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SUMMARY OF PREVIOUS INVESTIGATIONS AND REMEDIAL ACTION
<br />Environmental investigations have been conducted at the Site since 1989. A summary of
<br />previous assessments conducted at L&M OU, UOU, and MOU is presented below.
<br />In August and September 1989, Applied Geosystems (AGS) conducted a soil gas survey (VP-1
<br />through VP-14) at the Waterfront Redevelopment Property, and subsequently installed three
<br />groundwater monitoring wells (MW-1 through MW-3) at the Site. A water supply well survey
<br />was also performed, which confirmed the presence of two municipal water supply wells in the
<br />vicinity of the Site. One of the municipal water supply wells, owned by the City of Stockton and
<br />constructed in 1972, was identified approximately 2,200 feet (ft) east of the Waterfront
<br />Redevelopment property. Another municipal water supply well, maintained by California Water
<br />Service, was identified approximately 5,000 ft southeast of the Site. A total of six industrial wells
<br />were located at the Fiberboard Paper Company, approximately 2,000 ft southwest of the Site;
<br />these wells were reportedly installed between 1921 and 1954 (AGS,October 31, 1989).
<br />In July 1990, sixteen soil borings (B-4 through B-19) were drilled by AGS to investigate the
<br />extent of petroleum hydrocarbons beneath the Site. Four of the soil borings (B-4 through B-7)
<br />were converted to groundwater monitoring wells (MW-4 through MW-7). Results are included in
<br />AGS’ report entitled Evaluation of Hydrocarbons in Soil and Ground Water at City of Stockton
<br />Waterfront Redevelopment Property, West Weber Avenue and North Lincoln Street, Stockton,
<br />California, dated January 29, 2001.
<br />In October 1996, a total of 22 additional soil borings (TR-1 through TR-22) were drilled across
<br />the Site to determine the type and assess the extent of petroleum hydrocarbons in shallow soil
<br />and in groundwater. Four of the borings were converted to groundwater monitoring wells
<br />(MW-8 through MW-11). Results are presented in Treadwell & Rollo’s (T&R) report entitled
<br />Subsurface Investigation, South Parcel, West Weber Avenue & North Lincoln Street, Stockton,
<br />California, dated November 8, 1996.
<br />In January and February 1999, Environmental Resolutions Inc. (ERI) conducted a tidal study to
<br />determine the influence of tidal fluctuations on the direction of groundwater flow, collected
<br />additional data to evaluate concentration trends, and collected inorganic water quality data to
<br />investigate whether natural attenuation is occurring beneath the Site. Pressure
<br />transducers/data loggers were installed in wells MW-5, MW-8, and MW-9 to monitor changes in
<br />water levels within the monitoring wells over a 48-hour period. Results of the tidal study
<br />indicated that over the testing period, observed tidal changes (up to 4 ft) had little influence on
<br />the southerly direction of groundwater flow in the monitoring wells (less than 0.1 ft). Results of
<br />this multi-phase assessment are provided in ERI’s Groundwater Monitoring and Sampling and
<br />Tidal Influence Study Report, The Stockton Group Site, West Weber Avenue and North Lincoln
<br />Street, Stockton, California, dated June 11, 1999.
<br />Between August and October 1999, T&R oversaw a geophysical survey on Parcels 2A, 3,
<br />and 4, which involved the excavation of exploratory test pits (2ATP-1 through 2ATP-5, 2BTP-1,
<br />3TP-1 through 3TP-4, 4TP-1 through 4TP-3) to determine the location of suspected
<br />underground structures including underground storage tanks (USTs), sumps, and pipelines.
<br />Additional soil borings were drilled (2AB-1 through 2AB-4, 2BB-1 through 2BB-3, 3B-1, 3B-2,
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