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26 July 1999
<br /> AGE-NC
<br /> No Project� 96-023 5 I
<br /> Page 3 of 5
<br /> 22 76 feet below the tops of the well casings Ground water elevations at the site ranged from -9 33
<br /> feet in MW-4 to -15 79 feet mean sea level (MSL) in MW-6B Ground water elevation decreased
<br /> 5 42 feet in MW-6B, ground water elevation increased an average of 0 51 feet in the remaining ,
<br /> - wells -
<br /> To infer ground water flow direction, the ground water elevation data was divided into two sets
<br /> based on the well screen intervals Ground water was between 14 2 and 23 5 feet above the screened
<br /> ' intervals in monitoring wells MWA, MW-2, MW-3, MW-613 and MW-813, comprising the lower
<br /> data set Ground water was within the screened intervals for monitoring wells MW-4, MW-5, MW-
<br /> 6A, MW-7 and MW-8A Figure 3 illustrates the ground water elevations based on the two data sets
<br /> Ground 'water flow direction was calculated toward MW-6B using data from wells screened within
<br /> the lower interval Ground water elevations, based upon data from wells screened across the currant
<br /> Iground water surface, indicate a flow toward MW-5 Historic ground water flow directions and _
<br /> gradient, based on wells MW-1, MW-2 and MW-3 are illustrated on Figure 5
<br /> 3 2 ANALYTICAL RESULTS OF WATER SAMPLES
<br /> TPH-g was detected in MW-1, MW-2 and MW-3 at concentrations of 3,900 parts per billion (ppb,
<br /> reported as micrograms per liter), 21,000 ppb and 160 ppb, respectively Benzene was detected in
<br />' the same wells at concentrations of 1,100 ppb, 2,500 ppb and 17 ppb, respectively Toluene,
<br /> ethylbenzene, and xylenes were detected in the same wells at concentrations ranging from 8 4 ppb
<br /> to 3,700 ppb TPH-d was detected in MW-1, MW-2 and MW-3 at concentrations of 650 ppb, 3,300
<br /> ppb and 55 ppb, respectively Petroleum hydrocarbons were not detected in the samples collected
<br /> from the remaining wells Analytical results of all water samples collected at the site are summarized
<br /> on Table 2 The laboratory report (MAI Sample Nos 12362-12371), chain-of-custody forms and the
<br />' laboratory QA/QC report are included in Appendix B
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<br />' 33 SENSITIVE RECEPTOR SURVEY
<br /> One municipal well was identified within 2,000 feet of the subject property Cal Water Well No 72- T
<br />' 01 is located at Stockton Street and Navy Drive, approximately 1,100 feet southwest of the site
<br /> (section 15, tract G) The nearest down-gradient wells are Cal Water Well No 73-01, located
<br />' approximately 3,000 feet north of the site (section 10, tract J) and Well No 37-01, located 2,900 feet
<br /> northeast of the site (section 1,1, tract P) A Cal Water water tower is located approximately 2,800
<br /> feet northeast of the site (section 14,tract C) The DWR database indicated a well in section 10 tract
<br /> R, between 1,200 and 2,500 feet north of the site The well likely refers to the Cal Water well No
<br /> 73-01, located in tract J The nearest surface water feature is Morman Slough, located approximately
<br /> 3,000 feet north to northeast of the site Well locations are illustrated in Figure 4
<br /> Advanced GeoEmironmenial,Inc
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