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7.3.B. - Page 67
<br /> ENVIRON was retained by the project applicant to perform a Phase I Environmental Site Assessment (ESA) of the
<br /> properties that comprise the project site. The objective of the Phase I ESA, which was conducted in conformance
<br /> with the scope and limitations of ASTM International's "Standard Practice for Environmental Site Assessments:
<br /> Phase I Environmental Site Assessment Process E 1527 -05" (the `ASTM Standard'), was to identf Recognized
<br /> Environmental Conditions (RECs), as defined in the ASTM Standard. RECs are defined (ENVJRON, p 3) as "the
<br /> presence or likely presence of any hazardous substances or petroleum products on a property under conditions that
<br /> indicate an existing release, a past release, or a material threat of a release of any hazardous substances or
<br /> petroleum products into structures on the property or into the ground, groundwater, or surface water of the
<br /> property.... The term is not intended to include "de minimis" conditions that generally do not present a threat to
<br /> human health or the environment[.]"
<br /> The ESA revealed no evidence of RECs except for the following:
<br /> Contamination Related to Former Automobile Fueling and Repair Operations. Historical resources indicate a
<br /> gasoline service station operated from approximately the 1930s through 1960s . on the western part of the
<br /> currently vacant portion of the project site (along Jefferson Avenue). Based on a review of documents obtained
<br /> from the San Mateo County Environmental Health Division (SMCEHD), five gasoline underground storage
<br /> tanks (USTs) (two 1,000 - gallon USTs and three 500- gallon USTs) were removed from the location in December
<br /> 1989. An investigation conducted prior to the UST removals indicated the presence of total petroleum
<br /> hydrocarbons as gasoline ( TPHg) and TPH as diesel (TPHd) in soil and groundwater beneath the site.
<br /> Following removal of the USTs, multiple soil excavation events and additional site investigation took place between
<br /> approximately 1990 and 1994. Sampling activities identified TPH contamination in soil beneath the southern
<br /> portion of the parcel, beginning at approximately seven feet below ground surface (bgs) and extending to
<br /> groundwater, which appears to be encountered between eight and eleven feet bgs. Other chemicals typically
<br /> associated with TPH contamination - such as benzene, toluene, ethyl benzene, and xylenes (BTEX) - were generally
<br /> not detected in soil or were detected at relatively low concentrations, and according to SMCEHD documentation,
<br /> benzene was never detected in groundwater beneath the site. Excavation activities were implemented to remove
<br /> contaminated soil in proximity to the former USTs and in the vicinity of the historical location of auto repair
<br /> equipment, including a subgrade sump. It appears that some soil was disposed off-site, while other soil may have
<br /> remained at the site and used as backfll. In 1994, a Corrective Action Plan (CAP) prepared for the former gas
<br /> station parcel selected excavation and on -site aeration of soil as a final cleanup remedy, and a revised CAP
<br /> prepared in 1995 recommended additional excavation and remedial activities to address TPH contamination in soil
<br /> at depth across the parcel, but it does not appear that the CAP was ever implemented.
<br /> Based on the lack of significant groundwater impacts beneath the parcel and in accordance with a San Francisco
<br /> Regional Water Quality Control Board (RWQCB) directive regarding the closure of "low risk" sites, the SMCEHD
<br /> issued "no further action " for the former USTs in August 1997.
<br /> The case closure report stated that approximately 910 cubic yards of contaminated soil remained on the parcel at
<br /> the time closure was issued, with residual concentrations up to 710 mg /kg TPHg, which is elevated above the
<br /> current, established regulatory screening level of 100 mg /kg. Closure documentation also contained information
<br /> regarding construction activities for the adjacent Jefferson Street railroad underpass, a project that began in 1997
<br /> and included excavation and grading on a portion of the project site to meet the new (lowered) elevation of
<br /> Jefferson Avenue. The full extent of on -site excavation and associated grading as part of the underpass project is
<br /> not clear. In addition, SMCEHD closure documentation indicated that a due diligence investigation performed for
<br /> the northern portion of the project site in the mid -1990s (presumably on behalf of the City of Redwood City when it
<br /> acquired the current vacant parcels at the site, including the former gas station parcel) identified a concentration of
<br /> TPHg in excess of current regulatory screening values in a grab groundwater sample. The detection was not
<br /> confirmed through installation of permanent well(s), and the source was reportedly not known; no further
<br /> investigation was conducted or required.
<br /> Although the case received closure from the SMCEHD and human health risks associated with the presence of
<br /> residual contamination in this portion of the project site are likely to be low, residual impacts in soil in excess of
<br /> current regulatory screening criteria is considered to represent an REC. Site excavation for construction of the
<br /> proposed parking garage could encounter contaminated soils. Therefore, in conformance with the DTPP program
<br /> EIR (Chapter 14, Hazards and Hazardous Materials — Exposure to Existing Hazardous materials Contamination,
<br /> pp. 14 -13 and 14 -14), the proposed project would be subject to compliance with all applicable existing local -,
<br /> county-, regional -, and State - mandated site assessment, remediation, removal, and disposal requirements of the
<br /> City of Redwood City, San Mateo County Environmental Health Division (SMCEHD), Regional Water Quality
<br /> Control Board (RWQCB), State Water Resources Control Board, California Department of Toxic Substances
<br /> Control (DTSC), and other responsible agencies.
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