WORK PLANS - Laserfiche WebLink

Home Browse Search

CAIP Addendum:Former Fue2171g Station, 7500 West Eleventh Street, Tracy, CQ Page 9 525 gallons (Section 2.1.6), the volume of groundwater containing dissolved fuel hydrocarbons that will be extracted is approximately 9,475 gallons, or 35,867 liters. From Section 2.2.1.4 above, the estimated concentration of fuel hydrocarbons in the groundwater is the mean of the estimated concentrations in the'two sub-areas: one that lies between Monitoring Wells MW-13 and MW-7 and the second that lies between Monitoring Wells MW-7 and MWFP-3; that value is 50,575 µg/L. At that concentration, a mass of 1.81 grams of dissolved hydrocarbons would be removed from the subsurface by pumping 9,475 gallons of contaminated groundwater. That equates to 3.35% of the dissolved components of fuel hydrocarbons beneath the area of the site affected by LNAPL. (oo0®5ns-?5- lv)138,000 L} w1.g2 K1 2.2.1.5.4 Total Mass of Contaminants Extracted The sum of the estimates of the masses of contaminants extracted by excavation of soil from the trench (138,324 grams), pumping of the extractable volume of LNAPL (1,589,873 grams) and pumping of groundwater containing dissolved components of fuel hydrocarbons (1.81 grams) yields the total mass to be extracted. TOTAL MASS OF CONTAMINANTS TO BE EXTRACTED= 1,728,199 GRAMS. That mass amounts to 37.37% of the total mass (4,625,025 grams) of components of fuel hydrocarbons in the subsurface beneath the area of the Navarra Site that was estimated in Section 2.2.1.3 to be affected by LNAPL.Of the total extracted mass, LNAPL represents 92%, affected soil represents 8% and the mass extracted in groundwater represents 0.00006%. These figures demonstrate the dominant role that extraction of LNAPL plays in a successful groundwater remediation program. Removal of contaminated soil makes a more modest contribution to total contaminant reduction, while pumping of even large volumes of groundwater has very little practical effect. These figures also demonstrate why attempts to remediate sites where clay and other-low permeable soils are affected by petroleum hydrocarbons by "pump and treat" methods are rarely effective. Conversely, the figures demonstrate that successful remediation of recoverable LNAPL is of great benefit because it significantly reduces the total contaminant load affecting the subsurface. Note: If, as might be predicted by the Testa and Paczkowski method (see Section 2.1.5), 100% of the LNAPL in the subsurface, i.e., 1,050 gallons, could be recovered, then the total mass of contaminants extracted would have an estimated mass of 3,318,072 grams, or 72% of the total mass of components of fuel hydrocarbons in the subsurface beneath the area of the site affected by LNAPL. It is important to note that the remediation technology based on removal of LNAPL from an extraction trench that has been proposed for the Navarra Site does not primarily rely on removal of a very large percentage of the total contaminant mass from the subsurface. What it is intended to achieve is to create conditions that will permit an acceleration of