|
4'.
<br /> SITE BACKGROUND
<br /> The site contained three underground storage tanks (USTs) associated with past uses of the site. On July
<br /> 22, 1998 Henderson Construction of Stockton, California removed all three USTs from the site, each
<br /> from a separate excavation, A fuel dispenser island was also removed. Tank 6 (TK6)reportedly contained
<br /> fuel oil for a generator room. Tank 10 .(TK10) was reportedly a 10,000-gallon capacity UST formerly
<br /> containing diesel fuel. Tank 11 (TKI1) was reportedly a 1,000-gallon capacity UST formerly containing
<br /> gasoline. TK10 and TK11 were located adjacent to the north and south end, respectively, of the former
<br /> fuel dispenser island. TK6 was located approximately 100 feet southeast of TK10, TK11, and the fuel
<br /> dispenser island.
<br /> On July 23, 1998, a Condor representative was on-site to collect soil samples from the excavations under
<br /> the direction of Ms. Letitia Briggs of the San Joaquin County Environmental Health Department
<br /> (SJCEHD). The soil samples were analyzed by APCL of Chico, California. Henderson Construction
<br /> prepared a brief letter report, dated August 31, 1998, describing the UST removal activities, soil sampling
<br /> activities, and laboratory analytical results of the soil samples.
<br /> Field observations and the laboratory analytical results of the soil samples.indicated that further
<br /> subsurface investigation of the TK6 and TK1 I excavations was not necessary. Field observations and the
<br /> laboratory analytical results of the soil samples collected from beneath the former location of TK10,
<br /> however, indicated the presence of diesel range petroleum hydrocarbons.
<br /> In a letter dated April 28, 2000, the SJCEHD requested the submittal of a,work plan to investigate the
<br /> lateral and vertical extent of contamination at the site. At the request of California State University at
<br /> Stanislaus (CSUS),, Condor subsequently prepared and submitted the Work Plan for Soil and
<br /> Groundwater Sampling by Direct Push (Geoprobe), dated June 21, 2000. In a letter dated July 7,.2000,
<br /> Ms. Carol Oz of the SJCEHD approved the work plan (with modifications) and requested that the work
<br /> be conducted within 90 days and that a report of findings _be submitted within 60 days of work
<br /> completion.
<br /> On December 28 and 29, 2000, Condor conducted a limited soil and groundwater investigation utilizing
<br /> Geoprobe® direct push technology at the site. Condor prepared the Preliminary Investigation and
<br /> Evaluation Report (PIER), dated February 7, 2001, describing the results of the work. Laboratory
<br /> analytical results of the soil and groundwater samples and field observations indicated that petroleum
<br /> hydrocarbons were present in site soil and groundwater down to the approximate total depth of the
<br /> investigation (36 feet below grade). Based on the results of the investigation, Condor recommended the
<br /> installation of three cone penetrometer (CPT) borings to investigate the site geology, three direct push
<br /> borings to collect soil samples, and three Hydropunch borings to collect discrete groundwater samples at
<br /> depths to be determined by the results of the CPT borings. The purpose of borings was to continue with
<br /> evaluation of the vertical and horizontal distribution of petroleum hydrocarbon impacted .soil and
<br /> groundwater at the site. Condor also recommended the installation of three groundwater monitor wells to
<br /> establish the groundwater gradient and to monitor the concentratidns of petroleum hydrocarbons in site
<br /> groundwater. In addition, Condor recommended the completion of a sensitive receptor survey (SRS)
<br /> within a radius of 2,000 feet of the site to investigate the potential for receptors that may be impacted by
<br /> petroleum hydrocarbons in the groundwater.
<br /> In a letter dated April 4, 2001, to Mr, Cliff Bailey of CSUS, Ms. Dot Lofstrom of the SJCEHD concurred
<br /> with the recommendations contained in the PIER. At the request of Mr. David Rosso for the Trustees of
<br /> the California State University, Condor prepared the Work Plan - Additional Soil and Groundwater
<br /> Investigation, dated October 5, 2001. The proposed work included the installation of.CPT borings,'direct
<br /> lv --
<br />
|