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S E C O R r` 1� According to the transport model MT3DMS conducted in the Groundwater Modeling Report January 2005, the mobility of the contamination identified at the site is expected to be low to non existent. Factors causing low mobility of contamination include: • adsorption of the remaining constituents to particulate surfaces; • lack of rainfall or atmospheric moisture to transport the contaminants past the top layers of shallow soils; • paved surface in the site vicinity prevents downward movement of surface water; • high surface tension of water in silt and clay in the shallow soils inhibit downward movement of solutes; • depth to groundwater of 50 ft or more. ! 6.0 NO FURTHER ACTION REQUIRED STATUS RATIONALE SECOR formally requests that this site be granted NFA status based on the following rationale: • With the primary sources of petroleum hydrocarbon impacts removed, the groundwater plume and the MtBE contamination at the site is mainly isolated in the A -Zone near the former USTs. With the primary source removed, the groundwater plume is expected to decrease with time by natural attenuation and/or biodegradation. • The GWE and SVE system has reduced groundwater impacts by a large percentage and the incremental cost for further mass removal exceeds the incremental benefit. • The remaining impacts at the site presents a low risk and the transport model MT3DMS F, conducted and summarized in the Groundwater Modeling Report January 2005 indicates the mobility of the contamination identified at the site is expected to be low to non existent. • Groundwater analytical results summarized in Table 3 demonstrate the groundwater Plume is stable and is decreasing in hydrocarbon concentration. Although groundwater contains MtBE above water quality objectives in an isolated area, best available, cost-effective technology has been implemented and chemical concentrations in groundwater are projected to meet water quality objectives through natural processes. Based on the shallow depth, limited extent of hydrocarbons in soil, and relatively low concentrations of hydrocarbons in soil and groundwater, it is unlikely that the conditions remaining at the site will adversely impact water quality, human health and safety, or other beneficial uses. 95775 NFAR REPORT Final.doc 12 SECOR International Incorporated