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I • cone penetration determinations of soil classification Groundwater samples from below 115' were difficult to extract Some hydro punch samples required more than 4'of screen and required more than 15 minutes of collection time to retrieve 120 m1 of groundwater Conclusions from Sample Analysis and Cone Penetration Data The extent of hydrocarbon contamination of the groundwater is deeper than the 135'that was originally anticipated by the work plan for this CPT investigation In the area of the estimated spill point (near MW#1), CPT#2 water samples indicate contamination of the groundwater in the range of 10000 ug/L for TPHg, at a depth of 135 feet Most likely the groundwater contamination extends more than 150' below the surface It is the authors opinion that the major source of the gasoline contamination for this site is the UST's on the site or the related dispenser piping The contamination has spread from the UST and dispenser area to the northwest (see attached Contour Map of 1,2-DCA levels) Extraction of groundwater below 115' of depth will be very slow process The estimated permeability of the soil at this depth is in the range of k = 1 x10-6 to k= I xlO-7 for the areas investigated by the scope of this work plan The more permeable strata of sandy silts in the depths below 115'will be very difficult to isolate for any extraction remediation methods As a result, cross contamination between strata during any type of groundwater extraction method is highly likely Recommendations for Future Work It is recommended that the site continue to be monitored on a quarterly basis A deep monitoring well should be installed near the location of CPT#2 to a depth of 150' below the surface The existing work plan required the installation of monitoring well MW#IOS and MW#IOD in the area of CPT#3 It is recommended that this work start with the depth of well for MW#I OS be 60', and the depth of well for MW i O#D be 150' Recommendations for Soil and Groundwater Remediation(Requested by J Barton RWQCB) The soil contamination above groundwater could be reduced using vapor extraction in the general area of the UST's and the dispensers The well defined sand strata from I O'to 30'ofdepth will serve as a good conduit for soil vapor movement The remediation of the groundwater on this site is much more difficult Results will be very slow under any remediation method due to very low permeability Groundwater extraction and treatment will be the most successful in the sandy silt strata at depths from 80' to 115'below the surface Below 115' foot of depth, any method of remediation will be extremely slow due to the low permeability of those soils Muchmore work will be required to design an effective groundwater remediation system To complicate the problem, the must desirable location for extraction wells is in the building Suspected Errors in Chemical Analysis The soil samples from CPT#3 and CPT#4 indicate the presents of MTBE These samples were part of ithe same run done by Castle and likely were subject to contamination within the laboratory The analysis for each sample are basically the same, which is very uncommon for any set of samples (see Soil 3