HomeMy WebLinkAbout[Untitled]_5-6Former Phoenix & Son Garage & Storage 20 September 2016
Bakersfield, Kern County
Closure Summary
by the Policy, was present in the area of one of the permanent soil-gas wells, but not in the other,
and th6t the Policy's, screening level Vapor Intrusion to Indoor Air were satisfied.
Central Valley Water Board staff requested two additional rounds of soil-gas sampling during
2015 and 2016. The benzene concentration of 690 pg/M3 detected during the first additional
sampling, exceeded the Vapor Intrusion screening level criteria, and ethylbenzene, and xylenes
were not detected at Reporting Limits less than the screening level criteria. Benzene,
ethylbenzene and naphthalene were not detected during'the second sampling. The consultant
concluded that there was no significant risk from Vapor Intrusion.
Soil Rernediation
An undocumented secondary hydrocarbon source mass was removed. in 2000, during the UST
system removal activities. Remedial alternatives to reduce the ,hydrocarbon source mass in . soil
were evaluated. Excavation would be limited, due to the proximity of on.site buildings, the depth
of contamination and cost. Bioremediation by natural attenuation was.recommended as a
feasible, low cost remedial alternative, since free phase petroleum product was absent, and site
use was . not expected to changeduring the long time period required, and the release did not
have the mobility to migrate to. groundwater, which is at greater than 200 feet bgs in the area.
Sensitive Receptors
The Site is within an area of commercial/industrial properties. A sensitive receptor survey
conducted by the consultant during 2015 did not identify supply wells! schools, hospitals, or
churches within 1,000 feet of the release. The Kern Island Canal is approximately 900 feet
southwest of the Site, but is not a receptor, sin_ ce groundwater is not affected by the UST
release.
Low-Threat Underground Storage Tank Case Closure Policy Evaluation
The subject UST release satisfies all relevant General Criteria:
a. The release is within the service area of a public water system;
b. the release consists only of petroleum;
c. the ("primary") release from the UST system has been stopped;
d. free product is not present. The criteria for free product removal to the maximum
extent practicable is not relevant;
e.. a Conceptual Site Model has been completed. The assessment and sensitive
receptor survey contained in site assessment reports provide sufficient data for
Central Valley Water Board staff to complete the Conceptual Site Model;
f. secondary source has been removed to the extent practicable. , The remaining
source mass is expected to naturally degrade;
g. soil or groundwater have been tested for,methyl tertiary butyl ether (MTBE), in
accordance with Health and Safety Code section 25296.15; and
h. nuisance as defined by Water Code section 13050 does not exist.
The subject UST release satisfies the relevant Media-Specific criteria:
1. . Groundwater — There is no evidence that the release had sufficient mobility to migrate to
groundwater, which is known to be at least 120 feet beneath the bottom of soil
contamination. The criteria are not applicable.
2. Petroleum Vapor Intrusion to Indoor Air —Confirmation soil gas sampling data satisfies
criteria contained in Appendix 4, Appendix 4 (Direct Measurement of Soil Gas
Concentrations).