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- `i i ; JUL ENVIRONMENTAL HEALTH SERW155i Mr. R. R.Zielinski Page 2 02320 0475 The water samples were analyzed using modified EPP methods 5030/8020/8095, which measure concentrations of total petroleum hydrocarbons-as-gasoline(fPH C),and benzene,toluene,ethyibenzene and xylenes(BTEX). Copies 0f the laboratory analysis reports and chain-of-custody martifest are presented in Attachment C. GROUNDWATER ANALYTICAL RESULTS b to 83,000 ppb; Concentrations of TPH-G In the groundwater sampies ranged tbro Twoparts n orping�ivteos record b andstantial MW 5 the range for the previous quarter was from 64Cto 84,000 MWA decr&sed from 94,000 to irom0.9 fo 2i,000 ppb. changes In dissolved TPH G concentrations, Increased from 30,004 to 83,000 ppb TPH-G. The berrzone eanceniratfons rang TPH-G and benzone concentrations In groundwater for Febr`a laboratory analyses for the la1991 are shown In st five sampiding (Attachment A). Table 2(Attachment B),presents results Of the events. j Sall VAPOR EXTPACTION TEST BACKGROUND Is and an angle installed during the Analytical results of soil samples collected a usod t delf'na the extent hydrocaborinC rbonlimpa°led soils beneath course of the subsurface investigation, a State-cs�iQm 2 iQ 2 5or00 pan°pe the Texaco service station site. These soil samples were analyzed by ranging of the samples collected contained detect able concentrations of TPH G E million(ppm).,9 samples contained detectable concentrations of benzene ranging from t to 1i ppm. acted soil appears to be confined Based on the laboratory analyses of the 6011 samples,hydrocarbon impto the r beneath the northeast corner of the site and has been definednot exten'directions fuerther than 20 feet north of the underneath Charter Way. Aseuming that the Impacted so,!do approximately 3,000 ruble yards. site,(under Charter Way),the volume of impacted soil Is estimated to be in estimated The avArage concentration of petroioum hydrocarbons weight ht of hydrocarbons oca bons between 4,300 to 0 8,700Ypound s and 1,000 parts per million(ppm)yielding a 9 Since Charter Way is State Route 4 and within the Cal Trans right hrwrtae;further subsurface exploration is .,at feasible because Cal Trans does not allow this type of enc lay to a depth of 30 to 35 fest soils encountered during drilling operations consisted predominateivs t and a fine micaceous sand, below ground surface(BGS). The clay Is underlain by water-bearing ;i SOIL VAPOR EXTRACTION PILOT TE METHOD E A soil-venitng pilot test uin was conducted on May 21, 1991• Pers isThe est wasas conducted ained to determine m the San gthe i County Air Pollution Control District prior to conducting the to ower regened f rre blower. Flaw rate radius of influence and the concentration of hydrocarbons In the soil vapor extracted from blower. , Flow and MV,4-5. Vapors were drawn from each extraction well by a 1.5 horsepas during the test was most orer'with a Kurz model a blower41 air velocity war,discharged dmeter,and irectly totheeatmosphere and cubic feet per minute(cfrn). Effluent air from the photo-Ionization detector(PiD). A sample concentrations were monitored during operation with a portable p c and shipped with a chain-of-custody from extraction wells MW-5 and Mw_4 was collected In TedlaB�5X020 for BTEX,and TPH-G. No sample Mani GTELforManalysis cause of the pto Pesence methods separate-phase petroleum to the well. was collected from ;....r..-. `GRoUNOWATiat TECHNOLOGY INC. 7