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scrept bac Page 15 equipment . January 1997 Record rainfall levels in early January 1997 caused severe flooding in the Central Valley. The site sustained over $30, 000 in damage . The canyon lost two drainage chevrons on the canyon sides, erosion blankets and a significant amount of hydroseed. An additional work order was issued to the State contractor to design and build an additional culvert . This began on January 27, 1997 . Drainage from the canyon created a small lake behind the check dam. There were no releases from the impoundment . Analysis of water samples revealed no contamination. E . Actual Impacts To Public Health And The Environment 1 . Pyrolitic Oil Production The potential for the release of large volumes of pyrolitic oil posed a threat to Little Panoche Creek since the drainage from this site would discharge directly into the creek. However, because of the intensity of the fire, very little pyrolitic oil runoff was observed. Pyrolitic oil that flowed from beneath the burning tires eventually impounded in the sump behind the existing earthen dam. By the time the flow reached the sump most of the oil was believed to have been consumed in the fire . The burning oil in the sump area created extremely high temperatures which began melting the corrugated iron pipe at the base of the dam. Only a trickle of oil was observed at the outlet side of the old drainage pipe . Later it was discovered that a significant volume of pyrolitic oil had actually seeped into a gravel layer before it was totally consumed by fire . This gravel layer extended from the upper reaches of the canyon and eventually tapered off in the lower canyon. The gravel layer was several feet below ground surface . The initial surface soil samples taken at the retention basin missed this subsurface contamination. 2 . Toxic Air Emissions For several weeks a dense black smoke plume drifted over the valley. Fortunately, the site was remote and population centers were not impacted. Gale force winds throughout the incident helped to disperse the smoke and pollutants . On-site air sampling immediately downwind and inside the smoke plume revealed low concentrations of target compounds . The concentrations of air contaminants were well below the OSHA Permissable Exposure Limits (PELs) , except for benzene concentrations in the center of the plume . One measurement indicated benzene levels at about 1 . 5 times the PEL. The results of off-site air sampling revealed low ambient levels of hazardous