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EDWARD C RALSTON <br /> UNOCAL CORPORATION <br /> Page 2 <br /> d <br /> 2. Although removal of crushed rock is proposed, the workplan submitted fails to accurately <br /> address the actual extent or size of over-excavations which have been documented at this <br /> site. This information is critical to site assessment, characterization and remediation due <br /> to the crushed rock backfill placed in these excavations which may interfere in assessment <br /> and remediation activities. In addition, crushed rock may also act as a direct conduit to <br /> groundwater which may potentially further impact this site. Please provide as-built <br /> drawings to scale indicating the size and locations of all known excavations including <br /> volumes of crushed rock placed in any excavations on site. All crushed rock must be <br /> removed prior to or concurrent with site assessment. <br /> I <br /> 3. In an attempt to be both cost effective and efficient, staff from PHS-EHD Site Mitigation <br /> Unit during our August 15, 1995 meeting requested that Unocal employ techniques which <br /> would accelerate the assessment of this site reducing construction delays by including <br /> push point technologies in conjunction with an on site mobile laboratory. This workplan <br /> fails to utilize the most cost effective approach to site assessment as indicated in current <br /> regulation. The workplan proposes 24 hour and 5 day turn around for laboratory analysis <br /> which are not cost effective alternatives to mobile laboratories. Telephone <br /> communications with Jim Munch on August 21, 1995 representing the State Clean Up <br /> Fund confirm PHS-EHD staff recommendations to be reasonable and cost effective with <br /> regard to on-site laboratory applications. PHS-EHD thereby requests an amendment <br /> to the workplan to include the employmer nt of an on-site mobile laboratory. <br /> 4. The workplan fails to include analytical detection limits for soil samples and water <br /> samples. Following the State of California Tri-Regional Board Staff Recommendations <br /> for Preliminary Evaluation and Investigation4Underground Tank Sites detection limits <br /> i shall be 0.005 mg/Kg (ppm) for BTEX and 1.0 mg/Kg for TPH gasoline or diesel (TPH <br /> 1 g and d) in soil matrices. Water analysis detection limits shall be 50 ppb TPHg and d, and <br /> 0.5 ppb BTEX. <br /> 5. In accordance with PHS-EHD Well Standards, destruction of soil borings is limited to a <br /> '. 5 percent by weight maximum for bentonite'in cement mixtures. <br /> I6. All composite sampling shall be no greater',than 2 samples per 50 yards of soil. All <br /> compositing shall be performed by a state certified lab. <br /> 7. A public notification process is required for all remediation and assessment projects which <br /> utilize excavation techniques. PHS-EHD will decrease the standard 30 day period to 21 <br /> days by canvassing the immediate area as well as posting the site. Site work may begin <br /> after September 18, 1995 if no public opposition is encountered. <br /> 8. Please provide a tentative time line/event schedule for crushed rock removal and site <br /> assessment activities. <br /> ii <br />