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TA. - Page 77
<br /> LSA ASSOCIATES, INC. ROCKETSHIP REDWOOD CITY ELEMENTARY SCHOOL PROJECT
<br /> SEPTEMBER 2016 INITIAL STUDY/MITIGATED NEGATIVE DECLARATION
<br /> Based on the information reviewed,the shallow groundwater in the vicinity of the project site appears
<br /> to be impacted with volatile organic compounds(VOCs)including tetrachloroethene (PCE),
<br /> trichloroethene (TCE),and cis-1,2-dichloroethene (cis-1,2-DCE).Historically,PCE and TCE were
<br /> commonly used as cleaning solvents at industrial facilities. As PCE naturally degrades in the
<br /> environment,it can form TCE and TCE can degrade to form cis-1,2-DCE. The groundwater
<br /> monitoring performed at 2201 Bay Road indicates that shallow groundwater's piezometric surface59
<br /> historically ranges from 6.5 to 9.1 feet below ground surface and the apparent groundwater flow
<br /> direction is generally to the northwest toward the San Francisco Bay,away from the project site.60
<br /> Based on the results of groundwater monitoring performed at 2201 Bay Road in 2010,the highest
<br /> concentration of PCE in groundwater was reported to be 36 micrograms per liter(µg/L),the highest
<br /> TCE was 3.7 gg/L,and the highest cis-1,2-DCE was 1.7 gg/L. The concentration of all three VOCs
<br /> were higher along the downgradient(northwest) side of that property;however,PCE,TCE,and cis-
<br /> 1,2-DCE were also reported in a groundwater monitoring well upgradient from 2201 Bay Road,
<br /> suggesting other possible sources contributing to the groundwater impact. Groundwater monitoring
<br /> reports for the 2201 Bay Road site state that"regional chlorinated solvent plume may be contributing
<br /> to the on-site concentrations.,,61 Because the project site is located upgradient from the 2201 Bay Road
<br /> site,contamination of soil at the project site from past land use at 2201 Bay Road is unlikely;however,
<br /> if the VOC concentrations in groundwater reported at 2201 Bay Road are the result of an upgradient
<br /> source,VOCs may also be present in the groundwater at the project site.
<br /> The Phase I ESA identified the following Recognized Environmental Condition(REC),62 as defined
<br /> by ASTM E1527-05,71 on the project site due to former site uses: "There is a potential that hazardous
<br /> material used by past Site occupants or nearby commercial businesses could have impacted the Site.
<br /> Additionally,a reported regional groundwater solvent plume may extend beneath the site. Sampling
<br /> of soil, soil vapor,and groundwater is recommended to better evaluate site conditions prior to future
<br /> use as a school."The investigation conducted by Cornerstone Earth Group in 2014 evaluated soil, soil
<br /> vapor,and groundwater quality at the project site. The investigation consisted of the collection and
<br /> analyses of soil,groundwater,and subsurface and sub-slab vapor samples (i.e.,vapor samples from
<br /> beneath existing building foundation slabs,where vapors may collect).
<br /> Six soil borings were made at the project site to depths of 15 feet below ground surface (bgs)and
<br /> shallow soil samples were collected at each boring location. At four of the locations,deeper soil
<br /> samples(6 to 8 feet bgs)were also collected. Soil samples were analyzed for total petroleum
<br /> 59 Piezometric surface refers to an imaginary surface that defines the level to which water in a confined or semi-
<br /> confined aquifer rises to when measured in wells.For instance,groundwater may be located within permeable soil zone
<br /> under clay at 10 feet below ground surface(bgs)but within a well where it is not confined by the clay layer,rise to 5 feet
<br /> bgs.
<br /> 60 Amec Geomatrix,Inc.,2011.Fourth Quarter 2010, Groundwater Monitoring Program Report,2201 Bay Road,
<br /> Redwood City, CA.January 28.
<br /> 61 Ibid.
<br /> 62 REC are defined in ASTM E1527-05 as"the presence or likely presence of any hazardous substances or petroleum
<br /> products on a property under conditions that indicate an existing release,a past release,or a material threat of a release of
<br /> any hazardous substances or petroleum products into structures on the property or into the ground,groundwater,or surface
<br /> water of the property."According to ASTM E1527-05,the term"REU is not intended to include de minimis conditions that
<br /> generally do not present a material risk of harm to public health or the environment and that generally would not be the
<br /> subject of an enforcement action if brought to the attention of appropriate governmental authorities.
<br /> P:1RWC1401B Rocketship Sch-I\PRODUCrSUS-MND1Pu61ic1Ra ketship Public Review 09-29-16.docx(09/29/16)PUBLIC REVIEW DRAFT 53
<br /> ATTY/RESO.0084/CC RESO ADOPTING CEQA-ROCKETSHIP CHARTER SCHOOL APPEAL
<br /> REV:09-05-17 VR Page 61 of 124
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