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RfIlR1CX�-1fRNfR <br /> {s- Mr. Charles Leubner <br /> � } 20 January 1997 <br /> Page 7 <br /> Hence the gasoline tank excavation stockpile was deemed acceptable for use as backfill material. <br /> Clean pea gravel and Class AIB subbase was imported for this excavation to complete backfilling. <br /> CONCLUSIONS <br /> Due to the presence of petroleum hydrocarbons remaining in soil beneath Tank T7 (6,150 mg/Kg of <br /> TPH-D) and TI (691 mg/Kg of TPH-G), further investigations are required before these sites can <br /> be closed. A soil investigation of these areas should be conducted to evaluate the vertical extent of <br /> the hydrocarbons that remain in the soil. After the vertical extent of the contamination is <br /> determined, a risk based exposure assessment can be conducted to determine if further remediation <br /> of the tank sites are warranted. <br /> In 1990, four remote fill lines were removed near Tank T7. These lines were located near the <br /> trench excavated for removing the piping for the current project. Figure 4 from Stockton Unified <br /> School District Oil & Fuel Tank Project conducted in 1990 shows the locations of soil samples <br /> collected during the removal of those fill lines. A copy of this Figure is included within this report.. <br /> Petroleum hydrocarbons were detected at depths of 4 to 5 feet below the ground surface in the <br /> trench samples ranging 17 to 5,200 mg/Kg as Total Extractable Hydrocarbons (see attached Table 1 <br /> copied from that project's report). It is recommended that any investigation of Tank T7 also include <br /> sampling of the areas where hydrocarbons remain beneath the remote fill lines removed in 1990. <br /> We recommend that this report be submitted to the County for their concurrence with our findings. <br /> If you have any questions,please call. <br /> Sincerely yours, <br /> EOL <br /> HEL C &LERNER INC. L�� 1 f <br /> # 397)8 <br /> ; <br /> _ Noel M.Lerner IPA <br /> CPA � <br /> Project Manager '�lFQF O <br /> d` <br /> ,ALv <br /> enclosures: Figure 1,2, 3, and 4 (current report) <br /> Figure 4 from Oil&Fuel Storage Tank Project(1991 Report) <br /> Tables 1 and 2 (current report) <br /> Table 1 from Oil&Fuel Storage Tank Project(1991 Report) <br /> - Attachment A-Disposal Manifests <br /> - Attachment B -Laboratory Analysis Reports <br /> J <br /> cc: Ms. Letitcia Briggs- San Joaquin County Environmental Health Division <br /> 'I Z:1P1008IM1 BMOVAL.DOC <br /> J <br />