SITE INFORMATION AND CORRESPONDENCE

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• 0 Three groundwater zones were sults of the remedial investigations Glossary found directly beneath the site: zones and risk assessments, soils in Areas Asphalt Batching-soil is treated by A, B, and C. Zone A is the shallow 1I and III do not require cleanup.The mixing it with asphalt to bind up the groundwater zone. Zone B is deeper volumes of contaminated soil in Area chemicals.The soil can then be used for than Zone A. Zone C is the deep I which must be cleaned up to pre- pavement, groundwater zone.Groundwater first vent soil contaminants from reach- BTEx-Anacronymforgasoline occurs at about 35 feet below ground ing groundwater at detectable levels compounds benzene,toluene, surface. Zones A and B flow toward were developed using site data en- ethylbensene,and xylene. the east. Zones B and C are sepa- tered into a computer model. Like- rated by a 25-foot thick clay layer. wise, groundwater volumes were de- Groundwater-Water below the ground Zone C flows toward the southeast. veloped for extracting contaminated surface'hot moves slowly through the Groundwater immediately beneath groundwater. Natural attenuation spaces between soil and rock particles. the site has been affected by MGP- was also evaluated as a way to con- Feasibility study-A study to evaluate related chemicals.The extent of these tain and ultimately break down toxic alternatives to reduce or eliminate risks chemicals in groundwater has been chemicals in groundwater, posed by the chemicals at a site. determined horizontally as well as Eleven soil and groundwater Interim Remedial Measure(IRM)- vertieally..PNAs, BTEX, and Petro- cleanup'alternatives were evaluated A cleanup action token to protect public leum Hydrocarbons exist in ground- and screened using the federal and health and the environment while long- water, with the highest concentra- state criteria,described on Page 2,for term solutions are being developed. tions found in Zone A immediately be- the purpose of selecting a proposed neath the former underground stor- remedial alternative. A proposed re- Monitoring r a..alls-Wells drilled or specific locations to or around a site where age tanks areas and lower concen- medial alternative was chosen from groundwater can be sampled of selected trations found in Zone B and Zone C. the eleven alternatives.The proposed depths and studied to determine the direction alternative is discussed in the Feast- in which types Risk Assessments groundwater flows and the es A human health risk assessment bility Study and in the draft RAP. and amounts of chemicals present. and environmental risk assessment Remedial Action Plan Natural Attenuation-A naturally were performed as part of the reme- occurring chemical and biological process dial investigation in 1993.These stud- The proposed alternative in the that breaks down toxic chemicals into ran- lea were conducted to examine the po- draft RAP involves 1) excavating toxic chemicals in soil or groundwater. tential health effects if people, plants 10.000 cubic yards of soil in Area I of the site to protect future oundwa- Negative Declaration-The environ- or animals were exposed ul site soil p mental document that is prepared for and groundwater. The results of the ter and 2) natural attenuation of groundwater in Zones A, B, and C. projects that have no significant risk assessment indicate there are no known immediate human health or Restrictions will be maintained to environmental impact and meets the requirement of the California Environmen. environmental risks posed by the site. prevent exposure to affected soil and Pal Duality Act. There is no potential exposure to soil groundwater. Figure 3 shows the ar- or subsurface soil because the MGP eas to be excavated. Excavated clean PNA-An acronym for polynuclear site is covered by asphalt and sur- soil will be backfilled. Non hazardous aromatic hydrocarbon compounds. rounded by a fence. Groundwater in soil/residues will be disposed of at a Remedial Action-A corrective action the area is not used for domestic pur- permitted landfill offsite.If hazardous, taken to reduce,remove,or isolate poses. soil/residues will be treated using an chemicals in soil or groundwater. aspbait batabing process. Interim Remedial Measure Remedial Action Plan (RAP(- In 1992,an interim remedial mea- The draft RAP proposes monitor- A document describing which sum was conducted Just outside the ing groundwater for indications that remedial action (cleanup)alternative southern portion of the site between natural attenuation is occurring. The has been selected. the PG&E property boundary and groundwater will also be monitored to Remedial Investigation(RI)-A study Hazelton Avenue (called Hazelton Av- make sure the contaminated ground- to identify the types and extent of enue Strip on Figure 2).This small strip water is not moving away from the site. contamination ar a site. of exposed soil was shown to contain Every five years, the natural attenua- gas plant residues new the surface and tion will be evaluated for effectiveness. Risk Assessment-A study examining was covered With a concrete cap to pre- A contingency plan has been developed whether there is a potential for people vent any potential exposure to the soil. to address the possibility that contami- and/or the environment to be exposed to chemicals ata site and what the potential Feasibility Study noted groundwater might move offsite effects of exposure might 6e. A feasibility study was conducted during the remediation. PG&E also to develop potential soil and ground- proposes to make the interim remedial Petroleum Hydrocarbons-Any of water cleanup alternatives.Based on measure for the Hazelton Avenue Strip numerous organic compounds such as a final cleanup measure. this alter- gasoline and diesel that contain carbon historical property use, and the re- native was approved by DISC and hydrogen and are derived from on June 19, 1997. petroleum products. 3