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Page 2 of 3 <br /> ISCO plan for that site was to inject sodium persulfate. This compound was selected because it <br /> is the least reactive ISCO compound and because this site is an operating service station we <br /> wanted to be careful not to use an ISCO chemical that might elevate soil temperature or cause <br /> some other side-effect for the UST equipment. We performed a bench scale test for 2575 <br /> Country Club using sodium persulfate and found that the sodium levels after treatment increased <br /> dramatically. We have discussed this issue with Mike Infurna and he agrees this will be a <br /> problem for getting an injection permit from the Board, and at the very best we will likely be stuck <br /> for a long time trying to get the injection permit for ISCO at this site. We are now going to <br /> consider other remedial options at this site. <br /> Because 6131 Pacific is an operating service station we would likely use sodium persulfate at this <br /> site as well. So prior to performing a bench scale test at 6131 Pacific, we decided to collect <br /> some water samples to look at the background levels of sodium and some other elements. We <br /> collected water samples from wells VEW-2 (shallow groundwater) and from VEW-4 (deep <br /> groundwater). Both samples came back with Na, Fe, Mn, and AI at levels above the water quality <br /> goal. So we are now concerned that ISCO is not a viable option at this site and we are glad we <br /> figured this out before spending money on an ISCO bench scale test and pilot testing. <br /> We did the same analysis at a third site in Stockton (2494 E. Fremont St), where we were <br /> considering ISCO, and we found elevated Sodium there as well. <br /> So at this point we are thinking it would be a good idea for us to come up with another remedial <br /> option for this site. I'd like to get some input from you regarding this or discuss this with you in a <br /> phone call. But I wanted to give you this lab data first so you could take a look at it prior to me <br /> calling. <br /> We are still proceeding with the pending investigation at this site as the additional data is needed <br /> regardless of the remedial approach we take for this site. So at this point no delay in progress is <br /> expected. But we would like to start thinking about an alternative remedial approach as soon as <br /> possible to keep things moving along with this site. <br /> I'll give you a call next week to discuss this. <br /> Regards, <br /> Joe <br /> PS Just for reference here are the water quality goals we used for comparison <br /> Na 20 mg/I (20,000 pg/L) <br /> AI 1 mg/l (1,000 pg/L) <br /> Mn 0.050 mg/I (50 pg/L) <br /> Fe 0.3 mg/I (300 pg/L) <br /> Joe W. Neely, PG <br /> Conestoga-Rovers &Associates (CRA) <br /> 19449 Riverside Drive, Suite 230 <br /> Sonoma, CA 95476 <br /> Phone: 707-933-2361 <br /> Fax: 707-935-6649 <br /> Cell: 707-975-1372 <br /> 8/4/2010 <br />