site are within the subject site. Based on well screening data provided by yourconsultant, MW-138 and MW-137 are screened in the Gamma 1 and 2 Zone wells and too deep to beused as sentry wells upgradient of 1050 Mill Road. Based on the above, the Request is acceptable. Please let us know if you need a Regional Water Board letter. Respectfully, Roger W. Papler P.G.Engineering GeologistSan Francisco Bay Regional Water Quality Control Board1515 Clay Street, Suite 1400Oakland, CA 94612
Attachment D
Hardcopies were provided to the City Council members and Libraries only
This attachment can be reviewed at:
http://www.cityofpaloalto.org/news/displaynews.asp?NewsID=2436&TargetID=319
December 16, 2015
Jodie Gerhardt, AICP
Current Planning Manager
City of Palo Alto 250 Hamilton Avenue, 5th Floor
Palo Alto, CA 94301
Re: Submittal of Amended Map for Tract No. 10281, Mayfield California Avenue Residential
Dear Jodie:
As we have discussed with you and with Michel Jeremias, Stanford University requests an
amendment to the Final Map for Tract No. 10281, Mayfield California Avenue Residential. Our
proposed amended map is enclosed for City review. This amendment affects only portions of the
former 1601 California Avenue site; it does not affect the former 1451 and 1501 California Avenue sites.
The reason we request this amendment is as follows. Characterization sampling (soil, soil gas
and groundwater) conducted pursuant to the Mayfield Development Agreement Mitigation
Monitoring and Reporting Plan (MMRP) revealed an area of isolated elevated TCE
concentrations in the form of soil gas under the former footprint of 1601 California Avenue building, where a sump is believed to have been a source contributing to this release. This area
was not accessible for TCE testing until after the building was demolished. The isolated TCE in
soil gas remains at depth and has not migrated 50 feet beyond this localized area; Also within
this isolated area, TCE was found in one perched groundwater sample at a concentration that
would not contribute to vapor intrusion; concentrations in groundwater have not migrated from the property. As required by the MMRP, Stanford reported the test results to DTSC. Among
other measures, Stanford proposed to DTSC that seven homes originally planned to be located
on or near the elevated TCE readings be moved at least 50 feet away from the isolated area
thereby eliminating any potential risk of vapor intrusion to future occupants. The isolated area
would be used for open space and streets. DTSC agrees that there will not be a risk to future site users with the proposed redevelopment design.
This design redistributes 29 residences at the former 1601 California Avenue so that the required
180 homes are still provided; creates a jog in the new Amherst Street to accommodate the
redistributed homes; reduces the total square footage of home sites and homes in the affected
area; and increases common area open space.
Attachment E
Jodie Gerhardt
December 16, 2015
Page 2
After carefully reviewing the evidence, including this design, DTSC has agreed that “that there will not be a significant risk to future site users with the proposed redevelopment design.”
Accordingly, we now seek an amendment to the Final Map for Tract No. 10281 to reflect these
changes in the site plan. We request that the City Council consider and approve Stanford’s
request expeditiously so that project construction, which is already well under way on the former
1451 and 1501 California Avenue portions of the project site, can be completed as promptly as possible.
Section 21.16.280 of the Palo Alto Municipal Code authorizes map amendments. With respect
to final maps (as opposed to parcel maps), the ordinance provides:
In addition to the amendments authorized by Government Code
Section 66469, after a final map … is filed in the office of the county recorder, the recorded map may be modified by a certificate of correction or an amending map if (i) there are changes in
circumstances which make any or all of the conditions of such a
map no longer appropriate or necessary, (ii) that the modifications
do not impose any additional burden on the present fee owner of the property, (iii) the modifications do not alter any right, title, or interest in the real property reflected on the recorded map, and (iv)
the map as modified conforms to the provisions of the Subdivision
Map Act and Chapter 21. 16 of this title. The decision to approve
or deny a modification shall be made by the city council for final maps…. Prior to approval of any modification, notice shall be given as provided in Section 21.12.090. The hearing shall be
confined to consideration of and action on the proposed
modification.
Stanford’s request meets the four requirements of section 21.16.280. First, there are changes in circumstances (elevated TCE readings under seven home sites) that make certain final map conditions (the locations of those homes) no longer appropriate or necessary. Second, the
modifications do not impose any additional burden on Stanford, which is the fee owner of the
property. Third, the modifications do not alter any right, title, or interest in the real property
reflected on the recorded map. Fourth, the map as modified conforms to the provisions of the Subdivision Map Act and PAMC Chapter 21.16.
As you know, because this project is subject to the Mayfield Development Agreement and
Stanford elected to apply AS2 zoning to it as permitted by that agreement, the project must
continue to comply with AS2 Alternative Development Standards.
Jodie Gerhardt
December 16, 2015
Page 3
We also note that the proposed final map amendment would not result in a substantial increase in the severity of the environmental impacts identified in the Mayfield Development Agreement EIR. During construction, impacts would be the same as under the approved final map. All
Mayfield Development Agreement EIR mitigation measures would continue to apply. No
additional protected trees would be removed or relocated. Once the project is complete, impacts
would be the same, or slightly less than, the less-than-significant impacts identified with the approved final map. The reason for this is that although the amended map still provides for a total of 180 dwelling units at the project (as required under the Mayfield Development
Agreement), as noted above, some units will be reduced in square footage and bedroom count, as
the house redistribution will be accomplished in part by switching some of the larger house plans
to some of the smaller plans, and, in some cases, combining these smaller plans into duplexes. As a result, the project’s total occupancy and, therefore, its total vehicle trips, will likely be reduced compared to buildout under the January 2015 final map.
We look forward to working with the City to process this application as expeditiously as possible
and welcome any comments or questions you may have.
Sincerely yours,
Chris Wuthmann
Enclosures
- Setback Compliance Site Plan
- Height Restriction Compliance Site Plan - DTSC Approval email
ATTACHMENT F
Attachment G
Hardcopies were provided to the City Council members and Libraries only
Project plans can be reviewed at:
http://www.cityofpaloalto.org/news/displaynews.asp?NewsID=3437