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t <br /> 4 w 1 <br />' I <br /> _ CAMBRIA <br /> TECHNICAL RATIONALE FOR PROPOSED SCOPE OF WORK �P� N0 j <br /> • Gasoline constituents were detected in shallow groundwater amples collected from cone-q'(OM <br /> d^ <br /> penetration test (CPT) borings in the area north of the site. Shell proposes installing one 1 2,UD <br /> shallow monitoring well to assess gasoline constituents im a t downgrade of the s to <br /> JaAe dw�-fct- &s'a`(o x gr a1 r"kj0, 2� L <br /> • Gasoline constituents were detected in groundwater samples collected from CPT borings at <br /> LAA� -r`2,the 45-50 foot interval. Repeatable monitoring of this groundwater interval is warranted to j A <br /> �'�r��determine lateral extent of impact and concentration trends over time. Shell proposes <br /> Y (/( <br /> a-�(f -ja installing monitoring wells screened at this interval to further assess the groundwater plume. <br /> • Gasoline constituents were detected in groundwater samples collected from CPT borings at <br /> o? the 65-77,foot interval. Repeatable monitoring of this depth zone is warranted to determine <br /> the vertical extent of impact and concentration trends over time. Shell proposes installing <br /> Gf'f`l 1,,,1 Cd'�" tj <br /> G , monitoring wells screened at this depth interval to further assess the groundwater plume. <br /> t'O <br /> � �' • Based on a review of site data, the SJCEHD identified a potential migration pathway and <br /> recommended installing one additional well screened in the upper portion of a deep sand unit <br /> to monitor groundwater in the vicinity of former boring CPT-5. Cambria is interpreting this <br /> depth as the 65-77 foot interval as discussed above.. �'-' — Av6R2y - Z 2- 85 Vit-;) <br /> • Upgradient delineation is warranted due to 1,2-dichloroethane impact to groundwater. One <br /> upgradient soil boring is proposed in the southern portion of the site. <br /> WORK PLAN <br /> Work Tasks <br /> Permits: Cambria will obtain drilling permits from SJCEHD. Additionally, Cambria will obtain <br /> access agreements for the proposed offsite borings prior to initiating field work. <br /> Site Safety Plan: A Site Safety Plan will be prepared for field work. <br /> Utility Clearance: The proposed drilling location will be marked and cleared through <br /> Underground Service Alert and a private utility locating company prior to drilling. <br /> Site Investigation: Shell proposes to drill 14 soil borings to further assess the extent gasoline <br /> constituents in the vicinity of the site (Figure 2). Thirteen of the 14 borings will be converted to <br /> groundwater monitoring wells. The monitoring well borings will he drilled using Roto-sonic <br /> drilling equipment or another appropriate drilling method based on the recommendations of the <br /> drilling company. Boring CPT-18 will be drilled using CPT drilling equipment. <br /> 0778 2 <br />