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BIOSCREEN Model— UST B Mass estimates indicate 168 pounds of TPHg remain bound in the soil (Section 3.5.2). A BIOSCREEN model was run using the estimated 168 pounds of TPHg in remaining bound to the soil. To be conservative the highest recorded concentration in groundwater of 20 mg/L was used in the model. The model also used the longest projected attenuation timeframe of 15 years as predicted in Attachment G-2. The results indicate that TPH will attenuate to 0.1 mg/L in approximately 250 feet with no degradation. The first order decay results indicate that TPH will attenuate to 0.1 mg/L in less than 200 feet. BIOSCREEN model is included as Attachment H-1. BIOSCREEN Model—Bunker Mass estimates indicate 91 pounds of TPHd remain bound in the soil (Section 3.5.3). A BIOSCREEN model was run using the estimated 91 pounds of TPHd in remaining bound to the soil. The model also used a timeframe of 15 years. The results indicate that TPHd will attenuate to 0.1 mg/L in less than 200 feet with no degradation. The first order decay results indicate that TPHd will attenuate to 0.1 mg/L in less than 160 feet. The BIOSCREEN model is included as Attachment H-2. 3.5 Soil Mass Estimates 3.5.1 Soil Mass Estimate—UST A Upon review of the available data and the UST Remediation Proposal — Excavation Only Workplan, there is no significant impacted soil remaining in the location of the former UST A (Minney, 2010). 3.5.2 Soil Mass Estimate—UST B Mass estimates were calculated using the interpretation of the extent of soil contamination shown on Figure 10. Mass calculations show that there are approximately 168 pounds of TPHg and 0.2 pounds of benzene bound to soil in the area near UST B as summarized in Table 8. TPHd was effectively removed. The excavation activities removed approximately 5,331 pounds of TPHg and 17 pounds of benzene as summarized in Table 9. 3.5.3 Soil Mass Estimate- Bunker Mass estimates were calculated using the assumption of approximately 5 feet of impacted soil 10 feet thick in each direction beyond the excavation. Mass calculations show that there are approximately 91 pounds of TPHd and 375 pounds of Oil and Grease bound to soil in the area near the Bunker as summarized in Table 10. No benzene was present in the floor and sidewall samples. The excavation activities removed approximately 2,025 pounds of TPHd and 492 pounds of Oil and Grease as summarized in Table 11. - 14-