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Thanks for taking my call regarding the well demos at the Cordes Ranch project in Tracy CA. Here is the info
<br /> (attached)that I said I would send to you:
<br /> • 24550 Hansen Road 2.pdf—these are the well demo permits issued by SJCEHD (Johnny Yoakum).
<br /> • SICEHD Well Demo Permit Approval.pdf—email string that transmits issuance of well demo permits
<br /> from Johnny Yoakum.
<br /> • RWQCB Well Demo WP Approval.pdf—email approval of well demo work plan from Michael Smith,the
<br /> RWQCB case worker.
<br /> • 060223-WELL DATA.xIs—this is the historical well info.
<br /> o First worksheet has groundwater monitoring data. I highlighted wells that we considered
<br /> "clean" green and impacted wells red (MW-2, MW-SA,and MW-15).
<br /> o Second worksheet lists the well construction details (diameter, depth, screened interval).
<br /> You indicated in our conversation that you approve pressure grouting of 10 wells: MW-3, MW-6, MW-7, MW-8,
<br /> MW-9, MW-10, MW-11, MW-12, MW-14b,and MW-14c(total 30 wells). This would leave over-drilling of MW-
<br /> 1, MW-2, MW-4, MW-5a, MW-Sb, MW-Sc, MW-13b, MW-13c,and MW-15 (total 9 wells). I am not sure why
<br /> wells MW-1 and MW-4 did not make your pressure-grout list. MW-1 has been consistently non-detect. MW-4
<br /> has one low concentration,j-flagged detection (330 ug/L)that was a split sample that didn't meet lab QA/QC
<br /> limits. The corresponding split was non-detect.
<br /> I talked to my field guy and the following wells have already been pressure-grouted: MW-6, MW-8, MW-9, MW-
<br /> 10,and MW-11. So at this point, we have only pressure-grouted wells that are on your approved list above.
<br /> I respectfully request you reconsider our proposal for wells to be pressure-grouted based on the following
<br /> information paraphrased from our May 13, 2013 Site Conceptual Model.
<br /> g/L.R1TPHc detections in Zones B and C are infrequent and random, ranging from non-detect to
<br /> 2,800 Furthermore, the random detections of TPHc are relatively low concentration and are typically
<br /> flagged by the laboratory as "hydrocarbon result partly due to individual peak(s)in quantitation
<br /> range." Particularly random are the TPHc detections at well MW-14B, which is located over 310 feet
<br /> laterally(northwest)from the pipeline, and cross-gradient to the groundwater flow direction. Again,
<br /> TPHc concentrations at this depth (125 ft bgs)and lateral distance (320 feet)from the pipeline is not
<br /> consistent with the behavior of weathered crude oil particularly in the low Permeability soils encountered
<br /> at the Site.
<br /> Below is the Geotracker link to this Site Conceptual Model for your reference. Refer to Section 5.2.2.2 (page 22)
<br /> and Section 5.2.2.3(page 23). It is explained that we did some forensic analysis and determined that the deeper
<br /> (B and C zone) detections appeared to be naturally-occurring hydrocarbons, not crude from the former pipeline,
<br /> which the RWQCB has verbally agreed with in an April 23, 2014 meeting. Furthermore,wells MW-5b and MW-
<br /> 5c have an 8" diameter steel conductor casing which provides an added level to protection/seal.
<br /> http://geotracker.waterboards.ca.gov/esi/uploads/geo report/9141163647/SL0607708243.PDF
<br /> I am available to discuss this further Newel, but need to come to a resolution soon since the work is occurring
<br /> now. Tomorrow,we will limit pressure-grouting to the remaining wells on your approved list.
<br /> Thanks!
<br /> Dan Lescure,PE,LEED AP,QSP,QSD
<br /> Conestoga-Rovers&Associates(CRA)
<br /> One Concord Center
<br /> 2300 Clayton Road,Suite 920
<br /> Concord,CA 94520
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