ARCHIVED REPORTS XR0008203 - Laserfiche WebLink

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UPDATE 30 11-11-94 other than the wells that have been installed at this site for environmental evaluation and remediation Lithology Barriers The soils beneath Former Regal Station 604 , consist of a sequence of interbedded horizontal layers of silts, clays and fine silty sands These beds are not continuous throughout the site, but show facies changes laterally and bedding planes vertically, see Figure 6 and Figures 6A - 6J Sieve analyses were performed on samples obtained from the drilling of monitor wells MW1, MW2 and MW3 , see Tables 4 and Charts - Appendix C These analysis varify the lithology descriptions on the bore hole logs and the resulting lithology figures generated for this report, Figures 6A - 6J The primary lithologic barriers that would prevent and/or slow the movement of petroleum hydrocarbons are 1) vertically the horizontal bedding planes of silt and sands overlaying clay and 2 ) laterally facies changes from sand and salts to clays, see Figure 6 and 6A - 6J Overexcavation removed all of the tainted soil beneath the center pump island area and the majority of the gasoline range tainted soils beneath the eastern pump island area (AREA C) , the western pump island area (AREA A) and the UST area (AREA B) , see Figures 3B, 6 , 6A, 6B, 6C, and 6D Lateral and vertical migration of the petroleum hydrocarbons was limited beneath the pump islands by lithology type, predominately clay and clayey salts , and by facies changes of salts to clays or very fine sands to silts and clays Soil sample results from the borings drilled in Areas A and C indicate that petroleum hyrocarbons of degraded gasoline range tainted the soil to the 30 foot depth, with minor concentrations (2 mg/Kg TPHg) to the 40 foot depth, see Figures 6A - 6J and Sieve Charts As stated above, overexcavation removed the majority of the gasoline range tainted soils beneath the USTs Again lithology type was the primary factor in slowing and/or preventing the lateral and vertical migration of the hydrocarbons in the soil The area southeast of the UST excavation consisted predominately of clay and silts to the 25 foot depth The sand content then increased and at the 30 foot depth the formation was a very fine to very silty sand. The hydrocarbons` lateral and vertical rate of movement to the 25 foot depth would be slow and essentially equal through the very fine silts and clays, see Figures 6A - 6D and Sieve Charts The greatest lateral extent was achieved at the 30 foot depth Vertical migration continued, predominately at SB9, until ground water was achieved, see Figures 6F - 6J No free floating product ever accumulated on the ground water, only disolved concentrations were found at MW1, MWS and early in the investigation at MW2 , MW3 and MW4 page9