Laserfiche WebLink
2.3 EXTENT OF PETROLEUM HYDROCARBONS <br /> Based on the soil analytical data reported from the analysis of perimeter samples <br /> ' obtained during remedial excavation, elevated hydrocarbons concentrations were <br /> determined to remain only adjacent to the restroom structure The maximum <br /> lateral extent of soil contamination can be estimated from the locations and the <br /> ' analytical results of the soil samples collected from the soil borings advanced in this <br /> investigation BAI estimates the maximum volume of soil containing petroleum <br /> ' hydrocarbons in the impacted area (27 square feet) to be approximately 108 cubic feet <br /> This volume is based on the area between the soil borings and the excavation <br /> boundary and the estimated thickness of the zone where hydrocarbons are <br /> ' concentrated Hydrocarbons are assumed to have laterally migrated away from the <br /> UST excavation in a zone directly above the water table which BAI conservatively <br /> estimates to be four feet thick Total volume of affected sods is estimated to be 108 <br /> ' cubic feet (4 cubic yards) The estimated area of concern is shown on Figure 2 <br /> An estimate of the quantity of hydrocarbons remaining at the site can be obtained by <br /> ' using the volume of soil multiplied by the density of soil and the estimated average <br /> concentration of petroleum hydrocarbons existing within the four foot thickness on <br /> soil with elevated levels of TPHd The average TPHd concentration of the four-foot <br /> thick impacted area is conservatively estimated to be one half of the 40 mg/Kg <br /> concentration reported from the soil sample obtained lust above the groundwater in <br /> the remedial excavation completed in December 1991 The average concentration is <br /> chosen because the concentration is shown to decrease to non-detectable levels over <br /> the area of concern BAI estimates the quantity of petroleum hydrocarbons to be the <br /> following <br /> ' Quantity of Hydrocarbons =Volume x Approximate Soil Density x <br /> Average Concentration <br /> = 108 ft3 x 45 K /ft3 x 20 m K <br /> g mg/Kg <br /> = 9 7x104 mg <br /> ' = 97 grams of petroleum hydrocarbons <br /> This estimate is based on limited characterization of contaminant concentrations in <br /> ' the sods adjacent to the former source area, and as such, is of limited reliability <br /> 1 <br /> 4 <br />