ARCHIVED REPORTS_XR0003137 - Laserfiche WebLink

Home Browse Search

' k-9 KLEINFELDER For a summary of the results of the chemical analyses conducted, please refer to the attached Table 1 30 FINDINGS ' The groundwater flow direction was calculated to be towards the east with a gradient of approximately 0 005 ft/ft (see Plate 3) Past groundwater flow directions since October 1998 ' have been to the northeast at gradients ranging from 0 004 to 0 010 ft /ft A petroleum-like odor was noted from purge water in monitonng well MW-1 although no measurable product or sheen was noted during this (12/00) sampling event No unusual odor was noted in monitoring wells MW-2 and MW-3 ' As depicted in Table 1, total petroleum hydrocarbons as referenced to gasoline (TPH-G) were detected in the groundwater samples obtained from monitoring wells MW-1, MW-2 and MW-3 at concentrations ranging from 99 to 4,100 µg/1 (parts per billion) BTEX constituents were ' detected pnmanly in MW-1 Benzene was detected at 1,800 µg/1 in MW-1 and at 130 µg/1 in MW-3 Toluene and ethylbenzene were detected only in MW-1 at 0 93 µg/1 and 74 µg/l, respectively Total xylenes were not detected at or above laboratory reporting limits in any of the ' three groundwater samples Since the previous sampling event conducted in July 2000, concentrations of petroleum constituents have generally increased However, Table 1 shows a trend toward higher concentration of petroleum constituents in the winter months (January 1999, December 1999 and ' December 2000) as compared to the following summer months for each calendar year From January 1999 to May and September 1999 the concentrations of most petroleum constituents i approximately decreased by '/2 or more A similar trend was also noted when comparing ' December 1999 to the July 2000 groundwater sampling event Furthermore there appears to be a trend when comparing similar seasons on an annual basis In the winter months, for example, benzene has decreased from January 1999 to December 1999 from 9,300 pg/1 to 7,800 gg/l That trend continued as the benzene concentration decreased again in December 2000 to 4,100 gg/1 Similar trends can be noted when comparing petroleum ' constituents in groundwater samples in the summer months from year to year Based on these seasonal trends it appears that petroleum concentrations are generally decreasing over time tFor a review of historical laboratory analyses conducted, refer to Table 1 Copies of the laboratory data sheets along with the laboratory reporting limits are presented in Attachment C ' Kleinfelder recommends that a copy of this report should be submitted to the San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) for their review 20-4439-01 E02 1201 1 R355 Page 4 of G Copyright 2001,Kleinfelder, Inc April 2 2001