SITE INFORMATION AND CORRESPONDENCE

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The following criteria are used haus[ fumes, roofing tars, asphalt, Background when evaluating cleanup smoke from fireplaces, and cigarette Remedial Investigations remedies: smoke. PNAs move slowly in the en- From 1986 through 1996, PG&E vironment because they stick to soil conducted several environmental in- Federal Criteria and do not easily dissolve in water. vestigations at the Stockton former Some PNAs are suspected of caus- MGP site.In all,twenty-six surface soil 1) Long-term effectiveness and ing cancer in humans. Other PNAs samples were collected and seventy permanence may cause acute (short-term) and/ borings were drilled and sampled in 2) Reduction of toxicity, or chronic (long-term) health effects Areas 1, I1, and 111. Soil samples were mobility, or volume - if people are exposed to relatively high collected from the borings and ana- 3) Short-term concentrations of the chemicals. Ex- lyzed for chemicals related to the effectiveness posure to PNAs can occur if soils hav- former MGP and former underground 4) Compliance with applicable ing these compounds come into di- storage tanks.Twenty-seven ground- or relevant and appropriate rect contact with the skin or are in- water monitoring wells were installed requirements (ARARs) gested when an individual holds and in Areas I, 11 and near the streets lo- 5) Implementability then eats food with hands dirtied by cated around the PG&E property. 6) Overall protection of soils containing PNAs. Investigation Results human health and the BTEX compounds are chemicals Historical gas plant residues are environment found in petroleum products, gaso- mixed in soils below the ground sur- 7) Costs line, industrial solvents, degreasers, face in the central and southern por- 8) Acceptance by state paint thinners, and nail polish. Ben- tions of Area 1. Affected soils are be- agencies zene,a major component of gasoline. tween 1 and 25 feet deep depending 9) Acceptance by is known to cause cancer in humans. on where former underground struc- community Other VOCs may cause acute and/ tures existed.The highest concentra- or chronic health effects to humans tions of chemicals from residues are State of that are exposed to these chemicals. found at the location of buried former California Criteria Most VOCs are soluble to some ex- MGP structures.These areas(shown tent in water. VOCs move easily in Figure 3 as source areas) will be 1) Health and safety risks through soil and groundwater, and excavated to prevent any potential if exposed to air will evaporate rapidly. further impact to underlying soil and 2) Effects of contamination on groundwater. Soil being excavated present, future, and prob- For both PNAs and VOCs. the na- contains PNAs. VOCs and some fin- able beneficial uses of the ture and severity of health effects is dependent u how long and how organic compounds. on contaminated, polluted, or P P g threatened resources. much an individual is exposed to the 3) Effect of alternative reme- chemical. dial action measures 4) Site-specific characteristics 5) Cost effectiveness Figure 2 The Stockton 6) ?oientiul Former MGP Site environmental impacts I Sonora Street Former Paint AREA III Gas Plant Residues Manufacturing Areas I,II,and III were owned by PG&E. Gas plant residues include tars Building Areas I and II areowned by PG&E. and lampblack (a finely powdered carbon)that contain varying concen- Church Street trations of polynuclear aromatic 2 Service s Electric A P y Center Substation hydrocarbons (PNAs); and volatile d y c organic hydrocarbons (VOC's), in- d «!Je.Ndig 11 m ;f eluding benzene, toluene, E c tete Bulding tip ethylbenzene,and xylene compounds AREA I w(called BTEX). PNAs are chemicals Former MGPcommunications that are formed when organic mate- evlldin9 rials such as coal, oil, petroleum fu- :e on �e.saut els, or even foods are not completely Hazelton Avenue burned. PNAs are found in diesel ex- t