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} Additional Groundwater Investigation Report CSUS Multi-Campus Regional Center August 19,2003 Page 3 Cc monitor well MW-2 during the March 2003 monitoring event. A slight petroleum odor was noted in the groundwater recovered from MW-2, and has consistently been noted in the field:!:inspection samples collected from monitor well MW-3. Benzene, toluene, ethylbenzene, total xylenes (BTEX), TPH-G, L methyl tertiary-butyl ether (MTBE), and.1,2-DCA have consistently been detected in the groundwater ' samples collected from monitor well MW-3:In addition, TPH-D.was detected in the groundwater sample collected from MW-3 during the March 2003 monitoring event. The groundwater gradient direction has fluctuated from slightly north of east to southeast. Condor prepared a Problem Assessment Work Plan (PAWP) for the site dated January 23, 2003, to ( describe additional groundwater investigation at the site. The PAWP was prepared at'the request of Mr. {{ Rosso in response to a letter dated April 26, 2002 from Ms. Setliff of the SJCEHD. As requested by the SJCEHD,the PAWP also included a remedial feasibility evaluation that compared and"discussed remedial techniques for site remediation. Over-excavation and in-situ groundwater remediation were selected to minimize total remediation time. ! Condor prepared a .Work Plan for Soil and Groundwater Remediation (work plan), dated March 3, 2003, to describe proposed soil and groundwater remediation activities to be conducted at the CSUS site. The work plan was prepared at the request of Mr. Rosso. The scope of work described:in this work plan included: (1) groundwater dewatering including installation of dewatering wells, groundwater treatment, and proper disposal of treated groundwater; (2) soil over-excavation, including transport and disposal of 4 contaminated soil near the former UST location; and, (3) in-situ groundwater;:remediation after completion of soil excavation and backfill utilizing ozone sparging technology. The SJCEHD discussed the PAWP, dated January 23, 2003, and work plan, dated March 3, 2002, in a letter dated March 13, 2003 to Mr. Rosso. In the letter,Ms. Margaret Lagorio and Mr. Nuel Henderson of the SJCEHD approved the proposed CPT groundwater investigation described in"' the PAWP and concurred with Condor's recommendation that additional groundwater monitoring wells were needed to characterize and monitor the site. The SJCEHD also approved soil over-excavation as an interim remedial i measure at the site. In addition, the SJCEHD approved ozone sparging as an interim remedial measure at the site,pending the results of additional groundwater characterization. 3.0 CPT AND DIRECT PUSH BORING FIELD PROCEDURES On April 14 through 17, 2003, Condor conducted an additional groundwater investigation at the site using I g gT g g direct push boring methods. Condor supervised the completion of five deep CPT bonng pairs (CPT-4 through CPT-8)and one shallow hydropunch boring(GP-10). The boring locations are shown in Figure 2, Attachment A. CPT boring pairs were advanced in five locations in order to evaluate the vertical extent of 4 k groundwater contamination in the vicinity of the former USTs and at the anticipated"cross- and down- gradient extents of the plume. At each deep boring pair location, the first boring was advanced to provide a near-continuous log of the subsurface soil profile. The second boring at each pair location was advanced _ proximal to the first boring to collect a discrete groundwater sample from saturated horizons identified in geologic logs from the first borings. A single hydropunch boring (GP-10) was advanced to collect a groundwater grab sample to investigate the lateral extent of contamination in shallow groundwater. This section includes a description of the site preparation direct push boring procedures; and groundwater sample laboratory analyses. The boreholes were drilled by Gregg In Situ, Inc. of Martinez, California. A detailed presentation of the cone penetration test data and field equipment and procedures is provided in Attachment B. .1.1 coN©'OR . 4 .