COMPLIANCE INFO_1992-1993 - Laserfiche WebLink

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Mr. Robert Graulich Page 7 b. Large exposed surface area of the ash pile (19,049 m2, the size of the ash pile at the facility) , without limits to the ash available for dispersion; C. Potential receptors are permanently located downwind of the site, allowing for 70 years of constant exposure. Based on the models and the above described assumed conditions, even using the more conservative CAPCOA unit risk level, exposure was estimated to potentially cause an excess cancer rate of 4.48 x 10-7. This value is less than the rate of 1 x 10'6, which is accepted as the threshold for risk (i.e. , one in a million) . CONCLUSIONS Based on the information and data provided to the Department by Wadham and its consultant ENSR, the Department concurs with Wadham's determination that the ash currently being generated at the Williams facility is not hazardous waste (subject to the conditions specified below) . This determination is dependent upon the accuracy and representativeness of the data and information presented, and upon the validity and applicability of the risk assessment techniques used. If, for any reason, the characteristics of the ash significantly change such that the data and information presented to the Department for this determination no longer describe the characteristics of the ash, Wadham will be required to manage the ash as hazardous waste. This determination applies only to the currently generated ash, not the ash which was previously generated and which has been stored in piles at the facility. The Department's May 2, 1990 determination is still effective for the classification of the previously generated ash. Although the Department concurs with Wadham's classification that the currently generated ash is nonhazardous, the management and disposal of the ash remains subject to the jurisdiction of the regional water quality control board and local agencies. In addition, there remains a concern regarding the amorphous silica present in the waste. Although there is research which raises questions regarding amorphous silica, it is our opinion that insufficient scientific research has been conducted to conclusively establish amorphous silica as a causative agent for silicosis or pneumoconiosis in humans. Although the Department does not consider the presence of a significant amount of respirable amorphous silica to be reason to classify the ash as hazardous waste, the questions and suspicions about amorphous silica may warrant a more conservative approach by the Department in any future regulatory development regarding this waste or any waste containing amorphous silica.